/*
Expects everything but len in network order
*/
void send_time_exceeded(struct sr_instance *sr, uint8_t *pkt) {
/* Need to buffer enough space to include the unused 32 bits, the IP
header length, and 64 bits first bits of original datagrams data */
unsigned int packet_size = sizeof(sr_ethernet_hdr_t) +
sizeof(sr_ip_hdr_t) + sizeof(sr_icmp_hdr_t)
+ UNUSED_BYTE_LENGTH_TIME_EXCEEDED_ICMP + ICMP_DATA_SIZE;
uint8_t *outgoing_pkt = malloc(packet_size);
sr_ethernet_hdr_t *outgoing_eth_hdr = get_ethernet_hdr(outgoing_pkt);
sr_ip_hdr_t *outgoing_ip_hdr = get_ip_hdr(outgoing_pkt);
sr_icmp_hdr_t *outgoing_icmp_hdr = get_icmp_hdr(outgoing_pkt);
uint32_t ip_dst = get_ip_hdr(pkt)->ip_src;
struct sr_rt *outgoing_routing_entry = find_lpm_in_routing_table(sr->routing_table, ntohl(ip_dst));
if (!outgoing_routing_entry) {
free(pkt);
free(outgoing_pkt);
return;
}
struct sr_if *outgoing_inf = sr_get_interface(sr, outgoing_routing_entry->interface);
/*Ethernet*/
memcpy(outgoing_eth_hdr->ether_shost, outgoing_inf->addr, ETHER_ADDR_LEN);
outgoing_eth_hdr->ether_type = htons(ethertype_ip);
/*IP*/
populate_ip_hdr_normal(outgoing_ip_hdr);
outgoing_ip_hdr->ip_len = htons(packet_size - sizeof(sr_ethernet_hdr_t));
outgoing_ip_hdr->ip_p = ip_protocol_icmp;
outgoing_ip_hdr->ip_sum = 0;
outgoing_ip_hdr->ip_src = outgoing_inf->ip;
outgoing_ip_hdr->ip_dst = ip_dst;
outgoing_ip_hdr->ip_sum = cksum(outgoing_ip_hdr, sizeof(sr_ip_hdr_t));
/*ICMP*/
outgoing_icmp_hdr->icmp_type = ICMP_TYPE_TIME_EXCEEDED;
outgoing_icmp_hdr->icmp_code = ICMP_CODE_TIME_EXCEEDED;
outgoing_icmp_hdr->icmp_sum = 0;
memset((char *)outgoing_icmp_hdr + sizeof(sr_icmp_hdr_t), 0, UNUSED_BYTE_LENGTH_TIME_EXCEEDED_ICMP);
memcpy((char *)outgoing_icmp_hdr + sizeof(sr_icmp_hdr_t) + UNUSED_BYTE_LENGTH_TIME_EXCEEDED_ICMP,
get_ip_hdr(pkt), ICMP_DATA_SIZE);
outgoing_icmp_hdr->icmp_sum = cksum(outgoing_icmp_hdr,
sizeof(sr_icmp_hdr_t) + UNUSED_BYTE_LENGTH_TIME_EXCEEDED_ICMP + ICMP_DATA_SIZE);
send_or_queue_packet_based_on_arp_entry_existence(sr, outgoing_routing_entry,
outgoing_pkt, packet_size);
}
/*
Expects entire ethernet frame, still in network order.
