1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* SCTP kernel implementation
3 * (C) Copyright IBM Corp. 2001, 2004
4 * Copyright (c) 1999-2000 Cisco, Inc.
5 * Copyright (c) 1999-2001 Motorola, Inc.
6 *
7 * This file is part of the SCTP kernel implementation
8 *
9 * These functions handle output processing.
10 *
11 * Please send any bug reports or fixes you make to the
12 * email address(es):
13 * lksctp developers <linux-sctp@vger.kernel.org>
14 *
15 * Written or modified by:
16 * La Monte H.P. Yarroll <piggy@acm.org>
17 * Karl Knutson <karl@athena.chicago.il.us>
18 * Jon Grimm <jgrimm@austin.ibm.com>
19 * Sridhar Samudrala <sri@us.ibm.com>
20 */
21
22 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
23
24 #include <linux/types.h>
25 #include <linux/kernel.h>
26 #include <linux/wait.h>
27 #include <linux/time.h>
28 #include <linux/ip.h>
29 #include <linux/ipv6.h>
30 #include <linux/init.h>
31 #include <linux/slab.h>
32 #include <net/inet_ecn.h>
33 #include <net/ip.h>
34 #include <net/icmp.h>
35 #include <net/net_namespace.h>
36
37 #include <linux/socket.h> /* for sa_family_t */
38 #include <net/sock.h>
39
40 #include <net/sctp/sctp.h>
41 #include <net/sctp/sm.h>
42 #include <net/sctp/checksum.h>
43
44 /* Forward declarations for private helpers. */
45 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
46 struct sctp_chunk *chunk);
47 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
48 struct sctp_chunk *chunk);
49 static void sctp_packet_append_data(struct sctp_packet *packet,
50 struct sctp_chunk *chunk);
51 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
52 struct sctp_chunk *chunk,
53 u16 chunk_len);
54
55 static void sctp_packet_reset(struct sctp_packet *packet)
56 {
57 /* sctp_packet_transmit() relies on this to reset size to the
58 * current overhead after sending packets.
59 */
60 packet->size = packet->overhead;
61
62 packet->has_cookie_echo = 0;
63 packet->has_sack = 0;
64 packet->has_data = 0;
65 packet->has_auth = 0;
66 packet->ipfragok = 0;
67 packet->auth = NULL;
68 }
69
70 /* Config a packet.
71 * This appears to be a followup set of initializations.
72 */
73 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
74 int ecn_capable)
75 {
76 struct sctp_transport *tp = packet->transport;
77 struct sctp_association *asoc = tp->asoc;
78 struct sctp_sock *sp = NULL;
79 struct sock *sk;
80
81 pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
82 packet->vtag = vtag;
83
84 /* do the following jobs only once for a flush schedule */
85 if (!sctp_packet_empty(packet))
86 return;
87
88 /* set packet max_size with pathmtu, then calculate overhead */
89 packet->max_size = tp->pathmtu;
90
91 if (asoc) {
92 sk = asoc->base.sk;
93 sp = sctp_sk(sk);
94 }
95 packet->overhead = sctp_mtu_payload(sp, 0, 0);
96 packet->size = packet->overhead;
97
98 if (!asoc)
99 return;
100
101 /* update dst or transport pathmtu if in need */
102 if (!sctp_transport_dst_check(tp)) {
103 sctp_transport_route(tp, NULL, sp);
104 if (asoc->param_flags & SPP_PMTUD_ENABLE)
105 sctp_assoc_sync_pmtu(asoc);
106 } else if (!sctp_transport_pl_enabled(tp) &&
107 asoc->param_flags & SPP_PMTUD_ENABLE) {
108 if (!sctp_transport_pmtu_check(tp))
109 sctp_assoc_sync_pmtu(asoc);
110 }
111
112 if (asoc->pmtu_pending) {
113 if (asoc->param_flags & SPP_PMTUD_ENABLE)
114 sctp_assoc_sync_pmtu(asoc);
115 asoc->pmtu_pending = 0;
116 }
117
118 /* If there a is a prepend chunk stick it on the list before
119 * any other chunks get appended.
