Merge tag 'selinux-pr-20180403' of git://git.kernel.org/pub/scm/linux/kernel/git...
[muen/linux.git] / net / sctp / output.c
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. */
60 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
61                                                  struct sctp_chunk *chunk);
62 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
63                                                   struct sctp_chunk *chunk);
64 static void sctp_packet_append_data(struct sctp_packet *packet,
65                                     struct sctp_chunk *chunk);
66 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
67                                            struct sctp_chunk *chunk,
68                                            u16 chunk_len);
69
70 static void sctp_packet_reset(struct sctp_packet *packet)
71 {
72         /* sctp_packet_transmit() relies on this to reset size to the
73          * current overhead after sending packets.
74          */
75         packet->size = packet->overhead;
76
77         packet->has_cookie_echo = 0;
78         packet->has_sack = 0;
79         packet->has_data = 0;
80         packet->has_auth = 0;
81         packet->ipfragok = 0;
82         packet->auth = NULL;
83 }
84
85 /* Config a packet.
86  * This appears to be a followup set of initializations.
87  */
88 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
89                         int ecn_capable)
90 {
91         struct sctp_transport *tp = packet->transport;
92         struct sctp_association *asoc = tp->asoc;
93         struct sock *sk;
94         size_t overhead = sizeof(struct ipv6hdr) + sizeof(struct sctphdr);
95
96         pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
97         packet->vtag = vtag;
98
99         /* do the following jobs only once for a flush schedule */
100         if (!sctp_packet_empty(packet))
101                 return;
102
103         /* set packet max_size with pathmtu, then calculate overhead */
104         packet->max_size = tp->pathmtu;
105         if (asoc) {
106                 struct sctp_sock *sp = sctp_sk(asoc->base.sk);
107                 struct sctp_af *af = sp->pf->af;
108
109                 overhead = af->net_header_len +
110                            af->ip_options_len(asoc->base.sk);
111                 overhead += sizeof(struct sctphdr);
112                 packet->overhead = overhead;
113                 packet->size = overhead;
114         } else {
115                 packet->overhead = overhead;
116                 packet->size = overhead;
117                 return;
118         }
119
120         /* update dst or transport pathmtu if in need */
121         sk = asoc->base.sk;
122         if (!sctp_transport_dst_check(tp)) {
123                 sctp_transport_route(tp, NULL, sctp_sk(sk));
124                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
125                         sctp_assoc_sync_pmtu(asoc);
126         } else if (!sctp_transport_pmtu_check(tp)) {
127                 if (asoc->param_flags & SPP_PMTUD_ENABLE)
128                         sctp_assoc_sync_pmtu(asoc);
129         }
130
131         /* If there a is a prepend chunk stick it on the list before
132          * any other chunks get appended.
133          */
134         if (ecn_capable) {
135                 struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
136
137                 if (chunk)
138                         sctp_packet_append_chunk(packet, chunk);
139         }
140
141         if (!tp->dst)
142                 return;
143
144         /* set packet max_size with gso_max_size if gso is enabled*/
145         rcu_read_lock();
146         if (__sk_dst_get(sk) != tp->dst) {
147                 dst_hold(tp->dst);
148                 sk_setup_caps(sk, tp->dst);
149         }
150         packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
151                                           : asoc->pathmtu;
152         rcu_read_unlock();
153 }
154
155 /* Initialize the packet structure. */
156 void sctp_packet_init(struct sctp_packet *packet,
157                       struct sctp_transport *transport,
158                       __u16 sport, __u16 dport)
159 {
160         pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
161
162         packet->transport = transport;
163         packet->source_port = sport;
164         packet->destination_port = dport;
165         INIT_LIST_HEAD(&packet->chunk_list);
166         /* The overhead will be calculated by sctp_packet_config() */
167         packet->overhead = 0;
168         sctp_packet_reset(packet);
169         packet->vtag = 0;
170 }
171
172 /* Free a packet.  */
173 void sctp_packet_free(struct sctp_packet *packet)
174 {
175         struct sctp_chunk *chunk, *tmp;
176
177         pr_debug("%s: packet:%p\n", __func__, packet);
178
179         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
180                 list_del_init(&chunk->list);
181                 sctp_chunk_free(chunk);
182         }
183 }
184
185 /* This routine tries to append the chunk to the offered packet. If adding
186  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
187  * is not present in the packet, it transmits the input packet.
188  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
189  * as it can fit in the packet, but any more data that does not fit in this
190  * packet can be sent only after receiving the COOKIE_ACK.
