net/rxrpc/conn_object.c - third_party/linux - Git at Google

 /* RxRPC virtual connection handler, common bits.
  *
  * Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version
  * 2 of the License, or (at your option) any later version.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/net.h>
 #include <linux/skbuff.h>
 #include "ar-internal.h"

 /*
  * Time till a connection expires after last use (in seconds).
  */
 unsigned int __read_mostly rxrpc_connection_expiry = 10 * 60;
 unsigned int __read_mostly rxrpc_closed_conn_expiry = 10;

 static void rxrpc_destroy_connection(struct rcu_head *);

 static void rxrpc_connection_timer(struct timer_list *timer)
 {
 	struct rxrpc_connection *conn =
 		container_of(timer, struct rxrpc_connection, timer);

 	rxrpc_queue_conn(conn);
 }

 /*
  * allocate a new connection
  */
 struct rxrpc_connection *rxrpc_alloc_connection(gfp_t gfp)
 {
 	struct rxrpc_connection *conn;

 	_enter("");

 	conn = kzalloc(sizeof(struct rxrpc_connection), gfp);
 	if (conn) {
 		INIT_LIST_HEAD(&conn->cache_link);
 		spin_lock_init(&conn->channel_lock);
 		INIT_LIST_HEAD(&conn->waiting_calls);
 		timer_setup(&conn->timer, &rxrpc_connection_timer, 0);
 		INIT_WORK(&conn->processor, &rxrpc_process_connection);
 		INIT_LIST_HEAD(&conn->proc_link);
 		INIT_LIST_HEAD(&conn->link);
 		skb_queue_head_init(&conn->rx_queue);
 		conn->security = &rxrpc_no_security;
 		spin_lock_init(&conn->state_lock);
 		conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
 		conn->size_align = 4;
 		conn->idle_timestamp = jiffies;
 	}

 	_leave(" = %p{%d}", conn, conn ? conn->debug_id : 0);
 	return conn;
 }

 /*
  * Look up a connection in the cache by protocol parameters.
  *
  * If successful, a pointer to the connection is returned, but no ref is taken.
  * NULL is returned if there is no match.
  *
  * The caller must be holding the RCU read lock.
  */
 struct rxrpc_connection *rxrpc_find_connection_rcu(struct rxrpc_local *local,
 						   struct sk_buff *skb)
 {
 	struct rxrpc_connection *conn;
 	struct rxrpc_conn_proto k;
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct sockaddr_rxrpc srx;
 	struct rxrpc_peer *peer;

 	_enter(",%x", sp->hdr.cid & RXRPC_CIDMASK);

 	if (rxrpc_extract_addr_from_skb(local, &srx, skb) < 0)
 		goto not_found;

 	k.epoch	= sp->hdr.epoch;
 	k.cid	= sp->hdr.cid & RXRPC_CIDMASK;

 	/* We may have to handle mixing IPv4 and IPv6 */
 	if (srx.transport.family != local->srx.transport.family) {
 		pr_warn_ratelimited("AF_RXRPC: Protocol mismatch %u not %u\n",
 				    srx.transport.family,
 				    local->srx.transport.family);
 		goto not_found;
 	}

 	k.epoch	= sp->hdr.epoch;
 	k.cid	= sp->hdr.cid & RXRPC_CIDMASK;

 	if (sp->hdr.flags & RXRPC_CLIENT_INITIATED) {
 		/* We need to look up service connections by the full protocol
 		 * parameter set.  We look up the peer first as an intermediate
 		 * step and then the connection from the peer's tree.
 		 */
 		peer = rxrpc_lookup_peer_rcu(local, &srx);
 		if (!peer)
 			goto not_found;
 		conn = rxrpc_find_service_conn_rcu(peer, skb);
 		if (!conn || atomic_read(&conn->usage) == 0)
 			goto not_found;
 		_leave(" = %p", conn);
 		return conn;
 	} else {
 		/* Look up client connections by connection ID alone as their
 		 * IDs are unique for this machine.
 		 */
 		conn = idr_find(&rxrpc_client_conn_ids,
 				sp->hdr.cid >> RXRPC_CIDSHIFT);
 		if (!conn || atomic_read(&conn->usage) == 0) {
 			_debug("no conn");
 			goto not_found;
 		}

