1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * net/dccp/output.c
4 *
5 * An implementation of the DCCP protocol
6 * Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7 */
8
9 #include <linux/dccp.h>
10 #include <linux/kernel.h>
11 #include <linux/skbuff.h>
12 #include <linux/slab.h>
13 #include <linux/sched/signal.h>
14
15 #include <net/inet_sock.h>
16 #include <net/sock.h>
17
18 #include "ackvec.h"
19 #include "ccid.h"
20 #include "dccp.h"
21
dccp_event_ack_sent(struct sock * sk)22 static inline void dccp_event_ack_sent(struct sock *sk)
23 {
24 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
25 }
26
27 /* enqueue @skb on sk_send_head for retransmission, return clone to send now */
dccp_skb_entail(struct sock * sk,struct sk_buff * skb)28 static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
29 {
30 skb_set_owner_w(skb, sk);
31 WARN_ON(sk->sk_send_head);
32 sk->sk_send_head = skb;
33 return skb_clone(sk->sk_send_head, gfp_any());
34 }
35
36 /*
37 * All SKB's seen here are completely headerless. It is our
38 * job to build the DCCP header, and pass the packet down to
39 * IP so it can do the same plus pass the packet off to the
40 * device.
41 */
dccp_transmit_skb(struct sock * sk,struct sk_buff * skb)42 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
43 {
44 if (likely(skb != NULL)) {
45 struct inet_sock *inet = inet_sk(sk);
46 const struct inet_connection_sock *icsk = inet_csk(sk);
47 struct dccp_sock *dp = dccp_sk(sk);
48 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
49 struct dccp_hdr *dh;
50 /* XXX For now we're using only 48 bits sequence numbers */
51 const u32 dccp_header_size = sizeof(*dh) +
52 sizeof(struct dccp_hdr_ext) +
53 dccp_packet_hdr_len(dcb->dccpd_type);
54 int err, set_ack = 1;
55 u64 ackno = dp->dccps_gsr;
56 /*
57 * Increment GSS here already in case the option code needs it.
58 * Update GSS for real only if option processing below succeeds.
59 */
60 dcb->dccpd_seq = ADD48(dp->dccps_gss, 1);
61
62 switch (dcb->dccpd_type) {
63 case DCCP_PKT_DATA:
64 set_ack = 0;
65 /* fall through */
66 case DCCP_PKT_DATAACK:
67 case DCCP_PKT_RESET:
68 break;
69
70 case DCCP_PKT_REQUEST:
71 set_ack = 0;
72 /* Use ISS on the first (non-retransmitted) Request. */
73 if (icsk->icsk_retransmits == 0)
74 dcb->dccpd_seq = dp->dccps_iss;
75 /* fall through */
76
77 case DCCP_PKT_SYNC:
78 case DCCP_PKT_SYNCACK:
79 ackno = dcb->dccpd_ack_seq;
80 /* fall through */
81 default:
82 /*
83 * Set owner/destructor: some skbs are allocated via
84 * alloc_skb (e.g. when retransmission may happen).
85 * Only Data, DataAck, and Reset packets should come
86 * through here with skb->sk set.
87 */
88 WARN_ON(skb->sk);
89 skb_set_owner_w(skb, sk);
90 break;
91 }
92
93 if (dccp_insert_options(sk, skb)) {
94 kfree_skb(skb);
95 return -EPROTO;
96 }
97
98
99 /* Build DCCP header and checksum it. */
100 dh = dccp_zeroed_hdr(skb, dccp_header_size);
101 dh->dccph_type = dcb->dccpd_type;
102 dh->dccph_sport = inet->inet_sport;
103 dh->dccph_dport = inet->inet_dport;
104 dh->dccph_doff = (dccp_header_size + dcb->dccpd_opt_len) / 4;
105 dh->dccph_ccval = dcb->dccpd_ccval;
106 dh->dccph_cscov = dp->dccps_pcslen;
107 /* XXX For now we're using only 48 bits sequence numbers */
108 dh->dccph_x = 1;
109
110 dccp_update_gss(sk, dcb->dccpd_seq);
111 dccp_hdr_set_seq(dh, dp->dccps_gss);
112 if (set_ack)
113 dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
114
115 switch (dcb->dccpd_type) {
116 case DCCP_PKT_REQUEST:
117 dccp_hdr_request(skb)->dccph_req_service =
118 dp->dccps_service;
119 /*
120 * Limit Ack window to ISS <= P.ackno <= GSS, so that
121 * only Responses to Requests we sent are considered.
