+ if (dev->seq >= 0 && dev->seq < ARRAY_SIZE(disabled) &&
+ disabled[dev->seq])
+ return 0;
+
+ if (ntohs(eth->et_protlen) == PROT_ARP) {
+ struct arp_hdr *arp = packet + ETHER_HDR_SIZE;
+
+ if (ntohs(arp->ar_op) == ARPOP_REQUEST) {
+ struct ethernet_hdr *eth_recv;
+ struct arp_hdr *arp_recv;
+
+ /* store this as the assumed IP of the fake host */
+ priv->fake_host_ipaddr = net_read_ip(&arp->ar_tpa);
+ /* Formulate a fake response */
+ eth_recv = (void *)priv->recv_packet_buffer;
+ memcpy(eth_recv->et_dest, eth->et_src, ARP_HLEN);
+ memcpy(eth_recv->et_src, priv->fake_host_hwaddr,
+ ARP_HLEN);
+ eth_recv->et_protlen = htons(PROT_ARP);
+
+ arp_recv = (void *)priv->recv_packet_buffer +
+ ETHER_HDR_SIZE;
+ arp_recv->ar_hrd = htons(ARP_ETHER);
+ arp_recv->ar_pro = htons(PROT_IP);
+ arp_recv->ar_hln = ARP_HLEN;
+ arp_recv->ar_pln = ARP_PLEN;
+ arp_recv->ar_op = htons(ARPOP_REPLY);
+ memcpy(&arp_recv->ar_sha, priv->fake_host_hwaddr,
+ ARP_HLEN);
+ net_write_ip(&arp_recv->ar_spa, priv->fake_host_ipaddr);
+ memcpy(&arp_recv->ar_tha, &arp->ar_sha, ARP_HLEN);
+ net_copy_ip(&arp_recv->ar_tpa, &arp->ar_spa);
+
+ priv->recv_packet_length = ETHER_HDR_SIZE +
+ ARP_HDR_SIZE;
+ }
+ } else if (ntohs(eth->et_protlen) == PROT_IP) {
+ struct ip_udp_hdr *ip = packet + ETHER_HDR_SIZE;
+
+ if (ip->ip_p == IPPROTO_ICMP) {
+ struct icmp_hdr *icmp = (struct icmp_hdr *)&ip->udp_src;
+
+ if (icmp->type == ICMP_ECHO_REQUEST) {
+ struct ethernet_hdr *eth_recv;
+ struct ip_udp_hdr *ipr;
+ struct icmp_hdr *icmpr;
+
+ /* reply to the ping */
+ memcpy(priv->recv_packet_buffer, packet,
+ length);
+ eth_recv = (void *)priv->recv_packet_buffer;
+ ipr = (void *)priv->recv_packet_buffer +
+ ETHER_HDR_SIZE;
+ icmpr = (struct icmp_hdr *)&ipr->udp_src;
+ memcpy(eth_recv->et_dest, eth->et_src,
+ ARP_HLEN);
+ memcpy(eth_recv->et_src, priv->fake_host_hwaddr,
+ ARP_HLEN);
+ ipr->ip_sum = 0;
+ ipr->ip_off = 0;
+ net_copy_ip((void *)&ipr->ip_dst, &ip->ip_src);
+ net_write_ip((void *)&ipr->ip_src,
+ priv->fake_host_ipaddr);
+ ipr->ip_sum = compute_ip_checksum(ipr,
+ IP_HDR_SIZE);
+
+ icmpr->type = ICMP_ECHO_REPLY;
+ icmpr->checksum = 0;
+ icmpr->checksum = compute_ip_checksum(icmpr,
+ ICMP_HDR_SIZE);
+
+ priv->recv_packet_length = length;
+ }
+ }
+ }
+