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1/* SCTP kernel implementation
2 * (C) Copyright IBM Corp. 2001, 2004
3 * Copyright (c) 1999-2000 Cisco, Inc.
4 * Copyright (c) 1999-2001 Motorola, Inc.
5 *
6 * This file is part of the SCTP kernel implementation
7 *
8 * These functions handle output processing.
9 *
10 * This SCTP implementation is free software;
11 * you can redistribute it and/or modify it under the terms of
12 * the GNU General Public License as published by
13 * the Free Software Foundation; either version 2, or (at your option)
14 * any later version.
15 *
16 * This SCTP implementation is distributed in the hope that it
17 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
18 * ************************
19 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
20 * See the GNU General Public License for more details.
21 *
22 * You should have received a copy of the GNU General Public License
23 * along with GNU CC; see the file COPYING. If not, see
24 * <http://www.gnu.org/licenses/>.
25 *
26 * Please send any bug reports or fixes you make to the
27 * email address(es):
28 * lksctp developers <linux-sctp@vger.kernel.org>
29 *
30 * Written or modified by:
31 * La Monte H.P. Yarroll <piggy@acm.org>
32 * Karl Knutson <karl@athena.chicago.il.us>
33 * Jon Grimm <jgrimm@austin.ibm.com>
34 * Sridhar Samudrala <sri@us.ibm.com>
35 */
36
37#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
38
39#include <linux/types.h>
40#include <linux/kernel.h>
41#include <linux/wait.h>
42#include <linux/time.h>
43#include <linux/ip.h>
44#include <linux/ipv6.h>
45#include <linux/init.h>
46#include <linux/slab.h>
47#include <net/inet_ecn.h>
48#include <net/ip.h>
49#include <net/icmp.h>
50#include <net/net_namespace.h>
51
52#include <linux/socket.h> /* for sa_family_t */
53#include <net/sock.h>
54
55#include <net/sctp/sctp.h>
56#include <net/sctp/sm.h>
57#include <net/sctp/checksum.h>
58
59/* Forward declarations for private helpers. */
60static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
61 struct sctp_chunk *chunk);
62static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
63 struct sctp_chunk *chunk);
64static void sctp_packet_append_data(struct sctp_packet *packet,
65 struct sctp_chunk *chunk);
66static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
67 struct sctp_chunk *chunk,
68 u16 chunk_len);
69
70static void sctp_packet_reset(struct sctp_packet *packet)
71{
72 packet->size = packet->overhead;
73 packet->has_cookie_echo = 0;
74 packet->has_sack = 0;
75 packet->has_data = 0;
76 packet->has_auth = 0;
77 packet->ipfragok = 0;
78 packet->auth = NULL;
79}
80
81/* Config a packet.
82 * This appears to be a followup set of initializations.
83 */
84struct sctp_packet *sctp_packet_config(struct sctp_packet *packet,
85 __u32 vtag, int ecn_capable)
86{
87 struct sctp_chunk *chunk = NULL;
88
89 pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
90
91 packet->vtag = vtag;
92
93 if (ecn_capable && sctp_packet_empty(packet)) {
94 chunk = sctp_get_ecne_prepend(packet->transport->asoc);
95
96 /* If there a is a prepend chunk stick it on the list before
97 * any other chunks get appended.
98 */
99 if (chunk)
100 sctp_packet_append_chunk(packet, chunk);
101 }
102
103 return packet;
104}
105
106/* Initialize the packet structure. */
107struct sctp_packet *sctp_packet_init(struct sctp_packet *packet,
108 struct sctp_transport *transport,
109 __u16 sport, __u16 dport)
110{
111 struct sctp_association *asoc = transport->asoc;
112 size_t overhead;
113
114 pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
115
116 packet->transport = transport;
117 packet->source_port = sport;
118 packet->destination_port = dport;
119 INIT_LIST_HEAD(&packet->chunk_list);
120 if (asoc) {
121 struct sctp_sock *sp = sctp_sk(asoc->base.sk);
122 overhead = sp->pf->af->net_header_len;
123 } else {
124 overhead = sizeof(struct ipv6hdr);
125 }
126 overhead += sizeof(struct sctphdr);
127 packet->overhead = overhead;
128 sctp_packet_reset(packet);
129 packet->vtag = 0;
130
131 return packet;
132}
133
134/* Free a packet. */
135void sctp_packet_free(struct sctp_packet *packet)
136{
137 struct sctp_chunk *chunk, *tmp;
138
139 pr_debug("%s: packet:%p\n", __func__, packet);
140
141 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
142 list_del_init(&chunk->list);
143 sctp_chunk_free(chunk);
144 }
145}
146
147/* This routine tries to append the chunk to the offered packet. If adding
148 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
149 * is not present in the packet, it transmits the input packet.
150 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
151 * as it can fit in the packet, but any more data that does not fit in this
152 * packet can be sent only after receiving the COOKIE_ACK.
153 */
154sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet,
155 struct sctp_chunk *chunk,
156 int one_packet, gfp_t gfp)
157{
158 sctp_xmit_t retval;
159 int error = 0;
160
161 pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
162
163 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
164 case SCTP_XMIT_PMTU_FULL:
165 if (!packet->has_cookie_echo) {
166 error = sctp_packet_transmit(packet, gfp);
167 if (error < 0)
168 chunk->skb->sk->sk_err = -error;
169
170 /* If we have an empty packet, then we can NOT ever
171 * return PMTU_FULL.
172 */
173 if (!one_packet)
174 retval = sctp_packet_append_chunk(packet,
175 chunk);
176 }
177 break;
178
179 case SCTP_XMIT_RWND_FULL:
180 case SCTP_XMIT_OK:
181 case SCTP_XMIT_DELAY:
182 break;
183 }
184
185 return retval;
186}
187
188/* Try to bundle an auth chunk into the packet. */
189static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
190 struct sctp_chunk *chunk)
191{
192 struct sctp_association *asoc = pkt->transport->asoc;
193 struct sctp_chunk *auth;
194 sctp_xmit_t retval = SCTP_XMIT_OK;
195
196 /* if we don't have an association, we can't do authentication */
197 if (!asoc)
198 return retval;
199
200 /* See if this is an auth chunk we are bundling or if
201 * auth is already bundled.