*/
void handle_ip_packet_destined_to_router(struct sr_instance *sr, uint8_t *pkt, sr_ip_hdr_t *ip_hdr, unsigned int len) {
if (ip_hdr->ip_p == ip_protocol_icmp) {
sr_icmp_hdr_t *icmp_hdr = get_icmp_hdr(pkt);
if (icmp_packet_echo_request_sanity_check(icmp_hdr, len) && icmp_hdr->icmp_type == ICMP_TYPE_ECHO_REQUEST && icmp_hdr->icmp_code == ICMP_CODE_ECHO_REQUEST) {
send_echo_reply(sr, pkt, len);
}
} else if (ip_hdr->ip_p == ip_protocol_tcp ||
ip_hdr->ip_p == ip_protocol_udp) {
send_icmp_port_unreachable(sr, pkt, len);
} else {
printf("unexpected protocol in ip hdr.\n");
}
}
/*
Expects everything but len in network order
*/
void send_echo_reply(struct sr_instance *sr, uint8_t *pkt, unsigned int len) {
uint8_t *outgoing_pkt = malloc(len);
sr_ethernet_hdr_t *outgoing_eth_hdr = get_ethernet_hdr(outgoing_pkt);
sr_ip_hdr_t *outgoing_ip_hdr = get_ip_hdr(outgoing_pkt);
sr_icmp_hdr_t *outgoing_icmp_hdr = get_icmp_hdr(outgoing_pkt);
uint32_t ip_dst = get_ip_hdr(pkt)->ip_src;
struct sr_rt *outgoing_routing_entry = find_lpm_in_routing_table(sr->routing_table, ntohl(ip_dst));
if (!outgoing_routing_entry) {
free(pkt);
free(outgoing_pkt);
return;
}
struct sr_if *outgoing_inf = sr_get_interface(sr, outgoing_routing_entry->interface);
/*Ethernet*/
memcpy(outgoing_eth_hdr->ether_shost, outgoing_inf->addr, ETHER_ADDR_LEN);
outgoing_eth_hdr->ether_type = htons(ethertype_ip);
/*IP*/
populate_ip_hdr_normal(outgoing_ip_hdr);
outgoing_ip_hdr->ip_len = htons(len - sizeof(sr_ethernet_hdr_t));
outgoing_ip_hdr->ip_p = ip_protocol_icmp;
outgoing_ip_hdr->ip_sum = 0;
outgoing_ip_hdr->ip_src = get_ip_hdr(pkt)->ip_dst;
outgoing_ip_hdr->ip_dst = ip_dst;
outgoing_ip_hdr->ip_sum = cksum(outgoing_ip_hdr, sizeof(sr_ip_hdr_t));
/*ICMP*/
outgoing_icmp_hdr->icmp_type = ICMP_TYPE_ECHO_REPLY;
outgoing_icmp_hdr->icmp_code = ICMP_CODE_ECHO_REPLY;
outgoing_icmp_hdr->icmp_sum = 0;
memcpy((char *)outgoing_icmp_hdr + sizeof(sr_icmp_hdr_t), pkt +
sizeof(sr_ethernet_hdr_t) + sizeof(sr_ip_hdr_t) +
sizeof(sr_icmp_hdr_t), len - sizeof(sr_ethernet_hdr_t) - sizeof(sr_ip_hdr_t) -
sizeof(sr_icmp_hdr_t));
outgoing_icmp_hdr->icmp_sum = cksum(outgoing_icmp_hdr,
ntohs(outgoing_ip_hdr->ip_len) - sizeof(sr_ip_hdr_t));
send_or_queue_packet_based_on_arp_entry_existence(sr, outgoing_routing_entry,
outgoing_pkt, len);
}
void print_sping_queue(struct sr_instance *sr)
{
assert(sr);
printf("\n\n*******\nSPING QUEUE CONTENTS\n");
router_state *rs = get_router_state(sr);
node *sping_walker = 0;
sping_queue_entry *ae = 0;
sping_walker = rs->sping_queue;
while(sping_walker)
{
ae = (sping_queue_entry *)sping_walker->data;
uint8_t *data =(uint8_t*) get_icmp_hdr(ae->packet, ae->len);
data = data+sizeof(icmp_hdr);
unsigned short *id = (unsigned short *)data;
printf("%X\n", *id);
sping_walker = sping_walker->next;
}
}
/* PRETTY PRINT ICMP PACKET HEADER */
void print_icmp_load(const uint8_t *packet, unsigned int len)
{
assert(packet);
icmp_hdr *icmp = get_icmp_hdr(packet, len);
indent(1);
printf("ICMP Packet Header (%d bytes)\n", sizeof(icmp_hdr));
