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linux-next/net/rds/connection.c
Sowmini Varadhan 3b20fc3897 RDS: Use a single TCP socket for both send and receive.
Commit f711a6ae06 ("net/rds: RDS-TCP: Always create a new rds_sock
for an incoming connection.") modified rds-tcp so that an incoming SYN
would ignore an existing "client" TCP connection which had the local
port set to the transient port.  The motivation for ignoring the existing
"client" connection in f711a6ae was to avoid race conditions and an
endless duel of reconnect attempts triggered by a restart/abort of one
of the nodes in the TCP connection.

However, having separate sockets for active and passive sides
is avoidable, and the simpler model of a single TCP socket for
both send and receives of all RDS connections associated with
that tcp socket makes for easier observability. We avoid the race
conditions from f711a6ae by attempting reconnects in rds_conn_shutdown
if, and only if, the (new) c_outgoing bit is set for RDS_TRANS_TCP.
The c_outgoing bit is initialized in __rds_conn_create().

A side-effect of re-using the client rds_connection for an incoming
SYN is the potential of encountering duelling SYNs, i.e., we
have an outgoing RDS_CONN_CONNECTING socket when we get the incoming
SYN. The logic to arbitrate this criss-crossing SYN exchange in
rds_tcp_accept_one() has been modified to emulate the BGP state
machine: the smaller IP address should back off from the connection attempt.

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-05 03:34:51 -07:00

595 lines
17 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/list.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <net/inet_hashtables.h>
#include "rds.h"
#include "loop.h"
#define RDS_CONNECTION_HASH_BITS 12
#define RDS_CONNECTION_HASH_ENTRIES (1 << RDS_CONNECTION_HASH_BITS)
#define RDS_CONNECTION_HASH_MASK (RDS_CONNECTION_HASH_ENTRIES - 1)
/* converting this to RCU is a chore for another day.. */
static DEFINE_SPINLOCK(rds_conn_lock);
static unsigned long rds_conn_count;
static struct hlist_head rds_conn_hash[RDS_CONNECTION_HASH_ENTRIES];
static struct kmem_cache *rds_conn_slab;
static struct hlist_head *rds_conn_bucket(__be32 laddr, __be32 faddr)
{
static u32 rds_hash_secret __read_mostly;
unsigned long hash;
net_get_random_once(&rds_hash_secret, sizeof(rds_hash_secret));
/* Pass NULL, don't need struct net for hash */
hash = __inet_ehashfn(be32_to_cpu(laddr), 0,
be32_to_cpu(faddr), 0,
rds_hash_secret);
return &rds_conn_hash[hash & RDS_CONNECTION_HASH_MASK];
}
#define rds_conn_info_set(var, test, suffix) do { \
if (test) \
var |= RDS_INFO_CONNECTION_FLAG_##suffix; \
} while (0)
/* rcu read lock must be held or the connection spinlock */
static struct rds_connection *rds_conn_lookup(struct net *net,
struct hlist_head *head,
__be32 laddr, __be32 faddr,
struct rds_transport *trans)
{
struct rds_connection *conn, *ret = NULL;
hlist_for_each_entry_rcu(conn, head, c_hash_node) {
if (conn->c_faddr == faddr && conn->c_laddr == laddr &&
conn->c_trans == trans && net == rds_conn_net(conn)) {
ret = conn;
break;
}
}
rdsdebug("returning conn %p for %pI4 -> %pI4\n", ret,
&laddr, &faddr);
return ret;
}
/*
* This is called by transports as they're bringing down a connection.
* It clears partial message state so that the transport can start sending
* and receiving over this connection again in the future. It is up to
* the transport to have serialized this call with its send and recv.
