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Linux/net/dccp/ccids/ccid3.c

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  1 /*
  2  *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
  3  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
  4  *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
  5  *
  6  *  An implementation of the DCCP protocol
  7  *
  8  *  This code has been developed by the University of Waikato WAND
  9  *  research group. For further information please see http://www.wand.net.nz/
 10  *
 11  *  This code also uses code from Lulea University, rereleased as GPL by its
 12  *  authors:
 13  *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
 14  *
 15  *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
 16  *  and to make it work as a loadable module in the DCCP stack written by
 17  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
 18  *
 19  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 20  *
 21  *  This program is free software; you can redistribute it and/or modify
 22  *  it under the terms of the GNU General Public License as published by
 23  *  the Free Software Foundation; either version 2 of the License, or
 24  *  (at your option) any later version.
 25  *
 26  *  This program is distributed in the hope that it will be useful,
 27  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 28  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 29  *  GNU General Public License for more details.
 30  *
 31  *  You should have received a copy of the GNU General Public License
 32  *  along with this program; if not, write to the Free Software
 33  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 34  */
 35 #include "../dccp.h"
 36 #include "ccid3.h"
 37 
 38 #include <asm/unaligned.h>
 39 
 40 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
 41 static bool ccid3_debug;
 42 #define ccid3_pr_debug(format, a...)    DCCP_PR_DEBUG(ccid3_debug, format, ##a)
 43 #else
 44 #define ccid3_pr_debug(format, a...)
 45 #endif
 46 
 47 /*
 48  *      Transmitter Half-Connection Routines
 49  */
 50 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
 51 static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
 52 {
 53         static const char *const ccid3_state_names[] = {
 54         [TFRC_SSTATE_NO_SENT]  = "NO_SENT",
 55         [TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
 56         [TFRC_SSTATE_FBACK]    = "FBACK",
 57         };
 58 
 59         return ccid3_state_names[state];
 60 }
 61 #endif
 62 
 63 static void ccid3_hc_tx_set_state(struct sock *sk,
 64                                   enum ccid3_hc_tx_states state)
 65 {
 66         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 67         enum ccid3_hc_tx_states oldstate = hc->tx_state;
 68 
 69         ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
 70                        dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
 71                        ccid3_tx_state_name(state));
 72         WARN_ON(state == oldstate);
 73         hc->tx_state = state;
 74 }
 75 
 76 /*
 77  * Compute the initial sending rate X_init in the manner of RFC 3390:
 78  *
 79  *      X_init  =  min(4 * s, max(2 * s, 4380 bytes)) / RTT
 80  *
 81  * Note that RFC 3390 uses MSS, RFC 4342 refers to RFC 3390, and rfc3448bis
 82  * (rev-02) clarifies the use of RFC 3390 with regard to the above formula.
 83  * For consistency with other parts of the code, X_init is scaled by 2^6.
 84  */
 85 static inline u64 rfc3390_initial_rate(struct sock *sk)
 86 {
 87         const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 88         const __u32 w_init = clamp_t(__u32, 4380U, 2 * hc->tx_s, 4 * hc->tx_s);
 89 
 90         return scaled_div(w_init << 6, hc->tx_rtt);
 91 }
 92 
 93 /**
 94  * ccid3_update_send_interval  -  Calculate new t_ipi = s / X_inst
 95  * This respects the granularity of X_inst (64 * bytes/second).
 96  */
 97 static void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hc)
 98 {
 99         hc->tx_t_ipi = scaled_div32(((u64)hc->tx_s) << 6, hc->tx_x);
100 
101         DCCP_BUG_ON(hc->tx_t_ipi == 0);
102         ccid3_pr_debug("t_ipi=%u, s=%u, X=%u\n", hc->tx_t_ipi,
103                        hc->tx_s, (unsigned int)(hc->tx_x >> 6));
104 }
105 
106 static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hc, ktime_t now)
107 {
108         u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count);
109 
110         return delta / hc->tx_rtt;
111 }
112 
113 /**
114  * ccid3_hc_tx_update_x  -  Update allowed sending rate X
115  * @stamp: most recent time if available - can be left NULL.
116  *
117  * This function tracks draft rfc3448bis, check there for latest details.
