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Linux/net/dccp/output.c

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  1 /*
  2  *  net/dccp/output.c
  3  *
  4  *  An implementation of the DCCP protocol
  5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  6  *
  7  *      This program is free software; you can redistribute it and/or
  8  *      modify it under the terms of the GNU General Public License
  9  *      as published by the Free Software Foundation; either version
 10  *      2 of the License, or (at your option) any later version.
 11  */
 12 
 13 #include <linux/dccp.h>
 14 #include <linux/kernel.h>
 15 #include <linux/skbuff.h>
 16 #include <linux/slab.h>
 17 
 18 #include <net/inet_sock.h>
 19 #include <net/sock.h>
 20 
 21 #include "ackvec.h"
 22 #include "ccid.h"
 23 #include "dccp.h"
 24 
 25 static inline void dccp_event_ack_sent(struct sock *sk)
 26 {
 27         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 28 }
 29 
 30 /* enqueue @skb on sk_send_head for retransmission, return clone to send now */
 31 static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
 32 {
 33         skb_set_owner_w(skb, sk);
 34         WARN_ON(sk->sk_send_head);
 35         sk->sk_send_head = skb;
 36         return skb_clone(sk->sk_send_head, gfp_any());
 37 }
 38 
 39 /*
 40  * All SKB's seen here are completely headerless. It is our
 41  * job to build the DCCP header, and pass the packet down to
 42  * IP so it can do the same plus pass the packet off to the
 43  * device.
 44  */
 45 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
 46 {
 47         if (likely(skb != NULL)) {
 48                 struct inet_sock *inet = inet_sk(sk);
 49                 const struct inet_connection_sock *icsk = inet_csk(sk);
 50                 struct dccp_sock *dp = dccp_sk(sk);
 51                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 52                 struct dccp_hdr *dh;
 53                 /* XXX For now we're using only 48 bits sequence numbers */
 54                 const u32 dccp_header_size = sizeof(*dh) +
 55                                              sizeof(struct dccp_hdr_ext) +
 56                                           dccp_packet_hdr_len(dcb->dccpd_type);
 57                 int err, set_ack = 1;
 58                 u64 ackno = dp->dccps_gsr;
 59                 /*
 60                  * Increment GSS here already in case the option code needs it.
 61                  * Update GSS for real only if option processing below succeeds.
 62                  */
 63                 dcb->dccpd_seq = ADD48(dp->dccps_gss, 1);
 64 
 65                 switch (dcb->dccpd_type) {
 66                 case DCCP_PKT_DATA:
 67                         set_ack = 0;
 68                         /* fall through */
 69                 case DCCP_PKT_DATAACK:
 70                 case DCCP_PKT_RESET:
 71                         break;
 72 
 73                 case DCCP_PKT_REQUEST:
 74                         set_ack = 0;
 75                         /* Use ISS on the first (non-retransmitted) Request. */
 76                         if (icsk->icsk_retransmits == 0)
 77                                 dcb->dccpd_seq = dp->dccps_iss;
 78                         /* fall through */
 79 
 80                 case DCCP_PKT_SYNC:
 81                 case DCCP_PKT_SYNCACK:
 82                         ackno = dcb->dccpd_ack_seq;
 83                         /* fall through */
 84                 default:
 85                         /*
 86                          * Set owner/destructor: some skbs are allocated via
 87                          * alloc_skb (e.g. when retransmission may happen).
 88                          * Only Data, DataAck, and Reset packets should come
 89                          * through here with skb->sk set.
