xref: /openbmc/linux/net/rxrpc/conn_service.c (revision 8ee90c5c)
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 
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 				break;
54 			conn = NULL;
55 		}
56 	} while (need_seqretry(&peer->service_conn_lock, seq));
57 
58 	done_seqretry(&peer->service_conn_lock, seq);
59 	_leave(" = %d", conn ? conn->debug_id : -1);
60 	return conn;
61 }
62 
63 /*
64  * Insert a service connection into a peer's tree, thereby making it a target
65  * for incoming packets.
66  */
67 static void rxrpc_publish_service_conn(struct rxrpc_peer *peer,
68 				       struct rxrpc_connection *conn)
69 {
70 	struct rxrpc_connection *cursor = NULL;
71 	struct rxrpc_conn_proto k = conn->proto;
72 	struct rb_node **pp, *parent;
73 
74 	write_seqlock_bh(&peer->service_conn_lock);
75 
76 	pp = &peer->service_conns.rb_node;
77 	parent = NULL;
78 	while (*pp) {
79 		parent = *pp;
80 		cursor = rb_entry(parent,
81 				  struct rxrpc_connection, service_node);
82 
83 		if (cursor->proto.index_key < k.index_key)
84 			pp = &(*pp)->rb_left;
85 		else if (cursor->proto.index_key > k.index_key)
86 			pp = &(*pp)->rb_right;
87 		else
88 			goto found_extant_conn;
89 	}
90 
91 	rb_link_node_rcu(&conn->service_node, parent, pp);
92 	rb_insert_color(&conn->service_node, &peer->service_conns);
93 conn_published:
94 	set_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags);
95 	write_sequnlock_bh(&peer->service_conn_lock);
96 	_leave(" = %d [new]", conn->debug_id);
97 	return;
98 
99 found_extant_conn:
100 	if (atomic_read(&cursor->usage) == 0)
101 		goto replace_old_connection;
102 	write_sequnlock_bh(&peer->service_conn_lock);
103 	/* We should not be able to get here.  rxrpc_incoming_connection() is
104 	 * called in a non-reentrant context, so there can't be a race to
105 	 * insert a new connection.
106 	 */
107 	BUG();
108 
109 replace_old_connection:
110 	/* The old connection is from an outdated epoch. */
111 	_debug("replace conn");
112 	rb_replace_node_rcu(&cursor->service_node,
113 			    &conn->service_node,
114 			    &peer->service_conns);
115 	clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &cursor->flags);
116 	goto conn_published;
117 }
118 
119 /*
120  * Preallocate a service connection.  The connection is placed on the proc and
121  * reap lists so that we don't have to get the lock from BH context.
122  */
123 struct rxrpc_connection *rxrpc_prealloc_service_connection(struct rxrpc_net *rxnet,
124 							   gfp_t gfp)
125 {
126 	struct rxrpc_connection *conn = rxrpc_alloc_connection(gfp);
127 
128 	if (conn) {
129 		/* We maintain an extra ref on the connection whilst it is on
130 		 * the rxrpc_connections list.
131 		 */
132 		conn->state = RXRPC_CONN_SERVICE_PREALLOC;
133 		atomic_set(&conn->usage, 2);
134 
135 		write_lock(&rxnet->conn_lock);
136 		list_add_tail(&conn->link, &rxnet->service_conns);
137 		list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
138 		write_unlock(&rxnet->conn_lock);
139 
140 		trace_rxrpc_conn(conn, rxrpc_conn_new_service,
141 				 atomic_read(&conn->usage),
142 				 __builtin_return_address(0));
143 	}
144 
145 	return conn;
146 }
147 
148 /*
149  * Set up an incoming connection.  This is called in BH context with the RCU
150  * read lock held.
151  */
152 void rxrpc_new_incoming_connection(struct rxrpc_sock *rx,
153 				   struct rxrpc_connection *conn,
154 				   struct sk_buff *skb)
155 {
156 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
157 
158 	_enter("");
159 
160 	conn->proto.epoch	= sp->hdr.epoch;
161 	conn->proto.cid		= sp->hdr.cid & RXRPC_CIDMASK;
162 	conn->params.service_id	= sp->hdr.serviceId;
163 	conn->service_id	= sp->hdr.serviceId;
164 	conn->security_ix	= sp->hdr.securityIndex;
165 	conn->out_clientflag	= 0;
166 	if (conn->security_ix)
167 		conn->state	= RXRPC_CONN_SERVICE_UNSECURED;
168 	else
169 		conn->state	= RXRPC_CONN_SERVICE;
170 
171 	/* See if we should upgrade the service.  This can only happen on the
172 	 * first packet on a new connection.  Once done, it applies to all
173 	 * subsequent calls on that connection.
174 	 */
175 	if (sp->hdr.userStatus == RXRPC_USERSTATUS_SERVICE_UPGRADE &&
176 	    conn->service_id == rx->service_upgrade.from)
177 		conn->service_id = rx->service_upgrade.to;
178 
179 	/* Make the connection a target for incoming packets. */
180 	rxrpc_publish_service_conn(conn->params.peer, conn);
181 
182 	_net("CONNECTION new %d {%x}", conn->debug_id, conn->proto.cid);
183 }
184 
185 /*
186  * Remove the service connection from the peer's tree, thereby removing it as a
187  * target for incoming packets.
188  */
189 void rxrpc_unpublish_service_conn(struct rxrpc_connection *conn)
190 {
191 	struct rxrpc_peer *peer = conn->params.peer;
192 
193 	write_seqlock_bh(&peer->service_conn_lock);
194 	if (test_and_clear_bit(RXRPC_CONN_IN_SERVICE_CONNS, &conn->flags))
195 		rb_erase(&conn->service_node, &peer->service_conns);
196 	write_sequnlock_bh(&peer->service_conn_lock);
197 }
198