118  *
119  * Note: X and X_recv are both stored in units of 64 * bytes/second, to support
120  *       fine-grained resolution of sending rates. This requires scaling by 2^6
121  *       throughout the code. Only X_calc is unscaled (in bytes/second).
122  *
123  */
124 static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
125 {
126         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
127         __u64 min_rate = 2 * hc->tx_x_recv;
128         const __u64 old_x = hc->tx_x;
129         ktime_t now = stamp ? *stamp : ktime_get_real();
130 
131         /*
132          * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
133          * when idling [RFC 4342, 5.1]. Definition of idling is from rfc3448bis:
134          * a sender is idle if it has not sent anything over a 2-RTT-period.
135          * For consistency with X and X_recv, min_rate is also scaled by 2^6.
136          */
137         if (ccid3_hc_tx_idle_rtt(hc, now) >= 2) {
138                 min_rate = rfc3390_initial_rate(sk);
139                 min_rate = max(min_rate, 2 * hc->tx_x_recv);
140         }
141 
142         if (hc->tx_p > 0) {
143 
144                 hc->tx_x = min(((__u64)hc->tx_x_calc) << 6, min_rate);
145                 hc->tx_x = max(hc->tx_x, (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
146 
147         } else if (ktime_us_delta(now, hc->tx_t_ld) - (s64)hc->tx_rtt >= 0) {
148 
149                 hc->tx_x = min(2 * hc->tx_x, min_rate);
150                 hc->tx_x = max(hc->tx_x,
151                                scaled_div(((__u64)hc->tx_s) << 6, hc->tx_rtt));
152                 hc->tx_t_ld = now;
153         }
154 
155         if (hc->tx_x != old_x) {
156                 ccid3_pr_debug("X_prev=%u, X_now=%u, X_calc=%u, "
157                                "X_recv=%u\n", (unsigned int)(old_x >> 6),
158                                (unsigned int)(hc->tx_x >> 6), hc->tx_x_calc,
159                                (unsigned int)(hc->tx_x_recv >> 6));
160 
161                 ccid3_update_send_interval(hc);
162         }
163 }
164 
165 /**
166  *      ccid3_hc_tx_update_s - Track the mean packet size `s'
167  *      @len: DCCP packet payload size in bytes
168  *
169  *      cf. RFC 4342, 5.3 and  RFC 3448, 4.1
170  */
171 static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hc, int len)
172 {
173         const u16 old_s = hc->tx_s;
174 
175         hc->tx_s = tfrc_ewma(hc->tx_s, len, 9);
176 
177         if (hc->tx_s != old_s)
178                 ccid3_update_send_interval(hc);
179 }
180 
181 /*
182  *      Update Window Counter using the algorithm from [RFC 4342, 8.1].
183  *      As elsewhere, RTT > 0 is assumed by using dccp_sample_rtt().
184  */
185 static inline void ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock *hc,
186                                                 ktime_t now)
187 {
188         u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count),
189             quarter_rtts = (4 * delta) / hc->tx_rtt;
190 
191         if (quarter_rtts > 0) {
192                 hc->tx_t_last_win_count = now;
193                 hc->tx_last_win_count  += min(quarter_rtts, 5U);
194                 hc->tx_last_win_count  &= 0xF;          /* mod 16 */
195         }
196 }
197 
198 static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
199 {
200         struct sock *sk = (struct sock *)data;
201         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
202         unsigned long t_nfb = USEC_PER_SEC / 5;
203 
204         bh_lock_sock(sk);
205         if (sock_owned_by_user(sk)) {
206                 /* Try again later. */
207                 /* XXX: set some sensible MIB */
208                 goto restart_timer;
209         }
210 
211         ccid3_pr_debug("%s(%p, state=%s) - entry\n", dccp_role(sk), sk,
212                        ccid3_tx_state_name(hc->tx_state));
213 
214         /* Ignore and do not restart after leaving the established state */
215         if ((1 << sk->sk_state) & ~(DCCPF_OPEN | DCCPF_PARTOPEN))
216                 goto out;
217 
218         /* Reset feedback state to "no feedback received" */
219         if (hc->tx_state == TFRC_SSTATE_FBACK)
220                 ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
221 
222         /*
223          * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
224          * RTO is 0 if and only if no feedback has been received yet.
