Commit | Line | Data |
---|---|---|
09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
7c106d7e WHSE |
2 | /* |
3 | * TCP Low Priority (TCP-LP) | |
4 | * | |
5 | * TCP Low Priority is a distributed algorithm whose goal is to utilize only | |
6 | * the excess network bandwidth as compared to the ``fair share`` of | |
3795da47 | 7 | * bandwidth as targeted by TCP. |
7c106d7e | 8 | * |
7c106d7e WHSE |
9 | * As of 2.6.13, Linux supports pluggable congestion control algorithms. |
10 | * Due to the limitation of the API, we take the following changes from | |
11 | * the original TCP-LP implementation: | |
12 | * o We use newReno in most core CA handling. Only add some checking | |
13 | * within cong_avoid. | |
14 | * o Error correcting in remote HZ, therefore remote HZ will be keeped | |
15 | * on checking and updating. | |
25985edc | 16 | * o Handling calculation of One-Way-Delay (OWD) within rtt_sample, since |
7c106d7e WHSE |
17 | * OWD have a similar meaning as RTT. Also correct the buggy formular. |
18 | * o Handle reaction for Early Congestion Indication (ECI) within | |
19 | * pkts_acked, as mentioned within pseudo code. | |
20 | * o OWD is handled in relative format, where local time stamp will in | |
21 | * tcp_time_stamp format. | |
22 | * | |
3795da47 WHSE |
23 | * Original Author: |
24 | * Aleksandar Kuzmanovic <akuzma@northwestern.edu> | |
25 | * Available from: | |
26 | * http://www.ece.rice.edu/~akuzma/Doc/akuzma/TCP-LP.pdf | |
27 | * Original implementation for 2.4.19: | |
28 | * http://www-ece.rice.edu/networks/TCP-LP/ | |
7c106d7e | 29 | * |
3795da47 WHSE |
30 | * 2.6.x module Authors: |
31 | * Wong Hoi Sing, Edison <hswong3i@gmail.com> | |
32 | * Hung Hing Lun, Mike <hlhung3i@gmail.com> | |
33 | * SourceForge project page: | |
34 | * http://tcp-lp-mod.sourceforge.net/ | |
7c106d7e WHSE |
35 | */ |
36 | ||
7c106d7e WHSE |
37 | #include <linux/module.h> |
38 | #include <net/tcp.h> | |
39 | ||
40 | /* resolution of owd */ | |
9a568de4 | 41 | #define LP_RESOL TCP_TS_HZ |
7c106d7e WHSE |
42 | |
43 | /** | |
44 | * enum tcp_lp_state | |
45 | * @LP_VALID_RHZ: is remote HZ valid? | |
46 | * @LP_VALID_OWD: is OWD valid? | |
47 | * @LP_WITHIN_THR: are we within threshold? | |
48 | * @LP_WITHIN_INF: are we within inference? | |
49 | * | |
50 | * TCP-LP's state flags. | |
51 | * We create this set of state flag mainly for debugging. | |
52 | */ | |
53 | enum tcp_lp_state { | |
54 | LP_VALID_RHZ = (1 << 0), | |
55 | LP_VALID_OWD = (1 << 1), | |
56 | LP_WITHIN_THR = (1 << 3), | |
57 | LP_WITHIN_INF = (1 << 4), | |
58 | }; | |
59 | ||
60 | /** | |
61 | * struct lp | |
62 | * @flag: TCP-LP state flag | |
63 | * @sowd: smoothed OWD << 3 | |
64 | * @owd_min: min OWD | |
65 | * @owd_max: max OWD | |
e5ca43e8 | 66 | * @owd_max_rsv: reserved max owd |
7c106d7e WHSE |
67 | * @remote_hz: estimated remote HZ |
68 | * @remote_ref_time: remote reference time | |
69 | * @local_ref_time: local reference time | |
70 | * @last_drop: time for last active drop | |
71 | * @inference: current inference | |
72 | * | |
73 | * TCP-LP's private struct. | |
74 | * We get the idea from original TCP-LP implementation where only left those we | |
75 | * found are really useful. | |
76 | */ | |
77 | struct lp { | |
78 | u32 flag; | |
79 | u32 sowd; | |
80 | u32 owd_min; | |
81 | u32 owd_max; | |