120 */
121 if (ecn_capable) {
122 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
123
124 if (chunk)
125 sctp_packet_append_chunk(packet, chunk);
126 }
127
128 if (!tp->dst)
129 return;
130
131 /* set packet max_size with gso_max_size if gso is enabled*/
132 rcu_read_lock();
133 if (__sk_dst_get(sk) != tp->dst) {
134 dst_hold(tp->dst);
135 sk_setup_caps(sk, tp->dst);
136 }
137 packet->max_size = sk_can_gso(sk) ? min(READ_ONCE(tp->dst->dev->gso_max_size),
138 GSO_LEGACY_MAX_SIZE)
139 : asoc->pathmtu;
140 rcu_read_unlock();
141 }
142
143 /* Initialize the packet structure. */
144 void sctp_packet_init(struct sctp_packet *packet,
145 struct sctp_transport *transport,
146 __u16 sport, __u16 dport)
147 {
148 pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
149
150 packet->transport = transport;
151 packet->source_port = sport;
152 packet->destination_port = dport;
153 INIT_LIST_HEAD(&packet->chunk_list);
154 /* The overhead will be calculated by sctp_packet_config() */
155 packet->overhead = 0;
156 sctp_packet_reset(packet);
157 packet->vtag = 0;
158 }
159
160 /* Free a packet. */
161 void sctp_packet_free(struct sctp_packet *packet)
162 {
163 struct sctp_chunk *chunk, *tmp;
164
165 pr_debug("%s: packet:%p\n", __func__, packet);
166
167 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
168 list_del_init(&chunk->list);
169 sctp_chunk_free(chunk);
170 }
171 }
172
173 /* This routine tries to append the chunk to the offered packet. If adding
174 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
175 * is not present in the packet, it transmits the input packet.
176 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
177 * as it can fit in the packet, but any more data that does not fit in this
178 * packet can be sent only after receiving the COOKIE_ACK.
179 */
180 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
181 struct sctp_chunk *chunk,
182 int one_packet, gfp_t gfp)
183 {
184 enum sctp_xmit retval;
185
186 pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
187 packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
188
189 switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
190 case SCTP_XMIT_PMTU_FULL:
191 if (!packet->has_cookie_echo) {
192 int error = 0;
193
194 error = sctp_packet_transmit(packet, gfp);
195 if (error < 0)
196 chunk->skb->sk->sk_err = -error;
197
198 /* If we have an empty packet, then we can NOT ever
199 * return PMTU_FULL.
200 */
201 if (!one_packet)
202 retval = sctp_packet_append_chunk(packet,
203 chunk);
204 }
205 break;
206
207 case SCTP_XMIT_RWND_FULL:
208 case SCTP_XMIT_OK:
209 case SCTP_XMIT_DELAY:
210 break;
211 }
212
213 return retval;
214 }
215
216 /* Try to bundle a pad chunk into a packet with a heartbeat chunk for PLPMTUTD probe */
217 static enum sctp_xmit sctp_packet_bundle_pad(struct sctp_packet *pkt, struct sctp_chunk *chunk)
218 {
219 struct sctp_transport *t = pkt->transport;
220 struct sctp_chunk *pad;
221 int overhead = 0;
222
223 if (!chunk->pmtu_probe)
224 return SCTP_XMIT_OK;
225
226 /* calculate the Padding Data size for the pad chunk */
227 overhead += sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr);
228 overhead += sizeof(struct sctp_sender_hb_info) + sizeof(struct sctp_pad_chunk);
229 pad = sctp_make_pad(t->asoc, t->pl.probe_size - overhead);
230 if (!pad)
231 return SCTP_XMIT_DELAY;
232
233 list_add_tail(&pad->list, &pkt->chunk_list);
234 pkt->size += SCTP_PAD4(ntohs(pad->chunk_hdr->length));
235 chunk->transport = t;
236
237 return SCTP_XMIT_OK;
238 }
239
240 /* Try to bundle an auth chunk into the packet. */
241 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
242 struct sctp_chunk *chunk)
243 {
244 struct sctp_association *asoc = pkt->transport->asoc;
245 enum sctp_xmit retval = SCTP_XMIT_OK;
246 struct sctp_chunk *auth;
247
248 /* if we don't have an association, we can't do authentication */
249 if (!asoc)
250 return retval;
251
252 /* See if this is an auth chunk we are bundling or if
253 * auth is already bundled.