 		if (conn->proto.epoch != k.epoch ||
 		    conn->params.local != local)
 			goto not_found;

 		peer = conn->params.peer;
 		switch (srx.transport.family) {
 		case AF_INET:
 			if (peer->srx.transport.sin.sin_port !=
 			    srx.transport.sin.sin_port ||
 			    peer->srx.transport.sin.sin_addr.s_addr !=
 			    srx.transport.sin.sin_addr.s_addr)
 				goto not_found;
 			break;
 #ifdef CONFIG_AF_RXRPC_IPV6
 		case AF_INET6:
 			if (peer->srx.transport.sin6.sin6_port !=
 			    srx.transport.sin6.sin6_port ||
 			    memcmp(&peer->srx.transport.sin6.sin6_addr,
 				   &srx.transport.sin6.sin6_addr,
 				   sizeof(struct in6_addr)) != 0)
 				goto not_found;
 			break;
 #endif
 		default:
 			BUG();
 		}

 		_leave(" = %p", conn);
 		return conn;
 	}

 not_found:
 	_leave(" = NULL");
 	return NULL;
 }

 /*
  * Disconnect a call and clear any channel it occupies when that call
  * terminates.  The caller must hold the channel_lock and must release the
  * call's ref on the connection.
  */
 void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
 			     struct rxrpc_call *call)
 {
 	struct rxrpc_channel *chan =
 		&conn->channels[call->cid & RXRPC_CHANNELMASK];

 	_enter("%d,%x", conn->debug_id, call->cid);

 	if (rcu_access_pointer(chan->call) == call) {
 		/* Save the result of the call so that we can repeat it if necessary
 		 * through the channel, whilst disposing of the actual call record.
 		 */
 		trace_rxrpc_disconnect_call(call);
 		switch (call->completion) {
 		case RXRPC_CALL_SUCCEEDED:
 			chan->last_seq = call->rx_hard_ack;
 			chan->last_type = RXRPC_PACKET_TYPE_ACK;
 			break;
 		case RXRPC_CALL_LOCALLY_ABORTED:
 			chan->last_abort = call->abort_code;
 			chan->last_type = RXRPC_PACKET_TYPE_ABORT;
 			break;
 		default:
 			chan->last_abort = RX_USER_ABORT;
 			chan->last_type = RXRPC_PACKET_TYPE_ABORT;
 			break;
 		}

 		/* Sync with rxrpc_conn_retransmit(). */
 		smp_wmb();
 		chan->last_call = chan->call_id;
 		chan->call_id = chan->call_counter;

 		rcu_assign_pointer(chan->call, NULL);
 	}

 	_leave("");
 }

 /*
  * Disconnect a call and clear any channel it occupies when that call
  * terminates.
  */
 void rxrpc_disconnect_call(struct rxrpc_call *call)
 {
 	struct rxrpc_connection *conn = call->conn;

 	call->peer->cong_cwnd = call->cong_cwnd;

 	spin_lock_bh(&conn->params.peer->lock);
 	hlist_del_init(&call->error_link);
 	spin_unlock_bh(&conn->params.peer->lock);

 	if (rxrpc_is_client_call(call))
 		return rxrpc_disconnect_client_call(call);

 	spin_lock(&conn->channel_lock);
 	__rxrpc_disconnect_call(conn, call);
 	spin_unlock(&conn->channel_lock);

 	call->conn = NULL;
 	conn->idle_timestamp = jiffies;
 	rxrpc_put_connection(conn);
 }

 /*
  * Kill off a connection.
  */
 void rxrpc_kill_connection(struct rxrpc_connection *conn)
 {
 	struct rxrpc_net *rxnet = conn->params.local->rxnet;

