net/rds/tcp_listen.c - linux - Git at Google

 /*
  * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
  * General Public License (GPL) Version 2, available from the file
  * COPYING in the main directory of this source tree, or the
  * OpenIB.org BSD license below:
  *
  *     Redistribution and use in source and binary forms, with or
  *     without modification, are permitted provided that the following
  *     conditions are met:
  *
  *      - Redistributions of source code must retain the above
  *        copyright notice, this list of conditions and the following
  *        disclaimer.
  *
  *      - Redistributions in binary form must reproduce the above
  *        copyright notice, this list of conditions and the following
  *        disclaimer in the documentation and/or other materials
  *        provided with the distribution.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
  */
 #include <linux/kernel.h>
 #include <linux/gfp.h>
 #include <linux/in.h>
 #include <net/tcp.h>

 #include "rds.h"
 #include "tcp.h"

 void 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 */

 	sock_set_keepalive(sock->sk);
 	tcp_sock_set_keepcnt(sock->sk, keepcnt);
 	tcp_sock_set_keepidle(sock->sk, keepidle);
 	/* KEEPINTVL is the interval between successive probes. We follow
 	 * the model in xs_tcp_finish_connecting() and re-use keepidle.
 	 */
 	tcp_sock_set_keepintvl(sock->sk, keepidle);
 }

 /* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the
  * client's ipaddr < server's ipaddr. Otherwise, close the accepted
  * socket and force a reconneect from smaller -> larger ip addr. The reason
  * we special case cp_index 0 is to allow the rds probe ping itself to itself
  * get through efficiently.
  * Since reconnects are only initiated from the node with the numerically
  * smaller ip address, we recycle conns in RDS_CONN_ERROR on the passive side
  * by moving them to CONNECTING in this function.
  */
 static
 struct rds_tcp_connection *rds_tcp_accept_one_path(struct rds_connection *conn)
 {
 	int i;
 	int npaths = max_t(int, 1, conn->c_npaths);

 	/* for mprds, all paths MUST be initiated by the peer
 	 * with the smaller address.
 	 */
 	if (rds_addr_cmp(&conn->c_faddr, &conn->c_laddr) >= 0) {
 		/* Make sure we initiate at least one path if this
 		 * has not already been done; rds_start_mprds() will
 		 * take care of additional paths, if necessary.
 		 */
 		if (npaths == 1)
 			rds_conn_path_connect_if_down(&conn->c_path[0]);
 		return NULL;
 	}

 	for (i = 0; i < npaths; i++) {
 		struct rds_conn_path *cp = &conn->c_path[i];

 		if (rds_conn_path_transition(cp, RDS_CONN_DOWN,
 					     RDS_CONN_CONNECTING) ||
 		    rds_conn_path_transition(cp, RDS_CONN_ERROR,
 					     RDS_CONN_CONNECTING)) {
 			return cp->cp_transport_data;
 		}
 	}
 	return NULL;
 }

 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 = NULL;
 	int conn_state;
 	struct rds_conn_path *cp;
 	struct in6_addr *my_addr, *peer_addr;
 #if !IS_ENABLED(CONFIG_IPV6)
 	struct in6_addr saddr, daddr;
 #endif
 	int dev_if = 0;

 	if (!sock) /* module unload or netns delete in progress */
 		return -ENETUNREACH;

 	ret = sock_create_lite(sock->sk->sk_family,
 			       sock->sk->sk_type, sock->sk->sk_protocol,
 			       &new_sock);
 	if (ret)
 		goto out;

 	ret = sock->ops->accept(sock, new_sock, O_NONBLOCK, true);
 	if (ret < 0)
 		goto out;

