Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /proc/sys/net/ipv4/* Variables: |
2 | ||
3 | ip_forward - BOOLEAN | |
4 | 0 - disabled (default) | |
e18f5feb | 5 | not 0 - enabled |
1da177e4 LT |
6 | |
7 | Forward Packets between interfaces. | |
8 | ||
9 | This variable is special, its change resets all configuration | |
10 | parameters to their default state (RFC1122 for hosts, RFC1812 | |
11 | for routers) | |
12 | ||
13 | ip_default_ttl - INTEGER | |
cc6f02dd ED |
14 | Default value of TTL field (Time To Live) for outgoing (but not |
15 | forwarded) IP packets. Should be between 1 and 255 inclusive. | |
16 | Default: 64 (as recommended by RFC1700) | |
1da177e4 | 17 | |
cd174e67 HFS |
18 | ip_no_pmtu_disc - INTEGER |
19 | Disable Path MTU Discovery. If enabled in mode 1 and a | |
188b04d5 HFS |
20 | fragmentation-required ICMP is received, the PMTU to this |
21 | destination will be set to min_pmtu (see below). You will need | |
22 | to raise min_pmtu to the smallest interface MTU on your system | |
23 | manually if you want to avoid locally generated fragments. | |
cd174e67 HFS |
24 | |
25 | In mode 2 incoming Path MTU Discovery messages will be | |
26 | discarded. Outgoing frames are handled the same as in mode 1, | |
27 | implicitly setting IP_PMTUDISC_DONT on every created socket. | |
28 | ||
bb38ccce | 29 | Mode 3 is a hardened pmtu discover mode. The kernel will only |
8ed1dc44 HFS |
30 | accept fragmentation-needed errors if the underlying protocol |
31 | can verify them besides a plain socket lookup. Current | |
32 | protocols for which pmtu events will be honored are TCP, SCTP | |
33 | and DCCP as they verify e.g. the sequence number or the | |
34 | association. This mode should not be enabled globally but is | |
35 | only intended to secure e.g. name servers in namespaces where | |
36 | TCP path mtu must still work but path MTU information of other | |
37 | protocols should be discarded. If enabled globally this mode | |
38 | could break other protocols. | |
39 | ||
40 | Possible values: 0-3 | |
188b04d5 | 41 | Default: FALSE |
1da177e4 LT |
42 | |
43 | min_pmtu - INTEGER | |
20db93c3 | 44 | default 552 - minimum discovered Path MTU |
1da177e4 | 45 | |
f87c10a8 HFS |
46 | ip_forward_use_pmtu - BOOLEAN |
47 | By default we don't trust protocol path MTUs while forwarding | |
48 | because they could be easily forged and can lead to unwanted | |
49 | fragmentation by the router. | |
50 | You only need to enable this if you have user-space software | |
51 | which tries to discover path mtus by itself and depends on the | |
52 | kernel honoring this information. This is normally not the | |
53 | case. | |
54 | Default: 0 (disabled) | |
55 | Possible values: | |
56 | 0 - disabled | |
57 | 1 - enabled | |
58 | ||
219b5f29 LV |
59 | fwmark_reflect - BOOLEAN |
60 | Controls the fwmark of kernel-generated IPv4 reply packets that are not | |
61 | associated with a socket for example, TCP RSTs or ICMP echo replies). | |
62 | If unset, these packets have a fwmark of zero. If set, they have the | |
63 | fwmark of the packet they are replying to. | |
64 | Default: 0 | |
65 | ||
a6db4494 DA |
66 | fib_multipath_use_neigh - BOOLEAN |
67 | Use status of existing neighbor entry when determining nexthop for | |
68 | multipath routes. If disabled, neighbor information is not used and | |
69 | packets could be directed to a failed nexthop. Only valid for kernels | |
70 | built with CONFIG_IP_ROUTE_MULTIPATH enabled. | |
71 | Default: 0 (disabled) | |
72 | Possible values: | |
73 | 0 - disabled | |
74 | 1 - enabled | |
75 | ||
bf4e0a3d NA |
76 | fib_multipath_hash_policy - INTEGER |
77 | Controls which hash policy to use for multipath routes. Only valid | |
78 | for kernels built with CONFIG_IP_ROUTE_MULTIPATH enabled. | |
79 | Default: 0 (Layer 3) | |
80 | Possible values: | |
81 | 0 - Layer 3 | |
82 | 1 - Layer 4 | |
83 | ||
432e05d3 PM |
84 | ip_forward_update_priority - INTEGER |
85 | Whether to update SKB priority from "TOS" field in IPv4 header after it | |
86 | is forwarded. The new SKB priority is mapped from TOS field value | |
87 | according to an rt_tos2priority table (see e.g. man tc-prio). | |
88 | Default: 1 (Update priority.) | |
89 | Possible values: | |
90 | 0 - Do not update priority. | |
91 | 1 - Update priority. | |
92 | ||
cbaf087a BG |
93 | route/max_size - INTEGER |
94 | Maximum number of routes allowed in the kernel. Increase | |
95 | this when using large numbers of interfaces and/or routes. | |
25050c63 AS |
96 | From linux kernel 3.6 onwards, this is deprecated for ipv4 |
97 | as route cache is no longer used. | |
cbaf087a | 98 | |
2724680b YH |
99 | neigh/default/gc_thresh1 - INTEGER |
100 | Minimum number of entries to keep. Garbage collector will not | |
101 | purge entries if there are fewer than this number. | |
b66c66dc | 102 | Default: 128 |
2724680b | 103 | |
a3d12146 | 104 | neigh/default/gc_thresh2 - INTEGER |
105 | Threshold when garbage collector becomes more aggressive about | |
106 | purging entries. Entries older than 5 seconds will be cleared | |
107 | when over this number. | |
108 | Default: 512 | |
109 | ||
cbaf087a BG |
110 | neigh/default/gc_thresh3 - INTEGER |
111 | Maximum number of neighbor entries allowed. Increase this | |
112 | when using large numbers of interfaces and when communicating | |
113 | with large numbers of directly-connected peers. | |
cc868028 | 114 | Default: 1024 |
cbaf087a | 115 | |
8b5c171b ED |
116 | neigh/default/unres_qlen_bytes - INTEGER |
117 | The maximum number of bytes which may be used by packets | |
118 | queued for each unresolved address by other network layers. | |
119 | (added in linux 3.3) | |
3b09adcb | 120 | Setting negative value is meaningless and will return error. |
eaa72dc4 ED |
121 | Default: SK_WMEM_MAX, (same as net.core.wmem_default). |
122 | Exact value depends on architecture and kernel options, | |
123 | but should be enough to allow queuing 256 packets | |
124 | of medium size. | |
8b5c171b ED |
125 | |
126 | neigh/default/unres_qlen - INTEGER | |
127 | The maximum number of packets which may be queued for each | |
128 | unresolved address by other network layers. | |
129 | (deprecated in linux 3.3) : use unres_qlen_bytes instead. | |
cc868028 | 130 | Prior to linux 3.3, the default value is 3 which may cause |
5d248c49 | 131 | unexpected packet loss. The current default value is calculated |
cc868028 SW |
132 | according to default value of unres_qlen_bytes and true size of |
133 | packet. | |
eaa72dc4 | 134 | Default: 101 |
8b5c171b | 135 | |
1da177e4 LT |
136 | mtu_expires - INTEGER |
137 | Time, in seconds, that cached PMTU information is kept. | |
138 | ||
139 | min_adv_mss - INTEGER | |
140 | The advertised MSS depends on the first hop route MTU, but will | |
141 | never be lower than this setting. | |
142 | ||
143 | IP Fragmentation: | |
144 | ||
3e67f106 | 145 | ipfrag_high_thresh - LONG INTEGER |
648700f7 | 146 | Maximum memory used to reassemble IP fragments. |
e18f5feb | 147 | |
3e67f106 | 148 | ipfrag_low_thresh - LONG INTEGER |
648700f7 | 149 | (Obsolete since linux-4.17) |
b13d3cbf FW |
150 | Maximum memory used to reassemble IP fragments before the kernel |
151 | begins to remove incomplete fragment queues to free up resources. | |
152 | The kernel still accepts new fragments for defragmentation. | |
1da177e4 LT |
153 | |
154 | ipfrag_time - INTEGER | |
e18f5feb | 155 | Time in seconds to keep an IP fragment in memory. |
1da177e4 | 156 | |
89cee8b1 | 157 | ipfrag_max_dist - INTEGER |
e18f5feb JDB |
158 | ipfrag_max_dist is a non-negative integer value which defines the |
159 | maximum "disorder" which is allowed among fragments which share a | |
160 | common IP source address. Note that reordering of packets is | |
161 | not unusual, but if a large number of fragments arrive from a source | |
162 | IP address while a particular fragment queue remains incomplete, it | |
163 | probably indicates that one or more fragments belonging to that queue | |
164 | have been lost. When ipfrag_max_dist is positive, an additional check | |
165 | is done on fragments before they are added to a reassembly queue - if | |
166 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
167 | address between additions to any IP fragment queue using that source | |
168 | address, it's presumed that one or more fragments in the queue are | |
169 | lost. The existing fragment queue will be dropped, and a new one | |
89cee8b1 HX |
170 | started. An ipfrag_max_dist value of zero disables this check. |
171 | ||
172 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
173 | result in unnecessarily dropping fragment queues when normal | |
e18f5feb JDB |
174 | reordering of packets occurs, which could lead to poor application |
175 | performance. Using a very large value, e.g. 50000, increases the | |
176 | likelihood of incorrectly reassembling IP fragments that originate | |
89cee8b1 HX |
177 | from different IP datagrams, which could result in data corruption. |
178 | Default: 64 | |
179 | ||
1da177e4 LT |
180 | INET peer storage: |
181 | ||
182 | inet_peer_threshold - INTEGER | |
e18f5feb | 183 | The approximate size of the storage. Starting from this threshold |
1da177e4 LT |
184 | entries will be thrown aggressively. This threshold also determines |
185 | entries' time-to-live and time intervals between garbage collection | |
186 | passes. More entries, less time-to-live, less GC interval. | |
187 | ||
188 | inet_peer_minttl - INTEGER | |
189 | Minimum time-to-live of entries. Should be enough to cover fragment | |
190 | time-to-live on the reassembling side. This minimum time-to-live is | |
191 | guaranteed if the pool size is less than inet_peer_threshold. | |
77a538d5 | 192 | Measured in seconds. |
1da177e4 LT |
193 | |
194 | inet_peer_maxttl - INTEGER | |
195 | Maximum time-to-live of entries. Unused entries will expire after | |
196 | this period of time if there is no memory pressure on the pool (i.e. | |
197 | when the number of entries in the pool is very small). | |
77a538d5 | 198 | Measured in seconds. |
1da177e4 | 199 | |
e18f5feb | 200 | TCP variables: |
1da177e4 | 201 | |
ef56e622 SH |
202 | somaxconn - INTEGER |
203 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
204 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
205 | for TCP sockets. | |
206 | ||
ef56e622 SH |
207 | tcp_abort_on_overflow - BOOLEAN |
208 | If listening service is too slow to accept new connections, | |
209 | reset them. Default state is FALSE. It means that if overflow | |
210 | occurred due to a burst, connection will recover. Enable this | |
211 | option _only_ if you are really sure that listening daemon | |
212 | cannot be tuned to accept connections faster. Enabling this | |
213 | option can harm clients of your server. | |
1da177e4 | 214 | |
ef56e622 SH |
215 | tcp_adv_win_scale - INTEGER |
216 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
217 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
218 | if it is <= 0. | |
0147fc05 | 219 | Possible values are [-31, 31], inclusive. |
b49960a0 | 220 | Default: 1 |
1da177e4 | 221 | |
ef56e622 SH |
222 | tcp_allowed_congestion_control - STRING |
223 | Show/set the congestion control choices available to non-privileged | |
224 | processes. The list is a subset of those listed in | |
225 | tcp_available_congestion_control. | |
226 | Default is "reno" and the default setting (tcp_congestion_control). | |
1da177e4 | 227 | |
ef56e622 SH |
228 | tcp_app_win - INTEGER |
229 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
230 | buffer. Value 0 is special, it means that nothing is reserved. | |
231 | Default: 31 | |
1da177e4 | 232 | |
f54b3111 ED |
233 | tcp_autocorking - BOOLEAN |
234 | Enable TCP auto corking : | |
235 | When applications do consecutive small write()/sendmsg() system calls, | |
236 | we try to coalesce these small writes as much as possible, to lower | |
237 | total amount of sent packets. This is done if at least one prior | |
238 | packet for the flow is waiting in Qdisc queues or device transmit | |
239 | queue. Applications can still use TCP_CORK for optimal behavior | |
240 | when they know how/when to uncork their sockets. | |
241 | Default : 1 | |
242 | ||
ef56e622 SH |
243 | tcp_available_congestion_control - STRING |
244 | Shows the available congestion control choices that are registered. | |
245 | More congestion control algorithms may be available as modules, | |
246 | but not loaded. | |
1da177e4 | 247 | |
71599cd1 | 248 | tcp_base_mss - INTEGER |
4edc2f34 SH |
249 | The initial value of search_low to be used by the packetization layer |
250 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
251 | this is the initial MSS used by the connection. | |
71599cd1 | 252 | |
ef56e622 SH |
253 | tcp_congestion_control - STRING |
254 | Set the congestion control algorithm to be used for new | |
255 | connections. The algorithm "reno" is always available, but | |
256 | additional choices may be available based on kernel configuration. | |
257 | Default is set as part of kernel configuration. | |
d8a6e65f ED |
258 | For passive connections, the listener congestion control choice |
259 | is inherited. | |
260 | [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] | |
1da177e4 | 261 | |
ef56e622 SH |
262 | tcp_dsack - BOOLEAN |
