void send_icmp(void)
{
switch(opt_icmptype)
{
case ICMP_ECHO: /* type 8 */
case ICMP_ECHOREPLY: /* type 0 */
send_icmp_echo();
break;
case ICMP_DEST_UNREACH: /* type 3 */
case ICMP_SOURCE_QUENCH: /* type 4 */
case ICMP_REDIRECT: /* type 5 */
case ICMP_TIME_EXCEEDED: /* type 11 */
send_icmp_other();
break;
case ICMP_TIMESTAMP:
case ICMP_TIMESTAMPREPLY:
send_icmp_timestamp();
break;
case ICMP_ADDRESS:
case ICMP_ADDRESSREPLY:
send_icmp_address();
break;
default:
if (opt_force_icmp) {
send_icmp_other();
break;
} else {
printf("[send_icmp] Unsupported icmp type!\n");
exit(1);
}
}
}
void sr_handlepacket(struct sr_instance* sr, uint8_t * packet/* lent */,
unsigned int len, char* interface/* lent */) {
/* Function implemented by g1izzyw and gustan50404 */
/* REQUIRES */
assert(sr);
assert(packet);
assert(interface);
struct sr_if *ether_interface = (struct sr_if *) sr_get_interface(sr, interface);
/* Check if it an ethernet interface. */
if (ether_interface) {
/* Now we deal with the ethernet header */
struct sr_ethernet_hdr *ether_hdr = (struct sr_ethernet_hdr *) packet;
/* Check to see if we are dealing with an ARP request/reply */
if (ether_hdr->ether_type == htons(ethertype_arp)) {
fprintf(stderr, "We Got an ARP Packet\n");
/* Handle ARP for ethernet */
struct sr_arp_hdr * arp_hdr = (struct sr_arp_hdr *)(packet + sizeof(struct sr_ethernet_hdr));
if (arp_hdr->ar_hrd == htons(arp_hrd_ethernet)) {
if (arp_hdr->ar_op == htons(arp_op_request)) {
/* arp request */
struct sr_if *interface_for_ip = get_interface_for_ip(sr, arp_hdr->ar_tip);
if (interface_for_ip) {
/* Target ip is one of the router interfaces */
fprintf(stderr, "ARP req for one of our interfaces\n");
/* Now we want to make an arp reply and send it back */
uint8_t *buf = (uint8_t *) malloc(len);
memcpy(buf, packet, len);
/*Make Arp Header*/
make_arprply_hdr(interface_for_ip->addr, arp_hdr->ar_sha, interface_for_ip->ip,
arp_hdr->ar_sip, buf);
/*Make Ethernet Header*/
make_ether_hdr(interface_for_ip->addr, ether_hdr->ether_shost, ethertype_arp, buf);
/* Now we send the packet */
sr_send_packet(sr, buf, len, interface_for_ip->name);
free(buf);
fprintf(stderr, "ARP reply sent\n");
}
} else if (arp_hdr->ar_op == htons(arp_op_reply)) {
fprintf(stderr, "We got an ARP Reply, need to check for intfc tho \n");
/* arp reply */
struct sr_if *interface_for_ip = get_interface_for_ip(sr, arp_hdr->ar_tip);
if (interface_for_ip) {
fprintf(stderr, "We got an ARP Reply for one of our interfaces\n");
/*We first want to insert into Arp cache*/
struct sr_arpreq *request = sr_arpcache_insert(&(sr->cache),
arp_hdr->ar_sha,
arp_hdr->ar_sip);
fprintf(stderr, "Signalling all waiting packets\n");
if (request) {
struct sr_packet *cur_packet = request->packets;
while(cur_packet) {
fprintf(stderr, "About to forward \n");
print_hdrs(cur_packet->buf, cur_packet->len);
forward_packet(sr, cur_packet->iface, arp_hdr->ar_sha,
cur_packet->len, cur_packet->buf);
fprintf(stderr, "Packet Forwarded\n");
cur_packet = cur_packet->next;
}
}
}
}
}
} else if (ether_hdr->ether_type == htons(ethertype_ip)) {
/* Get the ip header from the ethernet header*/
sr_ip_hdr_t *ip_hdr = (sr_ip_hdr_t *)(packet + sizeof(sr_ethernet_hdr_t));