 	/* sock_create_lite() does not get a hold on the owner module so we
 	 * need to do it here.  Note that sock_release() uses sock->ops to
 	 * determine if it needs to decrement the reference count.  So set
 	 * sock->ops after calling accept() in case that fails.  And there's
 	 * no need to do try_module_get() as the listener should have a hold
 	 * already.
 	 */
 	new_sock->ops = sock->ops;
 	__module_get(new_sock->ops->owner);

 	rds_tcp_keepalive(new_sock);
 	rds_tcp_tune(new_sock);

 	inet = inet_sk(new_sock->sk);

 #if IS_ENABLED(CONFIG_IPV6)
 	my_addr = &new_sock->sk->sk_v6_rcv_saddr;
 	peer_addr = &new_sock->sk->sk_v6_daddr;
 #else
 	ipv6_addr_set_v4mapped(inet->inet_saddr, &saddr);
 	ipv6_addr_set_v4mapped(inet->inet_daddr, &daddr);
 	my_addr = &saddr;
 	peer_addr = &daddr;
 #endif
 	rdsdebug("accepted family %d tcp %pI6c:%u -> %pI6c:%u\n",
 		 sock->sk->sk_family,
 		 my_addr, ntohs(inet->inet_sport),
 		 peer_addr, ntohs(inet->inet_dport));

 #if IS_ENABLED(CONFIG_IPV6)
 	/* sk_bound_dev_if is not set if the peer address is not link local
 	 * address.  In this case, it happens that mcast_oif is set.  So
 	 * just use it.
 	 */
 	if ((ipv6_addr_type(my_addr) & IPV6_ADDR_LINKLOCAL) &&
 	    !(ipv6_addr_type(peer_addr) & IPV6_ADDR_LINKLOCAL)) {
 		struct ipv6_pinfo *inet6;

 		inet6 = inet6_sk(new_sock->sk);
 		dev_if = inet6->mcast_oif;
 	} else {
 		dev_if = new_sock->sk->sk_bound_dev_if;
 	}
 #endif

 	conn = rds_conn_create(sock_net(sock->sk),
 			       my_addr, peer_addr,
 			       &rds_tcp_transport, 0, GFP_KERNEL, dev_if);

 	if (IS_ERR(conn)) {
 		ret = PTR_ERR(conn);
 		goto out;
 	}
 	/* An incoming SYN request came in, and TCP just accepted it.
 	 *
 	 * If the client reboots, this conn will need to be cleaned up.
 	 * rds_tcp_state_change() will do that cleanup
 	 */
 	rs_tcp = rds_tcp_accept_one_path(conn);
 	if (!rs_tcp)
 		goto rst_nsk;
 	mutex_lock(&rs_tcp->t_conn_path_lock);
 	cp = rs_tcp->t_cpath;
 	conn_state = rds_conn_path_state(cp);
 	WARN_ON(conn_state == RDS_CONN_UP);
 	if (conn_state != RDS_CONN_CONNECTING && conn_state != RDS_CONN_ERROR)
 		goto rst_nsk;
 	if (rs_tcp->t_sock) {
 		/* Duelling SYN has been handled in rds_tcp_accept_one() */
 		rds_tcp_reset_callbacks(new_sock, cp);
 		/* rds_connect_path_complete() marks RDS_CONN_UP */
 		rds_connect_path_complete(cp, RDS_CONN_RESETTING);
 	} else {
 		rds_tcp_set_callbacks(new_sock, cp);
 		rds_connect_path_complete(cp, RDS_CONN_CONNECTING);
 	}
 	new_sock = NULL;
 	ret = 0;
 	if (conn->c_npaths == 0)
 		rds_send_ping(cp->cp_conn, cp->cp_index);
 	goto out;
 rst_nsk:
 	/* reset the newly returned accept sock and bail.
 	 * It is safe to set linger on new_sock because the RDS connection
 	 * has not been brought up on new_sock, so no RDS-level data could
 	 * be pending on it. By setting linger, we achieve the side-effect
 	 * of avoiding TIME_WAIT state on new_sock.
 	 */
 	sock_no_linger(new_sock->sk);
 	kernel_sock_shutdown(new_sock, SHUT_RDWR);
 	ret = 0;
 out:
 	if (rs_tcp)
 		mutex_unlock(&rs_tcp->t_conn_path_lock);
 	if (new_sock)
 		sock_release(new_sock);
 	return ret;
 }

 void rds_tcp_listen_data_ready(struct sock *sk)
 {
 	void (*ready)(struct sock *sk);

 	rdsdebug("listen data ready sk %p\n", sk);

 	read_lock_bh(&sk->sk_callback_lock);
 	ready = sk->sk_user_data;
 	if (!ready) { /* check for teardown race */
 		ready = sk->sk_data_ready;
 		goto out;
 	}