indent(2);
switch(icmp->icmp_type) {
case ICMP_TYPE_ECHO_REPLY:
{
printf("Type = Echo reply\n");
indent(2);
printf("Code = %d\n", icmp->icmp_code);
break;
}
case ICMP_TYPE_ECHO_REQUEST:
{
printf("Type = Echo request\n");
indent(2);
printf("Code = %d\n", icmp->icmp_code);
break;
}
case ICMP_TYPE_TIME_EXCEEDED:
{
printf("Type = Time exceeded\n");
indent(2);
printf("Code = %d\n", icmp->icmp_code);
break;
}
case ICMP_TYPE_DESTINATION_UNREACHABLE:
{
printf("Type = Destination unreachable\n");
indent(2);
switch(icmp->icmp_code) {
case 0:
{
printf("Code = Network unreachable\n error\n");
break;
}
case 1:
{
printf("Code = Host unreachable error\n");
break;
}
case 2:
{
printf("Code = Protocol unreachable error\n");
break;
}
case 3:
{
printf("Code = Port unreachable error\n");
break;
}
} /* end of switch(icmp->icmp_code)) */
break;
}
default:
{
printf("Type = %d\n", icmp->icmp_type);
indent(2);
printf("Code = %d\n", icmp->icmp_code);
break;
}
}/* end of switch(icmp->icmp_type)) */
indent(2);
printf("Checksum = 0x%X\n", htons(icmp->icmp_sum));
indent(2);
uint8_t* data = (uint8_t *) icmp;
data += sizeof(icmp_hdr);
int data_len = len - (sizeof(eth_hdr)+sizeof(ip_hdr)+sizeof(icmp_hdr));
printf("\nPayload 1(%d bytes)\n", data_len);
int i; for(i=0; i<data_len; i++)
{ printf("%X ", data[i]); }
printf("\n\n");
}
/*
* HELPER function called from arp_thread
*/
void process_arp_queue(struct sr_instance* sr) {
router_state* rs = get_router_state(sr);
node* n = get_router_state(sr)->arp_queue;
node* next = NULL;
time_t now;
double diff;
while (n) {
next = n->next;
arp_queue_entry* aqe = (arp_queue_entry*)n->data;
/* has it been over a second since the last arp request was sent? */
time(&now);
diff = difftime(now, aqe->last_req_time);
if (diff > 1) {
/* have we sent less than 5 arp requests? */
if (aqe->requests < 5) {
/* send another */
time(&(aqe->last_req_time));
++(aqe->requests);
send_arp_request(sr, aqe->next_hop.s_addr, aqe->out_iface_name);
} else {
/* we have exceeded the max arp requests, return packets to sender */
node* cur_packet_node = aqe->head;
node* next_packet_node = NULL;
while (cur_packet_node) {
/* send icmp for the packet, free it, and its encasing entry */
arp_queue_packet_entry* aqpe = (arp_queue_packet_entry*)cur_packet_node->data;
/* only send an icmp error if the packet is not icmp, or if it is, its an echo request or reply
* also ensure we don't send an icmp error back to one of our interfaces
*/
if ((get_ip_hdr(aqpe->packet, aqpe->len)->ip_p != IP_PROTO_ICMP) ||
(get_icmp_hdr(aqpe->packet, aqpe->len)->icmp_type == ICMP_TYPE_ECHO_REPLY) ||
(get_icmp_hdr(aqpe->packet, aqpe->len)->icmp_type == ICMP_TYPE_ECHO_REQUEST)) {
/* also ensure we don't send an icmp error back to one of our interfaces */
if (!iface_match_ip(rs, get_ip_hdr(aqpe->packet, aqpe->len)->ip_src.s_addr)) {
/* Total hack here to increment the TTL since we already decremented it earlier in the pipeline
* and the ICMP error should return the original packet.