263 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 264 | |
eed530b6 | 265 | tcp_early_retrans - INTEGER |
bec41a11 YC |
266 | Tail loss probe (TLP) converts RTOs occurring due to tail |
267 | losses into fast recovery (draft-ietf-tcpm-rack). Note that | |
268 | TLP requires RACK to function properly (see tcp_recovery below) | |
eed530b6 | 269 | Possible values: |
bec41a11 YC |
270 | 0 disables TLP |
271 | 3 or 4 enables TLP | |
6ba8a3b1 | 272 | Default: 3 |
eed530b6 | 273 | |
34a6ef38 | 274 | tcp_ecn - INTEGER |
7e3a2dc5 RJ |
275 | Control use of Explicit Congestion Notification (ECN) by TCP. |
276 | ECN is used only when both ends of the TCP connection indicate | |
277 | support for it. This feature is useful in avoiding losses due | |
278 | to congestion by allowing supporting routers to signal | |
279 | congestion before having to drop packets. | |
255cac91 | 280 | Possible values are: |
7e3a2dc5 | 281 | 0 Disable ECN. Neither initiate nor accept ECN. |
3d55b323 VS |
282 | 1 Enable ECN when requested by incoming connections and |
283 | also request ECN on outgoing connection attempts. | |
284 | 2 Enable ECN when requested by incoming connections | |
7e3a2dc5 | 285 | but do not request ECN on outgoing connections. |
255cac91 | 286 | Default: 2 |
ef56e622 | 287 | |
49213555 DB |
288 | tcp_ecn_fallback - BOOLEAN |
289 | If the kernel detects that ECN connection misbehaves, enable fall | |
290 | back to non-ECN. Currently, this knob implements the fallback | |
291 | from RFC3168, section 6.1.1.1., but we reserve that in future, | |
292 | additional detection mechanisms could be implemented under this | |
293 | knob. The value is not used, if tcp_ecn or per route (or congestion | |
294 | control) ECN settings are disabled. | |
295 | Default: 1 (fallback enabled) | |
296 | ||
ef56e622 | 297 | tcp_fack - BOOLEAN |
713bafea | 298 | This is a legacy option, it has no effect anymore. |
1da177e4 LT |
299 | |
300 | tcp_fin_timeout - INTEGER | |
d825da2e RJ |
301 | The length of time an orphaned (no longer referenced by any |
302 | application) connection will remain in the FIN_WAIT_2 state | |
303 | before it is aborted at the local end. While a perfectly | |
304 | valid "receive only" state for an un-orphaned connection, an | |
305 | orphaned connection in FIN_WAIT_2 state could otherwise wait | |
306 | forever for the remote to close its end of the connection. | |
307 | Cf. tcp_max_orphans | |
308 | Default: 60 seconds | |
1da177e4 | 309 | |
89808060 | 310 | tcp_frto - INTEGER |
e33099f9 | 311 | Enables Forward RTO-Recovery (F-RTO) defined in RFC5682. |
cd99889c | 312 | F-RTO is an enhanced recovery algorithm for TCP retransmission |
e33099f9 YC |
313 | timeouts. It is particularly beneficial in networks where the |
314 | RTT fluctuates (e.g., wireless). F-RTO is sender-side only | |
315 | modification. It does not require any support from the peer. | |
316 | ||
317 | By default it's enabled with a non-zero value. 0 disables F-RTO. | |
1da177e4 | 318 | |
e2d00e62 LC |
319 | tcp_fwmark_accept - BOOLEAN |
320 | If set, incoming connections to listening sockets that do not have a | |
321 | socket mark will set the mark of the accepting socket to the fwmark of | |
322 | the incoming SYN packet. This will cause all packets on that connection | |
323 | (starting from the first SYNACK) to be sent with that fwmark. The | |
324 | listening socket's mark is unchanged. Listening sockets that already | |
325 | have a fwmark set via setsockopt(SOL_SOCKET, SO_MARK, ...) are | |
326 | unaffected. | |
327 | ||
328 | Default: 0 | |
329 | ||
032ee423 NC |
330 | tcp_invalid_ratelimit - INTEGER |
331 | Limit the maximal rate for sending duplicate acknowledgments | |
332 | in response to incoming TCP packets that are for an existing | |
333 | connection but that are invalid due to any of these reasons: | |
334 | ||
335 | (a) out-of-window sequence number, | |
336 | (b) out-of-window acknowledgment number, or | |
337 | (c) PAWS (Protection Against Wrapped Sequence numbers) check failure | |
338 | ||
339 | This can help mitigate simple "ack loop" DoS attacks, wherein | |
340 | a buggy or malicious middlebox or man-in-the-middle can | |
341 | rewrite TCP header fields in manner that causes each endpoint | |
342 | to think that the other is sending invalid TCP segments, thus | |
343 | causing each side to send an unterminating stream of duplicate | |
344 | acknowledgments for invalid segments. | |
345 | ||
346 | Using 0 disables rate-limiting of dupacks in response to | |
347 | invalid segments; otherwise this value specifies the minimal | |
348 | space between sending such dupacks, in milliseconds. | |
349 | ||
350 | Default: 500 (milliseconds). | |
351 | ||
ef56e622 SH |
352 | tcp_keepalive_time - INTEGER |
353 | How often TCP sends out keepalive messages when keepalive is enabled. | |
354 | Default: 2hours. | |
1da177e4 | 355 | |
ef56e622 SH |
356 | tcp_keepalive_probes - INTEGER |
357 | How many keepalive probes TCP sends out, until it decides that the | |
358 | connection is broken. Default value: 9. | |
359 | ||
360 | tcp_keepalive_intvl - INTEGER | |
361 | How frequently the probes are send out. Multiplied by | |
362 | tcp_keepalive_probes it is time to kill not responding connection, | |
363 | after probes started. Default value: 75sec i.e. connection | |
364 | will be aborted after ~11 minutes of retries. | |
365 | ||
6dd9a14e DA |
366 | tcp_l3mdev_accept - BOOLEAN |
367 | Enables child sockets to inherit the L3 master device index. | |
368 | Enabling this option allows a "global" listen socket to work | |
369 | across L3 master domains (e.g., VRFs) with connected sockets | |
370 | derived from the listen socket to be bound to the L3 domain in | |
371 | which the packets originated. Only valid when the kernel was | |
372 | compiled with CONFIG_NET_L3_MASTER_DEV. | |
6897445f | 373 | Default: 0 (disabled) |
6dd9a14e | 374 | |
ef56e622 | 375 | tcp_low_latency - BOOLEAN |
b6690b14 | 376 | This is a legacy option, it has no effect anymore. |
1da177e4 LT |
377 | |
378 | tcp_max_orphans - INTEGER | |
379 | Maximal number of TCP sockets not attached to any user file handle, | |
380 | held by system. If this number is exceeded orphaned connections are | |
381 | reset immediately and warning is printed. This limit exists | |
382 | only to prevent simple DoS attacks, you _must_ not rely on this | |
383 | or lower the limit artificially, but rather increase it | |
384 | (probably, after increasing installed memory), | |
385 | if network conditions require more than default value, | |
386 | and tune network services to linger and kill such states | |
387 | more aggressively. Let me to remind again: each orphan eats | |
388 | up to ~64K of unswappable memory. | |
389 | ||
1da177e4 | 390 | tcp_max_syn_backlog - INTEGER |
99b53bdd PP |
391 | Maximal number of remembered connection requests, which have not |
392 | received an acknowledgment from connecting client. | |
393 | The minimal value is 128 for low memory machines, and it will | |
394 | increase in proportion to the memory of machine. | |
395 | If server suffers from overload, try increasing this number. | |
1da177e4 | 396 | |
ef56e622 SH |
397 | tcp_max_tw_buckets - INTEGER |
398 | Maximal number of timewait sockets held by system simultaneously. | |
399 | If this number is exceeded time-wait socket is immediately destroyed | |
400 | and warning is printed. This limit exists only to prevent | |
401 | simple DoS attacks, you _must_ not lower the limit artificially, | |
402 | but rather increase it (probably, after increasing installed memory), | |
403 | if network conditions require more than default value. | |
1da177e4 | 404 | |
ef56e622 SH |
405 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
406 | min: below this number of pages TCP is not bothered about its | |
407 | memory appetite. | |
1da177e4 | 408 | |
ef56e622 SH |
409 | pressure: when amount of memory allocated by TCP exceeds this number |
410 | of pages, TCP moderates its memory consumption and enters memory | |
411 | pressure mode, which is exited when memory consumption falls | |
412 | under "min". | |
1da177e4 | 413 | |
ef56e622 | 414 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 415 | |
ef56e622 SH |
416 | Defaults are calculated at boot time from amount of available |
417 | memory. | |
1da177e4 | 418 | |
f6722583 YC |
419 | tcp_min_rtt_wlen - INTEGER |
420 | The window length of the windowed min filter to track the minimum RTT. | |
421 | A shorter window lets a flow more quickly pick up new (higher) | |
422 | minimum RTT when it is moved to a longer path (e.g., due to traffic | |
423 | engineering). A longer window makes the filter more resistant to RTT | |
424 | inflations such as transient congestion. The unit is seconds. | |
425 | Default: 300 | |
426 | ||
71599cd1 | 427 | tcp_moderate_rcvbuf - BOOLEAN |
4edc2f34 | 428 | If set, TCP performs receive buffer auto-tuning, attempting to |
71599cd1 JH |
429 | automatically size the buffer (no greater than tcp_rmem[2]) to |
430 | match the size required by the path for full throughput. Enabled by | |
431 | default. | |
432 | ||
433 | tcp_mtu_probing - INTEGER | |
434 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
435 | values: | |
436 | 0 - Disabled | |
437 | 1 - Disabled by default, enabled when an ICMP black hole detected | |
438 | 2 - Always enabled, use initial MSS of tcp_base_mss. | |
439 | ||
d4ce5808 | 440 | tcp_probe_interval - UNSIGNED INTEGER |
fab42760 FD |
441 | Controls how often to start TCP Packetization-Layer Path MTU |
442 | Discovery reprobe. The default is reprobing every 10 minutes as | |
443 | per RFC4821. | |
444 | ||
445 | tcp_probe_threshold - INTEGER | |
446 | Controls when TCP Packetization-Layer Path MTU Discovery probing | |
447 | will stop in respect to the width of search range in bytes. Default | |
448 | is 8 bytes. | |
449 | ||
71599cd1 JH |
450 | tcp_no_metrics_save - BOOLEAN |
451 | By default, TCP saves various connection metrics in the route cache | |
452 | when the connection closes, so that connections established in the | |
453 | near future can use these to set initial conditions. Usually, this | |
454 | increases overall performance, but may sometimes cause performance | |
0f035b8e | 455 | degradation. If set, TCP will not cache metrics on closing |
71599cd1 JH |
456 | connections. |
457 | ||
ef56e622 | 458 | tcp_orphan_retries - INTEGER |
5d789229 DL |
459 | This value influences the timeout of a locally closed TCP connection, |
460 | when RTO retransmissions remain unacknowledged. | |
461 | See tcp_retries2 for more details. | |
462 | ||
06b8fc5d | 463 | The default value is 8. |
5d789229 | 464 | If your machine is a loaded WEB server, |
ef56e622 SH |
465 | you should think about lowering this value, such sockets |
466 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 | 467 | |
4f41b1c5 YC |
468 | tcp_recovery - INTEGER |
469 | This value is a bitmap to enable various experimental loss recovery | |
470 | features. | |
471 | ||
472 | RACK: 0x1 enables the RACK loss detection for fast detection of lost | |
b38a51fe YC |
473 | retransmissions and tail drops. It also subsumes and disables |
474 | RFC6675 recovery for SACK connections. | |
1f255691 | 475 | RACK: 0x2 makes RACK's reordering window static (min_rtt/4). |
20b654df | 476 | RACK: 0x4 disables RACK's DUPACK threshold heuristic |
4f41b1c5 YC |
477 | |
478 | Default: 0x1 | |
479 | ||
1da177e4 | 480 | tcp_reordering - INTEGER |
dca145ff ED |
481 | Initial reordering level of packets in a TCP stream. |
482 | TCP stack can then dynamically adjust flow reordering level | |
483 | between this initial value and tcp_max_reordering | |
e18f5feb | 484 | Default: 3 |
1da177e4 | 485 | |
dca145ff ED |
486 | tcp_max_reordering - INTEGER |
487 | Maximal reordering level of packets in a TCP stream. | |
488 | 300 is a fairly conservative value, but you might increase it | |
489 | if paths are using per packet load balancing (like bonding rr mode) | |
490 | Default: 300 | |
491 | ||
1da177e4 LT |
492 | tcp_retrans_collapse - BOOLEAN |
493 | Bug-to-bug compatibility with some broken printers. | |
494 | On retransmit try to send bigger packets to work around bugs in | |
495 | certain TCP stacks. | |
496 | ||
ef56e622 | 497 | tcp_retries1 - INTEGER |
5d789229 DL |
498 | This value influences the time, after which TCP decides, that |
499 | something is wrong due to unacknowledged RTO retransmissions, | |
500 | and reports this suspicion to the network layer. | |
501 | See tcp_retries2 for more details. | |
502 | ||
503 | RFC 1122 recommends at least 3 retransmissions, which is the | |
504 | default. | |
1da177e4 | 505 | |
ef56e622 | 506 | tcp_retries2 - INTEGER |
5d789229 DL |
507 | This value influences the timeout of an alive TCP connection, |
508 | when RTO retransmissions remain unacknowledged. | |
509 | Given a value of N, a hypothetical TCP connection following | |
510 | exponential backoff with an initial RTO of TCP_RTO_MIN would | |
511 | retransmit N times before killing the connection at the (N+1)th RTO. | |
512 | ||
513 | The default value of 15 yields a hypothetical timeout of 924.6 | |
514 | seconds and is a lower bound for the effective timeout. | |
515 | TCP will effectively time out at the first RTO which exceeds the | |
