+void route_arp(vpn_packet_t *packet)
+{
+ struct ether_arp *arp;
+ subnet_t *subnet;
+ unsigned char ipbuf[4];
+ ipv4_t dest;
+cp
+ /* First, snatch the source address from the ARP packet */
+
+ memcpy(mymac.net.mac.address.x, packet->data + 6, 6);
+
+ /* This routine generates replies to ARP requests.
+ You don't need to set NOARP flag on the interface anymore (which is broken on FreeBSD).
+ Most of the code here is taken from choparp.c by Takamichi Tateoka (tree@mma.club.uec.ac.jp)
+ */
+
+ arp = (struct ether_arp *)(packet->data + 14);
+
+ /* Check if this is a valid ARP request */
+
+ if(ntohs(arp->arp_hrd) != ARPHRD_ETHER ||
+ ntohs(arp->arp_pro) != ETHERTYPE_IP ||
+ (int) (arp->arp_hln) != ETHER_ADDR_LEN ||
+ (int) (arp->arp_pln) != 4 ||
+ ntohs(arp->arp_op) != ARPOP_REQUEST )
+ {
+ if(debug_lvl > DEBUG_TRAFFIC)
+ {
+ syslog(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
+ }
+ return;
+ }
+
+ /* Check if the IP address exists on the VPN */
+
+ dest = ntohl(*((unsigned long*)(arp->arp_tpa)));
+ subnet = lookup_subnet_ipv4(&dest);
+
+ if(!subnet)
+ {
+ if(debug_lvl >= DEBUG_TRAFFIC)
+ {
+ syslog(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
+ arp->arp_tpa[0], arp->arp_tpa[1], arp->arp_tpa[2], arp->arp_tpa[3]);
+ }
+
+ return;
+ }
+
+ /* Check if it is for our own subnet */
+
+ if(subnet->owner == myself)
+ return; /* silently ignore */
+
+ memcpy(packet->data, packet->data + ETHER_ADDR_LEN, ETHER_ADDR_LEN); /* copy destination address */
+ packet->data[ETHER_ADDR_LEN*2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
+
+ memcpy(ipbuf, arp->arp_tpa, 4); /* save protocol addr */
+ memcpy(arp->arp_tpa, arp->arp_spa, 4); /* swap destination and source protocol address */
+ memcpy(arp->arp_spa, ipbuf, 4); /* ... */
+
+ memcpy(arp->arp_tha, arp->arp_sha, 10); /* set target hard/proto addr */
+ memcpy(arp->arp_sha, packet->data + ETHER_ADDR_LEN, ETHER_ADDR_LEN); /* add fake source hard addr */
+ arp->arp_op = htons(ARPOP_REPLY);
+
+ accept_packet(packet);
+cp
+}
+