* TODO: Don't decrement the TTL until the packet is ready to be put on the wire
* and we have the next hop ARP address, although checking should be done
* where it is currently being decremented to minimize effort on a doomed packet */
ip_hdr *ip = get_ip_hdr(aqpe->packet, aqpe->len);
if (ip->ip_ttl < 255) {
ip->ip_ttl++;
/* recalculate checksum */
bzero(&ip->ip_sum, sizeof(uint16_t));
uint16_t checksum = htons(compute_ip_checksum(ip));
ip->ip_sum = checksum;
}
send_icmp_packet(sr, aqpe->packet, aqpe->len, ICMP_TYPE_DESTINATION_UNREACHABLE, ICMP_CODE_HOST_UNREACHABLE);
}
}
free(aqpe->packet);
next_packet_node = cur_packet_node->next;
//free(cur_packet_node); /* IS THIS CORRECT TO FREE IT ? */
node_remove(&(aqe->head), cur_packet_node);
cur_packet_node = next_packet_node;
}
/* free the arp queue entry for this destination ip, and patch the list */
node_remove(&(get_router_state(sr)->arp_queue), n);
}
}
n = next;
}
}
/* Handle IP packet */
void sr_handle_ippacket(struct sr_instance* sr,
uint8_t * packet/* lent */,
unsigned int len,
char* interface/* lent */)
{
assert(sr);
assert(packet);
assert(interface);
/* Get ethernet header */
sr_ethernet_hdr_t *eth_hdr = get_eth_hdr(packet);
if (eth_hdr == NULL) {
printf("ethernet header NULL!!!\n");
return;
}
/* Get ip header */
sr_ip_hdr_t *ip_hdr = get_ip_hdr(packet);
if (ip_hdr == NULL) {
printf("ip header NULL!!!\n");
return;
}
/* Before doing ttl decrement, check checksum */
uint16_t old_ip_sum = ip_hdr->ip_sum;
ip_hdr->ip_sum = 0;
if (!verify_checksum(ip_hdr, sizeof(sr_ip_hdr_t), old_ip_sum)) {
fprintf(stderr, "CHECKSUM FAILED!!\n");
return;
}
ip_hdr->ip_sum = old_ip_sum;
/* Get the arp cache */
struct sr_arpcache *sr_arp_cache = &sr->cache;
/* Get the destination interface on the router */
struct sr_if *sr_iface = sr_get_router_if(sr, ip_hdr->ip_dst);
/* Get the connected interface on the router */
struct sr_if *sr_con_if = sr_get_interface(sr, interface);
/* Check the time exceeded condition, if ttl==0, we need to form icmp 11 and send back */
if (ip_hdr->ip_ttl <= 1) {
/* time exceeded message and icmp type 11 */
printf("TTL time exceeded\n");
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
create_ethernet_hdr(eth_hdr, (sr_ethernet_hdr_t *)icmp_t3_hdr, sr_con_if);
/* Create ip header */
create_echo_ip_hdr(ip_hdr, (sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN), sr_con_if);
/* Send icmp type 11 time exceeded */
/* icmp_t3 type=11, code=0 */
create_icmp_t3_hdr(ip_hdr, (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr+IP_PACKET_LEN), 11, 0);
/* Send icmp type 11 packet */
struct sr_arpentry *arp_entry = sr_arpcache_lookup(sr_arp_cache, ip_hdr->ip_src);
if (arp_entry != NULL) {
sr_send_packet(sr, icmp_t3_hdr, packet_len, sr_con_if->name);
free(icmp_t3_hdr);
} else {
struct sr_arpreq *arp_req = sr_arpcache_queuereq(sr_arp_cache, ip_hdr->ip_src, icmp_t3_hdr, packet_len, sr_con_if->name);
handle_arpreq(arp_req, sr);
}
return;
}
/* Get the protocol from IP */
uint8_t ip_p = ip_hdr->ip_p;
/* If the packet is sent to self, meaning the ip is sent to the router */
if (sr_iface) {
/* Check the protocol if it is icmp */
if (ip_p == ip_protocol_icmp) {
/* Get the icmp header */