202 */
203 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
204 return retval;
205
206 /* if the peer did not request this chunk to be authenticated,
207 * don't do it
208 */
209 if (!chunk->auth)
210 return retval;
211
212 auth = sctp_make_auth(asoc);
213 if (!auth)
214 return retval;
215
216 retval = __sctp_packet_append_chunk(pkt, auth);
217
218 if (retval != SCTP_XMIT_OK)
219 sctp_chunk_free(auth);
220
221 return retval;
222}
223
224/* Try to bundle a SACK with the packet. */
225static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
226 struct sctp_chunk *chunk)
227{
228 sctp_xmit_t retval = SCTP_XMIT_OK;
229
230 /* If sending DATA and haven't aleady bundled a SACK, try to
231 * bundle one in to the packet.
232 */
233 if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
234 !pkt->has_cookie_echo) {
235 struct sctp_association *asoc;
236 struct timer_list *timer;
237 asoc = pkt->transport->asoc;
238 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
239
240 /* If the SACK timer is running, we have a pending SACK */
241 if (timer_pending(timer)) {
242 struct sctp_chunk *sack;
243
244 if (pkt->transport->sack_generation !=
245 pkt->transport->asoc->peer.sack_generation)
246 return retval;
247
248 asoc->a_rwnd = asoc->rwnd;
249 sack = sctp_make_sack(asoc);
250 if (sack) {
251 retval = __sctp_packet_append_chunk(pkt, sack);
252 if (retval != SCTP_XMIT_OK) {
253 sctp_chunk_free(sack);
254 goto out;
255 }
256 asoc->peer.sack_needed = 0;
257 if (del_timer(timer))
258 sctp_association_put(asoc);
259 }
260 }
261 }
262out:
263 return retval;
264}
265
266
267/* Append a chunk to the offered packet reporting back any inability to do
268 * so.
269 */
270static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
271 struct sctp_chunk *chunk)
272{
273 sctp_xmit_t retval = SCTP_XMIT_OK;
274 __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
275
276 /* Check to see if this chunk will fit into the packet */
277 retval = sctp_packet_will_fit(packet, chunk, chunk_len);
278 if (retval != SCTP_XMIT_OK)
279 goto finish;
280
281 /* We believe that this chunk is OK to add to the packet */
282 switch (chunk->chunk_hdr->type) {
283 case SCTP_CID_DATA:
284 /* Account for the data being in the packet */
285 sctp_packet_append_data(packet, chunk);
286 /* Disallow SACK bundling after DATA. */
287 packet->has_sack = 1;
288 /* Disallow AUTH bundling after DATA */
289 packet->has_auth = 1;
290 /* Let it be knows that packet has DATA in it */
291 packet->has_data = 1;
292 /* timestamp the chunk for rtx purposes */
293 chunk->sent_at = jiffies;
294 break;
295 case SCTP_CID_COOKIE_ECHO:
296 packet->has_cookie_echo = 1;
297 break;
298
299 case SCTP_CID_SACK:
300 packet->has_sack = 1;
301 if (chunk->asoc)
302 chunk->asoc->stats.osacks++;
303 break;
304
305 case SCTP_CID_AUTH:
306 packet->has_auth = 1;
307 packet->auth = chunk;
308 break;
309 }
310
311 /* It is OK to send this chunk. */
312 list_add_tail(&chunk->list, &packet->chunk_list);
313 packet->size += chunk_len;
314 chunk->transport = packet->transport;
315finish:
316 return retval;
317}
318
319/* Append a chunk to the offered packet reporting back any inability to do
320 * so.
321 */
322sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
323 struct sctp_chunk *chunk)
324{
325 sctp_xmit_t retval = SCTP_XMIT_OK;
326
327 pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
328
329 /* Data chunks are special. Before seeing what else we can
330 * bundle into this packet, check to see if we are allowed to
331 * send this DATA.
332 */
333 if (sctp_chunk_is_data(chunk)) {
334 retval = sctp_packet_can_append_data(packet, chunk);
335 if (retval != SCTP_XMIT_OK)
336 goto finish;
337 }
338
339 /* Try to bundle AUTH chunk */
340 retval = sctp_packet_bundle_auth(packet, chunk);
341 if (retval != SCTP_XMIT_OK)
342 goto finish;
343
344 /* Try to bundle SACK chunk */
345 retval = sctp_packet_bundle_sack(packet, chunk);
346 if (retval != SCTP_XMIT_OK)
347 goto finish;
348
349 retval = __sctp_packet_append_chunk(packet, chunk);
350
351finish:
352 return retval;
353}
354
355static void sctp_packet_release_owner(struct sk_buff *skb)
356{
357 sk_free(skb->sk);
358}
359
360static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
361{
362 skb_orphan(skb);
363 skb->sk = sk;
364 skb->destructor = sctp_packet_release_owner;
365
366 /*
367 * The data chunks have already been accounted for in sctp_sendmsg(),
368 * therefore only reserve a single byte to keep socket around until
369 * the packet has been transmitted.
370 */
371 atomic_inc(&sk->sk_wmem_alloc);
372}
373
374/* All packets are sent to the network through this function from
375 * sctp_outq_tail().
376 *
377 * The return value is a normal kernel error return value.
378 */
379int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
380{
381 struct sctp_transport *tp = packet->transport;
382 struct sctp_association *asoc = tp->asoc;
383 struct sctphdr *sh;
384 struct sk_buff *nskb;
385 struct sctp_chunk *chunk, *tmp;
386 struct sock *sk;
387 int err = 0;
388 int padding; /* How much padding do we need? */
389 __u8 has_data = 0;
390 struct dst_entry *dst;
391 unsigned char *auth = NULL; /* pointer to auth in skb data */
392
393 pr_debug("%s: packet:%p\n", __func__, packet);
394
395 /* Do NOT generate a chunkless packet. */
396 if (list_empty(&packet->chunk_list))
397 return err;
398
399 /* Set up convenience variables... */
400 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
401 sk = chunk->skb->sk;
402
403 /* Allocate the new skb. */
404 nskb = alloc_skb(packet->size + MAX_HEADER, gfp);
405 if (!nskb)
406 goto nomem;
407
408 /* Make sure the outbound skb has enough header room reserved. */
409 skb_reserve(nskb, packet->overhead + MAX_HEADER);
410
411 /* Set the owning socket so that we know where to get the
412 * destination IP address.