 90                          */
 91                         WARN_ON(skb->sk);
 92                         skb_set_owner_w(skb, sk);
 93                         break;
 94                 }
 95 
 96                 if (dccp_insert_options(sk, skb)) {
 97                         kfree_skb(skb);
 98                         return -EPROTO;
 99                 }
100 
101 
102                 /* Build DCCP header and checksum it. */
103                 dh = dccp_zeroed_hdr(skb, dccp_header_size);
104                 dh->dccph_type  = dcb->dccpd_type;
105                 dh->dccph_sport = inet->inet_sport;
106                 dh->dccph_dport = inet->inet_dport;
107                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
108                 dh->dccph_ccval = dcb->dccpd_ccval;
109                 dh->dccph_cscov = dp->dccps_pcslen;
110                 /* XXX For now we're using only 48 bits sequence numbers */
111                 dh->dccph_x     = 1;
112 
113                 dccp_update_gss(sk, dcb->dccpd_seq);
114                 dccp_hdr_set_seq(dh, dp->dccps_gss);
115                 if (set_ack)
116                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
117 
118                 switch (dcb->dccpd_type) {
119                 case DCCP_PKT_REQUEST:
120                         dccp_hdr_request(skb)->dccph_req_service =
121                                                         dp->dccps_service;
122                         /*
123                          * Limit Ack window to ISS <= P.ackno <= GSS, so that
124                          * only Responses to Requests we sent are considered.
125                          */
126                         dp->dccps_awl = dp->dccps_iss;
127                         break;
128                 case DCCP_PKT_RESET:
129                         dccp_hdr_reset(skb)->dccph_reset_code =
130                                                         dcb->dccpd_reset_code;
131                         break;
132                 }
133 
134                 icsk->icsk_af_ops->send_check(sk, skb);
135 
136                 if (set_ack)
137                         dccp_event_ack_sent(sk);
138 
139                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
140 
141                 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
142                 return net_xmit_eval(err);
143         }
144         return -ENOBUFS;
145 }
146 
147 /**
148  * dccp_determine_ccmps  -  Find out about CCID-specific packet-size limits
149  * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
150  * since the RX CCID is restricted to feedback packets (Acks), which are small
151  * in comparison with the data traffic. A value of 0 means "no current CCMPS".
152  */
153 static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
154 {
155         const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
156 
157         if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
158                 return 0;
159         return tx_ccid->ccid_ops->ccid_ccmps;
160 }
161 
162 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
163 {
164         struct inet_connection_sock *icsk = inet_csk(sk);
165         struct dccp_sock *dp = dccp_sk(sk);
166         u32 ccmps = dccp_determine_ccmps(dp);
167         u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
168 
169         /* Account for header lengths and IPv4/v6 option overhead */
170         cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
171                     sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
172 
173         /*
174          * Leave enough headroom for common DCCP header options.
175          * This only considers options which may appear on DCCP-Data packets, as
176          * per table 3 in RFC 4340, 5.8. When running out of space for other
177          * options (eg. Ack Vector which can take up to 255 bytes), it is better
178          * to schedule a separate Ack. Thus we leave headroom for the following:
179          *  - 1 byte for Slow Receiver (11.6)
180          *  - 6 bytes for Timestamp (13.1)
181          *  - 10 bytes for Timestamp Echo (13.3)
182          *  - 8 bytes for NDP count (7.7, when activated)
183          *  - 6 bytes for Data Checksum (9.3)
184          *  - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled)
185          */
186         cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 +
187                            (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4);
188 
189         /* And store cached results */
190         icsk->icsk_pmtu_cookie = pmtu;
191         dp->dccps_mss_cache = cur_mps;
192 
193         return cur_mps;
194 }
195 
196 EXPORT_SYMBOL_GPL(dccp_sync_mss);
197 
198 void dccp_write_space(struct sock *sk)
199 {
200         struct socket_wq *wq;
201 
202         rcu_read_lock();
203         wq = rcu_dereference(sk->sk_wq);
204         if (skwq_has_sleeper(wq))
205                 wake_up_interruptible(&wq->wait);
206         /* Should agree with poll, otherwise some programs break */
207         if (sock_writeable(sk))
208                 sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
209 
210         rcu_read_unlock();
211 }
212 
213 /**
214  * dccp_wait_for_ccid  -  Await CCID send permission
215  * @sk:    socket to wait for
216  * @delay: timeout in jiffies
217  *
218  * This is used by CCIDs which need to delay the send time in process context.
