Commit | Line | Data |
---|---|---|
1cec2cac MCC |
1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | ========= | |
4 | IP Sysctl | |
5 | ========= | |
6 | ||
7 | /proc/sys/net/ipv4/* Variables | |
8 | ============================== | |
1da177e4 LT |
9 | |
10 | ip_forward - BOOLEAN | |
1cec2cac MCC |
11 | - 0 - disabled (default) |
12 | - not 0 - enabled | |
1da177e4 LT |
13 | |
14 | Forward Packets between interfaces. | |
15 | ||
16 | This variable is special, its change resets all configuration | |
17 | parameters to their default state (RFC1122 for hosts, RFC1812 | |
18 | for routers) | |
19 | ||
20 | ip_default_ttl - INTEGER | |
cc6f02dd ED |
21 | Default value of TTL field (Time To Live) for outgoing (but not |
22 | forwarded) IP packets. Should be between 1 and 255 inclusive. | |
23 | Default: 64 (as recommended by RFC1700) | |
1da177e4 | 24 | |
cd174e67 HFS |
25 | ip_no_pmtu_disc - INTEGER |
26 | Disable Path MTU Discovery. If enabled in mode 1 and a | |
188b04d5 | 27 | fragmentation-required ICMP is received, the PMTU to this |
be1c5b53 | 28 | destination will be set to the smallest of the old MTU to |
29 | this destination and min_pmtu (see below). You will need | |
188b04d5 HFS |
30 | to raise min_pmtu to the smallest interface MTU on your system |
31 | manually if you want to avoid locally generated fragments. | |
cd174e67 HFS |
32 | |
33 | In mode 2 incoming Path MTU Discovery messages will be | |
34 | discarded. Outgoing frames are handled the same as in mode 1, | |
35 | implicitly setting IP_PMTUDISC_DONT on every created socket. | |
36 | ||
bb38ccce | 37 | Mode 3 is a hardened pmtu discover mode. The kernel will only |
8ed1dc44 HFS |
38 | accept fragmentation-needed errors if the underlying protocol |
39 | can verify them besides a plain socket lookup. Current | |
40 | protocols for which pmtu events will be honored are TCP, SCTP | |
41 | and DCCP as they verify e.g. the sequence number or the | |
42 | association. This mode should not be enabled globally but is | |
43 | only intended to secure e.g. name servers in namespaces where | |
44 | TCP path mtu must still work but path MTU information of other | |
45 | protocols should be discarded. If enabled globally this mode | |
46 | could break other protocols. | |
47 | ||
48 | Possible values: 0-3 | |
1cec2cac | 49 | |
188b04d5 | 50 | Default: FALSE |
1da177e4 LT |
51 | |
52 | min_pmtu - INTEGER | |
be1c5b53 | 53 | default 552 - minimum Path MTU. Unless this is changed mannually, |
54 | each cached pmtu will never be lower than this setting. | |
1da177e4 | 55 | |
f87c10a8 HFS |
56 | ip_forward_use_pmtu - BOOLEAN |
57 | By default we don't trust protocol path MTUs while forwarding | |
58 | because they could be easily forged and can lead to unwanted | |
59 | fragmentation by the router. | |
60 | You only need to enable this if you have user-space software | |
61 | which tries to discover path mtus by itself and depends on the | |
62 | kernel honoring this information. This is normally not the | |
63 | case. | |
1cec2cac | 64 | |
f87c10a8 | 65 | Default: 0 (disabled) |
1cec2cac | 66 | |
f87c10a8 | 67 | Possible values: |
1cec2cac MCC |
68 | |
69 | - 0 - disabled | |
70 | - 1 - enabled | |
f87c10a8 | 71 | |
219b5f29 LV |
72 | fwmark_reflect - BOOLEAN |
73 | Controls the fwmark of kernel-generated IPv4 reply packets that are not | |
74 | associated with a socket for example, TCP RSTs or ICMP echo replies). | |
75 | If unset, these packets have a fwmark of zero. If set, they have the | |
76 | fwmark of the packet they are replying to. | |
1cec2cac | 77 | |
219b5f29 LV |
78 | Default: 0 |
79 | ||
a6db4494 DA |
80 | fib_multipath_use_neigh - BOOLEAN |
81 | Use status of existing neighbor entry when determining nexthop for | |
82 | multipath routes. If disabled, neighbor information is not used and | |
83 | packets could be directed to a failed nexthop. Only valid for kernels | |
84 | built with CONFIG_IP_ROUTE_MULTIPATH enabled. | |
1cec2cac | 85 | |
a6db4494 | 86 | Default: 0 (disabled) |
1cec2cac | 87 | |
a6db4494 | 88 | Possible values: |
1cec2cac MCC |
89 | |
90 | - 0 - disabled | |
91 | - 1 - enabled | |
a6db4494 | 92 | |
bf4e0a3d NA |
93 | fib_multipath_hash_policy - INTEGER |
94 | Controls which hash policy to use for multipath routes. Only valid | |
95 | for kernels built with CONFIG_IP_ROUTE_MULTIPATH enabled. | |
1cec2cac | 96 | |
bf4e0a3d | 97 | Default: 0 (Layer 3) |
1cec2cac | 98 | |
bf4e0a3d | 99 | Possible values: |
1cec2cac MCC |
100 | |
101 | - 0 - Layer 3 | |
102 | - 1 - Layer 4 | |
103 | - 2 - Layer 3 or inner Layer 3 if present | |
4253b498 IS |
104 | - 3 - Custom multipath hash. Fields used for multipath hash calculation |
105 | are determined by fib_multipath_hash_fields sysctl | |
bf4e0a3d | 106 | |
ce5c9c20 IS |
107 | fib_multipath_hash_fields - UNSIGNED INTEGER |
108 | When fib_multipath_hash_policy is set to 3 (custom multipath hash), the | |
109 | fields used for multipath hash calculation are determined by this | |
110 | sysctl. | |
111 | ||
112 | This value is a bitmask which enables various fields for multipath hash | |
113 | calculation. | |
114 | ||
115 | Possible fields are: | |
116 | ||
117 | ====== ============================ | |
118 | 0x0001 Source IP address | |
119 | 0x0002 Destination IP address | |
120 | 0x0004 IP protocol | |
121 | 0x0008 Unused (Flow Label) | |
122 | 0x0010 Source port | |
123 | 0x0020 Destination port | |
124 | 0x0040 Inner source IP address | |
125 | 0x0080 Inner destination IP address | |
126 | 0x0100 Inner IP protocol | |
127 | 0x0200 Inner Flow Label | |
128 | 0x0400 Inner source port | |
129 | 0x0800 Inner destination port | |
130 | ====== ============================ | |
131 | ||
132 | Default: 0x0007 (source IP, destination IP and IP protocol) | |
133 | ||
9ab948a9 DA |
134 | fib_sync_mem - UNSIGNED INTEGER |
135 | Amount of dirty memory from fib entries that can be backlogged before | |
136 | synchronize_rcu is forced. | |
1cec2cac MCC |
137 | |
138 | Default: 512kB Minimum: 64kB Maximum: 64MB | |
9ab948a9 | 139 | |
432e05d3 PM |
140 | ip_forward_update_priority - INTEGER |
141 | Whether to update SKB priority from "TOS" field in IPv4 header after it | |
142 | is forwarded. The new SKB priority is mapped from TOS field value | |
143 | according to an rt_tos2priority table (see e.g. man tc-prio). | |
1cec2cac | 144 | |
432e05d3 | 145 | Default: 1 (Update priority.) |
1cec2cac | 146 | |
432e05d3 | 147 | Possible values: |
1cec2cac MCC |
148 | |
149 | - 0 - Do not update priority. | |
150 | - 1 - Update priority. | |
432e05d3 | 151 | |
cbaf087a BG |
152 | route/max_size - INTEGER |
153 | Maximum number of routes allowed in the kernel. Increase | |
154 | this when using large numbers of interfaces and/or routes. | |
1cec2cac | 155 | |
25050c63 AS |
156 | From linux kernel 3.6 onwards, this is deprecated for ipv4 |
157 | as route cache is no longer used. | |
cbaf087a | 158 | |
2724680b YH |
159 | neigh/default/gc_thresh1 - INTEGER |
160 | Minimum number of entries to keep. Garbage collector will not | |
161 | purge entries if there are fewer than this number. | |
1cec2cac | 162 | |
b66c66dc | 163 | Default: 128 |
2724680b | 164 | |
a3d12146 | 165 | neigh/default/gc_thresh2 - INTEGER |
166 | Threshold when garbage collector becomes more aggressive about | |
167 | purging entries. Entries older than 5 seconds will be cleared | |
168 | when over this number. | |
1cec2cac | 169 | |
a3d12146 | 170 | Default: 512 |
171 | ||
cbaf087a | 172 | neigh/default/gc_thresh3 - INTEGER |
58956317 DA |
173 | Maximum number of non-PERMANENT neighbor entries allowed. Increase |
174 | this when using large numbers of interfaces and when communicating | |
cbaf087a | 175 | with large numbers of directly-connected peers. |
1cec2cac | 176 | |
cc868028 | 177 | Default: 1024 |
cbaf087a | 178 | |
8b5c171b ED |
179 | neigh/default/unres_qlen_bytes - INTEGER |
180 | The maximum number of bytes which may be used by packets | |
181 | queued for each unresolved address by other network layers. | |
182 | (added in linux 3.3) | |
1cec2cac | 183 | |
3b09adcb | 184 | Setting negative value is meaningless and will return error. |
1cec2cac | 185 | |
eaa72dc4 | 186 | Default: SK_WMEM_MAX, (same as net.core.wmem_default). |
1cec2cac | 187 | |
eaa72dc4 ED |
188 | Exact value depends on architecture and kernel options, |
189 | but should be enough to allow queuing 256 packets | |
190 | of medium size. | |
8b5c171b ED |
191 | |
192 | neigh/default/unres_qlen - INTEGER | |
193 | The maximum number of packets which may be queued for each | |
194 | unresolved address by other network layers. | |
1cec2cac | 195 | |
8b5c171b | 196 | (deprecated in linux 3.3) : use unres_qlen_bytes instead. |
1cec2cac | 197 | |
cc868028 | 198 | Prior to linux 3.3, the default value is 3 which may cause |
5d248c49 | 199 | unexpected packet loss. The current default value is calculated |
cc868028 SW |
200 | according to default value of unres_qlen_bytes and true size of |
201 | packet. | |
1cec2cac | 202 | |
eaa72dc4 | 203 | Default: 101 |
8b5c171b | 204 | |
1da177e4 LT |
205 | mtu_expires - INTEGER |
206 | Time, in seconds, that cached PMTU information is kept. | |
207 | ||
208 | min_adv_mss - INTEGER | |
209 | The advertised MSS depends on the first hop route MTU, but will | |
210 | never be lower than this setting. | |
211 | ||
680aea08 AC |
212 | fib_notify_on_flag_change - INTEGER |
213 | Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/ | |
648106c3 | 214 | RTM_F_TRAP/RTM_F_OFFLOAD_FAILED flags are changed. |
680aea08 AC |
215 | |
216 | After installing a route to the kernel, user space receives an | |
217 | acknowledgment, which means the route was installed in the kernel, | |
218 | but not necessarily in hardware. | |
219 | It is also possible for a route already installed in hardware to change | |
220 | its action and therefore its flags. For example, a host route that is | |
221 | trapping packets can be "promoted" to perform decapsulation following | |
222 | the installation of an IPinIP/VXLAN tunnel. | |
223 | The notifications will indicate to user-space the state of the route. | |
224 | ||
225 | Default: 0 (Do not emit notifications.) | |
226 | ||
227 | Possible values: | |
228 | ||
229 | - 0 - Do not emit notifications. | |
230 | - 1 - Emit notifications. | |
648106c3 | 231 | - 2 - Emit notifications only for RTM_F_OFFLOAD_FAILED flag change. |
680aea08 | 232 | |
1da177e4 LT |
233 | IP Fragmentation: |
234 | ||
3e67f106 | 235 | ipfrag_high_thresh - LONG INTEGER |
648700f7 | 236 | Maximum memory used to reassemble IP fragments. |
e18f5feb | 237 | |
3e67f106 | 238 | ipfrag_low_thresh - LONG INTEGER |
648700f7 | 239 | (Obsolete since linux-4.17) |
b13d3cbf FW |
240 | Maximum memory used to reassemble IP fragments before the kernel |
241 | begins to remove incomplete fragment queues to free up resources. | |
242 | The kernel still accepts new fragments for defragmentation. | |
1da177e4 LT |
243 | |
244 | ipfrag_time - INTEGER | |
e18f5feb | 245 | Time in seconds to keep an IP fragment in memory. |
1da177e4 | 246 | |
89cee8b1 | 247 | ipfrag_max_dist - INTEGER |
e18f5feb JDB |
248 | ipfrag_max_dist is a non-negative integer value which defines the |
249 | maximum "disorder" which is allowed among fragments which share a | |
250 | common IP source address. Note that reordering of packets is | |
251 | not unusual, but if a large number of fragments arrive from a source | |
252 | IP address while a particular fragment queue remains incomplete, it | |
253 | probably indicates that one or more fragments belonging to that queue | |
254 | have been lost. When ipfrag_max_dist is positive, an additional check | |
255 | is done on fragments before they are added to a reassembly queue - if | |
256 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
257 | address between additions to any IP fragment queue using that source | |
258 | address, it's presumed that one or more fragments in the queue are | |
259 | lost. The existing fragment queue will be dropped, and a new one | |
89cee8b1 HX |
260 | started. An ipfrag_max_dist value of zero disables this check. |
261 | ||
262 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
263 | result in unnecessarily dropping fragment queues when normal | |
e18f5feb JDB |
264 | reordering of packets occurs, which could lead to poor application |
265 | performance. Using a very large value, e.g. 50000, increases the | |
266 | likelihood of incorrectly reassembling IP fragments that originate | |
89cee8b1 HX |
267 | from different IP datagrams, which could result in data corruption. |
268 | Default: 64 | |
269 | ||
c6a4254c ND |
270 | bc_forwarding - INTEGER |
271 | bc_forwarding enables the feature described in rfc1812#section-5.3.5.2 | |
272 | and rfc2644. It allows the router to forward directed broadcast. | |
273 | To enable this feature, the 'all' entry and the input interface entry | |
274 | should be set to 1. | |
275 | Default: 0 | |
276 | ||
1cec2cac MCC |
277 | INET peer storage |
278 | ================= | |
1da177e4 LT |
279 | |
280 | inet_peer_threshold - INTEGER | |
e18f5feb | 281 | The approximate size of the storage. Starting from this threshold |
1da177e4 LT |
282 | entries will be thrown aggressively. This threshold also determines |
283 | entries' time-to-live and time intervals between garbage collection | |
284 | passes. More entries, less time-to-live, less GC interval. | |
285 | ||
286 | inet_peer_minttl - INTEGER | |
287 | Minimum time-to-live of entries. Should be enough to cover fragment | |
288 | time-to-live on the reassembling side. This minimum time-to-live is | |
289 | guaranteed if the pool size is less than inet_peer_threshold. | |
77a538d5 | 290 | Measured in seconds. |
1da177e4 LT |
291 | |
292 | inet_peer_maxttl - INTEGER | |
293 | Maximum time-to-live of entries. Unused entries will expire after | |
294 | this period of time if there is no memory pressure on the pool (i.e. | |
295 | when the number of entries in the pool is very small). | |
77a538d5 | 296 | Measured in seconds. |
1da177e4 | 297 | |
1cec2cac MCC |
298 | TCP variables |
299 | ============= | |
1da177e4 | 300 | |
ef56e622 SH |
301 | somaxconn - INTEGER |
302 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
19f92a03 ED |
303 | Defaults to 4096. (Was 128 before linux-5.4) |
304 | See also tcp_max_syn_backlog for additional tuning for TCP sockets. | |
ef56e622 | 305 | |
ef56e622 SH |
306 | tcp_abort_on_overflow - BOOLEAN |
307 | If listening service is too slow to accept new connections, | |
308 | reset them. Default state is FALSE. It means that if overflow | |
309 | occurred due to a burst, connection will recover. Enable this | |
310 | option _only_ if you are really sure that listening daemon | |
311 | cannot be tuned to accept connections faster. Enabling this | |
312 | option can harm clients of your server. | |
1da177e4 | 313 | |
ef56e622 SH |
314 | tcp_adv_win_scale - INTEGER |
315 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
316 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
317 | if it is <= 0. | |
1cec2cac | 318 | |
0147fc05 | 319 | Possible values are [-31, 31], inclusive. |
1cec2cac | 320 | |
b49960a0 | 321 | Default: 1 |
1da177e4 | 322 | |
ef56e622 SH |
323 | tcp_allowed_congestion_control - STRING |
324 | Show/set the congestion control choices available to non-privileged | |
325 | processes. The list is a subset of those listed in | |
326 | tcp_available_congestion_control. | |
1cec2cac | 327 | |
ef56e622 | 328 | Default is "reno" and the default setting (tcp_congestion_control). |
1da177e4 | 329 | |
ef56e622 SH |
330 | tcp_app_win - INTEGER |
331 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
332 | buffer. Value 0 is special, it means that nothing is reserved. | |
1cec2cac | 333 | |
ef56e622 | 334 | Default: 31 |
1da177e4 | 335 | |
f54b3111 ED |
336 | tcp_autocorking - BOOLEAN |
337 | Enable TCP auto corking : | |
338 | When applications do consecutive small write()/sendmsg() system calls, | |
339 | we try to coalesce these small writes as much as possible, to lower | |
340 | total amount of sent packets. This is done if at least one prior | |
341 | packet for the flow is waiting in Qdisc queues or device transmit | |
342 | queue. Applications can still use TCP_CORK for optimal behavior | |
343 | when they know how/when to uncork their sockets. | |
1cec2cac | 344 | |
f54b3111 ED |
345 | Default : 1 |
346 | ||
ef56e622 SH |
347 | tcp_available_congestion_control - STRING |
348 | Shows the available congestion control choices that are registered. | |
349 | More congestion control algorithms may be available as modules, | |
350 | but not loaded. | |
1da177e4 | 351 | |
71599cd1 | 352 | tcp_base_mss - INTEGER |
4edc2f34 SH |
353 | The initial value of search_low to be used by the packetization layer |
354 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
355 | this is the initial MSS used by the connection. | |
71599cd1 | 356 | |
c04b79b6 JH |
357 | tcp_mtu_probe_floor - INTEGER |
358 | If MTU probing is enabled this caps the minimum MSS used for search_low | |
359 | for the connection. | |
360 | ||
361 | Default : 48 | |
362 | ||
5f3e2bf0 ED |
363 | tcp_min_snd_mss - INTEGER |
364 | TCP SYN and SYNACK messages usually advertise an ADVMSS option, | |
365 | as described in RFC 1122 and RFC 6691. | |
1cec2cac | 366 | |
5f3e2bf0 ED |
367 | If this ADVMSS option is smaller than tcp_min_snd_mss, |
368 | it is silently capped to tcp_min_snd_mss. | |
369 | ||
370 | Default : 48 (at least 8 bytes of payload per segment) | |
371 | ||
ef56e622 SH |
372 | tcp_congestion_control - STRING |