*/
static void rds_conn_reset(struct rds_connection *conn)
{
rdsdebug("connection %pI4 to %pI4 reset\n",
&conn->c_laddr, &conn->c_faddr);
rds_stats_inc(s_conn_reset);
rds_send_reset(conn);
conn->c_flags = 0;
/* Do not clear next_rx_seq here, else we cannot distinguish
* retransmitted packets from new packets, and will hand all
* of them to the application. That is not consistent with the
* reliability guarantees of RDS. */
}
/*
* There is only every one 'conn' for a given pair of addresses in the
* system at a time. They contain messages to be retransmitted and so
* span the lifetime of the actual underlying transport connections.
*
* For now they are not garbage collected once they're created. They
* are torn down as the module is removed, if ever.
*/
static struct rds_connection *__rds_conn_create(struct net *net,
__be32 laddr, __be32 faddr,
struct rds_transport *trans, gfp_t gfp,
int is_outgoing)
{
struct rds_connection *conn, *parent = NULL;
struct hlist_head *head = rds_conn_bucket(laddr, faddr);
struct rds_transport *loop_trans;
unsigned long flags;
int ret;
rcu_read_lock();
conn = rds_conn_lookup(net, head, laddr, faddr, trans);
if (conn && conn->c_loopback && conn->c_trans != &rds_loop_transport &&
laddr == faddr && !is_outgoing) {
/* This is a looped back IB connection, and we're
* called by the code handling the incoming connect.
* We need a second connection object into which we
* can stick the other QP. */
parent = conn;
conn = parent->c_passive;
}
rcu_read_unlock();
if (conn)
goto out;
conn = kmem_cache_zalloc(rds_conn_slab, gfp);
if (!conn) {
conn = ERR_PTR(-ENOMEM);
goto out;
}
INIT_HLIST_NODE(&conn->c_hash_node);
conn->c_laddr = laddr;
conn->c_faddr = faddr;
spin_lock_init(&conn->c_lock);
conn->c_next_tx_seq = 1;
rds_conn_net_set(conn, net);
init_waitqueue_head(&conn->c_waitq);
INIT_LIST_HEAD(&conn->c_send_queue);
INIT_LIST_HEAD(&conn->c_retrans);
ret = rds_cong_get_maps(conn);
if (ret) {
kmem_cache_free(rds_conn_slab, conn);
conn = ERR_PTR(ret);
goto out;
}
/*
* This is where a connection becomes loopback. If *any* RDS sockets
* can bind to the destination address then we'd rather the messages
* flow through loopback rather than either transport.
*/
loop_trans = rds_trans_get_preferred(net, faddr);
if (loop_trans) {
rds_trans_put(loop_trans);
conn->c_loopback = 1;
if (is_outgoing && trans->t_prefer_loopback) {
/* "outgoing" connection - and the transport
* says it wants the connection handled by the
* loopback transport. This is what TCP does.
*/
trans = &rds_loop_transport;
}
}
if (trans == NULL) {
kmem_cache_free(rds_conn_slab, conn);
conn = ERR_PTR(-ENODEV);
goto out;
}
conn->c_trans = trans;
ret = trans->conn_alloc(conn, gfp);
if (ret) {
kmem_cache_free(rds_conn_slab, conn);
conn = ERR_PTR(ret);
goto out;
}
atomic_set(&conn->c_state, RDS_CONN_DOWN);
conn->c_send_gen = 0;
conn->c_outgoing = (is_outgoing ? 1 : 0);
conn->c_reconnect_jiffies = 0;
INIT_DELAYED_WORK(&conn->c_send_w, rds_send_worker);
INIT_DELAYED_WORK(&conn->c_recv_w, rds_recv_worker);
INIT_DELAYED_WORK(&conn->c_conn_w, rds_connect_worker);
INIT_WORK(&conn->c_down_w, rds_shutdown_worker);
mutex_init(&conn->c_cm_lock);
conn->c_flags = 0;
rdsdebug("allocated conn %p for %pI4 -> %pI4 over %s %s\n",
conn, &laddr, &faddr,
trans->t_name ? trans->t_name : "[unknown]",
is_outgoing ? "(outgoing)" : "");
/*
* Since we ran without holding the conn lock, someone could
* have created the same conn (either normal or passive) in the
* interim. We check while holding the lock. If we won, we complete
* init and return our conn. If we lost, we rollback and return the
* other one.