219  */
220 static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay)
221 {
222         DEFINE_WAIT(wait);
223         long remaining;
224 
225         prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
226         sk->sk_write_pending++;
227         release_sock(sk);
228 
229         remaining = schedule_timeout(delay);
230 
231         lock_sock(sk);
232         sk->sk_write_pending--;
233         finish_wait(sk_sleep(sk), &wait);
234 
235         if (signal_pending(current) || sk->sk_err)
236                 return -1;
237         return remaining;
238 }
239 
240 /**
241  * dccp_xmit_packet  -  Send data packet under control of CCID
242  * Transmits next-queued payload and informs CCID to account for the packet.
243  */
244 static void dccp_xmit_packet(struct sock *sk)
245 {
246         int err, len;
247         struct dccp_sock *dp = dccp_sk(sk);
248         struct sk_buff *skb = dccp_qpolicy_pop(sk);
249 
250         if (unlikely(skb == NULL))
251                 return;
252         len = skb->len;
253 
254         if (sk->sk_state == DCCP_PARTOPEN) {
255                 const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
256                 /*
257                  * See 8.1.5 - Handshake Completion.
258                  *
259                  * For robustness we resend Confirm options until the client has
260                  * entered OPEN. During the initial feature negotiation, the MPS
261                  * is smaller than usual, reduced by the Change/Confirm options.
262                  */
263                 if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
264                         DCCP_WARN("Payload too large (%d) for featneg.\n", len);
265                         dccp_send_ack(sk);
266                         dccp_feat_list_purge(&dp->dccps_featneg);
267                 }
268 
269                 inet_csk_schedule_ack(sk);
270                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
271                                               inet_csk(sk)->icsk_rto,
272                                               DCCP_RTO_MAX);
273                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
274         } else if (dccp_ack_pending(sk)) {
275                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
276         } else {
277                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;
278         }
279 
280         err = dccp_transmit_skb(sk, skb);
281         if (err)
282                 dccp_pr_debug("transmit_skb() returned err=%d\n", err);
283         /*
284          * Register this one as sent even if an error occurred. To the remote
285          * end a local packet drop is indistinguishable from network loss, i.e.
286          * any local drop will eventually be reported via receiver feedback.
287          */
288         ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
289 
290         /*
291          * If the CCID needs to transfer additional header options out-of-band
292          * (e.g. Ack Vectors or feature-negotiation options), it activates this
293          * flag to schedule a Sync. The Sync will automatically incorporate all
294          * currently pending header options, thus clearing the backlog.
295          */
296         if (dp->dccps_sync_scheduled)
297                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
298 }
299 
300 /**
301  * dccp_flush_write_queue  -  Drain queue at end of connection
302  * Since dccp_sendmsg queues packets without waiting for them to be sent, it may
303  * happen that the TX queue is not empty at the end of a connection. We give the
304  * HC-sender CCID a grace period of up to @time_budget jiffies. If this function
305  * returns with a non-empty write queue, it will be purged later.
306  */
307 void dccp_flush_write_queue(struct sock *sk, long *time_budget)
308 {
309         struct dccp_sock *dp = dccp_sk(sk);
310         struct sk_buff *skb;
311         long delay, rc;
312 
313         while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) {
314                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
315 
316                 switch (ccid_packet_dequeue_eval(rc)) {
317                 case CCID_PACKET_WILL_DEQUEUE_LATER:
318                         /*
319                          * If the CCID determines when to send, the next sending
320                          * time is unknown or the CCID may not even send again
321                          * (e.g. remote host crashes or lost Ack packets).
