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, see
24 * <http://www.gnu.org/licenses/>.
26 * Please send any bug reports or fixes you make to the
28 * lksctp developers <linux-sctp@vger.kernel.org>
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>
37 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
39 #include <linux/types.h>
40 #include <linux/kernel.h>
41 #include <linux/wait.h>
42 #include <linux/time.h>
44 #include <linux/ipv6.h>
45 #include <linux/init.h>
46 #include <linux/slab.h>
47 #include <net/inet_ecn.h>
50 #include <net/net_namespace.h>
52 #include <linux/socket.h> /* for sa_family_t */
55 #include <net/sctp/sctp.h>
56 #include <net/sctp/sm.h>
57 #include <net/sctp/checksum.h>
59 /* Forward declarations for private helpers. */
60 static sctp_xmit_t
__sctp_packet_append_chunk(struct sctp_packet
*packet
,
61 struct sctp_chunk
*chunk
);
62 static sctp_xmit_t
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 sctp_xmit_t
sctp_packet_will_fit(struct sctp_packet
*packet
,
67 struct sctp_chunk
*chunk
,
70 static void sctp_packet_reset(struct sctp_packet
*packet
)
72 packet
->size
= packet
->overhead
;
73 packet
->has_cookie_echo
= 0;
82 * This appears to be a followup set of initializations.
84 struct sctp_packet
*sctp_packet_config(struct sctp_packet
*packet
,
85 __u32 vtag
, int ecn_capable
)
87 struct sctp_transport
*tp
= packet
->transport
;
88 struct sctp_association
*asoc
= tp
->asoc
;
90 pr_debug("%s: packet:%p vtag:0x%x\n", __func__
, packet
, vtag
);
94 if (asoc
&& tp
->dst
) {
95 struct sock
*sk
= asoc
->base
.sk
;
98 if (__sk_dst_get(sk
) != tp
->dst
) {
100 sk_setup_caps(sk
, tp
->dst
);
103 if (sk_can_gso(sk
)) {
104 struct net_device
*dev
= tp
->dst
->dev
;
106 packet
->max_size
= dev
->gso_max_size
;
108 packet
->max_size
= asoc
->pathmtu
;
113 packet
->max_size
= tp
->pathmtu
;
116 if (ecn_capable
&& sctp_packet_empty(packet
)) {
117 struct sctp_chunk
*chunk
;
119 /* If there a is a prepend chunk stick it on the list before
120 * any other chunks get appended.
122 chunk
= sctp_get_ecne_prepend(asoc
);
124 sctp_packet_append_chunk(packet
, chunk
);
130 /* Initialize the packet structure. */
131 struct sctp_packet
*sctp_packet_init(struct sctp_packet
*packet
,
132 struct sctp_transport
*transport
,
133 __u16 sport
, __u16 dport
)
135 struct sctp_association
*asoc
= transport
->asoc
;
138 pr_debug("%s: packet:%p transport:%p\n", __func__
, packet
, transport
);
140 packet
->transport
= transport
;
141 packet
->source_port
= sport
;
142 packet
->destination_port
= dport
;
143 INIT_LIST_HEAD(&packet
->chunk_list
);
145 struct sctp_sock
*sp
= sctp_sk(asoc
->base
.sk
);
146 overhead
= sp
->pf
->af
->net_header_len
;
148 overhead
= sizeof(struct ipv6hdr
);
150 overhead
+= sizeof(struct sctphdr
);
151 packet
->overhead
= overhead
;
152 sctp_packet_reset(packet
);
159 void sctp_packet_free(struct sctp_packet
*packet
)
161 struct sctp_chunk
*chunk
, *tmp
;
163 pr_debug("%s: packet:%p\n", __func__
, packet
);
165 list_for_each_entry_safe(chunk
, tmp
, &packet
->chunk_list
, list
) {
166 list_del_init(&chunk
->list
);
167 sctp_chunk_free(chunk
);
171 /* This routine tries to append the chunk to the offered packet. If adding
172 * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
173 * is not present in the packet, it transmits the input packet.
174 * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
175 * as it can fit in the packet, but any more data that does not fit in this
176 * packet can be sent only after receiving the COOKIE_ACK.