191  */
192 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
193                                           struct sctp_chunk *chunk,
194                                           int one_packet, gfp_t gfp)
195 {
196         enum sctp_xmit retval;
197
198         pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
199                  packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
200
201         switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
202         case SCTP_XMIT_PMTU_FULL:
203                 if (!packet->has_cookie_echo) {
204                         int error = 0;
205
206                         error = sctp_packet_transmit(packet, gfp);
207                         if (error < 0)
208                                 chunk->skb->sk->sk_err = -error;
209
210                         /* If we have an empty packet, then we can NOT ever
211                          * return PMTU_FULL.
212                          */
213                         if (!one_packet)
214                                 retval = sctp_packet_append_chunk(packet,
215                                                                   chunk);
216                 }
217                 break;
218
219         case SCTP_XMIT_RWND_FULL:
220         case SCTP_XMIT_OK:
221         case SCTP_XMIT_DELAY:
222                 break;
223         }
224
225         return retval;
226 }
227
228 /* Try to bundle an auth chunk into the packet. */
229 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
230                                               struct sctp_chunk *chunk)
231 {
232         struct sctp_association *asoc = pkt->transport->asoc;
233         enum sctp_xmit retval = SCTP_XMIT_OK;
234         struct sctp_chunk *auth;
235
236         /* if we don't have an association, we can't do authentication */
237         if (!asoc)
238                 return retval;
239
240         /* See if this is an auth chunk we are bundling or if
241          * auth is already bundled.
242          */
243         if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
244                 return retval;
245
246         /* if the peer did not request this chunk to be authenticated,
247          * don't do it
248          */
249         if (!chunk->auth)
250                 return retval;
251
252         auth = sctp_make_auth(asoc, chunk->shkey->key_id);
253         if (!auth)
254                 return retval;
255
256         auth->shkey = chunk->shkey;
257         sctp_auth_shkey_hold(auth->shkey);
258
259         retval = __sctp_packet_append_chunk(pkt, auth);
260
261         if (retval != SCTP_XMIT_OK)
262                 sctp_chunk_free(auth);
263
264         return retval;
265 }
266
267 /* Try to bundle a SACK with the packet. */
268 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
269                                               struct sctp_chunk *chunk)
270 {
271         enum sctp_xmit retval = SCTP_XMIT_OK;
272
273         /* If sending DATA and haven't aleady bundled a SACK, try to
274          * bundle one in to the packet.
275          */
276         if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
277             !pkt->has_cookie_echo) {
278                 struct sctp_association *asoc;
279                 struct timer_list *timer;
280                 asoc = pkt->transport->asoc;
281                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
282
283                 /* If the SACK timer is running, we have a pending SACK */
284                 if (timer_pending(timer)) {
285                         struct sctp_chunk *sack;
286
287                         if (pkt->transport->sack_generation !=
288                             pkt->transport->asoc->peer.sack_generation)
289                                 return retval;
290
291                         asoc->a_rwnd = asoc->rwnd;
292                         sack = sctp_make_sack(asoc);
293                         if (sack) {
294                                 retval = __sctp_packet_append_chunk(pkt, sack);
295                                 if (retval != SCTP_XMIT_OK) {
296                                         sctp_chunk_free(sack);
297                                         goto out;
298                                 }
299                                 asoc->peer.sack_needed = 0;
300                                 if (del_timer(timer))
301                                         sctp_association_put(asoc);
302                         }
303                 }
304         }
305 out:
306         return retval;
307 }
308
309
310 /* Append a chunk to the offered packet reporting back any inability to do
311  * so.
