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[4.2.y-ckt,stable] Patch "sctp: start t5 timer only when peer rwnd is 0 and local state is SHUTDOWN_PENDING" has been added to the 4.2.y-ckt tree

Message ID 1452902279-30233-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Jan. 15, 2016, 11:57 p.m. UTC 
This is a note to let you know that I have just added a patch titled

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

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

From abd1d0cd108b5acf514d707b76fe30bdf5feb43d Mon Sep 17 00:00:00 2001
From: lucien <lucien.xin@gmail.com>
Date: Sat, 5 Dec 2015 15:35:36 +0800
Subject: sctp: start t5 timer only when peer rwnd is 0 and local state is
 SHUTDOWN_PENDING

commit 8a0d19c5ed417c78d03f4e0fa7215e58c40896d8 upstream.

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 f8d960524328 ("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 f8d960524328 ("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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 include/net/sctp/structs.h | 3 ++-
 net/sctp/outqueue.c        | 1 +
 net/sctp/sm_statefuns.c    | 3 ++-
 3 files changed, 5 insertions(+), 2 deletions(-)

--
1.9.1
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Patch

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 7bbb710..eea9bde 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -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. */
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 7e8f0a1..8d88823 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1251,6 +1251,7 @@  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)
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 3ee27b7..3809a74 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -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