82 | u32 owd_max_rsv; | |
83 | u32 remote_hz; | |
84 | u32 remote_ref_time; | |
85 | u32 local_ref_time; | |
86 | u32 last_drop; | |
87 | u32 inference; | |
88 | }; | |
89 | ||
90 | /** | |
91 | * tcp_lp_init | |
726e5e49 | 92 | * @sk: socket to initialize congestion control algorithm for |
7c106d7e WHSE |
93 | * |
94 | * Init all required variables. | |
95 | * Clone the handling from Vegas module implementation. | |
96 | */ | |
97 | static void tcp_lp_init(struct sock *sk) | |
98 | { | |
99 | struct lp *lp = inet_csk_ca(sk); | |
100 | ||
101 | lp->flag = 0; | |
102 | lp->sowd = 0; | |
103 | lp->owd_min = 0xffffffff; | |
104 | lp->owd_max = 0; | |
105 | lp->owd_max_rsv = 0; | |
106 | lp->remote_hz = 0; | |
107 | lp->remote_ref_time = 0; | |
108 | lp->local_ref_time = 0; | |
109 | lp->last_drop = 0; | |
110 | lp->inference = 0; | |
111 | } | |
112 | ||
113 | /** | |
114 | * tcp_lp_cong_avoid | |
726e5e49 | 115 | * @sk: socket to avoid congesting |
7c106d7e WHSE |
116 | * |
117 | * Implementation of cong_avoid. | |
118 | * Will only call newReno CA when away from inference. | |
119 | * From TCP-LP's paper, this will be handled in additive increasement. | |
120 | */ | |
24901551 | 121 | static void tcp_lp_cong_avoid(struct sock *sk, u32 ack, u32 acked) |
7c106d7e WHSE |
122 | { |
123 | struct lp *lp = inet_csk_ca(sk); | |
124 | ||
125 | if (!(lp->flag & LP_WITHIN_INF)) | |
24901551 | 126 | tcp_reno_cong_avoid(sk, ack, acked); |
7c106d7e WHSE |
127 | } |
128 | ||
129 | /** | |
130 | * tcp_lp_remote_hz_estimator | |
726e5e49 | 131 | * @sk: socket which needs an estimate for the remote HZs |
7c106d7e WHSE |
132 | * |
133 | * Estimate remote HZ. | |
134 | * We keep on updating the estimated value, where original TCP-LP | |
135 | * implementation only guest it for once and use forever. | |
136 | */ | |
137 | static u32 tcp_lp_remote_hz_estimator(struct sock *sk) | |
138 | { | |
139 | struct tcp_sock *tp = tcp_sk(sk); | |
140 | struct lp *lp = inet_csk_ca(sk); | |
141 | s64 rhz = lp->remote_hz << 6; /* remote HZ << 6 */ | |
142 | s64 m = 0; | |
143 | ||
144 | /* not yet record reference time | |
145 | * go away!! record it before come back!! */ | |
146 | if (lp->remote_ref_time == 0 || lp->local_ref_time == 0) | |
147 | goto out; | |
148 | ||
149 | /* we can't calc remote HZ with no different!! */ | |
9d4fb27d JP |
150 | if (tp->rx_opt.rcv_tsval == lp->remote_ref_time || |
151 | tp->rx_opt.rcv_tsecr == lp->local_ref_time) | |
7c106d7e WHSE |
152 | goto out; |
153 | ||
9a568de4 ED |
154 | m = TCP_TS_HZ * |
155 | (tp->rx_opt.rcv_tsval - lp->remote_ref_time) / | |
156 | (tp->rx_opt.rcv_tsecr - lp->local_ref_time); | |
7c106d7e WHSE |
157 | if (m < 0) |
158 | m = -m; | |
159 | ||
3795da47 | 160 | if (rhz > 0) { |
7c106d7e WHSE |
161 | m -= rhz >> 6; /* m is now error in remote HZ est */ |
162 | rhz += m; /* 63/64 old + 1/64 new */ | |
163 | } else | |
164 | rhz = m << 6; | |
165 | ||
3795da47 | 166 | out: |
7c106d7e | 167 | /* record time for successful remote HZ calc */ |
bfbea8a8 | 168 | if ((rhz >> 6) > 0) |
3795da47 WHSE |
169 | lp->flag |= LP_VALID_RHZ; |
170 | else | |
171 | lp->flag &= ~LP_VALID_RHZ; | |
7c106d7e | 172 | |
7c106d7e WHSE |
173 | /* record reference time stamp */ |
174 | lp->remote_ref_time = tp->rx_opt.rcv_tsval; | |
175 | lp->local_ref_time = tp->rx_opt.rcv_tsecr; | |