178 sctp_xmit_t
sctp_packet_transmit_chunk(struct sctp_packet
*packet
,
179 struct sctp_chunk
*chunk
,
180 int one_packet
, gfp_t gfp
)
184 pr_debug("%s: packet:%p size:%Zu chunk:%p size:%d\n", __func__
,
185 packet
, packet
->size
, chunk
, chunk
->skb
? chunk
->skb
->len
: -1);
187 switch ((retval
= (sctp_packet_append_chunk(packet
, chunk
)))) {
188 case SCTP_XMIT_PMTU_FULL
:
189 if (!packet
->has_cookie_echo
) {
192 error
= sctp_packet_transmit(packet
, gfp
);
194 chunk
->skb
->sk
->sk_err
= -error
;
196 /* If we have an empty packet, then we can NOT ever
200 retval
= sctp_packet_append_chunk(packet
,
205 case SCTP_XMIT_RWND_FULL
:
207 case SCTP_XMIT_DELAY
:
214 /* Try to bundle an auth chunk into the packet. */
215 static sctp_xmit_t
sctp_packet_bundle_auth(struct sctp_packet
*pkt
,
216 struct sctp_chunk
*chunk
)
218 struct sctp_association
*asoc
= pkt
->transport
->asoc
;
219 struct sctp_chunk
*auth
;
220 sctp_xmit_t retval
= SCTP_XMIT_OK
;
222 /* if we don't have an association, we can't do authentication */
226 /* See if this is an auth chunk we are bundling or if
227 * auth is already bundled.
229 if (chunk
->chunk_hdr
->type
== SCTP_CID_AUTH
|| pkt
->has_auth
)
232 /* if the peer did not request this chunk to be authenticated,
238 auth
= sctp_make_auth(asoc
);
242 retval
= __sctp_packet_append_chunk(pkt
, auth
);
244 if (retval
!= SCTP_XMIT_OK
)
245 sctp_chunk_free(auth
);
250 /* Try to bundle a SACK with the packet. */
251 static sctp_xmit_t
sctp_packet_bundle_sack(struct sctp_packet
*pkt
,
252 struct sctp_chunk
*chunk
)
254 sctp_xmit_t retval
= SCTP_XMIT_OK
;
256 /* If sending DATA and haven't aleady bundled a SACK, try to
257 * bundle one in to the packet.
259 if (sctp_chunk_is_data(chunk
) && !pkt
->has_sack
&&
260 !pkt
->has_cookie_echo
) {
261 struct sctp_association
*asoc
;
262 struct timer_list
*timer
;
263 asoc
= pkt
->transport
->asoc
;
264 timer
= &asoc
->timers
[SCTP_EVENT_TIMEOUT_SACK
];
266 /* If the SACK timer is running, we have a pending SACK */
267 if (timer_pending(timer
)) {
268 struct sctp_chunk
*sack
;
270 if (pkt
->transport
->sack_generation
!=
271 pkt
->transport
->asoc
->peer
.sack_generation
)
274 asoc
->a_rwnd
= asoc
->rwnd
;
275 sack
= sctp_make_sack(asoc
);
277 retval
= __sctp_packet_append_chunk(pkt
, sack
);
278 if (retval
!= SCTP_XMIT_OK
) {
279 sctp_chunk_free(sack
);
282 asoc
->peer
.sack_needed
= 0;
283 if (del_timer(timer
))
284 sctp_association_put(asoc
);
293 /* Append a chunk to the offered packet reporting back any inability to do
296 static sctp_xmit_t
__sctp_packet_append_chunk(struct sctp_packet
*packet
,
297 struct sctp_chunk
*chunk
)
299 sctp_xmit_t retval
= SCTP_XMIT_OK
;
300 __u16 chunk_len
= SCTP_PAD4(ntohs(chunk
->chunk_hdr
->length
));
302 /* Check to see if this chunk will fit into the packet */
303 retval
= sctp_packet_will_fit(packet
, chunk
, chunk_len
);
304 if (retval
!= SCTP_XMIT_OK
)
307 /* We believe that this chunk is OK to add to the packet */
308 switch (chunk
->chunk_hdr
->type
) {
310 /* Account for the data being in the packet */
311 sctp_packet_append_data(packet
, chunk
);
312 /* Disallow SACK bundling after DATA. */
313 packet