 	ASSERT(!rcu_access_pointer(conn->channels[0].call) &&
 	       !rcu_access_pointer(conn->channels[1].call) &&
 	       !rcu_access_pointer(conn->channels[2].call) &&
 	       !rcu_access_pointer(conn->channels[3].call));
 	ASSERT(list_empty(&conn->cache_link));

 	write_lock(&rxnet->conn_lock);
 	list_del_init(&conn->proc_link);
 	write_unlock(&rxnet->conn_lock);

 	/* Drain the Rx queue.  Note that even though we've unpublished, an
 	 * incoming packet could still be being added to our Rx queue, so we
 	 * will need to drain it again in the RCU cleanup handler.
 	 */
 	rxrpc_purge_queue(&conn->rx_queue);

 	/* Leave final destruction to RCU.  The connection processor work item
 	 * must carry a ref on the connection to prevent us getting here whilst
 	 * it is queued or running.
 	 */
 	call_rcu(&conn->rcu, rxrpc_destroy_connection);
 }

 /*
  * Queue a connection's work processor, getting a ref to pass to the work
  * queue.
  */
 bool rxrpc_queue_conn(struct rxrpc_connection *conn)
 {
 	const void *here = __builtin_return_address(0);
 	int n = __atomic_add_unless(&conn->usage, 1, 0);
 	if (n == 0)
 		return false;
 	if (rxrpc_queue_work(&conn->processor))
 		trace_rxrpc_conn(conn, rxrpc_conn_queued, n + 1, here);
 	else
 		rxrpc_put_connection(conn);
 	return true;
 }

 /*
  * Note the re-emergence of a connection.
  */
 void rxrpc_see_connection(struct rxrpc_connection *conn)
 {
 	const void *here = __builtin_return_address(0);
 	if (conn) {
 		int n = atomic_read(&conn->usage);

 		trace_rxrpc_conn(conn, rxrpc_conn_seen, n, here);
 	}
 }

 /*
  * Get a ref on a connection.
  */
 void rxrpc_get_connection(struct rxrpc_connection *conn)
 {
 	const void *here = __builtin_return_address(0);
 	int n = atomic_inc_return(&conn->usage);

 	trace_rxrpc_conn(conn, rxrpc_conn_got, n, here);
 }

 /*
  * Try to get a ref on a connection.
  */
 struct rxrpc_connection *
 rxrpc_get_connection_maybe(struct rxrpc_connection *conn)
 {
 	const void *here = __builtin_return_address(0);

 	if (conn) {
 		int n = __atomic_add_unless(&conn->usage, 1, 0);
 		if (n > 0)
 			trace_rxrpc_conn(conn, rxrpc_conn_got, n + 1, here);
 		else
 			conn = NULL;
 	}
 	return conn;
 }

 /*
  * Set the service connection reap timer.
  */
 static void rxrpc_set_service_reap_timer(struct rxrpc_net *rxnet,
 					 unsigned long reap_at)
 {
 	if (rxnet->live)
 		timer_reduce(&rxnet->service_conn_reap_timer, reap_at);
 }

 /*
  * Release a service connection
  */
 void rxrpc_put_service_conn(struct rxrpc_connection *conn)
 {
 	const void *here = __builtin_return_address(0);
 	int n;

 	n = atomic_dec_return(&conn->usage);
 	trace_rxrpc_conn(conn, rxrpc_conn_put_service, n, here);
 	ASSERTCMP(n, >=, 0);
 	if (n == 1)
 		rxrpc_set_service_reap_timer(conn->params.local->rxnet,
 					     jiffies + rxrpc_connection_expiry);
 }

 /*
  * destroy a virtual connection
  */
 static void rxrpc_destroy_connection(struct rcu_head *rcu)
 {
 	struct rxrpc_connection *conn =
 		container_of(rcu, struct rxrpc_connection, rcu);

 	_enter("{%d,u=%d}", conn->debug_id, atomic_read(&conn->usage));

 	ASSERTCMP(atomic_read(&conn->usage), ==, 0);

