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treewide: remove redundant IS_ERR() before error code check
[linux/fpc-iii.git] / tools / testing / selftests / bpf / progs / bpf_cubic.c
blob7897c8f4d363bb67061d26f436a007a47114a89a
1 // SPDX-License-Identifier: GPL-2.0-only
2
3 /* WARNING: This implemenation is not necessarily the same
4 * as the tcp_cubic.c. The purpose is mainly for testing
5 * the kernel BPF logic.
6 *
7 * Highlights:
8 * 1. CONFIG_HZ .kconfig map is used.
9 * 2. In bictcp_update(), calculation is changed to use usec
10 * resolution (i.e. USEC_PER_JIFFY) instead of using jiffies.
11 * Thus, usecs_to_jiffies() is not used in the bpf_cubic.c.
12 * 3. In bitctcp_update() [under tcp_friendliness], the original
13 * "while (ca->ack_cnt > delta)" loop is changed to the equivalent
14 * "ca->ack_cnt / delta" operation.
15 */
16
17 #include <linux/bpf.h>
18 #include "bpf_tcp_helpers.h"
19
20 char _license[] SEC("license") = "GPL";
21
22 #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
23
24 #define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation
25 * max_cwnd = snd_cwnd * beta
26 */
27 #define BICTCP_HZ 10 /* BIC HZ 2^10 = 1024 */
28
29 /* Two methods of hybrid slow start */
30 #define HYSTART_ACK_TRAIN 0x1
31 #define HYSTART_DELAY 0x2
32
33 /* Number of delay samples for detecting the increase of delay */
34 #define HYSTART_MIN_SAMPLES 8
35 #define HYSTART_DELAY_MIN (4000U) /* 4ms */
36 #define HYSTART_DELAY_MAX (16000U) /* 16 ms */
37 #define HYSTART_DELAY_THRESH(x) clamp(x, HYSTART_DELAY_MIN, HYSTART_DELAY_MAX)
38
39 static int fast_convergence = 1;
40 static const int beta = 717; /* = 717/1024 (BICTCP_BETA_SCALE) */
41 static int initial_ssthresh;
42 static const int bic_scale = 41;
43 static int tcp_friendliness = 1;
44
45 static int hystart = 1;
46 static int hystart_detect = HYSTART_ACK_TRAIN | HYSTART_DELAY;
47 static int hystart_low_window = 16;
48 static int hystart_ack_delta_us = 2000;
49
50 static const __u32 cube_rtt_scale = (bic_scale * 10); /* 1024*c/rtt */
51 static const __u32 beta_scale = 8*(BICTCP_BETA_SCALE+beta) / 3
52 / (BICTCP_BETA_SCALE - beta);
53 /* calculate the "K" for (wmax-cwnd) = c/rtt * K^3
54 * so K = cubic_root( (wmax-cwnd)*rtt/c )
55 * the unit of K is bictcp_HZ=2^10, not HZ
56 *
57 * c = bic_scale >> 10
58 * rtt = 100ms
59 *
60 * the following code has been designed and tested for
61 * cwnd < 1 million packets
62 * RTT < 100 seconds
63 * HZ < 1,000,00 (corresponding to 10 nano-second)
64 */
65
66 /* 1/c * 2^2*bictcp_HZ * srtt, 2^40 */
67 static const __u64 cube_factor = (__u64)(1ull << (10+3*BICTCP_HZ))
68 / (bic_scale * 10);
69
70 /* BIC TCP Parameters */
71 struct bictcp {
72 __u32 cnt; /* increase cwnd by 1 after ACKs */
73 __u32 last_max_cwnd; /* last maximum snd_cwnd */
74 __u32 last_cwnd; /* the last snd_cwnd */
75 __u32 last_time; /* time when updated last_cwnd */
76 __u32 bic_origin_point;/* origin point of bic function */
77 __u32 bic_K; /* time to origin point
78 from the beginning of the current epoch */
79 __u32 delay_min; /* min delay (usec) */
80 __u32 epoch_start; /* beginning of an epoch */
81 __u32 ack_cnt; /* number of acks */
82 __u32 tcp_cwnd; /* estimated tcp cwnd */
83 __u16 unused;
84 __u8 sample_cnt; /* number of samples to decide curr_rtt */
