1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
4 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
5 * Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
6 *
7 * An implementation of the DCCP protocol
8 *
9 * This code has been developed by the University of Waikato WAND
10 * research group. For further information please see http://www.wand.net.nz/
11 *
12 * This code also uses code from Lulea University, rereleased as GPL by its
13 * authors:
14 * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
15 *
16 * Changes to meet Linux coding standards, to make it meet latest ccid3 draft
17 * and to make it work as a loadable module in the DCCP stack written by
18 * Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
19 *
20 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
21 */
22 #include "../dccp.h"
23 #include "ccid3.h"
24
25 #include <asm/unaligned.h>
26
27 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
28 static bool ccid3_debug;
29 #define ccid3_pr_debug(format, a...) DCCP_PR_DEBUG(ccid3_debug, format, ##a)
30 #else
31 #define ccid3_pr_debug(format, a...)
32 #endif
33
34 /*
35 * Transmitter Half-Connection Routines
36 */
37 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
ccid3_tx_state_name(enum ccid3_hc_tx_states state)38 static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
39 {
40 static const char *const ccid3_state_names[] = {
41 [TFRC_SSTATE_NO_SENT] = "NO_SENT",
42 [TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
43 [TFRC_SSTATE_FBACK] = "FBACK",
44 };
45
46 return ccid3_state_names[state];
47 }
48 #endif
49
ccid3_hc_tx_set_state(struct sock * sk,enum ccid3_hc_tx_states state)50 static void ccid3_hc_tx_set_state(struct sock *sk,
51 enum ccid3_hc_tx_states state)
52 {
53 struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
54 enum ccid3_hc_tx_states oldstate = hc->tx_state;
55
56 ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
57 dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
58 ccid3_tx_state_name(state));
59 WARN_ON(state == oldstate);
60 hc->tx_state = state;
61 }
62
63 /*
64 * Compute the initial sending rate X_init in the manner of RFC 3390:
65 *
66 * X_init = min(4 * s, max(2 * s, 4380 bytes)) / RTT
67 *
68 * Note that RFC 3390 uses MSS, RFC 4342 refers to RFC 3390, and rfc3448bis
69 * (rev-02) clarifies the use of RFC 3390 with regard to the above formula.
70 * For consistency with other parts of the code, X_init is scaled by 2^6.
71 */
rfc3390_initial_rate(struct sock * sk)72 static inline u64 rfc3390_initial_rate(struct sock *sk)
73 {
74 const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
75 const __u32 w_init = clamp_t(__u32, 4380U, 2 * hc->tx_s, 4 * hc->tx_s);
76
77 return scaled_div(w_init << 6, hc->tx_rtt);
78 }
79
80 /**
81 * ccid3_update_send_interval - Calculate new t_ipi = s / X_inst
82 * This respects the granularity of X_inst (64 * bytes/second).
83 */
ccid3_update_send_interval(struct ccid3_hc_tx_sock * hc)84 static void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hc)
85 {
86 hc->tx_t_ipi = scaled_div32(((u64)hc->tx_s) << 6, hc->tx_x);
87
88 DCCP_BUG_ON(hc->tx_t_ipi == 0);
89 ccid3_pr_debug("t_ipi=%u, s=%u, X=%u\n", hc->tx_t_ipi,
90 hc->tx_s, (unsigned int)(hc->tx_x >> 6));
91 }
92
ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock * hc,ktime_t now)93 static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hc, ktime_t now)
94 {
95 u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count);
96
97 return delta / hc->tx_rtt;
98 }
99
100 /**
101 * ccid3_hc_tx_update_x - Update allowed sending rate X
102 * @stamp: most recent time if available - can be left NULL.
103 *
104 * This function tracks draft rfc3448bis, check there for latest details.
105 *
106 * Note: X and X_recv are both stored in units of 64 * bytes/second, to support
107 * fine-grained resolution of sending rates. This requires scaling by 2^6
108 * throughout the code. Only X_calc is unscaled (in bytes/second).
109 *
110 */
ccid3_hc_tx_update_x(struct sock * sk,ktime_t * stamp)111 static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
112 {
113 struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
114 __u64 min_rate = 2 * hc->tx_x_recv;
115 const __u64 old_x = hc->tx_x;
116 ktime_t now = stamp ? *stamp : ktime_get_real();
117
118 /*
119 * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
120 * when idling [RFC 4342, 5.1]. Definition of idling is from rfc3448bis:
121 * a sender is idle if it has not sent anything over a 2-RTT-period.
