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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, 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}
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 asoc->a_rwnd = asoc->rwnd;
252 sack = sctp_make_sack(asoc);
253 if (sack) {
254 retval = sctp_packet_append_chunk(pkt, sack);
255 asoc->peer.sack_needed = 0;
256 if (del_timer(timer))
257 sctp_association_put(asoc);
258 }
259 }
260 }
261 return retval;
262}
263
264/* Append a chunk to the offered packet reporting back any inability to do
265 * so.
266 */
267sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
268 struct sctp_chunk *chunk)
269{
270 sctp_xmit_t retval = SCTP_XMIT_OK;
271 __u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
272
273 SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet,
274 chunk);
275
276 /* Data chunks are special. Before seeing what else we can
277 * bundle into this packet, check to see if we are allowed to
278 * send this DATA.
279 */
280 if (sctp_chunk_is_data(chunk)) {
281 retval = sctp_packet_can_append_data(packet, chunk);
282 if (retval != SCTP_XMIT_OK)
283 goto finish;
284 }
285
286 /* Try to bundle AUTH chunk */
287 retval = sctp_packet_bundle_auth(packet, chunk);
288 if (retval != SCTP_XMIT_OK)
289 goto finish;
290
291 /* Try to bundle SACK chunk */
292 retval = sctp_packet_bundle_sack(packet, chunk);
293 if (retval != SCTP_XMIT_OK)
294 goto finish;
295
296 /* Check to see if this chunk will fit into the packet */
297 retval = sctp_packet_will_fit(packet, chunk, chunk_len);
298 if (retval != SCTP_XMIT_OK)
299 goto finish;
300
301 /* We believe that this chunk is OK to add to the packet */
302 switch (chunk->chunk_hdr->type) {
303 case SCTP_CID_DATA:
304 /* Account for the data being in the packet */
305 sctp_packet_append_data(packet, chunk);
306 /* Disallow SACK bundling after DATA. */
307 packet->has_sack = 1;
308 /* Disallow AUTH bundling after DATA */
309 packet->has_auth = 1;
310 /* Let it be knows that packet has DATA in it */
311 packet->has_data = 1;
312 /* timestamp the chunk for rtx purposes */
313 chunk->sent_at = jiffies;
314 break;
315 case SCTP_CID_COOKIE_ECHO:
316 packet->has_cookie_echo = 1;
317 break;
318
319 case SCTP_CID_SACK:
320 packet->has_sack = 1;
321 break;
322
323 case SCTP_CID_AUTH:
324 packet->has_auth = 1;
325 packet->auth = chunk;
326 break;
327 }
328
329 /* It is OK to send this chunk. */
330 list_add_tail(&chunk->list, &packet->chunk_list);
331 packet->size += chunk_len;
332 chunk->transport = packet->transport;
333finish:
334 return retval;
335}
336
337/* All packets are sent to the network through this function from
338 * sctp_outq_tail().
339 *
340 * The return value is a normal kernel error return value.
341 */
342int sctp_packet_transmit(struct sctp_packet *packet)
343{
344 struct sctp_transport *tp = packet->transport;
345 struct sctp_association *asoc = tp->asoc;
346 struct sctphdr *sh;
347 struct sk_buff *nskb;
348 struct sctp_chunk *chunk, *tmp;
349 struct sock *sk;
350 int err = 0;
351 int padding; /* How much padding do we need? */
352 __u8 has_data = 0;
353 struct dst_entry *dst = tp->dst;
354 unsigned char *auth = NULL; /* pointer to auth in skb data */
355 __u32 cksum_buf_len = sizeof(struct sctphdr);
356
357 SCTP_DEBUG_PRINTK("%s: packet:%p\n", __func__, packet);
358
359 /* Do NOT generate a chunkless packet. */
360 if (list_empty(&packet->chunk_list))
361 return err;
362
363 /* Set up convenience variables... */
364 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
365 sk = chunk->skb->sk;
366
367 /* Allocate the new skb. */
368 nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
369 if (!nskb)
370 goto nomem;
371
372 /* Make sure the outbound skb has enough header room reserved. */
373 skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
374
375 /* Set the owning socket so that we know where to get the
376 * destination IP address.
