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 dccp_tasklet_schedule(struct sock *sk)
130{
131	struct tasklet_struct *t = &dccp_sk(sk)->dccps_xmitlet;
132
133	if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
134		sock_hold(sk);
135		__tasklet_schedule(t);
136	}
137}
138
139static void ccid2_hc_tx_rto_expire(struct timer_list *t)
140{
141	struct ccid2_hc_tx_sock *hc = from_timer(hc, t, tx_rtotimer);
142	struct sock *sk = hc->sk;
143	const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
144
145	bh_lock_sock(sk);
146	if (sock_owned_by_user(sk)) {
147		sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + HZ / 5);
148		goto out;
149	}
150
151	ccid2_pr_debug("RTO_EXPIRE\n");
152
153	if (sk->sk_state == DCCP_CLOSED)
154		goto out;
155
156	/* back-off timer */
157	hc->tx_rto <<= 1;
158	if (hc->tx_rto > DCCP_RTO_MAX)
159		hc->tx_rto = DCCP_RTO_MAX;
160
161	/* adjust pipe, cwnd etc */
162	hc->tx_ssthresh = hc->tx_cwnd / 2;
163	if (hc->tx_ssthresh < 2)
164		hc->tx_ssthresh = 2;
165	hc->tx_cwnd	= 1;
166	hc->tx_pipe	= 0;
167
168	/* clear state about stuff we sent */
169	hc->tx_seqt = hc->tx_seqh;
170	hc->tx_packets_acked = 0;
171
172	/* clear ack ratio state. */
173	hc->tx_rpseq    = 0;
174	hc->tx_rpdupack = -1;
175	ccid2_change_l_ack_ratio(sk, 1);
176
177	/* if we were blocked before, we may now send cwnd=1 packet */
178	if (sender_was_blocked)
179		dccp_tasklet_schedule(sk);
180	/* restart backed-off timer */
181	sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
182out:
183	bh_unlock_sock(sk);
184	sock_put(sk);
185}
186
187/*
188 *	Congestion window validation (RFC 2861).
189 */
190static bool ccid2_do_cwv = true;
191module_param(ccid2_do_cwv, bool, 0644);
192MODULE_PARM_DESC(ccid2_do_cwv, "Perform RFC2861 Congestion Window Validation");
193
194/**
195 * ccid2_update_used_window  -  Track how much of cwnd is actually used
196 * This is done in addition to CWV. The sender needs to have an idea of how many
197 * packets may be in flight, to set the local Sequence Window value accordingly
198 * (RFC 4340, 7.5.2). The CWV mechanism is exploited to keep track of the
199 * maximum-used window. We use an EWMA low-pass filter to filter out noise.
200 */
201static void ccid2_update_used_window(struct ccid2_hc_tx_sock *hc, u32 new_wnd)
202{
203	hc->tx_expected_wnd = (3 * hc->tx_expected_wnd + new_wnd) / 4;
204}
205
206/* This borrows the code of tcp_cwnd_application_limited() */
207static void ccid2_cwnd_application_limited(struct sock *sk, const u32 now)
208{
209	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
210	/* don't reduce cwnd below the initial window (IW) */
211	u32 init_win = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache),
212	    win_used = max(hc->tx_cwnd_used, init_win);
213
214	if (win_used < hc->tx_cwnd) {
215		hc->tx_ssthresh = max(hc->tx_ssthresh,
216				     (hc->tx_cwnd >> 1) + (hc->tx_cwnd >> 2));
217		hc->tx_cwnd = (hc->tx_cwnd + win_used) >> 1;
218	}
219	hc->tx_cwnd_used  = 0;
220	hc->tx_cwnd_stamp = now;
221
222	ccid2_check_l_ack_ratio(sk);
223}
224
225/* This borrows the code of tcp_cwnd_restart() */
226static void ccid2_cwnd_restart(struct sock *sk, const u32 now)
227{