225          */
226         if (hc->tx_t_rto == 0 || hc->tx_p == 0) {
227 
228                 /* halve send rate directly */
229                 hc->tx_x = max(hc->tx_x / 2,
230                                (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
231                 ccid3_update_send_interval(hc);
232         } else {
233                 /*
234                  *  Modify the cached value of X_recv
235                  *
236                  *  If (X_calc > 2 * X_recv)
237                  *    X_recv = max(X_recv / 2, s / (2 * t_mbi));
238                  *  Else
239                  *    X_recv = X_calc / 4;
240                  *
241                  *  Note that X_recv is scaled by 2^6 while X_calc is not
242                  */
243                 if (hc->tx_x_calc > (hc->tx_x_recv >> 5))
244                         hc->tx_x_recv =
245                                 max(hc->tx_x_recv / 2,
246                                     (((__u64)hc->tx_s) << 6) / (2*TFRC_T_MBI));
247                 else {
248                         hc->tx_x_recv = hc->tx_x_calc;
249                         hc->tx_x_recv <<= 4;
250                 }
251                 ccid3_hc_tx_update_x(sk, NULL);
252         }
253         ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
254                         (unsigned long long)hc->tx_x);
255 
256         /*
257          * Set new timeout for the nofeedback timer.
258          * See comments in packet_recv() regarding the value of t_RTO.
259          */
260         if (unlikely(hc->tx_t_rto == 0))        /* no feedback received yet */
261                 t_nfb = TFRC_INITIAL_TIMEOUT;
262         else
263                 t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
264 
265 restart_timer:
266         sk_reset_timer(sk, &hc->tx_no_feedback_timer,
267                            jiffies + usecs_to_jiffies(t_nfb));
268 out:
269         bh_unlock_sock(sk);
270         sock_put(sk);
271 }
272 
273 /**
274  * ccid3_hc_tx_send_packet  -  Delay-based dequeueing of TX packets
275  * @skb: next packet candidate to send on @sk
276  *
277  * This function uses the convention of ccid_packet_dequeue_eval() and
278  * returns a millisecond-delay value between 0 and t_mbi = 64000 msec.
279  */
280 static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
281 {
282         struct dccp_sock *dp = dccp_sk(sk);
283         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
284         ktime_t now = ktime_get_real();
285         s64 delay;
286 
287         /*
288          * This function is called only for Data and DataAck packets. Sending
289          * zero-sized Data(Ack)s is theoretically possible, but for congestion
290          * control this case is pathological - ignore it.
291          */
292         if (unlikely(skb->len == 0))
293                 return -EBADMSG;
294 
295         if (hc->tx_state == TFRC_SSTATE_NO_SENT) {
296                 sk_reset_timer(sk, &hc->tx_no_feedback_timer, (jiffies +
297                                usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
298                 hc->tx_last_win_count   = 0;
299                 hc->tx_t_last_win_count = now;
300 
301                 /* Set t_0 for initial packet */
302                 hc->tx_t_nom = now;
303 
304                 hc->tx_s = skb->len;
305 
306                 /*
307                  * Use initial RTT sample when available: recommended by erratum
308                  * to RFC 4342. This implements the initialisation procedure of
309                  * draft rfc3448bis, section 4.2. Remember, X is scaled by 2^6.
310                  */
311                 if (dp->dccps_syn_rtt) {
312                         ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
313                         hc->tx_rtt  = dp->dccps_syn_rtt;
314                         hc->tx_x    = rfc3390_initial_rate(sk);
315                         hc->tx_t_ld = now;
316                 } else {
317                         /*
318                          * Sender does not have RTT sample:
319                          * - set fallback RTT (RFC 4340, 3.4) since a RTT value
320                          *   is needed in several parts (e.g.  window counter);
321                          * - set sending rate X_pps = 1pps as per RFC 3448, 4.2.