85 __u8 found; /* the exit point is found? */
86 __u32 round_start; /* beginning of each round */
87 __u32 end_seq; /* end_seq of the round */
88 __u32 last_ack; /* last time when the ACK spacing is close */
89 __u32 curr_rtt; /* the minimum rtt of current round */
90 };
91
92 static inline void bictcp_reset(struct bictcp *ca)
93 {
94 ca->cnt = 0;
95 ca->last_max_cwnd = 0;
96 ca->last_cwnd = 0;
97 ca->last_time = 0;
98 ca->bic_origin_point = 0;
99 ca->bic_K = 0;
100 ca->delay_min = 0;
101 ca->epoch_start = 0;
102 ca->ack_cnt = 0;
103 ca->tcp_cwnd = 0;
104 ca->found = 0;
105 }
106
107 extern unsigned long CONFIG_HZ __kconfig;
108 #define HZ CONFIG_HZ
109 #define USEC_PER_MSEC 1000UL
110 #define USEC_PER_SEC 1000000UL
111 #define USEC_PER_JIFFY (USEC_PER_SEC / HZ)
112
113 static __always_inline __u64 div64_u64(__u64 dividend, __u64 divisor)
114 {
115 return dividend / divisor;
116 }
117
118 #define div64_ul div64_u64
119
120 #define BITS_PER_U64 (sizeof(__u64) * 8)
121 static __always_inline int fls64(__u64 x)
122 {
123 int num = BITS_PER_U64 - 1;
124
125 if (x == 0)
126 return 0;
127
128 if (!(x & (~0ull << (BITS_PER_U64-32)))) {
129 num -= 32;
130 x <<= 32;
131 }
132 if (!(x & (~0ull << (BITS_PER_U64-16)))) {
133 num -= 16;
134 x <<= 16;
135 }
136 if (!(x & (~0ull << (BITS_PER_U64-8)))) {
137 num -= 8;
138 x <<= 8;
139 }
140 if (!(x & (~0ull << (BITS_PER_U64-4)))) {
141 num -= 4;
142 x <<= 4;
143 }
144 if (!(x & (~0ull << (BITS_PER_U64-2)))) {
145 num -= 2;
146 x <<= 2;
147 }
148 if (!(x & (~0ull << (BITS_PER_U64-1))))
149 num -= 1;
150
151 return num + 1;
152 }
153
154 static __always_inline __u32 bictcp_clock_us(const struct sock *sk)
155 {
156 return tcp_sk(sk)->tcp_mstamp;
157 }
158
159 static __always_inline void bictcp_hystart_reset(struct sock *sk)
160 {
161 struct tcp_sock *tp = tcp_sk(sk);
162 struct bictcp *ca = inet_csk_ca(sk);
163
164 ca->round_start = ca->last_ack = bictcp_clock_us(sk);
165 ca->end_seq = tp->snd_nxt;
166 ca->curr_rtt = ~0U;
167 ca->sample_cnt = 0;
168 }
169
170 /* "struct_ops/" prefix is not a requirement
171 * It will be recognized as BPF_PROG_TYPE_STRUCT_OPS
172 * as long as it is used in one of the func ptr
173 * under SEC(".struct_ops").
174 */
175 SEC("struct_ops/bictcp_init")
176 void BPF_PROG(bictcp_init, struct sock *sk)
177 {
178 struct bictcp *ca = inet_csk_ca(sk);
179
180 bictcp_reset(ca);
181
182 if (hystart)
183 bictcp_hystart_reset(sk);
184
185 if (!hystart && initial_ssthresh)
186 tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
187 }
188
189 /* No prefix in SEC will also work.
190 * The remaining tcp-cubic functions have an easier way.
191 */
192 SEC("no-sec-prefix-bictcp_cwnd_event")
193 void BPF_PROG(bictcp_cwnd_event, struct sock *sk, enum tcp_ca_event event)
194 {
195 if (event == CA_EVENT_TX_START) {
196 struct bictcp *ca = inet_csk_ca(sk);
197 __u32 now = tcp_jiffies32;
198 __s32 delta;
199
200 delta = now - tcp_sk(sk)->lsndtime;
201
202 /* We were application limited (idle) for a while.
203 * Shift epoch_start to keep cwnd growth to cubic curve.
204 */
205 if (ca->epoch_start && delta > 0) {
206 ca->epoch_start += delta;
207 if (after(ca->epoch_start, now))
208 ca->epoch_start = now;
209 }
210 return;
211 }
212 }
213
214 /*
215 * cbrt(x) MSB values for x MSB values in [0..63].