228	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
229	u32 cwnd = hc->tx_cwnd, restart_cwnd,
230	    iwnd = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache);
231
232	hc->tx_ssthresh = max(hc->tx_ssthresh, (cwnd >> 1) + (cwnd >> 2));
233
234	/* don't reduce cwnd below the initial window (IW) */
235	restart_cwnd = min(cwnd, iwnd);
236	cwnd >>= (now - hc->tx_lsndtime) / hc->tx_rto;
237	hc->tx_cwnd = max(cwnd, restart_cwnd);
238
239	hc->tx_cwnd_stamp = now;
240	hc->tx_cwnd_used  = 0;
241
242	ccid2_check_l_ack_ratio(sk);
243}
244
245static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
246{
247	struct dccp_sock *dp = dccp_sk(sk);
248	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
249	const u32 now = ccid2_jiffies32;
250	struct ccid2_seq *next;
251
252	/* slow-start after idle periods (RFC 2581, RFC 2861) */
253	if (ccid2_do_cwv && !hc->tx_pipe &&
254	    (s32)(now - hc->tx_lsndtime) >= hc->tx_rto)
255		ccid2_cwnd_restart(sk, now);
256
257	hc->tx_lsndtime = now;
258	hc->tx_pipe    += 1;
259
260	/* see whether cwnd was fully used (RFC 2861), update expected window */
261	if (ccid2_cwnd_network_limited(hc)) {
262		ccid2_update_used_window(hc, hc->tx_cwnd);
263		hc->tx_cwnd_used  = 0;
264		hc->tx_cwnd_stamp = now;
265	} else {
266		if (hc->tx_pipe > hc->tx_cwnd_used)
267			hc->tx_cwnd_used = hc->tx_pipe;
268
269		ccid2_update_used_window(hc, hc->tx_cwnd_used);
270
271		if (ccid2_do_cwv && (s32)(now - hc->tx_cwnd_stamp) >= hc->tx_rto)
272			ccid2_cwnd_application_limited(sk, now);
273	}
274
275	hc->tx_seqh->ccid2s_seq   = dp->dccps_gss;
276	hc->tx_seqh->ccid2s_acked = 0;
277	hc->tx_seqh->ccid2s_sent  = now;
278
279	next = hc->tx_seqh->ccid2s_next;
280	/* check if we need to alloc more space */
281	if (next == hc->tx_seqt) {
282		if (ccid2_hc_tx_alloc_seq(hc)) {
283			DCCP_CRIT("packet history - out of memory!");
284			/* FIXME: find a more graceful way to bail out */
285			return;
286		}
287		next = hc->tx_seqh->ccid2s_next;
288		BUG_ON(next == hc->tx_seqt);
289	}
290	hc->tx_seqh = next;
291
292	ccid2_pr_debug("cwnd=%d pipe=%d\n", hc->tx_cwnd, hc->tx_pipe);
293
294	/*
295	 * FIXME: The code below is broken and the variables have been removed
296	 * from the socket struct. The `ackloss' variable was always set to 0,
297	 * and with arsent there are several problems:
298	 *  (i) it doesn't just count the number of Acks, but all sent packets;
299	 *  (ii) it is expressed in # of packets, not # of windows, so the
300	 *  comparison below uses the wrong formula: Appendix A of RFC 4341
301	 *  comes up with the number K = cwnd / (R^2 - R) of consecutive windows
302	 *  of data with no lost or marked Ack packets. If arsent were the # of
303	 *  consecutive Acks received without loss, then Ack Ratio needs to be
304	 *  decreased by 1 when
305	 *	      arsent >=  K * cwnd / R  =  cwnd^2 / (R^3 - R^2)
306	 *  where cwnd / R is the number of Acks received per window of data
307	 *  (cf. RFC 4341, App. A). The problems are that
308	 *  - arsent counts other packets as well;
309	 *  - the comparison uses a formula different from RFC 4341;
310	 *  - computing a cubic/quadratic equation each time is too complicated.
311	 *  Hence a different algorithm is needed.