373 | Set the congestion control algorithm to be used for new | |
374 | connections. The algorithm "reno" is always available, but | |
375 | additional choices may be available based on kernel configuration. | |
376 | Default is set as part of kernel configuration. | |
d8a6e65f ED |
377 | For passive connections, the listener congestion control choice |
378 | is inherited. | |
1cec2cac | 379 | |
d8a6e65f | 380 | [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] |
1da177e4 | 381 | |
ef56e622 SH |
382 | tcp_dsack - BOOLEAN |
383 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 384 | |
eed530b6 | 385 | tcp_early_retrans - INTEGER |
bec41a11 YC |
386 | Tail loss probe (TLP) converts RTOs occurring due to tail |
387 | losses into fast recovery (draft-ietf-tcpm-rack). Note that | |
388 | TLP requires RACK to function properly (see tcp_recovery below) | |
1cec2cac | 389 | |
eed530b6 | 390 | Possible values: |
1cec2cac MCC |
391 | |
392 | - 0 disables TLP | |
393 | - 3 or 4 enables TLP | |
394 | ||
6ba8a3b1 | 395 | Default: 3 |
eed530b6 | 396 | |
34a6ef38 | 397 | tcp_ecn - INTEGER |
7e3a2dc5 RJ |
398 | Control use of Explicit Congestion Notification (ECN) by TCP. |
399 | ECN is used only when both ends of the TCP connection indicate | |
400 | support for it. This feature is useful in avoiding losses due | |
401 | to congestion by allowing supporting routers to signal | |
402 | congestion before having to drop packets. | |
1cec2cac | 403 | |
255cac91 | 404 | Possible values are: |
1cec2cac MCC |
405 | |
406 | = ===================================================== | |
407 | 0 Disable ECN. Neither initiate nor accept ECN. | |
408 | 1 Enable ECN when requested by incoming connections and | |
409 | also request ECN on outgoing connection attempts. | |
410 | 2 Enable ECN when requested by incoming connections | |
411 | but do not request ECN on outgoing connections. | |
412 | = ===================================================== | |
413 | ||
255cac91 | 414 | Default: 2 |
ef56e622 | 415 | |
49213555 DB |
416 | tcp_ecn_fallback - BOOLEAN |
417 | If the kernel detects that ECN connection misbehaves, enable fall | |
418 | back to non-ECN. Currently, this knob implements the fallback | |
419 | from RFC3168, section 6.1.1.1., but we reserve that in future, | |
420 | additional detection mechanisms could be implemented under this | |
421 | knob. The value is not used, if tcp_ecn or per route (or congestion | |
422 | control) ECN settings are disabled. | |
1cec2cac | 423 | |
49213555 DB |
424 | Default: 1 (fallback enabled) |
425 | ||
ef56e622 | 426 | tcp_fack - BOOLEAN |
713bafea | 427 | This is a legacy option, it has no effect anymore. |
1da177e4 LT |
428 | |
429 | tcp_fin_timeout - INTEGER | |
d825da2e RJ |
430 | The length of time an orphaned (no longer referenced by any |
431 | application) connection will remain in the FIN_WAIT_2 state | |
432 | before it is aborted at the local end. While a perfectly | |
433 | valid "receive only" state for an un-orphaned connection, an | |
434 | orphaned connection in FIN_WAIT_2 state could otherwise wait | |
435 | forever for the remote to close its end of the connection. | |
1cec2cac | 436 | |
d825da2e | 437 | Cf. tcp_max_orphans |
1cec2cac | 438 | |
d825da2e | 439 | Default: 60 seconds |
1da177e4 | 440 | |
89808060 | 441 | tcp_frto - INTEGER |
e33099f9 | 442 | Enables Forward RTO-Recovery (F-RTO) defined in RFC5682. |
cd99889c | 443 | F-RTO is an enhanced recovery algorithm for TCP retransmission |
e33099f9 YC |
444 | timeouts. It is particularly beneficial in networks where the |
445 | RTT fluctuates (e.g., wireless). F-RTO is sender-side only | |
446 | modification. It does not require any support from the peer. | |
447 | ||
448 | By default it's enabled with a non-zero value. 0 disables F-RTO. | |
1da177e4 | 449 | |
e2d00e62 LC |
450 | tcp_fwmark_accept - BOOLEAN |
451 | If set, incoming connections to listening sockets that do not have a | |
452 | socket mark will set the mark of the accepting socket to the fwmark of | |
453 | the incoming SYN packet. This will cause all packets on that connection | |
454 | (starting from the first SYNACK) to be sent with that fwmark. The | |
455 | listening socket's mark is unchanged. Listening sockets that already | |
456 | have a fwmark set via setsockopt(SOL_SOCKET, SO_MARK, ...) are | |
457 | unaffected. | |
458 | ||
459 | Default: 0 | |
460 | ||
032ee423 NC |
461 | tcp_invalid_ratelimit - INTEGER |
462 | Limit the maximal rate for sending duplicate acknowledgments | |
463 | in response to incoming TCP packets that are for an existing | |
464 | connection but that are invalid due to any of these reasons: | |
465 | ||
466 | (a) out-of-window sequence number, | |
467 | (b) out-of-window acknowledgment number, or | |
468 | (c) PAWS (Protection Against Wrapped Sequence numbers) check failure | |
469 | ||
470 | This can help mitigate simple "ack loop" DoS attacks, wherein | |
471 | a buggy or malicious middlebox or man-in-the-middle can | |
472 | rewrite TCP header fields in manner that causes each endpoint | |
473 | to think that the other is sending invalid TCP segments, thus | |
474 | causing each side to send an unterminating stream of duplicate | |
475 | acknowledgments for invalid segments. | |
476 | ||
477 | Using 0 disables rate-limiting of dupacks in response to | |
478 | invalid segments; otherwise this value specifies the minimal | |
479 | space between sending such dupacks, in milliseconds. | |
480 | ||
481 | Default: 500 (milliseconds). | |
482 | ||
ef56e622 SH |
483 | tcp_keepalive_time - INTEGER |
484 | How often TCP sends out keepalive messages when keepalive is enabled. | |
485 | Default: 2hours. | |
1da177e4 | 486 | |
ef56e622 SH |
487 | tcp_keepalive_probes - INTEGER |
488 | How many keepalive probes TCP sends out, until it decides that the | |
489 | connection is broken. Default value: 9. | |
490 | ||
491 | tcp_keepalive_intvl - INTEGER | |
492 | How frequently the probes are send out. Multiplied by | |
493 | tcp_keepalive_probes it is time to kill not responding connection, | |
494 | after probes started. Default value: 75sec i.e. connection | |
495 | will be aborted after ~11 minutes of retries. | |
496 | ||
6dd9a14e DA |
497 | tcp_l3mdev_accept - BOOLEAN |
498 | Enables child sockets to inherit the L3 master device index. | |
499 | Enabling this option allows a "global" listen socket to work | |
500 | across L3 master domains (e.g., VRFs) with connected sockets | |
501 | derived from the listen socket to be bound to the L3 domain in | |
502 | which the packets originated. Only valid when the kernel was | |
503 | compiled with CONFIG_NET_L3_MASTER_DEV. | |
1cec2cac MCC |
504 | |
505 | Default: 0 (disabled) | |
6dd9a14e | 506 | |
ef56e622 | 507 | tcp_low_latency - BOOLEAN |
b6690b14 | 508 | This is a legacy option, it has no effect anymore. |
1da177e4 LT |
509 | |
510 | tcp_max_orphans - INTEGER | |
511 | Maximal number of TCP sockets not attached to any user file handle, | |
512 | held by system. If this number is exceeded orphaned connections are | |
513 | reset immediately and warning is printed. This limit exists | |
514 | only to prevent simple DoS attacks, you _must_ not rely on this | |
515 | or lower the limit artificially, but rather increase it | |
516 | (probably, after increasing installed memory), | |
517 | if network conditions require more than default value, | |
518 | and tune network services to linger and kill such states | |
519 | more aggressively. Let me to remind again: each orphan eats | |
520 | up to ~64K of unswappable memory. | |
521 | ||
1da177e4 | 522 | tcp_max_syn_backlog - INTEGER |
623d0c2d ED |
523 | Maximal number of remembered connection requests (SYN_RECV), |
524 | which have not received an acknowledgment from connecting client. | |
1cec2cac | 525 | |
623d0c2d | 526 | This is a per-listener limit. |
1cec2cac | 527 | |
99b53bdd PP |
528 | The minimal value is 128 for low memory machines, and it will |
529 | increase in proportion to the memory of machine. | |
1cec2cac | 530 | |
99b53bdd | 531 | If server suffers from overload, try increasing this number. |
1cec2cac | 532 | |
623d0c2d ED |
533 | Remember to also check /proc/sys/net/core/somaxconn |
534 | A SYN_RECV request socket consumes about 304 bytes of memory. | |
1da177e4 | 535 | |
ef56e622 SH |
536 | tcp_max_tw_buckets - INTEGER |
537 | Maximal number of timewait sockets held by system simultaneously. | |
538 | If this number is exceeded time-wait socket is immediately destroyed | |
539 | and warning is printed. This limit exists only to prevent | |
540 | simple DoS attacks, you _must_ not lower the limit artificially, | |
541 | but rather increase it (probably, after increasing installed memory), | |
542 | if network conditions require more than default value. | |
1da177e4 | 543 | |
ef56e622 SH |
544 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
545 | min: below this number of pages TCP is not bothered about its | |
546 | memory appetite. | |
1da177e4 | 547 | |
ef56e622 SH |
548 | pressure: when amount of memory allocated by TCP exceeds this number |
549 | of pages, TCP moderates its memory consumption and enters memory | |
550 | pressure mode, which is exited when memory consumption falls | |
551 | under "min". | |
1da177e4 | 552 | |
ef56e622 | 553 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 554 | |
ef56e622 SH |
555 | Defaults are calculated at boot time from amount of available |
556 | memory. | |
1da177e4 | 557 | |
f6722583 YC |
558 | tcp_min_rtt_wlen - INTEGER |
559 | The window length of the windowed min filter to track the minimum RTT. | |
560 | A shorter window lets a flow more quickly pick up new (higher) | |
561 | minimum RTT when it is moved to a longer path (e.g., due to traffic | |
562 | engineering). A longer window makes the filter more resistant to RTT | |
563 | inflations such as transient congestion. The unit is seconds. | |
1cec2cac | 564 | |
19fad20d | 565 | Possible values: 0 - 86400 (1 day) |
1cec2cac | 566 | |
f6722583 YC |
567 | Default: 300 |
568 | ||
71599cd1 | 569 | tcp_moderate_rcvbuf - BOOLEAN |
4edc2f34 | 570 | If set, TCP performs receive buffer auto-tuning, attempting to |
71599cd1 JH |
571 | automatically size the buffer (no greater than tcp_rmem[2]) to |
572 | match the size required by the path for full throughput. Enabled by | |
573 | default. | |
574 | ||
575 | tcp_mtu_probing - INTEGER | |
576 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
577 | values: | |
1cec2cac MCC |
578 | |
579 | - 0 - Disabled | |
580 | - 1 - Disabled by default, enabled when an ICMP black hole detected | |
581 | - 2 - Always enabled, use initial MSS of tcp_base_mss. | |
71599cd1 | 582 | |
d4ce5808 | 583 | tcp_probe_interval - UNSIGNED INTEGER |
fab42760 FD |
584 | Controls how often to start TCP Packetization-Layer Path MTU |
585 | Discovery reprobe. The default is reprobing every 10 minutes as | |
586 | per RFC4821. | |
587 | ||
588 | tcp_probe_threshold - INTEGER | |
589 | Controls when TCP Packetization-Layer Path MTU Discovery probing | |
590 | will stop in respect to the width of search range in bytes. Default | |
591 | is 8 bytes. | |
592 | ||
71599cd1 JH |
593 | tcp_no_metrics_save - BOOLEAN |
594 | By default, TCP saves various connection metrics in the route cache | |
595 | when the connection closes, so that connections established in the | |
596 | near future can use these to set initial conditions. Usually, this | |
597 | increases overall performance, but may sometimes cause performance | |
0f035b8e | 598 | degradation. If set, TCP will not cache metrics on closing |
71599cd1 JH |
599 | connections. |
600 | ||
65e6d901 KYY |
601 | tcp_no_ssthresh_metrics_save - BOOLEAN |
602 | Controls whether TCP saves ssthresh metrics in the route cache. | |
1cec2cac | 603 | |
65e6d901 KYY |
604 | Default is 1, which disables ssthresh metrics. |
605 | ||
ef56e622 | 606 | tcp_orphan_retries - INTEGER |
5d789229 DL |
607 | This value influences the timeout of a locally closed TCP connection, |
608 | when RTO retransmissions remain unacknowledged. | |
609 | See tcp_retries2 for more details. | |
610 | ||
06b8fc5d | 611 | The default value is 8. |
1cec2cac | 612 | |
5d789229 | 613 | If your machine is a loaded WEB server, |
ef56e622 SH |
614 | you should think about lowering this value, such sockets |
615 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 | 616 | |
4f41b1c5 YC |
617 | tcp_recovery - INTEGER |
618 | This value is a bitmap to enable various experimental loss recovery | |
619 | features. | |
620 | ||
1cec2cac MCC |
621 | ========= ============================================================= |
622 | RACK: 0x1 enables the RACK loss detection for fast detection of lost | |
623 | retransmissions and tail drops. It also subsumes and disables | |
624 | RFC6675 recovery for SACK connections. | |
625 | ||
626 | RACK: 0x2 makes RACK's reordering window static (min_rtt/4). | |
627 | ||
628 | RACK: 0x4 disables RACK's DUPACK threshold heuristic | |
629 | ========= ============================================================= | |
4f41b1c5 YC |
630 | |
631 | Default: 0x1 | |
632 | ||
1da177e4 | 633 | tcp_reordering - INTEGER |
dca145ff ED |
634 | Initial reordering level of packets in a TCP stream. |
635 | TCP stack can then dynamically adjust flow reordering level | |
636 | between this initial value and tcp_max_reordering | |
1cec2cac | 637 | |
e18f5feb | 638 | Default: 3 |
1da177e4 | 639 | |
dca145ff ED |
640 | tcp_max_reordering - INTEGER |
641 | Maximal reordering level of packets in a TCP stream. | |
642 | 300 is a fairly conservative value, but you might increase it | |
643 | if paths are using per packet load balancing (like bonding rr mode) | |
1cec2cac | 644 | |
dca145ff ED |
645 | Default: 300 |
646 | ||
1da177e4 LT |
647 | tcp_retrans_collapse - BOOLEAN |
648 | Bug-to-bug compatibility with some broken printers. | |
649 | On retransmit try to send bigger packets to work around bugs in | |
650 | certain TCP stacks. | |
651 | ||
ef56e622 | 652 | tcp_retries1 - INTEGER |
5d789229 DL |
653 | This value influences the time, after which TCP decides, that |
654 | something is wrong due to unacknowledged RTO retransmissions, | |
655 | and reports this suspicion to the network layer. | |
656 | See tcp_retries2 for more details. | |
657 | ||
658 | RFC 1122 recommends at least 3 retransmissions, which is the | |
659 | default. | |
1da177e4 | 660 | |
ef56e622 | 661 | tcp_retries2 - INTEGER |
5d789229 DL |
662 | This value influences the timeout of an alive TCP connection, |
663 | when RTO retransmissions remain unacknowledged. | |
664 | Given a value of N, a hypothetical TCP connection following | |
665 | exponential backoff with an initial RTO of TCP_RTO_MIN would | |
666 | retransmit N times before killing the connection at the (N+1)th RTO. | |
667 | ||
668 | The default value of 15 yields a hypothetical timeout of 924.6 | |
669 | seconds and is a lower bound for the effective timeout. | |
670 | TCP will effectively time out at the first RTO which exceeds the | |
671 | hypothetical timeout. | |
672 | ||
673 | RFC 1122 recommends at least 100 seconds for the timeout, | |
674 | which corresponds to a value of at least 8. | |
1da177e4 | 675 | |
ef56e622 SH |
676 | tcp_rfc1337 - BOOLEAN |
677 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
678 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
679 | assassination. | |
1cec2cac | 680 | |
ef56e622 | 681 | Default: 0 |
1da177e4 LT |
682 | |
683 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
684 | min: Minimal size of receive buffer used by TCP sockets. | |
685 | It is guaranteed to each TCP socket, even under moderate memory | |
686 | pressure. | |
1cec2cac | 687 | |
a61a86f8 | 688 | Default: 4K |
1da177e4 | 689 | |
53025f5e | 690 | default: initial size of receive buffer used by TCP sockets. |
1da177e4 | 691 | This value overrides net.core.rmem_default used by other protocols. |
1d1be912 ED |
692 | Default: 131072 bytes. |
693 | This value results in initial window of 65535. | |
1da177e4 LT |
694 | |
695 | max: maximal size of receive buffer allowed for automatically | |
696 | selected receiver buffers for TCP socket. This value does not override | |
53025f5e BF |
697 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
698 | automatic tuning of that socket's receive buffer size, in which | |
699 | case this value is ignored. | |
1d1be912 | 700 | Default: between 131072 and 6MB, depending on RAM size. |
1da177e4 | 701 | |
ef56e622 SH |
702 | tcp_sack - BOOLEAN |
703 | Enable select acknowledgments (SACKS). | |
1da177e4 | 704 | |
6d82aa24 ED |
705 | tcp_comp_sack_delay_ns - LONG INTEGER |
706 | TCP tries to reduce number of SACK sent, using a timer | |
707 | based on 5% of SRTT, capped by this sysctl, in nano seconds. | |
708 | The default is 1ms, based on TSO autosizing period. | |
709 | ||
710 | Default : 1,000,000 ns (1 ms) | |
711 | ||
a70437cc ED |
712 | tcp_comp_sack_slack_ns - LONG INTEGER |
713 | This sysctl control the slack used when arming the | |
714 | timer used by SACK compression. This gives extra time | |
715 | for small RTT flows, and reduces system overhead by allowing | |
716 | opportunistic reduction of timer interrupts. | |
717 | ||
718 | Default : 100,000 ns (100 us) | |
719 | ||
9c21d2fc | 720 | tcp_comp_sack_nr - INTEGER |
2bcd9d84 | 721 | Max number of SACK that can be compressed. |
9c21d2fc ED |
722 | Using 0 disables SACK compression. |
723 | ||
2bcd9d84 | 724 | Default : 44 |
9c21d2fc | 725 | |
ef56e622 SH |
726 | tcp_slow_start_after_idle - BOOLEAN |