 	/*
 	 * ->sk_data_ready is also called for a newly established child socket
 	 * before it has been accepted and the accepter has set up their
 	 * data_ready.. we only want to queue listen work for our listening
 	 * socket
 	 *
 	 * (*ready)() may be null if we are racing with netns delete, and
 	 * the listen socket is being torn down.
 	 */
 	if (sk->sk_state == TCP_LISTEN)
 		rds_tcp_accept_work(sk);
 	else
 		ready = rds_tcp_listen_sock_def_readable(sock_net(sk));

 out:
 	read_unlock_bh(&sk->sk_callback_lock);
 	if (ready)
 		ready(sk);
 }

 struct socket *rds_tcp_listen_init(struct net *net, bool isv6)
 {
 	struct socket *sock = NULL;
 	struct sockaddr_storage ss;
 	struct sockaddr_in6 *sin6;
 	struct sockaddr_in *sin;
 	int addr_len;
 	int ret;

 	ret = sock_create_kern(net, isv6 ? PF_INET6 : PF_INET, SOCK_STREAM,
 			       IPPROTO_TCP, &sock);
 	if (ret < 0) {
 		rdsdebug("could not create %s listener socket: %d\n",
 			 isv6 ? "IPv6" : "IPv4", ret);
 		goto out;
 	}

 	sock->sk->sk_reuse = SK_CAN_REUSE;
 	tcp_sock_set_nodelay(sock->sk);

 	write_lock_bh(&sock->sk->sk_callback_lock);
 	sock->sk->sk_user_data = sock->sk->sk_data_ready;
 	sock->sk->sk_data_ready = rds_tcp_listen_data_ready;
 	write_unlock_bh(&sock->sk->sk_callback_lock);

 	if (isv6) {
 		sin6 = (struct sockaddr_in6 *)&ss;
 		sin6->sin6_family = PF_INET6;
 		sin6->sin6_addr = in6addr_any;
 		sin6->sin6_port = (__force u16)htons(RDS_TCP_PORT);
 		sin6->sin6_scope_id = 0;
 		sin6->sin6_flowinfo = 0;
 		addr_len = sizeof(*sin6);
 	} else {
 		sin = (struct sockaddr_in *)&ss;
 		sin->sin_family = PF_INET;
 		sin->sin_addr.s_addr = INADDR_ANY;
 		sin->sin_port = (__force u16)htons(RDS_TCP_PORT);
 		addr_len = sizeof(*sin);
 	}

 	ret = sock->ops->bind(sock, (struct sockaddr *)&ss, addr_len);
 	if (ret < 0) {
 		rdsdebug("could not bind %s listener socket: %d\n",
 			 isv6 ? "IPv6" : "IPv4", ret);
 		goto out;
 	}

 	ret = sock->ops->listen(sock, 64);
 	if (ret < 0)
 		goto out;

 	return sock;
 out:
 	if (sock)
 		sock_release(sock);
 	return NULL;
 }

 void rds_tcp_listen_stop(struct socket *sock, struct work_struct *acceptor)
 {
 	struct sock *sk;

 	if (!sock)
 		return;

 	sk = sock->sk;

 	/* serialize with and prevent further callbacks */
 	lock_sock(sk);
 	write_lock_bh(&sk->sk_callback_lock);
 	if (sk->sk_user_data) {
 		sk->sk_data_ready = sk->sk_user_data;
 		sk->sk_user_data = NULL;
 	}
 	write_unlock_bh(&sk->sk_callback_lock);
 	release_sock(sk);