122 */
123 dp->dccps_awl = dp->dccps_iss;
124 break;
125 case DCCP_PKT_RESET:
126 dccp_hdr_reset(skb)->dccph_reset_code =
127 dcb->dccpd_reset_code;
128 break;
129 }
130
131 icsk->icsk_af_ops->send_check(sk, skb);
132
133 if (set_ack)
134 dccp_event_ack_sent(sk);
135
136 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
137
138 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
139 return net_xmit_eval(err);
140 }
141 return -ENOBUFS;
142 }
143
144 /**
145 * dccp_determine_ccmps - Find out about CCID-specific packet-size limits
146 * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
147 * since the RX CCID is restricted to feedback packets (Acks), which are small
148 * in comparison with the data traffic. A value of 0 means "no current CCMPS".
149 */
dccp_determine_ccmps(const struct dccp_sock * dp)150 static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
151 {
152 const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
153
154 if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
155 return 0;
156 return tx_ccid->ccid_ops->ccid_ccmps;
157 }
158
dccp_sync_mss(struct sock * sk,u32 pmtu)159 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
160 {
161 struct inet_connection_sock *icsk = inet_csk(sk);
162 struct dccp_sock *dp = dccp_sk(sk);
163 u32 ccmps = dccp_determine_ccmps(dp);
164 u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
165
166 /* Account for header lengths and IPv4/v6 option overhead */
167 cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
168 sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
169
170 /*
171 * Leave enough headroom for common DCCP header options.
172 * This only considers options which may appear on DCCP-Data packets, as
173 * per table 3 in RFC 4340, 5.8. When running out of space for other
174 * options (eg. Ack Vector which can take up to 255 bytes), it is better
175 * to schedule a separate Ack. Thus we leave headroom for the following:
176 * - 1 byte for Slow Receiver (11.6)
177 * - 6 bytes for Timestamp (13.1)
178 * - 10 bytes for Timestamp Echo (13.3)
179 * - 8 bytes for NDP count (7.7, when activated)
180 * - 6 bytes for Data Checksum (9.3)
181 * - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled)
182 */
183 cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 +
184 (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4);
185
186 /* And store cached results */
187 icsk->icsk_pmtu_cookie = pmtu;
188 dp->dccps_mss_cache = cur_mps;
189
190 return cur_mps;
191 }
192
193 EXPORT_SYMBOL_GPL(dccp_sync_mss);
194
dccp_write_space(struct sock * sk)195 void dccp_write_space(struct sock *sk)
196 {
197 struct socket_wq *wq;
198
199 rcu_read_lock();
200 wq = rcu_dereference(sk->sk_wq);
201 if (skwq_has_sleeper(wq))
202 wake_up_interruptible(&wq->wait);
203 /* Should agree with poll, otherwise some programs break */
204 if (sock_writeable(sk))
205 sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
206
207 rcu_read_unlock();
208 }
209
210 /**
211 * dccp_wait_for_ccid - Await CCID send permission
212 * @sk: socket to wait for
213 * @delay: timeout in jiffies
214 *
215 * This is used by CCIDs which need to delay the send time in process context.
216 */
dccp_wait_for_ccid(struct sock * sk,unsigned long delay)217 static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay)
218 {
219 DEFINE_WAIT(wait);
220 long remaining;
221
222 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
223 sk->sk_write_pending++;
224 release_sock(sk);
225
226 remaining = schedule_timeout(delay);
227
228 lock_sock(sk);
229 sk->sk_write_pending--;
230 finish_wait(sk_sleep(sk), &wait);
231
232 if (signal_pending(current) || sk->sk_err)
233 return -1;
234 return remaining;
235 }
236
237 /**
238 * dccp_xmit_packet - Send data packet under control of CCID
239 * Transmits next-queued payload and informs CCID to account for the packet.