377 */
378 skb_set_owner_w(nskb, sk);
379
380 /* The 'obsolete' field of dst is set to 2 when a dst is freed. */
381 if (!dst || (dst->obsolete > 1)) {
382 dst_release(dst);
383 sctp_transport_route(tp, NULL, sctp_sk(sk));
384 if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
385 sctp_assoc_sync_pmtu(asoc);
386 }
387 }
388 dst = dst_clone(tp->dst);
389 skb_dst_set(nskb, dst);
390 if (!dst)
391 goto no_route;
392
393 /* Build the SCTP header. */
394 sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));
395 skb_reset_transport_header(nskb);
396 sh->source = htons(packet->source_port);
397 sh->dest = htons(packet->destination_port);
398
399 /* From 6.8 Adler-32 Checksum Calculation:
400 * After the packet is constructed (containing the SCTP common
401 * header and one or more control or DATA chunks), the
402 * transmitter shall:
403 *
404 * 1) Fill in the proper Verification Tag in the SCTP common
405 * header and initialize the checksum field to 0's.
406 */
407 sh->vtag = htonl(packet->vtag);
408 sh->checksum = 0;
409
410 /**
411 * 6.10 Bundling
412 *
413 * An endpoint bundles chunks by simply including multiple
414 * chunks in one outbound SCTP packet. ...
415 */
416
417 /**
418 * 3.2 Chunk Field Descriptions
419 *
420 * The total length of a chunk (including Type, Length and
421 * Value fields) MUST be a multiple of 4 bytes. If the length
422 * of the chunk is not a multiple of 4 bytes, the sender MUST
423 * pad the chunk with all zero bytes and this padding is not
424 * included in the chunk length field. The sender should
425 * never pad with more than 3 bytes.
426 *
427 * [This whole comment explains WORD_ROUND() below.]
428 */
429 SCTP_DEBUG_PRINTK("***sctp_transmit_packet***\n");
430 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
431 list_del_init(&chunk->list);
432 if (sctp_chunk_is_data(chunk)) {
433 /* 6.3.1 C4) When data is in flight and when allowed
434 * by rule C5, a new RTT measurement MUST be made each
435 * round trip. Furthermore, new RTT measurements
436 * SHOULD be made no more than once per round-trip
437 * for a given destination transport address.
438 */
439
440 if (!tp->rto_pending) {
441 chunk->rtt_in_progress = 1;
442 tp->rto_pending = 1;
443 }
444 has_data = 1;
445 }
446
447 padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len;
448 if (padding)
449 memset(skb_put(chunk->skb, padding), 0, padding);
450
451 /* if this is the auth chunk that we are adding,
452 * store pointer where it will be added and put
453 * the auth into the packet.
454 */
455 if (chunk == packet->auth)
456 auth = skb_tail_pointer(nskb);
457
458 cksum_buf_len += chunk->skb->len;
459 memcpy(skb_put(nskb, chunk->skb->len),
460 chunk->skb->data, chunk->skb->len);
461
462 SCTP_DEBUG_PRINTK("%s %p[%s] %s 0x%x, %s %d, %s %d, %s %d\n",
463 "*** Chunk", chunk,
464 sctp_cname(SCTP_ST_CHUNK(
465 chunk->chunk_hdr->type)),
466 chunk->has_tsn ? "TSN" : "No TSN",
467 chunk->has_tsn ?
468 ntohl(chunk->subh.data_hdr->tsn) : 0,
469 "length", ntohs(chunk->chunk_hdr->length),
470 "chunk->skb->len", chunk->skb->len,
471 "rtt_in_progress", chunk->rtt_in_progress);
472
473 /*
474 * If this is a control chunk, this is our last
475 * reference. Free data chunks after they've been
476 * acknowledged or have failed.
477 */
478 if (!sctp_chunk_is_data(chunk))
479 sctp_chunk_free(chunk);
480 }
481
482 /* SCTP-AUTH, Section 6.2
483 * The sender MUST calculate the MAC as described in RFC2104 [2]
484 * using the hash function H as described by the MAC Identifier and
485 * the shared association key K based on the endpoint pair shared key
486 * described by the shared key identifier. The 'data' used for the
487 * computation of the AUTH-chunk is given by the AUTH chunk with its
488 * HMAC field set to zero (as shown in Figure 6) followed by all
489 * chunks that are placed after the AUTH chunk in the SCTP packet.
490 */
491 if (auth)
492 sctp_auth_calculate_hmac(asoc, nskb,
493 (struct sctp_auth_chunk *)auth,
494 GFP_ATOMIC);
495
496 /* 2) Calculate the Adler-32 checksum of the whole packet,
497 * including the SCTP common header and all the
498 * chunks.