312  */
313 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
314                                                  struct sctp_chunk *chunk)
315 {
316         __u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
317         enum sctp_xmit retval = SCTP_XMIT_OK;
318
319         /* Check to see if this chunk will fit into the packet */
320         retval = sctp_packet_will_fit(packet, chunk, chunk_len);
321         if (retval != SCTP_XMIT_OK)
322                 goto finish;
323
324         /* We believe that this chunk is OK to add to the packet */
325         switch (chunk->chunk_hdr->type) {
326         case SCTP_CID_DATA:
327         case SCTP_CID_I_DATA:
328                 /* Account for the data being in the packet */
329                 sctp_packet_append_data(packet, chunk);
330                 /* Disallow SACK bundling after DATA. */
331                 packet->has_sack = 1;
332                 /* Disallow AUTH bundling after DATA */
333                 packet->has_auth = 1;
334                 /* Let it be knows that packet has DATA in it */
335                 packet->has_data = 1;
336                 /* timestamp the chunk for rtx purposes */
337                 chunk->sent_at = jiffies;
338                 /* Mainly used for prsctp RTX policy */
339                 chunk->sent_count++;
340                 break;
341         case SCTP_CID_COOKIE_ECHO:
342                 packet->has_cookie_echo = 1;
343                 break;
344
345         case SCTP_CID_SACK:
346                 packet->has_sack = 1;
347                 if (chunk->asoc)
348                         chunk->asoc->stats.osacks++;
349                 break;
350
351         case SCTP_CID_AUTH:
352                 packet->has_auth = 1;
353                 packet->auth = chunk;
354                 break;
355         }
356
357         /* It is OK to send this chunk.  */
358         list_add_tail(&chunk->list, &packet->chunk_list);
359         packet->size += chunk_len;
360         chunk->transport = packet->transport;
361 finish:
362         return retval;
363 }
364
365 /* Append a chunk to the offered packet reporting back any inability to do
366  * so.
367  */
368 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
369                                         struct sctp_chunk *chunk)
370 {
371         enum sctp_xmit retval = SCTP_XMIT_OK;
372
373         pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
374
375         /* Data chunks are special.  Before seeing what else we can
376          * bundle into this packet, check to see if we are allowed to
377          * send this DATA.
378          */
379         if (sctp_chunk_is_data(chunk)) {
380                 retval = sctp_packet_can_append_data(packet, chunk);
381                 if (retval != SCTP_XMIT_OK)
382                         goto finish;
383         }
384
385         /* Try to bundle AUTH chunk */
386         retval = sctp_packet_bundle_auth(packet, chunk);
387         if (retval != SCTP_XMIT_OK)
388                 goto finish;
389
390         /* Try to bundle SACK chunk */
391         retval = sctp_packet_bundle_sack(packet, chunk);
392         if (retval != SCTP_XMIT_OK)
393                 goto finish;
394
395         retval = __sctp_packet_append_chunk(packet, chunk);
396
397 finish:
398         return retval;
399 }
400
401 static void sctp_packet_release_owner(struct sk_buff *skb)
402 {
403         sk_free(skb->sk);
404 }
405
406 static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
407 {
408         skb_orphan(skb);
409         skb->sk = sk;
410         skb->destructor = sctp_packet_release_owner;
411
412         /*
413          * The data chunks have already been accounted for in sctp_sendmsg(),
414          * therefore only reserve a single byte to keep socket around until
415          * the packet has been transmitted.
416          */
417         refcount_inc(&sk->sk_wmem_alloc);
418 }
419
420 static int sctp_packet_pack(struct sctp_packet *packet,
421                             struct sk_buff *head, int gso, gfp_t gfp)
422 {
423         struct sctp_transport *tp = packet->transport;
424         struct sctp_auth_chunk *auth = NULL;
425         struct sctp_chunk *chunk, *tmp;
426         int pkt_count = 0, pkt_size;
427         struct sock *sk = head->sk;
428         struct sk_buff *nskb;
429         int auth_len = 0;
430
431         if (gso) {
432                 skb_shinfo(head)->gso_type = sk->sk_gso_type;
433                 NAPI_GRO_CB(head)->last = head;
434         } else {
435                 nskb = head;
436                 pkt_size = packet->size;
437                 goto merge;
438         }
439
440         do {
441                 /* calculate the pkt_size and alloc nskb */
442                 pkt_size = packet->overhead;
443                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
444                                          list) {
445                         int padded = SCTP_PAD4(chunk->skb->len);
446
447                         if (chunk == packet->auth)
448                                 auth_len = padded;
449                         else if (auth_len + padded + packet->overhead >
450                                  tp->pathmtu)
451                                 return 0;
452                         else if (pkt_size + padded > tp->pathmtu)
453                                 break;
454                         pkt_size += padded;
455                 }
456                 nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
457                 if (!nskb)
458                         return 0;
459                 skb_reserve(nskb, packet->overhead + MAX_HEADER);
460
461 merge:
462                 /* merge chunks into nskb and append nskb into head list */
463                 pkt_size -= packet->overhead;
464                 list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