240 */
dccp_xmit_packet(struct sock * sk)241 static void dccp_xmit_packet(struct sock *sk)
242 {
243 int err, len;
244 struct dccp_sock *dp = dccp_sk(sk);
245 struct sk_buff *skb = dccp_qpolicy_pop(sk);
246
247 if (unlikely(skb == NULL))
248 return;
249 len = skb->len;
250
251 if (sk->sk_state == DCCP_PARTOPEN) {
252 const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
253 /*
254 * See 8.1.5 - Handshake Completion.
255 *
256 * For robustness we resend Confirm options until the client has
257 * entered OPEN. During the initial feature negotiation, the MPS
258 * is smaller than usual, reduced by the Change/Confirm options.
259 */
260 if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
261 DCCP_WARN("Payload too large (%d) for featneg.\n", len);
262 dccp_send_ack(sk);
263 dccp_feat_list_purge(&dp->dccps_featneg);
264 }
265
266 inet_csk_schedule_ack(sk);
267 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
268 inet_csk(sk)->icsk_rto,
269 DCCP_RTO_MAX);
270 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
271 } else if (dccp_ack_pending(sk)) {
272 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
273 } else {
274 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;
275 }
276
277 err = dccp_transmit_skb(sk, skb);
278 if (err)
279 dccp_pr_debug("transmit_skb() returned err=%d\n", err);
280 /*
281 * Register this one as sent even if an error occurred. To the remote
282 * end a local packet drop is indistinguishable from network loss, i.e.
283 * any local drop will eventually be reported via receiver feedback.
284 */
285 ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
286
287 /*
288 * If the CCID needs to transfer additional header options out-of-band
289 * (e.g. Ack Vectors or feature-negotiation options), it activates this
290 * flag to schedule a Sync. The Sync will automatically incorporate all
291 * currently pending header options, thus clearing the backlog.
292 */
293 if (dp->dccps_sync_scheduled)
294 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
295 }
296
297 /**
298 * dccp_flush_write_queue - Drain queue at end of connection
299 * Since dccp_sendmsg queues packets without waiting for them to be sent, it may
300 * happen that the TX queue is not empty at the end of a connection. We give the
301 * HC-sender CCID a grace period of up to @time_budget jiffies. If this function
302 * returns with a non-empty write queue, it will be purged later.
303 */
dccp_flush_write_queue(struct sock * sk,long * time_budget)304 void dccp_flush_write_queue(struct sock *sk, long *time_budget)
305 {
306 struct dccp_sock *dp = dccp_sk(sk);
307 struct sk_buff *skb;
308 long delay, rc;
309
310 while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) {
311 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
312
313 switch (ccid_packet_dequeue_eval(rc)) {
314 case CCID_PACKET_WILL_DEQUEUE_LATER:
315 /*
316 * If the CCID determines when to send, the next sending
317 * time is unknown or the CCID may not even send again
318 * (e.g. remote host crashes or lost Ack packets).