sr_icmp_hdr_t *icmp_hdr = get_icmp_hdr(packet);
/* Check if it is ICMP echo request */
/* icmp_echo_req = 8 */
if (icmp_hdr->icmp_type == 8) {
/* Do LPM on the routing table */
/* Check the routing table and see if the incoming ip matches the routing table ip, and find LPM router entry */
struct sr_rt *longest_pref_match = sr_lpm(sr, ip_hdr->ip_src);
if (longest_pref_match) {
/* check ARP cache */
struct sr_arpentry *arp_entry = sr_arpcache_lookup(&sr->cache, longest_pref_match->gw.s_addr);
struct sr_if *out_iface = sr_get_interface(sr, longest_pref_match->interface);
/* If hit, meaning the arp mapping has been cached */
if (arp_entry != NULL) {
/* We need to send the icmp echo reply */
/* Modify ethernet header */
memcpy(eth_hdr->ether_dhost, eth_hdr->ether_shost, ETHER_ADDR_LEN);
memcpy(eth_hdr->ether_shost, out_iface->addr, ETHER_ADDR_LEN);
/* Modify ip header */
ip_hdr->ip_off = htons(0b0100000000000000); /* fragment offset field */
ip_hdr->ip_ttl = 100; /* time to live */
uint32_t temp = ip_hdr->ip_src;
ip_hdr->ip_src = ip_hdr->ip_dst; /* source address */
ip_hdr->ip_dst = temp; /* dest address */
ip_hdr->ip_sum = 0;
ip_hdr->ip_sum = cksum(ip_hdr, sizeof(sr_ip_hdr_t)); /* checksum */
/* Modify icmp header */
unsigned int icmp_whole_size = len - IP_PACKET_LEN;
icmp_hdr->icmp_type = 0;
icmp_hdr->icmp_code = 0;
icmp_hdr->icmp_sum = 0;
icmp_hdr->icmp_sum = cksum(icmp_hdr, icmp_whole_size);
/* Send icmp echo reply */
sr_send_packet(sr, packet, len, out_iface->name);
return;
}
/* Else no hit, we cache it to the queue and send arp request */
else {
/* Add reply to the ARP queue */
/* We need to send the icmp echo reply */
/* Modify ethernet header */
memcpy(eth_hdr->ether_dhost, eth_hdr->ether_shost, ETHER_ADDR_LEN);
memcpy(eth_hdr->ether_shost, sr_con_if->addr, ETHER_ADDR_LEN);
/* Modify ip header */
ip_hdr->ip_off = htons(0b0100000000000000); /* fragment offset field */
ip_hdr->ip_ttl = 100; /* time to live */
uint32_t temp = ip_hdr->ip_src;
ip_hdr->ip_src = ip_hdr->ip_dst; /* source address */
ip_hdr->ip_dst = temp; /* dest address */
ip_hdr->ip_sum = 0;
ip_hdr->ip_sum = cksum(ip_hdr, sizeof(sr_ip_hdr_t)); /* checksum */
/* Modify icmp header */
unsigned int icmp_whole_size = len - IP_PACKET_LEN;
icmp_hdr->icmp_type = 0;
icmp_hdr->icmp_code = 0;
icmp_hdr->icmp_sum = 0;
icmp_hdr->icmp_sum = cksum(icmp_hdr, icmp_whole_size);
struct sr_arpreq *arp_req = sr_arpcache_queuereq(sr_arp_cache, ip_hdr->ip_dst, packet, len, out_iface->name);
/* Send ARP request, which is a broadcast */
handle_arpreq(arp_req, sr);
return;
}
} else {
fprintf(stderr, "Longest prefix doesnt match!!\n");
return;
}
} else {
fprintf(stderr, "Not an ICMP request!\n");
return;
}
}
/* Else it is TCP/UDP request */
else {
fprintf(stderr, "*** -> Received TCP/UDP!\n");
/* Do LPM on the routing table */
/* Check the routing table and see if the incoming ip matches the routing table ip, and find LPM router entry */
struct sr_rt *longest_pref_match = sr_lpm(sr, ip_hdr->ip_src);
if (longest_pref_match) {
/* check ARP cache */
struct sr_arpentry *arp_entry = sr_arpcache_lookup(&sr->cache, longest_pref_match->gw.s_addr);
struct sr_if *out_iface = sr_get_interface(sr, longest_pref_match->interface);
