source: src/linux/universal/linux-3.18/net/dccp/ccids/ccid2.c @ 31869

Last change on this file since 31869 was 31869, checked in by brainslayer, 6 weeks ago

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1/*
2 *  Copyright (c) 2005, 2006 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
3 *
4 *  Changes to meet Linux coding standards, and DCCP infrastructure fixes.
5 *
6 *  Copyright (c) 2006 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7 *
8 *  This program is free software; you can redistribute it and/or modify
9 *  it under the terms of the GNU General Public License as published by
10 *  the Free Software Foundation; either version 2 of the License, or
11 *  (at your option) any later version.
12 *
13 *  This program is distributed in the hope that it will be useful,
14 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
15 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16 *  GNU General Public License for more details.
17 *
18 *  You should have received a copy of the GNU General Public License
19 *  along with this program; if not, write to the Free Software
20 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 */
22
23/*
24 * This implementation should follow RFC 4341
25 */
26#include <linux/slab.h>
27#include "../feat.h"
28#include "ccid2.h"
29
30
31#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
32static bool ccid2_debug;
33#define ccid2_pr_debug(format, a...)    DCCP_PR_DEBUG(ccid2_debug, format, ##a)
34#else
35#define ccid2_pr_debug(format, a...)
36#endif
37
38static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hc)
39{
40        struct ccid2_seq *seqp;
41        int i;
42
43        /* check if we have space to preserve the pointer to the buffer */
44        if (hc->tx_seqbufc >= (sizeof(hc->tx_seqbuf) /
45                               sizeof(struct ccid2_seq *)))
46                return -ENOMEM;
47
48        /* allocate buffer and initialize linked list */
49        seqp = kmalloc(CCID2_SEQBUF_LEN * sizeof(struct ccid2_seq), gfp_any());
50        if (seqp == NULL)
51                return -ENOMEM;
52
53        for (i = 0; i < (CCID2_SEQBUF_LEN - 1); i++) {
54                seqp[i].ccid2s_next = &seqp[i + 1];
55                seqp[i + 1].ccid2s_prev = &seqp[i];
56        }
57        seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = seqp;
58        seqp->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
59
60        /* This is the first allocation.  Initiate the head and tail.  */
61        if (hc->tx_seqbufc == 0)
62                hc->tx_seqh = hc->tx_seqt = seqp;
63        else {
64                /* link the existing list with the one we just created */
65                hc->tx_seqh->ccid2s_next = seqp;
66                seqp->ccid2s_prev = hc->tx_seqh;
67
68                hc->tx_seqt->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
69                seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = hc->tx_seqt;
70        }
71
72        /* store the original pointer to the buffer so we can free it */
73        hc->tx_seqbuf[hc->tx_seqbufc] = seqp;
74        hc->tx_seqbufc++;
75
76        return 0;
77}
78
79static int ccid2_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
80{
81        if (ccid2_cwnd_network_limited(ccid2_hc_tx_sk(sk)))
82                return CCID_PACKET_WILL_DEQUEUE_LATER;
83        return CCID_PACKET_SEND_AT_ONCE;
84}
85
86static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
87{
88        u32 max_ratio = DIV_ROUND_UP(ccid2_hc_tx_sk(sk)->tx_cwnd, 2);
89
90        /*
91         * Ensure that Ack Ratio does not exceed ceil(cwnd/2), which is (2) from
92         * RFC 4341, 6.1.2. We ignore the statement that Ack Ratio 2 is always
93         * acceptable since this causes starvation/deadlock whenever cwnd < 2.
94         * The same problem arises when Ack Ratio is 0 (ie. Ack Ratio disabled).
95         */
96        if (val == 0 || val > max_ratio) {
97                DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
98                val = max_ratio;
99        }
100        dccp_feat_signal_nn_change(sk, DCCPF_ACK_RATIO,
101                                   min_t(u32, val, DCCPF_ACK_RATIO_MAX));
102}
103
104static void ccid2_check_l_ack_ratio(struct sock *sk)
105{
106        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
107
108        /*
109         * After a loss, idle period, application limited period, or RTO we
110         * need to check that the ack ratio is still less than the congestion
111         * window. Otherwise, we will send an entire congestion window of
112         * packets and got no response because we haven't sent ack ratio
113         * packets yet.
