Commit f711a6ae authored by Sowmini Varadhan's avatar Sowmini Varadhan Committed by David S. Miller
Browse files

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: default avatarSowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e16e888b

net/rds/connection.c

+4 −0
Original line number Diff line number Diff line
@@ -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);

net/rds/tcp_connect.c

+1 −0
Original line number Diff line number Diff line
@@ -62,6 +62,7 @@ void rds_tcp_state_change(struct sock *sk) 
		case TCP_ESTABLISHED:

			rds_connect_complete(conn);

			break;

		case TCP_CLOSE_WAIT:

		case TCP_CLOSE:

			rds_conn_drop(conn);

		default:

net/rds/tcp_listen.c

+46 −0
Original line number Diff line number Diff line
@@ -45,12 +45,45 @@ static void rds_tcp_accept_worker(struct work_struct *work); 
static DECLARE_WORK(rds_tcp_listen_work, rds_tcp_accept_worker);

static struct socket *rds_tcp_listen_sock;



static int rds_tcp_keepalive(struct socket *sock)

{

	/* values below based on xs_udp_default_timeout */

	int keepidle = 5; /* send a probe 'keepidle' secs after last data */

	int keepcnt = 5; /* number of unack'ed probes before declaring dead */

	int keepalive = 1;

	int ret = 0;



	ret = kernel_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,

				(char *)&keepalive, sizeof(keepalive));

	if (ret < 0)

		goto bail;



	ret = kernel_setsockopt(sock, IPPROTO_TCP, TCP_KEEPCNT,

				(char *)&keepcnt, sizeof(keepcnt));

	if (ret < 0)

		goto bail;



	ret = kernel_setsockopt(sock, IPPROTO_TCP, TCP_KEEPIDLE,

				(char *)&keepidle, sizeof(keepidle));

	if (ret < 0)

		goto bail;



	/* KEEPINTVL is the interval between successive probes. We follow

	 * the model in xs_tcp_finish_connecting() and re-use keepidle.

	 */

	ret = kernel_setsockopt(sock, IPPROTO_TCP, TCP_KEEPINTVL,

				(char *)&keepidle, sizeof(keepidle));

bail:

	return ret;

}



static int rds_tcp_accept_one(struct socket *sock)

{

	struct socket *new_sock = NULL;

	struct rds_connection *conn;

	int ret;

	struct inet_sock *inet;

	struct rds_tcp_connection *rs_tcp;



	ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,

			       sock->sk->sk_protocol, &new_sock);
@@ -63,6 +96,10 @@ static int rds_tcp_accept_one(struct socket *sock) 
	if (ret < 0)

		goto out;



	ret = rds_tcp_keepalive(new_sock);

	if (ret < 0)

		goto out;



	rds_tcp_tune(new_sock);



	inet = inet_sk(new_sock->sk);
@@ -77,6 +114,15 @@ static int rds_tcp_accept_one(struct socket *sock) 
		ret = PTR_ERR(conn);

		goto out;

	}

	/* An incoming SYN request came in, and TCP just accepted it.

	 * We always create a new conn for listen side of TCP, and do not

	 * add it to the c_hash_list.

	 *

	 * If the client reboots, this conn will need to be cleaned up.

	 * rds_tcp_state_change() will do that cleanup

	 */

	rs_tcp = (struct rds_tcp_connection *)conn->c_transport_data;

	WARN_ON(!rs_tcp || rs_tcp->t_sock);



	/*

	 * see the comment above rds_queue_delayed_reconnect()

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