727 | If set, provide RFC2861 behavior and time out the congestion | |
728 | window after an idle period. An idle period is defined at | |
729 | the current RTO. If unset, the congestion window will not | |
730 | be timed out after an idle period. | |
1cec2cac | 731 | |
ef56e622 | 732 | Default: 1 |
1da177e4 | 733 | |
ef56e622 | 734 | tcp_stdurg - BOOLEAN |
4edc2f34 | 735 | Use the Host requirements interpretation of the TCP urgent pointer field. |
ef56e622 SH |
736 | Most hosts use the older BSD interpretation, so if you turn this on |
737 | Linux might not communicate correctly with them. | |
1cec2cac | 738 | |
ef56e622 | 739 | Default: FALSE |
1da177e4 | 740 | |
ef56e622 SH |
741 | tcp_synack_retries - INTEGER |
742 | Number of times SYNACKs for a passive TCP connection attempt will | |
743 | be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
744 | is 5, which corresponds to 31seconds till the last retransmission |
745 | with the current initial RTO of 1second. With this the final timeout | |
746 | for a passive TCP connection will happen after 63seconds. | |
1da177e4 | 747 | |
d8513df2 | 748 | tcp_syncookies - INTEGER |
a3c910d2 | 749 | Only valid when the kernel was compiled with CONFIG_SYN_COOKIES |
ef56e622 | 750 | Send out syncookies when the syn backlog queue of a socket |
4edc2f34 | 751 | overflows. This is to prevent against the common 'SYN flood attack' |
a3c910d2 | 752 | Default: 1 |
1da177e4 | 753 | |
ef56e622 SH |
754 | Note, that syncookies is fallback facility. |
755 | It MUST NOT be used to help highly loaded servers to stand | |
4edc2f34 | 756 | against legal connection rate. If you see SYN flood warnings |
ef56e622 SH |
757 | in your logs, but investigation shows that they occur |
758 | because of overload with legal connections, you should tune | |
759 | another parameters until this warning disappear. | |
760 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 761 | |
ef56e622 SH |
762 | syncookies seriously violate TCP protocol, do not allow |
763 | to use TCP extensions, can result in serious degradation | |
764 | of some services (f.e. SMTP relaying), visible not by you, | |
765 | but your clients and relays, contacting you. While you see | |
4edc2f34 | 766 | SYN flood warnings in logs not being really flooded, your server |
ef56e622 | 767 | is seriously misconfigured. |
1da177e4 | 768 | |
5ad37d5d HFS |
769 | If you want to test which effects syncookies have to your |
770 | network connections you can set this knob to 2 to enable | |
771 | unconditionally generation of syncookies. | |
772 | ||
f9ac779f KI |
773 | tcp_migrate_req - BOOLEAN |
774 | The incoming connection is tied to a specific listening socket when | |
775 | the initial SYN packet is received during the three-way handshake. | |
776 | When a listener is closed, in-flight request sockets during the | |
777 | handshake and established sockets in the accept queue are aborted. | |
778 | ||
779 | If the listener has SO_REUSEPORT enabled, other listeners on the | |
780 | same port should have been able to accept such connections. This | |
781 | option makes it possible to migrate such child sockets to another | |
782 | listener after close() or shutdown(). | |
783 | ||
784 | The BPF_SK_REUSEPORT_SELECT_OR_MIGRATE type of eBPF program should | |
785 | usually be used to define the policy to pick an alive listener. | |
786 | Otherwise, the kernel will randomly pick an alive listener only if | |
787 | this option is enabled. | |
788 | ||
789 | Note that migration between listeners with different settings may | |
790 | crash applications. Let's say migration happens from listener A to | |
791 | B, and only B has TCP_SAVE_SYN enabled. B cannot read SYN data from | |
792 | the requests migrated from A. To avoid such a situation, cancel | |
793 | migration by returning SK_DROP in the type of eBPF program, or | |
794 | disable this option. | |
795 | ||
796 | Default: 0 | |
797 | ||
cf60af03 | 798 | tcp_fastopen - INTEGER |
cebc5cba YC |
799 | Enable TCP Fast Open (RFC7413) to send and accept data in the opening |
800 | SYN packet. | |
10467163 | 801 | |
cebc5cba YC |
802 | The client support is enabled by flag 0x1 (on by default). The client |
803 | then must use sendmsg() or sendto() with the MSG_FASTOPEN flag, | |
804 | rather than connect() to send data in SYN. | |
cf60af03 | 805 | |
cebc5cba YC |
806 | The server support is enabled by flag 0x2 (off by default). Then |
807 | either enable for all listeners with another flag (0x400) or | |
808 | enable individual listeners via TCP_FASTOPEN socket option with | |
809 | the option value being the length of the syn-data backlog. | |
cf60af03 | 810 | |
cebc5cba | 811 | The values (bitmap) are |
1cec2cac MCC |
812 | |
813 | ===== ======== ====================================================== | |
814 | 0x1 (client) enables sending data in the opening SYN on the client. | |
815 | 0x2 (server) enables the server support, i.e., allowing data in | |
cebc5cba YC |
816 | a SYN packet to be accepted and passed to the |
817 | application before 3-way handshake finishes. | |
1cec2cac | 818 | 0x4 (client) send data in the opening SYN regardless of cookie |
cebc5cba | 819 | availability and without a cookie option. |
1cec2cac MCC |
820 | 0x200 (server) accept data-in-SYN w/o any cookie option present. |
821 | 0x400 (server) enable all listeners to support Fast Open by | |
cebc5cba | 822 | default without explicit TCP_FASTOPEN socket option. |
1cec2cac | 823 | ===== ======== ====================================================== |
cebc5cba YC |
824 | |
825 | Default: 0x1 | |
10467163 | 826 | |
a7db3c76 | 827 | Note that additional client or server features are only |
cebc5cba | 828 | effective if the basic support (0x1 and 0x2) are enabled respectively. |
10467163 | 829 | |
cf1ef3f0 WW |
830 | tcp_fastopen_blackhole_timeout_sec - INTEGER |
831 | Initial time period in second to disable Fastopen on active TCP sockets | |
832 | when a TFO firewall blackhole issue happens. | |
833 | This time period will grow exponentially when more blackhole issues | |
834 | get detected right after Fastopen is re-enabled and will reset to | |
835 | initial value when the blackhole issue goes away. | |
7268586b | 836 | 0 to disable the blackhole detection. |
1cec2cac | 837 | |
213ad73d | 838 | By default, it is set to 0 (feature is disabled). |
cf1ef3f0 | 839 | |
2dc7e48d JB |
840 | tcp_fastopen_key - list of comma separated 32-digit hexadecimal INTEGERs |
841 | The list consists of a primary key and an optional backup key. The | |
842 | primary key is used for both creating and validating cookies, while the | |
843 | optional backup key is only used for validating cookies. The purpose of | |
844 | the backup key is to maximize TFO validation when keys are rotated. | |
845 | ||
846 | A randomly chosen primary key may be configured by the kernel if | |
847 | the tcp_fastopen sysctl is set to 0x400 (see above), or if the | |
848 | TCP_FASTOPEN setsockopt() optname is set and a key has not been | |
849 | previously configured via sysctl. If keys are configured via | |
850 | setsockopt() by using the TCP_FASTOPEN_KEY optname, then those | |
851 | per-socket keys will be used instead of any keys that are specified via | |
852 | sysctl. | |
853 | ||
854 | A key is specified as 4 8-digit hexadecimal integers which are separated | |
855 | by a '-' as: xxxxxxxx-xxxxxxxx-xxxxxxxx-xxxxxxxx. Leading zeros may be | |
856 | omitted. A primary and a backup key may be specified by separating them | |
857 | by a comma. If only one key is specified, it becomes the primary key and | |
858 | any previously configured backup keys are removed. | |
859 | ||
ef56e622 SH |
860 | tcp_syn_retries - INTEGER |
861 | Number of times initial SYNs for an active TCP connection attempt | |
bffae697 | 862 | will be retransmitted. Should not be higher than 127. Default value |
3b09adcb | 863 | is 6, which corresponds to 63seconds till the last retransmission |
6c9ff979 AB |
864 | with the current initial RTO of 1second. With this the final timeout |
865 | for an active TCP connection attempt will happen after 127seconds. | |
ef56e622 | 866 | |
25429d7b | 867 | tcp_timestamps - INTEGER |
1cec2cac MCC |
868 | Enable timestamps as defined in RFC1323. |
869 | ||
870 | - 0: Disabled. | |
871 | - 1: Enable timestamps as defined in RFC1323 and use random offset for | |
872 | each connection rather than only using the current time. | |
873 | - 2: Like 1, but without random offsets. | |
874 | ||
25429d7b | 875 | Default: 1 |
1da177e4 | 876 | |
95bd09eb ED |
877 | tcp_min_tso_segs - INTEGER |
878 | Minimal number of segments per TSO frame. | |
1cec2cac | 879 | |
95bd09eb ED |
880 | Since linux-3.12, TCP does an automatic sizing of TSO frames, |
881 | depending on flow rate, instead of filling 64Kbytes packets. | |
882 | For specific usages, it's possible to force TCP to build big | |
883 | TSO frames. Note that TCP stack might split too big TSO packets | |
884 | if available window is too small. | |
1cec2cac | 885 | |
95bd09eb ED |
886 | Default: 2 |
887 | ||
65466904 ED |
888 | tcp_tso_rtt_log - INTEGER |
889 | Adjustment of TSO packet sizes based on min_rtt | |
890 | ||
891 | Starting from linux-5.18, TCP autosizing can be tweaked | |
892 | for flows having small RTT. | |
893 | ||
894 | Old autosizing was splitting the pacing budget to send 1024 TSO | |
895 | per second. | |
896 | ||
897 | tso_packet_size = sk->sk_pacing_rate / 1024; | |
898 | ||
899 | With the new mechanism, we increase this TSO sizing using: | |
900 | ||
901 | distance = min_rtt_usec / (2^tcp_tso_rtt_log) | |
902 | tso_packet_size += gso_max_size >> distance; | |
903 | ||
904 | This means that flows between very close hosts can use bigger | |
905 | TSO packets, reducing their cpu costs. | |
906 | ||
907 | If you want to use the old autosizing, set this sysctl to 0. | |
908 | ||
909 | Default: 9 (2^9 = 512 usec) | |
910 | ||
43e122b0 ED |
911 | tcp_pacing_ss_ratio - INTEGER |
912 | sk->sk_pacing_rate is set by TCP stack using a ratio applied | |
913 | to current rate. (current_rate = cwnd * mss / srtt) | |
914 | If TCP is in slow start, tcp_pacing_ss_ratio is applied | |
915 | to let TCP probe for bigger speeds, assuming cwnd can be | |
916 | doubled every other RTT. | |
1cec2cac | 917 | |
43e122b0 ED |
918 | Default: 200 |
919 | ||
920 | tcp_pacing_ca_ratio - INTEGER | |
921 | sk->sk_pacing_rate is set by TCP stack using a ratio applied | |
922 | to current rate. (current_rate = cwnd * mss / srtt) | |
923 | If TCP is in congestion avoidance phase, tcp_pacing_ca_ratio | |
924 | is applied to conservatively probe for bigger throughput. | |
1cec2cac | 925 | |
43e122b0 ED |
926 | Default: 120 |
927 | ||
1da177e4 | 928 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
929 | This allows control over what percentage of the congestion window |
930 | can be consumed by a single TSO frame. | |
931 | The setting of this parameter is a choice between burstiness and | |
932 | building larger TSO frames. | |
1cec2cac | 933 | |
ef56e622 | 934 | Default: 3 |
1da177e4 | 935 | |
79e9fed4 MŻ |
936 | tcp_tw_reuse - INTEGER |
937 | Enable reuse of TIME-WAIT sockets for new connections when it is | |
938 | safe from protocol viewpoint. | |
1cec2cac MCC |
939 | |
940 | - 0 - disable | |
941 | - 1 - global enable | |
942 | - 2 - enable for loopback traffic only | |
943 | ||
ef56e622 SH |
944 | It should not be changed without advice/request of technical |
945 | experts. | |
1cec2cac | 946 | |
79e9fed4 | 947 | Default: 2 |
ce7bc3bf | 948 | |
ef56e622 SH |
949 | tcp_window_scaling - BOOLEAN |
950 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 951 | |
ef56e622 | 952 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
53025f5e | 953 | min: Amount of memory reserved for send buffers for TCP sockets. |
ef56e622 | 954 | Each TCP socket has rights to use it due to fact of its birth. |
1cec2cac | 955 | |
a61a86f8 | 956 | Default: 4K |
9d7bcfc6 | 957 | |
53025f5e BF |
958 | default: initial size of send buffer used by TCP sockets. This |
959 | value overrides net.core.wmem_default used by other protocols. | |
1cec2cac | 960 | |
53025f5e | 961 | It is usually lower than net.core.wmem_default. |
1cec2cac | 962 | |
ef56e622 SH |
963 | Default: 16K |
964 | ||
53025f5e BF |
965 | max: Maximal amount of memory allowed for automatically tuned |
966 | send buffers for TCP sockets. This value does not override | |
967 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
968 | automatic tuning of that socket's send buffer size, in which case | |
969 | this value is ignored. | |
1cec2cac | 970 | |
53025f5e | 971 | Default: between 64K and 4MB, depending on RAM size. |
1da177e4 | 972 | |
c9bee3b7 ED |
973 | tcp_notsent_lowat - UNSIGNED INTEGER |
974 | A TCP socket can control the amount of unsent bytes in its write queue, | |
975 | thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll() | |
976 | reports POLLOUT events if the amount of unsent bytes is below a per | |
977 | socket value, and if the write queue is not full. sendmsg() will | |
978 | also not add new buffers if the limit is hit. | |
979 | ||
980 | This global variable controls the amount of unsent data for | |
981 | sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change | |
982 | to the global variable has immediate effect. | |
983 | ||
984 | Default: UINT_MAX (0xFFFFFFFF) | |
985 | ||
15d99e02 RJ |
986 | tcp_workaround_signed_windows - BOOLEAN |
987 | If set, assume no receipt of a window scaling option means the | |
988 | remote TCP is broken and treats the window as a signed quantity. | |
989 | If unset, assume the remote TCP is not broken even if we do | |
990 | not receive a window scaling option from them. | |
1cec2cac | 991 | |
15d99e02 RJ |
992 | Default: 0 |
993 | ||
36e31b0a AP |
994 | tcp_thin_linear_timeouts - BOOLEAN |
995 | Enable dynamic triggering of linear timeouts for thin streams. | |
996 | If set, a check is performed upon retransmission by timeout to | |
997 | determine if the stream is thin (less than 4 packets in flight). | |
998 | As long as the stream is found to be thin, up to 6 linear | |
999 | timeouts may be performed before exponential backoff mode is | |
1000 | initiated. This improves retransmission latency for | |
1001 | non-aggressive thin streams, often found to be time-dependent. | |
1002 | For more information on thin streams, see | |
ff159f4f | 1003 | Documentation/networking/tcp-thin.rst |
1cec2cac | 1004 | |
36e31b0a AP |
1005 | Default: 0 |
1006 | ||
46d3ceab ED |
1007 | tcp_limit_output_bytes - INTEGER |
1008 | Controls TCP Small Queue limit per tcp socket. | |
1009 | TCP bulk sender tends to increase packets in flight until it | |
1010 | gets losses notifications. With SNDBUF autotuning, this can | |
9c4c3252 FL |
1011 | result in a large amount of packets queued on the local machine |
1012 | (e.g.: qdiscs, CPU backlog, or device) hurting latency of other | |
1013 | flows, for typical pfifo_fast qdiscs. tcp_limit_output_bytes | |
1014 | limits the number of bytes on qdisc or device to reduce artificial | |
1015 | RTT/cwnd and reduce bufferbloat. | |
1cec2cac | 1016 | |
c73e5807 | 1017 | Default: 1048576 (16 * 65536) |
46d3ceab | 1018 | |
282f23c6 ED |
1019 | tcp_challenge_ack_limit - INTEGER |
1020 | Limits number of Challenge ACK sent per second, as recommended | |
1021 | in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) | |
5309960e | 1022 | Default: 1000 |
282f23c6 | 1023 | |
1cec2cac MCC |
1024 | UDP variables |
1025 | ============= | |
95766fff | 1026 | |
63a6fff3 RS |
1027 | udp_l3mdev_accept - BOOLEAN |
1028 | Enabling this option allows a "global" bound socket to work | |
1029 | across L3 master domains (e.g., VRFs) with packets capable of | |
1030 | being received regardless of the L3 domain in which they | |
1031 | originated. Only valid when the kernel was compiled with | |
1032 | CONFIG_NET_L3_MASTER_DEV. | |
1cec2cac MCC |
1033 | |
1034 | Default: 0 (disabled) | |
63a6fff3 | 1035 | |
95766fff HA |
1036 | udp_mem - vector of 3 INTEGERs: min, pressure, max |
1037 | Number of pages allowed for queueing by all UDP sockets. | |
1038 | ||
69dfccbc | 1039 | min: Number of pages allowed for queueing by all UDP sockets. |
95766fff HA |
1040 | |
1041 | pressure: This value was introduced to follow format of tcp_mem. | |
1042 | ||
69dfccbc | 1043 | max: This value was introduced to follow format of tcp_mem. |
95766fff HA |
1044 | |
1045 | Default is calculated at boot time from amount of available memory. | |
1046 | ||
1047 | udp_rmem_min - INTEGER | |
1048 | Minimal size of receive buffer used by UDP sockets in moderation. | |
1049 | Each UDP socket is able to use the size for receiving data, even if | |
1050 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
1cec2cac | 1051 | |
320bd6de | 1052 | Default: 4K |
95766fff HA |
1053 | |
1054 | udp_wmem_min - INTEGER | |
c6b10de5 | 1055 | UDP does not have tx memory accounting and this tunable has no effect. |
95766fff | 1056 | |
1cec2cac MCC |
1057 | RAW variables |
1058 | ============= | |
6897445f MM |
1059 | |
1060 | raw_l3mdev_accept - BOOLEAN | |
1061 | Enabling this option allows a "global" bound socket to work | |
1062 | across L3 master domains (e.g., VRFs) with packets capable of | |
1063 | being received regardless of the L3 domain in which they | |
1064 | originated. Only valid when the kernel was compiled with | |
1065 | CONFIG_NET_L3_MASTER_DEV. | |
1cec2cac | 1066 | |
6897445f MM |
1067 | Default: 1 (enabled) |
1068 | ||
1cec2cac MCC |
1069 | CIPSOv4 Variables |
1070 | ================= | |
8802f616 PM |
1071 | |
1072 | cipso_cache_enable - BOOLEAN | |
