[3.13.y.z extended stable] Patch "sctp: handle association restarts when the socket is closed." has been added to staging queue

Kamal Mostafa kamal at canonical.com
Fri Oct 31 20:53:25 UTC 2014

This is a note to let you know that I have just added a patch titled

    sctp: handle association restarts when the socket is closed.

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:


This patch is scheduled to be released in version

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

For more information about the 3.13.y.z tree, see



>From 27233e7eeef6a39ad7220de4ce712df4b517833f Mon Sep 17 00:00:00 2001
From: Vlad Yasevich <vyasevich at gmail.com>
Date: Fri, 3 Oct 2014 18:16:20 -0400
Subject: sctp: handle association restarts when the socket is closed.

[ Upstream commit bdf6fa52f01b941d4a80372d56de465bdbbd1d23 ]

Currently association restarts do not take into consideration the
state of the socket.  When a restart happens, the current assocation
simply transitions into established state.  This creates a condition
where a remote system, through a the restart procedure, may create a
local association that is no way reachable by user.  The conditions
to trigger this are as follows:
  1) Remote does not acknoledge some data causing data to remain
  2) Local application calls close() on the socket.  Since data
     is still outstanding, the association is placed in SHUTDOWN_PENDING
     state.  However, the socket is closed.
  3) The remote tries to create a new association, triggering a restart
     on the local system.  The association moves from SHUTDOWN_PENDING
     to ESTABLISHED.  At this point, it is no longer reachable by
     any socket on the local system.

This patch addresses the above situation by moving the newly ESTABLISHED
association into SHUTDOWN-SENT state and bundling a SHUTDOWN after
the COOKIE-ACK chunk.  This way, the restarted associate immidiately
enters the shutdown procedure and forces the termination of the
unreachable association.

Reported-by: David Laight <David.Laight at aculab.com>
Signed-off-by: Vlad Yasevich <vyasevich at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 include/net/sctp/command.h |  2 +-
 net/sctp/sm_statefuns.c    | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
index 832f219..c3f0cd9 100644
--- a/include/net/sctp/command.h
+++ b/include/net/sctp/command.h
@@ -116,7 +116,7 @@ typedef enum {
  * analysis of the state functions, but in reality just taken from
  * thin air in the hopes othat we don't trigger a kernel panic.

 typedef union {
 	__s32 i32;
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index cd0d5a2..4b549a3 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -1776,9 +1776,22 @@ static sctp_disposition_t sctp_sf_do_dupcook_a(struct net *net,
 	/* Update the content of current association. */
 	sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
 	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
-	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
-	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
+	if (sctp_state(asoc, SHUTDOWN_PENDING) &&
+	    (sctp_sstate(asoc->base.sk, CLOSING) ||
+	     sock_flag(asoc->base.sk, SOCK_DEAD))) {
+		/* if were currently in SHUTDOWN_PENDING, but the socket
+		 * has been closed by user, don't transition to ESTABLISHED.
+		 * Instead trigger SHUTDOWN bundled with COOKIE_ACK.
+		 */
+		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
+		return sctp_sf_do_9_2_start_shutdown(net, ep, asoc,
+						     SCTP_ST_CHUNK(0), NULL,
+						     commands);
+	} else {
+		sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
+		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
+	}


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