516 | hypothetical timeout. | |
517 | ||
518 | RFC 1122 recommends at least 100 seconds for the timeout, | |
519 | which corresponds to a value of at least 8. | |
1da177e4 | 520 | |
ef56e622 SH |
521 | tcp_rfc1337 - BOOLEAN |
522 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
523 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
524 | assassination. | |
525 | Default: 0 | |
1da177e4 LT |
526 | |
527 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
528 | min: Minimal size of receive buffer used by TCP sockets. | |
529 | It is guaranteed to each TCP socket, even under moderate memory | |
530 | pressure. | |
a61a86f8 | 531 | Default: 4K |
1da177e4 | 532 | |
53025f5e | 533 | default: initial size of receive buffer used by TCP sockets. |
1da177e4 LT |
534 | This value overrides net.core.rmem_default used by other protocols. |
535 | Default: 87380 bytes. This value results in window of 65535 with | |
536 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
537 | less for default tcp_app_win. See below about these variables. | |
538 | ||
539 | max: maximal size of receive buffer allowed for automatically | |
540 | selected receiver buffers for TCP socket. This value does not override | |
53025f5e BF |
541 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
542 | automatic tuning of that socket's receive buffer size, in which | |
543 | case this value is ignored. | |
b49960a0 | 544 | Default: between 87380B and 6MB, depending on RAM size. |
1da177e4 | 545 | |
ef56e622 SH |
546 | tcp_sack - BOOLEAN |
547 | Enable select acknowledgments (SACKS). | |
1da177e4 | 548 | |
6d82aa24 ED |
549 | tcp_comp_sack_delay_ns - LONG INTEGER |
550 | TCP tries to reduce number of SACK sent, using a timer | |
551 | based on 5% of SRTT, capped by this sysctl, in nano seconds. | |
552 | The default is 1ms, based on TSO autosizing period. | |
553 | ||
554 | Default : 1,000,000 ns (1 ms) | |
555 | ||
9c21d2fc ED |
556 | tcp_comp_sack_nr - INTEGER |
557 | Max numer of SACK that can be compressed. | |
558 | Using 0 disables SACK compression. | |
559 | ||
560 | Detault : 44 | |
561 | ||
ef56e622 SH |
562 | tcp_slow_start_after_idle - BOOLEAN |
563 | If set, provide RFC2861 behavior and time out the congestion | |
564 | window after an idle period. An idle period is defined at | |
565 | the current RTO. If unset, the congestion window will not | |
566 | be timed out after an idle period. | |
567 | Default: 1 | |
1da177e4 | 568 | |
ef56e622 | 569 | tcp_stdurg - BOOLEAN |
4edc2f34 | 570 | Use the Host requirements interpretation of the TCP urgent pointer field. |
ef56e622 SH |
571 | Most hosts use the older BSD interpretation, so if you turn this on |
572 | Linux might not communicate correctly with them. | |
573 | Default: FALSE | |
1da177e4 | 574 | |
ef56e622 SH |
575 | tcp_synack_retries - INTEGER |
576 | Number of times SYNACKs for a passive TCP connection attempt will | |
577 | be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
578 | is 5, which corresponds to 31seconds till the last retransmission |
579 | with the current initial RTO of 1second. With this the final timeout | |
580 | for a passive TCP connection will happen after 63seconds. | |
1da177e4 | 581 | |
ef56e622 | 582 | tcp_syncookies - BOOLEAN |
a3c910d2 | 583 | Only valid when the kernel was compiled with CONFIG_SYN_COOKIES |
ef56e622 | 584 | Send out syncookies when the syn backlog queue of a socket |
4edc2f34 | 585 | overflows. This is to prevent against the common 'SYN flood attack' |
a3c910d2 | 586 | Default: 1 |
1da177e4 | 587 | |
ef56e622 SH |
588 | Note, that syncookies is fallback facility. |
589 | It MUST NOT be used to help highly loaded servers to stand | |
4edc2f34 | 590 | against legal connection rate. If you see SYN flood warnings |
ef56e622 SH |
591 | in your logs, but investigation shows that they occur |
592 | because of overload with legal connections, you should tune | |
593 | another parameters until this warning disappear. | |
594 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 595 | |
ef56e622 SH |
596 | syncookies seriously violate TCP protocol, do not allow |
597 | to use TCP extensions, can result in serious degradation | |
598 | of some services (f.e. SMTP relaying), visible not by you, | |
599 | but your clients and relays, contacting you. While you see | |
4edc2f34 | 600 | SYN flood warnings in logs not being really flooded, your server |
ef56e622 | 601 | is seriously misconfigured. |
1da177e4 | 602 | |
5ad37d5d HFS |
603 | If you want to test which effects syncookies have to your |
604 | network connections you can set this knob to 2 to enable | |
605 | unconditionally generation of syncookies. | |
606 | ||
cf60af03 | 607 | tcp_fastopen - INTEGER |
cebc5cba YC |
608 | Enable TCP Fast Open (RFC7413) to send and accept data in the opening |
609 | SYN packet. | |
10467163 | 610 | |
cebc5cba YC |
611 | The client support is enabled by flag 0x1 (on by default). The client |
612 | then must use sendmsg() or sendto() with the MSG_FASTOPEN flag, | |
613 | rather than connect() to send data in SYN. | |
cf60af03 | 614 | |
cebc5cba YC |
615 | The server support is enabled by flag 0x2 (off by default). Then |
616 | either enable for all listeners with another flag (0x400) or | |
617 | enable individual listeners via TCP_FASTOPEN socket option with | |
618 | the option value being the length of the syn-data backlog. | |
cf60af03 | 619 | |
cebc5cba YC |
620 | The values (bitmap) are |
621 | 0x1: (client) enables sending data in the opening SYN on the client. | |
622 | 0x2: (server) enables the server support, i.e., allowing data in | |
623 | a SYN packet to be accepted and passed to the | |
624 | application before 3-way handshake finishes. | |
625 | 0x4: (client) send data in the opening SYN regardless of cookie | |
626 | availability and without a cookie option. | |
627 | 0x200: (server) accept data-in-SYN w/o any cookie option present. | |
628 | 0x400: (server) enable all listeners to support Fast Open by | |
629 | default without explicit TCP_FASTOPEN socket option. | |
630 | ||
631 | Default: 0x1 | |
10467163 | 632 | |
cebc5cba YC |
633 | Note that that additional client or server features are only |
634 | effective if the basic support (0x1 and 0x2) are enabled respectively. | |
10467163 | 635 | |
cf1ef3f0 WW |
636 | tcp_fastopen_blackhole_timeout_sec - INTEGER |
637 | Initial time period in second to disable Fastopen on active TCP sockets | |
638 | when a TFO firewall blackhole issue happens. | |
639 | This time period will grow exponentially when more blackhole issues | |
640 | get detected right after Fastopen is re-enabled and will reset to | |
641 | initial value when the blackhole issue goes away. | |
7268586b | 642 | 0 to disable the blackhole detection. |
cf1ef3f0 WW |
643 | By default, it is set to 1hr. |
644 | ||
ef56e622 SH |
645 | tcp_syn_retries - INTEGER |
646 | Number of times initial SYNs for an active TCP connection attempt | |
bffae697 | 647 | will be retransmitted. Should not be higher than 127. Default value |
3b09adcb | 648 | is 6, which corresponds to 63seconds till the last retransmission |
6c9ff979 AB |
649 | with the current initial RTO of 1second. With this the final timeout |
650 | for an active TCP connection attempt will happen after 127seconds. | |
ef56e622 | 651 | |
25429d7b FW |
652 | tcp_timestamps - INTEGER |
653 | Enable timestamps as defined in RFC1323. | |
654 | 0: Disabled. | |
655 | 1: Enable timestamps as defined in RFC1323 and use random offset for | |
656 | each connection rather than only using the current time. | |
657 | 2: Like 1, but without random offsets. | |
658 | Default: 1 | |
1da177e4 | 659 | |
95bd09eb ED |
660 | tcp_min_tso_segs - INTEGER |
661 | Minimal number of segments per TSO frame. | |
662 | Since linux-3.12, TCP does an automatic sizing of TSO frames, | |
663 | depending on flow rate, instead of filling 64Kbytes packets. | |
664 | For specific usages, it's possible to force TCP to build big | |
665 | TSO frames. Note that TCP stack might split too big TSO packets | |
666 | if available window is too small. | |
667 | Default: 2 | |
668 | ||
43e122b0 ED |
669 | tcp_pacing_ss_ratio - INTEGER |
670 | sk->sk_pacing_rate is set by TCP stack using a ratio applied | |
671 | to current rate. (current_rate = cwnd * mss / srtt) | |
672 | If TCP is in slow start, tcp_pacing_ss_ratio is applied | |
673 | to let TCP probe for bigger speeds, assuming cwnd can be | |
674 | doubled every other RTT. | |
675 | Default: 200 | |
676 | ||
677 | tcp_pacing_ca_ratio - INTEGER | |
678 | sk->sk_pacing_rate is set by TCP stack using a ratio applied | |
679 | to current rate. (current_rate = cwnd * mss / srtt) | |
680 | If TCP is in congestion avoidance phase, tcp_pacing_ca_ratio | |
681 | is applied to conservatively probe for bigger throughput. | |
682 | Default: 120 | |
683 | ||
1da177e4 | 684 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
685 | This allows control over what percentage of the congestion window |
686 | can be consumed by a single TSO frame. | |
687 | The setting of this parameter is a choice between burstiness and | |
688 | building larger TSO frames. | |
689 | Default: 3 | |
1da177e4 | 690 | |
79e9fed4 MŻ |
691 | tcp_tw_reuse - INTEGER |
692 | Enable reuse of TIME-WAIT sockets for new connections when it is | |
693 | safe from protocol viewpoint. | |
694 | 0 - disable | |
695 | 1 - global enable | |
696 | 2 - enable for loopback traffic only | |
ef56e622 SH |
697 | It should not be changed without advice/request of technical |
698 | experts. | |
79e9fed4 | 699 | Default: 2 |
ce7bc3bf | 700 | |
ef56e622 SH |
701 | tcp_window_scaling - BOOLEAN |
702 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 703 | |
ef56e622 | 704 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
53025f5e | 705 | min: Amount of memory reserved for send buffers for TCP sockets. |
ef56e622 | 706 | Each TCP socket has rights to use it due to fact of its birth. |
a61a86f8 | 707 | Default: 4K |
9d7bcfc6 | 708 | |
53025f5e BF |
709 | default: initial size of send buffer used by TCP sockets. This |
710 | value overrides net.core.wmem_default used by other protocols. | |
711 | It is usually lower than net.core.wmem_default. | |
ef56e622 SH |
712 | Default: 16K |
713 | ||
53025f5e BF |
714 | max: Maximal amount of memory allowed for automatically tuned |
715 | send buffers for TCP sockets. This value does not override | |
716 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
717 | automatic tuning of that socket's send buffer size, in which case | |
718 | this value is ignored. | |
719 | Default: between 64K and 4MB, depending on RAM size. | |
1da177e4 | 720 | |
c9bee3b7 ED |
721 | tcp_notsent_lowat - UNSIGNED INTEGER |
722 | A TCP socket can control the amount of unsent bytes in its write queue, | |
723 | thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll() | |
724 | reports POLLOUT events if the amount of unsent bytes is below a per | |
725 | socket value, and if the write queue is not full. sendmsg() will | |
726 | also not add new buffers if the limit is hit. | |
727 | ||
728 | This global variable controls the amount of unsent data for | |
729 | sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change | |
730 | to the global variable has immediate effect. | |
731 | ||
732 | Default: UINT_MAX (0xFFFFFFFF) | |
733 | ||
15d99e02 RJ |
734 | tcp_workaround_signed_windows - BOOLEAN |
735 | If set, assume no receipt of a window scaling option means the | |
736 | remote TCP is broken and treats the window as a signed quantity. | |
737 | If unset, assume the remote TCP is not broken even if we do | |
738 | not receive a window scaling option from them. | |
739 | Default: 0 | |
740 | ||
36e31b0a AP |
741 | tcp_thin_linear_timeouts - BOOLEAN |
742 | Enable dynamic triggering of linear timeouts for thin streams. | |
743 | If set, a check is performed upon retransmission by timeout to | |
744 | determine if the stream is thin (less than 4 packets in flight). | |
745 | As long as the stream is found to be thin, up to 6 linear | |
746 | timeouts may be performed before exponential backoff mode is | |
747 | initiated. This improves retransmission latency for | |
748 | non-aggressive thin streams, often found to be time-dependent. | |
749 | For more information on thin streams, see | |
750 | Documentation/networking/tcp-thin.txt | |
751 | Default: 0 | |
752 | ||
46d3ceab ED |
753 | tcp_limit_output_bytes - INTEGER |
754 | Controls TCP Small Queue limit per tcp socket. | |
755 | TCP bulk sender tends to increase packets in flight until it | |
756 | gets losses notifications. With SNDBUF autotuning, this can | |
9c4c3252 FL |
757 | result in a large amount of packets queued on the local machine |
758 | (e.g.: qdiscs, CPU backlog, or device) hurting latency of other | |
759 | flows, for typical pfifo_fast qdiscs. tcp_limit_output_bytes | |
760 | limits the number of bytes on qdisc or device to reduce artificial | |
761 | RTT/cwnd and reduce bufferbloat. | |
c73e5807 | 762 | Default: 1048576 (16 * 65536) |
46d3ceab | 763 | |
282f23c6 ED |
764 | tcp_challenge_ack_limit - INTEGER |
765 | Limits number of Challenge ACK sent per second, as recommended | |
766 | in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) | |
767 | Default: 100 | |
768 | ||