114         * If the ack ratio does need to be reduced, we reduce it to half of
115         * the congestion window (or 1 if that's zero) instead of to the
116         * congestion window. This prevents problems if one ack is lost.
117         */
118        if (dccp_feat_nn_get(sk, DCCPF_ACK_RATIO) > hc->tx_cwnd)
119                ccid2_change_l_ack_ratio(sk, hc->tx_cwnd/2 ? : 1U);
120}
121
122static void ccid2_change_l_seq_window(struct sock *sk, u64 val)
123{
124        dccp_feat_signal_nn_change(sk, DCCPF_SEQUENCE_WINDOW,
125                                   clamp_val(val, DCCPF_SEQ_WMIN,
126                                                  DCCPF_SEQ_WMAX));
127}
128
129static void ccid2_hc_tx_rto_expire(unsigned long data)
130{
131        struct sock *sk = (struct sock *)data;
132        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
133        const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
134
135        bh_lock_sock(sk);
136        if (sock_owned_by_user(sk)) {
137                sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + HZ / 5);
138                goto out;
139        }
140
141        ccid2_pr_debug("RTO_EXPIRE\n");
142
143        /* back-off timer */
144        hc->tx_rto <<= 1;
145        if (hc->tx_rto > DCCP_RTO_MAX)
146                hc->tx_rto = DCCP_RTO_MAX;
147
148        /* adjust pipe, cwnd etc */
149        hc->tx_ssthresh = hc->tx_cwnd / 2;
150        if (hc->tx_ssthresh < 2)
151                hc->tx_ssthresh = 2;
152        hc->tx_cwnd     = 1;
153        hc->tx_pipe     = 0;
154
155        /* clear state about stuff we sent */
156        hc->tx_seqt = hc->tx_seqh;
157        hc->tx_packets_acked = 0;
158
159        /* clear ack ratio state. */
160        hc->tx_rpseq    = 0;
161        hc->tx_rpdupack = -1;
162        ccid2_change_l_ack_ratio(sk, 1);
163
164        /* if we were blocked before, we may now send cwnd=1 packet */
165        if (sender_was_blocked)
166                tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
167        /* restart backed-off timer */
168        sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
169out:
170        bh_unlock_sock(sk);
171        sock_put(sk);
172}
173
174/*
175 *      Congestion window validation (RFC 2861).
176 */
177static bool ccid2_do_cwv = true;
178module_param(ccid2_do_cwv, bool, 0644);
179MODULE_PARM_DESC(ccid2_do_cwv, "Perform RFC2861 Congestion Window Validation");
180
181/**
182 * ccid2_update_used_window  -  Track how much of cwnd is actually used
183 * This is done in addition to CWV. The sender needs to have an idea of how many
184 * packets may be in flight, to set the local Sequence Window value accordingly
185 * (RFC 4340, 7.5.2). The CWV mechanism is exploited to keep track of the
186 * maximum-used window. We use an EWMA low-pass filter to filter out noise.