176 | ||
177 | return rhz >> 6; | |
178 | } | |
179 | ||
180 | /** | |
181 | * tcp_lp_owd_calculator | |
726e5e49 | 182 | * @sk: socket to calculate one way delay for |
7c106d7e WHSE |
183 | * |
184 | * Calculate one way delay (in relative format). | |
185 | * Original implement OWD as minus of remote time difference to local time | |
186 | * difference directly. As this time difference just simply equal to RTT, when | |
187 | * the network status is stable, remote RTT will equal to local RTT, and result | |
188 | * OWD into zero. | |
189 | * It seems to be a bug and so we fixed it. | |
190 | */ | |
191 | static u32 tcp_lp_owd_calculator(struct sock *sk) | |
192 | { | |
193 | struct tcp_sock *tp = tcp_sk(sk); | |
194 | struct lp *lp = inet_csk_ca(sk); | |
195 | s64 owd = 0; | |
196 | ||
197 | lp->remote_hz = tcp_lp_remote_hz_estimator(sk); | |
198 | ||
199 | if (lp->flag & LP_VALID_RHZ) { | |
200 | owd = | |
201 | tp->rx_opt.rcv_tsval * (LP_RESOL / lp->remote_hz) - | |
9a568de4 | 202 | tp->rx_opt.rcv_tsecr * (LP_RESOL / TCP_TS_HZ); |
7c106d7e WHSE |
203 | if (owd < 0) |
204 | owd = -owd; | |
205 | } | |
206 | ||
207 | if (owd > 0) | |
208 | lp->flag |= LP_VALID_OWD; | |
209 | else | |
210 | lp->flag &= ~LP_VALID_OWD; | |
211 | ||
212 | return owd; | |
213 | } | |
214 | ||
215 | /** | |
216 | * tcp_lp_rtt_sample | |
726e5e49 AL |
217 | * @sk: socket to add a rtt sample to |
218 | * @rtt: round trip time, which is ignored! | |
7c106d7e WHSE |
219 | * |
220 | * Implementation or rtt_sample. | |
221 | * Will take the following action, | |
222 | * 1. calc OWD, | |
223 | * 2. record the min/max OWD, | |
224 | * 3. calc smoothed OWD (SOWD). | |
225 | * Most ideas come from the original TCP-LP implementation. | |
226 | */ | |
164891aa | 227 | static void tcp_lp_rtt_sample(struct sock *sk, u32 rtt) |
7c106d7e WHSE |
228 | { |
229 | struct lp *lp = inet_csk_ca(sk); | |
230 | s64 mowd = tcp_lp_owd_calculator(sk); | |
231 | ||
232 | /* sorry that we don't have valid data */ | |
233 | if (!(lp->flag & LP_VALID_RHZ) || !(lp->flag & LP_VALID_OWD)) | |
234 | return; | |
235 | ||
236 | /* record the next min owd */ | |
237 | if (mowd < lp->owd_min) | |
238 | lp->owd_min = mowd; | |
239 | ||
240 | /* always forget the max of the max | |
241 | * we just set owd_max as one below it */ | |
242 | if (mowd > lp->owd_max) { | |
243 | if (mowd > lp->owd_max_rsv) { | |
244 | if (lp->owd_max_rsv == 0) | |
245 | lp->owd_max = mowd; | |
246 | else | |
247 | lp->owd_max = lp->owd_max_rsv; | |
248 | lp->owd_max_rsv = mowd; | |
249 | } else | |
250 | lp->owd_max = mowd; | |
251 | } | |
252 | ||
253 | /* calc for smoothed owd */ | |
254 | if (lp->sowd != 0) { | |
255 | mowd -= lp->sowd >> 3; /* m is now error in owd est */ | |
256 | lp->sowd += mowd; /* owd = 7/8 owd + 1/8 new */ | |
257 | } else | |
258 | lp->sowd = mowd << 3; /* take the measured time be owd */ | |
259 | } | |
260 | ||
261 | /** | |
262 | * tcp_lp_pkts_acked | |
726e5e49 | 263 | * @sk: socket requiring congestion avoidance calculations |
7c106d7e WHSE |
264 | * |
265 | * Implementation of pkts_acked. | |
266 | * Deal with active drop under Early Congestion Indication. | |
267 | * Only drop to half and 1 will be handle, because we hope to use back | |
268 | * newReno in increase case. | |
