![Sowmini Varadhan](/assets/img/avatar_default.png)
When 2 RDS peers initiate an RDS-TCP connection simultaneously,
there is a potential for "duelling syns" on either/both sides.
See commit 241b271952
("RDS-TCP: Reset tcp callbacks if re-using an
outgoing socket in rds_tcp_accept_one()") for a description of this
condition, and the arbitration logic which ensures that the
numerically large IP address in the TCP connection is bound to the
RDS_TCP_PORT ("canonical ordering").
The rds_connection should not be marked as RDS_CONN_UP until the
arbitration logic has converged for the following reason. The sender
may start transmitting RDS datagrams as soon as RDS_CONN_UP is set,
and since the sender removes all datagrams from the rds_connection's
cp_retrans queue based on TCP acks. If the TCP ack was sent from
a tcp socket that got reset as part of duel aribitration (but
before data was delivered to the receivers RDS socket layer),
the sender may end up prematurely freeing the datagram, and
the datagram is no longer reliably deliverable.
This patch remedies that condition by making sure that, upon
receipt of 3WH completion state change notification of TCP_ESTABLISHED
in rds_tcp_state_change, we mark the rds_connection as RDS_CONN_UP
if, and only if, the IP addresses and ports for the connection are
canonically ordered. In all other cases, rds_tcp_state_change will
force an rds_conn_path_drop(), and rds_queue_reconnect() on
both peers will restart the connection to ensure canonical ordering.
A side-effect of enforcing this condition in rds_tcp_state_change()
is that rds_tcp_accept_one_path() can now be refactored for simplicity.
It is also no longer possible to encounter an RDS_CONN_UP connection in
the arbitration logic in rds_tcp_accept_one().
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>
296 lines
8.2 KiB
C
296 lines
8.2 KiB
C
/*
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* Copyright (c) 2006 Oracle. All rights reserved.
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*
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* This software is available to you under a choice of one of two
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* licenses. You may choose to be licensed under the terms of the GNU
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* General Public License (GPL) Version 2, available from the file
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* COPYING in the main directory of this source tree, or the
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* OpenIB.org BSD license below:
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above
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* copyright notice, this list of conditions and the following
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* disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/gfp.h>
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#include <linux/in.h>
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#include <net/tcp.h>
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#include "rds.h"
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#include "tcp.h"
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int rds_tcp_keepalive(struct socket *sock)
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{
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/* values below based on xs_udp_default_timeout */
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int keepidle = 5; /* send a probe 'keepidle' secs after last data */
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int keepcnt = 5; /* number of unack'ed probes before declaring dead */
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int keepalive = 1;
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int ret = 0;
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ret = kernel_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
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(char *)&keepalive, sizeof(keepalive));
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if (ret < 0)
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goto bail;
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ret = kernel_setsockopt(sock, IPPROTO_TCP, TCP_KEEPCNT,
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(char *)&keepcnt, sizeof(keepcnt));
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if (ret < 0)
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goto bail;
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ret = kernel_setsockopt(sock, IPPROTO_TCP, TCP_KEEPIDLE,
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(char *)&keepidle, sizeof(keepidle));
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if (ret < 0)
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goto bail;
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/* KEEPINTVL is the interval between successive probes. We follow
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* the model in xs_tcp_finish_connecting() and re-use keepidle.
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*/
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ret = kernel_setsockopt(sock, IPPROTO_TCP, TCP_KEEPINTVL,
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(char *)&keepidle, sizeof(keepidle));
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bail:
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return ret;
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}
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/* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the
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* client's ipaddr < server's ipaddr. Otherwise, close the accepted
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* socket and force a reconneect from smaller -> larger ip addr. The reason
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* we special case cp_index 0 is to allow the rds probe ping itself to itself
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* get through efficiently.
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* Since reconnects are only initiated from the node with the numerically
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* smaller ip address, we recycle conns in RDS_CONN_ERROR on the passive side
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* by moving them to CONNECTING in this function.
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*/
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struct rds_tcp_connection *rds_tcp_accept_one_path(struct rds_connection *conn)
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{
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int i;
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bool peer_is_smaller = (conn->c_faddr < conn->c_laddr);
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int npaths = max_t(int, 1, conn->c_npaths);
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/* for mprds, all paths MUST be initiated by the peer
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* with the smaller address.
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*/
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if (!peer_is_smaller) {
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/* Make sure we initiate at least one path if this
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* has not already been done; rds_start_mprds() will
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* take care of additional paths, if necessary.
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*/
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if (npaths == 1)
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rds_conn_path_connect_if_down(&conn->c_path[0]);
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return NULL;
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}
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for (i = 0; i < npaths; i++) {
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struct rds_conn_path *cp = &conn->c_path[i];
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if (rds_conn_path_transition(cp, RDS_CONN_DOWN,
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RDS_CONN_CONNECTING) ||
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rds_conn_path_transition(cp, RDS_CONN_ERROR,
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RDS_CONN_CONNECTING)) {
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return cp->cp_transport_data;
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}
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}
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return NULL;
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}
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int rds_tcp_accept_one(struct socket *sock)
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{
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struct socket *new_sock = NULL;
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struct rds_connection *conn;
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int ret;
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struct inet_sock *inet;
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struct rds_tcp_connection *rs_tcp = NULL;
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int conn_state;
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struct rds_conn_path *cp;
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if (!sock) /* module unload or netns delete in progress */
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return -ENETUNREACH;
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ret = sock_create_kern(sock_net(sock->sk), sock->sk->sk_family,
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sock->sk->sk_type, sock->sk->sk_protocol,
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&new_sock);
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if (ret)
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goto out;
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new_sock->type = sock->type;
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new_sock->ops = sock->ops;
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ret = sock->ops->accept(sock, new_sock, O_NONBLOCK);
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if (ret < 0)
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goto out;
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ret = rds_tcp_keepalive(new_sock);
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if (ret < 0)
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goto out;
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rds_tcp_tune(new_sock);
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inet = inet_sk(new_sock->sk);
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rdsdebug("accepted tcp %pI4:%u -> %pI4:%u\n",
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&inet->inet_saddr, ntohs(inet->inet_sport),
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&inet->inet_daddr, ntohs(inet->inet_dport));
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conn = rds_conn_create(sock_net(sock->sk),
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inet->inet_saddr, inet->inet_daddr,
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&rds_tcp_transport, GFP_KERNEL);
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if (IS_ERR(conn)) {
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ret = PTR_ERR(conn);
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goto out;
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}
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/* An incoming SYN request came in, and TCP just accepted it.