319 */
320 DCCP_WARN("CCID did not manage to send all packets\n");
321 return;
322 case CCID_PACKET_DELAY:
323 delay = msecs_to_jiffies(rc);
324 if (delay > *time_budget)
325 return;
326 rc = dccp_wait_for_ccid(sk, delay);
327 if (rc < 0)
328 return;
329 *time_budget -= (delay - rc);
330 /* check again if we can send now */
331 break;
332 case CCID_PACKET_SEND_AT_ONCE:
333 dccp_xmit_packet(sk);
334 break;
335 case CCID_PACKET_ERR:
336 skb_dequeue(&sk->sk_write_queue);
337 kfree_skb(skb);
338 dccp_pr_debug("packet discarded due to err=%ld\n", rc);
339 }
340 }
341 }
342
dccp_write_xmit(struct sock * sk)343 void dccp_write_xmit(struct sock *sk)
344 {
345 struct dccp_sock *dp = dccp_sk(sk);
346 struct sk_buff *skb;
347
348 while ((skb = dccp_qpolicy_top(sk))) {
349 int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
350
351 switch (ccid_packet_dequeue_eval(rc)) {
352 case CCID_PACKET_WILL_DEQUEUE_LATER:
353 return;
354 case CCID_PACKET_DELAY:
355 sk_reset_timer(sk, &dp->dccps_xmit_timer,
356 jiffies + msecs_to_jiffies(rc));
357 return;
358 case CCID_PACKET_SEND_AT_ONCE:
359 dccp_xmit_packet(sk);
360 break;
361 case CCID_PACKET_ERR:
362 dccp_qpolicy_drop(sk, skb);
363 dccp_pr_debug("packet discarded due to err=%d\n", rc);
364 }
365 }
366 }
367
368 /**
369 * dccp_retransmit_skb - Retransmit Request, Close, or CloseReq packets
370 * There are only four retransmittable packet types in DCCP:
371 * - Request in client-REQUEST state (sec. 8.1.1),
372 * - CloseReq in server-CLOSEREQ state (sec. 8.3),
373 * - Close in node-CLOSING state (sec. 8.3),
374 * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
375 * This function expects sk->sk_send_head to contain the original skb.
376 */
dccp_retransmit_skb(struct sock * sk)377 int dccp_retransmit_skb(struct sock *sk)
378 {
379 WARN_ON(sk->sk_send_head == NULL);
380
381 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
382 return -EHOSTUNREACH; /* Routing failure or similar. */
383
384 /* this count is used to distinguish original and retransmitted skb */
385 inet_csk(sk)->icsk_retransmits++;
386
387 return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
388 }
389
dccp_make_response(const struct sock * sk,struct dst_entry * dst,struct request_sock * req)390 struct sk_buff *dccp_make_response(const struct sock *sk, struct dst_entry *dst,
391 struct request_sock *req)
392 {
393 struct dccp_hdr *dh;
394 struct dccp_request_sock *dreq;
395 const u32 dccp_header_size = sizeof(struct dccp_hdr) +
396 sizeof(struct dccp_hdr_ext) +
397 sizeof(struct dccp_hdr_response);
398 struct sk_buff *skb;
399
400 /* sk is marked const to clearly express we dont hold socket lock.
401 * sock_wmalloc() will atomically change sk->sk_wmem_alloc,
402 * it is safe to promote sk to non const.
403 */
404 skb = sock_wmalloc((struct sock *)sk, MAX_DCCP_HEADER, 1,
405 GFP_ATOMIC);
406 if (!skb)
407 return NULL;
408
409 skb_reserve(skb, MAX_DCCP_HEADER);
410
411 skb_dst_set(skb, dst_clone(dst));
412
413 dreq = dccp_rsk(req);
414 if (inet_rsk(req)->acked) /* increase GSS upon retransmission */
415 dccp_inc_seqno(&dreq->dreq_gss);
416 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
417 DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_gss;
418
419 /* Resolve feature dependencies resulting from choice of CCID */
420 if (dccp_feat_server_ccid_dependencies(dreq))
421 goto response_failed;
422
423 if (dccp_insert_options_rsk(dreq, skb))
424 goto response_failed;
425
426 /* Build and checksum header */
427 dh = dccp_zeroed_hdr(skb, dccp_header_size);
428
429 dh->dccph_sport = htons(inet_rsk(req)->ir_num);
430 dh->dccph_dport = inet_rsk(req)->ir_rmt_port;
431 dh->dccph_doff = (dccp_header_size +
432 DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
433 dh->dccph_type = DCCP_PKT_RESPONSE;
434 dh->dccph_x = 1;
435 dccp_hdr_set_seq(dh, dreq->dreq_gss);
436 dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr);
437 dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
438
439 dccp_csum_outgoing(skb);
440
441 /* We use `acked' to remember that a Response was already sent. */
442 inet_rsk(req)->acked = 1;
443 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
444 return skb;
445 response_failed:
446 kfree_skb(skb);
447 return NULL;
448 }
449
450 EXPORT_SYMBOL_GPL(dccp_make_response);
451
452 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */
dccp_ctl_make_reset(struct sock * sk,struct sk_buff * rcv_skb)453 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
454 {
455 struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
456 struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