322                          */
323                         DCCP_WARN("CCID did not manage to send all packets\n");
324                         return;
325                 case CCID_PACKET_DELAY:
326                         delay = msecs_to_jiffies(rc);
327                         if (delay > *time_budget)
328                                 return;
329                         rc = dccp_wait_for_ccid(sk, delay);
330                         if (rc < 0)
331                                 return;
332                         *time_budget -= (delay - rc);
333                         /* check again if we can send now */
334                         break;
335                 case CCID_PACKET_SEND_AT_ONCE:
336                         dccp_xmit_packet(sk);
337                         break;
338                 case CCID_PACKET_ERR:
339                         skb_dequeue(&sk->sk_write_queue);
340                         kfree_skb(skb);
341                         dccp_pr_debug("packet discarded due to err=%ld\n", rc);
342                 }
343         }
344 }
345 
346 void dccp_write_xmit(struct sock *sk)
347 {
348         struct dccp_sock *dp = dccp_sk(sk);
349         struct sk_buff *skb;
350 
351         while ((skb = dccp_qpolicy_top(sk))) {
352                 int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
353 
354                 switch (ccid_packet_dequeue_eval(rc)) {
355                 case CCID_PACKET_WILL_DEQUEUE_LATER:
356                         return;
357                 case CCID_PACKET_DELAY:
358                         sk_reset_timer(sk, &dp->dccps_xmit_timer,
359                                        jiffies + msecs_to_jiffies(rc));
360                         return;
361                 case CCID_PACKET_SEND_AT_ONCE:
362                         dccp_xmit_packet(sk);
363                         break;
364                 case CCID_PACKET_ERR:
365                         dccp_qpolicy_drop(sk, skb);
366                         dccp_pr_debug("packet discarded due to err=%d\n", rc);
367                 }
368         }
369 }
370 
371 /**
372  * dccp_retransmit_skb  -  Retransmit Request, Close, or CloseReq packets
373  * There are only four retransmittable packet types in DCCP:
374  * - Request  in client-REQUEST  state (sec. 8.1.1),
375  * - CloseReq in server-CLOSEREQ state (sec. 8.3),
376  * - Close    in   node-CLOSING  state (sec. 8.3),
377  * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
378  * This function expects sk->sk_send_head to contain the original skb.
379  */
380 int dccp_retransmit_skb(struct sock *sk)
381 {
382         WARN_ON(sk->sk_send_head == NULL);
383 
384         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
385                 return -EHOSTUNREACH; /* Routing failure or similar. */
386 
387         /* this count is used to distinguish original and retransmitted skb */
388         inet_csk(sk)->icsk_retransmits++;
389 
390         return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
391 }
392 
393 struct sk_buff *dccp_make_response(const struct sock *sk, struct dst_entry *dst,
394                                    struct request_sock *req)
395 {
396         struct dccp_hdr *dh;
397         struct dccp_request_sock *dreq;
398         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
399                                      sizeof(struct dccp_hdr_ext) +
400                                      sizeof(struct dccp_hdr_response);
401         struct sk_buff *skb;
402 
403         /* sk is marked const to clearly express we dont hold socket lock.
404          * sock_wmalloc() will atomically change sk->sk_wmem_alloc,
405          * it is safe to promote sk to non const.
406          */
407         skb = sock_wmalloc((struct sock *)sk, MAX_DCCP_HEADER, 1,
408                            GFP_ATOMIC);
409         if (!skb)
410                 return NULL;
411 
412         skb_reserve(skb, MAX_DCCP_HEADER);
413 
414         skb_dst_set(skb, dst_clone(dst));
415 
416         dreq = dccp_rsk(req);
417         if (inet_rsk(req)->acked)       /* increase GSS upon retransmission */
418                 dccp_inc_seqno(&dreq->dreq_gss);
419         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
420         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_gss;
421 
422         /* Resolve feature dependencies resulting from choice of CCID */
423         if (dccp_feat_server_ccid_dependencies(dreq))
424                 goto response_failed;
425 
426         if (dccp_insert_options_rsk(dreq, skb))
427                 goto response_failed;
428 
429         /* Build and checksum header */
430         dh = dccp_zeroed_hdr(skb, dccp_header_size);
431 
432         dh->dccph_sport = htons(inet_rsk(req)->ir_num);
433         dh->dccph_dport = inet_rsk(req)->ir_rmt_port;
434         dh->dccph_doff  = (dccp_header_size +
435                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
436         dh->dccph_type  = DCCP_PKT_RESPONSE;
437         dh->dccph_x     = 1;
438         dccp_hdr_set_seq(dh, dreq->dreq_gss);
439         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr);
440         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
441 
442         dccp_csum_outgoing(skb);
443 
444         /* We use `acked' to remember that a Response was already sent. */
445         inet_rsk(req)->acked = 1;
446         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
447         return skb;
448 response_failed:
449         kfree_skb(skb);
450         return NULL;
451 }
452 
453 EXPORT_SYMBOL_GPL(dccp_make_response);
454 
455 /* answer offending packet in @rcv_skb with Reset from control socket @ctl */
456 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
457 {
458         struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