95766fff HA |
769 | UDP variables: |
770 | ||
63a6fff3 RS |
771 | udp_l3mdev_accept - BOOLEAN |
772 | Enabling this option allows a "global" bound socket to work | |
773 | across L3 master domains (e.g., VRFs) with packets capable of | |
774 | being received regardless of the L3 domain in which they | |
775 | originated. Only valid when the kernel was compiled with | |
776 | CONFIG_NET_L3_MASTER_DEV. | |
6897445f | 777 | Default: 0 (disabled) |
63a6fff3 | 778 | |
95766fff HA |
779 | udp_mem - vector of 3 INTEGERs: min, pressure, max |
780 | Number of pages allowed for queueing by all UDP sockets. | |
781 | ||
782 | min: Below this number of pages UDP is not bothered about its | |
783 | memory appetite. When amount of memory allocated by UDP exceeds | |
784 | this number, UDP starts to moderate memory usage. | |
785 | ||
786 | pressure: This value was introduced to follow format of tcp_mem. | |
787 | ||
788 | max: Number of pages allowed for queueing by all UDP sockets. | |
789 | ||
790 | Default is calculated at boot time from amount of available memory. | |
791 | ||
792 | udp_rmem_min - INTEGER | |
793 | Minimal size of receive buffer used by UDP sockets in moderation. | |
794 | Each UDP socket is able to use the size for receiving data, even if | |
795 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
320bd6de | 796 | Default: 4K |
95766fff HA |
797 | |
798 | udp_wmem_min - INTEGER | |
799 | Minimal size of send buffer used by UDP sockets in moderation. | |
800 | Each UDP socket is able to use the size for sending data, even if | |
801 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
320bd6de | 802 | Default: 4K |
95766fff | 803 | |
6897445f MM |
804 | RAW variables: |
805 | ||
806 | raw_l3mdev_accept - BOOLEAN | |
807 | Enabling this option allows a "global" bound socket to work | |
808 | across L3 master domains (e.g., VRFs) with packets capable of | |
809 | being received regardless of the L3 domain in which they | |
810 | originated. Only valid when the kernel was compiled with | |
811 | CONFIG_NET_L3_MASTER_DEV. | |
812 | Default: 1 (enabled) | |
813 | ||
8802f616 PM |
814 | CIPSOv4 Variables: |
815 | ||
816 | cipso_cache_enable - BOOLEAN | |
817 | If set, enable additions to and lookups from the CIPSO label mapping | |
818 | cache. If unset, additions are ignored and lookups always result in a | |
819 | miss. However, regardless of the setting the cache is still | |
820 | invalidated when required when means you can safely toggle this on and | |
821 | off and the cache will always be "safe". | |
822 | Default: 1 | |
823 | ||
824 | cipso_cache_bucket_size - INTEGER | |
825 | The CIPSO label cache consists of a fixed size hash table with each | |
826 | hash bucket containing a number of cache entries. This variable limits | |
827 | the number of entries in each hash bucket; the larger the value the | |
828 | more CIPSO label mappings that can be cached. When the number of | |
829 | entries in a given hash bucket reaches this limit adding new entries | |
830 | causes the oldest entry in the bucket to be removed to make room. | |
831 | Default: 10 | |
832 | ||
833 | cipso_rbm_optfmt - BOOLEAN | |
834 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
835 | the CIPSO draft specification (see Documentation/netlabel for details). | |
836 | This means that when set the CIPSO tag will be padded with empty | |
837 | categories in order to make the packet data 32-bit aligned. | |
838 | Default: 0 | |
839 | ||
840 | cipso_rbm_structvalid - BOOLEAN | |
841 | If set, do a very strict check of the CIPSO option when | |
842 | ip_options_compile() is called. If unset, relax the checks done during | |
843 | ip_options_compile(). Either way is "safe" as errors are caught else | |
844 | where in the CIPSO processing code but setting this to 0 (False) should | |
845 | result in less work (i.e. it should be faster) but could cause problems | |
846 | with other implementations that require strict checking. | |
847 | Default: 0 | |
848 | ||
1da177e4 LT |
849 | IP Variables: |
850 | ||
851 | ip_local_port_range - 2 INTEGERS | |
852 | Defines the local port range that is used by TCP and UDP to | |
e18f5feb | 853 | choose the local port. The first number is the first, the |
07f4c900 ED |
854 | second the last local port number. |
855 | If possible, it is better these numbers have different parity. | |
856 | (one even and one odd values) | |
857 | The default values are 32768 and 60999 respectively. | |
1da177e4 | 858 | |
e3826f1e AW |
859 | ip_local_reserved_ports - list of comma separated ranges |
860 | Specify the ports which are reserved for known third-party | |
861 | applications. These ports will not be used by automatic port | |
862 | assignments (e.g. when calling connect() or bind() with port | |
863 | number 0). Explicit port allocation behavior is unchanged. | |
864 | ||
865 | The format used for both input and output is a comma separated | |
866 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and | |
867 | 10). Writing to the file will clear all previously reserved | |
868 | ports and update the current list with the one given in the | |
869 | input. | |
870 | ||
871 | Note that ip_local_port_range and ip_local_reserved_ports | |
872 | settings are independent and both are considered by the kernel | |
873 | when determining which ports are available for automatic port | |
874 | assignments. | |
875 | ||
876 | You can reserve ports which are not in the current | |
877 | ip_local_port_range, e.g.: | |
878 | ||
879 | $ cat /proc/sys/net/ipv4/ip_local_port_range | |
07f4c900 | 880 | 32000 60999 |
e3826f1e AW |
881 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports |
882 | 8080,9148 | |
883 | ||
884 | although this is redundant. However such a setting is useful | |
885 | if later the port range is changed to a value that will | |
886 | include the reserved ports. | |
887 | ||
888 | Default: Empty | |
889 | ||
4548b683 KJ |
890 | ip_unprivileged_port_start - INTEGER |
891 | This is a per-namespace sysctl. It defines the first | |
892 | unprivileged port in the network namespace. Privileged ports | |
893 | require root or CAP_NET_BIND_SERVICE in order to bind to them. | |
894 | To disable all privileged ports, set this to 0. It may not | |
895 | overlap with the ip_local_reserved_ports range. | |
896 | ||
897 | Default: 1024 | |
898 | ||
1da177e4 LT |
899 | ip_nonlocal_bind - BOOLEAN |
900 | If set, allows processes to bind() to non-local IP addresses, | |
901 | which can be quite useful - but may break some applications. | |
902 | Default: 0 | |
903 | ||
904 | ip_dynaddr - BOOLEAN | |
905 | If set non-zero, enables support for dynamic addresses. | |
906 | If set to a non-zero value larger than 1, a kernel log | |
907 | message will be printed when dynamic address rewriting | |
908 | occurs. | |
909 | Default: 0 | |
910 | ||
e3d73bce CW |
911 | ip_early_demux - BOOLEAN |
912 | Optimize input packet processing down to one demux for | |
913 | certain kinds of local sockets. Currently we only do this | |
dddb64bc | 914 | for established TCP and connected UDP sockets. |
e3d73bce CW |
915 | |
916 | It may add an additional cost for pure routing workloads that | |
917 | reduces overall throughput, in such case you should disable it. | |
918 | Default: 1 | |
919 | ||
dddb64bc | 920 | tcp_early_demux - BOOLEAN |
921 | Enable early demux for established TCP sockets. | |
922 | Default: 1 | |
923 | ||
924 | udp_early_demux - BOOLEAN | |
925 | Enable early demux for connected UDP sockets. Disable this if | |
926 | your system could experience more unconnected load. | |
927 | Default: 1 | |
928 | ||
1da177e4 | 929 | icmp_echo_ignore_all - BOOLEAN |
7ce31246 DM |
930 | If set non-zero, then the kernel will ignore all ICMP ECHO |
931 | requests sent to it. | |
932 | Default: 0 | |
933 | ||
1da177e4 | 934 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
935 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
936 | TIMESTAMP requests sent to it via broadcast/multicast. | |
937 | Default: 1 | |
1da177e4 LT |
938 | |
939 | icmp_ratelimit - INTEGER | |
940 | Limit the maximal rates for sending ICMP packets whose type matches | |
941 | icmp_ratemask (see below) to specific targets. | |
6dbf4bca SH |
942 | 0 to disable any limiting, |
943 | otherwise the minimal space between responses in milliseconds. | |
4cdf507d ED |
944 | Note that another sysctl, icmp_msgs_per_sec limits the number |
945 | of ICMP packets sent on all targets. | |
6dbf4bca | 946 | Default: 1000 |
1da177e4 | 947 | |
4cdf507d ED |
948 | icmp_msgs_per_sec - INTEGER |
949 | Limit maximal number of ICMP packets sent per second from this host. | |
950 | Only messages whose type matches icmp_ratemask (see below) are | |
951 | controlled by this limit. | |
6dbf4bca | 952 | Default: 1000 |
1da177e4 | 953 | |
4cdf507d ED |
954 | icmp_msgs_burst - INTEGER |
955 | icmp_msgs_per_sec controls number of ICMP packets sent per second, | |
956 | while icmp_msgs_burst controls the burst size of these packets. | |
957 | Default: 50 | |
958 | ||
1da177e4 LT |
959 | icmp_ratemask - INTEGER |
960 | Mask made of ICMP types for which rates are being limited. | |
961 | Significant bits: IHGFEDCBA9876543210 | |
962 | Default mask: 0000001100000011000 (6168) | |
963 | ||
964 | Bit definitions (see include/linux/icmp.h): | |
965 | 0 Echo Reply | |
966 | 3 Destination Unreachable * | |
967 | 4 Source Quench * | |
968 | 5 Redirect | |
969 | 8 Echo Request | |
970 | B Time Exceeded * | |
971 | C Parameter Problem * | |
972 | D Timestamp Request | |
973 | E Timestamp Reply | |
974 | F Info Request | |
975 | G Info Reply | |
976 | H Address Mask Request | |
977 | I Address Mask Reply | |
978 | ||
979 | * These are rate limited by default (see default mask above) | |
980 | ||
981 | icmp_ignore_bogus_error_responses - BOOLEAN | |
982 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
983 | frames. Such violations are normally logged via a kernel warning. | |
984 | If this is set to TRUE, the kernel will not give such warnings, which | |
985 | will avoid log file clutter. | |
e8b265e8 | 986 | Default: 1 |
1da177e4 | 987 | |
95f7daf1 H |
988 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
989 | ||
02a6d613 PA |
990 | If zero, icmp error messages are sent with the primary address of |
991 | the exiting interface. | |
e18f5feb | 992 | |
95f7daf1 H |
993 | If non-zero, the message will be sent with the primary address of |
994 | the interface that received the packet that caused the icmp error. | |
995 | This is the behaviour network many administrators will expect from | |
996 | a router. And it can make debugging complicated network layouts | |
e18f5feb | 997 | much easier. |
95f7daf1 H |
998 | |
999 | Note that if no primary address exists for the interface selected, | |
1000 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 1001 | has one will be used regardless of this setting. |
95f7daf1 H |
1002 | |
1003 | Default: 0 | |
1004 | ||
1da177e4 LT |
1005 | igmp_max_memberships - INTEGER |
1006 | Change the maximum number of multicast groups we can subscribe to. | |
1007 | Default: 20 | |
1008 | ||
d67ef35f JE |
1009 | Theoretical maximum value is bounded by having to send a membership |
1010 | report in a single datagram (i.e. the report can't span multiple | |
1011 | datagrams, or risk confusing the switch and leaving groups you don't | |
1012 | intend to). | |
1da177e4 | 1013 | |
d67ef35f JE |
1014 | The number of supported groups 'M' is bounded by the number of group |
1015 | report entries you can fit into a single datagram of 65535 bytes. | |
1016 | ||
1017 | M = 65536-sizeof (ip header)/(sizeof(Group record)) | |
1018 | ||
1019 | Group records are variable length, with a minimum of 12 bytes. | |
1020 | So net.ipv4.igmp_max_memberships should not be set higher than: | |
1021 | ||
1022 | (65536-24) / 12 = 5459 | |
1023 | ||
1024 | The value 5459 assumes no IP header options, so in practice | |
1025 | this number may be lower. | |
1026 | ||
537377d3 BP |
1027 | igmp_max_msf - INTEGER |
1028 | Maximum number of addresses allowed in the source filter list for a | |
1029 | multicast group. | |
1030 | Default: 10 | |
1031 | ||
a9fe8e29 | 1032 | igmp_qrv - INTEGER |
537377d3 BP |
1033 | Controls the IGMP query robustness variable (see RFC2236 8.1). |
1034 | Default: 2 (as specified by RFC2236 8.1) | |
1035 | Minimum: 1 (as specified by RFC6636 4.5) | |
a9fe8e29 | 1036 | |
1af92836 HL |
1037 | force_igmp_version - INTEGER |
1038 | 0 - (default) No enforcement of a IGMP version, IGMPv1/v2 fallback | |
1039 | allowed. Will back to IGMPv3 mode again if all IGMPv1/v2 Querier | |
1040 | Present timer expires. | |
1041 | 1 - Enforce to use IGMP version 1. Will also reply IGMPv1 report if | |
1042 | receive IGMPv2/v3 query. | |
1043 | 2 - Enforce to use IGMP version 2. Will fallback to IGMPv1 if receive | |
1044 | IGMPv1 query message. Will reply report if receive IGMPv3 query. | |
1045 | 3 - Enforce to use IGMP version 3. The same react with default 0. | |
1046 | ||
1047 | Note: this is not the same with force_mld_version because IGMPv3 RFC3376 | |
1048 | Security Considerations does not have clear description that we could | |
1049 | ignore other version messages completely as MLDv2 RFC3810. So make | |
1050 | this value as default 0 is recommended. | |