322                          */
323                         hc->tx_rtt = DCCP_FALLBACK_RTT;
324                         hc->tx_x   = hc->tx_s;
325                         hc->tx_x <<= 6;
326                 }
327                 ccid3_update_send_interval(hc);
328 
329                 ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
330 
331         } else {
332                 delay = ktime_us_delta(hc->tx_t_nom, now);
333                 ccid3_pr_debug("delay=%ld\n", (long)delay);
334                 /*
335                  *      Scheduling of packet transmissions (RFC 5348, 8.3)
336                  *
337                  * if (t_now > t_nom - delta)
338                  *       // send the packet now
339                  * else
340                  *       // send the packet in (t_nom - t_now) milliseconds.
341                  */
342                 if (delay >= TFRC_T_DELTA)
343                         return (u32)delay / USEC_PER_MSEC;
344 
345                 ccid3_hc_tx_update_win_count(hc, now);
346         }
347 
348         /* prepare to send now (add options etc.) */
349         dp->dccps_hc_tx_insert_options = 1;
350         DCCP_SKB_CB(skb)->dccpd_ccval  = hc->tx_last_win_count;
351 
352         /* set the nominal send time for the next following packet */
353         hc->tx_t_nom = ktime_add_us(hc->tx_t_nom, hc->tx_t_ipi);
354         return CCID_PACKET_SEND_AT_ONCE;
355 }
356 
357 static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)
358 {
359         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
360 
361         ccid3_hc_tx_update_s(hc, len);
362 
363         if (tfrc_tx_hist_add(&hc->tx_hist, dccp_sk(sk)->dccps_gss))
364                 DCCP_CRIT("packet history - out of memory!");
365 }
366 
367 static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
368 {
369         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
370         struct tfrc_tx_hist_entry *acked;
371         ktime_t now;
372         unsigned long t_nfb;
373         u32 r_sample;
374 
375         /* we are only interested in ACKs */
376         if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
377               DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
378                 return;
379         /*
380          * Locate the acknowledged packet in the TX history.
381          *
382          * Returning "entry not found" here can for instance happen when
383          *  - the host has not sent out anything (e.g. a passive server),
384          *  - the Ack is outdated (packet with higher Ack number was received),
385          *  - it is a bogus Ack (for a packet not sent on this connection).
386          */
387         acked = tfrc_tx_hist_find_entry(hc->tx_hist, dccp_hdr_ack_seq(skb));
388         if (acked == NULL)
389                 return;
390         /* For the sake of RTT sampling, ignore/remove all older entries */
391         tfrc_tx_hist_purge(&acked->next);
392 
393         /* Update the moving average for the RTT estimate (RFC 3448, 4.3) */
394         now       = ktime_get_real();
395         r_sample  = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));
396         hc->tx_rtt = tfrc_ewma(hc->tx_rtt, r_sample, 9);
397 
398         /*
399          * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
400          */
401         if (hc->tx_state == TFRC_SSTATE_NO_FBACK) {
402                 ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
403 
404                 if (hc->tx_t_rto == 0) {
405                         /*
406                          * Initial feedback packet: Larger Initial Windows (4.2)
407                          */
408                         hc->tx_x    = rfc3390_initial_rate(sk);
409                         hc->tx_t_ld = now;
410 
411                         ccid3_update_send_interval(hc);
412 
413                         goto done_computing_x;
414                 } else if (hc->tx_p == 0) {
415                         /*
416                          * First feedback after nofeedback timer expiry (4.3)
417                          */
418                         goto done_computing_x;
419                 }
420         }
421 
422         /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
423         if (hc->tx_p > 0)
424                 hc->tx_x_calc = tfrc_calc_x(hc->tx_s, hc->tx_rtt, hc->tx_p);
425         ccid3_hc_tx_update_x(sk, &now);
426 
427 done_computing_x:
428         ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
429                                "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
430                                dccp_role(sk), sk, hc->tx_rtt, r_sample,
431                                hc->tx_s, hc->tx_p, hc->tx_x_calc,
432                                (unsigned int)(hc->tx_x_recv >> 6),
433                                (unsigned int)(hc->tx_x >> 6));
434 
435         /* unschedule no feedback timer */
436         sk_stop_timer(sk, &hc->tx_no_feedback_timer);
437 
438         /*
439          * As we have calculated new ipi, delta, t_nom it is possible
440          * that we now can send a packet, so wake up dccp_wait_for_ccid
441          */
442         sk->sk_write_space(sk);
443 
444         /*
445          * Update timeout interval for the nofeedback timer. In order to control
446          * rate halving on networks with very low RTTs (<= 1 ms), use per-route
447          * tunable RTAX_RTO_MIN value as the lower bound.