 	/* wait for accepts to stop and close the socket */
 	flush_workqueue(rds_wq);
 	flush_work(acceptor);
 	sock_release(sock);
 }
	/*
	* Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
	*
	* This software is available to you under a choice of one of two
	* licenses. You may choose to be licensed under the terms of the GNU
	* General Public License (GPL) Version 2, available from the file
	* COPYING in the main directory of this source tree, or the
	* OpenIB.org BSD license below:
	*
	* Redistribution and use in source and binary forms, with or
	* without modification, are permitted provided that the following
	* conditions are met:
	*
	* - Redistributions of source code must retain the above
	* copyright notice, this list of conditions and the following
	* disclaimer.
	*
	* - Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following
	* disclaimer in the documentation and/or other materials
	* provided with the distribution.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
	* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
	* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
	* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	* SOFTWARE.
	*
	*/
	#include <linux/kernel.h>
	#include <linux/gfp.h>
	#include <linux/in.h>
	#include <net/tcp.h>

	#include "rds.h"
	#include "tcp.h"

	void 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 */

	sock_set_keepalive(sock->sk);
	tcp_sock_set_keepcnt(sock->sk, keepcnt);
	tcp_sock_set_keepidle(sock->sk, keepidle);
	/* KEEPINTVL is the interval between successive probes. We follow
	* the model in xs_tcp_finish_connecting() and re-use keepidle.
	*/
	tcp_sock_set_keepintvl(sock->sk, keepidle);
	}

	/* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the
	* client's ipaddr < server's ipaddr. Otherwise, close the accepted
	* socket and force a reconneect from smaller -> larger ip addr. The reason
	* we special case cp_index 0 is to allow the rds probe ping itself to itself
	* get through efficiently.
	* Since reconnects are only initiated from the node with the numerically
	* smaller ip address, we recycle conns in RDS_CONN_ERROR on the passive side
	* by moving them to CONNECTING in this function.
	*/
	static
	struct rds_tcp_connection rds_tcp_accept_one_path(struct rds_connection conn)
	{
	int i;
	int npaths = max_t(int, 1, conn->c_npaths);

	/* for mprds, all paths MUST be initiated by the peer
	* with the smaller address.
	*/
	if (rds_addr_cmp(&conn->c_faddr, &conn->c_laddr) >= 0) {
	/* Make sure we initiate at least one path if this
	* has not already been done; rds_start_mprds() will
	* take care of additional paths, if necessary.
	*/
	if (npaths == 1)
	rds_conn_path_connect_if_down(&conn->c_path[0]);
	return NULL;
	}

	for (i = 0; i < npaths; i++) {
	struct rds_conn_path *cp = &conn->c_path[i];

	if (rds_conn_path_transition(cp, RDS_CONN_DOWN,
	RDS_CONN_CONNECTING) \|\|
	rds_conn_path_transition(cp, RDS_CONN_ERROR,
	RDS_CONN_CONNECTING)) {
	return cp->cp_transport_data;
	}
	}
	return NULL;
	}

	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 = NULL;
	int conn_state;
	struct rds_conn_path *cp;
	struct in6_addr my_addr, peer_addr;
	#if !IS_ENABLED(CONFIG_IPV6)
	struct in6_addr saddr, daddr;
	#endif
	int dev_if = 0;

	if (!sock) /* module unload or netns delete in progress */
	return -ENETUNREACH;

	ret = sock_create_lite(sock->sk->sk_family,
	sock->sk->sk_type, sock->sk->sk_protocol,
	&new_sock);
	if (ret)
	goto out;

	ret = sock->ops->accept(sock, new_sock, O_NONBLOCK, true);
	if (ret < 0)
	goto out;