413 */
414 sctp_packet_set_owner_w(nskb, sk);
415
416 if (!sctp_transport_dst_check(tp)) {
417 sctp_transport_route(tp, NULL, sctp_sk(sk));
418 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
419 sctp_assoc_sync_pmtu(sk, asoc);
420 }
421 }
422 dst = dst_clone(tp->dst);
423 if (!dst)
424 goto no_route;
425 skb_dst_set(nskb, dst);
426
427 /* Build the SCTP header. */
428 sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));
429 skb_reset_transport_header(nskb);
430 sh->source = htons(packet->source_port);
431 sh->dest = htons(packet->destination_port);
432
433 /* From 6.8 Adler-32 Checksum Calculation:
434 * After the packet is constructed (containing the SCTP common
435 * header and one or more control or DATA chunks), the
436 * transmitter shall:
437 *
438 * 1) Fill in the proper Verification Tag in the SCTP common
439 * header and initialize the checksum field to 0's.
440 */
441 sh->vtag = htonl(packet->vtag);
442 sh->checksum = 0;
443
444 /**
445 * 6.10 Bundling
446 *
447 * An endpoint bundles chunks by simply including multiple
448 * chunks in one outbound SCTP packet. ...
449 */
450
451 /**
452 * 3.2 Chunk Field Descriptions
453 *
454 * The total length of a chunk (including Type, Length and
455 * Value fields) MUST be a multiple of 4 bytes. If the length
456 * of the chunk is not a multiple of 4 bytes, the sender MUST
457 * pad the chunk with all zero bytes and this padding is not
458 * included in the chunk length field. The sender should
459 * never pad with more than 3 bytes.
460 *
461 * [This whole comment explains WORD_ROUND() below.]
462 */
463
464 pr_debug("***sctp_transmit_packet***\n");
465
466 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
467 list_del_init(&chunk->list);
468 if (sctp_chunk_is_data(chunk)) {
469 /* 6.3.1 C4) When data is in flight and when allowed
470 * by rule C5, a new RTT measurement MUST be made each
471 * round trip. Furthermore, new RTT measurements
472 * SHOULD be made no more than once per round-trip
473 * for a given destination transport address.
474 */
475
476 if (!chunk->resent && !tp->rto_pending) {
477 chunk->rtt_in_progress = 1;
478 tp->rto_pending = 1;
479 }
480
481 has_data = 1;
482 }
483
484 padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len;
485 if (padding)
486 memset(skb_put(chunk->skb, padding), 0, padding);
487
488 /* if this is the auth chunk that we are adding,
489 * store pointer where it will be added and put
490 * the auth into the packet.
491 */
492 if (chunk == packet->auth)
493 auth = skb_tail_pointer(nskb);
494
495 memcpy(skb_put(nskb, chunk->skb->len),
496 chunk->skb->data, chunk->skb->len);
497
498 pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, "
499 "rtt_in_progress:%d\n", chunk,
500 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
501 chunk->has_tsn ? "TSN" : "No TSN",
502 chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
503 ntohs(chunk->chunk_hdr->length), chunk->skb->len,
504 chunk->rtt_in_progress);
505
506 /*
507 * If this is a control chunk, this is our last
508 * reference. Free data chunks after they've been
509 * acknowledged or have failed.
510 */
511 if (!sctp_chunk_is_data(chunk))
512 sctp_chunk_free(chunk);
513 }
514
515 /* SCTP-AUTH, Section 6.2
516 * The sender MUST calculate the MAC as described in RFC2104 [2]
517 * using the hash function H as described by the MAC Identifier and
518 * the shared association key K based on the endpoint pair shared key
519 * described by the shared key identifier. The 'data' used for the
520 * computation of the AUTH-chunk is given by the AUTH chunk with its
521 * HMAC field set to zero (as shown in Figure 6) followed by all
522 * chunks that are placed after the AUTH chunk in the SCTP packet.
523 */
524 if (auth)
525 sctp_auth_calculate_hmac(asoc, nskb,
526 (struct sctp_auth_chunk *)auth,
527 gfp);
528
529 /* 2) Calculate the Adler-32 checksum of the whole packet,
530 * including the SCTP common header and all the
531 * chunks.
532 *
533 * Note: Adler-32 is no longer applicable, as has been replaced
534 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
535 */
536 if (!sctp_checksum_disable) {
537 if (!(dst->dev->features & NETIF_F_SCTP_CRC) ||
538 (dst_xfrm(dst) != NULL) || packet->ipfragok) {
539 sh->checksum = sctp_compute_cksum(nskb, 0);
540 } else {
541 /* no need to seed pseudo checksum for SCTP */
542 nskb->ip_summed = CHECKSUM_PARTIAL;
543 nskb->csum_start = skb_transport_header(nskb) - nskb->head;
544 nskb->csum_offset = offsetof(struct sctphdr, checksum);
545 }
546 }
547
548 /* IP layer ECN support
549 * From RFC 2481
550 * "The ECN-Capable Transport (ECT) bit would be set by the
551 * data sender to indicate that the end-points of the
552 * transport protocol are ECN-capable."
553 *
554 * Now setting the ECT bit all the time, as it should not cause
555 * any problems protocol-wise even if our peer ignores it.
556 *
557 * Note: The works for IPv6 layer checks this bit too later
558 * in transmission. See IP6_ECN_flow_xmit().
559 */
560 tp->af_specific->ecn_capable(nskb->sk);
561
562 /* Set up the IP options. */
563 /* BUG: not implemented
564 * For v4 this all lives somewhere in sk->sk_opt...
565 */
566
567 /* Dump that on IP! */
568 if (asoc) {
569 asoc->stats.opackets++;
570 if (asoc->peer.last_sent_to != tp)
571 /* Considering the multiple CPU scenario, this is a
572 * "correcter" place for last_sent_to. --xguo
573 */
574 asoc->peer.last_sent_to = tp;
575 }
576
577 if (has_data) {
578 struct timer_list *timer;
579 unsigned long timeout;
580
581 /* Restart the AUTOCLOSE timer when sending data. */
582 if (sctp_state(asoc, ESTABLISHED) &&
583 asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
584 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
585 timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
586
587 if (!mod_timer(timer, jiffies + timeout))
588 sctp_association_hold(asoc);
589 }
590 }
591
592 pr_debug("***sctp_transmit_packet*** skb->len:%d\n", nskb->len);
593
594 nskb->ignore_df = packet->ipfragok;
595 tp->af_specific->sctp_xmit(nskb, tp);
596
597out:
598 sctp_packet_reset(packet);
599 return err;
600no_route:
601 kfree_skb(nskb);
602
603 if (asoc)
604 IP_INC_STATS(sock_net(asoc->base.sk), IPSTATS_MIB_OUTNOROUTES);
605
606 /* FIXME: Returning the 'err' will effect all the associations
607 * associated with a socket, although only one of the paths of the
608 * association is unreachable.
