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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
17 #include <net/inet_sock.h>
18 #include <net/sock.h>
19
20 #include "ackvec.h"
21 #include "ccid.h"
22 #include "dccp.h"
23
24 static inline void dccp_event_ack_sent(struct sock *sk)
25 {
26         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
27 }
28
29 static void dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
30 {
31         skb_set_owner_w(skb, sk);
32         WARN_ON(sk->sk_send_head);
33         sk->sk_send_head = skb;
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  */
42 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
43 {
44         if (likely(skb != NULL)) {
45                 const 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                 dccp_inc_seqno(&dp->dccps_gss);
58
59                 switch (dcb->dccpd_type) {
60                 case DCCP_PKT_DATA:
61                         set_ack = 0;
62                         /* fall through */
63                 case DCCP_PKT_DATAACK:
64                         break;
65
66                 case DCCP_PKT_REQUEST:
67                         set_ack = 0;
68                         /* fall through */
69
70                 case DCCP_PKT_SYNC:
71                 case DCCP_PKT_SYNCACK:
72                         ackno = dcb->dccpd_seq;
73                         /* fall through */
74                 default:
75                         /*
76                          * Only data packets should come through with skb->sk
77                          * set.
78                          */
79                         WARN_ON(skb->sk);
80                         skb_set_owner_w(skb, sk);
81                         break;
82                 }
83
84                 dcb->dccpd_seq = dp->dccps_gss;
85
86                 if (dccp_insert_options(sk, skb)) {
87                         kfree_skb(skb);
88                         return -EPROTO;
89                 }
90                 
91                 skb->h.raw = skb_push(skb, dccp_header_size);
92                 dh = dccp_hdr(skb);
93
94                 /* Build DCCP header and checksum it. */
95                 memset(dh, 0, dccp_header_size);
96                 dh->dccph_type  = dcb->dccpd_type;
97                 dh->dccph_sport = inet->sport;
98                 dh->dccph_dport = inet->dport;
99                 dh->dccph_doff  = (dccp_header_size + dcb->dccpd_opt_len) / 4;
100                 dh->dccph_ccval = dcb->dccpd_ccval;
101                 /* XXX For now we're using only 48 bits sequence numbers */
102                 dh->dccph_x     = 1;
103
104                 dp->dccps_awh = dp->dccps_gss;
105                 dccp_hdr_set_seq(dh, dp->dccps_gss);
106                 if (set_ack)
107                         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
108
109                 switch (dcb->dccpd_type) {
110                 case DCCP_PKT_REQUEST:
111                         dccp_hdr_request(skb)->dccph_req_service =
112                                                         dp->dccps_service;
113                         break;
114                 case DCCP_PKT_RESET:
115                         dccp_hdr_reset(skb)->dccph_reset_code =
116                                                         dcb->dccpd_reset_code;
117                         break;
118                 }
119
120                 icsk->icsk_af_ops->send_check(sk, skb->len, skb);
121
122                 if (set_ack)
123                         dccp_event_ack_sent(sk);
124
125                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
126
127                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
128                 err = icsk->icsk_af_ops->queue_xmit(skb, 0);
129                 if (err <= 0)
130                         return err;
131
132                 /* NET_XMIT_CN is special. It does not guarantee,
133                  * that this packet is lost. It tells that device
134                  * is about to start to drop packets or already
135                  * drops some packets of the same priority and
136                  * invokes us to send less aggressively.