1073 | If set, enable additions to and lookups from the CIPSO label mapping | |
1074 | cache. If unset, additions are ignored and lookups always result in a | |
1075 | miss. However, regardless of the setting the cache is still | |
1076 | invalidated when required when means you can safely toggle this on and | |
1077 | off and the cache will always be "safe". | |
1cec2cac | 1078 | |
8802f616 PM |
1079 | Default: 1 |
1080 | ||
1081 | cipso_cache_bucket_size - INTEGER | |
1082 | The CIPSO label cache consists of a fixed size hash table with each | |
1083 | hash bucket containing a number of cache entries. This variable limits | |
dd44f04b | 1084 | the number of entries in each hash bucket; the larger the value is, the |
8802f616 PM |
1085 | more CIPSO label mappings that can be cached. When the number of |
1086 | entries in a given hash bucket reaches this limit adding new entries | |
1087 | causes the oldest entry in the bucket to be removed to make room. | |
1cec2cac | 1088 | |
8802f616 PM |
1089 | Default: 10 |
1090 | ||
1091 | cipso_rbm_optfmt - BOOLEAN | |
1092 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
1093 | the CIPSO draft specification (see Documentation/netlabel for details). | |
1094 | This means that when set the CIPSO tag will be padded with empty | |
1095 | categories in order to make the packet data 32-bit aligned. | |
1cec2cac | 1096 | |
8802f616 PM |
1097 | Default: 0 |
1098 | ||
1099 | cipso_rbm_structvalid - BOOLEAN | |
1100 | If set, do a very strict check of the CIPSO option when | |
1101 | ip_options_compile() is called. If unset, relax the checks done during | |
1102 | ip_options_compile(). Either way is "safe" as errors are caught else | |
1103 | where in the CIPSO processing code but setting this to 0 (False) should | |
1104 | result in less work (i.e. it should be faster) but could cause problems | |
1105 | with other implementations that require strict checking. | |
1cec2cac | 1106 | |
8802f616 PM |
1107 | Default: 0 |
1108 | ||
1cec2cac MCC |
1109 | IP Variables |
1110 | ============ | |
1da177e4 LT |
1111 | |
1112 | ip_local_port_range - 2 INTEGERS | |
1113 | Defines the local port range that is used by TCP and UDP to | |
e18f5feb | 1114 | choose the local port. The first number is the first, the |
07f4c900 | 1115 | second the last local port number. |
ac71676c MŻ |
1116 | If possible, it is better these numbers have different parity |
1117 | (one even and one odd value). | |
1118 | Must be greater than or equal to ip_unprivileged_port_start. | |
07f4c900 | 1119 | The default values are 32768 and 60999 respectively. |
1da177e4 | 1120 | |
e3826f1e AW |
1121 | ip_local_reserved_ports - list of comma separated ranges |
1122 | Specify the ports which are reserved for known third-party | |
1123 | applications. These ports will not be used by automatic port | |
1124 | assignments (e.g. when calling connect() or bind() with port | |
1125 | number 0). Explicit port allocation behavior is unchanged. | |
1126 | ||
1127 | The format used for both input and output is a comma separated | |
1128 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and | |
1129 | 10). Writing to the file will clear all previously reserved | |
1130 | ports and update the current list with the one given in the | |
1131 | input. | |
1132 | ||
1133 | Note that ip_local_port_range and ip_local_reserved_ports | |
1134 | settings are independent and both are considered by the kernel | |
1135 | when determining which ports are available for automatic port | |
1136 | assignments. | |
1137 | ||
1138 | You can reserve ports which are not in the current | |
1cec2cac | 1139 | ip_local_port_range, e.g.:: |
e3826f1e | 1140 | |
1cec2cac MCC |
1141 | $ cat /proc/sys/net/ipv4/ip_local_port_range |
1142 | 32000 60999 | |
1143 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports | |
1144 | 8080,9148 | |
e3826f1e AW |
1145 | |
1146 | although this is redundant. However such a setting is useful | |
1147 | if later the port range is changed to a value that will | |
a7a80b17 OH |
1148 | include the reserved ports. Also keep in mind, that overlapping |
1149 | of these ranges may affect probability of selecting ephemeral | |
1150 | ports which are right after block of reserved ports. | |
e3826f1e AW |
1151 | |
1152 | Default: Empty | |
1153 | ||
4548b683 KJ |
1154 | ip_unprivileged_port_start - INTEGER |
1155 | This is a per-namespace sysctl. It defines the first | |
1156 | unprivileged port in the network namespace. Privileged ports | |
1157 | require root or CAP_NET_BIND_SERVICE in order to bind to them. | |
ac71676c MŻ |
1158 | To disable all privileged ports, set this to 0. They must not |
1159 | overlap with the ip_local_port_range. | |
4548b683 KJ |
1160 | |
1161 | Default: 1024 | |
1162 | ||
1da177e4 LT |
1163 | ip_nonlocal_bind - BOOLEAN |
1164 | If set, allows processes to bind() to non-local IP addresses, | |
1165 | which can be quite useful - but may break some applications. | |
1cec2cac | 1166 | |
1da177e4 LT |
1167 | Default: 0 |
1168 | ||
4b01a967 KI |
1169 | ip_autobind_reuse - BOOLEAN |
1170 | By default, bind() does not select the ports automatically even if | |
1171 | the new socket and all sockets bound to the port have SO_REUSEADDR. | |
1172 | ip_autobind_reuse allows bind() to reuse the port and this is useful | |
1173 | when you use bind()+connect(), but may break some applications. | |
1174 | The preferred solution is to use IP_BIND_ADDRESS_NO_PORT and this | |
1175 | option should only be set by experts. | |
1176 | Default: 0 | |
1177 | ||
e49e4aff | 1178 | ip_dynaddr - INTEGER |
1da177e4 LT |
1179 | If set non-zero, enables support for dynamic addresses. |
1180 | If set to a non-zero value larger than 1, a kernel log | |
1181 | message will be printed when dynamic address rewriting | |
1182 | occurs. | |
1cec2cac | 1183 | |
1da177e4 LT |
1184 | Default: 0 |
1185 | ||
e3d73bce CW |
1186 | ip_early_demux - BOOLEAN |
1187 | Optimize input packet processing down to one demux for | |
1188 | certain kinds of local sockets. Currently we only do this | |
dddb64bc | 1189 | for established TCP and connected UDP sockets. |
e3d73bce CW |
1190 | |
1191 | It may add an additional cost for pure routing workloads that | |
1192 | reduces overall throughput, in such case you should disable it. | |
1cec2cac | 1193 | |
e3d73bce CW |
1194 | Default: 1 |
1195 | ||
5cc4adbc SH |
1196 | ping_group_range - 2 INTEGERS |
1197 | Restrict ICMP_PROTO datagram sockets to users in the group range. | |
1198 | The default is "1 0", meaning, that nobody (not even root) may | |
1199 | create ping sockets. Setting it to "100 100" would grant permissions | |
1200 | to the single group. "0 4294967295" would enable it for the world, "100 | |
1201 | 4294967295" would enable it for the users, but not daemons. | |
1202 | ||
dddb64bc | 1203 | tcp_early_demux - BOOLEAN |
1204 | Enable early demux for established TCP sockets. | |
1cec2cac | 1205 | |
dddb64bc | 1206 | Default: 1 |
1207 | ||
1208 | udp_early_demux - BOOLEAN | |
1209 | Enable early demux for connected UDP sockets. Disable this if | |
1210 | your system could experience more unconnected load. | |
1cec2cac | 1211 | |
dddb64bc | 1212 | Default: 1 |
1213 | ||
1da177e4 | 1214 | icmp_echo_ignore_all - BOOLEAN |
7ce31246 DM |
1215 | If set non-zero, then the kernel will ignore all ICMP ECHO |
1216 | requests sent to it. | |
1cec2cac | 1217 | |
7ce31246 DM |
1218 | Default: 0 |
1219 | ||
f1b8fa9f AR |
1220 | icmp_echo_enable_probe - BOOLEAN |
1221 | If set to one, then the kernel will respond to RFC 8335 PROBE | |
1222 | requests sent to it. | |
1223 | ||
1224 | Default: 0 | |
1225 | ||
1da177e4 | 1226 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
1227 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
1228 | TIMESTAMP requests sent to it via broadcast/multicast. | |
1cec2cac | 1229 | |
7ce31246 | 1230 | Default: 1 |
1da177e4 LT |
1231 | |
1232 | icmp_ratelimit - INTEGER | |
1233 | Limit the maximal rates for sending ICMP packets whose type matches | |
1234 | icmp_ratemask (see below) to specific targets. | |
6dbf4bca SH |
1235 | 0 to disable any limiting, |
1236 | otherwise the minimal space between responses in milliseconds. | |
4cdf507d ED |
1237 | Note that another sysctl, icmp_msgs_per_sec limits the number |
1238 | of ICMP packets sent on all targets. | |
1cec2cac | 1239 | |
6dbf4bca | 1240 | Default: 1000 |
1da177e4 | 1241 | |
4cdf507d ED |
1242 | icmp_msgs_per_sec - INTEGER |
1243 | Limit maximal number of ICMP packets sent per second from this host. | |
1244 | Only messages whose type matches icmp_ratemask (see below) are | |
b38e7819 ED |
1245 | controlled by this limit. For security reasons, the precise count |
1246 | of messages per second is randomized. | |
1cec2cac | 1247 | |
6dbf4bca | 1248 | Default: 1000 |
1da177e4 | 1249 | |
4cdf507d ED |
1250 | icmp_msgs_burst - INTEGER |
1251 | icmp_msgs_per_sec controls number of ICMP packets sent per second, | |
1252 | while icmp_msgs_burst controls the burst size of these packets. | |
b38e7819 | 1253 | For security reasons, the precise burst size is randomized. |
1cec2cac | 1254 | |
4cdf507d ED |
1255 | Default: 50 |
1256 | ||
1da177e4 LT |
1257 | icmp_ratemask - INTEGER |
1258 | Mask made of ICMP types for which rates are being limited. | |
1cec2cac | 1259 | |
1da177e4 | 1260 | Significant bits: IHGFEDCBA9876543210 |
1cec2cac | 1261 | |
1da177e4 LT |
1262 | Default mask: 0000001100000011000 (6168) |
1263 | ||
1264 | Bit definitions (see include/linux/icmp.h): | |
1cec2cac MCC |
1265 | |
1266 | = ========================= | |
1da177e4 | 1267 | 0 Echo Reply |
1cec2cac MCC |
1268 | 3 Destination Unreachable [1]_ |
1269 | 4 Source Quench [1]_ | |
1da177e4 LT |
1270 | 5 Redirect |
1271 | 8 Echo Request | |
1cec2cac MCC |
1272 | B Time Exceeded [1]_ |
1273 | C Parameter Problem [1]_ | |
1da177e4 LT |
1274 | D Timestamp Request |
1275 | E Timestamp Reply | |
1276 | F Info Request | |
1277 | G Info Reply | |
1278 | H Address Mask Request | |
1279 | I Address Mask Reply | |
1cec2cac | 1280 | = ========================= |
1da177e4 | 1281 | |
1cec2cac | 1282 | .. [1] These are rate limited by default (see default mask above) |
1da177e4 LT |
1283 | |
1284 | icmp_ignore_bogus_error_responses - BOOLEAN | |
1285 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
1286 | frames. Such violations are normally logged via a kernel warning. | |
1287 | If this is set to TRUE, the kernel will not give such warnings, which | |
1288 | will avoid log file clutter. | |
1cec2cac | 1289 | |
e8b265e8 | 1290 | Default: 1 |
1da177e4 | 1291 | |
95f7daf1 H |
1292 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
1293 | ||
02a6d613 PA |
1294 | If zero, icmp error messages are sent with the primary address of |
1295 | the exiting interface. | |
e18f5feb | 1296 | |
95f7daf1 H |
1297 | If non-zero, the message will be sent with the primary address of |
1298 | the interface that received the packet that caused the icmp error. | |
31628201 | 1299 | This is the behaviour many network administrators will expect from |
95f7daf1 | 1300 | a router. And it can make debugging complicated network layouts |
e18f5feb | 1301 | much easier. |
95f7daf1 H |
1302 | |
1303 | Note that if no primary address exists for the interface selected, | |
1304 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 1305 | has one will be used regardless of this setting. |
95f7daf1 H |
1306 | |
1307 | Default: 0 | |
1308 | ||
1da177e4 LT |
1309 | igmp_max_memberships - INTEGER |
1310 | Change the maximum number of multicast groups we can subscribe to. | |
1311 | Default: 20 | |
1312 | ||
d67ef35f JE |
1313 | Theoretical maximum value is bounded by having to send a membership |
1314 | report in a single datagram (i.e. the report can't span multiple | |
1315 | datagrams, or risk confusing the switch and leaving groups you don't | |
1316 | intend to). | |
1da177e4 | 1317 | |
d67ef35f JE |
1318 | The number of supported groups 'M' is bounded by the number of group |
1319 | report entries you can fit into a single datagram of 65535 bytes. | |
1320 | ||
1321 | M = 65536-sizeof (ip header)/(sizeof(Group record)) | |
1322 | ||
1323 | Group records are variable length, with a minimum of 12 bytes. | |
1324 | So net.ipv4.igmp_max_memberships should not be set higher than: | |
1325 | ||
1326 | (65536-24) / 12 = 5459 | |
1327 | ||
1328 | The value 5459 assumes no IP header options, so in practice | |
1329 | this number may be lower. | |
1330 | ||
537377d3 BP |
1331 | igmp_max_msf - INTEGER |
1332 | Maximum number of addresses allowed in the source filter list for a | |
1333 | multicast group. | |
1cec2cac | 1334 | |
537377d3 BP |
1335 | Default: 10 |
1336 | ||
a9fe8e29 | 1337 | igmp_qrv - INTEGER |
537377d3 | 1338 | Controls the IGMP query robustness variable (see RFC2236 8.1). |
1cec2cac | 1339 | |
537377d3 | 1340 | Default: 2 (as specified by RFC2236 8.1) |
1cec2cac | 1341 | |
537377d3 | 1342 | Minimum: 1 (as specified by RFC6636 4.5) |
a9fe8e29 | 1343 | |
1af92836 | 1344 | force_igmp_version - INTEGER |
1cec2cac MCC |
1345 | - 0 - (default) No enforcement of a IGMP version, IGMPv1/v2 fallback |
1346 | allowed. Will back to IGMPv3 mode again if all IGMPv1/v2 Querier | |
1347 | Present timer expires. | |
1348 | - 1 - Enforce to use IGMP version 1. Will also reply IGMPv1 report if | |
1349 | receive IGMPv2/v3 query. | |
1350 | - 2 - Enforce to use IGMP version 2. Will fallback to IGMPv1 if receive | |
1351 | IGMPv1 query message. Will reply report if receive IGMPv3 query. | |
1352 | - 3 - Enforce to use IGMP version 3. The same react with default 0. | |
1353 | ||
1354 | .. note:: | |
1af92836 | 1355 | |
1cec2cac MCC |
1356 | this is not the same with force_mld_version because IGMPv3 RFC3376 |
1357 | Security Considerations does not have clear description that we could | |
1358 | ignore other version messages completely as MLDv2 RFC3810. So make | |
1359 | this value as default 0 is recommended. | |
1af92836 | 1360 | |
1cec2cac MCC |
1361 | ``conf/interface/*`` |
1362 | changes special settings per interface (where | |
1363 | interface" is the name of your network interface) | |
6b226e2f | 1364 | |
1cec2cac MCC |
1365 | ``conf/all/*`` |
1366 | is special, changes the settings for all interfaces | |
6b226e2f | 1367 | |
1da177e4 LT |
1368 | log_martians - BOOLEAN |
1369 | Log packets with impossible addresses to kernel log. | |
1370 | log_martians for the interface will be enabled if at least one of | |
1371 | conf/{all,interface}/log_martians is set to TRUE, | |
1372 | it will be disabled otherwise | |
1373 | ||
1374 | accept_redirects - BOOLEAN | |
1375 | Accept ICMP redirect messages. | |
1376 | accept_redirects for the interface will be enabled if: | |
1cec2cac | 1377 | |
e18f5feb JDB |
1378 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
1379 | forwarding for the interface is enabled | |
1cec2cac | 1380 | |
1da177e4 | 1381 | or |
1cec2cac | 1382 | |
e18f5feb JDB |
1383 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
1384 | case forwarding for the interface is disabled | |
1cec2cac | 1385 | |
1da177e4 | 1386 | accept_redirects for the interface will be disabled otherwise |
1cec2cac MCC |
1387 | |
1388 | default: | |
1389 | ||
1390 | - TRUE (host) | |
1391 | - FALSE (router) | |
1da177e4 LT |
1392 | |
1393 | forwarding - BOOLEAN | |
88a7cddc NJ |
1394 | Enable IP forwarding on this interface. This controls whether packets |
1395 | received _on_ this interface can be forwarded. | |
1da177e4 LT |
1396 | |
1397 | mc_forwarding - BOOLEAN | |
1398 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
1399 | and a multicast routing daemon is required. | |
e18f5feb JDB |
1400 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
1401 | routing for the interface | |
1da177e4 LT |
1402 | |
1403 | medium_id - INTEGER | |
1404 | Integer value used to differentiate the devices by the medium they | |
1405 | are attached to. Two devices can have different id values when | |
1406 | the broadcast packets are received only on one of them. | |
1407 | The default value 0 means that the device is the only interface | |
1408 | to its medium, value of -1 means that medium is not known. | |
e18f5feb | 1409 | |
1da177e4 LT |
1410 | Currently, it is used to change the proxy_arp behavior: |
1411 | the proxy_arp feature is enabled for packets forwarded between | |
1412 | two devices attached to different media. | |
1413 | ||
1414 | proxy_arp - BOOLEAN | |
1415 | Do proxy arp. | |
1cec2cac | 1416 | |
1da177e4 LT |
1417 | proxy_arp for the interface will be enabled if at least one of |
1418 | conf/{all,interface}/proxy_arp is set to TRUE, | |
1419 | it will be disabled otherwise | |
1420 | ||
65324144 JDB |
1421 | proxy_arp_pvlan - BOOLEAN |
1422 | Private VLAN proxy arp. | |
1cec2cac | 1423 | |
65324144 JDB |
1424 | Basically allow proxy arp replies back to the same interface |
1425 | (from which the ARP request/solicitation was received). | |
1426 | ||
1427 | This is done to support (ethernet) switch features, like RFC | |
1428 | 3069, where the individual ports are NOT allowed to | |
1429 | communicate with each other, but they are allowed to talk to | |
1430 | the upstream router. As described in RFC 3069, it is possible | |
1431 | to allow these hosts to communicate through the upstream | |
1432 | router by proxy_arp'ing. Don't need to be used together with | |
1433 | proxy_arp. | |
1434 | ||
1435 | This technology is known by different names: | |
1cec2cac | 1436 | |
65324144 JDB |
1437 | In RFC 3069 it is called VLAN Aggregation. |
1438 | Cisco and Allied Telesyn call it Private VLAN. | |
