[PATCH net-next v9 17/23] ovpn: add support for peer floating

[Antonio Quartulli]

A peer connected via UDP may change its IP address without reconnecting
(float).

Add support for detecting and updating the new peer IP/port in case of
floating.

Signed-off-by: Antonio Quartulli <antonio@xxxxxxxxxxx>
---
 drivers/net/ovpn/bind.c |  10 ++--
 drivers/net/ovpn/io.c   |   9 ++++
 drivers/net/ovpn/peer.c | 126 ++++++++++++++++++++++++++++++++++++++++++++++--
 drivers/net/ovpn/peer.h |   2 +
 4 files changed, 136 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ovpn/bind.c b/drivers/net/ovpn/bind.c
index b4d2ccec2ceddf43bc445b489cc62a578ef0ad0a..d17d078c5730bf4336dc87f45cdba3f6b8cad770 100644
--- a/drivers/net/ovpn/bind.c
+++ b/drivers/net/ovpn/bind.c
@@ -47,12 +47,8 @@ struct ovpn_bind *ovpn_bind_from_sockaddr(const struct sockaddr_storage *ss)
  * @new: the new bind to assign
  */
 void ovpn_bind_reset(struct ovpn_peer *peer, struct ovpn_bind *new)
+	__must_hold(&peer->lock)
 {
-	struct ovpn_bind *old;
-
-	spin_lock_bh(&peer->lock);
-	old = rcu_replace_pointer(peer->bind, new, true);
-	spin_unlock_bh(&peer->lock);
-
-	kfree_rcu(old, rcu);
+	kfree_rcu(rcu_replace_pointer(peer->bind, new,
+				      lockdep_is_held(&peer->lock)), rcu);
 }
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
index 1c4cdbb16df4acc5c87707919c671f7a84bf4295..c857ac9015b75530cf3ae40f8db0d4db4c08e2fa 100644
--- a/drivers/net/ovpn/io.c
+++ b/drivers/net/ovpn/io.c
@@ -135,6 +135,15 @@ void ovpn_decrypt_post(void *data, int ret)
 	/* keep track of last received authenticated packet for keepalive */
 	peer->last_recv = ktime_get_real_seconds();
 
+	if (peer->sock->sock->sk->sk_protocol == IPPROTO_UDP) {
+		/* check if this peer changed it's IP address and update
+		 * state
+		 */
+		ovpn_peer_float(peer, skb);
+		/* update source endpoint for this peer */
+		ovpn_peer_update_local_endpoint(peer, skb);
+	}
+
 	/* point to encapsulated IP packet */
 	__skb_pull(skb, payload_offset);
 
diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c
index f3b20a561d614da98a8bee80272095b15bc6650d..0718051bb57d2e874e0a4e873ee24ab88eb3a38c 100644
--- a/drivers/net/ovpn/peer.c
+++ b/drivers/net/ovpn/peer.c
@@ -94,6 +94,128 @@ struct ovpn_peer *ovpn_peer_new(struct ovpn_struct *ovpn, u32 id)
 	return peer;
 }
 