*/
spin_lock_irqsave(&rds_conn_lock, flags);
if (parent) {
/* Creating passive conn */
if (parent->c_passive) {
trans->conn_free(conn->c_transport_data);
kmem_cache_free(rds_conn_slab, conn);
conn = parent->c_passive;
} else {
parent->c_passive = conn;
rds_cong_add_conn(conn);
rds_conn_count++;
}
} else {
/* Creating normal conn */
struct rds_connection *found;
found = rds_conn_lookup(net, head, laddr, faddr, trans);
if (found) {
trans->conn_free(conn->c_transport_data);
kmem_cache_free(rds_conn_slab, conn);
conn = found;
} else {
hlist_add_head_rcu(&conn->c_hash_node, head);
rds_cong_add_conn(conn);
rds_conn_count++;
}
}
spin_unlock_irqrestore(&rds_conn_lock, flags);
out:
return conn;
}
struct rds_connection *rds_conn_create(struct net *net,
__be32 laddr, __be32 faddr,
struct rds_transport *trans, gfp_t gfp)
{
return __rds_conn_create(net, laddr, faddr, trans, gfp, 0);
}
EXPORT_SYMBOL_GPL(rds_conn_create);
struct rds_connection *rds_conn_create_outgoing(struct net *net,
__be32 laddr, __be32 faddr,
struct rds_transport *trans, gfp_t gfp)
{
return __rds_conn_create(net, laddr, faddr, trans, gfp, 1);
}
EXPORT_SYMBOL_GPL(rds_conn_create_outgoing);
void rds_conn_shutdown(struct rds_connection *conn)
{
/* shut it down unless it's down already */
if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_DOWN)) {
/*
* Quiesce the connection mgmt handlers before we start tearing
* things down. We don't hold the mutex for the entire
* duration of the shutdown operation, else we may be
* deadlocking with the CM handler. Instead, the CM event
* handler is supposed to check for state DISCONNECTING
*/
mutex_lock(&conn->c_cm_lock);
if (!rds_conn_transition(conn, RDS_CONN_UP, RDS_CONN_DISCONNECTING)
&& !rds_conn_transition(conn, RDS_CONN_ERROR, RDS_CONN_DISCONNECTING)) {
rds_conn_error(conn, "shutdown called in state %d\n",
atomic_read(&conn->c_state));
mutex_unlock(&conn->c_cm_lock);
return;
}
mutex_unlock(&conn->c_cm_lock);
wait_event(conn->c_waitq,
!test_bit(RDS_IN_XMIT, &conn->c_flags));
wait_event(conn->c_waitq,
!test_bit(RDS_RECV_REFILL, &conn->c_flags));
conn->c_trans->conn_shutdown(conn);
rds_conn_reset(conn);
if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) {
/* This can happen - eg when we're in the middle of tearing
* down the connection, and someone unloads the rds module.
* Quite reproduceable with loopback connections.
* Mostly harmless.
*/
rds_conn_error(conn,
"%s: failed to transition to state DOWN, "
"current state is %d\n",
__func__,
atomic_read(&conn->c_state));
return;
}
}
/* Then reconnect if it's still live.
* The passive side of an IB loopback connection is never added
* to the conn hash, so we never trigger a reconnect on this
* conn - the reconnect is always triggered by the active peer. */
cancel_delayed_work_sync(&conn->c_conn_w);
rcu_read_lock();
if (!hlist_unhashed(&conn->c_hash_node)) {
rcu_read_unlock();
if (conn->c_trans->t_type != RDS_TRANS_TCP ||
conn->c_outgoing == 1)
rds_queue_reconnect(conn);
} else {
rcu_read_unlock();
}
}
/*
* Stop and free a connection.