	/* sock_create_lite() does not get a hold on the owner module so we
	* need to do it here. Note that sock_release() uses sock->ops to
	* determine if it needs to decrement the reference count. So set
	* sock->ops after calling accept() in case that fails. And there's
	* no need to do try_module_get() as the listener should have a hold
	* already.
	*/
	new_sock->ops = sock->ops;
	__module_get(new_sock->ops->owner);

	rds_tcp_keepalive(new_sock);
	rds_tcp_tune(new_sock);

	inet = inet_sk(new_sock->sk);

	#if IS_ENABLED(CONFIG_IPV6)
	my_addr = &new_sock->sk->sk_v6_rcv_saddr;
	peer_addr = &new_sock->sk->sk_v6_daddr;
	#else
	ipv6_addr_set_v4mapped(inet->inet_saddr, &saddr);
	ipv6_addr_set_v4mapped(inet->inet_daddr, &daddr);
	my_addr = &saddr;
	peer_addr = &daddr;
	#endif
	rdsdebug("accepted family %d tcp %pI6c:%u -> %pI6c:%u\n",
	sock->sk->sk_family,
	my_addr, ntohs(inet->inet_sport),
	peer_addr, ntohs(inet->inet_dport));

	#if IS_ENABLED(CONFIG_IPV6)
	/* sk_bound_dev_if is not set if the peer address is not link local
	* address. In this case, it happens that mcast_oif is set. So
	* just use it.
	*/
	if ((ipv6_addr_type(my_addr) & IPV6_ADDR_LINKLOCAL) &&
	!(ipv6_addr_type(peer_addr) & IPV6_ADDR_LINKLOCAL)) {
	struct ipv6_pinfo *inet6;

	inet6 = inet6_sk(new_sock->sk);
	dev_if = inet6->mcast_oif;
	} else {
	dev_if = new_sock->sk->sk_bound_dev_if;
	}
	#endif

	conn = rds_conn_create(sock_net(sock->sk),
	my_addr, peer_addr,
	&rds_tcp_transport, 0, GFP_KERNEL, dev_if);

	if (IS_ERR(conn)) {
	ret = PTR_ERR(conn);
	goto out;
	}
	/* An incoming SYN request came in, and TCP just accepted it.
	*
	* If the client reboots, this conn will need to be cleaned up.
	* rds_tcp_state_change() will do that cleanup
	*/
	rs_tcp = rds_tcp_accept_one_path(conn);
	if (!rs_tcp)
	goto rst_nsk;
	mutex_lock(&rs_tcp->t_conn_path_lock);
	cp = rs_tcp->t_cpath;
	conn_state = rds_conn_path_state(cp);
	WARN_ON(conn_state == RDS_CONN_UP);
	if (conn_state != RDS_CONN_CONNECTING && conn_state != RDS_CONN_ERROR)
	goto rst_nsk;
	if (rs_tcp->t_sock) {
	/* Duelling SYN has been handled in rds_tcp_accept_one() */
	rds_tcp_reset_callbacks(new_sock, cp);
	/* rds_connect_path_complete() marks RDS_CONN_UP */
	rds_connect_path_complete(cp, RDS_CONN_RESETTING);
	} else {
	rds_tcp_set_callbacks(new_sock, cp);
	rds_connect_path_complete(cp, RDS_CONN_CONNECTING);
	}
	new_sock = NULL;
	ret = 0;
	if (conn->c_npaths == 0)
	rds_send_ping(cp->cp_conn, cp->cp_index);
	goto out;
	rst_nsk:
	/* reset the newly returned accept sock and bail.
	* It is safe to set linger on new_sock because the RDS connection
	* has not been brought up on new_sock, so no RDS-level data could
	* be pending on it. By setting linger, we achieve the side-effect
	* of avoiding TIME_WAIT state on new_sock.
	*/
	sock_no_linger(new_sock->sk);
	kernel_sock_shutdown(new_sock, SHUT_RDWR);
	ret = 0;
	out:
	if (rs_tcp)
	mutex_unlock(&rs_tcp->t_conn_path_lock);
	if (new_sock)
	sock_release(new_sock);
	return ret;
	}

	void rds_tcp_listen_data_ready(struct sock *sk)
	{
	void (ready)(struct sock sk);

	rdsdebug("listen data ready sk %p\n", sk);

	read_lock_bh(&sk->sk_callback_lock);
	ready = sk->sk_user_data;
	if (!ready) { /* check for teardown race */
	ready = sk->sk_data_ready;
	goto out;
	}