499 *
500 * Note: Adler-32 is no longer applicable, as has been replaced
501 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
502 */
503 if (!sctp_checksum_disable) {
504 if (!(dst->dev->features & NETIF_F_SCTP_CSUM)) {
505 __u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len);
506
507 /* 3) Put the resultant value into the checksum field in the
508 * common header, and leave the rest of the bits unchanged.
509 */
510 sh->checksum = sctp_end_cksum(crc32);
511 } else {
512 /* no need to seed pseudo checksum for SCTP */
513 nskb->ip_summed = CHECKSUM_PARTIAL;
514 nskb->csum_start = (skb_transport_header(nskb) -
515 nskb->head);
516 nskb->csum_offset = offsetof(struct sctphdr, checksum);
517 }
518 }
519
520 /* IP layer ECN support
521 * From RFC 2481
522 * "The ECN-Capable Transport (ECT) bit would be set by the
523 * data sender to indicate that the end-points of the
524 * transport protocol are ECN-capable."
525 *
526 * Now setting the ECT bit all the time, as it should not cause
527 * any problems protocol-wise even if our peer ignores it.
528 *
529 * Note: The works for IPv6 layer checks this bit too later
530 * in transmission. See IP6_ECN_flow_xmit().
531 */
532 (*tp->af_specific->ecn_capable)(nskb->sk);
533
534 /* Set up the IP options. */
535 /* BUG: not implemented
536 * For v4 this all lives somewhere in sk->sk_opt...
537 */
538
539 /* Dump that on IP! */
540 if (asoc && asoc->peer.last_sent_to != tp) {
541 /* Considering the multiple CPU scenario, this is a
542 * "correcter" place for last_sent_to. --xguo
543 */
544 asoc->peer.last_sent_to = tp;
545 }
546
547 if (has_data) {
548 struct timer_list *timer;
549 unsigned long timeout;
550
551 /* Restart the AUTOCLOSE timer when sending data. */
552 if (sctp_state(asoc, ESTABLISHED) && asoc->autoclose) {
553 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
554 timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
555
556 if (!mod_timer(timer, jiffies + timeout))
557 sctp_association_hold(asoc);
558 }
559 }
560
561 SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n",
562 nskb->len);
563
564 nskb->local_df = packet->ipfragok;
565 (*tp->af_specific->sctp_xmit)(nskb, tp);
566
567out:
568 sctp_packet_reset(packet);
569 return err;
570no_route:
571 kfree_skb(nskb);
572 IP_INC_STATS_BH(&init_net, IPSTATS_MIB_OUTNOROUTES);
573
574 /* FIXME: Returning the 'err' will effect all the associations
575 * associated with a socket, although only one of the paths of the
576 * association is unreachable.
577 * The real failure of a transport or association can be passed on
578 * to the user via notifications. So setting this error may not be
579 * required.
580 */
581 /* err = -EHOSTUNREACH; */
582err:
583 /* Control chunks are unreliable so just drop them. DATA chunks
584 * will get resent or dropped later.
585 */
586
587 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
588 list_del_init(&chunk->list);
589 if (!sctp_chunk_is_data(chunk))
590 sctp_chunk_free(chunk);
591 }
592 goto out;
593nomem:
594 err = -ENOMEM;
595 goto err;
596}
597
598/********************************************************************
599 * 2nd Level Abstractions
600 ********************************************************************/
601
602/* This private function check to see if a chunk can be added */
603static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
604 struct sctp_chunk *chunk)
605{
606 sctp_xmit_t retval = SCTP_XMIT_OK;
607 size_t datasize, rwnd, inflight, flight_size;
608 struct sctp_transport *transport = packet->transport;
609 struct sctp_association *asoc = transport->asoc;
610 struct sctp_outq *q = &asoc->outqueue;
611
612 /* RFC 2960 6.1 Transmission of DATA Chunks
613 *
614 * A) At any given time, the data sender MUST NOT transmit new data to
615 * any destination transport address if its peer's rwnd indicates
616 * that the peer has no buffer space (i.e. rwnd is 0, see Section
617 * 6.2.1). However, regardless of the value of rwnd (including if it
618 * is 0), the data sender can always have one DATA chunk in flight to
619 * the receiver if allowed by cwnd (see rule B below). This rule
620 * allows the sender to probe for a change in rwnd that the sender
621 * missed due to the SACK having been lost in transit from the data
622 * receiver to the data sender.
623 */
624
625 rwnd = asoc->peer.rwnd;
626 inflight = q->outstanding_bytes;
627 flight_size = transport->flight_size;
628
629 datasize = sctp_data_size(chunk);
630
631 if (datasize > rwnd) {
632 if (inflight > 0) {
633 /* We have (at least) one data chunk in flight,
634 * so we can't fall back to rule 6.1 B).