/* Send ICMP port unreachable */
if (arp_entry != NULL) {
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
/* Create ethernet header */
create_ethernet_hdr(eth_hdr, (sr_ethernet_hdr_t *)icmp_t3_hdr, sr_iface);
/*memcpy(((sr_ethernet_hdr_t *)icmp_t3_hdr)->ether_dhost, eth_hdr->ether_shost, ETHER_ADDR_LEN);
memcpy(((sr_ethernet_hdr_t *)icmp_t3_hdr)->ether_shost, eth_hdr->ether_dhost, ETHER_ADDR_LEN);*/
/* Create ip header */
create_echo_ip_hdr(ip_hdr, (sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN), sr_iface);
/*sr_ip_hdr_t *icmp_t3_hdr_ip = (sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN);
icmp_t3_hdr_ip->ip_src = ip_hdr->ip_dst;
icmp_t3_hdr_ip->ip_sum = 0;
icmp_t3_hdr_ip->ip_sum = cksum(icmp_t3_hdr_ip, sizeof(sr_ip_hdr_t));*/
/* Should update source address to be interface address */
/* Send icmp type 3 port unreachable */
/* Create icmp port unreachable packet */
/* icmp_t3 type=3, code=3 */
create_icmp_t3_hdr(ip_hdr, (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr+IP_PACKET_LEN), 3, 3);
/* Send icmp type 3 packet */
sr_send_packet(sr, icmp_t3_hdr, packet_len, out_iface->name);
free(icmp_t3_hdr);
return;
} else {
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
/* Create ethernet header */
create_ethernet_hdr(eth_hdr, (sr_ethernet_hdr_t *)icmp_t3_hdr, sr_iface);
/*memcpy(((sr_ethernet_hdr_t *)icmp_t3_hdr)->ether_dhost, eth_hdr->ether_shost, ETHER_ADDR_LEN);
memcpy(((sr_ethernet_hdr_t *)icmp_t3_hdr)->ether_shost, eth_hdr->ether_dhost, ETHER_ADDR_LEN);*/
/* Create ip header */
create_echo_ip_hdr(ip_hdr, (sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN), sr_iface);
/*sr_ip_hdr_t *icmp_t3_hdr_ip = (sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN);
icmp_t3_hdr_ip->ip_src = ip_hdr->ip_dst;
icmp_t3_hdr_ip->ip_sum = 0;
icmp_t3_hdr_ip->ip_sum = cksum(icmp_t3_hdr_ip, sizeof(sr_ip_hdr_t));*/
/* Send icmp type 3 port unreachable */
/* Create icmp port unreachable packet */
/* icmp_t3 type=3, code=3 */
create_icmp_t3_hdr(ip_hdr, (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr+IP_PACKET_LEN), 3, 3);
struct sr_arpreq *arp_req = sr_arpcache_queuereq(sr_arp_cache, ip_hdr->ip_src, icmp_t3_hdr, packet_len, out_iface->name);
/* Send ARP request, which is a broadcast */
handle_arpreq(arp_req, sr);
return;
}
} else {
fprintf(stderr, "Longest prefix doesnt match!!\n");
return;
}
}
}
/* Else Check the routing table, perfomr LPM */
else {
/* Sanity-check the packet */
/* minimum length */
if (!check_min_length(len, IP_PACKET_LEN)) {
fprintf(stderr, "The packet length is not enough:(\n");
return;
}
/* Do LPM on the routing table */
/* Check the routing table and see if the incoming ip matches the routing table ip, and find LPM router entry */
struct sr_rt *longest_pref_match = sr_lpm(sr, ip_hdr->ip_dst);
if (longest_pref_match) {
/* check ARP cache */
struct sr_if *out_iface = sr_get_interface(sr, longest_pref_match->interface);
struct sr_arpentry *arp_entry = sr_arpcache_lookup(&sr->cache, longest_pref_match->gw.s_addr); /* ip_hdr->ip_dst */
/* If hit, meaning the arp_entry is found */
if (arp_entry) {
/*fprintf(stderr, "************ found the lpm router entry ***********\n");*/