/*IP Checksum Stuff*/
uint16_t temp_ip_sum = ip_hdr->ip_sum;
ip_hdr->ip_sum = 0;
ip_hdr->ip_sum = cksum(packet + sizeof(sr_ethernet_hdr_t), sizeof(sr_ip_hdr_t));
if (temp_ip_sum == ip_hdr->ip_sum) {
/*We got here means IP Cheksum is alright, so we extract the interface*/
struct sr_if *interface_for_ip = get_interface_for_ip(sr, ip_hdr->ip_dst);
/*Check to make sure interface is one of ours*/
if (interface_for_ip) {
fprintf(stderr, "IP Packet destined towards our interface\n");
/*Check if our IP packet is UDP or TCP*/
if (ip_hdr->ip_p == 6 || ip_hdr->ip_p == 17) {
fprintf(stderr, "We Got TCP or UDP, sending ICMP error msg\n");
send_icmp_error(3, 3, sr, interface, len, packet);
} else {
/* Get the ICMP header */
sr_icmp_hdr_t *icmp_hdr = (struct sr_icmp_hdr *) (packet +
sizeof(sr_ethernet_hdr_t) +
sizeof(sr_ip_hdr_t));
/*Now we do the ICMP checksum chek*/
/*This covers the ICMP echo case*/
uint16_t temp_icmp_sum = icmp_hdr->icmp_sum;
temp_icmp_sum = icmp_hdr->icmp_sum;
icmp_hdr->icmp_sum = 0;
if (temp_icmp_sum == cksum(packet + sizeof(sr_ethernet_hdr_t) + sizeof(sr_ip_hdr_t),
len - sizeof(sr_ethernet_hdr_t) - sizeof(sr_ip_hdr_t))) {
/*Everything is fine so we send an ICMP echo back*/
fprintf(stderr, "Sending ICMP echo reply\n");
send_icmp_echo(sr, interface, len, packet);
}
}
} else {
/*IP Packet not destined towards one of our interfaces*/
fprintf(stderr, "IP packet not destined to our interface\n");
/*Decremenrt TTL by 1*/
fprintf(stderr, "TTL modified \n");
print_hdrs(packet, len);
if (ip_hdr->ip_ttl <= 1) {
fprintf(stderr, "Packte with TTL < 0 found, sending ICMP error \n");
/*TTL is less than 0 so send an ICMP ERROR*/
send_icmp_error(11, 0, sr, interface, len, packet);
} else {
/*Recompute Checksum over new header TTL is fine*/
/*Check if it exists in the routing table*/
ip_hdr->ip_ttl = ip_hdr->ip_ttl - 1;
fprintf(stderr, "Recomputing Checksum after modifying TTl\n");
ip_hdr->ip_sum = 0;
ip_hdr->ip_sum = cksum(packet + sizeof(sr_ethernet_hdr_t), sizeof(sr_ip_hdr_t));
struct sr_if *dst_if = (struct sr_if *)malloc(sizeof(struct sr_if));
dst_if = next_hop(sr, interface, ip_hdr->ip_dst);
if (!(dst_if)) {
fprintf(stderr, "IP packet has no longest matching prefix sending ICMP error\n");
/*dst ip has no longest macthing prefix*/
/*So we send a type 3 code 0 ICMP error*/
send_icmp_error(3, 0, sr, interface, len, packet);
} else {
/*This is the case where we do have a longest macthing prefix*/
fprintf(stderr, "Found Longest mathcing prefix in RT\n");
struct sr_arpcache *cache = &(sr->cache);
struct sr_arpentry *in_cache = sr_arpcache_lookup(cache, ip_hdr->ip_dst);
if (in_cache) {
fprintf(stderr, "Found IP->MAC mapping in ARP cache forwarding packet \n");
/*this is the case where ip->mac maping is already in cache*/
forward_packet(sr, dst_if->name, in_cache->mac, len, packet);
free(in_cache);
} else {
fprintf(stderr, "IP->MAC mapping not in ARP cache %u \n", ip_hdr->ip_dst);
/*Case where ip->mapping is not in cache*/
sr_arpcache_queuereq(cache, ip_hdr->ip_dst, packet, len, dst_if->name);
fprintf(stderr, "Added Arp Req to queu \n");
}
}
}
}
}
}
}
} /* end sr_ForwardPacket */