254 */
255 if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
256 return retval;
257
258 /* if the peer did not request this chunk to be authenticated,
259 * don't do it
260 */
261 if (!chunk->auth)
262 return retval;
263
264 auth = sctp_make_auth(asoc, chunk->shkey->key_id);
265 if (!auth)
266 return retval;
267
268 auth->shkey = chunk->shkey;
269 sctp_auth_shkey_hold(auth->shkey);
270
271 retval = __sctp_packet_append_chunk(pkt, auth);
272
273 if (retval != SCTP_XMIT_OK)
274 sctp_chunk_free(auth);
275
276 return retval;
277 }
278
279 /* Try to bundle a SACK with the packet. */
280 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
281 struct sctp_chunk *chunk)
282 {
283 enum sctp_xmit retval = SCTP_XMIT_OK;
284
285 /* If sending DATA and haven't aleady bundled a SACK, try to
286 * bundle one in to the packet.
287 */
288 if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
289 !pkt->has_cookie_echo) {
290 struct sctp_association *asoc;
291 struct timer_list *timer;
292 asoc = pkt->transport->asoc;
293 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
294
295 /* If the SACK timer is running, we have a pending SACK */
296 if (timer_pending(timer)) {
297 struct sctp_chunk *sack;
298
299 if (pkt->transport->sack_generation !=
300 pkt->transport->asoc->peer.sack_generation)
301 return retval;
302
303 asoc->a_rwnd = asoc->rwnd;
304 sack = sctp_make_sack(asoc);
305 if (sack) {
306 retval = __sctp_packet_append_chunk(pkt, sack);
307 if (retval != SCTP_XMIT_OK) {
308 sctp_chunk_free(sack);
309 goto out;
310 }
311 SCTP_INC_STATS(asoc->base.net,
312 SCTP_MIB_OUTCTRLCHUNKS);
313 asoc->stats.octrlchunks++;
314 asoc->peer.sack_needed = 0;
315 if (del_timer(timer))
316 sctp_association_put(asoc);
317 }
318 }
319 }
320 out:
321 return retval;
322 }
323
324
325 /* Append a chunk to the offered packet reporting back any inability to do
326 * so.
327 */
328 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
329 struct sctp_chunk *chunk)
330 {
331 __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
332 enum sctp_xmit retval = SCTP_XMIT_OK;
333
334 /* Check to see if this chunk will fit into the packet */
335 retval = sctp_packet_will_fit(packet, chunk, chunk_len);
336 if (retval != SCTP_XMIT_OK)
337 goto finish;
338
339 /* We believe that this chunk is OK to add to the packet */
340 switch (chunk->chunk_hdr->type) {
341 case SCTP_CID_DATA:
342 case SCTP_CID_I_DATA:
343 /* Account for the data being in the packet */
344 sctp_packet_append_data(packet, chunk);
345 /* Disallow SACK bundling after DATA. */
346 packet->has_sack = 1;
347 /* Disallow AUTH bundling after DATA */
348 packet->has_auth = 1;
349 /* Let it be knows that packet has DATA in it */
350 packet->has_data = 1;
351 /* timestamp the chunk for rtx purposes */
352 chunk->sent_at = jiffies;
353 /* Mainly used for prsctp RTX policy */
354 chunk->sent_count++;
355 break;
356 case SCTP_CID_COOKIE_ECHO:
357 packet->has_cookie_echo = 1;
358 break;
359
360 case SCTP_CID_SACK:
361 packet->has_sack = 1;
362 if (chunk->asoc)
363 chunk->asoc->stats.osacks++;
364 break;
365
366 case SCTP_CID_AUTH:
367 packet->has_auth = 1;
368 packet->auth = chunk;
369 break;
370 }
371
372 /* It is OK to send this chunk. */
373 list_add_tail(&chunk->list, &packet->chunk_list);
374 packet->size += chunk_len;
375 chunk->transport = packet->transport;
376 finish:
377 return retval;
378 }
379
380 /* Append a chunk to the offered packet reporting back any inability to do
381 * so.