216 * Precomputed then refined by hand - Willy Tarreau
217 *
218 * For x in [0..63],
219 * v = cbrt(x << 18) - 1
220 * cbrt(x) = (v[x] + 10) >> 6
221 */
222 static const __u8 v[] = {
223 /* 0x00 */ 0, 54, 54, 54, 118, 118, 118, 118,
224 /* 0x08 */ 123, 129, 134, 138, 143, 147, 151, 156,
225 /* 0x10 */ 157, 161, 164, 168, 170, 173, 176, 179,
226 /* 0x18 */ 181, 185, 187, 190, 192, 194, 197, 199,
227 /* 0x20 */ 200, 202, 204, 206, 209, 211, 213, 215,
228 /* 0x28 */ 217, 219, 221, 222, 224, 225, 227, 229,
229 /* 0x30 */ 231, 232, 234, 236, 237, 239, 240, 242,
230 /* 0x38 */ 244, 245, 246, 248, 250, 251, 252, 254,
231 };
232
233 /* calculate the cubic root of x using a table lookup followed by one
234 * Newton-Raphson iteration.
235 * Avg err ~= 0.195%
236 */
237 static __always_inline __u32 cubic_root(__u64 a)
238 {
239 __u32 x, b, shift;
240
241 if (a < 64) {
242 /* a in [0..63] */
243 return ((__u32)v[(__u32)a] + 35) >> 6;
244 }
245
246 b = fls64(a);
247 b = ((b * 84) >> 8) - 1;
248 shift = (a >> (b * 3));
249
250 /* it is needed for verifier's bound check on v */
251 if (shift >= 64)
252 return 0;
253
254 x = ((__u32)(((__u32)v[shift] + 10) << b)) >> 6;
255
256 /*
257 * Newton-Raphson iteration
258 * 2
259 * x = ( 2 * x + a / x ) / 3
260 * k+1 k k
261 */
262 x = (2 * x + (__u32)div64_u64(a, (__u64)x * (__u64)(x - 1)));
263 x = ((x * 341) >> 10);
264 return x;
265 }
266
267 /*
268 * Compute congestion window to use.
269 */
270 static __always_inline void bictcp_update(struct bictcp *ca, __u32 cwnd,
271 __u32 acked)
272 {
273 __u32 delta, bic_target, max_cnt;
274 __u64 offs, t;
275
276 ca->ack_cnt += acked; /* count the number of ACKed packets */
277
278 if (ca->last_cwnd == cwnd &&
279 (__s32)(tcp_jiffies32 - ca->last_time) <= HZ / 32)
280 return;
281
282 /* The CUBIC function can update ca->cnt at most once per jiffy.
283 * On all cwnd reduction events, ca->epoch_start is set to 0,
284 * which will force a recalculation of ca->cnt.
285 */
286 if (ca->epoch_start && tcp_jiffies32 == ca->last_time)
287 goto tcp_friendliness;
288
289 ca->last_cwnd = cwnd;
290 ca->last_time = tcp_jiffies32;
291
292 if (ca->epoch_start == 0) {
293 ca->epoch_start = tcp_jiffies32; /* record beginning */
294 ca->ack_cnt = acked; /* start counting */
295 ca->tcp_cwnd = cwnd; /* syn with cubic */
296
297 if (ca->last_max_cwnd <= cwnd) {
298 ca->bic_K = 0;
299 ca->bic_origin_point = cwnd;
300 } else {
301 /* Compute new K based on
302 * (wmax-cwnd) * (srtt>>3 / HZ) / c * 2^(3*bictcp_HZ)
303 */
304 ca->bic_K = cubic_root(cube_factor
305 * (ca->last_max_cwnd - cwnd));
306 ca->bic_origin_point = ca->last_max_cwnd;
307 }
308 }
309
310 /* cubic function - calc*/
311 /* calculate c * time^3 / rtt,
312 * while considering overflow in calculation of time^3
313 * (so time^3 is done by using 64 bit)
314 * and without the support of division of 64bit numbers
315 * (so all divisions are done by using 32 bit)
316 * also NOTE the unit of those veriables
317 * time = (t - K) / 2^bictcp_HZ
318 * c = bic_scale >> 10
319 * rtt = (srtt >> 3) / HZ
320 * !!! The following code does not have overflow problems,
321 * if the cwnd < 1 million packets !!!
