[linux-2.6-block.git] / net / rxrpc / conn_service.c

/* Service connection management
 *
 * Copyright (C) 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 Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

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

/*
 * Find a service connection under RCU conditions.
 *
 * We could use a hash table, but that is subject to bucket stuffing by an
 * attacker as the client gets to pick the epoch and cid values and would know
 * the hash function.  So, instead, we use a hash table for the peer and from
 * that an rbtree to find the service connection.  Under ordinary circumstances
 * it might be slower than a large hash table, but it is at least limited in
 * depth.
 */
struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer,
						     struct sk_buff *skb)
{
	struct rxrpc_connection *conn = NULL;
	struct rxrpc_conn_proto k;
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	struct rb_node *p;
	unsigned int seq = 0;

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

	do {
		/* Unfortunately, rbtree walking doesn't give reliable results
		 * under just the RCU read lock, so we have to check for
		 * changes.
		 */
		read_seqbegin_or_lock(&peer->service_conn_lock, &seq);

		p = rcu_dereference_raw(peer->service_conns.rb_node);
		while (p) {
			conn = rb_entry(p, struct rxrpc_connection, service_node);

			if (conn->proto.index_key < k.index_key)
				p = rcu_dereference_raw(p->rb_left);
			else if (conn->proto.index_key > k.index_key)
				p = rcu_dereference_raw(p->rb_right);
			else
				goto done;
			conn = NULL;
		}
	} while (need_seqretry(&peer->service_conn_lock, seq));

done:
	done_seqretry(&peer->service_conn_lock, seq);
	_leave(" = %d", conn ? conn->debug_id : -1);
	return conn;
}

/*
 * Insert a service connection into a peer's tree, thereby making it a target
 * for incoming packets.
 */
static struct rxrpc_connection *
rxrpc_publish_service_conn(struct rxrpc_peer *peer,
			   struct rxrpc_connection *conn)
{
	struct rxrpc_connection *cursor = NULL;
	struct rxrpc_conn_proto k = conn->proto;
	struct rb_node **pp, *parent;

	write_seqlock_bh(&peer->service_conn_lock);

	pp = &peer->service_conns.rb_node;
	parent = NULL;
	while (*pp) {
		parent = *pp;
		cursor = rb_entry(parent,
				  struct rxrpc_connection, service_node);

		if (cursor->proto.index_key < k.index_key)
			pp = &(*pp)->rb_left;
		else if (cursor->proto.index_key > k.index_key)
			pp = &(*pp)->rb_right;
		else
			goto found_extant_conn;
	}

	rb_link_node_rcu(&conn->service_node, parent, pp);
	rb_insert_color(&conn->service_node, &peer->service_conns);
conn_published:
	set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
	write_sequnlock_bh(&peer->service_conn_lock);
	_leave(" = %d [new]", conn->debug_id);
	return conn;

found_extant_conn:
	if (atomic_read(&cursor->usage) == 0)
		goto replace_old_connection;
	write_sequnlock_bh(&peer->service_conn_lock);
	/* We should not be able to get here.  rxrpc_incoming_connection() is
	 * called in a non-reentrant context, so there can't be a race to
	 * insert a new connection.
	 */
	BUG();

replace_old_connection:
	/* The old connection is from an outdated epoch. */
	_debug("replace conn");
	rb_replace_node_rcu(&cursor->service_node,
			    &conn->service_node,
			    &peer->service_conns);
	clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
	goto conn_published;
}

/*
 * get a record of an incoming connection
 */
struct rxrpc_connection *rxrpc_incoming_connection(struct rxrpc_local *local,
						   struct sockaddr_rxrpc *srx,
						   struct sk_buff *skb)
{
	struct rxrpc_connection *conn;
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	struct rxrpc_peer *peer;
	const char *new = "old";

	_enter("");

	peer = rxrpc_lookup_peer(local, srx, GFP_NOIO);
	if (!peer) {
		_debug("no peer");
		return ERR_PTR(-EBUSY);
	}