312	 */
313#if 0
314	/* Ack Ratio.  Need to maintain a concept of how many windows we sent */
315	hc->tx_arsent++;
316	/* We had an ack loss in this window... */
317	if (hc->tx_ackloss) {
318		if (hc->tx_arsent >= hc->tx_cwnd) {
319			hc->tx_arsent  = 0;
320			hc->tx_ackloss = 0;
321		}
322	} else {
323		/* No acks lost up to now... */
324		/* decrease ack ratio if enough packets were sent */
325		if (dp->dccps_l_ack_ratio > 1) {
326			/* XXX don't calculate denominator each time */
327			int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
328				    dp->dccps_l_ack_ratio;
329
330			denom = hc->tx_cwnd * hc->tx_cwnd / denom;
331
332			if (hc->tx_arsent >= denom) {
333				ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
334				hc->tx_arsent = 0;
335			}
336		} else {
337			/* we can't increase ack ratio further [1] */
338			hc->tx_arsent = 0; /* or maybe set it to cwnd*/
339		}
340	}
341#endif
342
343	sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
344
345#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
346	do {
347		struct ccid2_seq *seqp = hc->tx_seqt;
348
349		while (seqp != hc->tx_seqh) {
350			ccid2_pr_debug("out seq=%llu acked=%d time=%u\n",
351				       (unsigned long long)seqp->ccid2s_seq,
352				       seqp->ccid2s_acked, seqp->ccid2s_sent);
353			seqp = seqp->ccid2s_next;
354		}
355	} while (0);
356	ccid2_pr_debug("=========\n");
357#endif
358}
359
360/**
361 * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
362 * This code is almost identical with TCP's tcp_rtt_estimator(), since
363 * - it has a higher sampling frequency (recommended by RFC 1323),
364 * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
365 * - it is simple (cf. more complex proposals such as Eifel timer or research
366 *   which suggests that the gain should be set according to window size),
367 * - in tests it was found to work well with CCID2 [gerrit].
368 */
369static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
370{
371	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
372	long m = mrtt ? : 1;
373
374	if (hc->tx_srtt == 0) {
375		/* First measurement m */
376		hc->tx_srtt = m << 3;
377		hc->tx_mdev = m << 1;
378
379		hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
380		hc->tx_rttvar   = hc->tx_mdev_max;
381
382		hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
383	} else {
384		/* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
385		m -= (hc->tx_srtt >> 3);
386		hc->tx_srtt += m;
387
388		/* Similarly, update scaled mdev with regard to |m| */
389		if (m < 0) {
390			m = -m;
391			m -= (hc->tx_mdev >> 2);
392			/*
393			 * This neutralises RTO increase when RTT < SRTT - mdev
394			 * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
395			 * in Linux TCP", USENIX 2002, pp. 49-62).
396			 */
397			if (m > 0)
398				m >>= 3;
399		} else {
400			m -= (hc->tx_mdev >> 2);
401		}
402		hc->tx_mdev += m;
403
404		if (hc->tx_mdev > hc->tx_mdev_max) {
405			hc->tx_mdev_max = hc->tx_mdev;
406			if (hc->tx_mdev_max > hc->tx_rttvar)
407				hc->tx_rttvar = hc->tx_mdev_max;
408		}
409
410		/*
411		 * Decay RTTVAR at most once per flight, exploiting that
412		 *  1) pipe <= cwnd <= Sequence_Window = W  (RFC 4340, 7.5.2)
413		 *  2) AWL = GSS-W+1 <= GAR <= GSS          (RFC 4340, 7.5.1)
414		 * GAR is a useful bound for FlightSize = pipe.
415		 * AWL is probably too low here, as it over-estimates pipe.
416		 */
417		if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
418			if (hc->tx_mdev_max < hc->tx_rttvar)
419				hc->tx_rttvar -= (hc->tx_rttvar -
420						  hc->tx_mdev_max) >> 2;
421			hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
422			hc->tx_mdev_max = tcp_rto_min(sk);
423		}
424	}
425
426	/*
427	 * Set RTO from SRTT and RTTVAR
428	 * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
429	 * This agrees with RFC 4341, 5:
430	 *	"Because DCCP does not retransmit data, DCCP does not require
431	 *	 TCP's recommended minimum timeout of one second".