+/**
+ * ovpn_peer_reset_sockaddr - recreate binding for peer
+ * @peer: peer to recreate the binding for
+ * @ss: sockaddr to use as remote endpoint for the binding
+ * @local_ip: local IP for the binding
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+static int ovpn_peer_reset_sockaddr(struct ovpn_peer *peer,
+				    const struct sockaddr_storage *ss,
+				    const u8 *local_ip)
+	__must_hold(&peer->lock)
+{
+	struct ovpn_bind *bind;
+	size_t ip_len;
+
+	/* create new ovpn_bind object */
+	bind = ovpn_bind_from_sockaddr(ss);
+	if (IS_ERR(bind))
+		return PTR_ERR(bind);
+
+	if (local_ip) {
+		if (ss->ss_family == AF_INET) {
+			ip_len = sizeof(struct in_addr);
+		} else if (ss->ss_family == AF_INET6) {
+			ip_len = sizeof(struct in6_addr);
+		} else {
+			netdev_dbg(peer->ovpn->dev, "%s: invalid family for remote endpoint\n",
+				   __func__);
+			kfree(bind);
+			return -EINVAL;
+		}
+
+		memcpy(&bind->local, local_ip, ip_len);
+	}
+
+	/* set binding */
+	ovpn_bind_reset(peer, bind);
+
+	return 0;
+}
+
+#define ovpn_get_hash_head(_tbl, _key, _key_len) ({		\
+	typeof(_tbl) *__tbl = &(_tbl);				\
+	(&(*__tbl)[jhash(_key, _key_len, 0) % HASH_SIZE(*__tbl)]); }) \
+
+/**
+ * ovpn_peer_float - update remote endpoint for peer
+ * @peer: peer to update the remote endpoint for
+ * @skb: incoming packet to retrieve the source address (remote) from
+ */
+void ovpn_peer_float(struct ovpn_peer *peer, struct sk_buff *skb)
+{
+	struct hlist_nulls_head *nhead;
+	struct sockaddr_storage ss;
+	const u8 *local_ip = NULL;
+	struct sockaddr_in6 *sa6;
+	struct sockaddr_in *sa;
+	struct ovpn_bind *bind;
+	sa_family_t family;
+	size_t salen;
+
+	rcu_read_lock();
+	bind = rcu_dereference(peer->bind);
+	if (unlikely(!bind)) {
+		rcu_read_unlock();
+		return;
+	}
+
+	spin_lock_bh(&peer->lock);
+	if (likely(ovpn_bind_skb_src_match(bind, skb)))
+		goto unlock;
+
+	family = skb_protocol_to_family(skb);
+
+	if (bind->remote.in4.sin_family == family)
+		local_ip = (u8 *)&bind->local;
+
+	switch (family) {
+	case AF_INET:
+		sa = (struct sockaddr_in *)&ss;
+		sa->sin_family = AF_INET;
+		sa->sin_addr.s_addr = ip_hdr(skb)->saddr;
+		sa->sin_port = udp_hdr(skb)->source;
+		salen = sizeof(*sa);
+		break;
+	case AF_INET6:
+		sa6 = (struct sockaddr_in6 *)&ss;
+		sa6->sin6_family = AF_INET6;
+		sa6->sin6_addr = ipv6_hdr(skb)->saddr;
+		sa6->sin6_port = udp_hdr(skb)->source;
+		sa6->sin6_scope_id = ipv6_iface_scope_id(&ipv6_hdr(skb)->saddr,
+							 skb->skb_iif);
+		salen = sizeof(*sa6);
+		break;
+	default:
+		goto unlock;
+	}
+
+	netdev_dbg(peer->ovpn->dev, "%s: peer %d floated to %pIScp", __func__,
+		   peer->id, &ss);
+	ovpn_peer_reset_sockaddr(peer, (struct sockaddr_storage *)&ss,
+				 local_ip);
+
+	/* rehashing is required only in MP mode as P2P has one peer
+	 * only and thus there is no hashtable
+	 */
+	if (peer->ovpn->mode == OVPN_MODE_MP) {
+		spin_lock_bh(&peer->ovpn->peers->lock);
+		/* remove old hashing */
+		hlist_nulls_del_init_rcu(&peer->hash_entry_transp_addr);
+		/* re-add with new transport address */
+		nhead = ovpn_get_hash_head(peer->ovpn->peers->by_transp_addr,
+					   &ss, salen);
+		hlist_nulls_add_head_rcu(&peer->hash_entry_transp_addr, nhead);
+		spin_unlock_bh(&peer->ovpn->peers->lock);
+	}
+unlock:
+	spin_unlock_bh(&peer->lock);
+	rcu_read_unlock();
+}
+
 static void ovpn_peer_release(struct ovpn_peer *peer)
 {
 	if (peer->sock)
@@ -186,10 +308,6 @@ static struct in6_addr ovpn_nexthop_from_skb6(struct sk_buff *skb)
 	return rt->rt6i_gateway;
 }
 
-#define ovpn_get_hash_head(_tbl, _key, _key_len) ({		\
-	typeof(_tbl) *__tbl = &(_tbl);				\
-	(&(*__tbl)[jhash(_key, _key_len, 0) % HASH_SIZE(*__tbl)]); }) \
-
 /**
  * ovpn_peer_get_by_vpn_addr4 - retrieve peer by its VPN IPv4 address
  * @ovpn: the openvpn instance to search
diff --git a/drivers/net/ovpn/peer.h b/drivers/net/ovpn/peer.h
index 1a8638d266b11a4a80ee2f088394d47a7798c3af..940cea5372ec0375cfe3e673154a1e0248978409 100644
--- a/drivers/net/ovpn/peer.h
+++ b/drivers/net/ovpn/peer.h
@@ -155,4 +155,6 @@ void ovpn_peer_keepalive_work(struct work_struct *work);
 void ovpn_peer_update_local_endpoint(struct ovpn_peer *peer,
 				     struct sk_buff *skb);
 
+void ovpn_peer_float(struct ovpn_peer *peer, struct sk_buff *skb);
+
 #endif /* _NET_OVPN_OVPNPEER_H_ */

-- 
2.45.2