609 * The real failure of a transport or association can be passed on
610 * to the user via notifications. So setting this error may not be
611 * required.
612 */
613 /* err = -EHOSTUNREACH; */
614err:
615 /* Control chunks are unreliable so just drop them. DATA chunks
616 * will get resent or dropped later.
617 */
618
619 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
620 list_del_init(&chunk->list);
621 if (!sctp_chunk_is_data(chunk))
622 sctp_chunk_free(chunk);
623 }
624 goto out;
625nomem:
626 err = -ENOMEM;
627 goto err;
628}
629
630/********************************************************************
631 * 2nd Level Abstractions
632 ********************************************************************/
633
634/* This private function check to see if a chunk can be added */
635static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
636 struct sctp_chunk *chunk)
637{
638 size_t datasize, rwnd, inflight, flight_size;
639 struct sctp_transport *transport = packet->transport;
640 struct sctp_association *asoc = transport->asoc;
641 struct sctp_outq *q = &asoc->outqueue;
642
643 /* RFC 2960 6.1 Transmission of DATA Chunks
644 *
645 * A) At any given time, the data sender MUST NOT transmit new data to
646 * any destination transport address if its peer's rwnd indicates
647 * that the peer has no buffer space (i.e. rwnd is 0, see Section
648 * 6.2.1). However, regardless of the value of rwnd (including if it
649 * is 0), the data sender can always have one DATA chunk in flight to
650 * the receiver if allowed by cwnd (see rule B below). This rule
651 * allows the sender to probe for a change in rwnd that the sender
652 * missed due to the SACK having been lost in transit from the data
653 * receiver to the data sender.
654 */
655
656 rwnd = asoc->peer.rwnd;
657 inflight = q->outstanding_bytes;
658 flight_size = transport->flight_size;
659
660 datasize = sctp_data_size(chunk);
661
662 if (datasize > rwnd && inflight > 0)
663 /* We have (at least) one data chunk in flight,
664 * so we can't fall back to rule 6.1 B).
665 */
666 return SCTP_XMIT_RWND_FULL;
667
668 /* RFC 2960 6.1 Transmission of DATA Chunks
669 *
670 * B) At any given time, the sender MUST NOT transmit new data
671 * to a given transport address if it has cwnd or more bytes
672 * of data outstanding to that transport address.
673 */
674 /* RFC 7.2.4 & the Implementers Guide 2.8.
675 *
676 * 3) ...
677 * When a Fast Retransmit is being performed the sender SHOULD
678 * ignore the value of cwnd and SHOULD NOT delay retransmission.
679 */
680 if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
681 flight_size >= transport->cwnd)
682 return SCTP_XMIT_RWND_FULL;
683
684 /* Nagle's algorithm to solve small-packet problem:
685 * Inhibit the sending of new chunks when new outgoing data arrives
686 * if any previously transmitted data on the connection remains
687 * unacknowledged.
688 */
689
690 if (sctp_sk(asoc->base.sk)->nodelay)
691 /* Nagle disabled */
692 return SCTP_XMIT_OK;
693
694 if (!sctp_packet_empty(packet))
695 /* Append to packet */
696 return SCTP_XMIT_OK;
697
698 if (inflight == 0)
699 /* Nothing unacked */
700 return SCTP_XMIT_OK;
701
702 if (!sctp_state(asoc, ESTABLISHED))
703 return SCTP_XMIT_OK;
704
705 /* Check whether this chunk and all the rest of pending data will fit
706 * or delay in hopes of bundling a full sized packet.
707 */
708 if (chunk->skb->len + q->out_qlen >
709 transport->pathmtu - packet->overhead - sizeof(sctp_data_chunk_t) - 4)
710 /* Enough data queued to fill a packet */
711 return SCTP_XMIT_OK;
712
713 /* Don't delay large message writes that may have been fragmented */
714 if (!chunk->msg->can_delay)
715 return SCTP_XMIT_OK;
716
717 /* Defer until all data acked or packet full */
718 return SCTP_XMIT_DELAY;
719}
720
721/* This private function does management things when adding DATA chunk */
722static void sctp_packet_append_data(struct sctp_packet *packet,
723 struct sctp_chunk *chunk)
724{
725 struct sctp_transport *transport = packet->transport;
726 size_t datasize = sctp_data_size(chunk);
727 struct sctp_association *asoc = transport->asoc;
728 u32 rwnd = asoc->peer.rwnd;
729
730 /* Keep track of how many bytes are in flight over this transport. */
731 transport->flight_size += datasize;
732
733 /* Keep track of how many bytes are in flight to the receiver. */
734 asoc->outqueue.outstanding_bytes += datasize;
735
736 /* Update our view of the receiver's rwnd. */
737 if (datasize < rwnd)
738 rwnd -= datasize;
739 else
740 rwnd = 0;
741
742 asoc->peer.rwnd = rwnd;
743 /* Has been accepted for transmission. */
744 if (!asoc->peer.prsctp_capable)
745 chunk->msg->can_abandon = 0;
746 sctp_chunk_assign_tsn(chunk);
747 sctp_chunk_assign_ssn(chunk);
748}
749
750static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
751 struct sctp_chunk *chunk,
752 u16 chunk_len)
753{
754 size_t psize;
755 size_t pmtu;
756 int too_big;
757 sctp_xmit_t retval = SCTP_XMIT_OK;
758
759 psize = packet->size;
760 pmtu = ((packet->transport->asoc) ?
761 (packet->transport->asoc->pathmtu) :
762 (packet->transport->pathmtu));
763
764 too_big = (psize + chunk_len > pmtu);
765
766 /* Decide if we need to fragment or resubmit later. */
767 if (too_big) {
768 /* It's OK to fragmet at IP level if any one of the following
769 * is true:
770 * 1. The packet is empty (meaning this chunk is greater
771 * the MTU)
772 * 2. The chunk we are adding is a control chunk
773 * 3. The packet doesn't have any data in it yet and data
774 * requires authentication.
775 */
776 if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) ||
777 (!packet->has_data && chunk->auth)) {
778 /* We no longer do re-fragmentation.