382 */
383 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
384 struct sctp_chunk *chunk)
385 {
386 enum sctp_xmit retval = SCTP_XMIT_OK;
387
388 pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
389
390 /* Data chunks are special. Before seeing what else we can
391 * bundle into this packet, check to see if we are allowed to
392 * send this DATA.
393 */
394 if (sctp_chunk_is_data(chunk)) {
395 retval = sctp_packet_can_append_data(packet, chunk);
396 if (retval != SCTP_XMIT_OK)
397 goto finish;
398 }
399
400 /* Try to bundle AUTH chunk */
401 retval = sctp_packet_bundle_auth(packet, chunk);
402 if (retval != SCTP_XMIT_OK)
403 goto finish;
404
405 /* Try to bundle SACK chunk */
406 retval = sctp_packet_bundle_sack(packet, chunk);
407 if (retval != SCTP_XMIT_OK)
408 goto finish;
409
410 retval = __sctp_packet_append_chunk(packet, chunk);
411 if (retval != SCTP_XMIT_OK)
412 goto finish;
413
414 retval = sctp_packet_bundle_pad(packet, chunk);
415
416 finish:
417 return retval;
418 }
419
420 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
421 {
422 if (SCTP_OUTPUT_CB(head)->last == head)
423 skb_shinfo(head)->frag_list = skb;
424 else
425 SCTP_OUTPUT_CB(head)->last->next = skb;
426 SCTP_OUTPUT_CB(head)->last = skb;
427
428 head->truesize += skb->truesize;
429 head->data_len += skb->len;
430 head->len += skb->len;
431 refcount_add(skb->truesize, &head->sk->sk_wmem_alloc);
432
433 __skb_header_release(skb);
434 }
435
436 static int sctp_packet_pack(struct sctp_packet *packet,
437 struct sk_buff *head, int gso, gfp_t gfp)
438 {
439 struct sctp_transport *tp = packet->transport;
440 struct sctp_auth_chunk *auth = NULL;
441 struct sctp_chunk *chunk, *tmp;
442 int pkt_count = 0, pkt_size;
443 struct sock *sk = head->sk;
444 struct sk_buff *nskb;
445 int auth_len = 0;
446
447 if (gso) {
448 skb_shinfo(head)->gso_type = sk->sk_gso_type;
449 SCTP_OUTPUT_CB(head)->last = head;
450 } else {
451 nskb = head;
452 pkt_size = packet->size;
453 goto merge;
454 }
455
456 do {
457 /* calculate the pkt_size and alloc nskb */
458 pkt_size = packet->overhead;
459 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
460 list) {
461 int padded = SCTP_PAD4(chunk->skb->len);
462
463 if (chunk == packet->auth)
464 auth_len = padded;
465 else if (auth_len + padded + packet->overhead >
466 tp->pathmtu)
467 return 0;
468 else if (pkt_size + padded > tp->pathmtu)
469 break;
470 pkt_size += padded;
471 }
472 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
473 if (!nskb)
474 return 0;
475 skb_reserve(nskb, packet->overhead + MAX_HEADER);
476
477 merge:
478 /* merge chunks into nskb and append nskb into head list */
479 pkt_size -= packet->overhead;
480 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
481 int padding;
482
483 list_del_init(&chunk->list);
484 if (sctp_chunk_is_data(chunk)) {
485 if (!sctp_chunk_retransmitted(chunk) &&
486 !tp->rto_pending) {
487 chunk->rtt_in_progress = 1;
488 tp->rto_pending = 1;
489 }
490 }
491
492 padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
493 if (padding)
494 skb_put_zero(chunk->skb, padding);
495
496 if (chunk == packet->auth)
497 auth = (struct sctp_auth_chunk *)
498 skb_tail_pointer(nskb);
499
500 skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
501
502 pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
503 chunk,
504 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
505 chunk->has_tsn ? "TSN" : "No TSN",
506 chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
507 ntohs(chunk->chunk_hdr->length), chunk->skb->len,
508 chunk->rtt_in_progress);
509
510 pkt_size -= SCTP_PAD4(chunk->skb->len);
