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.
6 * This file is part of the SCTP kernel implementation
8 * These functions handle output processing.
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)
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.
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.
27 * Please send any bug reports or fixes you make to the
29 * lksctp developers <linux-sctp@vger.kernel.org>
31 * Or submit a bug report through the following website:
32 * http://www.sf.net/projects/lksctp
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>
40 * Any bugs reported given to us we will try to fix... any fixes shared will
41 * be incorporated into the next SCTP release.
44 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
46 #include <linux/types.h>
47 #include <linux/kernel.h>
48 #include <linux/wait.h>
49 #include <linux/time.h>
51 #include <linux/ipv6.h>
52 #include <linux/init.h>
53 #include <linux/slab.h>
54 #include <net/inet_ecn.h>
57 #include <net/net_namespace.h>
59 #include <linux/socket.h> /* for sa_family_t */
62 #include <net/sctp/sctp.h>
63 #include <net/sctp/sm.h>
64 #include <net/sctp/checksum.h>
66 /* Forward declarations for private helpers. */
67 static sctp_xmit_t
__sctp_packet_append_chunk(struct sctp_packet
*packet
,
68 struct sctp_chunk
*chunk
);
69 static sctp_xmit_t
sctp_packet_can_append_data(struct sctp_packet
*packet
,
70 struct sctp_chunk
*chunk
);
71 static void sctp_packet_append_data(struct sctp_packet
*packet
,
72 struct sctp_chunk
*chunk
);
73 static sctp_xmit_t
sctp_packet_will_fit(struct sctp_packet
*packet
,
74 struct sctp_chunk
*chunk
,
77 static void sctp_packet_reset(struct sctp_packet
*packet
)
79 packet
->size
= packet
->overhead
;
80 packet
->has_cookie_echo
= 0;
89 * This appears to be a followup set of initializations.
91 struct sctp_packet
*sctp_packet_config(struct sctp_packet
*packet
,
92 __u32 vtag
, int ecn_capable
)
94 struct sctp_chunk
*chunk
= NULL
;
96 pr_debug("%s: packet:%p vtag:0x%x\n", __func__
, packet
, vtag
);
100 if (ecn_capable
&& sctp_packet_empty(packet
)) {
101 chunk
= sctp_get_ecne_prepend(packet
->transport
->asoc
);
103 /* If there a is a prepend chunk stick it on the list before
104 * any other chunks get appended.
107 sctp_packet_append_chunk(packet
, chunk
);
113 /* Initialize the packet structure. */
114 struct sctp_packet
*sctp_packet_init(struct sctp_packet
*packet
,
115 struct sctp_transport
*transport
,
116 __u16 sport
, __u16 dport
)
118 struct sctp_association
*asoc
= transport
->asoc
;
121 pr_debug("%s: packet:%p transport:%p\n", __func__
, packet
, transport
);
123 packet
->transport
= transport
;
124 packet
->source_port
= sport
;
125 packet
->destination_port
= dport
;
126 INIT_LIST_HEAD(&packet
->chunk_list
);
128 struct sctp_sock
*sp
= sctp_sk(asoc
->base
.sk
);
129 overhead
= sp
->pf
->af
->net_header_len
;
131 overhead
= sizeof(struct ipv6hdr
);
133 overhead
+= sizeof(struct sctphdr
);
134 packet
->overhead
= overhead
;
135 sctp_packet_reset(packet
);
142 void sctp_packet_free(struct sctp_packet
*packet
)
144 struct sctp_chunk
*chunk
, *tmp
;
146 pr_debug("%s: packet:%p\n", __func__
, packet
);
148 list_for_each_entry_safe(chunk
, tmp
, &packet
->chunk_list
, list
) {
149 list_del_init(&chunk
->list
);
150 sctp_chunk_free(chunk
);
154 /* This routine tries to append the chunk to the offered packet. If adding
155 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
156 * is not present in the packet, it transmits the input packet.
157 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
158 * as it can fit in the packet, but any more data that does not fit in this
159 * packet can be sent only after receiving the COOKIE_ACK.