	/*
	* ->sk_data_ready is also called for a newly established child socket
	* before it has been accepted and the accepter has set up their
	* data_ready.. we only want to queue listen work for our listening
	* socket
	*
	* (*ready)() may be null if we are racing with netns delete, and
	* the listen socket is being torn down.
	*/
	if (sk->sk_state == TCP_LISTEN)
	rds_tcp_accept_work(sk);
	else
	ready = rds_tcp_listen_sock_def_readable(sock_net(sk));

	out:
	read_unlock_bh(&sk->sk_callback_lock);
	if (ready)
	ready(sk);
	}

	struct socket rds_tcp_listen_init(struct net net, bool isv6)
	{
	struct socket *sock = NULL;
	struct sockaddr_storage ss;
	struct sockaddr_in6 *sin6;
	struct sockaddr_in *sin;
	int addr_len;
	int ret;

	ret = sock_create_kern(net, isv6 ? PF_INET6 : PF_INET, SOCK_STREAM,
	IPPROTO_TCP, &sock);
	if (ret < 0) {
	rdsdebug("could not create %s listener socket: %d\n",
	isv6 ? "IPv6" : "IPv4", ret);
	goto out;
	}

	sock->sk->sk_reuse = SK_CAN_REUSE;
	tcp_sock_set_nodelay(sock->sk);

	write_lock_bh(&sock->sk->sk_callback_lock);
	sock->sk->sk_user_data = sock->sk->sk_data_ready;
	sock->sk->sk_data_ready = rds_tcp_listen_data_ready;
	write_unlock_bh(&sock->sk->sk_callback_lock);

	if (isv6) {
	sin6 = (struct sockaddr_in6 *)&ss;
	sin6->sin6_family = PF_INET6;
	sin6->sin6_addr = in6addr_any;
	sin6->sin6_port = (__force u16)htons(RDS_TCP_PORT);
	sin6->sin6_scope_id = 0;
	sin6->sin6_flowinfo = 0;
	addr_len = sizeof(*sin6);
	} else {
	sin = (struct sockaddr_in *)&ss;
	sin->sin_family = PF_INET;
	sin->sin_addr.s_addr = INADDR_ANY;
	sin->sin_port = (__force u16)htons(RDS_TCP_PORT);
	addr_len = sizeof(*sin);
	}

	ret = sock->ops->bind(sock, (struct sockaddr *)&ss, addr_len);
	if (ret < 0) {
	rdsdebug("could not bind %s listener socket: %d\n",
	isv6 ? "IPv6" : "IPv4", ret);
	goto out;
	}

	ret = sock->ops->listen(sock, 64);
	if (ret < 0)
	goto out;

	return sock;
	out:
	if (sock)
	sock_release(sock);
	return NULL;
	}

	void rds_tcp_listen_stop(struct socket sock, struct work_struct acceptor)
	{
	struct sock *sk;

	if (!sock)
	return;

	sk = sock->sk;

	/* serialize with and prevent further callbacks */
	lock_sock(sk);
	write_lock_bh(&sk->sk_callback_lock);
	if (sk->sk_user_data) {
	sk->sk_data_ready = sk->sk_user_data;
	sk->sk_user_data = NULL;
	}
	write_unlock_bh(&sk->sk_callback_lock);
	release_sock(sk);

	/* wait for accepts to stop and close the socket */
	flush_workqueue(rds_wq);
	flush_work(acceptor);
	sock_release(sock);
	}