448          */
449         hc->tx_t_rto = max_t(u32, 4 * hc->tx_rtt,
450                                   USEC_PER_SEC/HZ * tcp_rto_min(sk));
451         /*
452          * Schedule no feedback timer to expire in
453          * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
454          */
455         t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
456 
457         ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
458                        "expire in %lu jiffies (%luus)\n",
459                        dccp_role(sk), sk, usecs_to_jiffies(t_nfb), t_nfb);
460 
461         sk_reset_timer(sk, &hc->tx_no_feedback_timer,
462                            jiffies + usecs_to_jiffies(t_nfb));
463 }
464 
465 static int ccid3_hc_tx_parse_options(struct sock *sk, u8 packet_type,
466                                      u8 option, u8 *optval, u8 optlen)
467 {
468         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
469         __be32 opt_val;
470 
471         switch (option) {
472         case TFRC_OPT_RECEIVE_RATE:
473         case TFRC_OPT_LOSS_EVENT_RATE:
474                 /* Must be ignored on Data packets, cf. RFC 4342 8.3 and 8.5 */
475                 if (packet_type == DCCP_PKT_DATA)
476                         break;
477                 if (unlikely(optlen != 4)) {
478                         DCCP_WARN("%s(%p), invalid len %d for %u\n",
479                                   dccp_role(sk), sk, optlen, option);
480                         return -EINVAL;
481                 }
482                 opt_val = ntohl(get_unaligned((__be32 *)optval));
483 
484                 if (option == TFRC_OPT_RECEIVE_RATE) {
485                         /* Receive Rate is kept in units of 64 bytes/second */
486                         hc->tx_x_recv = opt_val;
487                         hc->tx_x_recv <<= 6;
488 
489                         ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
490                                        dccp_role(sk), sk, opt_val);
491                 } else {
492                         /* Update the fixpoint Loss Event Rate fraction */
493                         hc->tx_p = tfrc_invert_loss_event_rate(opt_val);
494 
495                         ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
496                                        dccp_role(sk), sk, opt_val);
497                 }
498         }
499         return 0;
500 }
501 
502 static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
503 {
504         struct ccid3_hc_tx_sock *hc = ccid_priv(ccid);
505 
506         hc->tx_state = TFRC_SSTATE_NO_SENT;
507         hc->tx_hist  = NULL;
508         setup_timer(&hc->tx_no_feedback_timer,
509                         ccid3_hc_tx_no_feedback_timer, (unsigned long)sk);
510         return 0;
511 }
512 
513 static void ccid3_hc_tx_exit(struct sock *sk)
514 {
515         struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
516 
517         sk_stop_timer(sk, &hc->tx_no_feedback_timer);
518         tfrc_tx_hist_purge(&hc->tx_hist);
519 }
520 
521 static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
522 {
523         info->tcpi_rto = ccid3_hc_tx_sk(sk)->tx_t_rto;
524         info->tcpi_rtt = ccid3_hc_tx_sk(sk)->tx_rtt;
525 }
526 
527 static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
528                                   u32 __user *optval, int __user *optlen)
529 {
530         const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
531         struct tfrc_tx_info tfrc;
532         const void *val;
533 
534         switch (optname) {
535         case DCCP_SOCKOPT_CCID_TX_INFO:
536                 if (len < sizeof(tfrc))
537                         return -EINVAL;
538                 memset(&tfrc, 0, sizeof(tfrc));
539                 tfrc.tfrctx_x      = hc->tx_x;
540                 tfrc.tfrctx_x_recv = hc->tx_x_recv;
541                 tfrc.tfrctx_x_calc = hc->tx_x_calc;
542                 tfrc.tfrctx_rtt    = hc->tx_rtt;
543                 tfrc.tfrctx_p      = hc->tx_p;
544                 tfrc.tfrctx_rto    = hc->tx_t_rto;
545                 tfrc.tfrctx_ipi    = hc->tx_t_ipi;
546                 len = sizeof(tfrc);
547                 val = &tfrc;
548                 break;
549         default:
550                 return -ENOPROTOOPT;
551         }
552 
553         if (put_user(len, optlen) || copy_to_user(optval, val, len))
554                 return -EFAULT;