->has_sack
= 1;
314 /* Disallow AUTH bundling after DATA */
315 packet
->has_auth
= 1;
316 /* Let it be knows that packet has DATA in it */
317 packet
->has_data
= 1;
318 /* timestamp the chunk for rtx purposes */
319 chunk
->sent_at
= jiffies
;
320 /* Mainly used for prsctp RTX policy */
323 case SCTP_CID_COOKIE_ECHO
:
324 packet
->has_cookie_echo
= 1;
328 packet
->has_sack
= 1;
330 chunk
->asoc
->stats
.osacks
++;
334 packet
->has_auth
= 1;
335 packet
->auth
= chunk
;
339 /* It is OK to send this chunk. */
340 list_add_tail(&chunk
->list
, &packet
->chunk_list
);
341 packet
->size
+= chunk_len
;
342 chunk
->transport
= packet
->transport
;
347 /* Append a chunk to the offered packet reporting back any inability to do
350 sctp_xmit_t
sctp_packet_append_chunk(struct sctp_packet
*packet
,
351 struct sctp_chunk
*chunk
)
353 sctp_xmit_t retval
= SCTP_XMIT_OK
;
355 pr_debug("%s: packet:%p chunk:%p\n", __func__
, packet
, chunk
);
357 /* Data chunks are special. Before seeing what else we can
358 * bundle into this packet, check to see if we are allowed to
361 if (sctp_chunk_is_data(chunk
)) {
362 retval
= sctp_packet_can_append_data(packet
, chunk
);
363 if (retval
!= SCTP_XMIT_OK
)
367 /* Try to bundle AUTH chunk */
368 retval
= sctp_packet_bundle_auth(packet
, chunk
);
369 if (retval
!= SCTP_XMIT_OK
)
372 /* Try to bundle SACK chunk */
373 retval
= sctp_packet_bundle_sack(packet
, chunk
);
374 if (retval
!= SCTP_XMIT_OK
)
377 retval
= __sctp_packet_append_chunk(packet
, chunk
);
383 static void sctp_packet_release_owner(struct sk_buff
*skb
)
388 static void sctp_packet_set_owner_w(struct sk_buff
*skb
, struct sock
*sk
)
392 skb
->destructor
= sctp_packet_release_owner
;
395 * The data chunks have already been accounted for in sctp_sendmsg(),
396 * therefore only reserve a single byte to keep socket around until
397 * the packet has been transmitted.
399 atomic_inc(&sk
->sk_wmem_alloc
);
402 static int sctp_packet_pack(struct sctp_packet
*packet
,
403 struct sk_buff
*head
, int gso
, gfp_t gfp
)
405 struct sctp_transport
*tp
= packet
->transport
;
406 struct sctp_auth_chunk
*auth
= NULL
;
407 struct sctp_chunk
*chunk
, *tmp
;
408 int pkt_count
= 0, pkt_size
;
409 struct sock
*sk
= head
->sk
;
410 struct sk_buff
*nskb
;
414 skb_shinfo(head
)->gso_type
= sk
->sk_gso_type
;
415 NAPI_GRO_CB(head
)->last
= head
;
418 pkt_size
= packet
->size
;
423 /* calculate the pkt_size and alloc nskb */
424 pkt_size
= packet
->overhead
;
425 list_for_each_entry_safe(chunk
, tmp
, &packet
->chunk_list
,
427 int padded
= SCTP_PAD4(chunk
->skb
->len
);
429 if (chunk
== packet
->auth
)
431 else if (auth_len
+ padded
+ packet
->overhead
>
434 else if (pkt_size
+ padded
> tp
->pathmtu
)
438 nskb
= alloc_skb(pkt_size
+ MAX_HEADER
, gfp
);
441 skb_reserve(nskb
, packet
->overhead
+ MAX_HEADER
);
444 /* merge chunks into nskb and append nskb into head list */
445 pkt_size
-= packet
->overhead
;
446 list_for_each_entry_safe(chunk
, tmp
, &packet
->chunk_list
, list
) {
449 list_del_init(&chunk
->list
);
450 if (sctp_chunk_is_data(chunk
)) {
451 if (!sctp_chunk_retransmitted(chunk
) &&
453 chunk
->rtt_in_progress
= 1;
458 padding