 	_net("DESTROY CONN %d", conn->debug_id);

 	del_timer_sync(&conn->timer);
 	rxrpc_purge_queue(&conn->rx_queue);

 	conn->security->clear(conn);
 	key_put(conn->params.key);
 	key_put(conn->server_key);
 	rxrpc_put_peer(conn->params.peer);

 	if (atomic_dec_and_test(&conn->params.local->rxnet->nr_conns))
 		wake_up_var(&conn->params.local->rxnet->nr_conns);
 	rxrpc_put_local(conn->params.local);

 	kfree(conn);
 	_leave("");
 }

 /*
  * reap dead service connections
  */
 void rxrpc_service_connection_reaper(struct work_struct *work)
 {
 	struct rxrpc_connection *conn, *_p;
 	struct rxrpc_net *rxnet =
 		container_of(work, struct rxrpc_net, service_conn_reaper);
 	unsigned long expire_at, earliest, idle_timestamp, now;

 	LIST_HEAD(graveyard);

 	_enter("");

 	now = jiffies;
 	earliest = now + MAX_JIFFY_OFFSET;

 	write_lock(&rxnet->conn_lock);
 	list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
 		ASSERTCMP(atomic_read(&conn->usage), >, 0);
 		if (likely(atomic_read(&conn->usage) > 1))
 			continue;
 		if (conn->state == RXRPC_CONN_SERVICE_PREALLOC)
 			continue;

 		if (rxnet->live) {
 			idle_timestamp = READ_ONCE(conn->idle_timestamp);
 			expire_at = idle_timestamp + rxrpc_connection_expiry * HZ;
 			if (conn->params.local->service_closed)
 				expire_at = idle_timestamp + rxrpc_closed_conn_expiry * HZ;

 			_debug("reap CONN %d { u=%d,t=%ld }",
 			       conn->debug_id, atomic_read(&conn->usage),
 			       (long)expire_at - (long)now);

 			if (time_before(now, expire_at)) {
 				if (time_before(expire_at, earliest))
 					earliest = expire_at;
 				continue;
 			}
 		}

 		/* The usage count sits at 1 whilst the object is unused on the
 		 * list; we reduce that to 0 to make the object unavailable.
 		 */
 		if (atomic_cmpxchg(&conn->usage, 1, 0) != 1)
 			continue;
 		trace_rxrpc_conn(conn, rxrpc_conn_reap_service, 0, NULL);

 		if (rxrpc_conn_is_client(conn))
 			BUG();
 		else
 			rxrpc_unpublish_service_conn(conn);

 		list_move_tail(&conn->link, &graveyard);
 	}
 	write_unlock(&rxnet->conn_lock);

 	if (earliest != now + MAX_JIFFY_OFFSET) {
 		_debug("reschedule reaper %ld", (long)earliest - (long)now);
 		ASSERT(time_after(earliest, now));
 		rxrpc_set_service_reap_timer(rxnet, earliest);
 	}

 	while (!list_empty(&graveyard)) {
 		conn = list_entry(graveyard.next, struct rxrpc_connection,
 				  link);
 		list_del_init(&conn->link);

 		ASSERTCMP(atomic_read(&conn->usage), ==, 0);
 		rxrpc_kill_connection(conn);
 	}

 	_leave("");
 }

 /*
  * preemptively destroy all the service connection records rather than
  * waiting for them to time out
  */
 void rxrpc_destroy_all_connections(struct rxrpc_net *rxnet)
 {
 	struct rxrpc_connection *conn, *_p;
 	bool leak = false;

 	_enter("");

 	atomic_dec(&rxnet->nr_conns);
 	rxrpc_destroy_all_client_connections(rxnet);

 	del_timer_sync(&rxnet->service_conn_reap_timer);
 	rxrpc_queue_work(&rxnet->service_conn_reaper);
 	flush_workqueue(rxrpc_workqueue);

 	write_lock(&rxnet->conn_lock);
 	list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
 		pr_err("AF_RXRPC: Leaked conn %p {%d}\n",
 		       conn, atomic_read(&conn->usage));
 		leak = true;
 	}
 	write_unlock(&rxnet->conn_lock);
 	BUG_ON(leak);