555 
556         return 0;
557 }
558 
559 /*
560  *      Receiver Half-Connection Routines
561  */
562 
563 /* CCID3 feedback types */
564 enum ccid3_fback_type {
565         CCID3_FBACK_NONE = 0,
566         CCID3_FBACK_INITIAL,
567         CCID3_FBACK_PERIODIC,
568         CCID3_FBACK_PARAM_CHANGE
569 };
570 
571 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
572 static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
573 {
574         static const char *const ccid3_rx_state_names[] = {
575         [TFRC_RSTATE_NO_DATA] = "NO_DATA",
576         [TFRC_RSTATE_DATA]    = "DATA",
577         };
578 
579         return ccid3_rx_state_names[state];
580 }
581 #endif
582 
583 static void ccid3_hc_rx_set_state(struct sock *sk,
584                                   enum ccid3_hc_rx_states state)
585 {
586         struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
587         enum ccid3_hc_rx_states oldstate = hc->rx_state;
588 
589         ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
590                        dccp_role(sk), sk, ccid3_rx_state_name(oldstate),
591                        ccid3_rx_state_name(state));
592         WARN_ON(state == oldstate);
593         hc->rx_state = state;
594 }
595 
596 static void ccid3_hc_rx_send_feedback(struct sock *sk,
597                                       const struct sk_buff *skb,
598                                       enum ccid3_fback_type fbtype)
599 {
600         struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
601         struct dccp_sock *dp = dccp_sk(sk);
602         ktime_t now = ktime_get_real();
603         s64 delta = 0;
604 
605         switch (fbtype) {
606         case CCID3_FBACK_INITIAL:
607                 hc->rx_x_recv = 0;
608                 hc->rx_pinv   = ~0U;   /* see RFC 4342, 8.5 */
609                 break;
610         case CCID3_FBACK_PARAM_CHANGE:
611                 /*
612                  * When parameters change (new loss or p > p_prev), we do not
613                  * have a reliable estimate for R_m of [RFC 3448, 6.2] and so
614                  * need to  reuse the previous value of X_recv. However, when
615                  * X_recv was 0 (due to early loss), this would kill X down to
616                  * s/t_mbi (i.e. one packet in 64 seconds).
617                  * To avoid such drastic reduction, we approximate X_recv as
618                  * the number of bytes since last feedback.
619                  * This is a safe fallback, since X is bounded above by X_calc.
620                  */
621                 if (hc->rx_x_recv > 0)
622                         break;
623                 /* fall through */
624         case CCID3_FBACK_PERIODIC:
625                 delta = ktime_us_delta(now, hc->rx_tstamp_last_feedback);
626                 if (delta <= 0)
627                         DCCP_BUG("delta (%ld) <= 0", (long)delta);
628                 else
629                         hc->rx_x_recv = scaled_div32(hc->rx_bytes_recv, delta);
630                 break;
631         default:
632                 return;
633         }
634 
635         ccid3_pr_debug("Interval %ldusec, X_recv=%u, 1/p=%u\n", (long)delta,
636                        hc->rx_x_recv, hc->rx_pinv);
637 
638         hc->rx_tstamp_last_feedback = now;
639         hc->rx_last_counter         = dccp_hdr(skb)->dccph_ccval;
640         hc->rx_bytes_recv           = 0;
641 
642         dp->dccps_hc_rx_insert_options = 1;
643         dccp_send_ack(sk);
644 }
645 
646 static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
647 {
648         const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
649         __be32 x_recv, pinv;
650 
651         if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
652                 return 0;
653 
654         if (dccp_packet_without_ack(skb))
655                 return 0;
656 
657         x_recv = htonl(hc->rx_x_recv);
658         pinv   = htonl(hc->rx_pinv);
659 
660         if (dccp_insert_option(skb, TFRC_OPT_LOSS_EVENT_RATE,
661                                &pinv, sizeof(pinv)) ||
662             dccp_insert_option(skb, TFRC_OPT_RECEIVE_RATE,
663                                &x_recv, sizeof(x_recv)))
664                 return -1;
665 
666         return 0;
667 }
668 
669 /**
670  * ccid3_first_li  -  Implements [RFC 5348, 6.3.1]
671  *
672  * Determine the length of the first loss interval via inverse lookup.