511
512 if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
513 sctp_chunk_free(chunk);
514
515 if (!pkt_size)
516 break;
517 }
518
519 if (auth) {
520 sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
521 packet->auth->shkey, gfp);
522 /* free auth if no more chunks, or add it back */
523 if (list_empty(&packet->chunk_list))
524 sctp_chunk_free(packet->auth);
525 else
526 list_add(&packet->auth->list,
527 &packet->chunk_list);
528 }
529
530 if (gso)
531 sctp_packet_gso_append(head, nskb);
532
533 pkt_count++;
534 } while (!list_empty(&packet->chunk_list));
535
536 if (gso) {
537 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
538 sizeof(struct inet6_skb_parm)));
539 skb_shinfo(head)->gso_segs = pkt_count;
540 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
541 goto chksum;
542 }
543
544 if (sctp_checksum_disable)
545 return 1;
546
547 if (!(tp->dst->dev->features & NETIF_F_SCTP_CRC) ||
548 dst_xfrm(tp->dst) || packet->ipfragok || tp->encap_port) {
549 struct sctphdr *sh =
550 (struct sctphdr *)skb_transport_header(head);
551
552 sh->checksum = sctp_compute_cksum(head, 0);
553 } else {
554 chksum:
555 head->ip_summed = CHECKSUM_PARTIAL;
556 head->csum_not_inet = 1;
557 head->csum_start = skb_transport_header(head) - head->head;
558 head->csum_offset = offsetof(struct sctphdr, checksum);
559 }
560
561 return pkt_count;
562 }
563
564 /* All packets are sent to the network through this function from
565 * sctp_outq_tail().
566 *
567 * The return value is always 0 for now.
568 */
569 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
570 {
571 struct sctp_transport *tp = packet->transport;
572 struct sctp_association *asoc = tp->asoc;
573 struct sctp_chunk *chunk, *tmp;
574 int pkt_count, gso = 0;
575 struct sk_buff *head;
576 struct sctphdr *sh;
577 struct sock *sk;
578
579 pr_debug("%s: packet:%p\n", __func__, packet);
580 if (list_empty(&packet->chunk_list))
581 return 0;
582 chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
583 sk = chunk->skb->sk;
584
585 if (packet->size > tp->pathmtu && !packet->ipfragok && !chunk->pmtu_probe) {
586 if (tp->pl.state == SCTP_PL_ERROR) { /* do IP fragmentation if in Error state */
587 packet->ipfragok = 1;
588 } else {
589 if (!sk_can_gso(sk)) { /* check gso */
590 pr_err_once("Trying to GSO but underlying device doesn't support it.");
591 goto out;
592 }
593 gso = 1;
594 }
595 }
596
597 /* alloc head skb */
598 head = alloc_skb((gso ? packet->overhead : packet->size) +
599 MAX_HEADER, gfp);
600 if (!head)
601 goto out;
602 skb_reserve(head, packet->overhead + MAX_HEADER);
603 skb_set_owner_w(head, sk);
604
605 /* set sctp header */
606 sh = skb_push(head, sizeof(struct sctphdr));
607 skb_reset_transport_header(head);
608 sh->source = htons(packet->source_port);
609 sh->dest = htons(packet->destination_port);
610 sh->vtag = htonl(packet->vtag);
611 sh->checksum = 0;
612
613 /* drop packet if no dst */
614 if (!tp->dst) {
615 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
616 kfree_skb(head);
617 goto out;
618 }
619
620 /* pack up chunks */
621 pkt_count = sctp_packet_pack(packet, head, gso, gfp);
622 if (!pkt_count) {
623 kfree_skb(head);
624 goto out;
625 }
626 pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
627
628 /* start autoclose timer */
629 if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
630 asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
631 struct timer_list *timer =
632 &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
633 unsigned long timeout =
634 asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
635