122 * For consistency with X and X_recv, min_rate is also scaled by 2^6.
123 */
124 if (ccid3_hc_tx_idle_rtt(hc, now) >= 2) {
125 min_rate = rfc3390_initial_rate(sk);
126 min_rate = max(min_rate, 2 * hc->tx_x_recv);
127 }
128
129 if (hc->tx_p > 0) {
130
131 hc->tx_x = min(((__u64)hc->tx_x_calc) << 6, min_rate);
132 hc->tx_x = max(hc->tx_x, (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
133
134 } else if (ktime_us_delta(now, hc->tx_t_ld) - (s64)hc->tx_rtt >= 0) {
135
136 hc->tx_x = min(2 * hc->tx_x, min_rate);
137 hc->tx_x = max(hc->tx_x,
138 scaled_div(((__u64)hc->tx_s) << 6, hc->tx_rtt));
139 hc->tx_t_ld = now;
140 }
141
142 if (hc->tx_x != old_x) {
143 ccid3_pr_debug("X_prev=%u, X_now=%u, X_calc=%u, "
144 "X_recv=%u\n", (unsigned int)(old_x >> 6),
145 (unsigned int)(hc->tx_x >> 6), hc->tx_x_calc,
146 (unsigned int)(hc->tx_x_recv >> 6));
147
148 ccid3_update_send_interval(hc);
149 }
150 }
151
152 /**
153 * ccid3_hc_tx_update_s - Track the mean packet size `s'
154 * @len: DCCP packet payload size in bytes
155 *
156 * cf. RFC 4342, 5.3 and RFC 3448, 4.1
157 */
ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock * hc,int len)158 static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hc, int len)
159 {
160 const u16 old_s = hc->tx_s;
161
162 hc->tx_s = tfrc_ewma(hc->tx_s, len, 9);
163
164 if (hc->tx_s != old_s)
165 ccid3_update_send_interval(hc);
166 }
167
168 /*
169 * Update Window Counter using the algorithm from [RFC 4342, 8.1].
170 * As elsewhere, RTT > 0 is assumed by using dccp_sample_rtt().
171 */
ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock * hc,ktime_t now)172 static inline void ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock *hc,
173 ktime_t now)
174 {
175 u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count),
176 quarter_rtts = (4 * delta) / hc->tx_rtt;
177
178 if (quarter_rtts > 0) {
179 hc->tx_t_last_win_count = now;
180 hc->tx_last_win_count += min(quarter_rtts, 5U);
181 hc->tx_last_win_count &= 0xF; /* mod 16 */
182 }
183 }
184
ccid3_hc_tx_no_feedback_timer(struct timer_list * t)185 static void ccid3_hc_tx_no_feedback_timer(struct timer_list *t)
186 {
187 struct ccid3_hc_tx_sock *hc = from_timer(hc, t, tx_no_feedback_timer);
188 struct sock *sk = hc->sk;
189 unsigned long t_nfb = USEC_PER_SEC / 5;
190
191 bh_lock_sock(sk);
192 if (sock_owned_by_user(sk)) {
193 /* Try again later. */
194 /* XXX: set some sensible MIB */
195 goto restart_timer;
196 }
197
198 ccid3_pr_debug("%s(%p, state=%s) - entry\n", dccp_role(sk), sk,
199 ccid3_tx_state_name(hc->tx_state));
200
201 /* Ignore and do not restart after leaving the established state */
202 if ((1 << sk->sk_state) & ~(DCCPF_OPEN | DCCPF_PARTOPEN))
203 goto out;
204
205 /* Reset feedback state to "no feedback received" */
206 if (hc->tx_state == TFRC_SSTATE_FBACK)
207 ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
208
209 /*
210 * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
211 * RTO is 0 if and only if no feedback has been received yet.