432	 */
433	hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
434
435	if (hc->tx_rto > DCCP_RTO_MAX)
436		hc->tx_rto = DCCP_RTO_MAX;
437}
438
439static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
440			  unsigned int *maxincr)
441{
442	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
443	struct dccp_sock *dp = dccp_sk(sk);
444	int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
445
446	if (hc->tx_cwnd < dp->dccps_l_seq_win &&
447	    r_seq_used < dp->dccps_r_seq_win) {
448		if (hc->tx_cwnd < hc->tx_ssthresh) {
449			if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
450				hc->tx_cwnd += 1;
451				*maxincr    -= 1;
452				hc->tx_packets_acked = 0;
453			}
454		} else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
455			hc->tx_cwnd += 1;
456			hc->tx_packets_acked = 0;
457		}
458	}
459
460	/*
461	 * Adjust the local sequence window and the ack ratio to allow about
462	 * 5 times the number of packets in the network (RFC 4340 7.5.2)
463	 */
464	if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
465		ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio * 2);
466	else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
467		ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio / 2 ? : 1U);
468
469	if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
470		ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win * 2);
471	else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
472		ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win / 2);
473
474	/*
475	 * FIXME: RTT is sampled several times per acknowledgment (for each
476	 * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
477	 * This causes the RTT to be over-estimated, since the older entries
478	 * in the Ack Vector have earlier sending times.
479	 * The cleanest solution is to not use the ccid2s_sent field at all
480	 * and instead use DCCP timestamps: requires changes in other places.
481	 */
482	ccid2_rtt_estimator(sk, ccid2_jiffies32 - seqp->ccid2s_sent);
483}
484
485static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
486{
487	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
488
489	if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
490		ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
491		return;
492	}
493
494	hc->tx_last_cong = ccid2_jiffies32;
495
496	hc->tx_cwnd      = hc->tx_cwnd / 2 ? : 1U;
497	hc->tx_ssthresh  = max(hc->tx_cwnd, 2U);
498
499	ccid2_check_l_ack_ratio(sk);
500}
501
502static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
503				     u8 option, u8 *optval, u8 optlen)
504{
505	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
506
507	switch (option) {
508	case DCCPO_ACK_VECTOR_0:
509	case DCCPO_ACK_VECTOR_1:
510		return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
511					      option - DCCPO_ACK_VECTOR_0);
512	}
513	return 0;
514}
515
516static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
517{
518	struct dccp_sock *dp = dccp_sk(sk);
519	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
520	const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
521	struct dccp_ackvec_parsed *avp;
522	u64 ackno, seqno;
523	struct ccid2_seq *seqp;
524	int done = 0;
525	unsigned int maxincr = 0;
526
527	/* check reverse path congestion */
528	seqno = DCCP_SKB_CB(skb)->dccpd_seq;
529
530	/* XXX this whole "algorithm" is broken.  Need to fix it to keep track
531	 * of the seqnos of the dupacks so that rpseq and rpdupack are correct
532	 * -sorbo.