1439 | Hewlett-Packard call it Source-Port filtering or port-isolation. | |
1440 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | |
1441 | ||
1da177e4 LT |
1442 | shared_media - BOOLEAN |
1443 | Send(router) or accept(host) RFC1620 shared media redirects. | |
176b346b | 1444 | Overrides secure_redirects. |
1cec2cac | 1445 | |
1da177e4 LT |
1446 | shared_media for the interface will be enabled if at least one of |
1447 | conf/{all,interface}/shared_media is set to TRUE, | |
1448 | it will be disabled otherwise | |
1cec2cac | 1449 | |
1da177e4 LT |
1450 | default TRUE |
1451 | ||
1452 | secure_redirects - BOOLEAN | |
176b346b EG |
1453 | Accept ICMP redirect messages only to gateways listed in the |
1454 | interface's current gateway list. Even if disabled, RFC1122 redirect | |
1455 | rules still apply. | |
1cec2cac | 1456 | |
176b346b | 1457 | Overridden by shared_media. |
1cec2cac | 1458 | |
1da177e4 LT |
1459 | secure_redirects for the interface will be enabled if at least one of |
1460 | conf/{all,interface}/secure_redirects is set to TRUE, | |
1461 | it will be disabled otherwise | |
1cec2cac | 1462 | |
1da177e4 LT |
1463 | default TRUE |
1464 | ||
1465 | send_redirects - BOOLEAN | |
1466 | Send redirects, if router. | |
1cec2cac | 1467 | |
1da177e4 LT |
1468 | send_redirects for the interface will be enabled if at least one of |
1469 | conf/{all,interface}/send_redirects is set to TRUE, | |
1470 | it will be disabled otherwise | |
1cec2cac | 1471 | |
1da177e4 LT |
1472 | Default: TRUE |
1473 | ||
1474 | bootp_relay - BOOLEAN | |
1475 | Accept packets with source address 0.b.c.d destined | |
1476 | not to this host as local ones. It is supposed, that | |
1477 | BOOTP relay daemon will catch and forward such packets. | |
1478 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
1479 | for the interface | |
1cec2cac | 1480 | |
1da177e4 | 1481 | default FALSE |
1cec2cac | 1482 | |
1da177e4 LT |
1483 | Not Implemented Yet. |
1484 | ||
1485 | accept_source_route - BOOLEAN | |
1486 | Accept packets with SRR option. | |
1487 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
1488 | with SRR option on the interface | |
1cec2cac MCC |
1489 | |
1490 | default | |
1491 | ||
1492 | - TRUE (router) | |
1493 | - FALSE (host) | |
1da177e4 | 1494 | |
8153a10c | 1495 | accept_local - BOOLEAN |
72b126a4 SB |
1496 | Accept packets with local source addresses. In combination with |
1497 | suitable routing, this can be used to direct packets between two | |
1498 | local interfaces over the wire and have them accepted properly. | |
8153a10c PM |
1499 | default FALSE |
1500 | ||
d0daebc3 TG |
1501 | route_localnet - BOOLEAN |
1502 | Do not consider loopback addresses as martian source or destination | |
1503 | while routing. This enables the use of 127/8 for local routing purposes. | |
1cec2cac | 1504 | |
d0daebc3 TG |
1505 | default FALSE |
1506 | ||
c1cf8422 | 1507 | rp_filter - INTEGER |
1cec2cac MCC |
1508 | - 0 - No source validation. |
1509 | - 1 - Strict mode as defined in RFC3704 Strict Reverse Path | |
1510 | Each incoming packet is tested against the FIB and if the interface | |
1511 | is not the best reverse path the packet check will fail. | |
1512 | By default failed packets are discarded. | |
1513 | - 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
1514 | Each incoming packet's source address is also tested against the FIB | |
1515 | and if the source address is not reachable via any interface | |
1516 | the packet check will fail. | |
c1cf8422 | 1517 | |
e18f5feb | 1518 | Current recommended practice in RFC3704 is to enable strict mode |
bf869c30 | 1519 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
e18f5feb | 1520 | or other complicated routing, then loose mode is recommended. |
c1cf8422 | 1521 | |
1f5865e7 SW |
1522 | The max value from conf/{all,interface}/rp_filter is used |
1523 | when doing source validation on the {interface}. | |
1da177e4 LT |
1524 | |
1525 | Default value is 0. Note that some distributions enable it | |
1526 | in startup scripts. | |
1527 | ||
8cf5d8cc JV |
1528 | src_valid_mark - BOOLEAN |
1529 | - 0 - The fwmark of the packet is not included in reverse path | |
1530 | route lookup. This allows for asymmetric routing configurations | |
1531 | utilizing the fwmark in only one direction, e.g., transparent | |
1532 | proxying. | |
1533 | ||
1534 | - 1 - The fwmark of the packet is included in reverse path route | |
1535 | lookup. This permits rp_filter to function when the fwmark is | |
1536 | used for routing traffic in both directions. | |
1537 | ||
1538 | This setting also affects the utilization of fmwark when | |
1539 | performing source address selection for ICMP replies, or | |
1540 | determining addresses stored for the IPOPT_TS_TSANDADDR and | |
1541 | IPOPT_RR IP options. | |
1542 | ||
1543 | The max value from conf/{all,interface}/src_valid_mark is used. | |
1544 | ||
1545 | Default value is 0. | |
1546 | ||
1da177e4 | 1547 | arp_filter - BOOLEAN |
1cec2cac MCC |
1548 | - 1 - Allows you to have multiple network interfaces on the same |
1549 | subnet, and have the ARPs for each interface be answered | |
1550 | based on whether or not the kernel would route a packet from | |
1551 | the ARP'd IP out that interface (therefore you must use source | |
1552 | based routing for this to work). In other words it allows control | |
1553 | of which cards (usually 1) will respond to an arp request. | |
1554 | ||
1555 | - 0 - (default) The kernel can respond to arp requests with addresses | |
1556 | from other interfaces. This may seem wrong but it usually makes | |
1557 | sense, because it increases the chance of successful communication. | |
1558 | IP addresses are owned by the complete host on Linux, not by | |
1559 | particular interfaces. Only for more complex setups like load- | |
1560 | balancing, does this behaviour cause problems. | |
1da177e4 LT |
1561 | |
1562 | arp_filter for the interface will be enabled if at least one of | |
1563 | conf/{all,interface}/arp_filter is set to TRUE, | |
1564 | it will be disabled otherwise | |
1565 | ||
1566 | arp_announce - INTEGER | |
1567 | Define different restriction levels for announcing the local | |
1568 | source IP address from IP packets in ARP requests sent on | |
1569 | interface: | |
1cec2cac MCC |
1570 | |
1571 | - 0 - (default) Use any local address, configured on any interface | |
1572 | - 1 - Try to avoid local addresses that are not in the target's | |
1573 | subnet for this interface. This mode is useful when target | |
1574 | hosts reachable via this interface require the source IP | |
1575 | address in ARP requests to be part of their logical network | |
1576 | configured on the receiving interface. When we generate the | |
1577 | request we will check all our subnets that include the | |
1578 | target IP and will preserve the source address if it is from | |
1579 | such subnet. If there is no such subnet we select source | |
1580 | address according to the rules for level 2. | |
1581 | - 2 - Always use the best local address for this target. | |
1582 | In this mode we ignore the source address in the IP packet | |
1583 | and try to select local address that we prefer for talks with | |
1584 | the target host. Such local address is selected by looking | |
1585 | for primary IP addresses on all our subnets on the outgoing | |
1586 | interface that include the target IP address. If no suitable | |
1587 | local address is found we select the first local address | |
1588 | we have on the outgoing interface or on all other interfaces, | |
1589 | with the hope we will receive reply for our request and | |
1590 | even sometimes no matter the source IP address we announce. | |
1da177e4 LT |
1591 | |
1592 | The max value from conf/{all,interface}/arp_announce is used. | |
1593 | ||
1594 | Increasing the restriction level gives more chance for | |
1595 | receiving answer from the resolved target while decreasing | |
1596 | the level announces more valid sender's information. | |
1597 | ||
1598 | arp_ignore - INTEGER | |
1599 | Define different modes for sending replies in response to | |
1600 | received ARP requests that resolve local target IP addresses: | |
1cec2cac MCC |
1601 | |
1602 | - 0 - (default): reply for any local target IP address, configured | |
1603 | on any interface | |
1604 | - 1 - reply only if the target IP address is local address | |
1605 | configured on the incoming interface | |
1606 | - 2 - reply only if the target IP address is local address | |
1607 | configured on the incoming interface and both with the | |
1608 | sender's IP address are part from same subnet on this interface | |
1609 | - 3 - do not reply for local addresses configured with scope host, | |
1610 | only resolutions for global and link addresses are replied | |
1611 | - 4-7 - reserved | |
1612 | - 8 - do not reply for all local addresses | |
1da177e4 LT |
1613 | |
1614 | The max value from conf/{all,interface}/arp_ignore is used | |
1615 | when ARP request is received on the {interface} | |
1616 | ||
eefef1cf SH |
1617 | arp_notify - BOOLEAN |
1618 | Define mode for notification of address and device changes. | |
1cec2cac MCC |
1619 | |
1620 | == ========================================================== | |
1621 | 0 (default): do nothing | |
1622 | 1 Generate gratuitous arp requests when device is brought up | |
1623 | or hardware address changes. | |
1624 | == ========================================================== | |
eefef1cf | 1625 | |
c1b1bce8 | 1626 | arp_accept - BOOLEAN |
6d955180 OP |
1627 | Define behavior for gratuitous ARP frames who's IP is not |
1628 | already present in the ARP table: | |
1cec2cac MCC |
1629 | |
1630 | - 0 - don't create new entries in the ARP table | |
1631 | - 1 - create new entries in the ARP table | |
6d955180 OP |
1632 | |
1633 | Both replies and requests type gratuitous arp will trigger the | |
1634 | ARP table to be updated, if this setting is on. | |
1635 | ||
1636 | If the ARP table already contains the IP address of the | |
1637 | gratuitous arp frame, the arp table will be updated regardless | |
1638 | if this setting is on or off. | |
1639 | ||
fcdb44d0 JP |
1640 | arp_evict_nocarrier - BOOLEAN |
1641 | Clears the ARP cache on NOCARRIER events. This option is important for | |
1642 | wireless devices where the ARP cache should not be cleared when roaming | |
1643 | between access points on the same network. In most cases this should | |
1644 | remain as the default (1). | |
1645 | ||
1646 | - 1 - (default): Clear the ARP cache on NOCARRIER events | |
1647 | - 0 - Do not clear ARP cache on NOCARRIER events | |
1648 | ||
89c69d3c YH |
1649 | mcast_solicit - INTEGER |
1650 | The maximum number of multicast probes in INCOMPLETE state, | |
1651 | when the associated hardware address is unknown. Defaults | |
1652 | to 3. | |
1653 | ||
1654 | ucast_solicit - INTEGER | |
1655 | The maximum number of unicast probes in PROBE state, when | |
1656 | the hardware address is being reconfirmed. Defaults to 3. | |
c1b1bce8 | 1657 | |
1da177e4 LT |
1658 | app_solicit - INTEGER |
1659 | The maximum number of probes to send to the user space ARP daemon | |
1660 | via netlink before dropping back to multicast probes (see | |
89c69d3c YH |
1661 | mcast_resolicit). Defaults to 0. |
1662 | ||
1663 | mcast_resolicit - INTEGER | |
1664 | The maximum number of multicast probes after unicast and | |
1665 | app probes in PROBE state. Defaults to 0. | |
1da177e4 LT |
1666 | |
1667 | disable_policy - BOOLEAN | |
1668 | Disable IPSEC policy (SPD) for this interface | |
1669 | ||
1670 | disable_xfrm - BOOLEAN | |
1671 | Disable IPSEC encryption on this interface, whatever the policy | |
1672 | ||
fc4eba58 HFS |
1673 | igmpv2_unsolicited_report_interval - INTEGER |
1674 | The interval in milliseconds in which the next unsolicited | |
1675 | IGMPv1 or IGMPv2 report retransmit will take place. | |
1cec2cac | 1676 | |
fc4eba58 | 1677 | Default: 10000 (10 seconds) |
1da177e4 | 1678 | |
fc4eba58 HFS |
1679 | igmpv3_unsolicited_report_interval - INTEGER |
1680 | The interval in milliseconds in which the next unsolicited | |
1681 | IGMPv3 report retransmit will take place. | |
1cec2cac | 1682 | |
fc4eba58 | 1683 | Default: 1000 (1 seconds) |
1da177e4 | 1684 | |
c0c5a60f VB |
1685 | ignore_routes_with_linkdown - BOOLEAN |
1686 | Ignore routes whose link is down when performing a FIB lookup. | |
1687 | ||
d922e1cb MS |
1688 | promote_secondaries - BOOLEAN |
1689 | When a primary IP address is removed from this interface | |
1690 | promote a corresponding secondary IP address instead of | |
1691 | removing all the corresponding secondary IP addresses. | |
1692 | ||
12b74dfa JB |
1693 | drop_unicast_in_l2_multicast - BOOLEAN |
1694 | Drop any unicast IP packets that are received in link-layer | |
1695 | multicast (or broadcast) frames. | |
1cec2cac | 1696 | |
12b74dfa JB |
1697 | This behavior (for multicast) is actually a SHOULD in RFC |
1698 | 1122, but is disabled by default for compatibility reasons. | |
1cec2cac | 1699 | |
12b74dfa JB |
1700 | Default: off (0) |
1701 | ||
97daf331 JB |
1702 | drop_gratuitous_arp - BOOLEAN |
1703 | Drop all gratuitous ARP frames, for example if there's a known | |
1704 | good ARP proxy on the network and such frames need not be used | |
1705 | (or in the case of 802.11, must not be used to prevent attacks.) | |
1cec2cac | 1706 | |
97daf331 JB |
1707 | Default: off (0) |
1708 | ||
d922e1cb | 1709 | |
1da177e4 LT |
1710 | tag - INTEGER |
1711 | Allows you to write a number, which can be used as required. | |
1cec2cac | 1712 | |
1da177e4 LT |
1713 | Default value is 0. |
1714 | ||
e69948a0 | 1715 | xfrm4_gc_thresh - INTEGER |
837f7411 | 1716 | (Obsolete since linux-4.14) |
e69948a0 AD |
1717 | The threshold at which we will start garbage collecting for IPv4 |
1718 | destination cache entries. At twice this value the system will | |
3c2a89dd | 1719 | refuse new allocations. |
e69948a0 | 1720 | |
87583ebb PD |
1721 | igmp_link_local_mcast_reports - BOOLEAN |
1722 | Enable IGMP reports for link local multicast groups in the | |
1723 | 224.0.0.X range. | |
1cec2cac | 1724 | |
87583ebb PD |
1725 | Default TRUE |
1726 | ||
1da177e4 LT |
1727 | Alexey Kuznetsov. |
1728 | kuznet@ms2.inr.ac.ru | |
1729 | ||
1730 | Updated by: | |
1da177e4 | 1731 | |
1cec2cac MCC |
1732 | - Andi Kleen |
1733 | ak@muc.de | |
1734 | - Nicolas Delon | |
1735 | delon.nicolas@wanadoo.fr | |
1da177e4 LT |
1736 | |
1737 | ||
1738 | ||
1cec2cac MCC |
1739 | |
1740 | /proc/sys/net/ipv6/* Variables | |
1741 | ============================== | |
1da177e4 LT |
1742 | |
1743 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
1744 | apply to IPv6 [XXX?]. | |
1745 | ||
1746 | bindv6only - BOOLEAN | |
1747 | Default value for IPV6_V6ONLY socket option, | |
e18f5feb | 1748 | which restricts use of the IPv6 socket to IPv6 communication |
1da177e4 | 1749 | only. |
1cec2cac MCC |
1750 | |
1751 | - TRUE: disable IPv4-mapped address feature | |
1752 | - FALSE: enable IPv4-mapped address feature | |
1da177e4 | 1753 | |
d5c073ca | 1754 | Default: FALSE (as specified in RFC3493) |
1da177e4 | 1755 | |
6444f72b FF |
1756 | flowlabel_consistency - BOOLEAN |
1757 | Protect the consistency (and unicity) of flow label. | |
1758 | You have to disable it to use IPV6_FL_F_REFLECT flag on the | |
1759 | flow label manager. | |
1cec2cac MCC |
1760 | |
1761 | - TRUE: enabled | |
1762 | - FALSE: disabled | |
1763 | ||
6444f72b FF |
1764 | Default: TRUE |
1765 | ||
42240901 TH |
1766 | auto_flowlabels - INTEGER |
1767 | Automatically generate flow labels based on a flow hash of the | |
1768 | packet. This allows intermediate devices, such as routers, to | |
1769 | identify packet flows for mechanisms like Equal Cost Multipath | |
cb1ce2ef | 1770 | Routing (see RFC 6438). |
1cec2cac MCC |
1771 | |
1772 | = =========================================================== | |
1773 | 0 automatic flow labels are completely disabled | |
1774 | 1 automatic flow labels are enabled by default, they can be | |
42240901 TH |
1775 | disabled on a per socket basis using the IPV6_AUTOFLOWLABEL |
1776 | socket option | |
1cec2cac | 1777 | 2 automatic flow labels are allowed, they may be enabled on a |
42240901 | 1778 | per socket basis using the IPV6_AUTOFLOWLABEL socket option |
1cec2cac | 1779 | 3 automatic flow labels are enabled and enforced, they cannot |
42240901 | 1780 | be disabled by the socket option |
1cec2cac MCC |
1781 | = =========================================================== |
1782 | ||
b5677416 | 1783 | Default: 1 |
cb1ce2ef | 1784 | |
82a584b7 TH |
1785 | flowlabel_state_ranges - BOOLEAN |
1786 | Split the flow label number space into two ranges. 0-0x7FFFF is | |
1787 | reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF | |
1788 | is reserved for stateless flow labels as described in RFC6437. | |
1cec2cac MCC |
1789 | |
1790 | - TRUE: enabled | |
1791 | - FALSE: disabled | |
1792 | ||
82a584b7 TH |
1793 | Default: true |
1794 | ||
323a53c4 ED |
1795 | flowlabel_reflect - INTEGER |
1796 | Control flow label reflection. Needed for Path MTU | |
22b6722b JS |
1797 | Discovery to work with Equal Cost Multipath Routing in anycast |
1798 | environments. See RFC 7690 and: | |
1799 | https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01 | |
323a53c4 | 1800 | |
a346abe0 | 1801 | This is a bitmask. |
323a53c4 | 1802 | |
1cec2cac MCC |
1803 | - 1: enabled for established flows |
1804 | ||
1805 | Note that this prevents automatic flowlabel changes, as done | |
1806 | in "tcp: change IPv6 flow-label upon receiving spurious retransmission" | |