/* Send frame to next hop */
/* update the eth_hdr source and destination ethernet address */
/* use next_hop_ip->mac mapping in the entry to send the packet */
ip_hdr->ip_ttl--;
/* recompute the packet checksum over the modified header */
ip_hdr->ip_sum = 0;
uint16_t new_ip_sum = cksum(ip_hdr, sizeof(sr_ip_hdr_t));
ip_hdr->ip_sum = new_ip_sum;
memcpy(eth_hdr->ether_shost, out_iface->addr, ETHER_ADDR_LEN);
memcpy(eth_hdr->ether_dhost, arp_entry->mac, ETHER_ADDR_LEN);
sr_send_packet(sr, packet, len, out_iface->name);
print_hdr_ip((uint8_t*)ip_hdr);
/* free the entry */
free(arp_entry);
return;
} else/* No Hit */ {
/* send an ARP request for the next-hop IP */
/* add the packet to the queue of packets waiting on this ARP request */
/* Add request to ARP queue*/
ip_hdr->ip_ttl--;
/* recompute the packet checksum over the modified header */
ip_hdr->ip_sum = 0;
uint16_t new_ip_sum = cksum(ip_hdr, sizeof(sr_ip_hdr_t));
ip_hdr->ip_sum = new_ip_sum;
struct sr_arpreq *arp_req = sr_arpcache_queuereq(sr_arp_cache, ip_hdr->ip_dst, packet, len, out_iface->name);
/* send ARP request, this is a broadcast */
handle_arpreq(arp_req, sr);
return;
}
} else /* if not matched */ {
/* Send ICMP net unreachable */
printf("--------------- Net Unreachable ---------------\n");
/* Do LPM on the routing table */
/* Check the routing table and see if the incoming ip matches the routing table ip, and find LPM router entry */
struct sr_rt *longest_pref_match = sr_lpm(sr, ip_hdr->ip_src);
if (longest_pref_match) {
/* check ARP cache */
struct sr_arpentry *arp_entry = sr_arpcache_lookup(&sr->cache, longest_pref_match->gw.s_addr);
struct sr_if *out_iface = sr_get_interface(sr, longest_pref_match->interface);
if (arp_entry) {
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
/* Create ethernet header */
create_ethernet_hdr(eth_hdr, (sr_ethernet_hdr_t *)icmp_t3_hdr, out_iface);
/* Create ip header */
create_echo_ip_hdr(ip_hdr, (sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN), out_iface);
/* Create icmp net unreachable */
/* icmp_t3 type=3, code=0 */
create_icmp_t3_hdr(ip_hdr, (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr+IP_PACKET_LEN), 3, 0);
/* Send icmp type 3 packet */
sr_send_packet(sr, icmp_t3_hdr, packet_len, out_iface->name);
free(icmp_t3_hdr);
return;
} else {
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
/* Create ethernet header */
create_ethernet_hdr(eth_hdr, (sr_ethernet_hdr_t *)icmp_t3_hdr, out_iface);
/* Create ip header */
create_echo_ip_hdr(ip_hdr, (sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN), out_iface);
/* ((sr_ip_hdr_t *)((char *)icmp_t3_hdr+ETHER_PACKET_LEN))->ip_ttl += 1; */
/* Send icmp type 3 net unreachable */
/* Create icmp net unreachable packet */
/* icmp_t3 type=3, code=0 */
create_icmp_t3_hdr(ip_hdr, (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr+IP_PACKET_LEN), 3, 0);
struct sr_arpreq *arp_req = sr_arpcache_queuereq(sr_arp_cache, ip_hdr->ip_src, icmp_t3_hdr, packet_len, out_iface->name);
/* Send ARP request, which is a broadcast */
handle_arpreq(arp_req, sr);
return;
}
} else {
fprintf(stderr, "Longest prefix doesnt match!!\n");
return;
}
}
}
return;
}