533	 */
534	/* need to bootstrap */
535	if (hc->tx_rpdupack == -1) {
536		hc->tx_rpdupack = 0;
537		hc->tx_rpseq    = seqno;
538	} else {
539		/* check if packet is consecutive */
540		if (dccp_delta_seqno(hc->tx_rpseq, seqno) == 1)
541			hc->tx_rpseq = seqno;
542		/* it's a later packet */
543		else if (after48(seqno, hc->tx_rpseq)) {
544			hc->tx_rpdupack++;
545
546			/* check if we got enough dupacks */
547			if (hc->tx_rpdupack >= NUMDUPACK) {
548				hc->tx_rpdupack = -1; /* XXX lame */
549				hc->tx_rpseq    = 0;
550#ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
551				/*
552				 * FIXME: Ack Congestion Control is broken; in
553				 * the current state instabilities occurred with
554				 * Ack Ratios greater than 1; causing hang-ups
555				 * and long RTO timeouts. This needs to be fixed
556				 * before opening up dynamic changes. -- gerrit
557				 */
558				ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
559#endif
560			}
561		}
562	}
563
564	/* check forward path congestion */
565	if (dccp_packet_without_ack(skb))
566		return;
567
568	/* still didn't send out new data packets */
569	if (hc->tx_seqh == hc->tx_seqt)
570		goto done;
571
572	ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
573	if (after48(ackno, hc->tx_high_ack))
574		hc->tx_high_ack = ackno;
575
576	seqp = hc->tx_seqt;
577	while (before48(seqp->ccid2s_seq, ackno)) {
578		seqp = seqp->ccid2s_next;
579		if (seqp == hc->tx_seqh) {
580			seqp = hc->tx_seqh->ccid2s_prev;
581			break;
582		}
583	}
584
585	/*
586	 * In slow-start, cwnd can increase up to a maximum of Ack Ratio/2
587	 * packets per acknowledgement. Rounding up avoids that cwnd is not
588	 * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
589	 */
590	if (hc->tx_cwnd < hc->tx_ssthresh)
591		maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
592
593	/* go through all ack vectors */
594	list_for_each_entry(avp, &hc->tx_av_chunks, node) {
595		/* go through this ack vector */
596		for (; avp->len--; avp->vec++) {
597			u64 ackno_end_rl = SUB48(ackno,
598						 dccp_ackvec_runlen(avp->vec));
599
600			ccid2_pr_debug("ackvec %llu |%u,%u|\n",
601				       (unsigned long long)ackno,
602				       dccp_ackvec_state(avp->vec) >> 6,
603				       dccp_ackvec_runlen(avp->vec));
604			/* if the seqno we are analyzing is larger than the
605			 * current ackno, then move towards the tail of our
606			 * seqnos.
607			 */
608			while (after48(seqp->ccid2s_seq, ackno)) {
609				if (seqp == hc->tx_seqt) {
610					done = 1;
611					break;
612				}
613				seqp = seqp->ccid2s_prev;
614			}
615			if (done)
616				break;
617
618			/* check all seqnos in the range of the vector
619			 * run length
620			 */
621			while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
622				const u8 state = dccp_ackvec_state(avp->vec);
623
624				/* new packet received or marked */
625				if (state != DCCPAV_NOT_RECEIVED &&
626				    !seqp->ccid2s_acked) {
627					if (state == DCCPAV_ECN_MARKED)
628						ccid2_congestion_event(sk,
629								       seqp);
630					else
631						ccid2_new_ack(sk, seqp,
632							      &maxincr);
633
634					seqp->ccid2s_acked = 1;
635					ccid2_pr_debug("Got ack for %llu\n",
636						       (unsigned long long)seqp->ccid2s_seq);
637					hc->tx_pipe--;
638				}
639				if (seqp == hc->tx_seqt) {
640					done = 1;
641					break;
642				}
643				seqp = seqp->ccid2s_prev;
644			}
645			if (done)
646				break;
647
648			ackno = SUB48(ackno_end_rl, 1);
649		}
650		if (done)
651			break;
652	}
653
654	/* The state about what is acked should be correct now
655	 * Check for NUMDUPACK
656	 */
657	seqp = hc->tx_seqt;
658	while (before48(seqp->ccid2s_seq, hc->tx_high_ack)) {
659		seqp = seqp->ccid2s_next;
660		if (seqp == hc->tx_seqh) {
661			seqp = hc->tx_seqh->ccid2s_prev;
662			break;
663		}
664	}
665	done = 0;
666	while (1) {
667		if (seqp->ccid2s_acked) {
668			done++;
669			if (done == NUMDUPACK)
670				break;
671		}
672		if (seqp == hc->tx_seqt)
673			break;
674		seqp = seqp->ccid2s_prev;
675	}
676
677	/* If there are at least 3 acknowledgements, anything unacknowledged
678	 * below the last sequence number is considered lost
679	 */
680	if (done == NUMDUPACK) {
681		struct ccid2_seq *last_acked = seqp;
682
683		/* check for lost packets */
684		while (1) {
685			if (!seqp->ccid2s_acked) {
686				ccid2_pr_debug("Packet lost: %llu\n",
687					       (unsigned long long)seqp->ccid2s_seq);
688				/* XXX need to traverse from tail -> head in
689				 * order to detect multiple congestion events in
690				 * one ack vector.
