/*
* 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/random.h>
#include <linux/export.h>
#include "rds.h"
/*
* All of connection management is simplified by serializing it through
* work queues that execute in a connection managing thread.
*
* TCP wants to send acks through sendpage() in response to data_ready(),
* but it needs a process context to do so.
*
* The receive paths need to allocate but can't drop packets (!) so we have
* a thread around to block allocating if the receive fast path sees an
* allocation failure.
*/
/* Grand Unified Theory of connection life cycle:
* At any point in time, the connection can be in one of these states:
* DOWN, CONNECTING, UP, DISCONNECTING, ERROR
*
* The following transitions are possible:
* ANY -> ERROR
* UP -> DISCONNECTING
* ERROR -> DISCONNECTING
* DISCONNECTING -> DOWN
* DOWN -> CONNECTING
* CONNECTING -> UP
*
* Transition to state DISCONNECTING/DOWN:
* - Inside the shutdown worker; synchronizes with xmit path
* through RDS_IN_XMIT, and with connection management callbacks
* via c_cm_lock.
*
* For receive callbacks, we rely on the underlying transport
* (TCP, IB/RDMA) to provide the necessary synchronisation.
*/
struct workqueue_struct *rds_wq;
EXPORT_SYMBOL_GPL(rds_wq);
void rds_connect_path_complete(struct rds_conn_path *cp, int curr)
{
if (!rds_conn_path_transition(cp, curr, RDS_CONN_UP)) {
printk(KERN_WARNING "%s: Cannot transition to state UP, "
"current state is %d\n",
__func__,
atomic_read(&cp->cp_state));
rds_conn_path_drop(cp, false);
return;
}
rdsdebug("conn %p for %pI6c to %pI6c complete\n",
cp->cp_conn, &cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr);
cp->cp_reconnect_jiffies = 0;
set_bit(0, &cp->cp_conn->c_map_queued);
rcu_read_lock();
if (!rds_destroy_pending(cp->cp_conn)) {
queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
}
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rds_connect_path_complete);
void rds_connect_complete(struct rds_connection *conn)
{
rds_connect_path_complete(&conn->c_path[0], RDS_CONN_CONNECTING);
}
EXPORT_SYMBOL_GPL(rds_connect_complete);
/*
* This random exponential backoff is relied on to eventually resolve racing
* connects.
*
* If connect attempts race then both parties drop both connections and come
* here to wait for a random amount of time before trying again. Eventually
* the backoff range will be so much greater than the time it takes to
* establish a connection that one of the pair will establish the connection
* before the other's random delay fires.
*
* Connection attempts that arrive while a connection is already established
* are also considered to be racing connects. This lets a connection from
* a rebooted machine replace an existing stale connection before the transport
* notices that the connection has failed.
*
* We should *always* start with a random backoff; otherwise a broken connection
* will always take several iterations to be re-established.
*/
void rds_queue_reconnect(struct rds_conn_path *cp)
{
unsigned long rand;
struct rds_connection *conn = cp->cp_conn;
rdsdebug("conn %p for %pI6c to %pI6c reconnect jiffies %lu\n",
conn, &conn->c_laddr, &conn->c_faddr,
cp->cp_reconnect_jiffies);
/* let peer with smaller addr initiate reconnect, to avoid duels */
if (conn->c_trans->t_type == RDS_TRANS_TCP &&
rds_addr_cmp(&conn->c_laddr, &conn->c_faddr) >= 0)
return;
set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
if (cp->cp_reconnect_jiffies == 0) {
cp->cp_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
rcu_read_lock();
if (!rds_destroy_pending(cp->cp_conn))