779 * Just fragment at the IP layer, if we
780 * actually hit this condition
781 */
782 packet->ipfragok = 1;
783 } else {
784 retval = SCTP_XMIT_PMTU_FULL;
785 }
786 }
787
788 return retval;
789}
1/* SCTP kernel implementation
2 * (C) Copyright IBM Corp. 2001, 2004
3 * Copyright (c) 1999-2000 Cisco, Inc.
4 * Copyright (c) 1999-2001 Motorola, Inc.
5 *
6 * This file is part of the SCTP kernel implementation
7 *
8 * These functions handle output processing.
9 *
10 * This SCTP implementation is free software;
11 * you can redistribute it and/or modify it under the terms of
12 * the GNU General Public License as published by
13 * the Free Software Foundation; either version 2, or (at your option)
14 * any later version.
15 *
16 * This SCTP implementation is distributed in the hope that it
17 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
18 * ************************
19 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
20 * See the GNU General Public License for more details.
21 *
22 * You should have received a copy of the GNU General Public License
23 * along with GNU CC; see the file COPYING. If not, write to
24 * the Free Software Foundation, 59 Temple Place - Suite 330,
25 * Boston, MA 02111-1307, USA.
26 *
27 * Please send any bug reports or fixes you make to the
28 * email address(es):
29 * lksctp developers <lksctp-developers@lists.sourceforge.net>
30 *
31 * Or submit a bug report through the following website:
32 * http://www.sf.net/projects/lksctp
33 *
34 * Written or modified by:
35 * La Monte H.P. Yarroll <piggy@acm.org>
36 * Karl Knutson <karl@athena.chicago.il.us>
37 * Jon Grimm <jgrimm@austin.ibm.com>
38 * Sridhar Samudrala <sri@us.ibm.com>
39 *
40 * Any bugs reported given to us we will try to fix... any fixes shared will
41 * be incorporated into the next SCTP release.
42 */
43
44#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
45
46#include <linux/types.h>
47#include <linux/kernel.h>
48#include <linux/wait.h>
49#include <linux/time.h>
50#include <linux/ip.h>
51#include <linux/ipv6.h>
52#include <linux/init.h>
53#include <linux/slab.h>
54#include <net/inet_ecn.h>
55#include <net/ip.h>
56#include <net/icmp.h>
57#include <net/net_namespace.h>
58
59#include <linux/socket.h> /* for sa_family_t */
60#include <net/sock.h>
61
62#include <net/sctp/sctp.h>
63#include <net/sctp/sm.h>
64#include <net/sctp/checksum.h>
65
66/* Forward declarations for private helpers. */
67static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
68 struct sctp_chunk *chunk);
69static void sctp_packet_append_data(struct sctp_packet *packet,
70 struct sctp_chunk *chunk);
71static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
72 struct sctp_chunk *chunk,
73 u16 chunk_len);
74
75static void sctp_packet_reset(struct sctp_packet *packet)
76{
77 packet->size = packet->overhead;
78 packet->has_cookie_echo = 0;
79 packet->has_sack = 0;
80 packet->has_data = 0;
81 packet->has_auth = 0;
82 packet->ipfragok = 0;
83 packet->auth = NULL;
84}
85
86/* Config a packet.
87 * This appears to be a followup set of initializations.
88 */
89struct sctp_packet *sctp_packet_config(struct sctp_packet *packet,
90 __u32 vtag, int ecn_capable)
91{
92 struct sctp_chunk *chunk = NULL;
93
94 SCTP_DEBUG_PRINTK("%s: packet:%p vtag:0x%x\n", __func__,
95 packet, vtag);
96
97 packet->vtag = vtag;
98
99 if (ecn_capable && sctp_packet_empty(packet)) {
100 chunk = sctp_get_ecne_prepend(packet->transport->asoc);
101
102 /* If there a is a prepend chunk stick it on the list before
103 * any other chunks get appended.
104 */
105 if (chunk)
106 sctp_packet_append_chunk(packet, chunk);
107 }
108
109 return packet;
110}
111
112/* Initialize the packet structure. */
113struct sctp_packet *sctp_packet_init(struct sctp_packet *packet,
114 struct sctp_transport *transport,
115 __u16 sport, __u16 dport)
116{
117 struct sctp_association *asoc = transport->asoc;
118 size_t overhead;
119
120 SCTP_DEBUG_PRINTK("%s: packet:%p transport:%p\n", __func__,
121 packet, transport);
122
123 packet->transport = transport;
124 packet->source_port = sport;
125 packet->destination_port = dport;
126 INIT_LIST_HEAD(&packet->chunk_list);
127 if (asoc) {
128 struct sctp_sock *sp = sctp_sk(asoc->base.sk);
129 overhead = sp->pf->af->net_header_len;
130 } else {
131 overhead = sizeof(struct ipv6hdr);
132 }
133 overhead += sizeof(struct sctphdr);
134 packet->overhead = overhead;
135 sctp_packet_reset(packet);
136 packet->vtag = 0;
137 packet->malloced = 0;
138 return packet;
139}
140
141/* Free a packet. */
142void sctp_packet_free(struct sctp_packet *packet)
143{
144 struct sctp_chunk *chunk, *tmp;
145
146 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet);
147
148 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
149 list_del_init(&chunk->list);
150 sctp_chunk_free(chunk);
151 }
152
153 if (packet->malloced)
154 kfree(packet);
155}
156
157/* This routine tries to append the chunk to the offered packet. If adding
158 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
159 * is not present in the packet, it transmits the input packet.
160 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
161 * as it can fit in the packet, but any more data that does not fit in this
162 * packet can be sent only after receiving the COOKIE_ACK.
163 */
164sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet,
165 struct sctp_chunk *chunk,
166 int one_packet)
167{
168 sctp_xmit_t retval;
169 int error = 0;
170
171 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__,
172 packet, chunk);
173
174 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
175 case SCTP_XMIT_PMTU_FULL:
176 if (!packet->has_cookie_echo) {
177 error = sctp_packet_transmit(packet);
178 if (error < 0)
179 chunk->skb->sk->sk_err = -error;
180
181 /* If we have an empty packet, then we can NOT ever
182 * return PMTU_FULL.