457 const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
458 sizeof(struct dccp_hdr_ext) +
459 sizeof(struct dccp_hdr_reset);
460 struct dccp_hdr_reset *dhr;
461 struct sk_buff *skb;
462
463 skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
464 if (skb == NULL)
465 return NULL;
466
467 skb_reserve(skb, sk->sk_prot->max_header);
468
469 /* Swap the send and the receive. */
470 dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
471 dh->dccph_type = DCCP_PKT_RESET;
472 dh->dccph_sport = rxdh->dccph_dport;
473 dh->dccph_dport = rxdh->dccph_sport;
474 dh->dccph_doff = dccp_hdr_reset_len / 4;
475 dh->dccph_x = 1;
476
477 dhr = dccp_hdr_reset(skb);
478 dhr->dccph_reset_code = dcb->dccpd_reset_code;
479
480 switch (dcb->dccpd_reset_code) {
481 case DCCP_RESET_CODE_PACKET_ERROR:
482 dhr->dccph_reset_data[0] = rxdh->dccph_type;
483 break;
484 case DCCP_RESET_CODE_OPTION_ERROR: /* fall through */
485 case DCCP_RESET_CODE_MANDATORY_ERROR:
486 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
487 break;
488 }
489 /*
490 * From RFC 4340, 8.3.1:
491 * If P.ackno exists, set R.seqno := P.ackno + 1.
492 * Else set R.seqno := 0.
493 */
494 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
495 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
496 dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
497
498 dccp_csum_outgoing(skb);
499 return skb;
500 }
501
502 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
503
504 /* send Reset on established socket, to close or abort the connection */
dccp_send_reset(struct sock * sk,enum dccp_reset_codes code)505 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
506 {
507 struct sk_buff *skb;
508 /*
509 * FIXME: what if rebuild_header fails?
510 * Should we be doing a rebuild_header here?
511 */
512 int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
513
514 if (err != 0)
515 return err;
516
517 skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
518 if (skb == NULL)
519 return -ENOBUFS;
520
521 /* Reserve space for headers and prepare control bits. */
522 skb_reserve(skb, sk->sk_prot->max_header);
523 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESET;
524 DCCP_SKB_CB(skb)->dccpd_reset_code = code;
525
526 return dccp_transmit_skb(sk, skb);
527 }
528
529 /*
530 * Do all connect socket setups that can be done AF independent.
531 */
dccp_connect(struct sock * sk)532 int dccp_connect(struct sock *sk)
533 {
534 struct sk_buff *skb;
535 struct dccp_sock *dp = dccp_sk(sk);
536 struct dst_entry *dst = __sk_dst_get(sk);
537 struct inet_connection_sock *icsk = inet_csk(sk);
538
539 sk->sk_err = 0;
540 sock_reset_flag(sk, SOCK_DONE);
541
542 dccp_sync_mss(sk, dst_mtu(dst));
543
544 /* do not connect if feature negotiation setup fails */
545 if (dccp_feat_finalise_settings(dccp_sk(sk)))
546 return -EPROTO;
547
548 /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
549 dp->dccps_gar = dp->dccps_iss;
550
551 skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
552 if (unlikely(skb == NULL))
553 return -ENOBUFS;
554
555 /* Reserve space for headers. */
556 skb_reserve(skb, sk->sk_prot->max_header);
557
558 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
559
560 dccp_transmit_skb(sk, dccp_skb_entail(sk, skb));
561 DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
562
563 /* Timer for repeating the REQUEST until an answer. */
564 icsk->icsk_retransmits = 0;
565 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
566 icsk->icsk_rto, DCCP_RTO_MAX);
567 return 0;
568 }
569
570 EXPORT_SYMBOL_GPL(dccp_connect);
571
dccp_send_ack(struct sock * sk)572 void dccp_send_ack(struct sock *sk)
573 {
574 /* If we have been reset, we may not send again. */
575 if (sk->sk_state != DCCP_CLOSED) {
576 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
577 GFP_ATOMIC);
578
579 if (skb == NULL) {
580 inet_csk_schedule_ack(sk);
581 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
582 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
583 TCP_DELACK_MAX,
584 DCCP_RTO_MAX);
585 return;
586 }
587
588 /* Reserve space for headers */
589 skb_reserve(skb, sk->sk_prot->max_header);
590 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
591 dccp_transmit_skb(sk, skb);
592 }
593 }
594
595 EXPORT_SYMBOL_GPL(dccp_send_ack);
596
597 #if 0
598 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
599 void dccp_send_delayed_ack(struct sock *sk)
600 {
601 struct inet_connection_sock *icsk = inet_csk(sk);
602 /*
603 * FIXME: tune this timer. elapsed time fixes the skew, so no problem
604 * with using 2s, and active senders also piggyback the ACK into a
605 * DATAACK packet, so this is really for quiescent senders.
