+ struct ip6_hdr ip6;
+ struct nd_neighbor_solicit ns;
+ struct nd_opt_hdr opt;
+ subnet_t *subnet;
+ uint16_t checksum;
+ bool has_opt;
+
+ struct {
+ struct in6_addr ip6_src; /* source address */
+ struct in6_addr ip6_dst; /* destination address */
+ uint32_t length;
+ uint32_t next;
+ } pseudo;
+
+ cp();
+
+ 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;
+ }
+
+ /* Copy headers from packet to structs on the stack */
+
+ memcpy(&ip6, packet->data + ether_size, ip6_size);
+ memcpy(&ns, packet->data + ether_size + ip6_size, ns_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 */
+
+ if(overwrite_mac)
+ memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
+
+ /* Check if this is a valid neighbor solicitation request */
+
+ if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
+ (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;
+ }
+
+ /* Create pseudo header */
+
+ pseudo.ip6_src = ip6.ip6_src;
+ pseudo.ip6_dst = ip6.ip6_dst;
+ 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);
+ 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"));
+ return;
+ }
+
+ /* Check if the IPv6 address exists on the VPN */
+
+ subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
+
+ if(!subnet) {
+ ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
+ ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
+
+ return;
+ }
+
+ /* Check if it is for our own subnet */
+
+ if(subnet->owner == myself)
+ return; /* silently ignore */
+
+ /* Create neighbor advertation reply */
+
+ memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */
+ packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
+
+ ip6.ip6_dst = ip6.ip6_src; /* swap destination and source protocoll address */
+ ip6.ip6_src = ns.nd_ns_target;
+
+ 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;
+ ns.nd_ns_reserved = htonl(0x40000000UL); /* Set solicited flag */
+ opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
+
+ /* Create pseudo header */
+
+ pseudo.ip6_src = ip6.ip6_src;
+ pseudo.ip6_dst = ip6.ip6_dst;
+ 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);
+ 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;
+
+ /* Copy structs on stack back to packet */
+
+ memcpy(packet->data + ether_size, &ip6, ip6_size);
+ memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
+ if(has_opt)
+ memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
+
+ send_packet(source, packet);