459         struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
460         const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
461                                        sizeof(struct dccp_hdr_ext) +
462                                        sizeof(struct dccp_hdr_reset);
463         struct dccp_hdr_reset *dhr;
464         struct sk_buff *skb;
465 
466         skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
467         if (skb == NULL)
468                 return NULL;
469 
470         skb_reserve(skb, sk->sk_prot->max_header);
471 
472         /* Swap the send and the receive. */
473         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
474         dh->dccph_type  = DCCP_PKT_RESET;
475         dh->dccph_sport = rxdh->dccph_dport;
476         dh->dccph_dport = rxdh->dccph_sport;
477         dh->dccph_doff  = dccp_hdr_reset_len / 4;
478         dh->dccph_x     = 1;
479 
480         dhr = dccp_hdr_reset(skb);
481         dhr->dccph_reset_code = dcb->dccpd_reset_code;
482 
483         switch (dcb->dccpd_reset_code) {
484         case DCCP_RESET_CODE_PACKET_ERROR:
485                 dhr->dccph_reset_data[0] = rxdh->dccph_type;
486                 break;
487         case DCCP_RESET_CODE_OPTION_ERROR:      /* fall through */
488         case DCCP_RESET_CODE_MANDATORY_ERROR:
489                 memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
490                 break;
491         }
492         /*
493          * From RFC 4340, 8.3.1:
494          *   If P.ackno exists, set R.seqno := P.ackno + 1.
495          *   Else set R.seqno := 0.
496          */
497         if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
498                 dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
499         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
500 
501         dccp_csum_outgoing(skb);
502         return skb;
503 }
504 
505 EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
506 
507 /* send Reset on established socket, to close or abort the connection */
508 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
509 {
510         struct sk_buff *skb;
511         /*
512          * FIXME: what if rebuild_header fails?
513          * Should we be doing a rebuild_header here?
514          */
515         int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
516 
517         if (err != 0)
518                 return err;
519 
520         skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
521         if (skb == NULL)
522                 return -ENOBUFS;
523 
524         /* Reserve space for headers and prepare control bits. */
525         skb_reserve(skb, sk->sk_prot->max_header);
526         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
527         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
528 
529         return dccp_transmit_skb(sk, skb);
530 }
531 
532 /*
533  * Do all connect socket setups that can be done AF independent.
534  */
535 int dccp_connect(struct sock *sk)
536 {
537         struct sk_buff *skb;
538         struct dccp_sock *dp = dccp_sk(sk);
539         struct dst_entry *dst = __sk_dst_get(sk);
540         struct inet_connection_sock *icsk = inet_csk(sk);
541 
542         sk->sk_err = 0;
543         sock_reset_flag(sk, SOCK_DONE);
544 
545         dccp_sync_mss(sk, dst_mtu(dst));
546 
547         /* do not connect if feature negotiation setup fails */
548         if (dccp_feat_finalise_settings(dccp_sk(sk)))
549                 return -EPROTO;
550 
551         /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
552         dp->dccps_gar = dp->dccps_iss;
553 
554         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
555         if (unlikely(skb == NULL))
556                 return -ENOBUFS;
557 
558         /* Reserve space for headers. */
559         skb_reserve(skb, sk->sk_prot->max_header);
560 
561         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
562 
563         dccp_transmit_skb(sk, dccp_skb_entail(sk, skb));
564         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
565 
566         /* Timer for repeating the REQUEST until an answer. */
567         icsk->icsk_retransmits = 0;
568         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
569                                   icsk->icsk_rto, DCCP_RTO_MAX);
570         return 0;
571 }
572 
573 EXPORT_SYMBOL_GPL(dccp_connect);
574 
575 void dccp_send_ack(struct sock *sk)
576 {
577         /* If we have been reset, we may not send again. */
578         if (sk->sk_state != DCCP_CLOSED) {
579                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
580                                                 GFP_ATOMIC);
581 
582                 if (skb == NULL) {
583                         inet_csk_schedule_ack(sk);
584                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
585                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
586                                                   TCP_DELACK_MAX,
587                                                   DCCP_RTO_MAX);
588                         return;
589                 }
590 
591                 /* Reserve space for headers */
592                 skb_reserve(skb, sk->sk_prot->max_header);
593                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
594                 dccp_transmit_skb(sk, skb);
595         }
596 }
597 
598 EXPORT_SYMBOL_GPL(dccp_send_ack);
599 
600 #if 0
601 /* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
602 void dccp_send_delayed_ack(struct sock *sk)
603 {
604         struct inet_connection_sock *icsk = inet_csk(sk);
605         /*
606          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
607          * with using 2s, and active senders also piggyback the ACK into a
608          * DATAACK packet, so this is really for quiescent senders.