606 */
607 unsigned long timeout = jiffies + 2 * HZ;
608
609 /* Use new timeout only if there wasn't a older one earlier. */
610 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
611 /* If delack timer was blocked or is about to expire,
612 * send ACK now.
613 *
614 * FIXME: check the "about to expire" part
615 */
616 if (icsk->icsk_ack.blocked) {
617 dccp_send_ack(sk);
618 return;
619 }
620
621 if (!time_before(timeout, icsk->icsk_ack.timeout))
622 timeout = icsk->icsk_ack.timeout;
623 }
624 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
625 icsk->icsk_ack.timeout = timeout;
626 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
627 }
628 #endif
629
dccp_send_sync(struct sock * sk,const u64 ackno,const enum dccp_pkt_type pkt_type)630 void dccp_send_sync(struct sock *sk, const u64 ackno,
631 const enum dccp_pkt_type pkt_type)
632 {
633 /*
634 * We are not putting this on the write queue, so
635 * dccp_transmit_skb() will set the ownership to this
636 * sock.
637 */
638 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
639
640 if (skb == NULL) {
641 /* FIXME: how to make sure the sync is sent? */
642 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
643 return;
644 }
645
646 /* Reserve space for headers and prepare control bits. */
647 skb_reserve(skb, sk->sk_prot->max_header);
648 DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
649 DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
650
651 /*
652 * Clear the flag in case the Sync was scheduled for out-of-band data,
653 * such as carrying a long Ack Vector.
654 */
655 dccp_sk(sk)->dccps_sync_scheduled = 0;
656
657 dccp_transmit_skb(sk, skb);
658 }
659
660 EXPORT_SYMBOL_GPL(dccp_send_sync);
661
662 /*
663 * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
664 * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
665 * any circumstances.
666 */
dccp_send_close(struct sock * sk,const int active)667 void dccp_send_close(struct sock *sk, const int active)
668 {
669 struct dccp_sock *dp = dccp_sk(sk);
670 struct sk_buff *skb;
671 const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
672
673 skb = alloc_skb(sk->sk_prot->max_header, prio);
674 if (skb == NULL)
675 return;
676
677 /* Reserve space for headers and prepare control bits. */
678 skb_reserve(skb, sk->sk_prot->max_header);
679 if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait)
680 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ;
681 else
682 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE;
683
684 if (active) {
685 skb = dccp_skb_entail(sk, skb);
686 /*
687 * Retransmission timer for active-close: RFC 4340, 8.3 requires
688 * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
689 * state can be left. The initial timeout is 2 RTTs.
690 * Since RTT measurement is done by the CCIDs, there is no easy
691 * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
692 * is too low (200ms); we use a high value to avoid unnecessary
693 * retransmissions when the link RTT is > 0.2 seconds.
694 * FIXME: Let main module sample RTTs and use that instead.
695 */
696 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
697 DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
698 }
699 dccp_transmit_skb(sk, skb);
700 }
701