From 92203bdbcb1af4a52c7ca9d0e1a271168435c905 Mon Sep 17 00:00:00 2001 From: "Vittorio Gambaletta (VittGam)" Date: Fri, 4 Sep 2015 04:00:57 +0200 Subject: [PATCH] Fix source IP address for ICMP unreachable packets generated by tinc. Try to send ICMP unreachable replies from an address assigned to the local machine, instead of the destination address of the original packet. The address is found by looking up the route towards the sender of the packet that generated the error; in usual configurations, this is the tinc interface. This also fixes the traceroute display in mtr when using the DecrementTTL option. Signed-off-by: Vittorio Gambaletta # Conflicts: # src/route.c --- src/route.c | 42 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) diff --git a/src/route.c b/src/route.c index d7c4c87..3d7b1df 100644 --- a/src/route.c +++ b/src/route.c @@ -259,6 +259,7 @@ static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_ struct in_addr ip_src; struct in_addr ip_dst; uint32_t oldlen; + int sockfd; if(ratelimit(3)) return; @@ -276,6 +277,25 @@ static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_ ip_src = ip.ip_src; ip_dst = ip.ip_dst; + /* Try to reply with an IP address assigned to the local machine */ + + sockfd = socket(AF_INET, SOCK_DGRAM, 0); + if (sockfd != -1) { + struct sockaddr_in addr; + memset(&addr, 0, sizeof(addr)); + addr.sin_family = AF_INET; + addr.sin_addr = ip.ip_src; + if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) { + memset(&addr, 0, sizeof(addr)); + addr.sin_family = AF_INET; + socklen_t addrlen = sizeof(addr); + if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) { + ip_dst = addr.sin_addr; + } + } + close(sockfd); + } + oldlen = packet->len - ether_size; if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) @@ -448,7 +468,8 @@ static void route_ipv4(node_t *source, vpn_packet_t *packet) { static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) { struct ip6_hdr ip6; struct icmp6_hdr icmp6 = {0}; - uint16_t checksum; + uint16_t checksum; + int sockfd; struct { struct in6_addr ip6_src; /* source address */ @@ -473,6 +494,25 @@ static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_ pseudo.ip6_src = ip6.ip6_dst; pseudo.ip6_dst = ip6.ip6_src; + /* Try to reply with an IP address assigned to the local machine */ + + sockfd = socket(AF_INET6, SOCK_DGRAM, 0); + if (sockfd != -1) { + struct sockaddr_in6 addr; + memset(&addr, 0, sizeof(addr)); + addr.sin6_family = AF_INET6; + addr.sin6_addr = ip6.ip6_src; + if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) { + memset(&addr, 0, sizeof(addr)); + addr.sin6_family = AF_INET6; + socklen_t addrlen = sizeof(addr); + if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) { + pseudo.ip6_src = addr.sin6_addr; + } + } + close(sockfd); + } + pseudo.length = packet->len - ether_size; if(type == ICMP6_PACKET_TOO_BIG) -- 2.25.1