465                         int padding;
466
467                         list_del_init(&chunk->list);
468                         if (sctp_chunk_is_data(chunk)) {
469                                 if (!sctp_chunk_retransmitted(chunk) &&
470                                     !tp->rto_pending) {
471                                         chunk->rtt_in_progress = 1;
472                                         tp->rto_pending = 1;
473                                 }
474                         }
475
476                         padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
477                         if (padding)
478                                 skb_put_zero(chunk->skb, padding);
479
480                         if (chunk == packet->auth)
481                                 auth = (struct sctp_auth_chunk *)
482                                                         skb_tail_pointer(nskb);
483
484                         skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
485
486                         pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
487                                  chunk,
488                                  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
489                                  chunk->has_tsn ? "TSN" : "No TSN",
490                                  chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
491                                  ntohs(chunk->chunk_hdr->length), chunk->skb->len,
492                                  chunk->rtt_in_progress);
493
494                         pkt_size -= SCTP_PAD4(chunk->skb->len);
495
496                         if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
497                                 sctp_chunk_free(chunk);
498
499                         if (!pkt_size)
500                                 break;
501                 }
502
503                 if (auth) {
504                         sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
505                                                  packet->auth->shkey, gfp);
506                         /* free auth if no more chunks, or add it back */
507                         if (list_empty(&packet->chunk_list))
508                                 sctp_chunk_free(packet->auth);
509                         else
510                                 list_add(&packet->auth->list,
511                                          &packet->chunk_list);
512                 }
513
514                 if (gso) {
515                         if (skb_gro_receive(&head, nskb)) {
516                                 kfree_skb(nskb);
517                                 return 0;
518                         }
519                         if (WARN_ON_ONCE(skb_shinfo(head)->gso_segs >=
520                                          sk->sk_gso_max_segs))
521                                 return 0;
522                 }
523
524                 pkt_count++;
525         } while (!list_empty(&packet->chunk_list));
526
527         if (gso) {
528                 memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
529                                         sizeof(struct inet6_skb_parm)));
530                 skb_shinfo(head)->gso_segs = pkt_count;
531                 skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
532                 rcu_read_lock();
533                 if (skb_dst(head) != tp->dst) {
534                         dst_hold(tp->dst);
535                         sk_setup_caps(sk, tp->dst);
536                 }
537                 rcu_read_unlock();
538                 goto chksum;
539         }
540
541         if (sctp_checksum_disable)
542                 return 1;
543
544         if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
545             dst_xfrm(skb_dst(head)) || packet->ipfragok) {
546                 struct sctphdr *sh =
547                         (struct sctphdr *)skb_transport_header(head);
548
549                 sh->checksum = sctp_compute_cksum(head, 0);
550         } else {
551 chksum:
552                 head->ip_summed = CHECKSUM_PARTIAL;
553                 head->csum_not_inet = 1;
554                 head->csum_start = skb_transport_header(head) - head->head;
555                 head->csum_offset = offsetof(struct sctphdr, checksum);
556         }
557
558         return pkt_count;
559 }
560
561 /* All packets are sent to the network through this function from
562  * sctp_outq_tail().
563  *
564  * The return value is always 0 for now.
565  */
566 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
567 {
568         struct sctp_transport *tp = packet->transport;
569         struct sctp_association *asoc = tp->asoc;
570         struct sctp_chunk *chunk, *tmp;
571         int pkt_count, gso = 0;
572         struct dst_entry *dst;
573         struct sk_buff *head;
574         struct sctphdr *sh;
575         struct sock *sk;
576
577         pr_debug("%s: packet:%p\n", __func__, packet);
578         if (list_empty(&packet->chunk_list))
579                 return 0;
580         chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
581         sk = chunk->skb->sk;
582
583         /* check gso */
584         if (packet->size > tp->pathmtu && !packet->ipfragok) {
585                 if (!sk_can_gso(sk)) {
586                         pr_err_once("Trying to GSO but underlying device doesn't support it.");
587                         goto out;
588                 }
589                 gso = 1;
590         }
591
592         /* alloc head skb */
593         head = alloc_skb((gso ? packet->overhead : packet->size) +
594                          MAX_HEADER, gfp);
595         if (!head)
596                 goto out;
597         skb_reserve(head, packet->overhead + MAX_HEADER);
598         sctp_packet_set_owner_w(head, sk);
599
600         /* set sctp header */