	ASSERT(sp->hdr.flags & RXRPC_CLIENT_INITIATED);

	rcu_read_lock();
	peer = rxrpc_lookup_peer_rcu(local, srx);
	if (peer) {
		conn = rxrpc_find_service_conn_rcu(peer, skb);
		if (conn) {
			if (sp->hdr.securityIndex != conn->security_ix)
				goto security_mismatch_rcu;
			if (rxrpc_get_connection_maybe(conn))
				goto found_extant_connection_rcu;

			/* The conn has expired but we can't remove it without
			 * the appropriate lock, so we attempt to replace it
			 * when we have a new candidate.
			 */
		}

		if (!rxrpc_get_peer_maybe(peer))
			peer = NULL;
	}
	rcu_read_unlock();

	if (!peer) {
		peer = rxrpc_lookup_peer(local, srx, GFP_NOIO);
		if (!peer)
			goto enomem;
	}

	/* We don't have a matching record yet. */
	conn = rxrpc_alloc_connection(GFP_NOIO);
	if (!conn)
		goto enomem_peer;

	conn->proto.epoch	= sp->hdr.epoch;
	conn->proto.cid		= sp->hdr.cid & RXRPC_CIDMASK;
	conn->params.local	= local;
	conn->params.peer	= peer;
	conn->params.service_id	= sp->hdr.serviceId;
	conn->security_ix	= sp->hdr.securityIndex;
	conn->out_clientflag	= 0;
	conn->state		= RXRPC_CONN_SERVICE;
	if (conn->params.service_id)
		conn->state	= RXRPC_CONN_SERVICE_UNSECURED;

	rxrpc_get_local(local);

	write_lock(&rxrpc_connection_lock);
	list_add_tail(&conn->link, &rxrpc_connections);
	write_unlock(&rxrpc_connection_lock);

	/* Make the connection a target for incoming packets. */
	rxrpc_publish_service_conn(peer, conn);

	new = "new";

success:
	_net("CONNECTION %s %d {%x}", new, conn->debug_id, conn->proto.cid);
	_leave(" = %p {u=%d}", conn, atomic_read(&conn->usage));
	return conn;

found_extant_connection_rcu:
	rcu_read_unlock();
	goto success;

security_mismatch_rcu:
	rcu_read_unlock();
	_leave(" = -EKEYREJECTED");
	return ERR_PTR(-EKEYREJECTED);

enomem_peer:
	rxrpc_put_peer(peer);
enomem:
	_leave(" = -ENOMEM");
	return ERR_PTR(-ENOMEM);
}

/*
 * Remove the service connection from the peer's tree, thereby removing it as a
 * target for incoming packets.
 */
void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
{
	struct rxrpc_peer *peer = conn->params.peer;

