void ip_handle_incoming_packet(struct sr_packet * packet)
{
struct ip * ip_hdr = IP_HDR(packet);
if(ip_hdr->ip_sum != checksum_ipheader(ip_hdr))
{
printf("\nchecksums differ %x, %x\n", ip_hdr->ip_sum, checksum_ipheader(ip_hdr));
}
else if(ip_hdr->ip_v != 4)
{
printf("\nip version is %d; only accepting 4\n",ip_hdr->ip_v);
}
else
{
if(dhcp_packet(packet))
{
dhcp_handle_incoming(packet);
}
/* if packet is not for one of our interfaces then forward */
else if(!interface_list_ip_exists(ROUTER(packet->sr)->iflist, ip_hdr->ip_dst.s_addr) &&
ntohl(ip_hdr->ip_dst.s_addr) != OSPF_AllSPFRouters)
{
if(ip_hdr->ip_ttl <= 1)
{
icmp_send_time_exceeded(packet);
}
else
{
if(ip_hdr->ip_p == IP_P_TCP || ip_hdr->ip_p == IP_P_UDP)
{
tcp_handle_incoming_not_for_us(packet);
}
else
{
ip_forward(packet);
}
}
}
else
{
switch(ip_hdr->ip_p)
{
case IP_P_ICMP:
icmp_handle_incoming_packet(packet);
break;
case IP_P_TCP: case IP_P_UDP:
tcp_handle_incoming_for_us(packet);
break;
case IP_P_OSPF:
ospf_handle_incoming_packet(packet);
break;
default:
icmp_send_port_unreachable(packet);
}
}
}
}
void processForward(struct sr_instance* sr,
uint8_t * packet,
unsigned int len,
char* interface) {
struct sr_ip_hdr *ipHeader = (struct sr_ip_hdr *) (packet + sizeof(struct sr_ethernet_hdr));
/* Reply with timeout if TTL exceeded */
ipHeader->ip_ttl = ipHeader->ip_ttl - 1;
if (ipHeader->ip_ttl == 0) {
icmp_send_time_exceeded(sr, packet, len, interface);
return;
}
/* At this point, all checks passed, check routing table */
struct sr_rt *closestMatch = findLongestMatchPrefix(sr->routing_table, ipHeader->ip_dst);
if (closestMatch == NULL) {
/* No match found. Send net unreachable */
icmp_send_net_unreachable(sr, packet, len, interface);
} else {
/* Match found. Lookup MAC address in ARP cache */
struct sr_arpentry *arpEntry = sr_arpcache_lookup(&(sr->cache), ntohl(closestMatch->gw.s_addr));
if (arpEntry != NULL) {
/* Found MAC address. Send the packet */
struct sr_rt *arpClosestMatch = findLongestMatchPrefix(sr->routing_table, ntohl(arpEntry->ip));
send_packet_to_dest(sr, packet, len, arpClosestMatch->interface, arpEntry->mac, ntohl(arpEntry->ip));
} else {
/* Could not find MAC address. Queue request for ARP */
sr_arpcache_queuereq(&(sr->cache), ntohl(closestMatch->gw.s_addr), packet, len, interface);
}
}
}