187 */
188static void ccid2_update_used_window(struct ccid2_hc_tx_sock *hc, u32 new_wnd)
189{
190        hc->tx_expected_wnd = (3 * hc->tx_expected_wnd + new_wnd) / 4;
191}
192
193/* This borrows the code of tcp_cwnd_application_limited() */
194static void ccid2_cwnd_application_limited(struct sock *sk, const u32 now)
195{
196        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
197        /* don't reduce cwnd below the initial window (IW) */
198        u32 init_win = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache),
199            win_used = max(hc->tx_cwnd_used, init_win);
200
201        if (win_used < hc->tx_cwnd) {
202                hc->tx_ssthresh = max(hc->tx_ssthresh,
203                                     (hc->tx_cwnd >> 1) + (hc->tx_cwnd >> 2));
204                hc->tx_cwnd = (hc->tx_cwnd + win_used) >> 1;
205        }
206        hc->tx_cwnd_used  = 0;
207        hc->tx_cwnd_stamp = now;
208
209        ccid2_check_l_ack_ratio(sk);
210}
211
212/* This borrows the code of tcp_cwnd_restart() */
213static void ccid2_cwnd_restart(struct sock *sk, const u32 now)
214{
215        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
216        u32 cwnd = hc->tx_cwnd, restart_cwnd,
217            iwnd = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache);
218
219        hc->tx_ssthresh = max(hc->tx_ssthresh, (cwnd >> 1) + (cwnd >> 2));
220
221        /* don't reduce cwnd below the initial window (IW) */
222        restart_cwnd = min(cwnd, iwnd);
223        cwnd >>= (now - hc->tx_lsndtime) / hc->tx_rto;
224        hc->tx_cwnd = max(cwnd, restart_cwnd);
225
226        hc->tx_cwnd_stamp = now;
227        hc->tx_cwnd_used  = 0;
228
229        ccid2_check_l_ack_ratio(sk);
230}
231
232static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
233{
234        struct dccp_sock *dp = dccp_sk(sk);
235        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
236        const u32 now = ccid2_time_stamp;
237        struct ccid2_seq *next;
238
239        /* slow-start after idle periods (RFC 2581, RFC 2861) */
240        if (ccid2_do_cwv && !hc->tx_pipe &&
241            (s32)(now - hc->tx_lsndtime) >= hc->tx_rto)
242                ccid2_cwnd_restart(sk, now);
243
244        hc->tx_lsndtime = now;
245        hc->tx_pipe    += 1;
246
247        /* see whether cwnd was fully used (RFC 2861), update expected window */
248        if (ccid2_cwnd_network_limited(hc)) {
249                ccid2_update_used_window(hc, hc->tx_cwnd);
250                hc->tx_cwnd_used  = 0;
251                hc->tx_cwnd_stamp = now;
252        } else {
253                if (hc->tx_pipe > hc->tx_cwnd_used)
254                        hc->tx_cwnd_used = hc->tx_pipe;
255
256                ccid2_update_used_window(hc, hc->tx_cwnd_used);
257
258                if (ccid2_do_cwv && (s32)(now - hc->tx_cwnd_stamp) >= hc->tx_rto)
259                        ccid2_cwnd_application_limited(sk, now);
260        }
261
262        hc->tx_seqh->ccid2s_seq   = dp->dccps_gss;
263        hc->tx_seqh->ccid2s_acked = 0;
264        hc->tx_seqh->ccid2s_sent  = now;
265
266        next = hc->tx_seqh->ccid2s_next;
267        /* check if we need to alloc more space */
268        if (next == hc->tx_seqt) {
269                if (ccid2_hc_tx_alloc_seq(hc)) {
270                        DCCP_CRIT("packet history - out of memory!");
271                        /* FIXME: find a more graceful way to bail out */
272                        return;
273                }
274                next = hc->tx_seqh->ccid2s_next;
275                BUG_ON(next == hc->tx_seqt);
276        }
277        hc->tx_seqh = next;
278
279        ccid2_pr_debug("cwnd=%d pipe=%d\n", hc->tx_cwnd, hc->tx_pipe);
280
281        /*
282         * FIXME: The code below is broken and the variables have been removed
283         * from the socket struct. The `ackloss' variable was always set to 0,
284         * and with arsent there are several problems:
285         *  (i) it doesn't just count the number of Acks, but all sent packets;
286         *  (ii) it is expressed in # of packets, not # of windows, so the
287         *  comparison below uses the wrong formula: Appendix A of RFC 4341
288         *  comes up with the number K = cwnd / (R^2 - R) of consecutive windows
289         *  of data with no lost or marked Ack packets. If arsent were the # of
290         *  consecutive Acks received without loss, then Ack Ratio needs to be
291         *  decreased by 1 when
292         *            arsent >=  K * cwnd / R  =  cwnd^2 / (R^3 - R^2)
293         *  where cwnd / R is the number of Acks received per window of data
294         *  (cf. RFC 4341, App. A). The problems are that
295         *  - arsent counts other packets as well;
296         *  - the comparison uses a formula different from RFC 4341;
297         *  - computing a cubic/quadratic equation each time is too complicated.
298         *  Hence a different algorithm is needed.
