From: Etienne Dechamps <etienne@edechamps.fr>
Date: Tue, 2 Jan 2018 09:55:26 +0000 (+0000)
Subject: Support MSS clamping for IP in IP (RFC 2003) packets.
X-Git-Tag: release-1.1pre16~44^2
X-Git-Url: https://tinc-vpn.org/git/browse?p=tinc;a=commitdiff_plain;h=9ca5a3c43854fba782d87be080d7a97a88ef3427

Support MSS clamping for IP in IP (RFC 2003) packets.

This change allows tinc MSS clamping to operate on TCP streams that are
inside an IP in IP tunnel.
---

diff --git a/src/route.c b/src/route.c
index a130e690..92dc1cd0 100644
--- a/src/route.c
+++ b/src/route.c
@@ -406,6 +406,15 @@ static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *pac
 		type = DATA(packet)[16] << 8 | DATA(packet)[17];
 	}
 
+	/* IP in IP (RFC 2003) packet */
+	if(type == ETH_P_IP && DATA(packet)[start + 9] == 4) {
+		start += 20;
+	}
+
+	if(packet->len <= start + 20) {
+		return;
+	}
+
 	if(type == ETH_P_IP && DATA(packet)[start + 9] == 6) {
 		start += (DATA(packet)[start] & 0xf) * 4;
 	} else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6) {