137                  */
138                 return err == NET_XMIT_CN ? 0 : err;
139         }
140         return -ENOBUFS;
141 }
142
143 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
144 {
145         struct inet_connection_sock *icsk = inet_csk(sk);
146         struct dccp_sock *dp = dccp_sk(sk);
147         int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
148                        sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));
149
150         /* Now subtract optional transport overhead */
151         mss_now -= icsk->icsk_ext_hdr_len;
152
153         /*
154          * FIXME: this should come from the CCID infrastructure, where, say,
155          * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
156          * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
157          * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
158          * make it a multiple of 4
159          */
160
161         mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
162
163         /* And store cached results */
164         icsk->icsk_pmtu_cookie = pmtu;
165         dp->dccps_mss_cache = mss_now;
166
167         return mss_now;
168 }
169
170 EXPORT_SYMBOL_GPL(dccp_sync_mss);
171
172 void dccp_write_space(struct sock *sk)
173 {
174         read_lock(&sk->sk_callback_lock);
175
176         if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
177                 wake_up_interruptible(sk->sk_sleep);
178         /* Should agree with poll, otherwise some programs break */
179         if (sock_writeable(sk))
180                 sk_wake_async(sk, 2, POLL_OUT);
181
182         read_unlock(&sk->sk_callback_lock);
183 }
184
185 /**
186  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
187  * @sk: socket to wait for
188  * @timeo: for how long
189  */
190 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb,
191                               long *timeo)
192 {
193         struct dccp_sock *dp = dccp_sk(sk);
194         DEFINE_WAIT(wait);
195         long delay;
196         int rc;
197
198         while (1) {
199                 prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
200
201                 if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
202                         goto do_error;
203                 if (!*timeo)
204                         goto do_nonblock;
205                 if (signal_pending(current))
206                         goto do_interrupted;
207
208                 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
209                                             skb->len);
210                 if (rc <= 0)
211                         break;
212                 delay = msecs_to_jiffies(rc);
213                 if (delay > *timeo || delay < 0)
214                         goto do_nonblock;
215
216                 sk->sk_write_pending++;
217                 release_sock(sk);
218                 *timeo -= schedule_timeout(delay);
219                 lock_sock(sk);
220                 sk->sk_write_pending--;
221         }
222 out:
223         finish_wait(sk->sk_sleep, &wait);
224         return rc;
225
226 do_error:
227         rc = -EPIPE;
228         goto out;
229 do_nonblock:
230         rc = -EAGAIN;
231         goto out;
232 do_interrupted:
233         rc = sock_intr_errno(*timeo);
234         goto out;
235 }
236
237 int dccp_write_xmit(struct sock *sk, struct sk_buff *skb, long *timeo)
238 {
239         const struct dccp_sock *dp = dccp_sk(sk);
240         int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb,
241                                          skb->len);
242
243         if (err > 0)
244                 err = dccp_wait_for_ccid(sk, skb, timeo);
245
246         if (err == 0) {
247                 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
248                 const int len = skb->len;
249
250                 if (sk->sk_state == DCCP_PARTOPEN) {
251                         /* See 8.1.5.  Handshake Completion */
252                         inet_csk_schedule_ack(sk);
253                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
254                                                   inet_csk(sk)->icsk_rto,
255                                                   DCCP_RTO_MAX);
256                         dcb->dccpd_type = DCCP_PKT_DATAACK;
257                 } else if (dccp_ack_pending(sk))
258                         dcb->dccpd_type = DCCP_PKT_DATAACK;
259                 else
260                         dcb->dccpd_type = DCCP_PKT_DATA;
261
262                 err = dccp_transmit_skb(sk, skb);
263                 ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
264         } else
265                 kfree_skb(skb);
266
267         return err;
268 }
269
270 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
271 {
272         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
273                 return -EHOSTUNREACH; /* Routing failure or similar. */
274
275         return dccp_transmit_skb(sk, (skb_cloned(skb) ?