212 */
213 if (hc->tx_t_rto == 0 || hc->tx_p == 0) {
214
215 /* halve send rate directly */
216 hc->tx_x = max(hc->tx_x / 2,
217 (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
218 ccid3_update_send_interval(hc);
219 } else {
220 /*
221 * Modify the cached value of X_recv
222 *
223 * If (X_calc > 2 * X_recv)
224 * X_recv = max(X_recv / 2, s / (2 * t_mbi));
225 * Else
226 * X_recv = X_calc / 4;
227 *
228 * Note that X_recv is scaled by 2^6 while X_calc is not
229 */
230 if (hc->tx_x_calc > (hc->tx_x_recv >> 5))
231 hc->tx_x_recv =
232 max(hc->tx_x_recv / 2,
233 (((__u64)hc->tx_s) << 6) / (2*TFRC_T_MBI));
234 else {
235 hc->tx_x_recv = hc->tx_x_calc;
236 hc->tx_x_recv <<= 4;
237 }
238 ccid3_hc_tx_update_x(sk, NULL);
239 }
240 ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
241 (unsigned long long)hc->tx_x);
242
243 /*
244 * Set new timeout for the nofeedback timer.
245 * See comments in packet_recv() regarding the value of t_RTO.
246 */
247 if (unlikely(hc->tx_t_rto == 0)) /* no feedback received yet */
248 t_nfb = TFRC_INITIAL_TIMEOUT;
249 else
250 t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
251
252 restart_timer:
253 sk_reset_timer(sk, &hc->tx_no_feedback_timer,
254 jiffies + usecs_to_jiffies(t_nfb));
255 out:
256 bh_unlock_sock(sk);
257 sock_put(sk);
258 }
259
260 /**
261 * ccid3_hc_tx_send_packet - Delay-based dequeueing of TX packets
262 * @skb: next packet candidate to send on @sk
263 *
264 * This function uses the convention of ccid_packet_dequeue_eval() and
265 * returns a millisecond-delay value between 0 and t_mbi = 64000 msec.
266 */
ccid3_hc_tx_send_packet(struct sock * sk,struct sk_buff * skb)267 static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
268 {
269 struct dccp_sock *dp = dccp_sk(sk);
270 struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
271 ktime_t now = ktime_get_real();
272 s64 delay;
273
274 /*
275 * This function is called only for Data and DataAck packets. Sending
276 * zero-sized Data(Ack)s is theoretically possible, but for congestion
277 * control this case is pathological - ignore it.
278 */
279 if (unlikely(skb->len == 0))
280 return -EBADMSG;
281
282 if (hc->tx_state == TFRC_SSTATE_NO_SENT) {
283 sk_reset_timer(sk, &hc->tx_no_feedback_timer, (jiffies +
284 usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
285 hc->tx_last_win_count = 0;
286 hc->tx_t_last_win_count = now;
287
288 /* Set t_0 for initial packet */
289 hc->tx_t_nom = now;
290
291 hc->tx_s = skb->len;
292
293 /*
294 * Use initial RTT sample when available: recommended by erratum
295 * to RFC 4342. This implements the initialisation procedure of
296 * draft rfc3448bis, section 4.2. Remember, X is scaled by 2^6.
297 */
298 if (dp->dccps_syn_rtt) {
299 ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
300 hc->tx_rtt = dp->dccps_syn_rtt;
301 hc->tx_x = rfc3390_initial_rate(sk);
302 hc->tx_t_ld = now;
303 } else {
304 /*
305 * Sender does not have RTT sample:
306 * - set fallback RTT (RFC 4340, 3.4) since a RTT value
307 * is needed in several parts (e.g. window counter);
308 * - set sending rate X_pps = 1pps as per RFC 3448, 4.2.
309 */
310 hc->tx_rtt = DCCP_FALLBACK_RTT;
311 hc->tx_x = hc->tx_s;
312 hc->tx_x <<= 6;
313 }
314 ccid3_update_send_interval(hc);
315
316 ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
317
318 } else {
319 delay = ktime_us_delta(hc->tx_t_nom, now);
320 ccid3_pr_debug("delay=%ld\n", (long)delay);
321 /*
322 * Scheduling of packet transmissions (RFC 5348, 8.3)
323 *
324 * if (t_now > t_nom - delta)
325 * // send the packet now
326 * else
327 * // send the packet in (t_nom - t_now) milliseconds.