= SCTP_PAD4(chunk
->skb
->len
) - chunk
->skb
->len
;
460 memset(skb_put(chunk
->skb
, padding
), 0, padding
);
462 if (chunk
== packet
->auth
)
463 auth
= (struct sctp_auth_chunk
*)
464 skb_tail_pointer(nskb
);
466 memcpy(skb_put(nskb
, chunk
->skb
->len
), chunk
->skb
->data
,
469 pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
471 sctp_cname(SCTP_ST_CHUNK(chunk
->chunk_hdr
->type
)),
472 chunk
->has_tsn
? "TSN" : "No TSN",
473 chunk
->has_tsn
? ntohl(chunk
->subh
.data_hdr
->tsn
) : 0,
474 ntohs(chunk
->chunk_hdr
->length
), chunk
->skb
->len
,
475 chunk
->rtt_in_progress
);
477 pkt_size
-= SCTP_PAD4(chunk
->skb
->len
);
479 if (!sctp_chunk_is_data(chunk
) && chunk
!= packet
->auth
)
480 sctp_chunk_free(chunk
);
487 sctp_auth_calculate_hmac(tp
->asoc
, nskb
, auth
, gfp
);
488 /* free auth if no more chunks, or add it back */
489 if (list_empty(&packet
->chunk_list
))
490 sctp_chunk_free(packet
->auth
);
492 list_add(&packet
->auth
->list
,
493 &packet
->chunk_list
);
497 if (skb_gro_receive(&head
, nskb
)) {
501 if (WARN_ON_ONCE(skb_shinfo(head
)->gso_segs
>=
502 sk
->sk_gso_max_segs
))
507 } while (!list_empty(&packet
->chunk_list
));
510 memset(head
->cb
, 0, max(sizeof(struct inet_skb_parm
),
511 sizeof(struct inet6_skb_parm
)));
512 skb_shinfo(head
)->gso_segs
= pkt_count
;
513 skb_shinfo(head
)->gso_size
= GSO_BY_FRAGS
;
515 if (skb_dst(head
) != tp
->dst
) {
517 sk_setup_caps(sk
, tp
->dst
);
523 if (sctp_checksum_disable
)
526 if (!(skb_dst(head
)->dev
->features
& NETIF_F_SCTP_CRC
) ||
527 dst_xfrm(skb_dst(head
)) || packet
->ipfragok
) {
529 (struct sctphdr
*)skb_transport_header(head
);
531 sh
->checksum
= sctp_compute_cksum(head
, 0);
534 head
->ip_summed
= CHECKSUM_PARTIAL
;
535 head
->csum_start
= skb_transport_header(head
) - head
->head
;
536 head
->csum_offset
= offsetof(struct sctphdr
, checksum
);
542 /* All packets are sent to the network through this function from
545 * The return value is always 0 for now.
547 int sctp_packet_transmit(struct sctp_packet
*packet
, gfp_t gfp
)
549 struct sctp_transport
*tp
= packet
->transport
;
550 struct sctp_association
*asoc
= tp
->asoc
;
551 struct sctp_chunk
*chunk
, *tmp
;
552 int pkt_count
, gso
= 0;
553 struct dst_entry
*dst
;
554 struct sk_buff
*head
;
558 pr_debug("%s: packet:%p\n", __func__
, packet
);
559 if (list_empty(&packet
->chunk_list
))
561 chunk
= list_entry(packet
->chunk_list
.next
, struct sctp_chunk
, list
);
565 if (packet
->size
> tp
->pathmtu
&& !packet
->ipfragok
) {
566 if (!sk_can_gso(sk
)) {
567 pr_err_once("Trying to GSO but underlying device doesn't support it.");
574 head
= alloc_skb((gso
? packet
->overhead
: packet
->size
) +
578 skb_reserve(head
, packet
->overhead
+ MAX_HEADER
);
579 sctp_packet_set_owner_w(head
, sk
);
581 /* set sctp header */
582 sh
= (struct sctphdr
*)skb_push(head
, sizeof(struct sctphdr
));
583 skb_reset_transport_header(head
);
584 sh
->source
= htons(packet
->source_port
);
585 sh
->dest
= htons(packet
->destination_port
);
586 sh
->vtag
= htonl(packet
->vtag
);
589 /* update dst if in need */
590 if (!sctp_transport_dst_check(tp
)) {
591 sctp_transport_route(tp
, NULL
, sctp_sk(sk
));