269 | * We work it out by following the idea from TCP-LP's paper directly | |
270 | */ | |
756ee172 | 271 | static void tcp_lp_pkts_acked(struct sock *sk, const struct ack_sample *sample) |
7c106d7e WHSE |
272 | { |
273 | struct tcp_sock *tp = tcp_sk(sk); | |
274 | struct lp *lp = inet_csk_ca(sk); | |
9a568de4 | 275 | u32 now = tcp_time_stamp(tp); |
a9f11f96 | 276 | u32 delta; |
7c106d7e | 277 | |
756ee172 LB |
278 | if (sample->rtt_us > 0) |
279 | tcp_lp_rtt_sample(sk, sample->rtt_us); | |
164891aa | 280 | |
7c106d7e | 281 | /* calc inference */ |
46bf466f | 282 | delta = now - tp->rx_opt.rcv_tsecr; |
a9f11f96 ED |
283 | if ((s32)delta > 0) |
284 | lp->inference = 3 * delta; | |
7c106d7e WHSE |
285 | |
286 | /* test if within inference */ | |
46bf466f | 287 | if (lp->last_drop && (now - lp->last_drop < lp->inference)) |
7c106d7e WHSE |
288 | lp->flag |= LP_WITHIN_INF; |
289 | else | |
290 | lp->flag &= ~LP_WITHIN_INF; | |
291 | ||
292 | /* test if within threshold */ | |
293 | if (lp->sowd >> 3 < | |
294 | lp->owd_min + 15 * (lp->owd_max - lp->owd_min) / 100) | |
295 | lp->flag |= LP_WITHIN_THR; | |
296 | else | |
297 | lp->flag &= ~LP_WITHIN_THR; | |
298 | ||
299 | pr_debug("TCP-LP: %05o|%5u|%5u|%15u|%15u|%15u\n", lp->flag, | |
40570375 | 300 | tcp_snd_cwnd(tp), lp->remote_hz, lp->owd_min, lp->owd_max, |
7c106d7e WHSE |
301 | lp->sowd >> 3); |
302 | ||
303 | if (lp->flag & LP_WITHIN_THR) | |
304 | return; | |
305 | ||
306 | /* FIXME: try to reset owd_min and owd_max here | |
307 | * so decrease the chance the min/max is no longer suitable | |
e5ca43e8 | 308 | * and will usually within threshold when within inference */ |
7c106d7e WHSE |
309 | lp->owd_min = lp->sowd >> 3; |
310 | lp->owd_max = lp->sowd >> 2; | |
311 | lp->owd_max_rsv = lp->sowd >> 2; | |
312 | ||
313 | /* happened within inference | |
314 | * drop snd_cwnd into 1 */ | |
315 | if (lp->flag & LP_WITHIN_INF) | |
40570375 | 316 | tcp_snd_cwnd_set(tp, 1U); |
7c106d7e WHSE |
317 | |
318 | /* happened after inference | |
319 | * cut snd_cwnd into half */ | |
320 | else | |
40570375 | 321 | tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp) >> 1U, 1U)); |
7c106d7e WHSE |
322 | |
323 | /* record this drop time */ | |
46bf466f | 324 | lp->last_drop = now; |
7c106d7e WHSE |
325 | } |
326 | ||
a252bebe | 327 | static struct tcp_congestion_ops tcp_lp __read_mostly = { |
7c106d7e WHSE |
328 | .init = tcp_lp_init, |
329 | .ssthresh = tcp_reno_ssthresh, | |
e9799183 | 330 | .undo_cwnd = tcp_reno_undo_cwnd, |
7c106d7e | 331 | .cong_avoid = tcp_lp_cong_avoid, |
7c106d7e WHSE |
332 | .pkts_acked = tcp_lp_pkts_acked, |
333 | ||
334 | .owner = THIS_MODULE, | |
335 | .name = "lp" | |
336 | }; | |
337 | ||
338 | static int __init tcp_lp_register(void) | |
339 | { | |
29896972 | 340 | BUILD_BUG_ON(sizeof(struct lp) > ICSK_CA_PRIV_SIZE); |
7c106d7e WHSE |
341 | return tcp_register_congestion_control(&tcp_lp); |
342 | } | |
343 | ||
344 | static void __exit tcp_lp_unregister(void) | |
345 | { | |
346 | tcp_unregister_congestion_control(&tcp_lp); | |
347 | } | |
348 | ||
349 | module_init(tcp_lp_register); | |
350 | module_exit(tcp_lp_unregister); | |
351 | ||
3795da47 | 352 | MODULE_AUTHOR("Wong Hoi Sing Edison, Hung Hing Lun Mike"); |
7c106d7e WHSE |
353 | MODULE_LICENSE("GPL"); |
354 | MODULE_DESCRIPTION("TCP Low Priority"); |