Commit 8a0d19c5 authored Dec 05, 2015 by lucien Committed by David S. Miller Dec 06, 2015

sctp: start t5 timer only when peer rwnd is 0 and local state is SHUTDOWN_PENDING

when A sends a data to B, then A close() and enter into SHUTDOWN_PENDING
state, if B neither claim his rwnd is 0 nor send SACK for this data, A
will keep retransmitting this data until t5 timeout, Max.Retrans times
can't work anymore, which is bad.

if B's rwnd is not 0, it should send abort after Max.Retrans times, only
when B's rwnd == 0 and A's retransmitting beyonds Max.Retrans times, A
will start t5 timer, which is also commit f8d96052 ("sctp: Enforce
retransmission limit during shutdown") means, but it lacks the condition
peer rwnd == 0.

so fix it by adding a bit (zero_window_announced) in peer to record if
the last rwnd is 0. If it was, zero_window_announced will be set. and use
this bit to decide if start t5 timer when local.state is SHUTDOWN_PENDING.

Fixes: commit f8d96052 ("sctp: Enforce retransmission limit during shutdown")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8b570dc9

include/net/sctp/structs.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -1493,7 +1493,8 @@ struct sctp_association {
		* : SACK's are not delayed (see Section 6).
		*/
		__u8 sack_needed:1, /* Do we need to sack the peer? */
		sack_generation:1;
		sack_generation:1,
		zero_window_announced:1;
		__u32 sack_cnt;

		__u32 adaptation_ind; /* Adaptation Code point. */

net/sctp/outqueue.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1252,6 +1252,7 @@ int sctp_outq_sack(struct sctp_outq q, struct sctp_chunk chunk)
		*/

		sack_a_rwnd = ntohl(sack->a_rwnd);
		asoc->peer.zero_window_announced = !sack_a_rwnd;
		outstanding = q->outstanding_bytes;

		if (outstanding < sack_a_rwnd)

net/sctp/sm_statefuns.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -5412,7 +5412,8 @@ sctp_disposition_t sctp_sf_do_6_3_3_rtx(struct net *net,
		SCTP_INC_STATS(net, SCTP_MIB_T3_RTX_EXPIREDS);

		if (asoc->overall_error_count >= asoc->max_retrans) {
		if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING) {
		if (asoc->peer.zero_window_announced &&
		asoc->state == SCTP_STATE_SHUTDOWN_PENDING) {
		/*
		* We are here likely because the receiver had its rwnd
		* closed for a while and we have not been able to

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