183 */
184 if (!one_packet)
185 retval = sctp_packet_append_chunk(packet,
186 chunk);
187 }
188 break;
189
190 case SCTP_XMIT_RWND_FULL:
191 case SCTP_XMIT_OK:
192 case SCTP_XMIT_NAGLE_DELAY:
193 break;
194 }
195
196 return retval;
197}
198
199/* Try to bundle an auth chunk into the packet. */
200static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
201 struct sctp_chunk *chunk)
202{
203 struct sctp_association *asoc = pkt->transport->asoc;
204 struct sctp_chunk *auth;
205 sctp_xmit_t retval = SCTP_XMIT_OK;
206
207 /* if we don't have an association, we can't do authentication */
208 if (!asoc)
209 return retval;
210
211 /* See if this is an auth chunk we are bundling or if
212 * auth is already bundled.
213 */
214 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
215 return retval;
216
217 /* if the peer did not request this chunk to be authenticated,
218 * don't do it
219 */
220 if (!chunk->auth)
221 return retval;
222
223 auth = sctp_make_auth(asoc);
224 if (!auth)
225 return retval;
226
227 retval = sctp_packet_append_chunk(pkt, auth);
228
229 return retval;
230}
231
232/* Try to bundle a SACK with the packet. */
233static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
234 struct sctp_chunk *chunk)
235{
236 sctp_xmit_t retval = SCTP_XMIT_OK;
237
238 /* If sending DATA and haven't aleady bundled a SACK, try to
239 * bundle one in to the packet.
240 */
241 if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
242 !pkt->has_cookie_echo) {
243 struct sctp_association *asoc;
244 struct timer_list *timer;
245 asoc = pkt->transport->asoc;
246 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
247
248 /* If the SACK timer is running, we have a pending SACK */
249 if (timer_pending(timer)) {
250 struct sctp_chunk *sack;
251
252 if (pkt->transport->sack_generation !=
253 pkt->transport->asoc->peer.sack_generation)
254 return retval;
255
256 asoc->a_rwnd = asoc->rwnd;
257 sack = sctp_make_sack(asoc);
258 if (sack) {
259 retval = sctp_packet_append_chunk(pkt, sack);
260 asoc->peer.sack_needed = 0;
261 if (del_timer(timer))
262 sctp_association_put(asoc);
263 }
264 }
265 }
266 return retval;
267}
268
269/* Append a chunk to the offered packet reporting back any inability to do
270 * so.
271 */
272sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
273 struct sctp_chunk *chunk)
274{
275 sctp_xmit_t retval = SCTP_XMIT_OK;
276 __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
277
278 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet,
279 chunk);
280
281 /* Data chunks are special. Before seeing what else we can
282 * bundle into this packet, check to see if we are allowed to
283 * send this DATA.
284 */
285 if (sctp_chunk_is_data(chunk)) {
286 retval = sctp_packet_can_append_data(packet, chunk);
287 if (retval != SCTP_XMIT_OK)
288 goto finish;
289 }
290
291 /* Try to bundle AUTH chunk */
292 retval = sctp_packet_bundle_auth(packet, chunk);
293 if (retval != SCTP_XMIT_OK)
294 goto finish;
295
296 /* Try to bundle SACK chunk */
297 retval = sctp_packet_bundle_sack(packet, chunk);
298 if (retval != SCTP_XMIT_OK)
299 goto finish;
300
301 /* Check to see if this chunk will fit into the packet */
302 retval = sctp_packet_will_fit(packet, chunk, chunk_len);
303 if (retval != SCTP_XMIT_OK)
304 goto finish;
305
306 /* We believe that this chunk is OK to add to the packet */
307 switch (chunk->chunk_hdr->type) {
308 case SCTP_CID_DATA:
309 /* Account for the data being in the packet */
310 sctp_packet_append_data(packet, chunk);
311 /* Disallow SACK bundling after DATA. */
312 packet->has_sack = 1;
313 /* Disallow AUTH bundling after DATA */
314 packet->has_auth = 1;
315 /* Let it be knows that packet has DATA in it */
316 packet->has_data = 1;
317 /* timestamp the chunk for rtx purposes */
318 chunk->sent_at = jiffies;
319 break;
320 case SCTP_CID_COOKIE_ECHO:
321 packet->has_cookie_echo = 1;
322 break;
323
324 case SCTP_CID_SACK:
325 packet->has_sack = 1;
326 break;
327
328 case SCTP_CID_AUTH:
329 packet->has_auth = 1;
330 packet->auth = chunk;
331 break;
332 }
333
334 /* It is OK to send this chunk. */
335 list_add_tail(&chunk->list, &packet->chunk_list);
336 packet->size += chunk_len;
337 chunk->transport = packet->transport;
338finish:
339 return retval;
340}
341
342/* All packets are sent to the network through this function from
343 * sctp_outq_tail().
344 *
345 * The return value is a normal kernel error return value.
346 */
347int sctp_packet_transmit(struct sctp_packet *packet)
348{
349 struct sctp_transport *tp = packet->transport;
350 struct sctp_association *asoc = tp->asoc;
351 struct sctphdr *sh;
352 struct sk_buff *nskb;
353 struct sctp_chunk *chunk, *tmp;
354 struct sock *sk;
355 int err = 0;
356 int padding; /* How much padding do we need? */
357 __u8 has_data = 0;
358 struct dst_entry *dst = tp->dst;
359 unsigned char *auth = NULL; /* pointer to auth in skb data */
360 __u32 cksum_buf_len = sizeof(struct sctphdr);
361
362 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet);
363
364 /* Do NOT generate a chunkless packet. */
365 if (list_empty(&packet->chunk_list))
366 return err;
367
368 /* Set up convenience variables... */
369 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
370 sk = chunk->skb->sk;
371
372 /* Allocate the new skb. */
373 nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
374 if (!nskb)
375 goto nomem;
376
377 /* Make sure the outbound skb has enough header room reserved. */
378 skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
379
380 /* Set the owning socket so that we know where to get the
381 * destination IP address.
382 */
383 skb_set_owner_w(nskb, sk);
384
385 if (!sctp_transport_dst_check(tp)) {
386 sctp_transport_route(tp, NULL, sctp_sk(sk));
387 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
388 sctp_assoc_sync_pmtu(asoc);
389 }
390 }
391 dst = dst_clone(tp->dst);
392 skb_dst_set(nskb, dst);
393 if (!dst)
394 goto no_route;
395
396 /* Build the SCTP header. */
397 sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));
398 skb_reset_transport_header(nskb);
399 sh->source = htons(packet->source_port);
400 sh->dest = htons(packet->destination_port);
401
402 /* From 6.8 Adler-32 Checksum Calculation:
403 * After the packet is constructed (containing the SCTP common
404 * header and one or more control or DATA chunks), the
405 * transmitter shall:
406 *
407 * 1) Fill in the proper Verification Tag in the SCTP common
408 * header and initialize the checksum field to 0's.