609          */
610         unsigned long timeout = jiffies + 2 * HZ;
611 
612         /* Use new timeout only if there wasn't a older one earlier. */
613         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
614                 /* If delack timer was blocked or is about to expire,
615                  * send ACK now.
616                  *
617                  * FIXME: check the "about to expire" part
618                  */
619                 if (icsk->icsk_ack.blocked) {
620                         dccp_send_ack(sk);
621                         return;
622                 }
623 
624                 if (!time_before(timeout, icsk->icsk_ack.timeout))
625                         timeout = icsk->icsk_ack.timeout;
626         }
627         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
628         icsk->icsk_ack.timeout = timeout;
629         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
630 }
631 #endif
632 
633 void dccp_send_sync(struct sock *sk, const u64 ackno,
634                     const enum dccp_pkt_type pkt_type)
635 {
636         /*
637          * We are not putting this on the write queue, so
638          * dccp_transmit_skb() will set the ownership to this
639          * sock.
640          */
641         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
642 
643         if (skb == NULL) {
644                 /* FIXME: how to make sure the sync is sent? */
645                 DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
646                 return;
647         }
648 
649         /* Reserve space for headers and prepare control bits. */
650         skb_reserve(skb, sk->sk_prot->max_header);
651         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
652         DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
653 
654         /*
655          * Clear the flag in case the Sync was scheduled for out-of-band data,
656          * such as carrying a long Ack Vector.
657          */
658         dccp_sk(sk)->dccps_sync_scheduled = 0;
659 
660         dccp_transmit_skb(sk, skb);
661 }
662 
663 EXPORT_SYMBOL_GPL(dccp_send_sync);
664 
665 /*
666  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
667  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
668  * any circumstances.
669  */
670 void dccp_send_close(struct sock *sk, const int active)
671 {
672         struct dccp_sock *dp = dccp_sk(sk);
673         struct sk_buff *skb;
674         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
675 
676         skb = alloc_skb(sk->sk_prot->max_header, prio);
677         if (skb == NULL)
678                 return;
679 
680         /* Reserve space for headers and prepare control bits. */
681         skb_reserve(skb, sk->sk_prot->max_header);
682         if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait)
683                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ;
684         else
685                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE;
686 
687         if (active) {
688                 skb = dccp_skb_entail(sk, skb);
689                 /*
690                  * Retransmission timer for active-close: RFC 4340, 8.3 requires
691                  * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
692                  * state can be left. The initial timeout is 2 RTTs.
693                  * Since RTT measurement is done by the CCIDs, there is no easy
694                  * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
695                  * is too low (200ms); we use a high value to avoid unnecessary
696                  * retransmissions when the link RTT is > 0.2 seconds.
697                  * FIXME: Let main module sample RTTs and use that instead.
698                  */
699                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
700                                           DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
701         }
702         dccp_transmit_skb(sk, skb);
703 }
704 

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