328 */
329 if (delay >= TFRC_T_DELTA)
330 return (u32)delay / USEC_PER_MSEC;
331
332 ccid3_hc_tx_update_win_count(hc, now);
333 }
334
335 /* prepare to send now (add options etc.) */
336 dp->dccps_hc_tx_insert_options = 1;
337 DCCP_SKB_CB(skb)->dccpd_ccval = hc->tx_last_win_count;
338
339 /* set the nominal send time for the next following packet */
340 hc->tx_t_nom = ktime_add_us(hc->tx_t_nom, hc->tx_t_ipi);
341 return CCID_PACKET_SEND_AT_ONCE;
342 }
343
ccid3_hc_tx_packet_sent(struct sock * sk,unsigned int len)344 static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)
345 {
346 struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
347
348 ccid3_hc_tx_update_s(hc, len);
349
350 if (tfrc_tx_hist_add(&hc->tx_hist, dccp_sk(sk)->dccps_gss))
351 DCCP_CRIT("packet history - out of memory!");
352 }
353
ccid3_hc_tx_packet_recv(struct sock * sk,struct sk_buff * skb)354 static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
355 {
356 struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
357 struct tfrc_tx_hist_entry *acked;
358 ktime_t now;
359 unsigned long t_nfb;
360 u32 r_sample;
361
362 /* we are only interested in ACKs */
363 if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
364 DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
365 return;
366 /*
367 * Locate the acknowledged packet in the TX history.
368 *
369 * Returning "entry not found" here can for instance happen when
370 * - the host has not sent out anything (e.g. a passive server),
371 * - the Ack is outdated (packet with higher Ack number was received),
372 * - it is a bogus Ack (for a packet not sent on this connection).
373 */
374 acked = tfrc_tx_hist_find_entry(hc->tx_hist, dccp_hdr_ack_seq(skb));
375 if (acked == NULL)
376 return;
377 /* For the sake of RTT sampling, ignore/remove all older entries */
378 tfrc_tx_hist_purge(&acked->next);
379
380 /* Update the moving average for the RTT estimate (RFC 3448, 4.3) */
381 now = ktime_get_real();
382 r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));
383 hc->tx_rtt = tfrc_ewma(hc->tx_rtt, r_sample, 9);
384
385 /*
386 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
387 */
388 if (hc->tx_state == TFRC_SSTATE_NO_FBACK) {
389 ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
390
391 if (hc->tx_t_rto == 0) {
392 /*
393 * Initial feedback packet: Larger Initial Windows (4.2)
394 */
395 hc->tx_x = rfc3390_initial_rate(sk);
396 hc->tx_t_ld = now;
397
398 ccid3_update_send_interval(hc);
399
400 goto done_computing_x;
401 } else if (hc->tx_p == 0) {
402 /*
403 * First feedback after nofeedback timer expiry (4.3)
404 */
405 goto done_computing_x;
406 }
407 }
408
409 /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
410 if (hc->tx_p > 0)
411 hc->tx_x_calc = tfrc_calc_x(hc->tx_s, hc->tx_rtt, hc->tx_p);
412 ccid3_hc_tx_update_x(sk, &now);
413
414 done_computing_x:
415 ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
416 "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
417 dccp_role(sk), sk, hc->tx_rtt, r_sample,
418 hc->tx_s, hc->tx_p, hc->tx_x_calc,
419 (unsigned int)(hc->tx_x_recv >> 6),
420 (unsigned int)(hc->tx_x >> 6));
421
422 /* unschedule no feedback timer */
423 sk_stop_timer(sk, &hc->tx_no_feedback_timer);
424
425 /*
426 * As we have calculated new ipi, delta, t_nom it is possible
427 * that we now can send a packet, so wake up dccp_wait_for_ccid
428 */
429 sk->sk_write_space(sk);
430
431 /*
432 * Update timeout interval for the nofeedback timer. In order to control
433 * rate halving on networks with very low RTTs (<= 1 ms), use per-route
434 * tunable RTAX_RTO_MIN value as the lower bound.