*
* This can only be used in very limited circumstances. It assumes that once
* the conn has been shutdown that no one else is referencing the connection.
* We can only ensure this in the rmmod path in the current code.
*/
void rds_conn_destroy(struct rds_connection *conn)
{
struct rds_message *rm, *rtmp;
unsigned long flags;
rdsdebug("freeing conn %p for %pI4 -> "
"%pI4\n", conn, &conn->c_laddr,
&conn->c_faddr);
/* Ensure conn will not be scheduled for reconnect */
spin_lock_irq(&rds_conn_lock);
hlist_del_init_rcu(&conn->c_hash_node);
spin_unlock_irq(&rds_conn_lock);
synchronize_rcu();
/* shut the connection down */
rds_conn_drop(conn);
flush_work(&conn->c_down_w);
/* make sure lingering queued work won't try to ref the conn */
cancel_delayed_work_sync(&conn->c_send_w);
cancel_delayed_work_sync(&conn->c_recv_w);
/* tear down queued messages */
list_for_each_entry_safe(rm, rtmp,
&conn->c_send_queue,
m_conn_item) {
list_del_init(&rm->m_conn_item);
BUG_ON(!list_empty(&rm->m_sock_item));
rds_message_put(rm);
}
if (conn->c_xmit_rm)
rds_message_put(conn->c_xmit_rm);
conn->c_trans->conn_free(conn->c_transport_data);
/*
* The congestion maps aren't freed up here. They're
* freed by rds_cong_exit() after all the connections
* have been freed.
*/
rds_cong_remove_conn(conn);
BUG_ON(!list_empty(&conn->c_retrans));
kmem_cache_free(rds_conn_slab, conn);
spin_lock_irqsave(&rds_conn_lock, flags);
rds_conn_count--;
spin_unlock_irqrestore(&rds_conn_lock, flags);
}
EXPORT_SYMBOL_GPL(rds_conn_destroy);
static void rds_conn_message_info(struct socket *sock, unsigned int len,
struct rds_info_iterator *iter,
struct rds_info_lengths *lens,
int want_send)
{
struct hlist_head *head;
struct list_head *list;
struct rds_connection *conn;
struct rds_message *rm;
unsigned int total = 0;
unsigned long flags;
size_t i;
len /= sizeof(struct rds_info_message);
rcu_read_lock();
for (i = 0, head = rds_conn_hash; i < ARRAY_SIZE(rds_conn_hash);
i++, head++) {
hlist_for_each_entry_rcu(conn, head, c_hash_node) {
if (want_send)
list = &conn->c_send_queue;
else
list = &conn->c_retrans;
spin_lock_irqsave(&conn->c_lock, flags);
/* XXX too lazy to maintain counts.. */
list_for_each_entry(rm, list, m_conn_item) {
total++;
if (total <= len)
rds_inc_info_copy(&rm->m_inc, iter,
conn->c_laddr,
conn->c_faddr, 0);
}
spin_unlock_irqrestore(&conn->c_lock, flags);
}
}
rcu_read_unlock();
lens->nr = total;
lens->each = sizeof(struct rds_info_message);
}
static void rds_conn_message_info_send(struct socket *sock, unsigned int len,
struct rds_info_iterator *iter,
struct rds_info_lengths *lens)
{
rds_conn_message_info(sock, len, iter, lens, 1);
}
static void rds_conn_message_info_retrans(struct socket *sock,
unsigned int len,
struct rds_info_iterator *iter,
struct rds_info_lengths *lens)
{
rds_conn_message_info(sock, len, iter, lens, 0);
}
void rds_for_each_conn_info(struct socket *sock, unsigned int len,
struct rds_info_iterator *iter,
struct rds_info_lengths *lens,
int (*visitor)(struct rds_connection *, void *),
size_t item_len)
{
uint64_t buffer[(item_len + 7) / 8];