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*
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* If the client reboots, this conn will need to be cleaned up.
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* rds_tcp_state_change() will do that cleanup
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*/
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rs_tcp = rds_tcp_accept_one_path(conn);
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if (!rs_tcp)
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goto rst_nsk;
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mutex_lock(&rs_tcp->t_conn_path_lock);
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cp = rs_tcp->t_cpath;
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conn_state = rds_conn_path_state(cp);
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WARN_ON(conn_state == RDS_CONN_UP);
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if (conn_state != RDS_CONN_CONNECTING && conn_state != RDS_CONN_ERROR)
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goto rst_nsk;
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if (rs_tcp->t_sock) {
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/* Need to resolve a duelling SYN between peers.
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* We have an outstanding SYN to this peer, which may
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* potentially have transitioned to the RDS_CONN_UP state,
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* so we must quiesce any send threads before resetting
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* c_transport_data.
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*/
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if (ntohl(inet->inet_saddr) < ntohl(inet->inet_daddr) ||
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!cp->cp_outgoing) {
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goto rst_nsk;
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} else {
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rds_tcp_reset_callbacks(new_sock, cp);
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cp->cp_outgoing = 0;
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/* rds_connect_path_complete() marks RDS_CONN_UP */
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rds_connect_path_complete(cp, RDS_CONN_RESETTING);
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}
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} else {
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rds_tcp_set_callbacks(new_sock, cp);
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rds_connect_path_complete(cp, RDS_CONN_CONNECTING);
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}
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new_sock = NULL;
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ret = 0;
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goto out;
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rst_nsk:
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/* reset the newly returned accept sock and bail */
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kernel_sock_shutdown(new_sock, SHUT_RDWR);
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ret = 0;
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out:
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if (rs_tcp)
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mutex_unlock(&rs_tcp->t_conn_path_lock);
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if (new_sock)
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sock_release(new_sock);
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return ret;
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}
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void rds_tcp_listen_data_ready(struct sock *sk)
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{
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void (*ready)(struct sock *sk);
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rdsdebug("listen data ready sk %p\n", sk);
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read_lock_bh(&sk->sk_callback_lock);
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ready = sk->sk_user_data;
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if (!ready) { /* check for teardown race */
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ready = sk->sk_data_ready;
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goto out;
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}
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/*
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* ->sk_data_ready is also called for a newly established child socket
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* before it has been accepted and the accepter has set up their
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* data_ready.. we only want to queue listen work for our listening
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* socket
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*/
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if (sk->sk_state == TCP_LISTEN)
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rds_tcp_accept_work(sk);
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else
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ready = rds_tcp_listen_sock_def_readable(sock_net(sk));
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out:
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read_unlock_bh(&sk->sk_callback_lock);
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ready(sk);
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}
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struct socket *rds_tcp_listen_init(struct net *net)
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{
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struct sockaddr_in sin;
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struct socket *sock = NULL;
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int ret;
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ret = sock_create_kern(net, PF_INET, SOCK_STREAM, IPPROTO_TCP, &sock);
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if (ret < 0)
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goto out;
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sock->sk->sk_reuse = SK_CAN_REUSE;
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rds_tcp_nonagle(sock);
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write_lock_bh(&sock->sk->sk_callback_lock);
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sock->sk->sk_user_data = sock->sk->sk_data_ready;
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sock->sk->sk_data_ready = rds_tcp_listen_data_ready;
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write_unlock_bh(&sock->sk->sk_callback_lock);
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sin.sin_family = PF_INET;
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sin.sin_addr.s_addr = (__force u32)htonl(INADDR_ANY);
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sin.sin_port = (__force u16)htons(RDS_TCP_PORT);
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ret = sock->ops->bind(sock, (struct sockaddr *)&sin, sizeof(sin));
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if (ret < 0)
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goto out;
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ret = sock->ops->listen(sock, 64);
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if (ret < 0)
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goto out;
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return sock;
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out:
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if (sock)
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sock_release(sock);
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return NULL;
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}
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void rds_tcp_listen_stop(struct socket *sock)
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{
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struct sock *sk;
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if (!sock)
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return;
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sk = sock->sk;
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/* serialize with and prevent further callbacks */
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lock_sock(sk);
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write_lock_bh(&sk->sk_callback_lock);
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if (sk->sk_user_data) {
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sk->sk_data_ready = sk->sk_user_data;
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sk->sk_user_data = NULL;
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}
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write_unlock_bh(&sk->sk_callback_lock);
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release_sock(sk);
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/* wait for accepts to stop and close the socket */
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flush_workqueue(rds_wq);
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sock_release(sock);
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}
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