From 241b271952eb319622a6cc740a72abe41fc27ad6 Mon Sep 17 00:00:00 2001
From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Date: Sun, 11 Oct 2015 16:49:44 -0400
Subject: [PATCH] RDS-TCP: Reset tcp callbacks if re-using an outgoing socket
in rds_tcp_accept_one()
Consider the following "duelling syn" sequence between two peers A and B:
A B
SYN1 -->
<-- SYN2
SYN2ACK -->
Note that the SYN/ACK has already been sent out by TCP before
rds_tcp_accept_one() gets invoked as part of callbacks.
If the inet_addr(A) is numerically less than inet_addr(B),
the arbitration scheme in rds_tcp_accept_one() will prefer the
TCP connection triggered by SYN1, and will send a CLOSE for the
SYN2 (just after the SYN2ACK was sent).
Since B also follows the same arbitration scheme, it will send the SYN-ACK
for SYN1 that will set up a healthy ESTABLISHED connection on both sides.
B will also get a CLOSE for SYN2, which should result in the cleanup
of the TCP state machine for SYN2, but it should not trigger any
stale RDS-TCP callbacks (such as ->writespace, ->state_change etc),
that would disrupt the progress of the SYN2 based RDS-TCP connection.
Thus the arbitration scheme in rds_tcp_accept_one() should restore
rds_tcp callbacks for the winner before setting them up for the
new accept socket, and also make sure that conn->c_outgoing
is set to 0 so that we do not trigger any reconnect attempts on the
passive side of the tcp socket in the future, in conformance with
commit c82ac7e69efe ("net/rds: RDS-TCP: only initiate reconnect attempt
on outgoing TCP socket.")
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/rds/tcp_listen.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index 1d90240e5d82d..0936a4a32b476 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -125,6 +125,9 @@ int rds_tcp_accept_one(struct socket *sock)
new_sock = NULL;
ret = 0;
goto out;
+ } else if (rs_tcp->t_sock) {
+ rds_tcp_restore_callbacks(rs_tcp->t_sock, rs_tcp);
+ conn->c_outgoing = 0;
}
rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING);
--
2.49.0