435 */
436 hc->tx_t_rto = max_t(u32, 4 * hc->tx_rtt,
437 USEC_PER_SEC/HZ * tcp_rto_min(sk));
438 /*
439 * Schedule no feedback timer to expire in
440 * max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi)
441 */
442 t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
443
444 ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
445 "expire in %lu jiffies (%luus)\n",
446 dccp_role(sk), sk, usecs_to_jiffies(t_nfb), t_nfb);
447
448 sk_reset_timer(sk, &hc->tx_no_feedback_timer,
449 jiffies + usecs_to_jiffies(t_nfb));
450 }
451
ccid3_hc_tx_parse_options(struct sock * sk,u8 packet_type,u8 option,u8 * optval,u8 optlen)452 static int ccid3_hc_tx_parse_options(struct sock *sk, u8 packet_type,
453 u8 option, u8 *optval, u8 optlen)
454 {
455 struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
456 __be32 opt_val;
457
458 switch (option) {
459 case TFRC_OPT_RECEIVE_RATE:
460 case TFRC_OPT_LOSS_EVENT_RATE:
461 /* Must be ignored on Data packets, cf. RFC 4342 8.3 and 8.5 */
462 if (packet_type == DCCP_PKT_DATA)
463 break;
464 if (unlikely(optlen != 4)) {
465 DCCP_WARN("%s(%p), invalid len %d for %u\n",
466 dccp_role(sk), sk, optlen, option);
467 return -EINVAL;
468 }
469 opt_val = ntohl(get_unaligned((__be32 *)optval));
470
471 if (option == TFRC_OPT_RECEIVE_RATE) {
472 /* Receive Rate is kept in units of 64 bytes/second */
473 hc->tx_x_recv = opt_val;
474 hc->tx_x_recv <<= 6;
475
476 ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
477 dccp_role(sk), sk, opt_val);
478 } else {
479 /* Update the fixpoint Loss Event Rate fraction */
480 hc->tx_p = tfrc_invert_loss_event_rate(opt_val);
481
482 ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
483 dccp_role(sk), sk, opt_val);
484 }
485 }
486 return 0;
487 }
488
ccid3_hc_tx_init(struct ccid * ccid,struct sock * sk)489 static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
490 {
491 struct ccid3_hc_tx_sock *hc = ccid_priv(ccid);
492
493 hc->tx_state = TFRC_SSTATE_NO_SENT;
494 hc->tx_hist = NULL;
495 hc->sk = sk;
496 timer_setup(&hc->tx_no_feedback_timer,
497 ccid3_hc_tx_no_feedback_timer, 0);
498 return 0;
499 }
500
ccid3_hc_tx_exit(struct sock * sk)501 static void ccid3_hc_tx_exit(struct sock *sk)
502 {
503 struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
504
505 sk_stop_timer(sk, &hc->tx_no_feedback_timer);
506 tfrc_tx_hist_purge(&hc->tx_hist);
507 }
508
ccid3_hc_tx_get_info(struct sock * sk,struct tcp_info * info)509 static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
510 {
511 info->tcpi_rto = ccid3_hc_tx_sk(sk)->tx_t_rto;
512 info->tcpi_rtt = ccid3_hc_tx_sk(sk)->tx_rtt;
513 }
514
ccid3_hc_tx_getsockopt(struct sock * sk,const int optname,int len,u32 __user * optval,int __user * optlen)515 static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
516 u32 __user *optval, int __user *optlen)
517 {
518 const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
519 struct tfrc_tx_info tfrc;
520 const void *val;
521
522 switch (optname) {
523 case DCCP_SOCKOPT_CCID_TX_INFO:
524 if (len < sizeof(tfrc))
525 return -EINVAL;
526 memset(&tfrc, 0, sizeof(tfrc));
527 tfrc.tfrctx_x = hc->tx_x;
528 tfrc.tfrctx_x_recv = hc->tx_x_recv;
529 tfrc.tfrctx_x_calc = hc->tx_x_calc;
530 tfrc.tfrctx_rtt = hc->tx_rtt;
531 tfrc.tfrctx_p = hc->tx_p;
532 tfrc.tfrctx_rto = hc->tx_t_rto;
533 tfrc.tfrctx_ipi = hc->tx_t_ipi;
534 len = sizeof(tfrc);
535 val = &tfrc;
536 break;
537 default:
538 return -ENOPROTOOPT;
539 }
540
541 if (put_user(len, optlen) || copy_to_user(optval, val, len))
542 return -EFAULT;
543
544 return 0;
545 }