161 sctp_xmit_t
sctp_packet_transmit_chunk(struct sctp_packet
*packet
,
162 struct sctp_chunk
*chunk
,
168 pr_debug("%s: packet:%p chunk:%p\n", __func__
, packet
, chunk
);
170 switch ((retval
= (sctp_packet_append_chunk(packet
, chunk
)))) {
171 case SCTP_XMIT_PMTU_FULL
:
172 if (!packet
->has_cookie_echo
) {
173 error
= sctp_packet_transmit(packet
);
175 chunk
->skb
->sk
->sk_err
= -error
;
177 /* If we have an empty packet, then we can NOT ever
181 retval
= sctp_packet_append_chunk(packet
,
186 case SCTP_XMIT_RWND_FULL
:
188 case SCTP_XMIT_NAGLE_DELAY
:
195 /* Try to bundle an auth chunk into the packet. */
196 static sctp_xmit_t
sctp_packet_bundle_auth(struct sctp_packet
*pkt
,
197 struct sctp_chunk
*chunk
)
199 struct sctp_association
*asoc
= pkt
->transport
->asoc
;
200 struct sctp_chunk
*auth
;
201 sctp_xmit_t retval
= SCTP_XMIT_OK
;
203 /* if we don't have an association, we can't do authentication */
207 /* See if this is an auth chunk we are bundling or if
208 * auth is already bundled.
210 if (chunk
->chunk_hdr
->type
== SCTP_CID_AUTH
|| pkt
->has_auth
)
213 /* if the peer did not request this chunk to be authenticated,
219 auth
= sctp_make_auth(asoc
);
223 retval
= __sctp_packet_append_chunk(pkt
, auth
);
225 if (retval
!= SCTP_XMIT_OK
)
226 sctp_chunk_free(auth
);
231 /* Try to bundle a SACK with the packet. */
232 static sctp_xmit_t
sctp_packet_bundle_sack(struct sctp_packet
*pkt
,
233 struct sctp_chunk
*chunk
)
235 sctp_xmit_t retval
= SCTP_XMIT_OK
;
237 /* If sending DATA and haven't aleady bundled a SACK, try to
238 * bundle one in to the packet.
240 if (sctp_chunk_is_data(chunk
) && !pkt
->has_sack
&&
241 !pkt
->has_cookie_echo
) {
242 struct sctp_association
*asoc
;
243 struct timer_list
*timer
;
244 asoc
= pkt
->transport
->asoc
;
245 timer
= &asoc
->timers
[SCTP_EVENT_TIMEOUT_SACK
];
247 /* If the SACK timer is running, we have a pending SACK */
248 if (timer_pending(timer
)) {
249 struct sctp_chunk
*sack
;
251 if (pkt
->transport
->sack_generation
!=
252 pkt
->transport
->asoc
->peer
.sack_generation
)
255 asoc
->a_rwnd
= asoc
->rwnd
;
256 sack
= sctp_make_sack(asoc
);
258 retval
= __sctp_packet_append_chunk(pkt
, sack
);
259 if (retval
!= SCTP_XMIT_OK
) {
260 sctp_chunk_free(sack
);
263 asoc
->peer
.sack_needed
= 0;
264 if (del_timer(timer
))
265 sctp_association_put(asoc
);
274 /* Append a chunk to the offered packet reporting back any inability to do
277 static sctp_xmit_t
__sctp_packet_append_chunk(struct sctp_packet
*packet
,
278 struct sctp_chunk
*chunk
)
280 sctp_xmit_t retval
= SCTP_XMIT_OK
;
281 __u16 chunk_len
= WORD_ROUND(ntohs(chunk
->chunk_hdr
->length
));
283 /* Check to see if this chunk will fit into the packet */
284 retval
= sctp_packet_will_fit(packet
, chunk
, chunk_len
);
285 if (retval
!= SCTP_XMIT_OK
)
288 /* We believe that this chunk is OK to add to the packet */
289 switch (chunk
->chunk_hdr
->type
) {
291 /* Account for the data being in the packet */
292 sctp_packet_append_data(packet
, chunk
);
293 /* Disallow SACK bundling after DATA. */
294 packet
->has_sack
= 1;
295 /* Disallow AUTH bundling after DATA */
296 packet
->has_auth
= 1;
297 /* Let it be knows that packet has DATA in it */
298 packet
->has_data
= 1;
299 /* timestamp the chunk for rtx purposes */
300 chunk
->sent_at
= jiffies
;
302 case SCTP_CID_COOKIE_ECHO
:
303 packet
->has_cookie_echo
= 1;
307 packet
->has_sack
= 1;
309 chunk
->asoc
->stats
.osacks
++;
313 packet
->has_auth