276                                       pskb_copy(skb, GFP_ATOMIC):
277                                       skb_clone(skb, GFP_ATOMIC)));
278 }
279
280 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
281                                    struct request_sock *req)
282 {
283         struct dccp_hdr *dh;
284         struct dccp_request_sock *dreq;
285         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
286                                      sizeof(struct dccp_hdr_ext) +
287                                      sizeof(struct dccp_hdr_response);
288         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
289                                            GFP_ATOMIC);
290         if (skb == NULL)
291                 return NULL;
292
293         /* Reserve space for headers. */
294         skb_reserve(skb, sk->sk_prot->max_header);
295
296         skb->dst = dst_clone(dst);
297         skb->csum = 0;
298
299         dreq = dccp_rsk(req);
300         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
301         DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
302
303         if (dccp_insert_options(sk, skb)) {
304                 kfree_skb(skb);
305                 return NULL;
306         }
307
308         skb->h.raw = skb_push(skb, dccp_header_size);
309
310         dh = dccp_hdr(skb);
311         memset(dh, 0, dccp_header_size);
312
313         dh->dccph_sport = inet_sk(sk)->sport;
314         dh->dccph_dport = inet_rsk(req)->rmt_port;
315         dh->dccph_doff  = (dccp_header_size +
316                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
317         dh->dccph_type  = DCCP_PKT_RESPONSE;
318         dh->dccph_x     = 1;
319         dccp_hdr_set_seq(dh, dreq->dreq_iss);
320         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
321         dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
322
323         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
324         return skb;
325 }
326
327 EXPORT_SYMBOL_GPL(dccp_make_response);
328
329 static struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
330                                        const enum dccp_reset_codes code)
331                                    
332 {
333         struct dccp_hdr *dh;
334         struct dccp_sock *dp = dccp_sk(sk);
335         const u32 dccp_header_size = sizeof(struct dccp_hdr) +
336                                      sizeof(struct dccp_hdr_ext) +
337                                      sizeof(struct dccp_hdr_reset);
338         struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
339                                            GFP_ATOMIC);
340         if (skb == NULL)
341                 return NULL;
342
343         /* Reserve space for headers. */
344         skb_reserve(skb, sk->sk_prot->max_header);
345
346         skb->dst = dst_clone(dst);
347         skb->csum = 0;
348
349         dccp_inc_seqno(&dp->dccps_gss);
350
351         DCCP_SKB_CB(skb)->dccpd_reset_code = code;
352         DCCP_SKB_CB(skb)->dccpd_type       = DCCP_PKT_RESET;
353         DCCP_SKB_CB(skb)->dccpd_seq        = dp->dccps_gss;
354
355         if (dccp_insert_options(sk, skb)) {
356                 kfree_skb(skb);
357                 return NULL;
358         }
359
360         skb->h.raw = skb_push(skb, dccp_header_size);
361
362         dh = dccp_hdr(skb);
363         memset(dh, 0, dccp_header_size);
364
365         dh->dccph_sport = inet_sk(sk)->sport;
366         dh->dccph_dport = inet_sk(sk)->dport;
367         dh->dccph_doff  = (dccp_header_size +
368                            DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
369         dh->dccph_type  = DCCP_PKT_RESET;
370         dh->dccph_x     = 1;
371         dccp_hdr_set_seq(dh, dp->dccps_gss);
372         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);
373
374         dccp_hdr_reset(skb)->dccph_reset_code = code;
375         inet_csk(sk)->icsk_af_ops->send_check(sk, skb->len, skb);
376
377         DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
378         return skb;
379 }
380
381 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
382 {
383         /*
384          * FIXME: what if rebuild_header fails?
385          * Should we be doing a rebuild_header here?
386          */
387         int err = inet_sk_rebuild_header(sk);
388
389         if (err == 0) {
390                 struct sk_buff *skb = dccp_make_reset(sk, sk->sk_dst_cache,
391                                                       code);
392                 if (skb != NULL) {
393                         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
394                         err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, 0);
395                         if (err == NET_XMIT_CN)
396                                 err = 0;
397                 }
398         }
399
400         return err;
401 }
402
403 /*
404  * Do all connect socket setups that can be done AF independent.
405  */
406 static inline void dccp_connect_init(struct sock *sk)
407 {
408         struct dccp_sock *dp = dccp_sk(sk);
409         struct dst_entry *dst = __sk_dst_get(sk);
410         struct inet_connection_sock *icsk = inet_csk(sk);
411
412         sk->sk_err = 0;
413         sock_reset_flag(sk, SOCK_DONE);
414         
415         dccp_sync_mss(sk, dst_mtu(dst));
416
417         dccp_update_gss(sk, dp->dccps_iss);
418         /*
419          * SWL and AWL are initially adjusted so that they are not less than
420          * the initial Sequence Numbers received and sent, respectively:
421          *      SWL := max(GSR + 1 - floor(W/4), ISR),
422          *      AWL := max(GSS - W' + 1, ISS).
423          * These adjustments MUST be applied only at the beginning of the
424          * connection.
