1 files changed, 230 insertions, 0 deletions
diff --git a/net/rxrpc/conn_service.c b/net/rxrpc/conn_service.c
new file mode 100644
index 000000000000..fd9027ccba8f
--- /dev/null
+++ b/net/rxrpc/conn_service.c
@@ -0,0 +1,230 @@
+/* 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);
+}