 	ASSERT(list_empty(&rxnet->conn_proc_list));

 	/* We need to wait for the connections to be destroyed by RCU as they
 	 * pin things that we still need to get rid of.
 	 */
 	wait_var_event(&rxnet->nr_conns, !atomic_read(&rxnet->nr_conns));
 	_leave("");
 }
	/* RxRPC virtual connection handler, common bits.
	*
	* Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/net.h>
	#include <linux/skbuff.h>
	#include "ar-internal.h"

	/*
	* Time till a connection expires after last use (in seconds).
	*/
	unsigned int __read_mostly rxrpc_connection_expiry = 10 * 60;
	unsigned int __read_mostly rxrpc_closed_conn_expiry = 10;

	static void rxrpc_destroy_connection(struct rcu_head *);

	static void rxrpc_connection_timer(struct timer_list *timer)
	{
	struct rxrpc_connection *conn =
	container_of(timer, struct rxrpc_connection, timer);

	rxrpc_queue_conn(conn);
	}

	/*
	* allocate a new connection
	*/
	struct rxrpc_connection *rxrpc_alloc_connection(gfp_t gfp)
	{
	struct rxrpc_connection *conn;

	_enter("");

	conn = kzalloc(sizeof(struct rxrpc_connection), gfp);
	if (conn) {
	INIT_LIST_HEAD(&conn->cache_link);
	spin_lock_init(&conn->channel_lock);
	INIT_LIST_HEAD(&conn->waiting_calls);
	timer_setup(&conn->timer, &rxrpc_connection_timer, 0);
	INIT_WORK(&conn->processor, &rxrpc_process_connection);
	INIT_LIST_HEAD(&conn->proc_link);
	INIT_LIST_HEAD(&conn->link);
	skb_queue_head_init(&conn->rx_queue);
	conn->security = &rxrpc_no_security;
	spin_lock_init(&conn->state_lock);
	conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
	conn->size_align = 4;
	conn->idle_timestamp = jiffies;
	}

	_leave(" = %p{%d}", conn, conn ? conn->debug_id : 0);
	return conn;
	}

	/*
	* Look up a connection in the cache by protocol parameters.
	*
	* If successful, a pointer to the connection is returned, but no ref is taken.
	* NULL is returned if there is no match.
	*
	* The caller must be holding the RCU read lock.
	*/
	struct rxrpc_connection rxrpc_find_connection_rcu(struct rxrpc_local local,
	struct sk_buff *skb)
	{
	struct rxrpc_connection *conn;
	struct rxrpc_conn_proto k;
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	struct sockaddr_rxrpc srx;
	struct rxrpc_peer *peer;

	_enter(",%x", sp->hdr.cid & RXRPC_CIDMASK);

	if (rxrpc_extract_addr_from_skb(local, &srx, skb) < 0)
	goto not_found;

	k.epoch = sp->hdr.epoch;
	k.cid = sp->hdr.cid & RXRPC_CIDMASK;

	/* We may have to handle mixing IPv4 and IPv6 */
	if (srx.transport.family != local->srx.transport.family) {
	pr_warn_ratelimited("AF_RXRPC: Protocol mismatch %u not %u\n",
	srx.transport.family,
	local->srx.transport.family);
	goto not_found;
	}

	k.epoch = sp->hdr.epoch;
	k.cid = sp->hdr.cid & RXRPC_CIDMASK;

	if (sp->hdr.flags & RXRPC_CLIENT_INITIATED) {
	/* We need to look up service connections by the full protocol
	* parameter set. We look up the peer first as an intermediate
	* step and then the connection from the peer's tree.
	*/
	peer = rxrpc_lookup_peer_rcu(local, &srx);
	if (!peer)
	goto not_found;
	conn = rxrpc_find_service_conn_rcu(peer, skb);
	if (!conn \|\| atomic_read(&conn->usage) == 0)
	goto not_found;
	_leave(" = %p", conn);
	return conn;
	} else {
	/* Look up client connections by connection ID alone as their
	* IDs are unique for this machine.
	*/
	conn = idr_find(&rxrpc_client_conn_ids,
	sp->hdr.cid >> RXRPC_CIDSHIFT);
	if (!conn \|\| atomic_read(&conn->usage) == 0) {
	_debug("no conn");
	goto not_found;
	}

