net/rds: RDS-TCP: Always create a new rds_sock for an incoming connection.

When running RDS over TCP, the active (client) side connects to the
listening ("passive") side at the RDS_TCP_PORT.  After the connection
is established, if the client side reboots (potentially without even
sending a FIN) the server still has a TCP socket in the esablished
state.  If the server-side now gets a new SYN comes from the client
with a different client port, TCP will create a new socket-pair, but
the RDS layer will incorrectly pull up the old rds_connection (which
is still associated with the stale t_sock and RDS socket state).

This patch corrects this behavior by having rds_tcp_accept_one()
always create a new connection for an incoming TCP SYN.
The rds and tcp state associated with the old socket-pair is cleaned
up via the rds_tcp_state_change() callback which would typically be
invoked in most cases when the client-TCP sends a FIN on TCP restart,
triggering a transition to CLOSE_WAIT state. In the rarer event of client
death without a FIN, TCP_KEEPALIVE probes on the socket will detect
the stale socket, and the TCP transition to CLOSE state will trigger
the RDS state cleanup.

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 14f041398ca1..60f0cd6ed15f 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -126,7 +126,10 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,
 	struct rds_transport *loop_trans;
 	unsigned long flags;
 	int ret;
+	struct rds_transport *otrans = trans;
 
+	if (!is_outgoing && otrans->t_type == RDS_TRANS_TCP)
+		goto new_conn;
 	rcu_read_lock();
 	conn = rds_conn_lookup(head, laddr, faddr, trans);
 	if (conn && conn->c_loopback && conn->c_trans != &rds_loop_transport &&
@@ -142,6 +145,7 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,
 	if (conn)
 		goto out;
 
+new_conn:
 	conn = kmem_cache_zalloc(rds_conn_slab, gfp);
 	if (!conn) {
 		conn = ERR_PTR(-ENOMEM);