425          */
426         dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));
427
428         icsk->icsk_retransmits = 0;
429 }
430
431 int dccp_connect(struct sock *sk)
432 {
433         struct sk_buff *skb;
434         struct inet_connection_sock *icsk = inet_csk(sk);
435
436         dccp_connect_init(sk);
437
438         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
439         if (unlikely(skb == NULL))
440                 return -ENOBUFS;
441
442         /* Reserve space for headers. */
443         skb_reserve(skb, sk->sk_prot->max_header);
444
445         DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
446         skb->csum = 0;
447
448         dccp_skb_entail(sk, skb);
449         dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
450         DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
451
452         /* Timer for repeating the REQUEST until an answer. */
453         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
454                                   icsk->icsk_rto, DCCP_RTO_MAX);
455         return 0;
456 }
457
458 EXPORT_SYMBOL_GPL(dccp_connect);
459
460 void dccp_send_ack(struct sock *sk)
461 {
462         /* If we have been reset, we may not send again. */
463         if (sk->sk_state != DCCP_CLOSED) {
464                 struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
465                                                 GFP_ATOMIC);
466
467                 if (skb == NULL) {
468                         inet_csk_schedule_ack(sk);
469                         inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
470                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
471                                                   TCP_DELACK_MAX,
472                                                   DCCP_RTO_MAX);
473                         return;
474                 }
475
476                 /* Reserve space for headers */
477                 skb_reserve(skb, sk->sk_prot->max_header);
478                 skb->csum = 0;
479                 DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
480                 dccp_transmit_skb(sk, skb);
481         }
482 }
483
484 EXPORT_SYMBOL_GPL(dccp_send_ack);
485
486 void dccp_send_delayed_ack(struct sock *sk)
487 {
488         struct inet_connection_sock *icsk = inet_csk(sk);
489         /*
490          * FIXME: tune this timer. elapsed time fixes the skew, so no problem
491          * with using 2s, and active senders also piggyback the ACK into a
492          * DATAACK packet, so this is really for quiescent senders.
493          */
494         unsigned long timeout = jiffies + 2 * HZ;
495
496         /* Use new timeout only if there wasn't a older one earlier. */
497         if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
498                 /* If delack timer was blocked or is about to expire,
499                  * send ACK now.
500                  *
501                  * FIXME: check the "about to expire" part
502                  */
503                 if (icsk->icsk_ack.blocked) {
504                         dccp_send_ack(sk);
505                         return;
506                 }
507
508                 if (!time_before(timeout, icsk->icsk_ack.timeout))
509                         timeout = icsk->icsk_ack.timeout;
510         }
511         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
512         icsk->icsk_ack.timeout = timeout;
513         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
514 }
515
516 void dccp_send_sync(struct sock *sk, const u64 seq,
517                     const enum dccp_pkt_type pkt_type)
518 {
519         /*
520          * We are not putting this on the write queue, so
521          * dccp_transmit_skb() will set the ownership to this
522          * sock.
523          */
524         struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
525
526         if (skb == NULL)
527                 /* FIXME: how to make sure the sync is sent? */
528                 return;
529
530         /* Reserve space for headers and prepare control bits. */
531         skb_reserve(skb, sk->sk_prot->max_header);
532         skb->csum = 0;
533         DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
534         DCCP_SKB_CB(skb)->dccpd_seq = seq;
535
536         dccp_transmit_skb(sk, skb);
537 }
538
539 EXPORT_SYMBOL_GPL(dccp_send_sync);
540
541 /*
542  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
543  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
544  * any circumstances.
545  */
546 void dccp_send_close(struct sock *sk, const int active)
547 {
548         struct dccp_sock *dp = dccp_sk(sk);
549         struct sk_buff *skb;
550         const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
551
552         skb = alloc_skb(sk->sk_prot->max_header, prio);
553         if (skb == NULL)
554                 return;
555
556         /* Reserve space for headers and prepare control bits. */
557         skb_reserve(skb, sk->sk_prot->max_header);
558         skb->csum = 0;
559         DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
560                                         DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;
561
562         if (active) {
563                 dccp_skb_entail(sk, skb);
564                 dccp_transmit_skb(sk, skb_clone(skb, prio));
565         } else
566                 dccp_transmit_skb(sk, skb);
567 }