322 */
323
324 t = (__s32)(tcp_jiffies32 - ca->epoch_start) * USEC_PER_JIFFY;
325 t += ca->delay_min;
326 /* change the unit from usec to bictcp_HZ */
327 t <<= BICTCP_HZ;
328 t /= USEC_PER_SEC;
329
330 if (t < ca->bic_K) /* t - K */
331 offs = ca->bic_K - t;
332 else
333 offs = t - ca->bic_K;
334
335 /* c/rtt * (t-K)^3 */
336 delta = (cube_rtt_scale * offs * offs * offs) >> (10+3*BICTCP_HZ);
337 if (t < ca->bic_K) /* below origin*/
338 bic_target = ca->bic_origin_point - delta;
339 else /* above origin*/
340 bic_target = ca->bic_origin_point + delta;
341
342 /* cubic function - calc bictcp_cnt*/
343 if (bic_target > cwnd) {
344 ca->cnt = cwnd / (bic_target - cwnd);
345 } else {
346 ca->cnt = 100 * cwnd; /* very small increment*/
347 }
348
349 /*
350 * The initial growth of cubic function may be too conservative
351 * when the available bandwidth is still unknown.
352 */
353 if (ca->last_max_cwnd == 0 && ca->cnt > 20)
354 ca->cnt = 20; /* increase cwnd 5% per RTT */
355
356 tcp_friendliness:
357 /* TCP Friendly */
358 if (tcp_friendliness) {
359 __u32 scale = beta_scale;
360 __u32 n;
361
362 /* update tcp cwnd */
363 delta = (cwnd * scale) >> 3;
364 if (ca->ack_cnt > delta && delta) {
365 n = ca->ack_cnt / delta;
366 ca->ack_cnt -= n * delta;
367 ca->tcp_cwnd += n;
368 }
369
370 if (ca->tcp_cwnd > cwnd) { /* if bic is slower than tcp */
371 delta = ca->tcp_cwnd - cwnd;
372 max_cnt = cwnd / delta;
373 if (ca->cnt > max_cnt)
374 ca->cnt = max_cnt;
375 }
376 }
377
378 /* The maximum rate of cwnd increase CUBIC allows is 1 packet per
379 * 2 packets ACKed, meaning cwnd grows at 1.5x per RTT.
380 */
381 ca->cnt = max(ca->cnt, 2U);
382 }
383
384 /* Or simply use the BPF_STRUCT_OPS to avoid the SEC boiler plate. */
385 void BPF_STRUCT_OPS(bictcp_cong_avoid, struct sock *sk, __u32 ack, __u32 acked)
386 {
387 struct tcp_sock *tp = tcp_sk(sk);
388 struct bictcp *ca = inet_csk_ca(sk);
389
390 if (!tcp_is_cwnd_limited(sk))
391 return;
392
393 if (tcp_in_slow_start(tp)) {
394 if (hystart && after(ack, ca->end_seq))
395 bictcp_hystart_reset(sk);
396 acked = tcp_slow_start(tp, acked);
397 if (!acked)
398 return;
399 }
400 bictcp_update(ca, tp->snd_cwnd, acked);
401 tcp_cong_avoid_ai(tp, ca->cnt, acked);
402 }
403
404 __u32 BPF_STRUCT_OPS(bictcp_recalc_ssthresh, struct sock *sk)
405 {
406 const struct tcp_sock *tp = tcp_sk(sk);
407 struct bictcp *ca = inet_csk_ca(sk);
408
409 ca->epoch_start = 0; /* end of epoch */
410
411 /* Wmax and fast convergence */
412 if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)
413 ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))
414 / (2 * BICTCP_BETA_SCALE);
415 else
416 ca->last_max_cwnd = tp->snd_cwnd;
417
418 return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
419 }
420
421 void BPF_STRUCT_OPS(bictcp_state, struct sock *sk, __u8 new_state)
422 {
423 if (new_state == TCP_CA_Loss) {
424 bictcp_reset(inet_csk_ca(sk));
425 bictcp_hystart_reset(sk);
426 }
427 }
428
429 #define GSO_MAX_SIZE 65536
430
431 /* Account for TSO/GRO delays.
432 * Otherwise short RTT flows could get too small ssthresh, since during
433 * slow start we begin with small TSO packets and ca->delay_min would
434 * not account for long aggregation delay when TSO packets get bigger.
