netdev - [PATCH net-next v3 17/24] ovpn: add support for updating local UDP endpoint

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Message-ID: <20240506011637.27272-18-antonio@openvpn.net>
Date: Mon,  6 May 2024 03:16:30 +0200
From: Antonio Quartulli <antonio@...nvpn.net>
To: netdev@...r.kernel.org
Cc: Jakub Kicinski <kuba@...nel.org>,
	Sergey Ryazanov <ryazanov.s.a@...il.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Andrew Lunn <andrew@...n.ch>,
	Esben Haabendal <esben@...nix.com>,
	Antonio Quartulli <antonio@...nvpn.net>
Subject: [PATCH net-next v3 17/24] ovpn: add support for updating local UDP endpoint

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@...nvpn.net>
---
 drivers/net/ovpn/io.c   |  4 ++++
 drivers/net/ovpn/peer.c | 37 +++++++++++++++++++++++++++++++++++++
 drivers/net/ovpn/peer.h |  7 +++++++
 3 files changed, 48 insertions(+)

diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
index 2469e30970b7..19ebc0fbe2be 100644
--- a/drivers/net/ovpn/io.c
+++ b/drivers/net/ovpn/io.c
@@ -218,6 +218,10 @@ static int ovpn_decrypt_one(struct ovpn_peer *peer, struct sk_buff *skb)
 	/* note event of authenticated packet received for keepalive */
 	ovpn_peer_keepalive_recv_reset(peer);
 
+	/* update source endpoint for this peer */
+	if (peer->sock->sock->sk->sk_protocol == IPPROTO_UDP)
+		ovpn_peer_update_local_endpoint(peer, skb);
+
 	/* increment RX stats */
 	ovpn_peer_stats_increment_rx(&peer->vpn_stats, skb->len);
 
diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c
index 79a6d6fb1be1..e88c2483450d 100644
--- a/drivers/net/ovpn/peer.c
+++ b/drivers/net/ovpn/peer.c
@@ -518,6 +518,43 @@ struct ovpn_peer *ovpn_peer_get_by_id(struct ovpn_struct *ovpn, u32 peer_id)
 	return peer;
 }
 
+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;
+
+	switch (skb_protocol_to_family(skb)) {
+	case AF_INET:
+		if (unlikely(bind->local.ipv4.s_addr != ip_hdr(skb)->daddr)) {
+			netdev_dbg(peer->ovpn->dev,
+				   "%s: learning local IPv4 for peer %d (%pI4 -> %pI4)\n",
+				   __func__, peer->id, &bind->local.ipv4.s_addr,
+				   &ip_hdr(skb)->daddr);
+			bind->local.ipv4.s_addr = ip_hdr(skb)->daddr;
+		}
+		break;
+	case AF_INET6:
+		if (unlikely(memcmp(&bind->local.ipv6, &ipv6_hdr(skb)->daddr,
+				    sizeof(bind->local.ipv6)))) {
+			netdev_dbg(peer->ovpn->dev,
+				   "%s: learning local IPv6 for peer %d (%pI6c -> %pI6c\n",
+				   __func__, peer->id, &bind->local.ipv6,
+				   &ipv6_hdr(skb)->daddr);
+			bind->local.ipv6 = ipv6_hdr(skb)->daddr;
+		}
+		break;
+	default:
+		break;
+	}
+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 d5b63c07408e..df2b1c93dead 100644
--- a/drivers/net/ovpn/peer.h
+++ b/drivers/net/ovpn/peer.h
@@ -273,4 +273,11 @@ static inline void ovpn_peer_keepalive_xmit_reset(struct ovpn_peer *peer)
  */
 void ovpn_peer_keepalive_set(struct ovpn_peer *peer, u32 interval, u32 timeout);
 
+/**
+ * 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);
 #endif /* _NET_OVPN_OVPNPEER_H_ */
-- 
2.43.2