299         */
300#if 0
301        /* Ack Ratio.  Need to maintain a concept of how many windows we sent */
302        hc->tx_arsent++;
303        /* We had an ack loss in this window... */
304        if (hc->tx_ackloss) {
305                if (hc->tx_arsent >= hc->tx_cwnd) {
306                        hc->tx_arsent  = 0;
307                        hc->tx_ackloss = 0;
308                }
309        } else {
310                /* No acks lost up to now... */
311                /* decrease ack ratio if enough packets were sent */
312                if (dp->dccps_l_ack_ratio > 1) {
313                        /* XXX don't calculate denominator each time */
314                        int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
315                                    dp->dccps_l_ack_ratio;
316
317                        denom = hc->tx_cwnd * hc->tx_cwnd / denom;
318
319                        if (hc->tx_arsent >= denom) {
320                                ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
321                                hc->tx_arsent = 0;
322                        }
323                } else {
324                        /* we can't increase ack ratio further [1] */
325                        hc->tx_arsent = 0; /* or maybe set it to cwnd*/
326                }
327        }
328#endif
329
330        sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
331
332#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
333        do {
334                struct ccid2_seq *seqp = hc->tx_seqt;
335
336                while (seqp != hc->tx_seqh) {
337                        ccid2_pr_debug("out seq=%llu acked=%d time=%u\n",
338                                       (unsigned long long)seqp->ccid2s_seq,
339                                       seqp->ccid2s_acked, seqp->ccid2s_sent);
340                        seqp = seqp->ccid2s_next;
341                }
342        } while (0);
343        ccid2_pr_debug("=========\n");
344#endif
345}
346
347/**
348 * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
349 * This code is almost identical with TCP's tcp_rtt_estimator(), since
350 * - it has a higher sampling frequency (recommended by RFC 1323),
351 * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
352 * - it is simple (cf. more complex proposals such as Eifel timer or research
353 *   which suggests that the gain should be set according to window size),
354 * - in tests it was found to work well with CCID2 [gerrit].
355 */
356static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
357{
358        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
359        long m = mrtt ? : 1;
360
361        if (hc->tx_srtt == 0) {
362                /* First measurement m */
363                hc->tx_srtt = m << 3;
364                hc->tx_mdev = m << 1;
365
366                hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
367                hc->tx_rttvar   = hc->tx_mdev_max;
368
369                hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
370        } else {
371                /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
372                m -= (hc->tx_srtt >> 3);
373                hc->tx_srtt += m;
374
375                /* Similarly, update scaled mdev with regard to |m| */
376                if (m < 0) {
377                        m = -m;
378                        m -= (hc->tx_mdev >> 2);
379                        /*
380                         * This neutralises RTO increase when RTT < SRTT - mdev
381                         * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
382                         * in Linux TCP", USENIX 2002, pp. 49-62).
383                         */
384                        if (m > 0)
385                                m >>= 3;
386                } else {
387                        m -= (hc->tx_mdev >> 2);
388                }
389                hc->tx_mdev += m;
390
391                if (hc->tx_mdev > hc->tx_mdev_max) {
392                        hc->tx_mdev_max = hc->tx_mdev;
393                        if (hc->tx_mdev_max > hc->tx_rttvar)
394                                hc->tx_rttvar = hc->tx_mdev_max;
395                }
396
397                /*
398                 * Decay RTTVAR at most once per flight, exploiting that
399                 *  1) pipe <= cwnd <= Sequence_Window = W  (RFC 4340, 7.5.2)
400                 *  2) AWL = GSS-W+1 <= GAR <= GSS          (RFC 4340, 7.5.1)
401                 * GAR is a useful bound for FlightSize = pipe.
402                 * AWL is probably too low here, as it over-estimates pipe.
403                 */
404                if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
405                        if (hc->tx_mdev_max < hc->tx_rttvar)
406                                hc->tx_rttvar -= (hc->tx_rttvar -
407                                                  hc->tx_mdev_max) >> 2;
408                        hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
409                        hc->tx_mdev_max = tcp_rto_min(sk);
410                }
411        }
412
413        /*
414         * Set RTO from SRTT and RTTVAR
415         * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
416         * This agrees with RFC 4341, 5:
417         *      "Because DCCP does not retransmit data, DCCP does not require
418         *       TCP's recommended minimum timeout of one second".