673  * Assume that X_recv can be computed by the throughput equation
674  *                  s
675  *      X_recv = --------
676  *               R * fval
677  * Find some p such that f(p) = fval; return 1/p (scaled).
678  */
679 static u32 ccid3_first_li(struct sock *sk)
680 {
681         struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
682         u32 x_recv, p, delta;
683         u64 fval;
684 
685         if (hc->rx_rtt == 0) {
686                 DCCP_WARN("No RTT estimate available, using fallback RTT\n");
687                 hc->rx_rtt = DCCP_FALLBACK_RTT;
688         }
689 
690         delta  = ktime_to_us(net_timedelta(hc->rx_tstamp_last_feedback));
691         x_recv = scaled_div32(hc->rx_bytes_recv, delta);
692         if (x_recv == 0) {              /* would also trigger divide-by-zero */
693                 DCCP_WARN("X_recv==0\n");
694                 if (hc->rx_x_recv == 0) {
695                         DCCP_BUG("stored value of X_recv is zero");
696                         return ~0U;
697                 }
698                 x_recv = hc->rx_x_recv;
699         }
700 
701         fval = scaled_div(hc->rx_s, hc->rx_rtt);
702         fval = scaled_div32(fval, x_recv);
703         p = tfrc_calc_x_reverse_lookup(fval);
704 
705         ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
706                        "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
707 
708         return p == 0 ? ~0U : scaled_div(1, p);
709 }
710 
711 static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
712 {
713         struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
714         enum ccid3_fback_type do_feedback = CCID3_FBACK_NONE;
715         const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
716         const bool is_data_packet = dccp_data_packet(skb);
717 
718         if (unlikely(hc->rx_state == TFRC_RSTATE_NO_DATA)) {
719                 if (is_data_packet) {
720                         const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
721                         do_feedback = CCID3_FBACK_INITIAL;
722                         ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
723                         hc->rx_s = payload;
724                         /*
725                          * Not necessary to update rx_bytes_recv here,
726                          * since X_recv = 0 for the first feedback packet (cf.
727                          * RFC 3448, 6.3) -- gerrit
728                          */
729                 }
730                 goto update_records;
731         }
732 
733         if (tfrc_rx_hist_duplicate(&hc->rx_hist, skb))
734                 return; /* done receiving */
735 
736         if (is_data_packet) {
737                 const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
738                 /*
739                  * Update moving-average of s and the sum of received payload bytes
740                  */
741                 hc->rx_s = tfrc_ewma(hc->rx_s, payload, 9);
742                 hc->rx_bytes_recv += payload;
743         }
744 
745         /*
746          * Perform loss detection and handle pending losses
747          */
748         if (tfrc_rx_handle_loss(&hc->rx_hist, &hc->rx_li_hist,
749                                 skb, ndp, ccid3_first_li, sk)) {
750                 do_feedback = CCID3_FBACK_PARAM_CHANGE;
751                 goto done_receiving;
752         }
753 
754         if (tfrc_rx_hist_loss_pending(&hc->rx_hist))
755                 return; /* done receiving */
756 
757         /*
758          * Handle data packets: RTT sampling and monitoring p
759          */
760         if (unlikely(!is_data_packet))
761                 goto update_records;
762 
763         if (!tfrc_lh_is_initialised(&hc->rx_li_hist)) {
764                 const u32 sample = tfrc_rx_hist_sample_rtt(&hc->rx_hist, skb);
765                 /*
766                  * Empty loss history: no loss so far, hence p stays 0.
767                  * Sample RTT values, since an RTT estimate is required for the
768                  * computation of p when the first loss occurs; RFC 3448, 6.3.1.
769                  */
770                 if (sample != 0)
771                         hc->rx_rtt = tfrc_ewma(hc->rx_rtt, sample, 9);
772 
773         } else if (tfrc_lh_update_i_mean(&hc->rx_li_hist, skb)) {
774                 /*
775                  * Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
776                  * has decreased (resp. p has increased), send feedback now.