= 1;
314 packet
->auth
= chunk
;
318 /* It is OK to send this chunk. */
319 list_add_tail(&chunk
->list
, &packet
->chunk_list
);
320 packet
->size
+= chunk_len
;
321 chunk
->transport
= packet
->transport
;
326 /* Append a chunk to the offered packet reporting back any inability to do
329 sctp_xmit_t
sctp_packet_append_chunk(struct sctp_packet
*packet
,
330 struct sctp_chunk
*chunk
)
332 sctp_xmit_t retval
= SCTP_XMIT_OK
;
334 pr_debug("%s: packet:%p chunk:%p\n", __func__
, packet
, chunk
);
336 /* Data chunks are special. Before seeing what else we can
337 * bundle into this packet, check to see if we are allowed to
340 if (sctp_chunk_is_data(chunk
)) {
341 retval
= sctp_packet_can_append_data(packet
, chunk
);
342 if (retval
!= SCTP_XMIT_OK
)
346 /* Try to bundle AUTH chunk */
347 retval
= sctp_packet_bundle_auth(packet
, chunk
);
348 if (retval
!= SCTP_XMIT_OK
)
351 /* Try to bundle SACK chunk */
352 retval
= sctp_packet_bundle_sack(packet
, chunk
);
353 if (retval
!= SCTP_XMIT_OK
)
356 retval
= __sctp_packet_append_chunk(packet
, chunk
);
362 static void sctp_packet_release_owner(struct sk_buff
*skb
)
367 static void sctp_packet_set_owner_w(struct sk_buff
*skb
, struct sock
*sk
)
371 skb
->destructor
= sctp_packet_release_owner
;
374 * The data chunks have already been accounted for in sctp_sendmsg(),
375 * therefore only reserve a single byte to keep socket around until
376 * the packet has been transmitted.
378 atomic_inc(&sk
->sk_wmem_alloc
);
381 /* All packets are sent to the network through this function from
384 * The return value is a normal kernel error return value.
386 int sctp_packet_transmit(struct sctp_packet
*packet
)
388 struct sctp_transport
*tp
= packet
->transport
;
389 struct sctp_association
*asoc
= tp
->asoc
;
391 struct sk_buff
*nskb
;
392 struct sctp_chunk
*chunk
, *tmp
;
395 int padding
; /* How much padding do we need? */
397 struct dst_entry
*dst
= tp
->dst
;
398 unsigned char *auth
= NULL
; /* pointer to auth in skb data */
399 __u32 cksum_buf_len
= sizeof(struct sctphdr
);
401 pr_debug("%s: packet:%p\n", __func__
, packet
);
403 /* Do NOT generate a chunkless packet. */
404 if (list_empty(&packet
->chunk_list
))
407 /* Set up convenience variables... */
408 chunk
= list_entry(packet
->chunk_list
.next
, struct sctp_chunk
, list
);
411 /* Allocate the new skb. */
412 nskb
= alloc_skb(packet
->size
+ LL_MAX_HEADER
, GFP_ATOMIC
);
416 /* Make sure the outbound skb has enough header room reserved. */
417 skb_reserve(nskb
, packet
->overhead
+ LL_MAX_HEADER
);
419 /* Set the owning socket so that we know where to get the
420 * destination IP address.
422 sctp_packet_set_owner_w(nskb
, sk
);
424 if (!sctp_transport_dst_check(tp
)) {
425 sctp_transport_route(tp
, NULL
, sctp_sk(sk
));
426 if (asoc
&& (asoc
->param_flags
& SPP_PMTUD_ENABLE
)) {
427 sctp_assoc_sync_pmtu(sk
, asoc
);
430 dst
= dst_clone(tp
->dst
);
431 skb_dst_set(nskb
, dst
);
435 /* Build the SCTP header. */
436 sh
= (struct sctphdr
*)skb_push(nskb
, sizeof(struct sctphdr
));
437 skb_reset_transport_header(nskb
);
438 sh
->source
= htons(packet
->source_port
);
439 sh
->dest
= htons(packet
->destination_port
);
441 /* From 6.8 Adler-32 Checksum Calculation:
442 * After the packet is constructed (containing the SCTP common
443 * header and one or more control or DATA chunks), the
446 * 1) Fill in the proper Verification Tag in the SCTP common
447 * header and initialize the checksum field to 0's.