1051 | ||
6b226e2f BP |
1052 | conf/interface/* changes special settings per interface (where |
1053 | "interface" is the name of your network interface) | |
1054 | ||
1055 | conf/all/* is special, changes the settings for all interfaces | |
1056 | ||
1da177e4 LT |
1057 | log_martians - BOOLEAN |
1058 | Log packets with impossible addresses to kernel log. | |
1059 | log_martians for the interface will be enabled if at least one of | |
1060 | conf/{all,interface}/log_martians is set to TRUE, | |
1061 | it will be disabled otherwise | |
1062 | ||
1063 | accept_redirects - BOOLEAN | |
1064 | Accept ICMP redirect messages. | |
1065 | accept_redirects for the interface will be enabled if: | |
e18f5feb JDB |
1066 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
1067 | forwarding for the interface is enabled | |
1da177e4 | 1068 | or |
e18f5feb JDB |
1069 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
1070 | case forwarding for the interface is disabled | |
1da177e4 LT |
1071 | accept_redirects for the interface will be disabled otherwise |
1072 | default TRUE (host) | |
1073 | FALSE (router) | |
1074 | ||
1075 | forwarding - BOOLEAN | |
88a7cddc NJ |
1076 | Enable IP forwarding on this interface. This controls whether packets |
1077 | received _on_ this interface can be forwarded. | |
1da177e4 LT |
1078 | |
1079 | mc_forwarding - BOOLEAN | |
1080 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
1081 | and a multicast routing daemon is required. | |
e18f5feb JDB |
1082 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
1083 | routing for the interface | |
1da177e4 LT |
1084 | |
1085 | medium_id - INTEGER | |
1086 | Integer value used to differentiate the devices by the medium they | |
1087 | are attached to. Two devices can have different id values when | |
1088 | the broadcast packets are received only on one of them. | |
1089 | The default value 0 means that the device is the only interface | |
1090 | to its medium, value of -1 means that medium is not known. | |
e18f5feb | 1091 | |
1da177e4 LT |
1092 | Currently, it is used to change the proxy_arp behavior: |
1093 | the proxy_arp feature is enabled for packets forwarded between | |
1094 | two devices attached to different media. | |
1095 | ||
1096 | proxy_arp - BOOLEAN | |
1097 | Do proxy arp. | |
1098 | proxy_arp for the interface will be enabled if at least one of | |
1099 | conf/{all,interface}/proxy_arp is set to TRUE, | |
1100 | it will be disabled otherwise | |
1101 | ||
65324144 JDB |
1102 | proxy_arp_pvlan - BOOLEAN |
1103 | Private VLAN proxy arp. | |
1104 | Basically allow proxy arp replies back to the same interface | |
1105 | (from which the ARP request/solicitation was received). | |
1106 | ||
1107 | This is done to support (ethernet) switch features, like RFC | |
1108 | 3069, where the individual ports are NOT allowed to | |
1109 | communicate with each other, but they are allowed to talk to | |
1110 | the upstream router. As described in RFC 3069, it is possible | |
1111 | to allow these hosts to communicate through the upstream | |
1112 | router by proxy_arp'ing. Don't need to be used together with | |
1113 | proxy_arp. | |
1114 | ||
1115 | This technology is known by different names: | |
1116 | In RFC 3069 it is called VLAN Aggregation. | |
1117 | Cisco and Allied Telesyn call it Private VLAN. | |
1118 | Hewlett-Packard call it Source-Port filtering or port-isolation. | |
1119 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | |
1120 | ||
1da177e4 LT |
1121 | shared_media - BOOLEAN |
1122 | Send(router) or accept(host) RFC1620 shared media redirects. | |
176b346b | 1123 | Overrides secure_redirects. |
1da177e4 LT |
1124 | shared_media for the interface will be enabled if at least one of |
1125 | conf/{all,interface}/shared_media is set to TRUE, | |
1126 | it will be disabled otherwise | |
1127 | default TRUE | |
1128 | ||
1129 | secure_redirects - BOOLEAN | |
176b346b EG |
1130 | Accept ICMP redirect messages only to gateways listed in the |
1131 | interface's current gateway list. Even if disabled, RFC1122 redirect | |
1132 | rules still apply. | |
1133 | Overridden by shared_media. | |
1da177e4 LT |
1134 | secure_redirects for the interface will be enabled if at least one of |
1135 | conf/{all,interface}/secure_redirects is set to TRUE, | |
1136 | it will be disabled otherwise | |
1137 | default TRUE | |
1138 | ||
1139 | send_redirects - BOOLEAN | |
1140 | Send redirects, if router. | |
1141 | send_redirects for the interface will be enabled if at least one of | |
1142 | conf/{all,interface}/send_redirects is set to TRUE, | |
1143 | it will be disabled otherwise | |
1144 | Default: TRUE | |
1145 | ||
1146 | bootp_relay - BOOLEAN | |
1147 | Accept packets with source address 0.b.c.d destined | |
1148 | not to this host as local ones. It is supposed, that | |
1149 | BOOTP relay daemon will catch and forward such packets. | |
1150 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
1151 | for the interface | |
1152 | default FALSE | |
1153 | Not Implemented Yet. | |
1154 | ||
1155 | accept_source_route - BOOLEAN | |
1156 | Accept packets with SRR option. | |
1157 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
1158 | with SRR option on the interface | |
1159 | default TRUE (router) | |
1160 | FALSE (host) | |
1161 | ||
8153a10c | 1162 | accept_local - BOOLEAN |
72b126a4 SB |
1163 | Accept packets with local source addresses. In combination with |
1164 | suitable routing, this can be used to direct packets between two | |
1165 | local interfaces over the wire and have them accepted properly. | |
8153a10c PM |
1166 | default FALSE |
1167 | ||
d0daebc3 TG |
1168 | route_localnet - BOOLEAN |
1169 | Do not consider loopback addresses as martian source or destination | |
1170 | while routing. This enables the use of 127/8 for local routing purposes. | |
1171 | default FALSE | |
1172 | ||
c1cf8422 | 1173 | rp_filter - INTEGER |
1da177e4 | 1174 | 0 - No source validation. |
c1cf8422 SH |
1175 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path |
1176 | Each incoming packet is tested against the FIB and if the interface | |
1177 | is not the best reverse path the packet check will fail. | |
1178 | By default failed packets are discarded. | |
1179 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
1180 | Each incoming packet's source address is also tested against the FIB | |
1181 | and if the source address is not reachable via any interface | |
1182 | the packet check will fail. | |
1183 | ||
e18f5feb | 1184 | Current recommended practice in RFC3704 is to enable strict mode |
bf869c30 | 1185 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
e18f5feb | 1186 | or other complicated routing, then loose mode is recommended. |
c1cf8422 | 1187 | |
1f5865e7 SW |
1188 | The max value from conf/{all,interface}/rp_filter is used |
1189 | when doing source validation on the {interface}. | |
1da177e4 LT |
1190 | |
1191 | Default value is 0. Note that some distributions enable it | |
1192 | in startup scripts. | |
1193 | ||
1194 | arp_filter - BOOLEAN | |
1195 | 1 - Allows you to have multiple network interfaces on the same | |
1196 | subnet, and have the ARPs for each interface be answered | |
1197 | based on whether or not the kernel would route a packet from | |
1198 | the ARP'd IP out that interface (therefore you must use source | |
1199 | based routing for this to work). In other words it allows control | |
1200 | of which cards (usually 1) will respond to an arp request. | |
1201 | ||
1202 | 0 - (default) The kernel can respond to arp requests with addresses | |
1203 | from other interfaces. This may seem wrong but it usually makes | |
1204 | sense, because it increases the chance of successful communication. | |
1205 | IP addresses are owned by the complete host on Linux, not by | |
1206 | particular interfaces. Only for more complex setups like load- | |
1207 | balancing, does this behaviour cause problems. | |
1208 | ||
1209 | arp_filter for the interface will be enabled if at least one of | |
1210 | conf/{all,interface}/arp_filter is set to TRUE, | |
1211 | it will be disabled otherwise | |
1212 | ||
1213 | arp_announce - INTEGER | |
1214 | Define different restriction levels for announcing the local | |
1215 | source IP address from IP packets in ARP requests sent on | |
1216 | interface: | |
1217 | 0 - (default) Use any local address, configured on any interface | |
1218 | 1 - Try to avoid local addresses that are not in the target's | |
1219 | subnet for this interface. This mode is useful when target | |
1220 | hosts reachable via this interface require the source IP | |
1221 | address in ARP requests to be part of their logical network | |
1222 | configured on the receiving interface. When we generate the | |
1223 | request we will check all our subnets that include the | |
1224 | target IP and will preserve the source address if it is from | |
1225 | such subnet. If there is no such subnet we select source | |
1226 | address according to the rules for level 2. | |
1227 | 2 - Always use the best local address for this target. | |
1228 | In this mode we ignore the source address in the IP packet | |
1229 | and try to select local address that we prefer for talks with | |
1230 | the target host. Such local address is selected by looking | |
1231 | for primary IP addresses on all our subnets on the outgoing | |
1232 | interface that include the target IP address. If no suitable | |
1233 | local address is found we select the first local address | |
1234 | we have on the outgoing interface or on all other interfaces, | |
1235 | with the hope we will receive reply for our request and | |
1236 | even sometimes no matter the source IP address we announce. | |
1237 | ||
1238 | The max value from conf/{all,interface}/arp_announce is used. | |
1239 | ||
1240 | Increasing the restriction level gives more chance for | |
1241 | receiving answer from the resolved target while decreasing | |
1242 | the level announces more valid sender's information. | |
1243 | ||
1244 | arp_ignore - INTEGER | |
1245 | Define different modes for sending replies in response to | |
1246 | received ARP requests that resolve local target IP addresses: | |
1247 | 0 - (default): reply for any local target IP address, configured | |
1248 | on any interface | |
1249 | 1 - reply only if the target IP address is local address | |
1250 | configured on the incoming interface | |
1251 | 2 - reply only if the target IP address is local address | |
1252 | configured on the incoming interface and both with the | |
1253 | sender's IP address are part from same subnet on this interface | |
1254 | 3 - do not reply for local addresses configured with scope host, | |
1255 | only resolutions for global and link addresses are replied | |
1256 | 4-7 - reserved | |
1257 | 8 - do not reply for all local addresses | |
1258 | ||
1259 | The max value from conf/{all,interface}/arp_ignore is used | |
1260 | when ARP request is received on the {interface} | |
1261 | ||
eefef1cf SH |
1262 | arp_notify - BOOLEAN |
1263 | Define mode for notification of address and device changes. | |
1264 | 0 - (default): do nothing | |
3f8dc236 | 1265 | 1 - Generate gratuitous arp requests when device is brought up |
eefef1cf SH |
1266 | or hardware address changes. |
1267 | ||
c1b1bce8 | 1268 | arp_accept - BOOLEAN |
6d955180 OP |
1269 | Define behavior for gratuitous ARP frames who's IP is not |
1270 | already present in the ARP table: | |
1271 | 0 - don't create new entries in the ARP table | |
1272 | 1 - create new entries in the ARP table | |
1273 | ||
1274 | Both replies and requests type gratuitous arp will trigger the | |
1275 | ARP table to be updated, if this setting is on. | |
1276 | ||
1277 | If the ARP table already contains the IP address of the | |
1278 | gratuitous arp frame, the arp table will be updated regardless | |
1279 | if this setting is on or off. | |
1280 | ||
89c69d3c YH |
1281 | mcast_solicit - INTEGER |
1282 | The maximum number of multicast probes in INCOMPLETE state, | |
1283 | when the associated hardware address is unknown. Defaults | |
1284 | to 3. | |
1285 | ||
1286 | ucast_solicit - INTEGER | |
1287 | The maximum number of unicast probes in PROBE state, when | |
1288 | the hardware address is being reconfirmed. Defaults to 3. | |
c1b1bce8 | 1289 | |
1da177e4 LT |
1290 | app_solicit - INTEGER |
1291 | The maximum number of probes to send to the user space ARP daemon | |
1292 | via netlink before dropping back to multicast probes (see | |
89c69d3c YH |
1293 | mcast_resolicit). Defaults to 0. |
1294 | ||
1295 | mcast_resolicit - INTEGER | |
1296 | The maximum number of multicast probes after unicast and | |
1297 | app probes in PROBE state. Defaults to 0. | |
1da177e4 LT |
1298 | |
1299 | disable_policy - BOOLEAN | |
1300 | Disable IPSEC policy (SPD) for this interface | |
1301 | ||
1302 | disable_xfrm - BOOLEAN | |
1303 | Disable IPSEC encryption on this interface, whatever the policy | |
1304 | ||
fc4eba58 HFS |
1305 | igmpv2_unsolicited_report_interval - INTEGER |
1306 | The interval in milliseconds in which the next unsolicited | |
1307 | IGMPv1 or IGMPv2 report retransmit will take place. | |
1308 | Default: 10000 (10 seconds) | |
1da177e4 | 1309 | |
fc4eba58 HFS |
1310 | igmpv3_unsolicited_report_interval - INTEGER |
