From: Vittorio Gambaletta (VittGam) <github@vittgam.net>
Date: Thu, 3 Sep 2015 14:02:50 +0000 (+0200)
Subject: Fix DecrementTTL option.
X-Git-Tag: release-1.0.27~35
X-Git-Url: https://tinc-vpn.org/git/browse?a=commitdiff_plain;h=a588f6febeca13edd038d78e42efb8aa9f16a444;p=tinc

Fix DecrementTTL option.

The option was not actually working, as it could be seen on traceroute or mtr.

The problem is that it was checking if the TTL was < 1 (so equal to 0) before decrementing it.

This meant that a packet with a TTL of 1 was being sent with a TTL of 0 on the VPN, instead of being discarded with the ICMP error message.

Signed-off-by: Vittorio Gambaletta <openwrt@vittgam.net>
---

diff --git a/src/route.c b/src/route.c
index c11267b1..a1254d80 100644
--- a/src/route.c
+++ b/src/route.c
@@ -891,7 +891,7 @@ static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 			if(!checklength(source, packet, ethlen + ip_size))
 				return false;
 
-			if(packet->data[ethlen + 8] < 1) {
+			if(packet->data[ethlen + 8] <= 1) {
 				if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 					route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 				return false;
@@ -914,7 +914,7 @@ static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 			if(!checklength(source, packet, ethlen + ip6_size))
 				return false;
 
-			if(packet->data[ethlen + 7] < 1) {
+			if(packet->data[ethlen + 7] <= 1) {
 				if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 					route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 				return false;