546
547 /*
548 * Receiver Half-Connection Routines
549 */
550
551 /* CCID3 feedback types */
552 enum ccid3_fback_type {
553 CCID3_FBACK_NONE = 0,
554 CCID3_FBACK_INITIAL,
555 CCID3_FBACK_PERIODIC,
556 CCID3_FBACK_PARAM_CHANGE
557 };
558
559 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
ccid3_rx_state_name(enum ccid3_hc_rx_states state)560 static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
561 {
562 static const char *const ccid3_rx_state_names[] = {
563 [TFRC_RSTATE_NO_DATA] = "NO_DATA",
564 [TFRC_RSTATE_DATA] = "DATA",
565 };
566
567 return ccid3_rx_state_names[state];
568 }
569 #endif
570
ccid3_hc_rx_set_state(struct sock * sk,enum ccid3_hc_rx_states state)571 static void ccid3_hc_rx_set_state(struct sock *sk,
572 enum ccid3_hc_rx_states state)
573 {
574 struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
575 enum ccid3_hc_rx_states oldstate = hc->rx_state;
576
577 ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
578 dccp_role(sk), sk, ccid3_rx_state_name(oldstate),
579 ccid3_rx_state_name(state));
580 WARN_ON(state == oldstate);
581 hc->rx_state = state;
582 }
583
ccid3_hc_rx_send_feedback(struct sock * sk,const struct sk_buff * skb,enum ccid3_fback_type fbtype)584 static void ccid3_hc_rx_send_feedback(struct sock *sk,
585 const struct sk_buff *skb,
586 enum ccid3_fback_type fbtype)
587 {
588 struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
589 struct dccp_sock *dp = dccp_sk(sk);
590 ktime_t now = ktime_get();
591 s64 delta = 0;
592
593 switch (fbtype) {
594 case CCID3_FBACK_INITIAL:
595 hc->rx_x_recv = 0;
596 hc->rx_pinv = ~0U; /* see RFC 4342, 8.5 */
597 break;
598 case CCID3_FBACK_PARAM_CHANGE:
599 /*
600 * When parameters change (new loss or p > p_prev), we do not
601 * have a reliable estimate for R_m of [RFC 3448, 6.2] and so
602 * need to reuse the previous value of X_recv. However, when
603 * X_recv was 0 (due to early loss), this would kill X down to
604 * s/t_mbi (i.e. one packet in 64 seconds).
605 * To avoid such drastic reduction, we approximate X_recv as
606 * the number of bytes since last feedback.
607 * This is a safe fallback, since X is bounded above by X_calc.
608 */
609 if (hc->rx_x_recv > 0)
610 break;
611 /* fall through */
612 case CCID3_FBACK_PERIODIC:
613 delta = ktime_us_delta(now, hc->rx_tstamp_last_feedback);
614 if (delta <= 0)
615 delta = 1;
616 hc->rx_x_recv = scaled_div32(hc->rx_bytes_recv, delta);
617 break;
618 default:
619 return;
620 }
621
622 ccid3_pr_debug("Interval %lldusec, X_recv=%u, 1/p=%u\n", delta,
623 hc->rx_x_recv, hc->rx_pinv);
624
625 hc->rx_tstamp_last_feedback = now;
626 hc->rx_last_counter = dccp_hdr(skb)->dccph_ccval;
627 hc->rx_bytes_recv = 0;
628
629 dp->dccps_hc_rx_insert_options = 1;
630 dccp_send_ack(sk);
631 }
632
ccid3_hc_rx_insert_options(struct sock * sk,struct sk_buff * skb)633 static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
634 {
635 const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
636 __be32 x_recv, pinv;
637
638 if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
639 return 0;
640
641 if (dccp_packet_without_ack(skb))
642 return 0;
643
644 x_recv = htonl(hc->rx_x_recv);
645 pinv = htonl(hc->rx_pinv);
646
647 if (dccp_insert_option(skb, TFRC_OPT_LOSS_EVENT_RATE,
648 &pinv, sizeof(pinv)) ||
649 dccp_insert_option(skb, TFRC_OPT_RECEIVE_RATE,
650 &x_recv, sizeof(x_recv)))
651 return -1;
652
653 return 0;
654 }
655
656 /**
657 * ccid3_first_li - Implements [RFC 5348, 6.3.1]
658 *
659 * Determine the length of the first loss interval via inverse lookup.