1807 | and "tcp: Change txhash on every SYN and RTO retransmit" | |
323a53c4 | 1808 | |
1cec2cac MCC |
1809 | - 2: enabled for TCP RESET packets (no active listener) |
1810 | If set, a RST packet sent in response to a SYN packet on a closed | |
1811 | port will reflect the incoming flow label. | |
323a53c4 | 1812 | |
1cec2cac | 1813 | - 4: enabled for ICMPv6 echo reply messages. |
a346abe0 | 1814 | |
323a53c4 | 1815 | Default: 0 |
22b6722b | 1816 | |
b4bac172 DA |
1817 | fib_multipath_hash_policy - INTEGER |
1818 | Controls which hash policy to use for multipath routes. | |
1cec2cac | 1819 | |
b4bac172 | 1820 | Default: 0 (Layer 3) |
1cec2cac | 1821 | |
b4bac172 | 1822 | Possible values: |
1cec2cac MCC |
1823 | |
1824 | - 0 - Layer 3 (source and destination addresses plus flow label) | |
1825 | - 1 - Layer 4 (standard 5-tuple) | |
1826 | - 2 - Layer 3 or inner Layer 3 if present | |
73c2c5cb IS |
1827 | - 3 - Custom multipath hash. Fields used for multipath hash calculation |
1828 | are determined by fib_multipath_hash_fields sysctl | |
b4bac172 | 1829 | |
ed13923f IS |
1830 | fib_multipath_hash_fields - UNSIGNED INTEGER |
1831 | When fib_multipath_hash_policy is set to 3 (custom multipath hash), the | |
1832 | fields used for multipath hash calculation are determined by this | |
1833 | sysctl. | |
1834 | ||
1835 | This value is a bitmask which enables various fields for multipath hash | |
1836 | calculation. | |
1837 | ||
1838 | Possible fields are: | |
1839 | ||
1840 | ====== ============================ | |
1841 | 0x0001 Source IP address | |
1842 | 0x0002 Destination IP address | |
1843 | 0x0004 IP protocol | |
1844 | 0x0008 Flow Label | |
1845 | 0x0010 Source port | |
1846 | 0x0020 Destination port | |
1847 | 0x0040 Inner source IP address | |
1848 | 0x0080 Inner destination IP address | |
1849 | 0x0100 Inner IP protocol | |
1850 | 0x0200 Inner Flow Label | |
1851 | 0x0400 Inner source port | |
1852 | 0x0800 Inner destination port | |
1853 | ====== ============================ | |
1854 | ||
1855 | Default: 0x0007 (source IP, destination IP and IP protocol) | |
1856 | ||
509aba3b FLB |
1857 | anycast_src_echo_reply - BOOLEAN |
1858 | Controls the use of anycast addresses as source addresses for ICMPv6 | |
1859 | echo reply | |
1cec2cac MCC |
1860 | |
1861 | - TRUE: enabled | |
1862 | - FALSE: disabled | |
1863 | ||
509aba3b FLB |
1864 | Default: FALSE |
1865 | ||
9f0761c1 HFS |
1866 | idgen_delay - INTEGER |
1867 | Controls the delay in seconds after which time to retry | |
1868 | privacy stable address generation if a DAD conflict is | |
1869 | detected. | |
1cec2cac | 1870 | |
9f0761c1 HFS |
1871 | Default: 1 (as specified in RFC7217) |
1872 | ||
1873 | idgen_retries - INTEGER | |
1874 | Controls the number of retries to generate a stable privacy | |
1875 | address if a DAD conflict is detected. | |
1cec2cac | 1876 | |
9f0761c1 HFS |
1877 | Default: 3 (as specified in RFC7217) |
1878 | ||
2f711939 HFS |
1879 | mld_qrv - INTEGER |
1880 | Controls the MLD query robustness variable (see RFC3810 9.1). | |
1cec2cac | 1881 | |
2f711939 | 1882 | Default: 2 (as specified by RFC3810 9.1) |
1cec2cac | 1883 | |
2f711939 HFS |
1884 | Minimum: 1 (as specified by RFC6636 4.5) |
1885 | ||
ab913455 | 1886 | max_dst_opts_number - INTEGER |
47d3d7ac TH |
1887 | Maximum number of non-padding TLVs allowed in a Destination |
1888 | options extension header. If this value is less than zero | |
1889 | then unknown options are disallowed and the number of known | |
1890 | TLVs allowed is the absolute value of this number. | |
1cec2cac | 1891 | |
47d3d7ac TH |
1892 | Default: 8 |
1893 | ||
ab913455 | 1894 | max_hbh_opts_number - INTEGER |
47d3d7ac TH |
1895 | Maximum number of non-padding TLVs allowed in a Hop-by-Hop |
1896 | options extension header. If this value is less than zero | |
1897 | then unknown options are disallowed and the number of known | |
1898 | TLVs allowed is the absolute value of this number. | |
1cec2cac | 1899 | |
47d3d7ac TH |
1900 | Default: 8 |
1901 | ||
ab913455 | 1902 | max_dst_opts_length - INTEGER |
47d3d7ac TH |
1903 | Maximum length allowed for a Destination options extension |
1904 | header. | |
1cec2cac | 1905 | |
47d3d7ac TH |
1906 | Default: INT_MAX (unlimited) |
1907 | ||
ab913455 | 1908 | max_hbh_length - INTEGER |
47d3d7ac TH |
1909 | Maximum length allowed for a Hop-by-Hop options extension |
1910 | header. | |
1cec2cac | 1911 | |
47d3d7ac TH |
1912 | Default: INT_MAX (unlimited) |
1913 | ||
7c6bb7d2 DA |
1914 | skip_notify_on_dev_down - BOOLEAN |
1915 | Controls whether an RTM_DELROUTE message is generated for routes | |
1916 | removed when a device is taken down or deleted. IPv4 does not | |
1917 | generate this message; IPv6 does by default. Setting this sysctl | |
1918 | to true skips the message, making IPv4 and IPv6 on par in relying | |
1919 | on userspace caches to track link events and evict routes. | |
1cec2cac | 1920 | |
7c6bb7d2 DA |
1921 | Default: false (generate message) |
1922 | ||
4f80116d RP |
1923 | nexthop_compat_mode - BOOLEAN |
1924 | New nexthop API provides a means for managing nexthops independent of | |
1925 | prefixes. Backwards compatibilty with old route format is enabled by | |
1926 | default which means route dumps and notifications contain the new | |
1927 | nexthop attribute but also the full, expanded nexthop definition. | |
1928 | Further, updates or deletes of a nexthop configuration generate route | |
1929 | notifications for each fib entry using the nexthop. Once a system | |
1930 | understands the new API, this sysctl can be disabled to achieve full | |
1931 | performance benefits of the new API by disabling the nexthop expansion | |
1932 | and extraneous notifications. | |
1933 | Default: true (backward compat mode) | |
1934 | ||
907eea48 AC |
1935 | fib_notify_on_flag_change - INTEGER |
1936 | Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/ | |
6fad361a | 1937 | RTM_F_TRAP/RTM_F_OFFLOAD_FAILED flags are changed. |
907eea48 AC |
1938 | |
1939 | After installing a route to the kernel, user space receives an | |
1940 | acknowledgment, which means the route was installed in the kernel, | |
1941 | but not necessarily in hardware. | |
1942 | It is also possible for a route already installed in hardware to change | |
1943 | its action and therefore its flags. For example, a host route that is | |
1944 | trapping packets can be "promoted" to perform decapsulation following | |
1945 | the installation of an IPinIP/VXLAN tunnel. | |
1946 | The notifications will indicate to user-space the state of the route. | |
1947 | ||
1948 | Default: 0 (Do not emit notifications.) | |
1949 | ||
1950 | Possible values: | |
1951 | ||
1952 | - 0 - Do not emit notifications. | |
1953 | - 1 - Emit notifications. | |
6fad361a | 1954 | - 2 - Emit notifications only for RTM_F_OFFLOAD_FAILED flag change. |
907eea48 | 1955 | |
de8e80a5 JI |
1956 | ioam6_id - INTEGER |
1957 | Define the IOAM id of this node. Uses only 24 bits out of 32 in total. | |
1958 | ||
1959 | Min: 0 | |
1960 | Max: 0xFFFFFF | |
1961 | ||
1962 | Default: 0xFFFFFF | |
1963 | ||
1964 | ioam6_id_wide - LONG INTEGER | |
1965 | Define the wide IOAM id of this node. Uses only 56 bits out of 64 in | |
1966 | total. Can be different from ioam6_id. | |
1967 | ||
1968 | Min: 0 | |
1969 | Max: 0xFFFFFFFFFFFFFF | |
1970 | ||
1971 | Default: 0xFFFFFFFFFFFFFF | |
1972 | ||
1da177e4 LT |
1973 | IPv6 Fragmentation: |
1974 | ||
1975 | ip6frag_high_thresh - INTEGER | |
e18f5feb | 1976 | Maximum memory used to reassemble IPv6 fragments. When |
1da177e4 LT |
1977 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
1978 | the fragment handler will toss packets until ip6frag_low_thresh | |
1979 | is reached. | |
e18f5feb | 1980 | |
1da177e4 | 1981 | ip6frag_low_thresh - INTEGER |
e18f5feb | 1982 | See ip6frag_high_thresh |
1da177e4 LT |
1983 | |
1984 | ip6frag_time - INTEGER | |
1985 | Time in seconds to keep an IPv6 fragment in memory. | |
1986 | ||
1cec2cac | 1987 | ``conf/default/*``: |
1da177e4 LT |
1988 | Change the interface-specific default settings. |
1989 | ||
fc024c5c PR |
1990 | These settings would be used during creating new interfaces. |
1991 | ||
1da177e4 | 1992 | |
1cec2cac | 1993 | ``conf/all/*``: |
e18f5feb | 1994 | Change all the interface-specific settings. |
1da177e4 LT |
1995 | |
1996 | [XXX: Other special features than forwarding?] | |
1997 | ||
fc024c5c PR |
1998 | conf/all/disable_ipv6 - BOOLEAN |
1999 | Changing this value is same as changing ``conf/default/disable_ipv6`` | |
2000 | setting and also all per-interface ``disable_ipv6`` settings to the same | |
2001 | value. | |
2002 | ||
2003 | Reading this value does not have any particular meaning. It does not say | |
2004 | whether IPv6 support is enabled or disabled. Returned value can be 1 | |
2005 | also in the case when some interface has ``disable_ipv6`` set to 0 and | |
2006 | has configured IPv6 addresses. | |
2007 | ||
1da177e4 | 2008 | conf/all/forwarding - BOOLEAN |
e18f5feb | 2009 | Enable global IPv6 forwarding between all interfaces. |
1da177e4 | 2010 | |
e18f5feb | 2011 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
1da177e4 LT |
2012 | to control which interfaces may forward packets and which not. |
2013 | ||
e18f5feb | 2014 | This also sets all interfaces' Host/Router setting |
1da177e4 LT |
2015 | 'forwarding' to the specified value. See below for details. |
2016 | ||
2017 | This referred to as global forwarding. | |
2018 | ||
fbea49e1 YH |
2019 | proxy_ndp - BOOLEAN |
2020 | Do proxy ndp. | |
2021 | ||
219b5f29 LV |
2022 | fwmark_reflect - BOOLEAN |
2023 | Controls the fwmark of kernel-generated IPv6 reply packets that are not | |
2024 | associated with a socket for example, TCP RSTs or ICMPv6 echo replies). | |
2025 | If unset, these packets have a fwmark of zero. If set, they have the | |
2026 | fwmark of the packet they are replying to. | |
1cec2cac | 2027 | |
219b5f29 LV |
2028 | Default: 0 |
2029 | ||
1cec2cac | 2030 | ``conf/interface/*``: |
1da177e4 LT |
2031 | Change special settings per interface. |
2032 | ||
e18f5feb | 2033 | The functional behaviour for certain settings is different |
1da177e4 LT |
2034 | depending on whether local forwarding is enabled or not. |
2035 | ||
605b91c8 | 2036 | accept_ra - INTEGER |
1da177e4 | 2037 | Accept Router Advertisements; autoconfigure using them. |
e18f5feb | 2038 | |
026359bc TA |
2039 | It also determines whether or not to transmit Router |
2040 | Solicitations. If and only if the functional setting is to | |
2041 | accept Router Advertisements, Router Solicitations will be | |
2042 | transmitted. | |
2043 | ||
ae8abfa0 | 2044 | Possible values are: |
ae8abfa0 | 2045 | |
1cec2cac MCC |
2046 | == =========================================================== |
2047 | 0 Do not accept Router Advertisements. | |
2048 | 1 Accept Router Advertisements if forwarding is disabled. | |
2049 | 2 Overrule forwarding behaviour. Accept Router Advertisements | |
2050 | even if forwarding is enabled. | |
2051 | == =========================================================== | |
2052 | ||
2053 | Functional default: | |
2054 | ||
2055 | - enabled if local forwarding is disabled. | |
2056 | - disabled if local forwarding is enabled. | |
1da177e4 | 2057 | |
65f5c7c1 YH |
2058 | accept_ra_defrtr - BOOLEAN |
2059 | Learn default router in Router Advertisement. | |
2060 | ||
1cec2cac MCC |
2061 | Functional default: |
2062 | ||
2063 | - enabled if accept_ra is enabled. | |
2064 | - disabled if accept_ra is disabled. | |
65f5c7c1 | 2065 | |
6b2e04bc PC |
2066 | ra_defrtr_metric - UNSIGNED INTEGER |
2067 | Route metric for default route learned in Router Advertisement. This value | |
2068 | will be assigned as metric for the default route learned via IPv6 Router | |
2069 | Advertisement. Takes affect only if accept_ra_defrtr is enabled. | |
2070 | ||
2071 | Possible values: | |
2072 | 1 to 0xFFFFFFFF | |
2073 | ||
2074 | Default: IP6_RT_PRIO_USER i.e. 1024. | |
2075 | ||
d9333196 BG |
2076 | accept_ra_from_local - BOOLEAN |
2077 | Accept RA with source-address that is found on local machine | |
1cec2cac MCC |
2078 | if the RA is otherwise proper and able to be accepted. |
2079 | ||
2080 | Default is to NOT accept these as it may be an un-intended | |
2081 | network loop. | |
d9333196 BG |
2082 | |
2083 | Functional default: | |
1cec2cac MCC |
2084 | |
2085 | - enabled if accept_ra_from_local is enabled | |
2086 | on a specific interface. | |
2087 | - disabled if accept_ra_from_local is disabled | |
2088 | on a specific interface. | |
d9333196 | 2089 | |
8013d1d7 HL |
2090 | accept_ra_min_hop_limit - INTEGER |
2091 | Minimum hop limit Information in Router Advertisement. | |
2092 | ||
2093 | Hop limit Information in Router Advertisement less than this | |
2094 | variable shall be ignored. | |
2095 | ||
2096 | Default: 1 | |
2097 | ||
c4fd30eb | 2098 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 2099 | Learn Prefix Information in Router Advertisement. |
c4fd30eb | 2100 | |
1cec2cac MCC |
2101 | Functional default: |
2102 | ||
2103 | - enabled if accept_ra is enabled. | |
2104 | - disabled if accept_ra is disabled. | |
c4fd30eb | 2105 | |
bbea124b JS |
2106 | accept_ra_rt_info_min_plen - INTEGER |
2107 | Minimum prefix length of Route Information in RA. | |
2108 | ||
2109 | Route Information w/ prefix smaller than this variable shall | |
2110 | be ignored. | |
2111 | ||
1cec2cac MCC |
2112 | Functional default: |
2113 | ||
2114 | * 0 if accept_ra_rtr_pref is enabled. | |
2115 | * -1 if accept_ra_rtr_pref is disabled. | |
bbea124b | 2116 | |
09c884d4 YH |
2117 | accept_ra_rt_info_max_plen - INTEGER |
2118 | Maximum prefix length of Route Information in RA. | |
2119 | ||
bbea124b JS |
2120 | Route Information w/ prefix larger than this variable shall |
2121 | be ignored. | |
09c884d4 | 2122 | |
1cec2cac MCC |
2123 | Functional default: |
2124 | ||
2125 | * 0 if accept_ra_rtr_pref is enabled. | |
2126 | * -1 if accept_ra_rtr_pref is disabled. | |
09c884d4 | 2127 | |
930d6ff2 YH |
2128 | accept_ra_rtr_pref - BOOLEAN |
2129 | Accept Router Preference in RA. | |
2130 | ||
1cec2cac MCC |
2131 | Functional default: |
2132 | ||
2133 | - enabled if accept_ra is enabled. | |
2134 | - disabled if accept_ra is disabled. | |
930d6ff2 | 2135 | |
c2943f14 HH |
2136 | accept_ra_mtu - BOOLEAN |
2137 | Apply the MTU value specified in RA option 5 (RFC4861). If | |
2138 | disabled, the MTU specified in the RA will be ignored. | |
2139 | ||
1cec2cac MCC |
2140 | Functional default: |
2141 | ||
2142 | - enabled if accept_ra is enabled. | |
2143 | - disabled if accept_ra is disabled. | |
c2943f14 | 2144 | |
1da177e4 LT |
2145 | accept_redirects - BOOLEAN |
2146 | Accept Redirects. | |
2147 | ||
1cec2cac MCC |
2148 | Functional default: |
2149 | ||
2150 | - enabled if local forwarding is disabled. | |
2151 | - disabled if local forwarding is enabled. | |
1da177e4 | 2152 | |
0bcbc926 YH |
2153 | accept_source_route - INTEGER |
2154 | Accept source routing (routing extension header). | |
2155 | ||
1cec2cac MCC |
2156 | - >= 0: Accept only routing header type 2. |
2157 | - < 0: Do not accept routing header. | |
0bcbc926 YH |
2158 | |
2159 | Default: 0 | |
2160 | ||
1da177e4 | 2161 | autoconf - BOOLEAN |
e18f5feb | 2162 | Autoconfigure addresses using Prefix Information in Router |
1da177e4 LT |
2163 | Advertisements. |
2164 | ||
1cec2cac MCC |
2165 | Functional default: |
2166 | ||
2167 | - enabled if accept_ra_pinfo is enabled. | |
2168 | - disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
2169 | |
2170 | dad_transmits - INTEGER | |
2171 | The amount of Duplicate Address Detection probes to send. | |
1cec2cac | 2172 | |
1da177e4 | 2173 | Default: 1 |
e18f5feb | 2174 | |
605b91c8 | 2175 | forwarding - INTEGER |
e18f5feb | 2176 | Configure interface-specific Host/Router behaviour. |
1da177e4 | 2177 | |
1cec2cac MCC |
2178 | .. note:: |
2179 | ||
2180 | It is recommended to have the same setting on all | |
2181 | interfaces; mixed router/host scenarios are rather uncommon. | |
1da177e4 | 2182 | |
ae8abfa0 | 2183 | Possible values are: |
ae8abfa0 | 2184 | |
1cec2cac MCC |
2185 | - 0 Forwarding disabled |
2186 | - 1 Forwarding enabled | |
2187 | ||
2188 | **FALSE (0)**: | |
1da177e4 LT |
2189 | |
2190 | By default, Host behaviour is assumed. This means: | |
2191 | ||
2192 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
026359bc TA |
2193 | 2. If accept_ra is TRUE (default), transmit Router |
2194 | Solicitations. | |
e18f5feb | 2195 | 3. If accept_ra is TRUE (default), accept Router |
1da177e4 LT |
2196 | Advertisements (and do autoconfiguration). |
2197 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
2198 | ||
1cec2cac | 2199 | **TRUE (1)**: |
1da177e4 | 2200 | |
e18f5feb | 2201 | If local forwarding is enabled, Router behaviour is assumed. |
1da177e4 LT |
2202 | This means exactly the reverse from the above: |
2203 | ||
2204 | 1. IsRouter flag is set in Neighbour Advertisements. | |
026359bc | 2205 | 2. Router Solicitations are not sent unless accept_ra is 2. |
ae8abfa0 | 2206 | 3. Router Advertisements are ignored unless accept_ra is 2. |
1da177e4 LT |
2207 | 4. Redirects are ignored. |
2208 | ||
ae8abfa0 | 2209 | Default: 0 (disabled) if global forwarding is disabled (default), |
1cec2cac | 2210 | otherwise 1 (enabled). |
1da177e4 LT |
2211 | |
2212 | hop_limit - INTEGER | |
2213 | Default Hop Limit to set. | |
1cec2cac | 2214 | |
1da177e4 LT |
2215 | Default: 64 |
2216 | ||
2217 | mtu - INTEGER | |
2218 | Default Maximum Transfer Unit | |
1cec2cac | 2219 | |
1da177e4 LT |