592 if (asoc
&& asoc
->param_flags
& SPP_PMTUD_ENABLE
)
593 sctp_assoc_sync_pmtu(sk
, asoc
);
595 dst
= dst_clone(tp
->dst
);
597 IP_INC_STATS(sock_net(sk
), IPSTATS_MIB_OUTNOROUTES
);
601 skb_dst_set(head
, dst
);
604 pkt_count
= sctp_packet_pack(packet
, head
, gso
, gfp
);
609 pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head
->len
);
611 /* start autoclose timer */
612 if (packet
->has_data
&& sctp_state(asoc
, ESTABLISHED
) &&
613 asoc
->timeouts
[SCTP_EVENT_TIMEOUT_AUTOCLOSE
]) {
614 struct timer_list
*timer
=
615 &asoc
->timers
[SCTP_EVENT_TIMEOUT_AUTOCLOSE
];
616 unsigned long timeout
=
617 asoc
->timeouts
[SCTP_EVENT_TIMEOUT_AUTOCLOSE
];
619 if (!mod_timer(timer
, jiffies
+ timeout
))
620 sctp_association_hold(asoc
);
624 tp
->af_specific
->ecn_capable(sk
);
626 asoc
->stats
.opackets
+= pkt_count
;
627 if (asoc
->peer
.last_sent_to
!= tp
)
628 asoc
->peer
.last_sent_to
= tp
;
630 head
->ignore_df
= packet
->ipfragok
;
631 tp
->af_specific
->sctp_xmit(head
, tp
);
634 list_for_each_entry_safe(chunk
, tmp
, &packet
->chunk_list
, list
) {
635 list_del_init(&chunk
->list
);
636 if (!sctp_chunk_is_data(chunk
))
637 sctp_chunk_free(chunk
);
639 sctp_packet_reset(packet
);
643 /********************************************************************
644 * 2nd Level Abstractions
645 ********************************************************************/
647 /* This private function check to see if a chunk can be added */
648 static sctp_xmit_t
sctp_packet_can_append_data(struct sctp_packet
*packet
,
649 struct sctp_chunk
*chunk
)
651 size_t datasize
, rwnd
, inflight
, flight_size
;
652 struct sctp_transport
*transport
= packet
->transport
;
653 struct sctp_association
*asoc
= transport
->asoc
;
654 struct sctp_outq
*q
= &asoc
->outqueue
;
656 /* RFC 2960 6.1 Transmission of DATA Chunks
658 * A) At any given time, the data sender MUST NOT transmit new data to
659 * any destination transport address if its peer's rwnd indicates
660 * that the peer has no buffer space (i.e. rwnd is 0, see Section
661 * 6.2.1). However, regardless of the value of rwnd (including if it
662 * is 0), the data sender can always have one DATA chunk in flight to
663 * the receiver if allowed by cwnd (see rule B below). This rule
664 * allows the sender to probe for a change in rwnd that the sender
665 * missed due to the SACK having been lost in transit from the data
666 * receiver to the data sender.
669 rwnd
= asoc
->peer
.rwnd
;
670 inflight
= q
->outstanding_bytes
;
671 flight_size
= transport
->flight_size
;
673 datasize
= sctp_data_size(chunk
);
675 if (datasize
> rwnd
&& inflight
> 0)
676 /* We have (at least) one data chunk in flight,
677 * so we can't fall back to rule 6.1 B).
679 return SCTP_XMIT_RWND_FULL
;
681 /* RFC 2960 6.1 Transmission of DATA Chunks
683 * B) At any given time, the sender MUST NOT transmit new data
684 * to a given transport address if it has cwnd or more bytes
685 * of data outstanding to that transport address.
687 /* RFC 7.2.4 & the Implementers Guide 2.8.
690 * When a Fast Retransmit is being performed the sender SHOULD
691 * ignore the value of cwnd and SHOULD NOT delay retransmission.
