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Fix DecrementTTL option for packets destined to the local node.
[tinc] / src / route.c
diff --git a/src/route.c b/src/route.c
index 68a6649..6415f0e 100644 (file)
--- a/src/route.c
+++ b/src/route.c
@@ -55,6 +55,8 @@ static const size_t icmp6_size = sizeof(struct icmp6_hdr);
 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
 static const size_t opt_size = sizeof(struct nd_opt_hdr);
 
+static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet);
+
 #ifndef MAX
 #define MAX(a, b) ((a) > (b) ? (a) : (b))
 #endif
@@ -250,6 +252,14 @@ static void learn_mac(mac_t *address) {
        }
 }
 
+static void broadcast_packet_helper(node_t *source, vpn_packet_t *packet) {
+       if(decrement_ttl && source != myself)
+               if(!do_decrement_ttl(source, packet))
+                       return;
+
+       broadcast_packet(source, packet);
+}
+
 /* RFC 792 */
 
 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
@@ -276,6 +286,27 @@ 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 */
+
+       if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
+               int 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)
@@ -398,7 +429,7 @@ static void route_ipv4(node_t *source, vpn_packet_t *packet) {
        }
 
        if (!subnet->owner) {
-               broadcast_packet(source, packet);
+               broadcast_packet_helper(source, packet);
                return;
        }
 
@@ -413,6 +444,10 @@ static void route_ipv4(node_t *source, vpn_packet_t *packet) {
        if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
                return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 
+       if(decrement_ttl && source != myself && subnet->owner != myself)
+               if(!do_decrement_ttl(source, packet))
+                       return;
+
        if(priorityinheritance)
                packet->priority = DATA(packet)[15];
 
@@ -448,7 +483,7 @@ 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;      
 
        struct {
                struct in6_addr ip6_src;        /* source address */
@@ -473,6 +508,27 @@ 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 */
+
+       if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
+               int 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)
@@ -558,7 +614,7 @@ static void route_ipv6(node_t *source, vpn_packet_t *packet) {
        }
 
        if (!subnet->owner) {
-               broadcast_packet(source, packet);
+               broadcast_packet_helper(source, packet);
                return;
        }
 
@@ -573,6 +629,10 @@ static void route_ipv6(node_t *source, vpn_packet_t *packet) {
        if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
                return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 
+       if(decrement_ttl && source != myself && subnet->owner != myself)
+               if(!do_decrement_ttl(source, packet))
+                       return;
+
        via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 
        if(via == source) {
@@ -689,6 +749,10 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
        if(subnet->owner == myself)
                return;                                          /* silently ignore */
 
+       if(decrement_ttl)
+               if(!do_decrement_ttl(source, packet))
+                       return;
+
        /* Create neighbor advertation reply */
 
        memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
@@ -784,6 +848,10 @@ static void route_arp(node_t *source, vpn_packet_t *packet) {
        if(subnet->owner == myself)
                return;                                          /* silently ignore */
 
+       if(decrement_ttl)
+               if(!do_decrement_ttl(source, packet))
+                       return;
+
        memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
        memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
        memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
@@ -818,7 +886,7 @@ static void route_mac(node_t *source, vpn_packet_t *packet) {
        subnet = lookup_subnet_mac(NULL, &dest);
 
        if(!subnet || !subnet->owner) {
-               broadcast_packet(source, packet);
+               broadcast_packet_helper(source, packet);
                return;
        }
 
@@ -830,6 +898,10 @@ static void route_mac(node_t *source, vpn_packet_t *packet) {
        if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
                return;
 
+       if(decrement_ttl && source != myself && subnet->owner != myself)
+               if(!do_decrement_ttl(source, packet))
+                       return;
+
        uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 
        if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
@@ -902,7 +974,7 @@ static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
                        if(!checklength(source, packet, ethlen + ip_size))
                                return false;
 
-                       if(DATA(packet)[ethlen + 8] < 1) {
+                       if(DATA(packet)[ethlen + 8] <= 1) {
                                if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED)
                                        route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
                                return false;
@@ -925,7 +997,7 @@ static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
                        if(!checklength(source, packet, ethlen + ip6_size))
                                return false;
 
-                       if(DATA(packet)[ethlen + 7] < 1) {
+                       if(DATA(packet)[ethlen + 7] <= 1) {
                                if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED)
                                        route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
                                return false;
@@ -952,10 +1024,6 @@ void route(node_t *source, vpn_packet_t *packet) {
        if(!checklength(source, packet, ether_size))
                return;
 
-       if(decrement_ttl && source != myself)
-               if(!do_decrement_ttl(source, packet))
-                       return;
-
        uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 
        switch (routing_mode) {
@@ -984,7 +1052,7 @@ void route(node_t *source, vpn_packet_t *packet) {
                        break;
 
                case RMODE_HUB:
-                       broadcast_packet(source, packet);
+                       broadcast_packet_helper(source, packet);
                        break;
        }
 }
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