From 1789b2c077f6d6c82b04cfe49a0fec020dc42488 Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Wed, 8 Apr 2015 12:33:46 -0400 Subject: [PATCH] RDS: only use passive connections when addresses match Passive connections were added for the case where one loopback IB connection between identical addresses needs another connection to store the second QP. Unfortunately, they were also created in the case where the addesses differ and we already have both QPs. This lead to a message reordering bug. - two different IB interfaces and addresses on a machine: A B - traffic is sent from A to B - connection from A-B is created, connect request sent - listening accepts connect request, B-A is created - traffic flows, next_rx is incremented - unacked messages exist on the retrans list - connection A-B is shut down, new connect request sent - listen sees existing loopback B-A, creates new passive B-A - retrans messages are sent and delivered because of 0 next_rx The problem is that the second connection request saw the previously existing parent connection. Instead of using it, and using the existing next_rx_seq state for the traffic between those IPs, it mistakenly thought that it had to create a passive connection. We fix this by only using passive connections in the special case where laddr and faddr match. In this case we'll only ever have one parent sending connection requests and one passive connection created as the listening path sees the existing parent connection which initiated the request. Original patch by Zach Brown Signed-off-by: Sowmini Varadhan Signed-off-by: David S. Miller --- net/rds/connection.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index 378c3a6acf84..7952a5b1b4c4 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -130,7 +130,7 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr, rcu_read_lock(); conn = rds_conn_lookup(head, laddr, faddr, trans); if (conn && conn->c_loopback && conn->c_trans != &rds_loop_transport && - !is_outgoing) { + laddr == faddr && !is_outgoing) { /* This is a looped back IB connection, and we're * called by the code handling the incoming connect. * We need a second connection object into which we -- 2.20.1