435 * Ideally even with a very small RTT we would like to have at least one
436 * TSO packet being sent and received by GRO, and another one in qdisc layer.
437 * We apply another 100% factor because @rate is doubled at this point.
438 * We cap the cushion to 1ms.
439 */
440 static __always_inline __u32 hystart_ack_delay(struct sock *sk)
441 {
442 unsigned long rate;
443
444 rate = sk->sk_pacing_rate;
445 if (!rate)
446 return 0;
447 return min((__u64)USEC_PER_MSEC,
448 div64_ul((__u64)GSO_MAX_SIZE * 4 * USEC_PER_SEC, rate));
449 }
450
451 static __always_inline void hystart_update(struct sock *sk, __u32 delay)
452 {
453 struct tcp_sock *tp = tcp_sk(sk);
454 struct bictcp *ca = inet_csk_ca(sk);
455 __u32 threshold;
456
457 if (hystart_detect & HYSTART_ACK_TRAIN) {
458 __u32 now = bictcp_clock_us(sk);
459
460 /* first detection parameter - ack-train detection */
461 if ((__s32)(now - ca->last_ack) <= hystart_ack_delta_us) {
462 ca->last_ack = now;
463
464 threshold = ca->delay_min + hystart_ack_delay(sk);
465
466 /* Hystart ack train triggers if we get ack past
467 * ca->delay_min/2.
468 * Pacing might have delayed packets up to RTT/2
469 * during slow start.
470 */
471 if (sk->sk_pacing_status == SK_PACING_NONE)
472 threshold >>= 1;
473
474 if ((__s32)(now - ca->round_start) > threshold) {
475 ca->found = 1;
476 tp->snd_ssthresh = tp->snd_cwnd;
477 }
478 }
479 }
480
481 if (hystart_detect & HYSTART_DELAY) {
482 /* obtain the minimum delay of more than sampling packets */
483 if (ca->sample_cnt < HYSTART_MIN_SAMPLES) {
484 if (ca->curr_rtt > delay)
485 ca->curr_rtt = delay;
486
487 ca->sample_cnt++;
488 } else {
489 if (ca->curr_rtt > ca->delay_min +
490 HYSTART_DELAY_THRESH(ca->delay_min >> 3)) {
491 ca->found = 1;
492 tp->snd_ssthresh = tp->snd_cwnd;
493 }
494 }
495 }
496 }
497
498 void BPF_STRUCT_OPS(bictcp_acked, struct sock *sk,
499 const struct ack_sample *sample)
500 {
501 const struct tcp_sock *tp = tcp_sk(sk);
502 struct bictcp *ca = inet_csk_ca(sk);
503 __u32 delay;
504
505 /* Some calls are for duplicates without timetamps */
506 if (sample->rtt_us < 0)
507 return;
508
509 /* Discard delay samples right after fast recovery */
510 if (ca->epoch_start && (__s32)(tcp_jiffies32 - ca->epoch_start) < HZ)
511 return;
512
513 delay = sample->rtt_us;
514 if (delay == 0)
515 delay = 1;
516
517 /* first time call or link delay decreases */
518 if (ca->delay_min == 0 || ca->delay_min > delay)
519 ca->delay_min = delay;
520
521 /* hystart triggers when cwnd is larger than some threshold */
522 if (!ca->found && tcp_in_slow_start(tp) && hystart &&
523 tp->snd_cwnd >= hystart_low_window)
524 hystart_update(sk, delay);
525 }
526
527 __u32 BPF_STRUCT_OPS(tcp_reno_undo_cwnd, struct sock *sk)
528 {
529 const struct tcp_sock *tp = tcp_sk(sk);
530
531 return max(tp->snd_cwnd, tp->prior_cwnd);
532 }
533
534 SEC(".struct_ops")
535 struct tcp_congestion_ops cubic = {
536 .init = (void *)bictcp_init,
537 .ssthresh = (void *)bictcp_recalc_ssthresh,
538 .cong_avoid = (void *)bictcp_cong_avoid,
539 .set_state = (void *)bictcp_state,
540 .undo_cwnd = (void *)tcp_reno_undo_cwnd,
541 .cwnd_event = (void *)bictcp_cwnd_event,
542 .pkts_acked = (void *)bictcp_acked,
543 .name = "bpf_cubic",
544 };
Linux with added FPC-III support