660 * Assume that X_recv can be computed by the throughput equation
661 * s
662 * X_recv = --------
663 * R * fval
664 * Find some p such that f(p) = fval; return 1/p (scaled).
665 */
ccid3_first_li(struct sock * sk)666 static u32 ccid3_first_li(struct sock *sk)
667 {
668 struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
669 u32 x_recv, p;
670 s64 delta;
671 u64 fval;
672
673 if (hc->rx_rtt == 0) {
674 DCCP_WARN("No RTT estimate available, using fallback RTT\n");
675 hc->rx_rtt = DCCP_FALLBACK_RTT;
676 }
677
678 delta = ktime_us_delta(ktime_get(), hc->rx_tstamp_last_feedback);
679 if (delta <= 0)
680 delta = 1;
681 x_recv = scaled_div32(hc->rx_bytes_recv, delta);
682 if (x_recv == 0) { /* would also trigger divide-by-zero */
683 DCCP_WARN("X_recv==0\n");
684 if (hc->rx_x_recv == 0) {
685 DCCP_BUG("stored value of X_recv is zero");
686 return ~0U;
687 }
688 x_recv = hc->rx_x_recv;
689 }
690
691 fval = scaled_div(hc->rx_s, hc->rx_rtt);
692 fval = scaled_div32(fval, x_recv);
693 p = tfrc_calc_x_reverse_lookup(fval);
694
695 ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
696 "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
697
698 return p == 0 ? ~0U : scaled_div(1, p);
699 }
700
ccid3_hc_rx_packet_recv(struct sock * sk,struct sk_buff * skb)701 static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
702 {
703 struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
704 enum ccid3_fback_type do_feedback = CCID3_FBACK_NONE;
705 const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
706 const bool is_data_packet = dccp_data_packet(skb);
707
708 if (unlikely(hc->rx_state == TFRC_RSTATE_NO_DATA)) {
709 if (is_data_packet) {
710 const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
711 do_feedback = CCID3_FBACK_INITIAL;
712 ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
713 hc->rx_s = payload;
714 /*
715 * Not necessary to update rx_bytes_recv here,
716 * since X_recv = 0 for the first feedback packet (cf.
717 * RFC 3448, 6.3) -- gerrit
718 */
719 }
720 goto update_records;
721 }
722
723 if (tfrc_rx_hist_duplicate(&hc->rx_hist, skb))
724 return; /* done receiving */
725
726 if (is_data_packet) {
727 const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
728 /*
729 * Update moving-average of s and the sum of received payload bytes
730 */
731 hc->rx_s = tfrc_ewma(hc->rx_s, payload, 9);
732 hc->rx_bytes_recv += payload;
733 }
734
735 /*
736 * Perform loss detection and handle pending losses
737 */
738 if (tfrc_rx_handle_loss(&hc->rx_hist, &hc->rx_li_hist,
739 skb, ndp, ccid3_first_li, sk)) {
740 do_feedback = CCID3_FBACK_PARAM_CHANGE;
741 goto done_receiving;
742 }
743
744 if (tfrc_rx_hist_loss_pending(&hc->rx_hist))
745 return; /* done receiving */
746
747 /*
748 * Handle data packets: RTT sampling and monitoring p
749 */
750 if (unlikely(!is_data_packet))
751 goto update_records;
752
753 if (!tfrc_lh_is_initialised(&hc->rx_li_hist)) {
754 const u32 sample = tfrc_rx_hist_sample_rtt(&hc->rx_hist, skb);
755 /*
756 * Empty loss history: no loss so far, hence p stays 0.
757 * Sample RTT values, since an RTT estimate is required for the
758 * computation of p when the first loss occurs; RFC 3448, 6.3.1.
759 */
760 if (sample != 0)
761 hc->rx_rtt = tfrc_ewma(hc->rx_rtt, sample, 9);
762
763 } else if (tfrc_lh_update_i_mean(&hc->rx_li_hist, skb)) {
764 /*
765 * Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
766 * has decreased (resp. p has increased), send feedback now.