	write_seqlock_bh(&peer->service_conn_lock);
	if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
		rb_erase(&conn->service_node, &peer->service_conns);
	write_sequnlock_bh(&peer->service_conn_lock);
}
Commit	Line	Data
7877a4a4 DH	1	/* Service connection management
	2	*
	3	* Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public Licence
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the Licence, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/slab.h>
	13	#include "ar-internal.h"
	14
8496af50 DH	15	/*
	16	* Find a service connection under RCU conditions.
	17	*
	18	* We could use a hash table, but that is subject to bucket stuffing by an
	19	* attacker as the client gets to pick the epoch and cid values and would know
	20	* the hash function. So, instead, we use a hash table for the peer and from
	21	* that an rbtree to find the service connection. Under ordinary circumstances
	22	* it might be slower than a large hash table, but it is at least limited in
	23	* depth.
	24	*/
	25	struct rxrpc_connection rxrpc_find_service_conn_rcu(struct rxrpc_peer peer,
	26	struct sk_buff *skb)
	27	{
	28	struct rxrpc_connection *conn = NULL;
	29	struct rxrpc_conn_proto k;
	30	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	31	struct rb_node *p;
	32	unsigned int seq = 0;
	33
	34	k.epoch = sp->hdr.epoch;
	35	k.cid = sp->hdr.cid & RXRPC_CIDMASK;
	36
	37	do {
	38	/* Unfortunately, rbtree walking doesn't give reliable results
	39	* under just the RCU read lock, so we have to check for
	40	* changes.
	41	*/
	42	read_seqbegin_or_lock(&peer->service_conn_lock, &seq);
	43
	44	p = rcu_dereference_raw(peer->service_conns.rb_node);
	45	while (p) {
	46	conn = rb_entry(p, struct rxrpc_connection, service_node);
	47
	48	if (conn->proto.index_key < k.index_key)
	49	p = rcu_dereference_raw(p->rb_left);
	50	else if (conn->proto.index_key > k.index_key)
	51	p = rcu_dereference_raw(p->rb_right);
	52	else
	53	goto done;
	54	conn = NULL;
	55	}
	56	} while (need_seqretry(&peer->service_conn_lock, seq));
	57
	58	done:
	59	done_seqretry(&peer->service_conn_lock, seq);
	60	_leave(" = %d", conn ? conn->debug_id : -1);
	61	return conn;
	62	}
	63
	64	/*
	65	* Insert a service connection into a peer's tree, thereby making it a target
	66	* for incoming packets.
	67	*/
	68	static struct rxrpc_connection *
	69	rxrpc_publish_service_conn(struct rxrpc_peer *peer,
	70	struct rxrpc_connection *conn)
	71	{
	72	struct rxrpc_connection *cursor = NULL;
	73	struct rxrpc_conn_proto k = conn->proto;
	74	struct rb_node *pp, parent;
	75
	76	write_seqlock_bh(&peer->service_conn_lock);
	77
	78	pp = &peer->service_conns.rb_node;
79	parent = NULL;
80	while (*pp) {
81	parent = *pp;
82	cursor = rb_entry(parent,
83	struct rxrpc_connection, service_node);
84
85	if (cursor->proto.index_key < k.index_key)
86	pp = &(*pp)->rb_left;
87	else if (cursor->proto.index_key > k.index_key)
88	pp = &(*pp)->rb_right;
89	else
90	goto found_extant_conn;
91	}
92
93	rb_link_node_rcu(&conn->service_node, parent, pp);
94	rb_insert_color(&conn->service_node, &peer->service_conns);
95	conn_published:
96	set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
97	write_sequnlock_bh(&peer->service_conn_lock);
98	_leave(" = %d [new]", conn->debug_id);
99	return conn;
100
101	found_extant_conn:
102	if (atomic_read(&cursor->usage) == 0)
103	goto replace_old_connection;
104	write_sequnlock_bh(&peer->service_conn_lock);
105	/* We should not be able to get here. rxrpc_incoming_connection() is
106	* called in a non-reentrant context, so there can't be a race to
107	* insert a new connection.
108	*/
109	BUG();
110
111	replace_old_connection:
112	/* The old connection is from an outdated epoch. */
113	_debug("replace conn");
114	rb_replace_node_rcu(&cursor->service_node,