449 sh
->vtag
= htonl(packet
->vtag
);
455 * An endpoint bundles chunks by simply including multiple
456 * chunks in one outbound SCTP packet. ...
460 * 3.2 Chunk Field Descriptions
462 * The total length of a chunk (including Type, Length and
463 * Value fields) MUST be a multiple of 4 bytes. If the length
464 * of the chunk is not a multiple of 4 bytes, the sender MUST
465 * pad the chunk with all zero bytes and this padding is not
466 * included in the chunk length field. The sender should
467 * never pad with more than 3 bytes.
469 * [This whole comment explains WORD_ROUND() below.]
472 pr_debug("***sctp_transmit_packet***\n");
474 list_for_each_entry_safe(chunk
, tmp
, &packet
->chunk_list
, list
) {
475 list_del_init(&chunk
->list
);
476 if (sctp_chunk_is_data(chunk
)) {
477 /* 6.3.1 C4) When data is in flight and when allowed
478 * by rule C5, a new RTT measurement MUST be made each
479 * round trip. Furthermore, new RTT measurements
480 * SHOULD be made no more than once per round-trip
481 * for a given destination transport address.
484 if (!tp
->rto_pending
) {
485 chunk
->rtt_in_progress
= 1;
491 padding
= WORD_ROUND(chunk
->skb
->len
) - chunk
->skb
->len
;
493 memset(skb_put(chunk
->skb
, padding
), 0, padding
);
495 /* if this is the auth chunk that we are adding,
496 * store pointer where it will be added and put
497 * the auth into the packet.
499 if (chunk
== packet
->auth
)
500 auth
= skb_tail_pointer(nskb
);
502 cksum_buf_len
+= chunk
->skb
->len
;
503 memcpy(skb_put(nskb
, chunk
->skb
->len
),
504 chunk
->skb
->data
, chunk
->skb
->len
);
506 pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, "
507 "rtt_in_progress:%d\n", chunk
,
508 sctp_cname(SCTP_ST_CHUNK(chunk
->chunk_hdr
->type
)),
509 chunk
->has_tsn
? "TSN" : "No TSN",
510 chunk
->has_tsn
? ntohl(chunk
->subh
.data_hdr
->tsn
) : 0,
511 ntohs(chunk
->chunk_hdr
->length
), chunk
->skb
->len
,
512 chunk
->rtt_in_progress
);
515 * If this is a control chunk, this is our last
516 * reference. Free data chunks after they've been
517 * acknowledged or have failed.
519 if (!sctp_chunk_is_data(chunk
))
520 sctp_chunk_free(chunk
);
523 /* SCTP-AUTH, Section 6.2
524 * The sender MUST calculate the MAC as described in RFC2104 [2]
525 * using the hash function H as described by the MAC Identifier and
526 * the shared association key K based on the endpoint pair shared key
527 * described by the shared key identifier. The 'data' used for the
528 * computation of the AUTH-chunk is given by the AUTH chunk with its
529 * HMAC field set to zero (as shown in Figure 6) followed by all
530 * chunks that are placed after the AUTH chunk in the SCTP packet.
533 sctp_auth_calculate_hmac(asoc
, nskb
,
534 (struct sctp_auth_chunk
*)auth
,
537 /* 2) Calculate the Adler-32 checksum of the whole packet,
538 * including the SCTP common header and all the
541 * Note: Adler-32 is no longer applicable, as has been replaced
542 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
544 if (!sctp_checksum_disable
) {
545 if (!(dst
->dev
->features
& NETIF_F_SCTP_CSUM
)) {
546 __u32 crc32
= sctp_start_cksum((__u8
*)sh
, cksum_buf_len
);
548 /* 3) Put the resultant value into the checksum field in the
549 * common header, and leave the rest of the bits unchanged.