1311 | The interval in milliseconds in which the next unsolicited | |
1312 | IGMPv3 report retransmit will take place. | |
1313 | Default: 1000 (1 seconds) | |
1da177e4 | 1314 | |
d922e1cb MS |
1315 | promote_secondaries - BOOLEAN |
1316 | When a primary IP address is removed from this interface | |
1317 | promote a corresponding secondary IP address instead of | |
1318 | removing all the corresponding secondary IP addresses. | |
1319 | ||
12b74dfa JB |
1320 | drop_unicast_in_l2_multicast - BOOLEAN |
1321 | Drop any unicast IP packets that are received in link-layer | |
1322 | multicast (or broadcast) frames. | |
1323 | This behavior (for multicast) is actually a SHOULD in RFC | |
1324 | 1122, but is disabled by default for compatibility reasons. | |
1325 | Default: off (0) | |
1326 | ||
97daf331 JB |
1327 | drop_gratuitous_arp - BOOLEAN |
1328 | Drop all gratuitous ARP frames, for example if there's a known | |
1329 | good ARP proxy on the network and such frames need not be used | |
1330 | (or in the case of 802.11, must not be used to prevent attacks.) | |
1331 | Default: off (0) | |
1332 | ||
d922e1cb | 1333 | |
1da177e4 LT |
1334 | tag - INTEGER |
1335 | Allows you to write a number, which can be used as required. | |
1336 | Default value is 0. | |
1337 | ||
e69948a0 AD |
1338 | xfrm4_gc_thresh - INTEGER |
1339 | The threshold at which we will start garbage collecting for IPv4 | |
1340 | destination cache entries. At twice this value the system will | |
3c2a89dd | 1341 | refuse new allocations. |
e69948a0 | 1342 | |
87583ebb PD |
1343 | igmp_link_local_mcast_reports - BOOLEAN |
1344 | Enable IGMP reports for link local multicast groups in the | |
1345 | 224.0.0.X range. | |
1346 | Default TRUE | |
1347 | ||
1da177e4 LT |
1348 | Alexey Kuznetsov. |
1349 | kuznet@ms2.inr.ac.ru | |
1350 | ||
1351 | Updated by: | |
1352 | Andi Kleen | |
1353 | ak@muc.de | |
1354 | Nicolas Delon | |
1355 | delon.nicolas@wanadoo.fr | |
1356 | ||
1357 | ||
1358 | ||
1359 | ||
1360 | /proc/sys/net/ipv6/* Variables: | |
1361 | ||
1362 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
1363 | apply to IPv6 [XXX?]. | |
1364 | ||
1365 | bindv6only - BOOLEAN | |
1366 | Default value for IPV6_V6ONLY socket option, | |
e18f5feb | 1367 | which restricts use of the IPv6 socket to IPv6 communication |
1da177e4 LT |
1368 | only. |
1369 | TRUE: disable IPv4-mapped address feature | |
1370 | FALSE: enable IPv4-mapped address feature | |
1371 | ||
d5c073ca | 1372 | Default: FALSE (as specified in RFC3493) |
1da177e4 | 1373 | |
6444f72b FF |
1374 | flowlabel_consistency - BOOLEAN |
1375 | Protect the consistency (and unicity) of flow label. | |
1376 | You have to disable it to use IPV6_FL_F_REFLECT flag on the | |
1377 | flow label manager. | |
1378 | TRUE: enabled | |
1379 | FALSE: disabled | |
1380 | Default: TRUE | |
1381 | ||
42240901 TH |
1382 | auto_flowlabels - INTEGER |
1383 | Automatically generate flow labels based on a flow hash of the | |
1384 | packet. This allows intermediate devices, such as routers, to | |
1385 | identify packet flows for mechanisms like Equal Cost Multipath | |
cb1ce2ef | 1386 | Routing (see RFC 6438). |
42240901 TH |
1387 | 0: automatic flow labels are completely disabled |
1388 | 1: automatic flow labels are enabled by default, they can be | |
1389 | disabled on a per socket basis using the IPV6_AUTOFLOWLABEL | |
1390 | socket option | |
1391 | 2: automatic flow labels are allowed, they may be enabled on a | |
1392 | per socket basis using the IPV6_AUTOFLOWLABEL socket option | |
1393 | 3: automatic flow labels are enabled and enforced, they cannot | |
1394 | be disabled by the socket option | |
b5677416 | 1395 | Default: 1 |
cb1ce2ef | 1396 | |
82a584b7 TH |
1397 | flowlabel_state_ranges - BOOLEAN |
1398 | Split the flow label number space into two ranges. 0-0x7FFFF is | |
1399 | reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF | |
1400 | is reserved for stateless flow labels as described in RFC6437. | |
1401 | TRUE: enabled | |
1402 | FALSE: disabled | |
1403 | Default: true | |
1404 | ||
22b6722b JS |
1405 | flowlabel_reflect - BOOLEAN |
1406 | Automatically reflect the flow label. Needed for Path MTU | |
1407 | Discovery to work with Equal Cost Multipath Routing in anycast | |
1408 | environments. See RFC 7690 and: | |
1409 | https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01 | |
1410 | TRUE: enabled | |
1411 | FALSE: disabled | |
1412 | Default: FALSE | |
1413 | ||
b4bac172 DA |
1414 | fib_multipath_hash_policy - INTEGER |
1415 | Controls which hash policy to use for multipath routes. | |
1416 | Default: 0 (Layer 3) | |
1417 | Possible values: | |
1418 | 0 - Layer 3 (source and destination addresses plus flow label) | |
1419 | 1 - Layer 4 (standard 5-tuple) | |
1420 | ||
509aba3b FLB |
1421 | anycast_src_echo_reply - BOOLEAN |
1422 | Controls the use of anycast addresses as source addresses for ICMPv6 | |
1423 | echo reply | |
1424 | TRUE: enabled | |
1425 | FALSE: disabled | |
1426 | Default: FALSE | |
1427 | ||
9f0761c1 HFS |
1428 | idgen_delay - INTEGER |
1429 | Controls the delay in seconds after which time to retry | |
1430 | privacy stable address generation if a DAD conflict is | |
1431 | detected. | |
1432 | Default: 1 (as specified in RFC7217) | |
1433 | ||
1434 | idgen_retries - INTEGER | |
1435 | Controls the number of retries to generate a stable privacy | |
1436 | address if a DAD conflict is detected. | |
1437 | Default: 3 (as specified in RFC7217) | |
1438 | ||
2f711939 HFS |
1439 | mld_qrv - INTEGER |
1440 | Controls the MLD query robustness variable (see RFC3810 9.1). | |
1441 | Default: 2 (as specified by RFC3810 9.1) | |
1442 | Minimum: 1 (as specified by RFC6636 4.5) | |
1443 | ||
ab913455 | 1444 | max_dst_opts_number - INTEGER |
47d3d7ac TH |
1445 | Maximum number of non-padding TLVs allowed in a Destination |
1446 | options extension header. If this value is less than zero | |
1447 | then unknown options are disallowed and the number of known | |
1448 | TLVs allowed is the absolute value of this number. | |
1449 | Default: 8 | |
1450 | ||
ab913455 | 1451 | max_hbh_opts_number - INTEGER |
47d3d7ac TH |
1452 | Maximum number of non-padding TLVs allowed in a Hop-by-Hop |
1453 | options extension header. If this value is less than zero | |
1454 | then unknown options are disallowed and the number of known | |
1455 | TLVs allowed is the absolute value of this number. | |
1456 | Default: 8 | |
1457 | ||
ab913455 | 1458 | max_dst_opts_length - INTEGER |
47d3d7ac TH |
1459 | Maximum length allowed for a Destination options extension |
1460 | header. | |
1461 | Default: INT_MAX (unlimited) | |
1462 | ||
ab913455 | 1463 | max_hbh_length - INTEGER |
47d3d7ac TH |
1464 | Maximum length allowed for a Hop-by-Hop options extension |
1465 | header. | |
1466 | Default: INT_MAX (unlimited) | |
1467 | ||
7c6bb7d2 DA |
1468 | skip_notify_on_dev_down - BOOLEAN |
1469 | Controls whether an RTM_DELROUTE message is generated for routes | |
1470 | removed when a device is taken down or deleted. IPv4 does not | |
1471 | generate this message; IPv6 does by default. Setting this sysctl | |
1472 | to true skips the message, making IPv4 and IPv6 on par in relying | |
1473 | on userspace caches to track link events and evict routes. | |
1474 | Default: false (generate message) | |
1475 | ||
1da177e4 LT |
1476 | IPv6 Fragmentation: |
1477 | ||
1478 | ip6frag_high_thresh - INTEGER | |
e18f5feb | 1479 | Maximum memory used to reassemble IPv6 fragments. When |
1da177e4 LT |
1480 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
1481 | the fragment handler will toss packets until ip6frag_low_thresh | |
1482 | is reached. | |
e18f5feb | 1483 | |
1da177e4 | 1484 | ip6frag_low_thresh - INTEGER |
e18f5feb | 1485 | See ip6frag_high_thresh |
1da177e4 LT |
1486 | |
1487 | ip6frag_time - INTEGER | |
1488 | Time in seconds to keep an IPv6 fragment in memory. | |
1489 | ||
a6dc6670 AA |
1490 | IPv6 Segment Routing: |
1491 | ||
1492 | seg6_flowlabel - INTEGER | |
1493 | Controls the behaviour of computing the flowlabel of outer | |
1494 | IPv6 header in case of SR T.encaps | |
1495 | ||
1496 | -1 set flowlabel to zero. | |
1497 | 0 copy flowlabel from Inner packet in case of Inner IPv6 | |
1498 | (Set flowlabel to 0 in case IPv4/L2) | |
1499 | 1 Compute the flowlabel using seg6_make_flowlabel() | |
1500 | ||
1501 | Default is 0. | |
1502 | ||
1da177e4 LT |
1503 | conf/default/*: |
1504 | Change the interface-specific default settings. | |
1505 | ||
1506 | ||
1507 | conf/all/*: | |
e18f5feb | 1508 | Change all the interface-specific settings. |
1da177e4 LT |
1509 | |
1510 | [XXX: Other special features than forwarding?] | |
1511 | ||
1512 | conf/all/forwarding - BOOLEAN | |
e18f5feb | 1513 | Enable global IPv6 forwarding between all interfaces. |
1da177e4 | 1514 | |
e18f5feb | 1515 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
1da177e4 LT |
1516 | to control which interfaces may forward packets and which not. |
1517 | ||
e18f5feb | 1518 | This also sets all interfaces' Host/Router setting |
1da177e4 LT |
1519 | 'forwarding' to the specified value. See below for details. |
1520 | ||
1521 | This referred to as global forwarding. | |
1522 | ||
fbea49e1 YH |
1523 | proxy_ndp - BOOLEAN |
1524 | Do proxy ndp. | |
1525 | ||
219b5f29 LV |
1526 | fwmark_reflect - BOOLEAN |
1527 | Controls the fwmark of kernel-generated IPv6 reply packets that are not | |
1528 | associated with a socket for example, TCP RSTs or ICMPv6 echo replies). | |
1529 | If unset, these packets have a fwmark of zero. If set, they have the | |
1530 | fwmark of the packet they are replying to. | |
1531 | Default: 0 | |
1532 | ||
1da177e4 LT |
1533 | conf/interface/*: |
1534 | Change special settings per interface. | |
1535 | ||
e18f5feb | 1536 | The functional behaviour for certain settings is different |
1da177e4 LT |
1537 | depending on whether local forwarding is enabled or not. |
1538 | ||
605b91c8 | 1539 | accept_ra - INTEGER |
1da177e4 | 1540 | Accept Router Advertisements; autoconfigure using them. |
e18f5feb | 1541 | |
026359bc TA |
1542 | It also determines whether or not to transmit Router |
1543 | Solicitations. If and only if the functional setting is to | |
1544 | accept Router Advertisements, Router Solicitations will be | |
1545 | transmitted. | |
1546 | ||
ae8abfa0 TG |
1547 | Possible values are: |
1548 | 0 Do not accept Router Advertisements. | |
1549 | 1 Accept Router Advertisements if forwarding is disabled. | |
1550 | 2 Overrule forwarding behaviour. Accept Router Advertisements | |
1551 | even if forwarding is enabled. | |
1552 | ||
1da177e4 LT |
1553 | Functional default: enabled if local forwarding is disabled. |
1554 | disabled if local forwarding is enabled. | |
1555 | ||
65f5c7c1 YH |
1556 | accept_ra_defrtr - BOOLEAN |
1557 | Learn default router in Router Advertisement. | |
1558 | ||
1559 | Functional default: enabled if accept_ra is enabled. | |
1560 | disabled if accept_ra is disabled. | |
1561 | ||
d9333196 BG |
1562 | accept_ra_from_local - BOOLEAN |
1563 | Accept RA with source-address that is found on local machine | |
1564 | if the RA is otherwise proper and able to be accepted. | |
1565 | Default is to NOT accept these as it may be an un-intended | |
1566 | network loop. | |
1567 | ||
1568 | Functional default: | |
1569 | enabled if accept_ra_from_local is enabled | |
1570 | on a specific interface. | |
1571 | disabled if accept_ra_from_local is disabled | |
1572 | on a specific interface. | |
1573 | ||
8013d1d7 HL |
1574 | accept_ra_min_hop_limit - INTEGER |
1575 | Minimum hop limit Information in Router Advertisement. | |
1576 | ||
1577 | Hop limit Information in Router Advertisement less than this | |
1578 | variable shall be ignored. | |
1579 | ||
1580 | Default: 1 | |
1581 | ||
c4fd30eb | 1582 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 1583 | Learn Prefix Information in Router Advertisement. |
c4fd30eb YH |
1584 | |
1585 | Functional default: enabled if accept_ra is enabled. | |
1586 | disabled if accept_ra is disabled. | |
1587 | ||
bbea124b JS |
1588 | accept_ra_rt_info_min_plen - INTEGER |
1589 | Minimum prefix length of Route Information in RA. | |
1590 | ||
1591 | Route Information w/ prefix smaller than this variable shall | |
1592 | be ignored. | |
1593 | ||
1594 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
1595 | -1 if accept_ra_rtr_pref is disabled. | |
1596 | ||
09c884d4 YH |
1597 | accept_ra_rt_info_max_plen - INTEGER |
1598 | Maximum prefix length of Route Information in RA. | |
1599 | ||
bbea124b JS |
1600 | Route Information w/ prefix larger than this variable shall |
1601 | be ignored. | |
09c884d4 YH |
1602 | |
1603 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
1604 | -1 if accept_ra_rtr_pref is disabled. | |
1605 | ||
930d6ff2 YH |
1606 | accept_ra_rtr_pref - BOOLEAN |
1607 | Accept Router Preference in RA. | |
1608 | ||
1609 | Functional default: enabled if accept_ra is enabled. | |
1610 | disabled if accept_ra is disabled. | |
1611 | ||
c2943f14 HH |
1612 | accept_ra_mtu - BOOLEAN |
1613 | Apply the MTU value specified in RA option 5 (RFC4861). If | |
1614 | disabled, the MTU specified in the RA will be ignored. | |
1615 | ||
1616 | Functional default: enabled if accept_ra is enabled. | |