	if (conn->proto.epoch != k.epoch \|\|
	conn->params.local != local)
	goto not_found;

	peer = conn->params.peer;
	switch (srx.transport.family) {
	case AF_INET:
	if (peer->srx.transport.sin.sin_port !=
	srx.transport.sin.sin_port \|\|
	peer->srx.transport.sin.sin_addr.s_addr !=
	srx.transport.sin.sin_addr.s_addr)
	goto not_found;
	break;
	#ifdef CONFIG_AF_RXRPC_IPV6
	case AF_INET6:
	if (peer->srx.transport.sin6.sin6_port !=
	srx.transport.sin6.sin6_port \|\|
	memcmp(&peer->srx.transport.sin6.sin6_addr,
	&srx.transport.sin6.sin6_addr,
	sizeof(struct in6_addr)) != 0)
	goto not_found;
	break;
	#endif
	default:
	BUG();
	}

	_leave(" = %p", conn);
	return conn;
	}

	not_found:
	_leave(" = NULL");
	return NULL;
	}

	/*
	* Disconnect a call and clear any channel it occupies when that call
	* terminates. The caller must hold the channel_lock and must release the
	* call's ref on the connection.
	*/
	void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
	struct rxrpc_call *call)
	{
	struct rxrpc_channel *chan =
	&conn->channels[call->cid & RXRPC_CHANNELMASK];

	_enter("%d,%x", conn->debug_id, call->cid);

	if (rcu_access_pointer(chan->call) == call) {
	/* Save the result of the call so that we can repeat it if necessary
	* through the channel, whilst disposing of the actual call record.
	*/
	trace_rxrpc_disconnect_call(call);
	switch (call->completion) {
	case RXRPC_CALL_SUCCEEDED:
	chan->last_seq = call->rx_hard_ack;
	chan->last_type = RXRPC_PACKET_TYPE_ACK;
	break;
	case RXRPC_CALL_LOCALLY_ABORTED:
	chan->last_abort = call->abort_code;
	chan->last_type = RXRPC_PACKET_TYPE_ABORT;
	break;
	default:
	chan->last_abort = RX_USER_ABORT;
	chan->last_type = RXRPC_PACKET_TYPE_ABORT;
	break;
	}

	/* Sync with rxrpc_conn_retransmit(). */
	smp_wmb();
	chan->last_call = chan->call_id;
	chan->call_id = chan->call_counter;

	rcu_assign_pointer(chan->call, NULL);
	}

	_leave("");
	}

	/*
	* Disconnect a call and clear any channel it occupies when that call
	* terminates.
	*/
	void rxrpc_disconnect_call(struct rxrpc_call *call)
	{
	struct rxrpc_connection *conn = call->conn;

	call->peer->cong_cwnd = call->cong_cwnd;

	spin_lock_bh(&conn->params.peer->lock);
	hlist_del_init(&call->error_link);
	spin_unlock_bh(&conn->params.peer->lock);

	if (rxrpc_is_client_call(call))
	return rxrpc_disconnect_client_call(call);

	spin_lock(&conn->channel_lock);
	__rxrpc_disconnect_call(conn, call);
	spin_unlock(&conn->channel_lock);

	call->conn = NULL;
	conn->idle_timestamp = jiffies;
	rxrpc_put_connection(conn);
	}

	/*
	* Kill off a connection.
	*/
	void rxrpc_kill_connection(struct rxrpc_connection *conn)
	{
	struct rxrpc_net *rxnet = conn->params.local->rxnet;