551 sh
->checksum
= sctp_end_cksum(crc32
);
553 /* no need to seed pseudo checksum for SCTP */
554 nskb
->ip_summed
= CHECKSUM_PARTIAL
;
555 nskb
->csum_start
= (skb_transport_header(nskb
) -
557 nskb
->csum_offset
= offsetof(struct sctphdr
, checksum
);
561 /* IP layer ECN support
563 * "The ECN-Capable Transport (ECT) bit would be set by the
564 * data sender to indicate that the end-points of the
565 * transport protocol are ECN-capable."
567 * Now setting the ECT bit all the time, as it should not cause
568 * any problems protocol-wise even if our peer ignores it.
570 * Note: The works for IPv6 layer checks this bit too later
571 * in transmission. See IP6_ECN_flow_xmit().
573 (*tp
->af_specific
->ecn_capable
)(nskb
->sk
);
575 /* Set up the IP options. */
576 /* BUG: not implemented
577 * For v4 this all lives somewhere in sk->sk_opt...
580 /* Dump that on IP! */
582 asoc
->stats
.opackets
++;
583 if (asoc
->peer
.last_sent_to
!= tp
)
584 /* Considering the multiple CPU scenario, this is a
585 * "correcter" place for last_sent_to. --xguo
587 asoc
->peer
.last_sent_to
= tp
;
591 struct timer_list
*timer
;
592 unsigned long timeout
;
594 /* Restart the AUTOCLOSE timer when sending data. */
595 if (sctp_state(asoc
, ESTABLISHED
) && asoc
->autoclose
) {
596 timer
= &asoc
->timers
[SCTP_EVENT_TIMEOUT_AUTOCLOSE
];
597 timeout
= asoc
->timeouts
[SCTP_EVENT_TIMEOUT_AUTOCLOSE
];
599 if (!mod_timer(timer
, jiffies
+ timeout
))
600 sctp_association_hold(asoc
);
604 pr_debug("***sctp_transmit_packet*** skb->len:%d\n", nskb
->len
);
606 nskb
->local_df
= packet
->ipfragok
;
607 (*tp
->af_specific
->sctp_xmit
)(nskb
, tp
);
610 sctp_packet_reset(packet
);
614 IP_INC_STATS_BH(sock_net(asoc
->base
.sk
), IPSTATS_MIB_OUTNOROUTES
);
616 /* FIXME: Returning the 'err' will effect all the associations
617 * associated with a socket, although only one of the paths of the
618 * association is unreachable.
619 * The real failure of a transport or association can be passed on
620 * to the user via notifications. So setting this error may not be
623 /* err = -EHOSTUNREACH; */
625 /* Control chunks are unreliable so just drop them. DATA chunks
626 * will get resent or dropped later.
629 list_for_each_entry_safe(chunk
, tmp
, &packet
->chunk_list
, list
) {
630 list_del_init(&chunk
->list
);
631 if (!sctp_chunk_is_data(chunk
))
632 sctp_chunk_free(chunk
);
640 /********************************************************************
641 * 2nd Level Abstractions
642 ********************************************************************/
644 /* This private function check to see if a chunk can be added */
645 static sctp_xmit_t
sctp_packet_can_append_data(struct sctp_packet
*packet
,
646 struct sctp_chunk
*chunk
)
648 sctp_xmit_t retval
= SCTP_XMIT_OK
;
649 size_t datasize
, rwnd
, inflight
, flight_size
;
650 struct sctp_transport
*transport
= packet
->transport
;
651 struct sctp_association
*asoc
= transport
->asoc
;
652 struct sctp_outq
*q
= &asoc
->outqueue
;
654 /* RFC 2960 6.1 Transmission of DATA Chunks
656 * A) At any given time, the data sender MUST NOT transmit new data to
657 * any destination transport address if its peer's rwnd indicates
658 * that the peer has no buffer space (i.e. rwnd is 0, see Section
659 * 6.2.1). However, regardless of the value of rwnd (including if it
660 * is 0), the data sender can always have one DATA chunk in flight to
661 * the receiver if allowed by cwnd (see rule B below). This rule
662 * allows the sender to probe for a change in rwnd that the sender
663 * missed due to the SACK having been lost in transit from the data
664 * receiver to the data sender.