691				 */
692				ccid2_congestion_event(sk, seqp);
693				hc->tx_pipe--;
694			}
695			if (seqp == hc->tx_seqt)
696				break;
697			seqp = seqp->ccid2s_prev;
698		}
699
700		hc->tx_seqt = last_acked;
701	}
702
703	/* trim acked packets in tail */
704	while (hc->tx_seqt != hc->tx_seqh) {
705		if (!hc->tx_seqt->ccid2s_acked)
706			break;
707
708		hc->tx_seqt = hc->tx_seqt->ccid2s_next;
709	}
710
711	/* restart RTO timer if not all outstanding data has been acked */
712	if (hc->tx_pipe == 0)
713		sk_stop_timer(sk, &hc->tx_rtotimer);
714	else
715		sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
716done:
717	/* check if incoming Acks allow pending packets to be sent */
718	if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
719		dccp_tasklet_schedule(sk);
720	dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
721}
722
723static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
724{
725	struct ccid2_hc_tx_sock *hc = ccid_priv(ccid);
726	struct dccp_sock *dp = dccp_sk(sk);
727	u32 max_ratio;
728
729	/* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
730	hc->tx_ssthresh = ~0U;
731
732	/* Use larger initial windows (RFC 4341, section 5). */
733	hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
734	hc->tx_expected_wnd = hc->tx_cwnd;
735
736	/* Make sure that Ack Ratio is enabled and within bounds. */
737	max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
738	if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
739		dp->dccps_l_ack_ratio = max_ratio;
740
741	/* XXX init ~ to window size... */
742	if (ccid2_hc_tx_alloc_seq(hc))
743		return -ENOMEM;
744
745	hc->tx_rto	 = DCCP_TIMEOUT_INIT;
746	hc->tx_rpdupack  = -1;
747	hc->tx_last_cong = hc->tx_lsndtime = hc->tx_cwnd_stamp = ccid2_jiffies32;
748	hc->tx_cwnd_used = 0;
749	hc->sk		 = sk;
750	timer_setup(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire, 0);
751	INIT_LIST_HEAD(&hc->tx_av_chunks);
752	return 0;
753}
754
755static void ccid2_hc_tx_exit(struct sock *sk)
756{
757	struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
758	int i;
759
760	sk_stop_timer(sk, &hc->tx_rtotimer);
761
762	for (i = 0; i < hc->tx_seqbufc; i++)
763		kfree(hc->tx_seqbuf[i]);
764	hc->tx_seqbufc = 0;
765	dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
766}
767
768static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
769{
770	struct ccid2_hc_rx_sock *hc = ccid2_hc_rx_sk(sk);
771
772	if (!dccp_data_packet(skb))
773		return;
774
775	if (++hc->rx_num_data_pkts >= dccp_sk(sk)->dccps_r_ack_ratio) {
776		dccp_send_ack(sk);
777		hc->rx_num_data_pkts = 0;
778	}
779}
780
781struct ccid_operations ccid2_ops = {
782	.ccid_id		  = DCCPC_CCID2,
783	.ccid_name		  = "TCP-like",
784	.ccid_hc_tx_obj_size	  = sizeof(struct ccid2_hc_tx_sock),
785	.ccid_hc_tx_init	  = ccid2_hc_tx_init,
786	.ccid_hc_tx_exit	  = ccid2_hc_tx_exit,
787	.ccid_hc_tx_send_packet	  = ccid2_hc_tx_send_packet,
788	.ccid_hc_tx_packet_sent	  = ccid2_hc_tx_packet_sent,
789	.ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
790	.ccid_hc_tx_packet_recv	  = ccid2_hc_tx_packet_recv,
791	.ccid_hc_rx_obj_size	  = sizeof(struct ccid2_hc_rx_sock),
792	.ccid_hc_rx_packet_recv	  = ccid2_hc_rx_packet_recv,
793};
794
795#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
796module_param(ccid2_debug, bool, 0644);
797MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
798#endif