linux_dsm_epyc7002/net/rds/tcp_connect.c
Sowmini Varadhan bd7c5f983f RDS: TCP: Synchronize accept() and connect() paths on t_conn_lock.
An arbitration scheme for duelling SYNs is implemented as part of
commit 241b271952 ("RDS-TCP: Reset tcp callbacks if re-using an
outgoing socket in rds_tcp_accept_one()") which ensures that both nodes
involved will arrive at the same arbitration decision. However, this
needs to be synchronized with an outgoing SYN to be generated by
rds_tcp_conn_connect(). This commit achieves the synchronization
through the t_conn_lock mutex in struct rds_tcp_connection.

The rds_conn_state is checked in rds_tcp_conn_connect() after acquiring
the t_conn_lock mutex.  A SYN is sent out only if the RDS connection is
not already UP (an UP would indicate that rds_tcp_accept_one() has
completed 3WH, so no SYN needs to be generated).

Similarly, the rds_conn_state is checked in rds_tcp_accept_one() after
acquiring the t_conn_lock mutex. The only acceptable states (to
allow continuation of the arbitration logic) are UP (i.e., outgoing SYN
was SYN-ACKed by peer after it sent us the SYN) or CONNECTING (we sent
outgoing SYN before we saw incoming SYN).

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-05-03 16:03:44 -04:00

168 lines
4.5 KiB
C

/*
* Copyright (c) 2006 Oracle. 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/in.h>
#include <net/tcp.h>
#include "rds.h"
#include "tcp.h"
void rds_tcp_state_change(struct sock *sk)
{
void (*state_change)(struct sock *sk);
struct rds_connection *conn;
struct rds_tcp_connection *tc;
read_lock(&sk->sk_callback_lock);
conn = sk->sk_user_data;
if (!conn) {
state_change = sk->sk_state_change;
goto out;
}
tc = conn->c_transport_data;
state_change = tc->t_orig_state_change;
rdsdebug("sock %p state_change to %d\n", tc->t_sock, sk->sk_state);
switch(sk->sk_state) {
/* ignore connecting sockets as they make progress */
case TCP_SYN_SENT:
case TCP_SYN_RECV:
break;
case TCP_ESTABLISHED:
rds_connect_complete(conn);
break;
case TCP_CLOSE_WAIT:
case TCP_CLOSE:
rds_conn_drop(conn);
default:
break;
}
out:
read_unlock(&sk->sk_callback_lock);
state_change(sk);
}
int rds_tcp_conn_connect(struct rds_connection *conn)
{
struct socket *sock = NULL;
struct sockaddr_in src, dest;
int ret;
struct rds_tcp_connection *tc = conn->c_transport_data;
mutex_lock(&tc->t_conn_lock);
if (rds_conn_up(conn)) {
mutex_unlock(&tc->t_conn_lock);
return 0;
}
ret = sock_create_kern(rds_conn_net(conn), PF_INET,
SOCK_STREAM, IPPROTO_TCP, &sock);
if (ret < 0)
goto out;
rds_tcp_tune(sock);
src.sin_family = AF_INET;
src.sin_addr.s_addr = (__force u32)conn->c_laddr;
src.sin_port = (__force u16)htons(0);
ret = sock->ops->bind(sock, (struct sockaddr *)&src, sizeof(src));
if (ret) {
rdsdebug("bind failed with %d at address %pI4\n",
ret, &conn->c_laddr);
goto out;
}
dest.sin_family = AF_INET;
dest.sin_addr.s_addr = (__force u32)conn->c_faddr;
dest.sin_port = (__force u16)htons(RDS_TCP_PORT);
/*
* once we call connect() we can start getting callbacks and they
* own the socket
*/
rds_tcp_set_callbacks(sock, conn);
ret = sock->ops->connect(sock, (struct sockaddr *)&dest, sizeof(dest),
O_NONBLOCK);
rdsdebug("connect to address %pI4 returned %d\n", &conn->c_faddr, ret);
if (ret == -EINPROGRESS)
ret = 0;
if (ret == 0) {
rds_tcp_keepalive(sock);
sock = NULL;
} else {
rds_tcp_restore_callbacks(sock, conn->c_transport_data);
}
out:
mutex_unlock(&tc->t_conn_lock);
if (sock)
sock_release(sock);
return ret;
}
/*
* Before killing the tcp socket this needs to serialize with callbacks. The
* caller has already grabbed the sending sem so we're serialized with other
* senders.
*
* TCP calls the callbacks with the sock lock so we hold it while we reset the
* callbacks to those set by TCP. Our callbacks won't execute again once we
* hold the sock lock.
*/
void rds_tcp_conn_shutdown(struct rds_connection *conn)
{
struct rds_tcp_connection *tc = conn->c_transport_data;
struct socket *sock = tc->t_sock;
rdsdebug("shutting down conn %p tc %p sock %p\n", conn, tc, sock);
if (sock) {
sock->ops->shutdown(sock, RCV_SHUTDOWN | SEND_SHUTDOWN);
lock_sock(sock->sk);
rds_tcp_restore_callbacks(sock, tc); /* tc->tc_sock = NULL */
release_sock(sock->sk);
sock_release(sock);
}
if (tc->t_tinc) {
rds_inc_put(&tc->t_tinc->ti_inc);
tc->t_tinc = NULL;
}
tc->t_tinc_hdr_rem = sizeof(struct rds_header);
tc->t_tinc_data_rem = 0;
}