667 rwnd
= asoc
->peer
.rwnd
;
668 inflight
= q
->outstanding_bytes
;
669 flight_size
= transport
->flight_size
;
671 datasize
= sctp_data_size(chunk
);
673 if (datasize
> rwnd
) {
675 /* We have (at least) one data chunk in flight,
676 * so we can't fall back to rule 6.1 B).
678 retval
= SCTP_XMIT_RWND_FULL
;
683 /* RFC 2960 6.1 Transmission of DATA Chunks
685 * B) At any given time, the sender MUST NOT transmit new data
686 * to a given transport address if it has cwnd or more bytes
687 * of data outstanding to that transport address.
689 /* RFC 7.2.4 & the Implementers Guide 2.8.
692 * When a Fast Retransmit is being performed the sender SHOULD
693 * ignore the value of cwnd and SHOULD NOT delay retransmission.
695 if (chunk
->fast_retransmit
!= SCTP_NEED_FRTX
)
696 if (flight_size
>= transport
->cwnd
) {
697 retval
= SCTP_XMIT_RWND_FULL
;
701 /* Nagle's algorithm to solve small-packet problem:
702 * Inhibit the sending of new chunks when new outgoing data arrives
703 * if any previously transmitted data on the connection remains
706 if (!sctp_sk(asoc
->base
.sk
)->nodelay
&& sctp_packet_empty(packet
) &&
707 inflight
&& sctp_state(asoc
, ESTABLISHED
)) {
708 unsigned int max
= transport
->pathmtu
- packet
->overhead
;
709 unsigned int len
= chunk
->skb
->len
+ q
->out_qlen
;
711 /* Check whether this chunk and all the rest of pending
712 * data will fit or delay in hopes of bundling a full
714 * Don't delay large message writes that may have been
715 * fragmeneted into small peices.
717 if ((len
< max
) && chunk
->msg
->can_delay
) {
718 retval
= SCTP_XMIT_NAGLE_DELAY
;
727 /* This private function does management things when adding DATA chunk */
728 static void sctp_packet_append_data(struct sctp_packet
*packet
,
729 struct sctp_chunk
*chunk
)
731 struct sctp_transport
*transport
= packet
->transport
;
732 size_t datasize
= sctp_data_size(chunk
);
733 struct sctp_association
*asoc
= transport
->asoc
;
734 u32 rwnd
= asoc
->peer
.rwnd
;
736 /* Keep track of how many bytes are in flight over this transport. */
737 transport
->flight_size
+= datasize
;
739 /* Keep track of how many bytes are in flight to the receiver. */
740 asoc
->outqueue
.outstanding_bytes
+= datasize
;
742 /* Update our view of the receiver's rwnd. */
748 asoc
->peer
.rwnd
= rwnd
;
749 /* Has been accepted for transmission. */
750 if (!asoc
->peer
.prsctp_capable
)
751 chunk
->msg
->can_abandon
= 0;
752 sctp_chunk_assign_tsn(chunk
);
753 sctp_chunk_assign_ssn(chunk
);
756 static sctp_xmit_t
sctp_packet_will_fit(struct sctp_packet
*packet
,
757 struct sctp_chunk
*chunk
,
763 sctp_xmit_t retval
= SCTP_XMIT_OK
;
765 psize
= packet
->size
;
766 pmtu
= ((packet
->transport
->asoc
) ?
767 (packet
->transport
->asoc
->pathmtu
) :
768 (packet
->transport
->pathmtu
));
770 too_big
= (psize
+ chunk_len
> pmtu
);
772 /* Decide if we need to fragment or resubmit later. */
774 /* It's OK to fragmet at IP level if any one of the following
776 * 1. The packet is empty (meaning this chunk is greater
778 * 2. The chunk we are adding is a control chunk
779 * 3. The packet doesn't have any data in it yet and data
780 * requires authentication.
782 if (sctp_packet_empty(packet
) || !sctp_chunk_is_data(chunk
) ||
783 (!packet
->has_data
&& chunk
->auth
)) {
784 /* We no longer do re-fragmentation.
785 * Just fragment at the IP layer, if we
786 * actually hit this condition
788 packet
->ipfragok
= 1;
790 retval
= SCTP_XMIT_PMTU_FULL
;