635 */
636 retval = SCTP_XMIT_RWND_FULL;
637 goto finish;
638 }
639 }
640
641 /* RFC 2960 6.1 Transmission of DATA Chunks
642 *
643 * B) At any given time, the sender MUST NOT transmit new data
644 * to a given transport address if it has cwnd or more bytes
645 * of data outstanding to that transport address.
646 */
647 /* RFC 7.2.4 & the Implementers Guide 2.8.
648 *
649 * 3) ...
650 * When a Fast Retransmit is being performed the sender SHOULD
651 * ignore the value of cwnd and SHOULD NOT delay retransmission.
652 */
653 if (chunk->fast_retransmit != SCTP_NEED_FRTX)
654 if (flight_size >= transport->cwnd) {
655 retval = SCTP_XMIT_RWND_FULL;
656 goto finish;
657 }
658
659 /* Nagle's algorithm to solve small-packet problem:
660 * Inhibit the sending of new chunks when new outgoing data arrives
661 * if any previously transmitted data on the connection remains
662 * unacknowledged.
663 */
664 if (!sctp_sk(asoc->base.sk)->nodelay && sctp_packet_empty(packet) &&
665 inflight && sctp_state(asoc, ESTABLISHED)) {
666 unsigned max = transport->pathmtu - packet->overhead;
667 unsigned len = chunk->skb->len + q->out_qlen;
668
669 /* Check whether this chunk and all the rest of pending
670 * data will fit or delay in hopes of bundling a full
671 * sized packet.
672 * Don't delay large message writes that may have been
673 * fragmeneted into small peices.
674 */
675 if ((len < max) && chunk->msg->can_delay) {
676 retval = SCTP_XMIT_NAGLE_DELAY;
677 goto finish;
678 }
679 }
680
681finish:
682 return retval;
683}
684
685/* This private function does management things when adding DATA chunk */
686static void sctp_packet_append_data(struct sctp_packet *packet,
687 struct sctp_chunk *chunk)
688{
689 struct sctp_transport *transport = packet->transport;
690 size_t datasize = sctp_data_size(chunk);
691 struct sctp_association *asoc = transport->asoc;
692 u32 rwnd = asoc->peer.rwnd;
693
694 /* Keep track of how many bytes are in flight over this transport. */
695 transport->flight_size += datasize;
696
697 /* Keep track of how many bytes are in flight to the receiver. */
698 asoc->outqueue.outstanding_bytes += datasize;
699
700 /* Update our view of the receiver's rwnd. Include sk_buff overhead
701 * while updating peer.rwnd so that it reduces the chances of a
702 * receiver running out of receive buffer space even when receive
703 * window is still open. This can happen when a sender is sending
704 * sending small messages.
705 */
706 datasize += sizeof(struct sk_buff);
707 if (datasize < rwnd)
708 rwnd -= datasize;
709 else
710 rwnd = 0;
711
712 asoc->peer.rwnd = rwnd;
713 /* Has been accepted for transmission. */
714 if (!asoc->peer.prsctp_capable)
715 chunk->msg->can_abandon = 0;
716 sctp_chunk_assign_tsn(chunk);
717 sctp_chunk_assign_ssn(chunk);
718}
719
720static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
721 struct sctp_chunk *chunk,
722 u16 chunk_len)
723{
724 size_t psize;
725 size_t pmtu;
726 int too_big;
727 sctp_xmit_t retval = SCTP_XMIT_OK;
728
729 psize = packet->size;
730 pmtu = ((packet->transport->asoc) ?
731 (packet->transport->asoc->pathmtu) :
732 (packet->transport->pathmtu));
733
734 too_big = (psize + chunk_len > pmtu);
735
736 /* Decide if we need to fragment or resubmit later. */
737 if (too_big) {
738 /* It's OK to fragmet at IP level if any one of the following
739 * is true:
740 * 1. The packet is empty (meaning this chunk is greater
741 * the MTU)
742 * 2. The chunk we are adding is a control chunk
743 * 3. The packet doesn't have any data in it yet and data
744 * requires authentication.
745 */
746 if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) ||
747 (!packet->has_data && chunk->auth)) {
748 /* We no longer do re-fragmentation.
749 * Just fragment at the IP layer, if we
750 * actually hit this condition
751 */
752 packet->ipfragok = 1;
753 } else {
754 retval = SCTP_XMIT_PMTU_FULL;
755 }
756 }
757
758 return retval;
759}