419         */
420        hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
421
422        if (hc->tx_rto > DCCP_RTO_MAX)
423                hc->tx_rto = DCCP_RTO_MAX;
424}
425
426static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
427                          unsigned int *maxincr)
428{
429        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
430        struct dccp_sock *dp = dccp_sk(sk);
431        int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
432
433        if (hc->tx_cwnd < dp->dccps_l_seq_win &&
434            r_seq_used < dp->dccps_r_seq_win) {
435                if (hc->tx_cwnd < hc->tx_ssthresh) {
436                        if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
437                                hc->tx_cwnd += 1;
438                                *maxincr    -= 1;
439                                hc->tx_packets_acked = 0;
440                        }
441                } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
442                        hc->tx_cwnd += 1;
443                        hc->tx_packets_acked = 0;
444                }
445        }
446
447        /*
448         * Adjust the local sequence window and the ack ratio to allow about
449         * 5 times the number of packets in the network (RFC 4340 7.5.2)
450         */
451        if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
452                ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio * 2);
453        else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
454                ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio / 2 ? : 1U);
455
456        if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
457                ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win * 2);
458        else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
459                ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win / 2);
460
461        /*
462         * FIXME: RTT is sampled several times per acknowledgment (for each
463         * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
464         * This causes the RTT to be over-estimated, since the older entries
465         * in the Ack Vector have earlier sending times.
466         * The cleanest solution is to not use the ccid2s_sent field at all
467         * and instead use DCCP timestamps: requires changes in other places.
468         */
469        ccid2_rtt_estimator(sk, ccid2_time_stamp - seqp->ccid2s_sent);
470}
471
472static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
473{
474        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
475
476        if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
477                ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
478                return;
479        }
480
481        hc->tx_last_cong = ccid2_time_stamp;
482
483        hc->tx_cwnd      = hc->tx_cwnd / 2 ? : 1U;
484        hc->tx_ssthresh  = max(hc->tx_cwnd, 2U);
485
486        ccid2_check_l_ack_ratio(sk);
487}
488
489static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
490                                     u8 option, u8 *optval, u8 optlen)
491{
492        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
493
494        switch (option) {
495        case DCCPO_ACK_VECTOR_0:
496        case DCCPO_ACK_VECTOR_1:
497                return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
498                                              option - DCCPO_ACK_VECTOR_0);
499        }
500        return 0;
501}
502
503static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
504{
505        struct dccp_sock *dp = dccp_sk(sk);
506        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
507        const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
508        struct dccp_ackvec_parsed *avp;
509        u64 ackno, seqno;
510        struct ccid2_seq *seqp;
511        int done = 0;
512        unsigned int maxincr = 0;
513
514        /* check reverse path congestion */
515        seqno = DCCP_SKB_CB(skb)->dccpd_seq;
516
517        /* XXX this whole "algorithm" is broken.  Need to fix it to keep track
518         * of the seqnos of the dupacks so that rpseq and rpdupack are correct
519         * -sorbo.