636 if (!mod_timer(timer, jiffies + timeout))
637 sctp_association_hold(asoc);
638 }
639
640 /* sctp xmit */
641 tp->af_specific->ecn_capable(sk);
642 if (asoc) {
643 asoc->stats.opackets += pkt_count;
644 if (asoc->peer.last_sent_to != tp)
645 asoc->peer.last_sent_to = tp;
646 }
647 head->ignore_df = packet->ipfragok;
648 if (tp->dst_pending_confirm)
649 skb_set_dst_pending_confirm(head, 1);
650 /* neighbour should be confirmed on successful transmission or
651 * positive error
652 */
653 if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
654 tp->dst_pending_confirm)
655 tp->dst_pending_confirm = 0;
656
657 out:
658 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
659 list_del_init(&chunk->list);
660 if (!sctp_chunk_is_data(chunk))
661 sctp_chunk_free(chunk);
662 }
663 sctp_packet_reset(packet);
664 return 0;
665 }
666
667 /********************************************************************
668 * 2nd Level Abstractions
669 ********************************************************************/
670
671 /* This private function check to see if a chunk can be added */
672 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
673 struct sctp_chunk *chunk)
674 {
675 size_t datasize, rwnd, inflight, flight_size;
676 struct sctp_transport *transport = packet->transport;
677 struct sctp_association *asoc = transport->asoc;
678 struct sctp_outq *q = &asoc->outqueue;
679
680 /* RFC 2960 6.1 Transmission of DATA Chunks
681 *
682 * A) At any given time, the data sender MUST NOT transmit new data to
683 * any destination transport address if its peer's rwnd indicates
684 * that the peer has no buffer space (i.e. rwnd is 0, see Section
685 * 6.2.1). However, regardless of the value of rwnd (including if it
686 * is 0), the data sender can always have one DATA chunk in flight to
687 * the receiver if allowed by cwnd (see rule B below). This rule
688 * allows the sender to probe for a change in rwnd that the sender
689 * missed due to the SACK having been lost in transit from the data
690 * receiver to the data sender.
691 */
692
693 rwnd = asoc->peer.rwnd;
694 inflight = q->outstanding_bytes;
695 flight_size = transport->flight_size;
696
697 datasize = sctp_data_size(chunk);
698
699 if (datasize > rwnd && inflight > 0)
700 /* We have (at least) one data chunk in flight,
701 * so we can't fall back to rule 6.1 B).
702 */
703 return SCTP_XMIT_RWND_FULL;
704
705 /* RFC 2960 6.1 Transmission of DATA Chunks
706 *
707 * B) At any given time, the sender MUST NOT transmit new data
708 * to a given transport address if it has cwnd or more bytes
709 * of data outstanding to that transport address.
710 */
711 /* RFC 7.2.4 & the Implementers Guide 2.8.
712 *
713 * 3) ...
714 * When a Fast Retransmit is being performed the sender SHOULD
715 * ignore the value of cwnd and SHOULD NOT delay retransmission.
716 */
717 if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
718 flight_size >= transport->cwnd)
719 return SCTP_XMIT_RWND_FULL;
720
721 /* Nagle's algorithm to solve small-packet problem:
722 * Inhibit the sending of new chunks when new outgoing data arrives
723 * if any previously transmitted data on the connection remains
724 * unacknowledged.
725 */
726
727 if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
728 !asoc->force_delay)
729 /* Nothing unacked */
730 return SCTP_XMIT_OK;
731
732 if (!sctp_packet_empty(packet))
733 /* Append to packet */
734 return SCTP_XMIT_OK;
735
736 if (!sctp_state(asoc, ESTABLISHED))
737 return SCTP_XMIT_OK;
738
739 /* Check whether this chunk and all the rest of pending data will fit
740 * or delay in hopes of bundling a full sized packet.