601         sh = skb_push(head, sizeof(struct sctphdr));
602         skb_reset_transport_header(head);
603         sh->source = htons(packet->source_port);
604         sh->dest = htons(packet->destination_port);
605         sh->vtag = htonl(packet->vtag);
606         sh->checksum = 0;
607
608         /* drop packet if no dst */
609         dst = dst_clone(tp->dst);
610         if (!dst) {
611                 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
612                 kfree_skb(head);
613                 goto out;
614         }
615         skb_dst_set(head, dst);
616
617         /* pack up chunks */
618         pkt_count = sctp_packet_pack(packet, head, gso, gfp);
619         if (!pkt_count) {
620                 kfree_skb(head);
621                 goto out;
622         }
623         pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
624
625         /* start autoclose timer */
626         if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
627             asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
628                 struct timer_list *timer =
629                         &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
630                 unsigned long timeout =
631                         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
632
633                 if (!mod_timer(timer, jiffies + timeout))
634                         sctp_association_hold(asoc);
635         }
636
637         /* sctp xmit */
638         tp->af_specific->ecn_capable(sk);
639         if (asoc) {
640                 asoc->stats.opackets += pkt_count;
641                 if (asoc->peer.last_sent_to != tp)
642                         asoc->peer.last_sent_to = tp;
643         }
644         head->ignore_df = packet->ipfragok;
645         if (tp->dst_pending_confirm)
646                 skb_set_dst_pending_confirm(head, 1);
647         /* neighbour should be confirmed on successful transmission or
648          * positive error
649          */
650         if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
651             tp->dst_pending_confirm)
652                 tp->dst_pending_confirm = 0;
653
654 out:
655         list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
656                 list_del_init(&chunk->list);
657                 if (!sctp_chunk_is_data(chunk))
658                         sctp_chunk_free(chunk);
659         }
660         sctp_packet_reset(packet);
661         return 0;
662 }
663
664 /********************************************************************
665  * 2nd Level Abstractions
666  ********************************************************************/
667
668 /* This private function check to see if a chunk can be added */
669 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
670                                                   struct sctp_chunk *chunk)
671 {
672         size_t datasize, rwnd, inflight, flight_size;
673         struct sctp_transport *transport = packet->transport;
674         struct sctp_association *asoc = transport->asoc;
675         struct sctp_outq *q = &asoc->outqueue;
676
677         /* RFC 2960 6.1  Transmission of DATA Chunks
678          *
679          * A) At any given time, the data sender MUST NOT transmit new data to
680          * any destination transport address if its peer's rwnd indicates
681          * that the peer has no buffer space (i.e. rwnd is 0, see Section
682          * 6.2.1).  However, regardless of the value of rwnd (including if it
683          * is 0), the data sender can always have one DATA chunk in flight to
684          * the receiver if allowed by cwnd (see rule B below).  This rule
685          * allows the sender to probe for a change in rwnd that the sender
686          * missed due to the SACK having been lost in transit from the data
687          * receiver to the data sender.
688          */
689
690         rwnd = asoc->peer.rwnd;
691         inflight = q->outstanding_bytes;
692         flight_size = transport->flight_size;
693
694         datasize = sctp_data_size(chunk);
695
696         if (datasize > rwnd && inflight > 0)
697                 /* We have (at least) one data chunk in flight,
698                  * so we can't fall back to rule 6.1 B).
699                  */
700                 return SCTP_XMIT_RWND_FULL;
701
702         /* RFC 2960 6.1  Transmission of DATA Chunks
703          *
704          * B) At any given time, the sender MUST NOT transmit new data
705          * to a given transport address if it has cwnd or more bytes
706          * of data outstanding to that transport address.
707          */
708         /* RFC 7.2.4 & the Implementers Guide 2.8.
709          *
710          * 3) ...
711          *    When a Fast Retransmit is being performed the sender SHOULD
712          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
713          */
714         if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
715             flight_size >= transport->cwnd)
716                 return SCTP_XMIT_RWND_FULL;
717
718         /* Nagle's algorithm to solve small-packet problem:
719          * Inhibit the sending of new chunks when new outgoing data arrives
720          * if any previously transmitted data on the connection remains
721          * unacknowledged.
722          */
723
724         if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
725             !asoc->force_delay)
726                 /* Nothing unacked */
727                 return SCTP_XMIT_OK;
728
729         if (!sctp_packet_empty(packet))
730                 /* Append to packet */
731                 return SCTP_XMIT_OK;
732
733         if (!sctp_state(asoc, ESTABLISHED))
734                 return SCTP_XMIT_OK;
735
736         /* Check whether this chunk and all the rest of pending data will fit
737          * or delay in hopes of bundling a full sized packet.
