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 c11267b..a1254d8 100644 (file)
--- 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(!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;
                                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(!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;
                                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;