[PATCH v21 17/24] ovpn: add support for updating local UDP endpoint

[Antonio Quartulli <antonio@openvpn.net>]

In case of UDP links, the local endpoint used to communicate with a
given peer may change without a connection restart.

Add support for learning the new address in case of change.

Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
---
 drivers/net/ovpn/peer.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/net/ovpn/peer.h |  3 +++
 2 files changed, 48 insertions(+)

diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c
index 45e87ac155b554044388490a403f64c777d283a6..1803359b833d5797728566fb976e253e2a85ea75 100644
--- a/drivers/net/ovpn/peer.c
+++ b/drivers/net/ovpn/peer.c
@@ -522,6 +522,51 @@ static void ovpn_peer_remove(struct ovpn_peer *peer,
 	llist_add(&peer->release_entry, release_list);
 }
 
+/**
+ * ovpn_peer_update_local_endpoint - update local endpoint for peer
+ * @peer: peer to update the endpoint for
+ * @skb: incoming packet to retrieve the destination address (local) from
+ */
+void ovpn_peer_update_local_endpoint(struct ovpn_peer *peer,
+				     struct sk_buff *skb)
+{
+	struct ovpn_bind *bind;
+
+	rcu_read_lock();
+	bind = rcu_dereference(peer->bind);
+	if (unlikely(!bind))
+		goto unlock;
+
+	spin_lock_bh(&peer->lock);
+	switch (skb->protocol) {
+	case htons(ETH_P_IP):
+		if (unlikely(bind->local.ipv4.s_addr != ip_hdr(skb)->daddr)) {
+			net_dbg_ratelimited("%s: learning local IPv4 for peer %d (%pI4 -> %pI4)\n",
+					    netdev_name(peer->ovpn->dev),
+					    peer->id, &bind->local.ipv4.s_addr,
+					    &ip_hdr(skb)->daddr);
+			bind->local.ipv4.s_addr = ip_hdr(skb)->daddr;
+		}
+		break;
+	case htons(ETH_P_IPV6):
+		if (unlikely(!ipv6_addr_equal(&bind->local.ipv6,
+					      &ipv6_hdr(skb)->daddr))) {
+			net_dbg_ratelimited("%s: learning local IPv6 for peer %d (%pI6c -> %pI6c\n",
+					    netdev_name(peer->ovpn->dev),
+					    peer->id, &bind->local.ipv6,
+					    &ipv6_hdr(skb)->daddr);
+			bind->local.ipv6 = ipv6_hdr(skb)->daddr;
+		}
+		break;
+	default:
+		break;
+	}
+	spin_unlock_bh(&peer->lock);
+
+unlock:
+	rcu_read_unlock();
+}
+
 /**
  * ovpn_peer_get_by_dst - Lookup peer to send skb to
  * @ovpn: the private data representing the current VPN session
diff --git a/drivers/net/ovpn/peer.h b/drivers/net/ovpn/peer.h
index e747c4b210642db990222986a80bb37c9a0413fe..d90ccc313cc3af24ffa6df8bb41bca15fbb022ad 100644
--- a/drivers/net/ovpn/peer.h
+++ b/drivers/net/ovpn/peer.h
@@ -153,4 +153,7 @@ bool ovpn_peer_check_by_src(struct ovpn_priv *ovpn, struct sk_buff *skb,
 void ovpn_peer_keepalive_set(struct ovpn_peer *peer, u32 interval, u32 timeout);
 void ovpn_peer_keepalive_work(struct work_struct *work);
 
+void ovpn_peer_update_local_endpoint(struct ovpn_peer *peer,
+				     struct sk_buff *skb);
+
 #endif /* _NET_OVPN_OVPNPEER_H_ */

-- 
2.45.3