738          */
739         if (chunk->skb->len + q->out_qlen > transport->pathmtu -
740             packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
741                 /* Enough data queued to fill a packet */
742                 return SCTP_XMIT_OK;
743
744         /* Don't delay large message writes that may have been fragmented */
745         if (!chunk->msg->can_delay)
746                 return SCTP_XMIT_OK;
747
748         /* Defer until all data acked or packet full */
749         return SCTP_XMIT_DELAY;
750 }
751
752 /* This private function does management things when adding DATA chunk */
753 static void sctp_packet_append_data(struct sctp_packet *packet,
754                                 struct sctp_chunk *chunk)
755 {
756         struct sctp_transport *transport = packet->transport;
757         size_t datasize = sctp_data_size(chunk);
758         struct sctp_association *asoc = transport->asoc;
759         u32 rwnd = asoc->peer.rwnd;
760
761         /* Keep track of how many bytes are in flight over this transport. */
762         transport->flight_size += datasize;
763
764         /* Keep track of how many bytes are in flight to the receiver. */
765         asoc->outqueue.outstanding_bytes += datasize;
766
767         /* Update our view of the receiver's rwnd. */
768         if (datasize < rwnd)
769                 rwnd -= datasize;
770         else
771                 rwnd = 0;
772
773         asoc->peer.rwnd = rwnd;
774         sctp_chunk_assign_tsn(chunk);
775         asoc->stream.si->assign_number(chunk);
776 }
777
778 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
779                                            struct sctp_chunk *chunk,
780                                            u16 chunk_len)
781 {
782         enum sctp_xmit retval = SCTP_XMIT_OK;
783         size_t psize, pmtu, maxsize;
784
785         /* Don't bundle in this packet if this chunk's auth key doesn't
786          * match other chunks already enqueued on this packet. Also,
787          * don't bundle the chunk with auth key if other chunks in this
788          * packet don't have auth key.
789          */
790         if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
791             (!packet->auth && chunk->shkey &&
792              chunk->chunk_hdr->type != SCTP_CID_AUTH))
793                 return SCTP_XMIT_PMTU_FULL;
794
795         psize = packet->size;
796         if (packet->transport->asoc)
797                 pmtu = packet->transport->asoc->pathmtu;
798         else
799                 pmtu = packet->transport->pathmtu;
800
801         /* Decide if we need to fragment or resubmit later. */
802         if (psize + chunk_len > pmtu) {
803                 /* It's OK to fragment at IP level if any one of the following
804                  * is true:
805                  *      1. The packet is empty (meaning this chunk is greater
806                  *         the MTU)
807                  *      2. The packet doesn't have any data in it yet and data
808                  *         requires authentication.
809                  */
810                 if (sctp_packet_empty(packet) ||
811                     (!packet->has_data && chunk->auth)) {
812                         /* We no longer do re-fragmentation.
813                          * Just fragment at the IP layer, if we
814                          * actually hit this condition
815                          */
816                         packet->ipfragok = 1;
817                         goto out;
818                 }
819
820                 /* Similarly, if this chunk was built before a PMTU
821                  * reduction, we have to fragment it at IP level now. So
822                  * if the packet already contains something, we need to
823                  * flush.
824                  */
825                 maxsize = pmtu - packet->overhead;
826                 if (packet->auth)
827                         maxsize -= SCTP_PAD4(packet->auth->skb->len);
828                 if (chunk_len > maxsize)
829                         retval = SCTP_XMIT_PMTU_FULL;
830
831                 /* It is also okay to fragment if the chunk we are
832                  * adding is a control chunk, but only if current packet
833                  * is not a GSO one otherwise it causes fragmentation of
834                  * a large frame. So in this case we allow the
835                  * fragmentation by forcing it to be in a new packet.
836                  */
837                 if (!sctp_chunk_is_data(chunk) && packet->has_data)
838                         retval = SCTP_XMIT_PMTU_FULL;
839
840                 if (psize + chunk_len > packet->max_size)
841                         /* Hit GSO/PMTU limit, gotta flush */
842                         retval = SCTP_XMIT_PMTU_FULL;
843
844                 if (!packet->transport->burst_limited &&
845                     psize + chunk_len > (packet->transport->cwnd >> 1))
846                         /* Do not allow a single GSO packet to use more
847                          * than half of cwnd.
848                          */
849                         retval = SCTP_XMIT_PMTU_FULL;
850
851                 if (packet->transport->burst_limited &&
852                     psize + chunk_len > (packet->transport->burst_limited >> 1))
853                         /* Do not allow a single GSO packet to use more
854                          * than half of original cwnd.
855                          */
856                         retval = SCTP_XMIT_PMTU_FULL;
857                 /* Otherwise it will fit in the GSO packet */
858         }
859
860 out:
861         return retval;
862 }