693 if (chunk
->fast_retransmit
!= SCTP_NEED_FRTX
&&
694 flight_size
>= transport
->cwnd
)
695 return SCTP_XMIT_RWND_FULL
;
697 /* Nagle's algorithm to solve small-packet problem:
698 * Inhibit the sending of new chunks when new outgoing data arrives
699 * if any previously transmitted data on the connection remains
703 if (sctp_sk(asoc
->base
.sk
)->nodelay
)
707 if (!sctp_packet_empty(packet
))
708 /* Append to packet */
712 /* Nothing unacked */
715 if (!sctp_state(asoc
, ESTABLISHED
))
718 /* Check whether this chunk and all the rest of pending data will fit
719 * or delay in hopes of bundling a full sized packet.
721 if (chunk
->skb
->len
+ q
->out_qlen
>
722 transport
->pathmtu
- packet
->overhead
- sizeof(sctp_data_chunk_t
) - 4)
723 /* Enough data queued to fill a packet */
726 /* Don't delay large message writes that may have been fragmented */
727 if (!chunk
->msg
->can_delay
)
730 /* Defer until all data acked or packet full */
731 return SCTP_XMIT_DELAY
;
734 /* This private function does management things when adding DATA chunk */
735 static void sctp_packet_append_data(struct sctp_packet
*packet
,
736 struct sctp_chunk
*chunk
)
738 struct sctp_transport
*transport
= packet
->transport
;
739 size_t datasize
= sctp_data_size(chunk
);
740 struct sctp_association
*asoc
= transport
->asoc
;
741 u32 rwnd
= asoc
->peer
.rwnd
;
743 /* Keep track of how many bytes are in flight over this transport. */
744 transport
->flight_size
+= datasize
;
746 /* Keep track of how many bytes are in flight to the receiver. */
747 asoc
->outqueue
.outstanding_bytes
+= datasize
;
749 /* Update our view of the receiver's rwnd. */
755 asoc
->peer
.rwnd
= rwnd
;
756 sctp_chunk_assign_tsn(chunk
);
757 sctp_chunk_assign_ssn(chunk
);
760 static sctp_xmit_t
sctp_packet_will_fit(struct sctp_packet
*packet
,
761 struct sctp_chunk
*chunk
,
764 size_t psize
, pmtu
, maxsize
;
765 sctp_xmit_t retval
= SCTP_XMIT_OK
;
767 psize
= packet
->size
;
768 if (packet
->transport
->asoc
)
769 pmtu
= packet
->transport
->asoc
->pathmtu
;
771 pmtu
= packet
->transport
->pathmtu
;
773 /* Decide if we need to fragment or resubmit later. */
774 if (psize
+ chunk_len
> pmtu
) {
775 /* It's OK to fragment at IP level if any one of the following
777 * 1. The packet is empty (meaning this chunk is greater
779 * 2. The packet doesn't have any data in it yet and data
780 * requires authentication.
782 if (sctp_packet_empty(packet
) ||
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;
792 /* Similarly, if this chunk was built before a PMTU
793 * reduction, we have to fragment it at IP level now. So
794 * if the packet already contains something, we need to
797 maxsize
= pmtu
- packet
->overhead
;
799 maxsize
-= SCTP_PAD4(packet
->auth
->skb
->len
);
800 if (chunk_len
> maxsize
)
801 retval
= SCTP_XMIT_PMTU_FULL
;
803 /* It is also okay to fragment if the chunk we are
804 * adding is a control chunk, but only if current packet
805 * is not a GSO one otherwise it causes fragmentation of
806 * a large frame. So in this case we allow the
807 * fragmentation by forcing it to be in a new packet.
809 if (!sctp_chunk_is_data(chunk
) && packet
->has_data
)
810 retval
= SCTP_XMIT_PMTU_FULL
;
812 if (psize
+ chunk_len
> packet
->max_size
)
813 /* Hit GSO/PMTU limit, gotta flush */
814 retval
= SCTP_XMIT_PMTU_FULL
;
816 if (!packet
->transport
->burst_limited
&&
817 psize
+ chunk_len
> (packet
->transport
->cwnd
>> 1))
818 /* Do not allow a single GSO packet to use more
821 retval
= SCTP_XMIT_PMTU_FULL
;
823 if (packet
->transport
->burst_limited
&&
824 psize
+ chunk_len
> (packet
->transport
->burst_limited
>> 1))
825 /* Do not allow a single GSO packet to use more
826 * than half of original cwnd.
828 retval
= SCTP_XMIT_PMTU_FULL
;
829 /* Otherwise it will fit in the GSO packet */