Handle neighbor solicitation requests without link layer addresses.

Apparently FreeBSD likes to send out neighbor solicitation requests, even on a
tun interface where this is completely pointless. These requests do not have an
option header containing a link layer address, so the proxy-neighborsol code
was treating these requests as invalid. We now handle such requests, and send
back equally pointless replies, also without a link layer address. This seems
to satisfy FreeBSD.

diff --git a/src/route.c b/src/route.c
index c458ea4..52b538b 100644 (file)
--- a/src/route.c
+++ b/src/route.c
@@ -521,6 +521,7 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
        struct nd_opt_hdr opt;
        subnet_t *subnet;
        uint16_t checksum;
+       bool has_opt;
 
        struct {
                struct in6_addr ip6_src;        /* source address */
@@ -531,9 +532,11 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 
        cp();
 
-       if(!checklength(source, packet, ether_size + ip6_size + ns_size + opt_size + ETH_ALEN))
+       if(!checklength(source, packet, ether_size + ip6_size + ns_size))
                return;
        
+       has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
+       
        if(source != myself) {
                ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
                return;
@@ -543,7 +546,8 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 
        memcpy(&ip6, packet->data + ether_size, ip6_size);
        memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
-       memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
+       if(has_opt)
+               memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 
        /* First, snatch the source address from the neighbor solicitation packet */
 
@@ -553,7 +557,7 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
        /* Check if this is a valid neighbor solicitation request */
 
        if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
-          opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR) {
+          (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
                ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
                return;
        }
@@ -562,15 +566,20 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 
        pseudo.ip6_src = ip6.ip6_src;
        pseudo.ip6_dst = ip6.ip6_dst;
-       pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
+       if(has_opt)
+               pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
+       else
+               pseudo.length = htonl(ns_size);
        pseudo.next = htonl(IPPROTO_ICMPV6);
 
        /* Generate checksum */
 
        checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
        checksum = inet_checksum(&ns, ns_size, checksum);
-       checksum = inet_checksum(&opt, opt_size, checksum);
-       checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
+       if(has_opt) {
+               checksum = inet_checksum(&opt, opt_size, checksum);
+               checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
+       }
 
        if(checksum) {
                ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
@@ -608,7 +617,8 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
        ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
        ip6.ip6_src = ns.nd_ns_target;
 
-       memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
+       if(has_opt)
+               memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 
        ns.nd_ns_cksum = 0;
        ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
@@ -619,15 +629,20 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 
        pseudo.ip6_src = ip6.ip6_src;
        pseudo.ip6_dst = ip6.ip6_dst;
-       pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
+       if(has_opt)
+               pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
+       else
+               pseudo.length = htonl(ns_size);
        pseudo.next = htonl(IPPROTO_ICMPV6);
 
        /* Generate checksum */
 
        checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
        checksum = inet_checksum(&ns, ns_size, checksum);
-       checksum = inet_checksum(&opt, opt_size, checksum);
-       checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
+       if(has_opt) {
+               checksum = inet_checksum(&opt, opt_size, checksum);
+               checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
+       }
 
        ns.nd_ns_hdr.icmp6_cksum = checksum;
 
@@ -635,7 +650,8 @@ static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 
        memcpy(packet->data + ether_size, &ip6, ip6_size);
        memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
-       memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
+       if(has_opt)
+               memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 
        send_packet(source, packet);
 }