1617 | disabled if accept_ra is disabled. | |
1618 | ||
1da177e4 LT |
1619 | accept_redirects - BOOLEAN |
1620 | Accept Redirects. | |
1621 | ||
1622 | Functional default: enabled if local forwarding is disabled. | |
1623 | disabled if local forwarding is enabled. | |
1624 | ||
0bcbc926 YH |
1625 | accept_source_route - INTEGER |
1626 | Accept source routing (routing extension header). | |
1627 | ||
bb4dbf9e | 1628 | >= 0: Accept only routing header type 2. |
0bcbc926 YH |
1629 | < 0: Do not accept routing header. |
1630 | ||
1631 | Default: 0 | |
1632 | ||
1da177e4 | 1633 | autoconf - BOOLEAN |
e18f5feb | 1634 | Autoconfigure addresses using Prefix Information in Router |
1da177e4 LT |
1635 | Advertisements. |
1636 | ||
c4fd30eb YH |
1637 | Functional default: enabled if accept_ra_pinfo is enabled. |
1638 | disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
1639 | |
1640 | dad_transmits - INTEGER | |
1641 | The amount of Duplicate Address Detection probes to send. | |
1642 | Default: 1 | |
e18f5feb | 1643 | |
605b91c8 | 1644 | forwarding - INTEGER |
e18f5feb | 1645 | Configure interface-specific Host/Router behaviour. |
1da177e4 | 1646 | |
e18f5feb | 1647 | Note: It is recommended to have the same setting on all |
1da177e4 LT |
1648 | interfaces; mixed router/host scenarios are rather uncommon. |
1649 | ||
ae8abfa0 TG |
1650 | Possible values are: |
1651 | 0 Forwarding disabled | |
1652 | 1 Forwarding enabled | |
ae8abfa0 TG |
1653 | |
1654 | FALSE (0): | |
1da177e4 LT |
1655 | |
1656 | By default, Host behaviour is assumed. This means: | |
1657 | ||
1658 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
026359bc TA |
1659 | 2. If accept_ra is TRUE (default), transmit Router |
1660 | Solicitations. | |
e18f5feb | 1661 | 3. If accept_ra is TRUE (default), accept Router |
1da177e4 LT |
1662 | Advertisements (and do autoconfiguration). |
1663 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
1664 | ||
ae8abfa0 | 1665 | TRUE (1): |
1da177e4 | 1666 | |
e18f5feb | 1667 | If local forwarding is enabled, Router behaviour is assumed. |
1da177e4 LT |
1668 | This means exactly the reverse from the above: |
1669 | ||
1670 | 1. IsRouter flag is set in Neighbour Advertisements. | |
026359bc | 1671 | 2. Router Solicitations are not sent unless accept_ra is 2. |
ae8abfa0 | 1672 | 3. Router Advertisements are ignored unless accept_ra is 2. |
1da177e4 LT |
1673 | 4. Redirects are ignored. |
1674 | ||
ae8abfa0 TG |
1675 | Default: 0 (disabled) if global forwarding is disabled (default), |
1676 | otherwise 1 (enabled). | |
1da177e4 LT |
1677 | |
1678 | hop_limit - INTEGER | |
1679 | Default Hop Limit to set. | |
1680 | Default: 64 | |
1681 | ||
1682 | mtu - INTEGER | |
1683 | Default Maximum Transfer Unit | |
1684 | Default: 1280 (IPv6 required minimum) | |
1685 | ||
35a256fe TH |
1686 | ip_nonlocal_bind - BOOLEAN |
1687 | If set, allows processes to bind() to non-local IPv6 addresses, | |
1688 | which can be quite useful - but may break some applications. | |
1689 | Default: 0 | |
1690 | ||
52e16356 YH |
1691 | router_probe_interval - INTEGER |
1692 | Minimum interval (in seconds) between Router Probing described | |
1693 | in RFC4191. | |
1694 | ||
1695 | Default: 60 | |
1696 | ||
1da177e4 LT |
1697 | router_solicitation_delay - INTEGER |
1698 | Number of seconds to wait after interface is brought up | |
1699 | before sending Router Solicitations. | |
1700 | Default: 1 | |
1701 | ||
1702 | router_solicitation_interval - INTEGER | |
1703 | Number of seconds to wait between Router Solicitations. | |
1704 | Default: 4 | |
1705 | ||
1706 | router_solicitations - INTEGER | |
e18f5feb | 1707 | Number of Router Solicitations to send until assuming no |
1da177e4 LT |
1708 | routers are present. |
1709 | Default: 3 | |
1710 | ||
3985e8a3 EK |
1711 | use_oif_addrs_only - BOOLEAN |
1712 | When enabled, the candidate source addresses for destinations | |
1713 | routed via this interface are restricted to the set of addresses | |
1714 | configured on this interface (vis. RFC 6724, section 4). | |
1715 | ||
1716 | Default: false | |
1717 | ||
1da177e4 LT |
1718 | use_tempaddr - INTEGER |
1719 | Preference for Privacy Extensions (RFC3041). | |
1720 | <= 0 : disable Privacy Extensions | |
1721 | == 1 : enable Privacy Extensions, but prefer public | |
1722 | addresses over temporary addresses. | |
1723 | > 1 : enable Privacy Extensions and prefer temporary | |
1724 | addresses over public addresses. | |
1725 | Default: 0 (for most devices) | |
1726 | -1 (for point-to-point devices and loopback devices) | |
1727 | ||
1728 | temp_valid_lft - INTEGER | |
1729 | valid lifetime (in seconds) for temporary addresses. | |
1730 | Default: 604800 (7 days) | |
1731 | ||
1732 | temp_prefered_lft - INTEGER | |
1733 | Preferred lifetime (in seconds) for temporary addresses. | |
1734 | Default: 86400 (1 day) | |
1735 | ||
f1705ec1 DA |
1736 | keep_addr_on_down - INTEGER |
1737 | Keep all IPv6 addresses on an interface down event. If set static | |
1738 | global addresses with no expiration time are not flushed. | |
1739 | >0 : enabled | |
1740 | 0 : system default | |
1741 | <0 : disabled | |
1742 | ||
1743 | Default: 0 (addresses are removed) | |
1744 | ||
1da177e4 LT |
1745 | max_desync_factor - INTEGER |
1746 | Maximum value for DESYNC_FACTOR, which is a random value | |
e18f5feb | 1747 | that ensures that clients don't synchronize with each |
1da177e4 LT |
1748 | other and generate new addresses at exactly the same time. |
1749 | value is in seconds. | |
1750 | Default: 600 | |
e18f5feb | 1751 | |
1da177e4 LT |
1752 | regen_max_retry - INTEGER |
1753 | Number of attempts before give up attempting to generate | |
1754 | valid temporary addresses. | |
1755 | Default: 5 | |
1756 | ||
1757 | max_addresses - INTEGER | |
e79dc484 BH |
1758 | Maximum number of autoconfigured addresses per interface. Setting |
1759 | to zero disables the limitation. It is not recommended to set this | |
1760 | value too large (or to zero) because it would be an easy way to | |
1761 | crash the kernel by allowing too many addresses to be created. | |
1da177e4 LT |
1762 | Default: 16 |
1763 | ||
778d80be | 1764 | disable_ipv6 - BOOLEAN |
9bdd8d40 BH |
1765 | Disable IPv6 operation. If accept_dad is set to 2, this value |
1766 | will be dynamically set to TRUE if DAD fails for the link-local | |
1767 | address. | |
778d80be YH |
1768 | Default: FALSE (enable IPv6 operation) |
1769 | ||
56d417b1 BH |
1770 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
1771 | it will dynamically create a link-local address on the given | |
1772 | interface and start Duplicate Address Detection, if necessary. | |
1773 | ||
1774 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
2f0aaf7f LB |
1775 | it will dynamically delete all addresses and routes on the given |
1776 | interface. From now on it will not possible to add addresses/routes | |
1777 | to the selected interface. | |
56d417b1 | 1778 | |
1b34be74 YH |
1779 | accept_dad - INTEGER |
1780 | Whether to accept DAD (Duplicate Address Detection). | |
1781 | 0: Disable DAD | |
1782 | 1: Enable DAD (default) | |
1783 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
1784 | link-local address has been found. | |
1785 | ||
35e015e1 MC |
1786 | DAD operation and mode on a given interface will be selected according |
1787 | to the maximum value of conf/{all,interface}/accept_dad. | |
1788 | ||
f7734fdf OP |
1789 | force_tllao - BOOLEAN |
1790 | Enable sending the target link-layer address option even when | |
1791 | responding to a unicast neighbor solicitation. | |
1792 | Default: FALSE | |
1793 | ||
1794 | Quoting from RFC 2461, section 4.4, Target link-layer address: | |
1795 | ||
1796 | "The option MUST be included for multicast solicitations in order to | |
1797 | avoid infinite Neighbor Solicitation "recursion" when the peer node | |
1798 | does not have a cache entry to return a Neighbor Advertisements | |
1799 | message. When responding to unicast solicitations, the option can be | |
1800 | omitted since the sender of the solicitation has the correct link- | |
1801 | layer address; otherwise it would not have be able to send the unicast | |
1802 | solicitation in the first place. However, including the link-layer | |
1803 | address in this case adds little overhead and eliminates a potential | |
1804 | race condition where the sender deletes the cached link-layer address | |
1805 | prior to receiving a response to a previous solicitation." | |
1806 | ||
db2b620a HFS |
1807 | ndisc_notify - BOOLEAN |
1808 | Define mode for notification of address and device changes. | |
1809 | 0 - (default): do nothing | |
1810 | 1 - Generate unsolicited neighbour advertisements when device is brought | |
1811 | up or hardware address changes. | |
1812 | ||
2210d6b2 MŻ |
1813 | ndisc_tclass - INTEGER |
1814 | The IPv6 Traffic Class to use by default when sending IPv6 Neighbor | |
1815 | Discovery (Router Solicitation, Router Advertisement, Neighbor | |
1816 | Solicitation, Neighbor Advertisement, Redirect) messages. | |
1817 | These 8 bits can be interpreted as 6 high order bits holding the DSCP | |
1818 | value and 2 low order bits representing ECN (which you probably want | |
1819 | to leave cleared). | |
1820 | 0 - (default) | |
1821 | ||
fc4eba58 HFS |
1822 | mldv1_unsolicited_report_interval - INTEGER |
1823 | The interval in milliseconds in which the next unsolicited | |
1824 | MLDv1 report retransmit will take place. | |
1825 | Default: 10000 (10 seconds) | |
1826 | ||
1827 | mldv2_unsolicited_report_interval - INTEGER | |
1828 | The interval in milliseconds in which the next unsolicited | |
1829 | MLDv2 report retransmit will take place. | |
1830 | Default: 1000 (1 second) | |
1831 | ||
f2127810 DB |
1832 | force_mld_version - INTEGER |
1833 | 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed | |
1834 | 1 - Enforce to use MLD version 1 | |
1835 | 2 - Enforce to use MLD version 2 | |
1836 | ||
b800c3b9 HFS |
1837 | suppress_frag_ndisc - INTEGER |
1838 | Control RFC 6980 (Security Implications of IPv6 Fragmentation | |
1839 | with IPv6 Neighbor Discovery) behavior: | |
1840 | 1 - (default) discard fragmented neighbor discovery packets | |
1841 | 0 - allow fragmented neighbor discovery packets | |
1842 | ||
7fd2561e EK |
1843 | optimistic_dad - BOOLEAN |
1844 | Whether to perform Optimistic Duplicate Address Detection (RFC 4429). | |
35e015e1 MC |
1845 | 0: disabled (default) |
1846 | 1: enabled | |
1847 | ||
1848 | Optimistic Duplicate Address Detection for the interface will be enabled | |
1849 | if at least one of conf/{all,interface}/optimistic_dad is set to 1, | |
1850 | it will be disabled otherwise. | |
7fd2561e EK |
1851 | |
1852 | use_optimistic - BOOLEAN | |
1853 | If enabled, do not classify optimistic addresses as deprecated during | |
1854 | source address selection. Preferred addresses will still be chosen | |
1855 | before optimistic addresses, subject to other ranking in the source | |
1856 | address selection algorithm. | |
35e015e1 MC |
1857 | 0: disabled (default) |
1858 | 1: enabled | |
1859 | ||
1860 | This will be enabled if at least one of | |
1861 | conf/{all,interface}/use_optimistic is set to 1, disabled otherwise. | |
7fd2561e | 1862 | |
9f0761c1 HFS |
1863 | stable_secret - IPv6 address |
1864 | This IPv6 address will be used as a secret to generate IPv6 | |
1865 | addresses for link-local addresses and autoconfigured | |
1866 | ones. All addresses generated after setting this secret will | |
1867 | be stable privacy ones by default. This can be changed via the | |
1868 | addrgenmode ip-link. conf/default/stable_secret is used as the | |
1869 | secret for the namespace, the interface specific ones can | |
1870 | overwrite that. Writes to conf/all/stable_secret are refused. | |
1871 | ||
1872 | It is recommended to generate this secret during installation | |
1873 | of a system and keep it stable after that. | |
1874 | ||
1875 | By default the stable secret is unset. | |
1876 | ||
f168db5e SD |
1877 | addr_gen_mode - INTEGER |
1878 | Defines how link-local and autoconf addresses are generated. | |
1879 | ||
1880 | 0: generate address based on EUI64 (default) | |
1881 | 1: do no generate a link-local address, use EUI64 for addresses generated | |
1882 | from autoconf | |
1883 | 2: generate stable privacy addresses, using the secret from | |
1884 | stable_secret (RFC7217) | |
1885 | 3: generate stable privacy addresses, using a random secret if unset | |
1886 | ||
abbc3043 JB |
1887 | drop_unicast_in_l2_multicast - BOOLEAN |
1888 | Drop any unicast IPv6 packets that are received in link-layer | |
1889 | multicast (or broadcast) frames. | |
1890 | ||
1891 | By default this is turned off. | |
1892 | ||
7a02bf89 JB |
1893 | drop_unsolicited_na - BOOLEAN |
1894 | Drop all unsolicited neighbor advertisements, for example if there's | |
1895 | a known good NA proxy on the network and such frames need not be used | |
1896 | (or in the case of 802.11, must not be used to prevent attacks.) | |
1897 | ||
1898 | By default this is turned off. | |
1899 | ||
adc176c5 EN |
1900 | enhanced_dad - BOOLEAN |
1901 | Include a nonce option in the IPv6 neighbor solicitation messages used for | |
1902 | duplicate address detection per RFC7527. A received DAD NS will only signal | |