409 */
410 sh->vtag = htonl(packet->vtag);
411 sh->checksum = 0;
412
413 /**
414 * 6.10 Bundling
415 *
416 * An endpoint bundles chunks by simply including multiple
417 * chunks in one outbound SCTP packet. ...
418 */
419
420 /**
421 * 3.2 Chunk Field Descriptions
422 *
423 * The total length of a chunk (including Type, Length and
424 * Value fields) MUST be a multiple of 4 bytes. If the length
425 * of the chunk is not a multiple of 4 bytes, the sender MUST
426 * pad the chunk with all zero bytes and this padding is not
427 * included in the chunk length field. The sender should
428 * never pad with more than 3 bytes.
429 *
430 * [This whole comment explains WORD_ROUND() below.]
431 */
432 SCTP_DEBUG_PRINTK("***sctp_transmit_packet***\n");
433 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
434 list_del_init(&chunk->list);
435 if (sctp_chunk_is_data(chunk)) {
436 /* 6.3.1 C4) When data is in flight and when allowed
437 * by rule C5, a new RTT measurement MUST be made each
438 * round trip. Furthermore, new RTT measurements
439 * SHOULD be made no more than once per round-trip
440 * for a given destination transport address.
441 */
442
443 if (!tp->rto_pending) {
444 chunk->rtt_in_progress = 1;
445 tp->rto_pending = 1;
446 }
447 has_data = 1;
448 }
449
450 padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len;
451 if (padding)
452 memset(skb_put(chunk->skb, padding), 0, padding);
453
454 /* if this is the auth chunk that we are adding,
455 * store pointer where it will be added and put
456 * the auth into the packet.
457 */
458 if (chunk == packet->auth)
459 auth = skb_tail_pointer(nskb);
460
461 cksum_buf_len += chunk->skb->len;
462 memcpy(skb_put(nskb, chunk->skb->len),
463 chunk->skb->data, chunk->skb->len);
464
465 SCTP_DEBUG_PRINTK("%s %p[%s] %s 0x%x, %s %d, %s %d, %s %d\n",
466 "*** Chunk", chunk,
467 sctp_cname(SCTP_ST_CHUNK(
468 chunk->chunk_hdr->type)),
469 chunk->has_tsn ? "TSN" : "No TSN",
470 chunk->has_tsn ?
471 ntohl(chunk->subh.data_hdr->tsn) : 0,
472 "length", ntohs(chunk->chunk_hdr->length),
473 "chunk->skb->len", chunk->skb->len,
474 "rtt_in_progress", chunk->rtt_in_progress);
475
476 /*
477 * If this is a control chunk, this is our last
478 * reference. Free data chunks after they've been
479 * acknowledged or have failed.
480 */
481 if (!sctp_chunk_is_data(chunk))
482 sctp_chunk_free(chunk);
483 }
484
485 /* SCTP-AUTH, Section 6.2
486 * The sender MUST calculate the MAC as described in RFC2104 [2]
487 * using the hash function H as described by the MAC Identifier and
488 * the shared association key K based on the endpoint pair shared key
489 * described by the shared key identifier. The 'data' used for the
490 * computation of the AUTH-chunk is given by the AUTH chunk with its
491 * HMAC field set to zero (as shown in Figure 6) followed by all
492 * chunks that are placed after the AUTH chunk in the SCTP packet.
493 */
494 if (auth)
495 sctp_auth_calculate_hmac(asoc, nskb,
496 (struct sctp_auth_chunk *)auth,
497 GFP_ATOMIC);
498
499 /* 2) Calculate the Adler-32 checksum of the whole packet,
500 * including the SCTP common header and all the
501 * chunks.
502 *
503 * Note: Adler-32 is no longer applicable, as has been replaced
504 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
505 */
506 if (!sctp_checksum_disable) {
507 if (!(dst->dev->features & NETIF_F_SCTP_CSUM)) {
508 __u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len);
509
510 /* 3) Put the resultant value into the checksum field in the
511 * common header, and leave the rest of the bits unchanged.
512 */
513 sh->checksum = sctp_end_cksum(crc32);
514 } else {
515 /* no need to seed pseudo checksum for SCTP */
516 nskb->ip_summed = CHECKSUM_PARTIAL;
517 nskb->csum_start = (skb_transport_header(nskb) -
518 nskb->head);
519 nskb->csum_offset = offsetof(struct sctphdr, checksum);
520 }
521 }
522
523 /* IP layer ECN support
524 * From RFC 2481
525 * "The ECN-Capable Transport (ECT) bit would be set by the
526 * data sender to indicate that the end-points of the
527 * transport protocol are ECN-capable."
528 *
529 * Now setting the ECT bit all the time, as it should not cause
530 * any problems protocol-wise even if our peer ignores it.
531 *
532 * Note: The works for IPv6 layer checks this bit too later
533 * in transmission. See IP6_ECN_flow_xmit().
534 */
535 (*tp->af_specific->ecn_capable)(nskb->sk);
536
537 /* Set up the IP options. */
538 /* BUG: not implemented
539 * For v4 this all lives somewhere in sk->sk_opt...
540 */
541
542 /* Dump that on IP! */
543 if (asoc && asoc->peer.last_sent_to != tp) {
544 /* Considering the multiple CPU scenario, this is a
545 * "correcter" place for last_sent_to. --xguo
546 */
547 asoc->peer.last_sent_to = tp;
548 }
549
550 if (has_data) {
551 struct timer_list *timer;
552 unsigned long timeout;
553
554 /* Restart the AUTOCLOSE timer when sending data. */
555 if (sctp_state(asoc, ESTABLISHED) && asoc->autoclose) {
556 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
557 timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
558
559 if (!mod_timer(timer, jiffies + timeout))
560 sctp_association_hold(asoc);
561 }
562 }
563
564 SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n",
565 nskb->len);
566
567 nskb->local_df = packet->ipfragok;
568 (*tp->af_specific->sctp_xmit)(nskb, tp);
569
570out:
571 sctp_packet_reset(packet);
572 return err;
573no_route:
574 kfree_skb(nskb);
575 IP_INC_STATS_BH(&init_net, IPSTATS_MIB_OUTNOROUTES);
576
577 /* FIXME: Returning the 'err' will effect all the associations
578 * associated with a socket, although only one of the paths of the
579 * association is unreachable.