520         */
521        /* need to bootstrap */
522        if (hc->tx_rpdupack == -1) {
523                hc->tx_rpdupack = 0;
524                hc->tx_rpseq    = seqno;
525        } else {
526                /* check if packet is consecutive */
527                if (dccp_delta_seqno(hc->tx_rpseq, seqno) == 1)
528                        hc->tx_rpseq = seqno;
529                /* it's a later packet */
530                else if (after48(seqno, hc->tx_rpseq)) {
531                        hc->tx_rpdupack++;
532
533                        /* check if we got enough dupacks */
534                        if (hc->tx_rpdupack >= NUMDUPACK) {
535                                hc->tx_rpdupack = -1; /* XXX lame */
536                                hc->tx_rpseq    = 0;
537#ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
538                                /*
539                                 * FIXME: Ack Congestion Control is broken; in
540                                 * the current state instabilities occurred with
541                                 * Ack Ratios greater than 1; causing hang-ups
542                                 * and long RTO timeouts. This needs to be fixed
543                                 * before opening up dynamic changes. -- gerrit
544                                 */
545                                ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
546#endif
547                        }
548                }
549        }
550
551        /* check forward path congestion */
552        if (dccp_packet_without_ack(skb))
553                return;
554
555        /* still didn't send out new data packets */
556        if (hc->tx_seqh == hc->tx_seqt)
557                goto done;
558
559        ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
560        if (after48(ackno, hc->tx_high_ack))
561                hc->tx_high_ack = ackno;
562
563        seqp = hc->tx_seqt;
564        while (before48(seqp->ccid2s_seq, ackno)) {
565                seqp = seqp->ccid2s_next;
566                if (seqp == hc->tx_seqh) {
567                        seqp = hc->tx_seqh->ccid2s_prev;
568                        break;
569                }
570        }
571
572        /*
573         * In slow-start, cwnd can increase up to a maximum of Ack Ratio/2
574         * packets per acknowledgement. Rounding up avoids that cwnd is not
575         * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
576         */
577        if (hc->tx_cwnd < hc->tx_ssthresh)
578                maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
579
580        /* go through all ack vectors */
581        list_for_each_entry(avp, &hc->tx_av_chunks, node) {
582                /* go through this ack vector */
583                for (; avp->len--; avp->vec++) {
584                        u64 ackno_end_rl = SUB48(ackno,
585                                                 dccp_ackvec_runlen(avp->vec));
586
587                        ccid2_pr_debug("ackvec %llu |%u,%u|\n",
588                                       (unsigned long long)ackno,
589                                       dccp_ackvec_state(avp->vec) >> 6,
590                                       dccp_ackvec_runlen(avp->vec));
591                        /* if the seqno we are analyzing is larger than the
592                         * current ackno, then move towards the tail of our
593                         * seqnos.
594                         */
595                        while (after48(seqp->ccid2s_seq, ackno)) {
596                                if (seqp == hc->tx_seqt) {
597                                        done = 1;
598                                        break;
599                                }
600                                seqp = seqp->ccid2s_prev;
601                        }
602                        if (done)
603                                break;
604
605                        /* check all seqnos in the range of the vector
606                         * run length
607                         */
608                        while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
609                                const u8 state = dccp_ackvec_state(avp->vec);
610
611                                /* new packet received or marked */
612                                if (state != DCCPAV_NOT_RECEIVED &&
613                                    !seqp->ccid2s_acked) {
614                                        if (state == DCCPAV_ECN_MARKED)
615                                                ccid2_congestion_event(sk,
616                                                                       seqp);
617                                        else
618                                                ccid2_new_ack(sk, seqp,
619                                                              &maxincr);
620
621                                        seqp->ccid2s_acked = 1;
622                                        ccid2_pr_debug("Got ack for %llu\n",
623                                                       (unsigned long long)seqp->ccid2s_seq);
624                                        hc->tx_pipe--;
625                                }
626                                if (seqp == hc->tx_seqt) {
627                                        done = 1;
628                                        break;
629                                }
630                                seqp = seqp->ccid2s_prev;
631                        }
632                        if (done)
633                                break;
634
635                        ackno = SUB48(ackno_end_rl, 1);
636                }
637                if (done)
638                        break;
639        }
640
641        /* The state about what is acked should be correct now
642         * Check for NUMDUPACK
643         */
644        seqp = hc->tx_seqt;
645        while (before48(seqp->ccid2s_seq, hc->tx_high_ack)) {
646                seqp = seqp->ccid2s_next;
647                if (seqp == hc->tx_seqh) {
648                        seqp = hc->tx_seqh->ccid2s_prev;
649                        break;
650                }
651        }
652        done = 0;
653        while (1) {
654                if (seqp->ccid2s_acked) {
655                        done++;
656                        if (done == NUMDUPACK)
657                                break;
658                }
659                if (seqp == hc->tx_seqt)
660                        break;
661                seqp = seqp->ccid2s_prev;
662        }
663
664        /* If there are at least 3 acknowledgements, anything unacknowledged
665         * below the last sequence number is considered lost
666         */
667        if (done == NUMDUPACK) {
668                struct ccid2_seq *last_acked = seqp;
669
670                /* check for lost packets */
671                while (1) {
672                        if (!seqp->ccid2s_acked) {
673                                ccid2_pr_debug("Packet lost: %llu\n",
674                                               (unsigned long long)seqp->ccid2s_seq);
675                                /* XXX need to traverse from tail -> head in
676                                 * order to detect multiple congestion events in
677                                 * one ack vector.