1903 | a duplicate address if the nonce is different. This avoids any false | |
1904 | detection of duplicates due to loopback of the NS messages that we send. | |
1905 | The nonce option will be sent on an interface unless both of | |
1906 | conf/{all,interface}/enhanced_dad are set to FALSE. | |
1907 | Default: TRUE | |
1908 | ||
1da177e4 LT |
1909 | icmp/*: |
1910 | ratelimit - INTEGER | |
1911 | Limit the maximal rates for sending ICMPv6 packets. | |
6dbf4bca SH |
1912 | 0 to disable any limiting, |
1913 | otherwise the minimal space between responses in milliseconds. | |
1914 | Default: 1000 | |
1da177e4 | 1915 | |
e6f86b0f VJ |
1916 | echo_ignore_all - BOOLEAN |
1917 | If set non-zero, then the kernel will ignore all ICMP ECHO | |
1918 | requests sent to it over the IPv6 protocol. | |
1919 | Default: 0 | |
1920 | ||
e69948a0 AD |
1921 | xfrm6_gc_thresh - INTEGER |
1922 | The threshold at which we will start garbage collecting for IPv6 | |
1923 | destination cache entries. At twice this value the system will | |
3c2a89dd | 1924 | refuse new allocations. |
e69948a0 | 1925 | |
1da177e4 LT |
1926 | |
1927 | IPv6 Update by: | |
1928 | Pekka Savola <pekkas@netcore.fi> | |
1929 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
1930 | ||
1931 | ||
1932 | /proc/sys/net/bridge/* Variables: | |
1933 | ||
1934 | bridge-nf-call-arptables - BOOLEAN | |
1935 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
1936 | 0 : disable this. | |
1937 | Default: 1 | |
1938 | ||
1939 | bridge-nf-call-iptables - BOOLEAN | |
1940 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
1941 | 0 : disable this. | |
1942 | Default: 1 | |
1943 | ||
1944 | bridge-nf-call-ip6tables - BOOLEAN | |
1945 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
1946 | 0 : disable this. | |
1947 | Default: 1 | |
1948 | ||
1949 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
516299d2 MM |
1950 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
1951 | 0 : disable this. | |
4981682c | 1952 | Default: 0 |
516299d2 MM |
1953 | |
1954 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1955 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. | |
1da177e4 | 1956 | 0 : disable this. |
4981682c | 1957 | Default: 0 |
1da177e4 | 1958 | |
4981682c PNA |
1959 | bridge-nf-pass-vlan-input-dev - BOOLEAN |
1960 | 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan | |
1961 | interface on the bridge and set the netfilter input device to the vlan. | |
1962 | This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT | |
1963 | target work with vlan-on-top-of-bridge interfaces. When no matching | |
1964 | vlan interface is found, or this switch is off, the input device is | |
1965 | set to the bridge interface. | |
1966 | 0: disable bridge netfilter vlan interface lookup. | |
1967 | Default: 0 | |
1da177e4 | 1968 | |
32e8d494 VY |
1969 | proc/sys/net/sctp/* Variables: |
1970 | ||
1971 | addip_enable - BOOLEAN | |
1972 | Enable or disable extension of Dynamic Address Reconfiguration | |
1973 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
1974 | the ability to dynamically add and remove new addresses for the SCTP | |
1975 | associations. | |
1976 | ||
1977 | 1: Enable extension. | |
1978 | ||
1979 | 0: Disable extension. | |
1980 | ||
1981 | Default: 0 | |
1982 | ||
566178f8 ZY |
1983 | pf_enable - INTEGER |
1984 | Enable or disable pf (pf is short for potentially failed) state. A value | |
1985 | of pf_retrans > path_max_retrans also disables pf state. That is, one of | |
1986 | both pf_enable and pf_retrans > path_max_retrans can disable pf state. | |
1987 | Since pf_retrans and path_max_retrans can be changed by userspace | |
1988 | application, sometimes user expects to disable pf state by the value of | |
1989 | pf_retrans > path_max_retrans, but occasionally the value of pf_retrans | |
1990 | or path_max_retrans is changed by the user application, this pf state is | |
1991 | enabled. As such, it is necessary to add this to dynamically enable | |
1992 | and disable pf state. See: | |
1993 | https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for | |
1994 | details. | |
1995 | ||
1996 | 1: Enable pf. | |
1997 | ||
1998 | 0: Disable pf. | |
1999 | ||
2000 | Default: 1 | |
2001 | ||
32e8d494 VY |
2002 | addip_noauth_enable - BOOLEAN |
2003 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
2004 | authentication to protect the operations of adding or removing new | |
2005 | addresses. This requirement is mandated so that unauthorized hosts | |
2006 | would not be able to hijack associations. However, older | |
2007 | implementations may not have implemented this requirement while | |
2008 | allowing the ADD-IP extension. For reasons of interoperability, | |
2009 | we provide this variable to control the enforcement of the | |
2010 | authentication requirement. | |
2011 | ||
2012 | 1: Allow ADD-IP extension to be used without authentication. This | |
2013 | should only be set in a closed environment for interoperability | |
2014 | with older implementations. | |
2015 | ||
2016 | 0: Enforce the authentication requirement | |
2017 | ||
2018 | Default: 0 | |
2019 | ||
2020 | auth_enable - BOOLEAN | |
2021 | Enable or disable Authenticated Chunks extension. This extension | |
2022 | provides the ability to send and receive authenticated chunks and is | |
2023 | required for secure operation of Dynamic Address Reconfiguration | |
2024 | (ADD-IP) extension. | |
2025 | ||
2026 | 1: Enable this extension. | |
2027 | 0: Disable this extension. | |
2028 | ||
2029 | Default: 0 | |
2030 | ||
2031 | prsctp_enable - BOOLEAN | |
2032 | Enable or disable the Partial Reliability extension (RFC3758) which | |
2033 | is used to notify peers that a given DATA should no longer be expected. | |
2034 | ||
2035 | 1: Enable extension | |
2036 | 0: Disable | |
2037 | ||
2038 | Default: 1 | |
2039 | ||
2040 | max_burst - INTEGER | |
2041 | The limit of the number of new packets that can be initially sent. It | |
2042 | controls how bursty the generated traffic can be. | |
2043 | ||
2044 | Default: 4 | |
2045 | ||
2046 | association_max_retrans - INTEGER | |
2047 | Set the maximum number for retransmissions that an association can | |
2048 | attempt deciding that the remote end is unreachable. If this value | |
2049 | is exceeded, the association is terminated. | |
2050 | ||
2051 | Default: 10 | |
2052 | ||
2053 | max_init_retransmits - INTEGER | |
2054 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
2055 | that an association will attempt before declaring the destination | |
2056 | unreachable and terminating. | |
2057 | ||
2058 | Default: 8 | |
2059 | ||
2060 | path_max_retrans - INTEGER | |
2061 | The maximum number of retransmissions that will be attempted on a given | |
2062 | path. Once this threshold is exceeded, the path is considered | |
2063 | unreachable, and new traffic will use a different path when the | |
2064 | association is multihomed. | |
2065 | ||
2066 | Default: 5 | |
2067 | ||
5aa93bcf NH |
2068 | pf_retrans - INTEGER |
2069 | The number of retransmissions that will be attempted on a given path | |
2070 | before traffic is redirected to an alternate transport (should one | |
2071 | exist). Note this is distinct from path_max_retrans, as a path that | |
2072 | passes the pf_retrans threshold can still be used. Its only | |
2073 | deprioritized when a transmission path is selected by the stack. This | |
2074 | setting is primarily used to enable fast failover mechanisms without | |
2075 | having to reduce path_max_retrans to a very low value. See: | |
2076 | http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt | |
2077 | for details. Note also that a value of pf_retrans > path_max_retrans | |
566178f8 ZY |
2078 | disables this feature. Since both pf_retrans and path_max_retrans can |
2079 | be changed by userspace application, a variable pf_enable is used to | |
2080 | disable pf state. | |
5aa93bcf NH |
2081 | |
2082 | Default: 0 | |
2083 | ||
32e8d494 VY |
2084 | rto_initial - INTEGER |
2085 | The initial round trip timeout value in milliseconds that will be used | |
2086 | in calculating round trip times. This is the initial time interval | |
2087 | for retransmissions. | |
2088 | ||
2089 | Default: 3000 | |
1da177e4 | 2090 | |
32e8d494 VY |
2091 | rto_max - INTEGER |
2092 | The maximum value (in milliseconds) of the round trip timeout. This | |
2093 | is the largest time interval that can elapse between retransmissions. | |
2094 | ||
2095 | Default: 60000 | |
2096 | ||
2097 | rto_min - INTEGER | |
2098 | The minimum value (in milliseconds) of the round trip timeout. This | |
2099 | is the smallest time interval the can elapse between retransmissions. | |
2100 | ||
2101 | Default: 1000 | |
2102 | ||
2103 | hb_interval - INTEGER | |
2104 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
2105 | are sent at the specified interval on idle paths to probe the state of | |
2106 | a given path between 2 associations. | |
2107 | ||
2108 | Default: 30000 | |
2109 | ||
2110 | sack_timeout - INTEGER | |
2111 | The amount of time (in milliseconds) that the implementation will wait | |
2112 | to send a SACK. | |
2113 | ||
2114 | Default: 200 | |
2115 | ||
2116 | valid_cookie_life - INTEGER | |
2117 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
2118 | is used during association establishment. | |
2119 | ||
2120 | Default: 60000 | |
2121 | ||
2122 | cookie_preserve_enable - BOOLEAN | |
2123 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
2124 | that is used during the establishment phase of SCTP association | |
2125 | ||
2126 | 1: Enable cookie lifetime extension. | |
2127 | 0: Disable | |
2128 | ||
2129 | Default: 1 | |
2130 | ||
3c68198e NH |
2131 | cookie_hmac_alg - STRING |
2132 | Select the hmac algorithm used when generating the cookie value sent by | |
2133 | a listening sctp socket to a connecting client in the INIT-ACK chunk. | |
2134 | Valid values are: | |
2135 | * md5 | |
2136 | * sha1 | |
2137 | * none | |
2138 | Ability to assign md5 or sha1 as the selected alg is predicated on the | |
3b09adcb | 2139 | configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and |
3c68198e NH |
2140 | CONFIG_CRYPTO_SHA1). |
2141 | ||
2142 | Default: Dependent on configuration. MD5 if available, else SHA1 if | |
2143 | available, else none. | |
2144 | ||
32e8d494 VY |
2145 | rcvbuf_policy - INTEGER |
2146 | Determines if the receive buffer is attributed to the socket or to | |
2147 | association. SCTP supports the capability to create multiple | |
2148 | associations on a single socket. When using this capability, it is | |
2149 | possible that a single stalled association that's buffering a lot | |
2150 | of data may block other associations from delivering their data by | |
2151 | consuming all of the receive buffer space. To work around this, | |
2152 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
2153 | to each association instead of the socket. This prevents the described | |
2154 | blocking. | |
2155 | ||
2156 | 1: rcvbuf space is per association | |
3b09adcb | 2157 | 0: rcvbuf space is per socket |
32e8d494 VY |
2158 | |
2159 | Default: 0 | |
2160 | ||
2161 | sndbuf_policy - INTEGER | |
2162 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
2163 | ||
2164 | 1: Send buffer is tracked per association | |
2165 | 0: Send buffer is tracked per socket. | |
2166 | ||
2167 | Default: 0 | |
2168 | ||
2169 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
2170 | Number of pages allowed for queueing by all SCTP sockets. | |
2171 | ||
2172 | min: Below this number of pages SCTP is not bothered about its | |
2173 | memory appetite. When amount of memory allocated by SCTP exceeds | |
2174 | this number, SCTP starts to moderate memory usage. | |
2175 | ||
2176 | pressure: This value was introduced to follow format of tcp_mem. | |
2177 | ||
2178 | max: Number of pages allowed for queueing by all SCTP sockets. | |
2179 | ||
2180 | Default is calculated at boot time from amount of available memory. | |
2181 | ||
2182 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b MM |
2183 | Only the first value ("min") is used, "default" and "max" are |
2184 | ignored. | |
2185 | ||
2186 | min: Minimal size of receive buffer used by SCTP socket. | |
2187 | It is guaranteed to each SCTP socket (but not association) even | |
2188 | under moderate memory pressure. | |
2189 | ||
320bd6de | 2190 | Default: 4K |
32e8d494 VY |
2191 | |
2192 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b | 2193 | Currently this tunable has no effect. |
32e8d494 | 2194 | |
72388433 BD |
2195 | addr_scope_policy - INTEGER |
2196 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 | |
2197 | ||
2198 | 0 - Disable IPv4 address scoping | |
2199 | 1 - Enable IPv4 address scoping | |
2200 | 2 - Follow draft but allow IPv4 private addresses | |
2201 | 3 - Follow draft but allow IPv4 link local addresses | |
2202 | ||
2203 | Default: 1 | |
2204 | ||
1da177e4 | 2205 | |
4edc2f34 | 2206 | /proc/sys/net/core/* |
c60f6aa8 | 2207 | Please see: Documentation/sysctl/net.txt for descriptions of these entries. |
705efc3b | 2208 | |
4edc2f34 SH |
2209 | |
2210 | /proc/sys/net/unix/* | |
705efc3b WT |
2211 | max_dgram_qlen - INTEGER |
2212 | The maximum length of dgram socket receive queue | |
2213 | ||
2214 | Default: 10 | |
2215 |