580 * The real failure of a transport or association can be passed on
581 * to the user via notifications. So setting this error may not be
582 * required.
583 */
584 /* err = -EHOSTUNREACH; */
585err:
586 /* Control chunks are unreliable so just drop them. DATA chunks
587 * will get resent or dropped later.
588 */
589
590 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
591 list_del_init(&chunk->list);
592 if (!sctp_chunk_is_data(chunk))
593 sctp_chunk_free(chunk);
594 }
595 goto out;
596nomem:
597 err = -ENOMEM;
598 goto err;
599}
600
601/********************************************************************
602 * 2nd Level Abstractions
603 ********************************************************************/
604
605/* This private function check to see if a chunk can be added */
606static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
607 struct sctp_chunk *chunk)
608{
609 sctp_xmit_t retval = SCTP_XMIT_OK;
610 size_t datasize, rwnd, inflight, flight_size;
611 struct sctp_transport *transport = packet->transport;
612 struct sctp_association *asoc = transport->asoc;
613 struct sctp_outq *q = &asoc->outqueue;
614
615 /* RFC 2960 6.1 Transmission of DATA Chunks
616 *
617 * A) At any given time, the data sender MUST NOT transmit new data to
618 * any destination transport address if its peer's rwnd indicates
619 * that the peer has no buffer space (i.e. rwnd is 0, see Section
620 * 6.2.1). However, regardless of the value of rwnd (including if it
621 * is 0), the data sender can always have one DATA chunk in flight to
622 * the receiver if allowed by cwnd (see rule B below). This rule
623 * allows the sender to probe for a change in rwnd that the sender
624 * missed due to the SACK having been lost in transit from the data
625 * receiver to the data sender.
626 */
627
628 rwnd = asoc->peer.rwnd;
629 inflight = q->outstanding_bytes;
630 flight_size = transport->flight_size;
631
632 datasize = sctp_data_size(chunk);
633
634 if (datasize > rwnd) {
635 if (inflight > 0) {
636 /* We have (at least) one data chunk in flight,
637 * so we can't fall back to rule 6.1 B).
638 */
639 retval = SCTP_XMIT_RWND_FULL;
640 goto finish;
641 }
642 }
643
644 /* RFC 2960 6.1 Transmission of DATA Chunks
645 *
646 * B) At any given time, the sender MUST NOT transmit new data
647 * to a given transport address if it has cwnd or more bytes
648 * of data outstanding to that transport address.
649 */
650 /* RFC 7.2.4 & the Implementers Guide 2.8.
651 *
652 * 3) ...
653 * When a Fast Retransmit is being performed the sender SHOULD
654 * ignore the value of cwnd and SHOULD NOT delay retransmission.
655 */
656 if (chunk->fast_retransmit != SCTP_NEED_FRTX)
657 if (flight_size >= transport->cwnd) {
658 retval = SCTP_XMIT_RWND_FULL;
659 goto finish;
660 }
661
662 /* Nagle's algorithm to solve small-packet problem:
663 * Inhibit the sending of new chunks when new outgoing data arrives
664 * if any previously transmitted data on the connection remains
665 * unacknowledged.
666 */
667 if (!sctp_sk(asoc->base.sk)->nodelay && sctp_packet_empty(packet) &&
668 inflight && sctp_state(asoc, ESTABLISHED)) {
669 unsigned int max = transport->pathmtu - packet->overhead;
670 unsigned int len = chunk->skb->len + q->out_qlen;
671
672 /* Check whether this chunk and all the rest of pending
673 * data will fit or delay in hopes of bundling a full
674 * sized packet.
675 * Don't delay large message writes that may have been
676 * fragmeneted into small peices.
677 */
678 if ((len < max) && chunk->msg->can_delay) {
679 retval = SCTP_XMIT_NAGLE_DELAY;
680 goto finish;
681 }
682 }
683
684finish:
685 return retval;
686}
687
688/* This private function does management things when adding DATA chunk */
689static void sctp_packet_append_data(struct sctp_packet *packet,
690 struct sctp_chunk *chunk)
691{
692 struct sctp_transport *transport = packet->transport;
693 size_t datasize = sctp_data_size(chunk);
694 struct sctp_association *asoc = transport->asoc;
695 u32 rwnd = asoc->peer.rwnd;
696
697 /* Keep track of how many bytes are in flight over this transport. */
698 transport->flight_size += datasize;
699
700 /* Keep track of how many bytes are in flight to the receiver. */
701 asoc->outqueue.outstanding_bytes += datasize;
702
703 /* Update our view of the receiver's rwnd. */
704 if (datasize < rwnd)
705 rwnd -= datasize;
706 else
707 rwnd = 0;
708
709 asoc->peer.rwnd = rwnd;
710 /* Has been accepted for transmission. */
711 if (!asoc->peer.prsctp_capable)
712 chunk->msg->can_abandon = 0;
713 sctp_chunk_assign_tsn(chunk);
714 sctp_chunk_assign_ssn(chunk);
715}
716
717static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
718 struct sctp_chunk *chunk,
719 u16 chunk_len)
720{
721 size_t psize;
722 size_t pmtu;
723 int too_big;
724 sctp_xmit_t retval = SCTP_XMIT_OK;
725
726 psize = packet->size;
727 pmtu = ((packet->transport->asoc) ?
728 (packet->transport->asoc->pathmtu) :
729 (packet->transport->pathmtu));
730
731 too_big = (psize + chunk_len > pmtu);
732
733 /* Decide if we need to fragment or resubmit later. */
734 if (too_big) {
735 /* It's OK to fragmet at IP level if any one of the following
736 * is true:
737 * 1. The packet is empty (meaning this chunk is greater
738 * the MTU)
739 * 2. The chunk we are adding is a control chunk
740 * 3. The packet doesn't have any data in it yet and data
741 * requires authentication.
742 */
743 if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) ||
744 (!packet->has_data && chunk->auth)) {
745 /* We no longer do re-fragmentation.
746 * Just fragment at the IP layer, if we
747 * actually hit this condition
748 */
749 packet->ipfragok = 1;
750 } else {
751 retval = SCTP_XMIT_PMTU_FULL;
752 }
753 }
754
755 return retval;
756}