	ASSERT(!rcu_access_pointer(conn->channels[0].call) &&
	!rcu_access_pointer(conn->channels[1].call) &&
	!rcu_access_pointer(conn->channels[2].call) &&
	!rcu_access_pointer(conn->channels[3].call));
	ASSERT(list_empty(&conn->cache_link));

	write_lock(&rxnet->conn_lock);
	list_del_init(&conn->proc_link);
	write_unlock(&rxnet->conn_lock);

	/* Drain the Rx queue. Note that even though we've unpublished, an
	* incoming packet could still be being added to our Rx queue, so we
	* will need to drain it again in the RCU cleanup handler.
	*/
	rxrpc_purge_queue(&conn->rx_queue);

	/* Leave final destruction to RCU. The connection processor work item
	* must carry a ref on the connection to prevent us getting here whilst
	* it is queued or running.
	*/
	call_rcu(&conn->rcu, rxrpc_destroy_connection);
	}

	/*
	* Queue a connection's work processor, getting a ref to pass to the work
	* queue.
	*/
	bool rxrpc_queue_conn(struct rxrpc_connection *conn)
	{
	const void *here = __builtin_return_address(0);
	int n = __atomic_add_unless(&conn->usage, 1, 0);
	if (n == 0)
	return false;
	if (rxrpc_queue_work(&conn->processor))
	trace_rxrpc_conn(conn, rxrpc_conn_queued, n + 1, here);
	else
	rxrpc_put_connection(conn);
	return true;
	}

	/*
	* Note the re-emergence of a connection.
	*/
	void rxrpc_see_connection(struct rxrpc_connection *conn)
	{
	const void *here = __builtin_return_address(0);
	if (conn) {
	int n = atomic_read(&conn->usage);

	trace_rxrpc_conn(conn, rxrpc_conn_seen, n, here);
	}
	}

	/*
	* Get a ref on a connection.
	*/
	void rxrpc_get_connection(struct rxrpc_connection *conn)
	{
	const void *here = __builtin_return_address(0);
	int n = atomic_inc_return(&conn->usage);

	trace_rxrpc_conn(conn, rxrpc_conn_got, n, here);
	}

	/*
	* Try to get a ref on a connection.
	*/
	struct rxrpc_connection *
	rxrpc_get_connection_maybe(struct rxrpc_connection *conn)
	{
	const void *here = __builtin_return_address(0);

	if (conn) {
	int n = __atomic_add_unless(&conn->usage, 1, 0);
	if (n > 0)
	trace_rxrpc_conn(conn, rxrpc_conn_got, n + 1, here);
	else
	conn = NULL;
	}
	return conn;
	}

	/*
	* Set the service connection reap timer.
	*/
	static void rxrpc_set_service_reap_timer(struct rxrpc_net *rxnet,
	unsigned long reap_at)
	{
	if (rxnet->live)
	timer_reduce(&rxnet->service_conn_reap_timer, reap_at);
	}

	/*
	* Release a service connection
	*/
	void rxrpc_put_service_conn(struct rxrpc_connection *conn)
	{
	const void *here = __builtin_return_address(0);
	int n;

	n = atomic_dec_return(&conn->usage);
	trace_rxrpc_conn(conn, rxrpc_conn_put_service, n, here);
	ASSERTCMP(n, >=, 0);
	if (n == 1)
	rxrpc_set_service_reap_timer(conn->params.local->rxnet,
	jiffies + rxrpc_connection_expiry);
	}

	/*
	* destroy a virtual connection
	*/
	static void rxrpc_destroy_connection(struct rcu_head *rcu)
	{
	struct rxrpc_connection *conn =
	container_of(rcu, struct rxrpc_connection, rcu);

	_enter("{%d,u=%d}", conn->debug_id, atomic_read(&conn->usage));

	ASSERTCMP(atomic_read(&conn->usage), ==, 0);