777                  */
778                 do_feedback = CCID3_FBACK_PARAM_CHANGE;
779         }
780 
781         /*
782          * Check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3
783          */
784         if (SUB16(dccp_hdr(skb)->dccph_ccval, hc->rx_last_counter) > 3)
785                 do_feedback = CCID3_FBACK_PERIODIC;
786 
787 update_records:
788         tfrc_rx_hist_add_packet(&hc->rx_hist, skb, ndp);
789 
790 done_receiving:
791         if (do_feedback)
792                 ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
793 }
794 
795 static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
796 {
797         struct ccid3_hc_rx_sock *hc = ccid_priv(ccid);
798 
799         hc->rx_state = TFRC_RSTATE_NO_DATA;
800         tfrc_lh_init(&hc->rx_li_hist);
801         return tfrc_rx_hist_alloc(&hc->rx_hist);
802 }
803 
804 static void ccid3_hc_rx_exit(struct sock *sk)
805 {
806         struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
807 
808         tfrc_rx_hist_purge(&hc->rx_hist);
809         tfrc_lh_cleanup(&hc->rx_li_hist);
810 }
811 
812 static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
813 {
814         info->tcpi_ca_state = ccid3_hc_rx_sk(sk)->rx_state;
815         info->tcpi_options  |= TCPI_OPT_TIMESTAMPS;
816         info->tcpi_rcv_rtt  = ccid3_hc_rx_sk(sk)->rx_rtt;
817 }
818 
819 static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
820                                   u32 __user *optval, int __user *optlen)
821 {
822         const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
823         struct tfrc_rx_info rx_info;
824         const void *val;
825 
826         switch (optname) {
827         case DCCP_SOCKOPT_CCID_RX_INFO:
828                 if (len < sizeof(rx_info))
829                         return -EINVAL;
830                 rx_info.tfrcrx_x_recv = hc->rx_x_recv;
831                 rx_info.tfrcrx_rtt    = hc->rx_rtt;
832                 rx_info.tfrcrx_p      = tfrc_invert_loss_event_rate(hc->rx_pinv);
833                 len = sizeof(rx_info);
834                 val = &rx_info;
835                 break;
836         default:
837                 return -ENOPROTOOPT;
838         }
839 
840         if (put_user(len, optlen) || copy_to_user(optval, val, len))
841                 return -EFAULT;
842 
843         return 0;
844 }
845 
846 struct ccid_operations ccid3_ops = {
847         .ccid_id                   = DCCPC_CCID3,
848         .ccid_name                 = "TCP-Friendly Rate Control",
849         .ccid_hc_tx_obj_size       = sizeof(struct ccid3_hc_tx_sock),
850         .ccid_hc_tx_init           = ccid3_hc_tx_init,
851         .ccid_hc_tx_exit           = ccid3_hc_tx_exit,
852         .ccid_hc_tx_send_packet    = ccid3_hc_tx_send_packet,
853         .ccid_hc_tx_packet_sent    = ccid3_hc_tx_packet_sent,
854         .ccid_hc_tx_packet_recv    = ccid3_hc_tx_packet_recv,
855         .ccid_hc_tx_parse_options  = ccid3_hc_tx_parse_options,
856         .ccid_hc_rx_obj_size       = sizeof(struct ccid3_hc_rx_sock),
857         .ccid_hc_rx_init           = ccid3_hc_rx_init,
858         .ccid_hc_rx_exit           = ccid3_hc_rx_exit,
859         .ccid_hc_rx_insert_options = ccid3_hc_rx_insert_options,
860         .ccid_hc_rx_packet_recv    = ccid3_hc_rx_packet_recv,
861         .ccid_hc_rx_get_info       = ccid3_hc_rx_get_info,
862         .ccid_hc_tx_get_info       = ccid3_hc_tx_get_info,
863         .ccid_hc_rx_getsockopt     = ccid3_hc_rx_getsockopt,
864         .ccid_hc_tx_getsockopt     = ccid3_hc_tx_getsockopt,
865 };
866 
867 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
868 module_param(ccid3_debug, bool, 0644);
869 MODULE_PARM_DESC(ccid3_debug, "Enable CCID-3 debug messages");
870 #endif
871 

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