2220 | Default: 1280 (IPv6 required minimum) |
2221 | ||
35a256fe TH |
2222 | ip_nonlocal_bind - BOOLEAN |
2223 | If set, allows processes to bind() to non-local IPv6 addresses, | |
2224 | which can be quite useful - but may break some applications. | |
1cec2cac | 2225 | |
35a256fe TH |
2226 | Default: 0 |
2227 | ||
52e16356 YH |
2228 | router_probe_interval - INTEGER |
2229 | Minimum interval (in seconds) between Router Probing described | |
2230 | in RFC4191. | |
2231 | ||
2232 | Default: 60 | |
2233 | ||
1da177e4 LT |
2234 | router_solicitation_delay - INTEGER |
2235 | Number of seconds to wait after interface is brought up | |
2236 | before sending Router Solicitations. | |
1cec2cac | 2237 | |
1da177e4 LT |
2238 | Default: 1 |
2239 | ||
2240 | router_solicitation_interval - INTEGER | |
2241 | Number of seconds to wait between Router Solicitations. | |
1cec2cac | 2242 | |
1da177e4 LT |
2243 | Default: 4 |
2244 | ||
2245 | router_solicitations - INTEGER | |
e18f5feb | 2246 | Number of Router Solicitations to send until assuming no |
1da177e4 | 2247 | routers are present. |
1cec2cac | 2248 | |
1da177e4 LT |
2249 | Default: 3 |
2250 | ||
3985e8a3 EK |
2251 | use_oif_addrs_only - BOOLEAN |
2252 | When enabled, the candidate source addresses for destinations | |
2253 | routed via this interface are restricted to the set of addresses | |
2254 | configured on this interface (vis. RFC 6724, section 4). | |
2255 | ||
2256 | Default: false | |
2257 | ||
1da177e4 LT |
2258 | use_tempaddr - INTEGER |
2259 | Preference for Privacy Extensions (RFC3041). | |
1cec2cac MCC |
2260 | |
2261 | * <= 0 : disable Privacy Extensions | |
2262 | * == 1 : enable Privacy Extensions, but prefer public | |
2263 | addresses over temporary addresses. | |
2264 | * > 1 : enable Privacy Extensions and prefer temporary | |
2265 | addresses over public addresses. | |
2266 | ||
2267 | Default: | |
2268 | ||
2269 | * 0 (for most devices) | |
2270 | * -1 (for point-to-point devices and loopback devices) | |
1da177e4 LT |
2271 | |
2272 | temp_valid_lft - INTEGER | |
2273 | valid lifetime (in seconds) for temporary addresses. | |
1cec2cac | 2274 | |
969c5464 | 2275 | Default: 172800 (2 days) |
1da177e4 LT |
2276 | |
2277 | temp_prefered_lft - INTEGER | |
2278 | Preferred lifetime (in seconds) for temporary addresses. | |
1cec2cac | 2279 | |
1da177e4 LT |
2280 | Default: 86400 (1 day) |
2281 | ||
f1705ec1 DA |
2282 | keep_addr_on_down - INTEGER |
2283 | Keep all IPv6 addresses on an interface down event. If set static | |
2284 | global addresses with no expiration time are not flushed. | |
1cec2cac MCC |
2285 | |
2286 | * >0 : enabled | |
2287 | * 0 : system default | |
2288 | * <0 : disabled | |
f1705ec1 DA |
2289 | |
2290 | Default: 0 (addresses are removed) | |
2291 | ||
1da177e4 LT |
2292 | max_desync_factor - INTEGER |
2293 | Maximum value for DESYNC_FACTOR, which is a random value | |
e18f5feb | 2294 | that ensures that clients don't synchronize with each |
1da177e4 LT |
2295 | other and generate new addresses at exactly the same time. |
2296 | value is in seconds. | |
1cec2cac | 2297 | |
1da177e4 | 2298 | Default: 600 |
e18f5feb | 2299 | |
1da177e4 LT |
2300 | regen_max_retry - INTEGER |
2301 | Number of attempts before give up attempting to generate | |
2302 | valid temporary addresses. | |
1cec2cac | 2303 | |
1da177e4 LT |
2304 | Default: 5 |
2305 | ||
2306 | max_addresses - INTEGER | |
e79dc484 BH |
2307 | Maximum number of autoconfigured addresses per interface. Setting |
2308 | to zero disables the limitation. It is not recommended to set this | |
2309 | value too large (or to zero) because it would be an easy way to | |
2310 | crash the kernel by allowing too many addresses to be created. | |
1cec2cac | 2311 | |
1da177e4 LT |
2312 | Default: 16 |
2313 | ||
778d80be | 2314 | disable_ipv6 - BOOLEAN |
9bdd8d40 BH |
2315 | Disable IPv6 operation. If accept_dad is set to 2, this value |
2316 | will be dynamically set to TRUE if DAD fails for the link-local | |
2317 | address. | |
1cec2cac | 2318 | |
778d80be YH |
2319 | Default: FALSE (enable IPv6 operation) |
2320 | ||
56d417b1 BH |
2321 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
2322 | it will dynamically create a link-local address on the given | |
2323 | interface and start Duplicate Address Detection, if necessary. | |
2324 | ||
2325 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
2f0aaf7f LB |
2326 | it will dynamically delete all addresses and routes on the given |
2327 | interface. From now on it will not possible to add addresses/routes | |
2328 | to the selected interface. | |
56d417b1 | 2329 | |
1b34be74 YH |
2330 | accept_dad - INTEGER |
2331 | Whether to accept DAD (Duplicate Address Detection). | |
1cec2cac MCC |
2332 | |
2333 | == ============================================================== | |
2334 | 0 Disable DAD | |
2335 | 1 Enable DAD (default) | |
2336 | 2 Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
2337 | link-local address has been found. | |
2338 | == ============================================================== | |
1b34be74 | 2339 | |
35e015e1 MC |
2340 | DAD operation and mode on a given interface will be selected according |
2341 | to the maximum value of conf/{all,interface}/accept_dad. | |
2342 | ||
f7734fdf OP |
2343 | force_tllao - BOOLEAN |
2344 | Enable sending the target link-layer address option even when | |
2345 | responding to a unicast neighbor solicitation. | |
1cec2cac | 2346 | |
f7734fdf OP |
2347 | Default: FALSE |
2348 | ||
2349 | Quoting from RFC 2461, section 4.4, Target link-layer address: | |
2350 | ||
2351 | "The option MUST be included for multicast solicitations in order to | |
2352 | avoid infinite Neighbor Solicitation "recursion" when the peer node | |
2353 | does not have a cache entry to return a Neighbor Advertisements | |
2354 | message. When responding to unicast solicitations, the option can be | |
2355 | omitted since the sender of the solicitation has the correct link- | |
2356 | layer address; otherwise it would not have be able to send the unicast | |
2357 | solicitation in the first place. However, including the link-layer | |
2358 | address in this case adds little overhead and eliminates a potential | |
2359 | race condition where the sender deletes the cached link-layer address | |
2360 | prior to receiving a response to a previous solicitation." | |
2361 | ||
db2b620a HFS |
2362 | ndisc_notify - BOOLEAN |
2363 | Define mode for notification of address and device changes. | |
1cec2cac MCC |
2364 | |
2365 | * 0 - (default): do nothing | |
2366 | * 1 - Generate unsolicited neighbour advertisements when device is brought | |
2367 | up or hardware address changes. | |
db2b620a | 2368 | |
2210d6b2 MŻ |
2369 | ndisc_tclass - INTEGER |
2370 | The IPv6 Traffic Class to use by default when sending IPv6 Neighbor | |
2371 | Discovery (Router Solicitation, Router Advertisement, Neighbor | |
2372 | Solicitation, Neighbor Advertisement, Redirect) messages. | |
2373 | These 8 bits can be interpreted as 6 high order bits holding the DSCP | |
2374 | value and 2 low order bits representing ECN (which you probably want | |
2375 | to leave cleared). | |
1cec2cac MCC |
2376 | |
2377 | * 0 - (default) | |
2210d6b2 | 2378 | |
18ac597a JP |
2379 | ndisc_evict_nocarrier - BOOLEAN |
2380 | Clears the neighbor discovery table on NOCARRIER events. This option is | |
2381 | important for wireless devices where the neighbor discovery cache should | |
2382 | not be cleared when roaming between access points on the same network. | |
2383 | In most cases this should remain as the default (1). | |
2384 | ||
2385 | - 1 - (default): Clear neighbor discover cache on NOCARRIER events. | |
2386 | - 0 - Do not clear neighbor discovery cache on NOCARRIER events. | |
2387 | ||
fc4eba58 HFS |
2388 | mldv1_unsolicited_report_interval - INTEGER |
2389 | The interval in milliseconds in which the next unsolicited | |
2390 | MLDv1 report retransmit will take place. | |
1cec2cac | 2391 | |
fc4eba58 HFS |
2392 | Default: 10000 (10 seconds) |
2393 | ||
2394 | mldv2_unsolicited_report_interval - INTEGER | |
2395 | The interval in milliseconds in which the next unsolicited | |
2396 | MLDv2 report retransmit will take place. | |
1cec2cac | 2397 | |
fc4eba58 HFS |
2398 | Default: 1000 (1 second) |
2399 | ||
f2127810 | 2400 | force_mld_version - INTEGER |
1cec2cac MCC |
2401 | * 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed |
2402 | * 1 - Enforce to use MLD version 1 | |
2403 | * 2 - Enforce to use MLD version 2 | |
f2127810 | 2404 | |
b800c3b9 HFS |
2405 | suppress_frag_ndisc - INTEGER |
2406 | Control RFC 6980 (Security Implications of IPv6 Fragmentation | |
2407 | with IPv6 Neighbor Discovery) behavior: | |
1cec2cac MCC |
2408 | |
2409 | * 1 - (default) discard fragmented neighbor discovery packets | |
2410 | * 0 - allow fragmented neighbor discovery packets | |
b800c3b9 | 2411 | |
7fd2561e EK |
2412 | optimistic_dad - BOOLEAN |
2413 | Whether to perform Optimistic Duplicate Address Detection (RFC 4429). | |
1cec2cac MCC |
2414 | |
2415 | * 0: disabled (default) | |
2416 | * 1: enabled | |
35e015e1 MC |
2417 | |
2418 | Optimistic Duplicate Address Detection for the interface will be enabled | |
2419 | if at least one of conf/{all,interface}/optimistic_dad is set to 1, | |
2420 | it will be disabled otherwise. | |
7fd2561e EK |
2421 | |
2422 | use_optimistic - BOOLEAN | |
2423 | If enabled, do not classify optimistic addresses as deprecated during | |
2424 | source address selection. Preferred addresses will still be chosen | |
2425 | before optimistic addresses, subject to other ranking in the source | |
2426 | address selection algorithm. | |
1cec2cac MCC |
2427 | |
2428 | * 0: disabled (default) | |
2429 | * 1: enabled | |
35e015e1 MC |
2430 | |
2431 | This will be enabled if at least one of | |
2432 | conf/{all,interface}/use_optimistic is set to 1, disabled otherwise. | |
7fd2561e | 2433 | |
9f0761c1 HFS |
2434 | stable_secret - IPv6 address |
2435 | This IPv6 address will be used as a secret to generate IPv6 | |
2436 | addresses for link-local addresses and autoconfigured | |
2437 | ones. All addresses generated after setting this secret will | |
2438 | be stable privacy ones by default. This can be changed via the | |
2439 | addrgenmode ip-link. conf/default/stable_secret is used as the | |
2440 | secret for the namespace, the interface specific ones can | |
2441 | overwrite that. Writes to conf/all/stable_secret are refused. | |
2442 | ||
2443 | It is recommended to generate this secret during installation | |
2444 | of a system and keep it stable after that. | |
2445 | ||
2446 | By default the stable secret is unset. | |
2447 | ||
f168db5e SD |
2448 | addr_gen_mode - INTEGER |
2449 | Defines how link-local and autoconf addresses are generated. | |
2450 | ||
1cec2cac MCC |
2451 | = ================================================================= |
2452 | 0 generate address based on EUI64 (default) | |
2453 | 1 do no generate a link-local address, use EUI64 for addresses | |
2454 | generated from autoconf | |
2455 | 2 generate stable privacy addresses, using the secret from | |
f168db5e | 2456 | stable_secret (RFC7217) |
1cec2cac MCC |
2457 | 3 generate stable privacy addresses, using a random secret if unset |
2458 | = ================================================================= | |
f168db5e | 2459 | |
abbc3043 JB |
2460 | drop_unicast_in_l2_multicast - BOOLEAN |
2461 | Drop any unicast IPv6 packets that are received in link-layer | |
2462 | multicast (or broadcast) frames. | |
2463 | ||
2464 | By default this is turned off. | |
2465 | ||
7a02bf89 JB |
2466 | drop_unsolicited_na - BOOLEAN |
2467 | Drop all unsolicited neighbor advertisements, for example if there's | |
2468 | a known good NA proxy on the network and such frames need not be used | |
2469 | (or in the case of 802.11, must not be used to prevent attacks.) | |
2470 | ||
2471 | By default this is turned off. | |
2472 | ||
3e0b8f52 AA |
2473 | accept_untracked_na - BOOLEAN |
2474 | Add a new neighbour cache entry in STALE state for routers on receiving a | |
2475 | neighbour advertisement (either solicited or unsolicited) with target | |
2476 | link-layer address option specified if no neighbour entry is already | |
2477 | present for the advertised IPv6 address. Without this knob, NAs received | |
2478 | for untracked addresses (absent in neighbour cache) are silently ignored. | |
2479 | ||
2480 | This is as per router-side behaviour documented in RFC9131. | |
f9a2fb73 | 2481 | |
3e0b8f52 | 2482 | This has lower precedence than drop_unsolicited_na. |
f9a2fb73 AA |
2483 | |
2484 | This will optimize the return path for the initial off-link communication | |
2485 | that is initiated by a directly connected host, by ensuring that | |
2486 | the first-hop router which turns on this setting doesn't have to | |
2487 | buffer the initial return packets to do neighbour-solicitation. | |
2488 | The prerequisite is that the host is configured to send | |
2489 | unsolicited neighbour advertisements on interface bringup. | |
2490 | This setting should be used in conjunction with the ndisc_notify setting | |
2491 | on the host to satisfy this prerequisite. | |
2492 | ||
2493 | By default this is turned off. | |
2494 | ||
adc176c5 EN |
2495 | enhanced_dad - BOOLEAN |
2496 | Include a nonce option in the IPv6 neighbor solicitation messages used for | |
2497 | duplicate address detection per RFC7527. A received DAD NS will only signal | |
2498 | a duplicate address if the nonce is different. This avoids any false | |
2499 | detection of duplicates due to loopback of the NS messages that we send. | |
2500 | The nonce option will be sent on an interface unless both of | |
2501 | conf/{all,interface}/enhanced_dad are set to FALSE. | |
1cec2cac | 2502 | |
adc176c5 EN |
2503 | Default: TRUE |
2504 | ||
1cec2cac MCC |
2505 | ``icmp/*``: |
2506 | =========== | |
2507 | ||
1da177e4 | 2508 | ratelimit - INTEGER |
0bc19985 | 2509 | Limit the maximal rates for sending ICMPv6 messages. |
1cec2cac | 2510 | |
6dbf4bca SH |
2511 | 0 to disable any limiting, |
2512 | otherwise the minimal space between responses in milliseconds. | |
1cec2cac | 2513 | |
6dbf4bca | 2514 | Default: 1000 |
1da177e4 | 2515 | |
0bc19985 SS |
2516 | ratemask - list of comma separated ranges |
2517 | For ICMPv6 message types matching the ranges in the ratemask, limit | |
2518 | the sending of the message according to ratelimit parameter. | |
2519 | ||
2520 | The format used for both input and output is a comma separated | |
2521 | list of ranges (e.g. "0-127,129" for ICMPv6 message type 0 to 127 and | |
2522 | 129). Writing to the file will clear all previous ranges of ICMPv6 | |
2523 | message types and update the current list with the input. | |
2524 | ||
2525 | Refer to: https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml | |
2526 | for numerical values of ICMPv6 message types, e.g. echo request is 128 | |
2527 | and echo reply is 129. | |
2528 | ||
2529 | Default: 0-1,3-127 (rate limit ICMPv6 errors except Packet Too Big) | |
2530 | ||
e6f86b0f VJ |
2531 | echo_ignore_all - BOOLEAN |
2532 | If set non-zero, then the kernel will ignore all ICMP ECHO | |
2533 | requests sent to it over the IPv6 protocol. | |
1cec2cac | 2534 | |
e6f86b0f VJ |
2535 | Default: 0 |
2536 | ||
03f1eccc SS |
2537 | echo_ignore_multicast - BOOLEAN |
2538 | If set non-zero, then the kernel will ignore all ICMP ECHO | |
2539 | requests sent to it over the IPv6 protocol via multicast. | |
1cec2cac | 2540 | |
03f1eccc SS |
2541 | Default: 0 |
2542 | ||
0b03a5ca SS |
2543 | echo_ignore_anycast - BOOLEAN |
2544 | If set non-zero, then the kernel will ignore all ICMP ECHO | |
2545 | requests sent to it over the IPv6 protocol destined to anycast address. | |
1cec2cac | 2546 | |
0b03a5ca SS |
2547 | Default: 0 |
2548 | ||
e69948a0 | 2549 | xfrm6_gc_thresh - INTEGER |
837f7411 | 2550 | (Obsolete since linux-4.14) |
e69948a0 AD |
2551 | The threshold at which we will start garbage collecting for IPv6 |
2552 | destination cache entries. At twice this value the system will | |
3c2a89dd | 2553 | refuse new allocations. |
e69948a0 | 2554 | |
1da177e4 LT |
2555 | |
2556 | IPv6 Update by: | |
2557 | Pekka Savola <pekkas@netcore.fi> | |
2558 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
2559 | ||
2560 | ||
2561 | /proc/sys/net/bridge/* Variables: | |
1cec2cac | 2562 | ================================= |
1da177e4 LT |
2563 | |
2564 | bridge-nf-call-arptables - BOOLEAN | |
1cec2cac MCC |
2565 | - 1 : pass bridged ARP traffic to arptables' FORWARD chain. |
2566 | - 0 : disable this. | |
2567 | ||
1da177e4 LT |
2568 | Default: 1 |
2569 | ||
2570 | bridge-nf-call-iptables - BOOLEAN | |
1cec2cac MCC |
2571 | - 1 : pass bridged IPv4 traffic to iptables' chains. |
2572 | - 0 : disable this. | |
2573 | ||
1da177e4 LT |
2574 | Default: 1 |
2575 | ||
2576 | bridge-nf-call-ip6tables - BOOLEAN | |
1cec2cac MCC |
2577 | - 1 : pass bridged IPv6 traffic to ip6tables' chains. |
2578 | - 0 : disable this. | |
2579 | ||
1da177e4 LT |
2580 | Default: 1 |
2581 | ||
2582 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
1cec2cac MCC |
2583 | - 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
2584 | - 0 : disable this. | |
2585 | ||
4981682c | 2586 | Default: 0 |
516299d2 MM |
2587 | |
2588 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1cec2cac MCC |
2589 | - 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. |
2590 | - 0 : disable this. | |
2591 | ||
4981682c | 2592 | Default: 0 |
1da177e4 | 2593 | |
4981682c | 2594 | bridge-nf-pass-vlan-input-dev - BOOLEAN |
