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>

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 14f041398ca1744ea7596decaad7145184c7df0c..60f0cd6ed15fa3b860f7ed64d19c630b630d67ef 100644 (file)
--- 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);

diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c
index f9f564a6c960e47b3c243d11a3e11317c5a56353..973109c7b8e86f21bec783eb9e4e118e6e8ebb8b 100644 (file)
--- a/net/rds/tcp_connect.c
+++ b/net/rds/tcp_connect.c
@@ -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:

diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index 23ab4dcd1d9f03942aa4d70bc7f6d9aa401f7707..0da49e34495f1e974bf466b83ba1144ec8965f61 100644 (file)
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -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()