767 */
768 do_feedback = CCID3_FBACK_PARAM_CHANGE;
769 }
770
771 /*
772 * Check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3
773 */
774 if (SUB16(dccp_hdr(skb)->dccph_ccval, hc->rx_last_counter) > 3)
775 do_feedback = CCID3_FBACK_PERIODIC;
776
777 update_records:
778 tfrc_rx_hist_add_packet(&hc->rx_hist, skb, ndp);
779
780 done_receiving:
781 if (do_feedback)
782 ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
783 }
784
ccid3_hc_rx_init(struct ccid * ccid,struct sock * sk)785 static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
786 {
787 struct ccid3_hc_rx_sock *hc = ccid_priv(ccid);
788
789 hc->rx_state = TFRC_RSTATE_NO_DATA;
790 tfrc_lh_init(&hc->rx_li_hist);
791 return tfrc_rx_hist_alloc(&hc->rx_hist);
792 }
793
ccid3_hc_rx_exit(struct sock * sk)794 static void ccid3_hc_rx_exit(struct sock *sk)
795 {
796 struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
797
798 tfrc_rx_hist_purge(&hc->rx_hist);
799 tfrc_lh_cleanup(&hc->rx_li_hist);
800 }
801
ccid3_hc_rx_get_info(struct sock * sk,struct tcp_info * info)802 static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
803 {
804 info->tcpi_ca_state = ccid3_hc_rx_sk(sk)->rx_state;
805 info->tcpi_options |= TCPI_OPT_TIMESTAMPS;
806 info->tcpi_rcv_rtt = ccid3_hc_rx_sk(sk)->rx_rtt;
807 }
808
ccid3_hc_rx_getsockopt(struct sock * sk,const int optname,int len,u32 __user * optval,int __user * optlen)809 static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
810 u32 __user *optval, int __user *optlen)
811 {
812 const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
813 struct tfrc_rx_info rx_info;
814 const void *val;
815
816 switch (optname) {
817 case DCCP_SOCKOPT_CCID_RX_INFO:
818 if (len < sizeof(rx_info))
819 return -EINVAL;
820 rx_info.tfrcrx_x_recv = hc->rx_x_recv;
821 rx_info.tfrcrx_rtt = hc->rx_rtt;
822 rx_info.tfrcrx_p = tfrc_invert_loss_event_rate(hc->rx_pinv);
823 len = sizeof(rx_info);
824 val = &rx_info;
825 break;
826 default:
827 return -ENOPROTOOPT;
828 }
829
830 if (put_user(len, optlen) || copy_to_user(optval, val, len))
831 return -EFAULT;
832
833 return 0;
834 }
835
836 struct ccid_operations ccid3_ops = {
837 .ccid_id = DCCPC_CCID3,
838 .ccid_name = "TCP-Friendly Rate Control",
839 .ccid_hc_tx_obj_size = sizeof(struct ccid3_hc_tx_sock),
840 .ccid_hc_tx_init = ccid3_hc_tx_init,
841 .ccid_hc_tx_exit = ccid3_hc_tx_exit,
842 .ccid_hc_tx_send_packet = ccid3_hc_tx_send_packet,
843 .ccid_hc_tx_packet_sent = ccid3_hc_tx_packet_sent,
844 .ccid_hc_tx_packet_recv = ccid3_hc_tx_packet_recv,
845 .ccid_hc_tx_parse_options = ccid3_hc_tx_parse_options,
846 .ccid_hc_rx_obj_size = sizeof(struct ccid3_hc_rx_sock),
847 .ccid_hc_rx_init = ccid3_hc_rx_init,
848 .ccid_hc_rx_exit = ccid3_hc_rx_exit,
849 .ccid_hc_rx_insert_options = ccid3_hc_rx_insert_options,
850 .ccid_hc_rx_packet_recv = ccid3_hc_rx_packet_recv,
851 .ccid_hc_rx_get_info = ccid3_hc_rx_get_info,
852 .ccid_hc_tx_get_info = ccid3_hc_tx_get_info,
853 .ccid_hc_rx_getsockopt = ccid3_hc_rx_getsockopt,
854 .ccid_hc_tx_getsockopt = ccid3_hc_tx_getsockopt,
855 };
856
857 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
858 module_param(ccid3_debug, bool, 0644);
859 MODULE_PARM_DESC(ccid3_debug, "Enable CCID-3 debug messages");
860 #endif
861