1cec2cac MCC |
2595 | - 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan |
2596 | interface on the bridge and set the netfilter input device to the | |
2597 | vlan. This allows use of e.g. "iptables -i br0.1" and makes the | |
2598 | REDIRECT target work with vlan-on-top-of-bridge interfaces. When no | |
2599 | matching vlan interface is found, or this switch is off, the input | |
2600 | device is set to the bridge interface. | |
2601 | ||
2602 | - 0: disable bridge netfilter vlan interface lookup. | |
2603 | ||
4981682c | 2604 | Default: 0 |
1da177e4 | 2605 | |
1cec2cac MCC |
2606 | ``proc/sys/net/sctp/*`` Variables: |
2607 | ================================== | |
32e8d494 VY |
2608 | |
2609 | addip_enable - BOOLEAN | |
2610 | Enable or disable extension of Dynamic Address Reconfiguration | |
2611 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
2612 | the ability to dynamically add and remove new addresses for the SCTP | |
2613 | associations. | |
2614 | ||
2615 | 1: Enable extension. | |
2616 | ||
2617 | 0: Disable extension. | |
2618 | ||
2619 | Default: 0 | |
2620 | ||
566178f8 ZY |
2621 | pf_enable - INTEGER |
2622 | Enable or disable pf (pf is short for potentially failed) state. A value | |
2623 | of pf_retrans > path_max_retrans also disables pf state. That is, one of | |
2624 | both pf_enable and pf_retrans > path_max_retrans can disable pf state. | |
2625 | Since pf_retrans and path_max_retrans can be changed by userspace | |
2626 | application, sometimes user expects to disable pf state by the value of | |
2627 | pf_retrans > path_max_retrans, but occasionally the value of pf_retrans | |
2628 | or path_max_retrans is changed by the user application, this pf state is | |
2629 | enabled. As such, it is necessary to add this to dynamically enable | |
2630 | and disable pf state. See: | |
2631 | https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for | |
2632 | details. | |
2633 | ||
2634 | 1: Enable pf. | |
2635 | ||
2636 | 0: Disable pf. | |
2637 | ||
2638 | Default: 1 | |
2639 | ||
aef587be XL |
2640 | pf_expose - INTEGER |
2641 | Unset or enable/disable pf (pf is short for potentially failed) state | |
2642 | exposure. Applications can control the exposure of the PF path state | |
2643 | in the SCTP_PEER_ADDR_CHANGE event and the SCTP_GET_PEER_ADDR_INFO | |
2644 | sockopt. When it's unset, no SCTP_PEER_ADDR_CHANGE event with | |
2645 | SCTP_ADDR_PF state will be sent and a SCTP_PF-state transport info | |
2646 | can be got via SCTP_GET_PEER_ADDR_INFO sockopt; When it's enabled, | |
2647 | a SCTP_PEER_ADDR_CHANGE event will be sent for a transport becoming | |
2648 | SCTP_PF state and a SCTP_PF-state transport info can be got via | |
2649 | SCTP_GET_PEER_ADDR_INFO sockopt; When it's diabled, no | |
2650 | SCTP_PEER_ADDR_CHANGE event will be sent and it returns -EACCES when | |
2651 | trying to get a SCTP_PF-state transport info via SCTP_GET_PEER_ADDR_INFO | |
2652 | sockopt. | |
2653 | ||
2654 | 0: Unset pf state exposure, Compatible with old applications. | |
2655 | ||
2656 | 1: Disable pf state exposure. | |
2657 | ||
2658 | 2: Enable pf state exposure. | |
2659 | ||
2660 | Default: 0 | |
2661 | ||
32e8d494 VY |
2662 | addip_noauth_enable - BOOLEAN |
2663 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
2664 | authentication to protect the operations of adding or removing new | |
2665 | addresses. This requirement is mandated so that unauthorized hosts | |
2666 | would not be able to hijack associations. However, older | |
2667 | implementations may not have implemented this requirement while | |
2668 | allowing the ADD-IP extension. For reasons of interoperability, | |
2669 | we provide this variable to control the enforcement of the | |
2670 | authentication requirement. | |
2671 | ||
1cec2cac MCC |
2672 | == =============================================================== |
2673 | 1 Allow ADD-IP extension to be used without authentication. This | |
32e8d494 VY |
2674 | should only be set in a closed environment for interoperability |
2675 | with older implementations. | |
2676 | ||
1cec2cac MCC |
2677 | 0 Enforce the authentication requirement |
2678 | == =============================================================== | |
32e8d494 VY |
2679 | |
2680 | Default: 0 | |
2681 | ||
2682 | auth_enable - BOOLEAN | |
2683 | Enable or disable Authenticated Chunks extension. This extension | |
2684 | provides the ability to send and receive authenticated chunks and is | |
2685 | required for secure operation of Dynamic Address Reconfiguration | |
2686 | (ADD-IP) extension. | |
2687 | ||
1cec2cac MCC |
2688 | - 1: Enable this extension. |
2689 | - 0: Disable this extension. | |
32e8d494 VY |
2690 | |
2691 | Default: 0 | |
2692 | ||
2693 | prsctp_enable - BOOLEAN | |
2694 | Enable or disable the Partial Reliability extension (RFC3758) which | |
2695 | is used to notify peers that a given DATA should no longer be expected. | |
2696 | ||
1cec2cac MCC |
2697 | - 1: Enable extension |
2698 | - 0: Disable | |
32e8d494 VY |
2699 | |
2700 | Default: 1 | |
2701 | ||
2702 | max_burst - INTEGER | |
2703 | The limit of the number of new packets that can be initially sent. It | |
2704 | controls how bursty the generated traffic can be. | |
2705 | ||
2706 | Default: 4 | |
2707 | ||
2708 | association_max_retrans - INTEGER | |
2709 | Set the maximum number for retransmissions that an association can | |
2710 | attempt deciding that the remote end is unreachable. If this value | |
2711 | is exceeded, the association is terminated. | |
2712 | ||
2713 | Default: 10 | |
2714 | ||
2715 | max_init_retransmits - INTEGER | |
2716 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
2717 | that an association will attempt before declaring the destination | |
2718 | unreachable and terminating. | |
2719 | ||
2720 | Default: 8 | |
2721 | ||
2722 | path_max_retrans - INTEGER | |
2723 | The maximum number of retransmissions that will be attempted on a given | |
2724 | path. Once this threshold is exceeded, the path is considered | |
2725 | unreachable, and new traffic will use a different path when the | |
2726 | association is multihomed. | |
2727 | ||
2728 | Default: 5 | |
2729 | ||
5aa93bcf NH |
2730 | pf_retrans - INTEGER |
2731 | The number of retransmissions that will be attempted on a given path | |
2732 | before traffic is redirected to an alternate transport (should one | |
2733 | exist). Note this is distinct from path_max_retrans, as a path that | |
2734 | passes the pf_retrans threshold can still be used. Its only | |
2735 | deprioritized when a transmission path is selected by the stack. This | |
2736 | setting is primarily used to enable fast failover mechanisms without | |
2737 | having to reduce path_max_retrans to a very low value. See: | |
2738 | http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt | |
2739 | for details. Note also that a value of pf_retrans > path_max_retrans | |
566178f8 ZY |
2740 | disables this feature. Since both pf_retrans and path_max_retrans can |
2741 | be changed by userspace application, a variable pf_enable is used to | |
2742 | disable pf state. | |
5aa93bcf NH |
2743 | |
2744 | Default: 0 | |
2745 | ||
34515e94 XL |
2746 | ps_retrans - INTEGER |
2747 | Primary.Switchover.Max.Retrans (PSMR), it's a tunable parameter coming | |
2748 | from section-5 "Primary Path Switchover" in rfc7829. The primary path | |
2749 | will be changed to another active path when the path error counter on | |
2750 | the old primary path exceeds PSMR, so that "the SCTP sender is allowed | |
2751 | to continue data transmission on a new working path even when the old | |
2752 | primary destination address becomes active again". Note this feature | |
2753 | is disabled by initializing 'ps_retrans' per netns as 0xffff by default, | |
2754 | and its value can't be less than 'pf_retrans' when changing by sysctl. | |
2755 | ||
2756 | Default: 0xffff | |
2757 | ||
32e8d494 VY |
2758 | rto_initial - INTEGER |
2759 | The initial round trip timeout value in milliseconds that will be used | |
2760 | in calculating round trip times. This is the initial time interval | |
2761 | for retransmissions. | |
2762 | ||
2763 | Default: 3000 | |
1da177e4 | 2764 | |
32e8d494 VY |
2765 | rto_max - INTEGER |
2766 | The maximum value (in milliseconds) of the round trip timeout. This | |
2767 | is the largest time interval that can elapse between retransmissions. | |
2768 | ||
2769 | Default: 60000 | |
2770 | ||
2771 | rto_min - INTEGER | |
2772 | The minimum value (in milliseconds) of the round trip timeout. This | |
2773 | is the smallest time interval the can elapse between retransmissions. | |
2774 | ||
2775 | Default: 1000 | |
2776 | ||
2777 | hb_interval - INTEGER | |
2778 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
2779 | are sent at the specified interval on idle paths to probe the state of | |
2780 | a given path between 2 associations. | |
2781 | ||
2782 | Default: 30000 | |
2783 | ||
2784 | sack_timeout - INTEGER | |
2785 | The amount of time (in milliseconds) that the implementation will wait | |
2786 | to send a SACK. | |
2787 | ||
2788 | Default: 200 | |
2789 | ||
2790 | valid_cookie_life - INTEGER | |
2791 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
2792 | is used during association establishment. | |
2793 | ||
2794 | Default: 60000 | |
2795 | ||
2796 | cookie_preserve_enable - BOOLEAN | |
2797 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
2798 | that is used during the establishment phase of SCTP association | |
2799 | ||
1cec2cac MCC |
2800 | - 1: Enable cookie lifetime extension. |
2801 | - 0: Disable | |
32e8d494 VY |
2802 | |
2803 | Default: 1 | |
2804 | ||
3c68198e NH |
2805 | cookie_hmac_alg - STRING |
2806 | Select the hmac algorithm used when generating the cookie value sent by | |
2807 | a listening sctp socket to a connecting client in the INIT-ACK chunk. | |
2808 | Valid values are: | |
1cec2cac | 2809 | |
3c68198e NH |
2810 | * md5 |
2811 | * sha1 | |
2812 | * none | |
1cec2cac | 2813 | |
3c68198e | 2814 | Ability to assign md5 or sha1 as the selected alg is predicated on the |
3b09adcb | 2815 | configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and |
3c68198e NH |
2816 | CONFIG_CRYPTO_SHA1). |
2817 | ||
2818 | Default: Dependent on configuration. MD5 if available, else SHA1 if | |
2819 | available, else none. | |
2820 | ||
32e8d494 VY |
2821 | rcvbuf_policy - INTEGER |
2822 | Determines if the receive buffer is attributed to the socket or to | |
2823 | association. SCTP supports the capability to create multiple | |
2824 | associations on a single socket. When using this capability, it is | |
2825 | possible that a single stalled association that's buffering a lot | |
2826 | of data may block other associations from delivering their data by | |
2827 | consuming all of the receive buffer space. To work around this, | |
2828 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
2829 | to each association instead of the socket. This prevents the described | |
2830 | blocking. | |
2831 | ||
1cec2cac MCC |
2832 | - 1: rcvbuf space is per association |
2833 | - 0: rcvbuf space is per socket | |
32e8d494 VY |
2834 | |
2835 | Default: 0 | |
2836 | ||
2837 | sndbuf_policy - INTEGER | |
2838 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
2839 | ||
1cec2cac MCC |
2840 | - 1: Send buffer is tracked per association |
2841 | - 0: Send buffer is tracked per socket. | |
32e8d494 VY |
2842 | |
2843 | Default: 0 | |
2844 | ||
2845 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
2846 | Number of pages allowed for queueing by all SCTP sockets. | |
2847 | ||
2848 | min: Below this number of pages SCTP is not bothered about its | |
2849 | memory appetite. When amount of memory allocated by SCTP exceeds | |
2850 | this number, SCTP starts to moderate memory usage. | |
2851 | ||
2852 | pressure: This value was introduced to follow format of tcp_mem. | |
2853 | ||
2854 | max: Number of pages allowed for queueing by all SCTP sockets. | |
2855 | ||
2856 | Default is calculated at boot time from amount of available memory. | |
2857 | ||
2858 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b MM |
2859 | Only the first value ("min") is used, "default" and "max" are |
2860 | ignored. | |
2861 | ||
2862 | min: Minimal size of receive buffer used by SCTP socket. | |
2863 | It is guaranteed to each SCTP socket (but not association) even | |
2864 | under moderate memory pressure. | |
2865 | ||
320bd6de | 2866 | Default: 4K |
32e8d494 VY |
2867 | |
2868 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
aa709da0 XL |
2869 | Only the first value ("min") is used, "default" and "max" are |
2870 | ignored. | |
2871 | ||
2872 | min: Minimum size of send buffer that can be used by SCTP sockets. | |
2873 | It is guaranteed to each SCTP socket (but not association) even | |
2874 | under moderate memory pressure. | |
2875 | ||
2876 | Default: 4K | |
32e8d494 | 2877 | |
72388433 BD |
2878 | addr_scope_policy - INTEGER |
2879 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 | |
2880 | ||
1cec2cac MCC |
2881 | - 0 - Disable IPv4 address scoping |
2882 | - 1 - Enable IPv4 address scoping | |
2883 | - 2 - Follow draft but allow IPv4 private addresses | |
2884 | - 3 - Follow draft but allow IPv4 link local addresses | |
72388433 BD |
2885 | |
2886 | Default: 1 | |
2887 | ||
046c052b XL |
2888 | udp_port - INTEGER |
2889 | The listening port for the local UDP tunneling sock. Normally it's | |
2890 | using the IANA-assigned UDP port number 9899 (sctp-tunneling). | |
2891 | ||
2892 | This UDP sock is used for processing the incoming UDP-encapsulated | |
2893 | SCTP packets (from RFC6951), and shared by all applications in the | |
2894 | same net namespace. This UDP sock will be closed when the value is | |
2895 | set to 0. | |
2896 | ||
2897 | The value will also be used to set the src port of the UDP header | |
2898 | for the outgoing UDP-encapsulated SCTP packets. For the dest port, | |
2899 | please refer to 'encap_port' below. | |
2900 | ||
2901 | Default: 0 | |
2902 | ||
e8a3001c XL |
2903 | encap_port - INTEGER |
2904 | The default remote UDP encapsulation port. | |
2905 | ||
2906 | This value is used to set the dest port of the UDP header for the | |
2907 | outgoing UDP-encapsulated SCTP packets by default. Users can also | |
2908 | change the value for each sock/asoc/transport by using setsockopt. | |
2909 | For further information, please refer to RFC6951. | |
2910 | ||
2911 | Note that when connecting to a remote server, the client should set | |
2912 | this to the port that the UDP tunneling sock on the peer server is | |
2913 | listening to and the local UDP tunneling sock on the client also | |
2914 | must be started. On the server, it would get the encap_port from | |
2915 | the incoming packet's source port. | |
2916 | ||
2917 | Default: 0 | |
2918 | ||
d1e462a7 | 2919 | plpmtud_probe_interval - INTEGER |
fea1d5b1 XL |
2920 | The time interval (in milliseconds) for the PLPMTUD probe timer, |
2921 | which is configured to expire after this period to receive an | |
2922 | acknowledgment to a probe packet. This is also the time interval | |
2923 | between the probes for the current pmtu when the probe search | |
2924 | is done. | |
2925 | ||
2926 | PLPMTUD will be disabled when 0 is set, and other values for it | |
2927 | must be >= 5000. | |
d1e462a7 XL |
2928 | |
2929 | Default: 0 | |
2930 | ||
c349ae5f XL |
2931 | reconf_enable - BOOLEAN |
2932 | Enable or disable extension of Stream Reconfiguration functionality | |
2933 | specified in RFC6525. This extension provides the ability to "reset" | |
2934 | a stream, and it includes the Parameters of "Outgoing/Incoming SSN | |
2935 | Reset", "SSN/TSN Reset" and "Add Outgoing/Incoming Streams". | |
2936 | ||
2937 | - 1: Enable extension. | |
2938 | - 0: Disable extension. | |
2939 | ||
2940 | Default: 0 | |
2941 | ||
e65775fd XL |
2942 | intl_enable - BOOLEAN |
2943 | Enable or disable extension of User Message Interleaving functionality | |
2944 | specified in RFC8260. This extension allows the interleaving of user | |
2945 | messages sent on different streams. With this feature enabled, I-DATA | |
2946 | chunk will replace DATA chunk to carry user messages if also supported | |
2947 | by the peer. Note that to use this feature, one needs to set this option | |
2948 | to 1 and also needs to set socket options SCTP_FRAGMENT_INTERLEAVE to 2 | |
2949 | and SCTP_INTERLEAVING_SUPPORTED to 1. | |
2950 | ||
2951 | - 1: Enable extension. | |
2952 | - 0: Disable extension. | |
2953 | ||
2954 | Default: 0 | |
2955 | ||
249eddaf XL |
2956 | ecn_enable - BOOLEAN |
2957 | Control use of Explicit Congestion Notification (ECN) by SCTP. | |
2958 | Like in TCP, ECN is used only when both ends of the SCTP connection | |
2959 | indicate support for it. This feature is useful in avoiding losses | |
2960 | due to congestion by allowing supporting routers to signal congestion | |
2961 | before having to drop packets. | |
2962 | ||
2963 | 1: Enable ecn. | |
2964 | 0: Disable ecn. | |
2965 | ||
2966 | Default: 1 | |
2967 | ||
1da177e4 | 2968 | |
1cec2cac MCC |
2969 | ``/proc/sys/net/core/*`` |
2970 | ======================== | |
2971 | ||
57043247 | 2972 | Please see: Documentation/admin-guide/sysctl/net.rst for descriptions of these entries. |
705efc3b | 2973 | |
4edc2f34 | 2974 | |
1cec2cac MCC |
2975 | ``/proc/sys/net/unix/*`` |
2976 | ======================== | |
2977 | ||
705efc3b WT |
2978 | max_dgram_qlen - INTEGER |
2979 | The maximum length of dgram socket receive queue | |
2980 | ||
2981 | Default: 10 | |
2982 |