struct hlist_head *head;
struct rds_connection *conn;
size_t i;
rcu_read_lock();
lens->nr = 0;
lens->each = item_len;
for (i = 0, head = rds_conn_hash; i < ARRAY_SIZE(rds_conn_hash);
i++, head++) {
hlist_for_each_entry_rcu(conn, head, c_hash_node) {
/* XXX no c_lock usage.. */
if (!visitor(conn, buffer))
continue;
/* We copy as much as we can fit in the buffer,
* but we count all items so that the caller
* can resize the buffer. */
if (len >= item_len) {
rds_info_copy(iter, buffer, item_len);
len -= item_len;
}
lens->nr++;
}
}
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rds_for_each_conn_info);
static int rds_conn_info_visitor(struct rds_connection *conn,
void *buffer)
{
struct rds_info_connection *cinfo = buffer;
cinfo->next_tx_seq = conn->c_next_tx_seq;
cinfo->next_rx_seq = conn->c_next_rx_seq;
cinfo->laddr = conn->c_laddr;
cinfo->faddr = conn->c_faddr;
strncpy(cinfo->transport, conn->c_trans->t_name,
sizeof(cinfo->transport));
cinfo->flags = 0;
rds_conn_info_set(cinfo->flags, test_bit(RDS_IN_XMIT, &conn->c_flags),
SENDING);
/* XXX Future: return the state rather than these funky bits */
rds_conn_info_set(cinfo->flags,
atomic_read(&conn->c_state) == RDS_CONN_CONNECTING,
CONNECTING);
rds_conn_info_set(cinfo->flags,
atomic_read(&conn->c_state) == RDS_CONN_UP,
CONNECTED);
return 1;
}
static void rds_conn_info(struct socket *sock, unsigned int len,
struct rds_info_iterator *iter,
struct rds_info_lengths *lens)
{
rds_for_each_conn_info(sock, len, iter, lens,
rds_conn_info_visitor,
sizeof(struct rds_info_connection));
}
int rds_conn_init(void)
{
rds_conn_slab = kmem_cache_create("rds_connection",
sizeof(struct rds_connection),
0, 0, NULL);
if (!rds_conn_slab)
return -ENOMEM;
rds_info_register_func(RDS_INFO_CONNECTIONS, rds_conn_info);
rds_info_register_func(RDS_INFO_SEND_MESSAGES,
rds_conn_message_info_send);
rds_info_register_func(RDS_INFO_RETRANS_MESSAGES,
rds_conn_message_info_retrans);
return 0;
}
void rds_conn_exit(void)
{
rds_loop_exit();
WARN_ON(!hlist_empty(rds_conn_hash));
kmem_cache_destroy(rds_conn_slab);
rds_info_deregister_func(RDS_INFO_CONNECTIONS, rds_conn_info);
rds_info_deregister_func(RDS_INFO_SEND_MESSAGES,
rds_conn_message_info_send);
rds_info_deregister_func(RDS_INFO_RETRANS_MESSAGES,
rds_conn_message_info_retrans);
}
/*
* Force a disconnect
*/
void rds_conn_drop(struct rds_connection *conn)
{
atomic_set(&conn->c_state, RDS_CONN_ERROR);
queue_work(rds_wq, &conn->c_down_w);
}
EXPORT_SYMBOL_GPL(rds_conn_drop);
/*
* If the connection is down, trigger a connect. We may have scheduled a
* delayed reconnect however - in this case we should not interfere.
*/
void rds_conn_connect_if_down(struct rds_connection *conn)
{
if (rds_conn_state(conn) == RDS_CONN_DOWN &&
!test_and_set_bit(RDS_RECONNECT_PENDING, &conn->c_flags))
queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
}
EXPORT_SYMBOL_GPL(rds_conn_connect_if_down);
/*
* An error occurred on the connection
*/
void
__rds_conn_error(struct rds_connection *conn, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vprintk(fmt, ap);
va_end(ap);
rds_conn_drop(conn);
}