741 */
742 if (chunk->skb->len + q->out_qlen > transport->pathmtu -
743 packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
744 /* Enough data queued to fill a packet */
745 return SCTP_XMIT_OK;
746
747 /* Don't delay large message writes that may have been fragmented */
748 if (!chunk->msg->can_delay)
749 return SCTP_XMIT_OK;
750
751 /* Defer until all data acked or packet full */
752 return SCTP_XMIT_DELAY;
753 }
754
755 /* This private function does management things when adding DATA chunk */
756 static void sctp_packet_append_data(struct sctp_packet *packet,
757 struct sctp_chunk *chunk)
758 {
759 struct sctp_transport *transport = packet->transport;
760 size_t datasize = sctp_data_size(chunk);
761 struct sctp_association *asoc = transport->asoc;
762 u32 rwnd = asoc->peer.rwnd;
763
764 /* Keep track of how many bytes are in flight over this transport. */
765 transport->flight_size += datasize;
766
767 /* Keep track of how many bytes are in flight to the receiver. */
768 asoc->outqueue.outstanding_bytes += datasize;
769
770 /* Update our view of the receiver's rwnd. */
771 if (datasize < rwnd)
772 rwnd -= datasize;
773 else
774 rwnd = 0;
775
776 asoc->peer.rwnd = rwnd;
777 sctp_chunk_assign_tsn(chunk);
778 asoc->stream.si->assign_number(chunk);
779 }
780
781 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
782 struct sctp_chunk *chunk,
783 u16 chunk_len)
784 {
785 enum sctp_xmit retval = SCTP_XMIT_OK;
786 size_t psize, pmtu, maxsize;
787
788 /* Don't bundle in this packet if this chunk's auth key doesn't
789 * match other chunks already enqueued on this packet. Also,
790 * don't bundle the chunk with auth key if other chunks in this
791 * packet don't have auth key.
792 */
793 if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
794 (!packet->auth && chunk->shkey &&
795 chunk->chunk_hdr->type != SCTP_CID_AUTH))
796 return SCTP_XMIT_PMTU_FULL;
797
798 psize = packet->size;
799 if (packet->transport->asoc)
800 pmtu = packet->transport->asoc->pathmtu;
801 else
802 pmtu = packet->transport->pathmtu;
803
804 /* Decide if we need to fragment or resubmit later. */
805 if (psize + chunk_len > pmtu) {
806 /* It's OK to fragment at IP level if any one of the following
807 * is true:
808 * 1. The packet is empty (meaning this chunk is greater
809 * the MTU)
810 * 2. The packet doesn't have any data in it yet and data
811 * requires authentication.
812 */
813 if (sctp_packet_empty(packet) ||
814 (!packet->has_data && chunk->auth)) {
815 /* We no longer do re-fragmentation.
816 * Just fragment at the IP layer, if we
817 * actually hit this condition
818 */
819 packet->ipfragok = 1;
820 goto out;
821 }
822
823 /* Similarly, if this chunk was built before a PMTU
824 * reduction, we have to fragment it at IP level now. So
825 * if the packet already contains something, we need to
826 * flush.
827 */
828 maxsize = pmtu - packet->overhead;
829 if (packet->auth)
830 maxsize -= SCTP_PAD4(packet->auth->skb->len);
831 if (chunk_len > maxsize)
832 retval = SCTP_XMIT_PMTU_FULL;
833
834 /* It is also okay to fragment if the chunk we are
835 * adding is a control chunk, but only if current packet
836 * is not a GSO one otherwise it causes fragmentation of
837 * a large frame. So in this case we allow the
838 * fragmentation by forcing it to be in a new packet.
839 */
840 if (!sctp_chunk_is_data(chunk) && packet->has_data)
841 retval = SCTP_XMIT_PMTU_FULL;
842
843 if (psize + chunk_len > packet->max_size)
844 /* Hit GSO/PMTU limit, gotta flush */
845 retval = SCTP_XMIT_PMTU_FULL;
846
847 if (!packet->transport->burst_limited &&
848 psize + chunk_len > (packet->transport->cwnd >> 1))
849 /* Do not allow a single GSO packet to use more
850 * than half of cwnd.
851 */
852 retval = SCTP_XMIT_PMTU_FULL;
853
854 if (packet->transport->burst_limited &&
855 psize + chunk_len > (packet->transport->burst_limited >> 1))
856 /* Do not allow a single GSO packet to use more
857 * than half of original cwnd.
858 */
859 retval = SCTP_XMIT_PMTU_FULL;
860 /* Otherwise it will fit in the GSO packet */
861 }
862
863 out:
864 return retval;
865 }
866
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