2024-10-29, 11:47:22 +0100, Antonio Quartulli wrote:

+static int ovpn_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
+{

[...]

+	opcode = ovpn_opcode_from_skb(skb, sizeof(struct udphdr));
+	if (unlikely(opcode != OVPN_DATA_V2)) {
+		/* DATA_V1 is not supported */
+		if (opcode == OVPN_DATA_V1)

The TCP encap code passes everything that's not V2 to userspace. Why
not do that with UDP as well?

+			goto drop;
+
+		/* unknown or control packet: let it bubble up to userspace */
+		return 1;
+	}
+
+	peer_id = ovpn_peer_id_from_skb(skb, sizeof(struct udphdr));
+	/* some OpenVPN server implementations send data packets with the
+	 * peer-id set to undef. In this case we skip the peer lookup by peer-id
+	 * and we try with the transport address
+	 */
+	if (peer_id != OVPN_PEER_ID_UNDEF) {
+		peer = ovpn_peer_get_by_id(ovpn, peer_id);
+		if (!peer) {
+			net_err_ratelimited("%s: received data from unknown peer (id: %d)\n",
+					    __func__, peer_id);
+			goto drop;
+		}
+	}
+
+	if (!peer) {

nit: that could be an "else" combined with the previous case?

+		/* data packet with undef peer-id */
+		peer = ovpn_peer_get_by_transp_addr(ovpn, skb);
+		if (unlikely(!peer)) {
+			net_dbg_ratelimited("%s: received data with undef peer-id from unknown source\n",
+					    __func__);
+			goto drop;
+		}
+	}

-- 
Sabrina