On 25.09.2018 16:56, Jason A. Donenfeld wrote:

Extensive documentation and description of the protocol and
considerations, along with formal proofs of the cryptography, are> available at:

  * https://www.wireguard.com/
  * https://www.wireguard.com/papers/wireguard.pdf

[]

+enum { HANDSHAKE_DSCP = 0x88 /* AF41, plus 00 ECN */ };

[]

+	if (skb->protocol == htons(ETH_P_IP)) {
+		len = ntohs(ip_hdr(skb)->tot_len);
+		if (unlikely(len < sizeof(struct iphdr)))
+			goto dishonest_packet_size;
+		if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
+			IP_ECN_set_ce(ip_hdr(skb));
+	} else if (skb->protocol == htons(ETH_P_IPV6)) {
+		len = ntohs(ipv6_hdr(skb)->payload_len) +
+		      sizeof(struct ipv6hdr);
+		if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
+			IP6_ECN_set_ce(skb, ipv6_hdr(skb));
+	} else

[]

+	skb_queue_walk (&packets, skb) {
+		/* 0 for no outer TOS: no leak. TODO: should we use flowi->tos
+		 * as outer? */
+		PACKET_CB(skb)->ds = ip_tunnel_ecn_encap(0, ip_hdr(skb), skb);
+		PACKET_CB(skb)->nonce =
+				atomic64_inc_return(&key->counter.counter) - 1;
+		if (unlikely(PACKET_CB(skb)->nonce >= REJECT_AFTER_MESSAGES))
+			goto out_invalid;
+	}

Hi,

is there documentation and/or rationale for ecn handling?
Quick search for ecn and dscp didn't reveal any.

Regards,
Ivan