115	&conn->service_node,
116	&peer->service_conns);
117	clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
118	goto conn_published;
119	}
120
7877a4a4 DH	121	/*
	122	* get a record of an incoming connection
	123	*/
	124	struct rxrpc_connection rxrpc_incoming_connection(struct rxrpc_local local,
d991b4a3	125	struct sockaddr_rxrpc *srx,
7877a4a4 DH	126	struct sk_buff *skb)
7877a4a4 DH	127	{
8496af50	128	struct rxrpc_connection *conn;
7877a4a4	129	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
d991b4a3	130	struct rxrpc_peer *peer;
7877a4a4	131	const char *new = "old";
7877a4a4 DH	132
	133	_enter("");
	134
d991b4a3 DH	135	peer = rxrpc_lookup_peer(local, srx, GFP_NOIO);
	136	if (!peer) {
	137	_debug("no peer");
	138	return ERR_PTR(-EBUSY);
	139	}
	140
7877a4a4 DH	141	ASSERT(sp->hdr.flags & RXRPC_CLIENT_INITIATED);
7877a4a4 DH	142
8496af50 DH	143	rcu_read_lock();
	144	peer = rxrpc_lookup_peer_rcu(local, srx);
	145	if (peer) {
	146	conn = rxrpc_find_service_conn_rcu(peer, skb);
	147	if (conn) {
	148	if (sp->hdr.securityIndex != conn->security_ix)
	149	goto security_mismatch_rcu;
	150	if (rxrpc_get_connection_maybe(conn))
	151	goto found_extant_connection_rcu;
	152
	153	/* The conn has expired but we can't remove it without
	154	* the appropriate lock, so we attempt to replace it
	155	* when we have a new candidate.
	156	*/
	157	}
	158
	159	if (!rxrpc_get_peer_maybe(peer))
	160	peer = NULL;
7877a4a4	161	}
8496af50	162	rcu_read_unlock();
7877a4a4	163
8496af50 DH	164	if (!peer) {
8496af50 DH	165	peer = rxrpc_lookup_peer(local, srx, GFP_NOIO);
7acef604	166	if (!peer)
8496af50	167	goto enomem;
7877a4a4 DH	168	}
7877a4a4 DH	169
8496af50 DH	170	/* We don't have a matching record yet. */
	171	conn = rxrpc_alloc_connection(GFP_NOIO);
	172	if (!conn)
	173	goto enomem_peer;
	174
	175	conn->proto.epoch = sp->hdr.epoch;
	176	conn->proto.cid = sp->hdr.cid & RXRPC_CIDMASK;
	177	conn->params.local = local;
	178	conn->params.peer = peer;
	179	conn->params.service_id = sp->hdr.serviceId;
	180	conn->security_ix = sp->hdr.securityIndex;
	181	conn->out_clientflag = 0;
	182	conn->state = RXRPC_CONN_SERVICE;
	183	if (conn->params.service_id)
	184	conn->state = RXRPC_CONN_SERVICE_UNSECURED;
7877a4a4	185
8496af50	186	rxrpc_get_local(local);
7877a4a4 DH	187
	188	write_lock(&rxrpc_connection_lock);
	189	list_add_tail(&conn->link, &rxrpc_connections);
	190	write_unlock(&rxrpc_connection_lock);
	191
8496af50 DH	192	/* Make the connection a target for incoming packets. */
	193	rxrpc_publish_service_conn(peer, conn);
	194
7877a4a4 DH	195	new = "new";
	196
	197	success:
	198	_net("CONNECTION %s %d {%x}", new, conn->debug_id, conn->proto.cid);
7877a4a4 DH	199	_leave(" = %p {u=%d}", conn, atomic_read(&conn->usage));
	200	return conn;
	201
8496af50 DH	202	found_extant_connection_rcu:
8496af50 DH	203	rcu_read_unlock();
7877a4a4 DH	204	goto success;
7877a4a4 DH	205
8496af50 DH	206	security_mismatch_rcu:
8496af50 DH	207	rcu_read_unlock();
7877a4a4 DH	208	_leave(" = -EKEYREJECTED");
7877a4a4 DH	209	return ERR_PTR(-EKEYREJECTED);
8496af50 DH	210
	211	enomem_peer:
	212	rxrpc_put_peer(peer);
	213	enomem:
	214	_leave(" = -ENOMEM");
	215	return ERR_PTR(-ENOMEM);
7877a4a4	216	}
001c1122 DH	217
	218	/*
	219	* Remove the service connection from the peer's tree, thereby removing it as a
	220	* target for incoming packets.
	221	*/
	222	void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
	223	{
	224	struct rxrpc_peer *peer = conn->params.peer;
	225
8496af50	226	write_seqlock_bh(&peer->service_conn_lock);
001c1122 DH	227	if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
001c1122 DH	228	rb_erase(&conn->service_node, &peer->service_conns);
8496af50	229	write_sequnlock_bh(&peer->service_conn_lock);
001c1122	230	}