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Linux/net/dccp/ccids/ccid3.c

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  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
 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 
 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  */
 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  */
 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 
 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  */
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  */
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  */
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 
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  */
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 
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 
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 
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 
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 
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 
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 
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
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 
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 
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 
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  */
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 
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 
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 
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 
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 
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 

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