678                                 */
679                                ccid2_congestion_event(sk, seqp);
680                                hc->tx_pipe--;
681                        }
682                        if (seqp == hc->tx_seqt)
683                                break;
684                        seqp = seqp->ccid2s_prev;
685                }
686
687                hc->tx_seqt = last_acked;
688        }
689
690        /* trim acked packets in tail */
691        while (hc->tx_seqt != hc->tx_seqh) {
692                if (!hc->tx_seqt->ccid2s_acked)
693                        break;
694
695                hc->tx_seqt = hc->tx_seqt->ccid2s_next;
696        }
697
698        /* restart RTO timer if not all outstanding data has been acked */
699        if (hc->tx_pipe == 0)
700                sk_stop_timer(sk, &hc->tx_rtotimer);
701        else
702                sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
703done:
704        /* check if incoming Acks allow pending packets to be sent */
705        if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
706                tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
707        dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
708}
709
710static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
711{
712        struct ccid2_hc_tx_sock *hc = ccid_priv(ccid);
713        struct dccp_sock *dp = dccp_sk(sk);
714        u32 max_ratio;
715
716        /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
717        hc->tx_ssthresh = ~0U;
718
719        /* Use larger initial windows (RFC 4341, section 5). */
720        hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
721        hc->tx_expected_wnd = hc->tx_cwnd;
722
723        /* Make sure that Ack Ratio is enabled and within bounds. */
724        max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
725        if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
726                dp->dccps_l_ack_ratio = max_ratio;
727
728        /* XXX init ~ to window size... */
729        if (ccid2_hc_tx_alloc_seq(hc))
730                return -ENOMEM;
731
732        hc->tx_rto       = DCCP_TIMEOUT_INIT;
733        hc->tx_rpdupack  = -1;
734        hc->tx_last_cong = hc->tx_lsndtime = hc->tx_cwnd_stamp = ccid2_time_stamp;
735        hc->tx_cwnd_used = 0;
736        setup_timer(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire,
737                        (unsigned long)sk);
738        INIT_LIST_HEAD(&hc->tx_av_chunks);
739        return 0;
740}
741
742static void ccid2_hc_tx_exit(struct sock *sk)
743{
744        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
745        int i;
746
747        sk_stop_timer(sk, &hc->tx_rtotimer);
748
749        for (i = 0; i < hc->tx_seqbufc; i++)
750                kfree(hc->tx_seqbuf[i]);
751        hc->tx_seqbufc = 0;
752        dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
753}
754
755static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
756{
757        struct ccid2_hc_rx_sock *hc = ccid2_hc_rx_sk(sk);
758
759        if (!dccp_data_packet(skb))
760                return;
761
762        if (++hc->rx_num_data_pkts >= dccp_sk(sk)->dccps_r_ack_ratio) {
763                dccp_send_ack(sk);
764                hc->rx_num_data_pkts = 0;
765        }
766}
767
768struct ccid_operations ccid2_ops = {
769        .ccid_id                  = DCCPC_CCID2,
770        .ccid_name                = "TCP-like",
771        .ccid_hc_tx_obj_size      = sizeof(struct ccid2_hc_tx_sock),
772        .ccid_hc_tx_init          = ccid2_hc_tx_init,
773        .ccid_hc_tx_exit          = ccid2_hc_tx_exit,
774        .ccid_hc_tx_send_packet   = ccid2_hc_tx_send_packet,
775        .ccid_hc_tx_packet_sent   = ccid2_hc_tx_packet_sent,
776        .ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
777        .ccid_hc_tx_packet_recv   = ccid2_hc_tx_packet_recv,
778        .ccid_hc_rx_obj_size      = sizeof(struct ccid2_hc_rx_sock),
779        .ccid_hc_rx_packet_recv   = ccid2_hc_rx_packet_recv,
780};
781
782#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
783module_param(ccid2_debug, bool, 0644);
784MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
785#endif
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