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Date: Tue, 5 May 2015 15:20:51 -0400
From: Sowmini Varadhan <sowmini.varadhan@...cle.com>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: chien.yen@...cle.com, davem@...emloft.net,
rds-devel@....oracle.com, ajaykumar.hotchandani@...cle.com,
Sowmini Varadhan <sowmini.varadhan@...cle.com>
Subject: [PATCH v2 1/2] 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@...cle.com>
---
v2: DaveM comments- make the TCP server side recovery follow patterns in
NFS/RPC, and keep things neat without needless memory bloat.
net/rds/connection.c | 4 ++++
net/rds/tcp_connect.c | 1 +
net/rds/tcp_listen.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 51 insertions(+), 0 deletions(-)
diff --git a/net/rds/connection.c b/net/rds/connection.c
index 14f0413..60f0cd6 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);
diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c
index f9f564a..973109c 100644
--- 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 23ab4dc..0da49e3 100644
--- 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()
--
1.7.1
--
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