queue_delayed_work(rds_wq, &cp->cp_conn_w, 0);
rcu_read_unlock();
return;
}
get_random_bytes(&rand, sizeof(rand));
rdsdebug("%lu delay %lu ceil conn %p for %pI6c -> %pI6c\n",
rand % cp->cp_reconnect_jiffies, cp->cp_reconnect_jiffies,
conn, &conn->c_laddr, &conn->c_faddr);
rcu_read_lock();
if (!rds_destroy_pending(cp->cp_conn))
queue_delayed_work(rds_wq, &cp->cp_conn_w,
rand % cp->cp_reconnect_jiffies);
rcu_read_unlock();
cp->cp_reconnect_jiffies = min(cp->cp_reconnect_jiffies * 2,
rds_sysctl_reconnect_max_jiffies);
}
void rds_connect_worker(struct work_struct *work)
{
struct rds_conn_path *cp = container_of(work,
struct rds_conn_path,
cp_conn_w.work);
struct rds_connection *conn = cp->cp_conn;
int ret;
if (cp->cp_index > 0 &&
rds_addr_cmp(&cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr) >= 0)
return;
clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
ret = rds_conn_path_transition(cp, RDS_CONN_DOWN, RDS_CONN_CONNECTING);
if (ret) {
ret = conn->c_trans->conn_path_connect(cp);
rdsdebug("conn %p for %pI6c to %pI6c dispatched, ret %d\n",
conn, &conn->c_laddr, &conn->c_faddr, ret);
if (ret) {
if (rds_conn_path_transition(cp,
RDS_CONN_CONNECTING,
RDS_CONN_DOWN))
rds_queue_reconnect(cp);
else
rds_conn_path_error(cp, "connect failed\n");
}
}
}
void rds_send_worker(struct work_struct *work)
{
struct rds_conn_path *cp = container_of(work,
struct rds_conn_path,
cp_send_w.work);
int ret;
if (rds_conn_path_state(cp) == RDS_CONN_UP) {
clear_bit(RDS_LL_SEND_FULL, &cp->cp_flags);
ret = rds_send_xmit(cp);
cond_resched();
rdsdebug("conn %p ret %d\n", cp->cp_conn, ret);
switch (ret) {
case -EAGAIN:
rds_stats_inc(s_send_immediate_retry);
queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
break;
case -ENOMEM:
rds_stats_inc(s_send_delayed_retry);
queue_delayed_work(rds_wq, &cp->cp_send_w, 2);
default:
break;
}
}
}
void rds_recv_worker(struct work_struct *work)
{
struct rds_conn_path *cp = container_of(work,
struct rds_conn_path,
cp_recv_w.work);
int ret;
if (rds_conn_path_state(cp) == RDS_CONN_UP) {
ret = cp->cp_conn->c_trans->recv_path(cp);
rdsdebug("conn %p ret %d\n", cp->cp_conn, ret);
switch (ret) {
case -EAGAIN:
rds_stats_inc(s_recv_immediate_retry);
queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
break;
case -ENOMEM:
rds_stats_inc(s_recv_delayed_retry);
queue_delayed_work(rds_wq, &cp->cp_recv_w, 2);
default:
break;
}
}
}
void rds_shutdown_worker(struct work_struct *work)
{
struct rds_conn_path *cp = container_of(work,
struct rds_conn_path,
cp_down_w);
rds_conn_shutdown(cp);
}
void rds_threads_exit(void)
{
destroy_workqueue(rds_wq);
}
int rds_threads_init(void)
{
rds_wq = create_singlethread_workqueue("krdsd");
if (!rds_wq)
return -ENOMEM;
return 0;
}
/* Compare two IPv6 addresses. Return 0 if the two addresses are equal.
* Return 1 if the first is greater. Return -1 if the second is greater.
*/
int rds_addr_cmp(const struct in6_addr *addr1,
const struct in6_addr *addr2)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
const __be64 *a1, *a2;
u64 x, y;
a1 = (__be64 *)addr1;
a2 = (__be64 *)addr2;
if (*a1 != *a2) {
if (be64_to_cpu(*a1) < be64_to_cpu(*a2))
return -1;
else
return 1;
} else {
x = be64_to_cpu(*++a1);
y = be64_to_cpu(*++a2);
if (x < y)
return -1;
else if (x > y)
return 1;
else
return 0;
}
#else
u32 a, b;
int i;
for (i = 0; i < 4; i++) {
if (addr1->s6_addr32[i] != addr2->s6_addr32[i]) {
a = ntohl(addr1->s6_addr32[i]);
b = ntohl(addr2->s6_addr32[i]);
if (a < b)
return -1;
else if (a > b)
return 1;
}
}
return 0;
#endif
}
EXPORT_SYMBOL_GPL(rds_addr_cmp);
