netdev - [PATCH] net: sctp: bug-fixing: retran_path not set properly after transports recovering (v3)

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Message-Id: <1384387106-8105-1-git-send-email-changxiangzhong@gmail.com>
Date:	Thu, 14 Nov 2013 00:58:26 +0100
From:	Chang Xiangzhong <changxiangzhong@...il.com>
To:	vyasevich@...il.com
Cc:	nhorman@...driver.com, davem@...emloft.net,
	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	Chang Xiangzhong <changxiangzhong@...il.com>
Subject: [PATCH] net: sctp: bug-fixing: retran_path not set properly after transports recovering (v3)

When a transport recovers due to the new coming sack, SCTP should
iterate all of its transport_list to locate the __two__ most recently used
transport and set to active_path and retran_path respectively. The exising
code does not find the two properly - In case of the following list:

[most-recent] -> [2nd-most-recent] -> ...

Both active_path and retran_path would be set to the 1st element.

The bug happens when:
1) multi-homing
2) failure/partial_failure transport recovers
Both active_path and retran_path would be set to the same most-recent one, in
other words, retran_path would not take its role - an end user might not even
notice this issue.

Signed-off-by: Chang Xiangzhong <changxiangzhong@...il.com>
---
 net/sctp/associola.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index ab67efc..8f26276 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -913,8 +913,8 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
 		if (!first || t->last_time_heard > first->last_time_heard) {
 			second = first;
 			first = t;
-		}
-		if (!second || t->last_time_heard > second->last_time_heard)
+		} else if (!second ||
+			   t->last_time_heard > second->last_time_heard)
 			second = t;
 	}
 
@@ -935,6 +935,8 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
 		first = asoc->peer.primary_path;
 	}
 
+	if (!second)
+		second = first;
 	/* If we failed to find a usable transport, just camp on the
 	 * primary, even if it is inactive.
 	 */
-- 
1.7.9.5

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