	_net("DESTROY CONN %d", conn->debug_id);

	del_timer_sync(&conn->timer);
	rxrpc_purge_queue(&conn->rx_queue);

	conn->security->clear(conn);
	key_put(conn->params.key);
	key_put(conn->server_key);
	rxrpc_put_peer(conn->params.peer);

	if (atomic_dec_and_test(&conn->params.local->rxnet->nr_conns))
	wake_up_var(&conn->params.local->rxnet->nr_conns);
	rxrpc_put_local(conn->params.local);

	kfree(conn);
	_leave("");
	}

	/*
	* reap dead service connections
	*/
	void rxrpc_service_connection_reaper(struct work_struct *work)
	{
	struct rxrpc_connection conn, _p;
	struct rxrpc_net *rxnet =
	container_of(work, struct rxrpc_net, service_conn_reaper);
	unsigned long expire_at, earliest, idle_timestamp, now;

	LIST_HEAD(graveyard);

	_enter("");

	now = jiffies;
	earliest = now + MAX_JIFFY_OFFSET;

	write_lock(&rxnet->conn_lock);
	list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
	ASSERTCMP(atomic_read(&conn->usage), >, 0);
	if (likely(atomic_read(&conn->usage) > 1))
	continue;
	if (conn->state == RXRPC_CONN_SERVICE_PREALLOC)
	continue;

	if (rxnet->live) {
	idle_timestamp = READ_ONCE(conn->idle_timestamp);
	expire_at = idle_timestamp + rxrpc_connection_expiry * HZ;
	if (conn->params.local->service_closed)
	expire_at = idle_timestamp + rxrpc_closed_conn_expiry * HZ;

	_debug("reap CONN %d { u=%d,t=%ld }",
	conn->debug_id, atomic_read(&conn->usage),
	(long)expire_at - (long)now);

	if (time_before(now, expire_at)) {
	if (time_before(expire_at, earliest))
	earliest = expire_at;
	continue;
	}
	}

	/* The usage count sits at 1 whilst the object is unused on the
	* list; we reduce that to 0 to make the object unavailable.
	*/
	if (atomic_cmpxchg(&conn->usage, 1, 0) != 1)
	continue;
	trace_rxrpc_conn(conn, rxrpc_conn_reap_service, 0, NULL);

	if (rxrpc_conn_is_client(conn))
	BUG();
	else
	rxrpc_unpublish_service_conn(conn);

	list_move_tail(&conn->link, &graveyard);
	}
	write_unlock(&rxnet->conn_lock);

	if (earliest != now + MAX_JIFFY_OFFSET) {
	_debug("reschedule reaper %ld", (long)earliest - (long)now);
	ASSERT(time_after(earliest, now));
	rxrpc_set_service_reap_timer(rxnet, earliest);
	}

	while (!list_empty(&graveyard)) {
	conn = list_entry(graveyard.next, struct rxrpc_connection,
	link);
	list_del_init(&conn->link);

	ASSERTCMP(atomic_read(&conn->usage), ==, 0);
	rxrpc_kill_connection(conn);
	}

	_leave("");
	}

	/*
	* preemptively destroy all the service connection records rather than
	* waiting for them to time out
	*/
	void rxrpc_destroy_all_connections(struct rxrpc_net *rxnet)
	{
	struct rxrpc_connection conn, _p;
	bool leak = false;

	_enter("");

	atomic_dec(&rxnet->nr_conns);
	rxrpc_destroy_all_client_connections(rxnet);

	del_timer_sync(&rxnet->service_conn_reap_timer);
	rxrpc_queue_work(&rxnet->service_conn_reaper);
	flush_workqueue(rxrpc_workqueue);

	write_lock(&rxnet->conn_lock);
	list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
	pr_err("AF_RXRPC: Leaked conn %p {%d}\n",
	conn, atomic_read(&conn->usage));
	leak = true;
	}
	write_unlock(&rxnet->conn_lock);
	BUG_ON(leak);

	ASSERT(list_empty(&rxnet->conn_proc_list));

	/* We need to wait for the connections to be destroyed by RCU as they
	* pin things that we still need to get rid of.
	*/
	wait_var_event(&rxnet->nr_conns, !atomic_read(&rxnet->nr_conns));
	_leave("");
	}