/* 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;
}
void *sr_nat_timeout(void *sr_ptr) { /* Periodic Timout handling */
struct sr_instance *sr = (struct sr_instance *)sr_ptr;
struct sr_nat *nat = sr->nat;
while (1) {
sleep(1.0);
pthread_mutex_lock(&(nat->lock));
/* handle periodic tasks here */
time_t curtime = time(NULL);
struct sr_tcp_unsolicited_packet *my_pkt = nat->unsolicited_packet;
/* if my_pkt is NULL, finish! */
if (my_pkt == NULL) {
pthread_mutex_unlock(&(nat->lock));
}
else {
/* get the next packet */
struct sr_tcp_unsolicited_packet *next_pkt = my_pkt->next;
/* if next pkt is NULL, only check my_pkt */
if (next_pkt == NULL) {
time_t pkt_time = my_pkt->time_updated;
/* if the time difference is bigger than 6 seconds */
if (difftime(curtime, pkt_time) >= 6) {
/* get all the headers */
uint8_t *packet = my_pkt->buf;
sr_ethernet_hdr_t *eth_hdr = get_eth_hdr(packet);
sr_ip_hdr_t *ip_hdr = get_ip_hdr(packet);
/* create a new icmp t3 port unreachable */
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
/* create ethernet header */
sr_ethernet_hdr_t *new_eth_hdr = (sr_ethernet_hdr_t *)icmp_t3_hdr;
memcpy(new_eth_hdr->ether_dhost, eth_hdr->ether_shost, ETHER_ADDR_LEN);
memcpy(new_eth_hdr->ether_shost, eth_hdr->ether_dhost, ETHER_ADDR_LEN);
/* create ip header */
sr_ip_hdr_t *new_ip_hdr = (sr_ip_hdr_t *)((char *)icmp_t3_hdr + ETHER_PACKET_LEN);
new_ip_hdr->ip_hl = ip_hdr->ip_hl; /* header length */
new_ip_hdr->ip_v = ip_hdr->ip_v; /* header version */
new_ip_hdr->ip_tos = ip_hdr->ip_tos; /* type of service */
new_ip_hdr->ip_len = htons(56); /* total length */
new_ip_hdr->ip_id = 0; /* identification */
new_ip_hdr->ip_off = htons(0b0100000000000000); /* fragment offset field */
new_ip_hdr->ip_ttl = 64; /* time to live */
new_ip_hdr->ip_p = ip_protocol_icmp; /* protocol */
new_ip_hdr->ip_src = ip_hdr->ip_dst; /* source address */
new_ip_hdr->ip_dst = ip_hdr->ip_src; /* dest address */
new_ip_hdr->ip_sum = 0;
new_ip_hdr->ip_sum = cksum(new_ip_hdr, sizeof(sr_ip_hdr_t));; /* checksum */
/* create icmp t3 header */
sr_icmp_t3_hdr_t *new_icmp_t3_hdr = (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr + IP_PACKET_LEN);
new_icmp_t3_hdr->icmp_type = htons(3);
new_icmp_t3_hdr->icmp_code = htons(3);
new_icmp_t3_hdr->unused = 0;
new_icmp_t3_hdr->next_mtu = 0;
memcpy(new_icmp_t3_hdr->data, new_ip_hdr, ICMP_DATA_SIZE);
new_icmp_t3_hdr->icmp_sum = 0;
new_icmp_t3_hdr->icmp_sum = cksum(new_icmp_t3_hdr, sizeof(sr_icmp_t3_hdr_t));
struct sr_if *out_iface = sr_get_router_if(sr, ip_hdr->ip_dst);
sr_send_packet(sr, icmp_t3_hdr, packet_len, out_iface->name);
/* set unsolicited_packet to be NULL */
nat->unsolicited_packet = NULL;
}
pthread_mutex_unlock(&(nat->lock));
}
/* otherwise we need to loop through the packets */
else {
struct sr_tcp_unsolicited_packet *prev_pkt = my_pkt;
while (next_pkt != NULL) {
time_t pkt_time = my_pkt->time_updated;
/* if the time difference is bigger than 6 seconds */
if (difftime(curtime, pkt_time) >= 6) {
/* get all the headers */
uint8_t *packet = my_pkt->buf;
sr_ethernet_hdr_t *eth_hdr = get_eth_hdr(packet);
sr_ip_hdr_t *ip_hdr = get_ip_hdr(packet);
/* create a new icmp t3 port unreachable */
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
/* create ethernet header */
sr_ethernet_hdr_t *new_eth_hdr = (sr_ethernet_hdr_t *)icmp_t3_hdr;
memcpy(new_eth_hdr->ether_dhost, eth_hdr->ether_shost, ETHER_ADDR_LEN);
memcpy(new_eth_hdr->ether_shost, eth_hdr->ether_dhost, ETHER_ADDR_LEN);
/* create ip header */
sr_ip_hdr_t *new_ip_hdr = (sr_ip_hdr_t *)((char *)icmp_t3_hdr + ETHER_PACKET_LEN);
new_ip_hdr->ip_hl = ip_hdr->ip_hl; /* header length */
new_ip_hdr->ip_v = ip_hdr->ip_v; /* header version */
new_ip_hdr->ip_tos = ip_hdr->ip_tos; /* type of service */
new_ip_hdr->ip_len = htons(56); /* total length */
new_ip_hdr->ip_id = 0; /* identification */
new_ip_hdr->ip_off = htons(0b0100000000000000); /* fragment offset field */
new_ip_hdr->ip_ttl = 64; /* time to live */
new_ip_hdr->ip_p = ip_protocol_icmp; /* protocol */
new_ip_hdr->ip_src = ip_hdr->ip_dst; /* source address */
new_ip_hdr->ip_dst = ip_hdr->ip_src; /* dest address */
new_ip_hdr->ip_sum = 0;
new_ip_hdr->ip_sum = cksum(new_ip_hdr, sizeof(sr_ip_hdr_t));; /* checksum */
/* create icmp t3 header */
sr_icmp_t3_hdr_t *new_icmp_t3_hdr = (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr + IP_PACKET_LEN);
new_icmp_t3_hdr->icmp_type = htons(3);
new_icmp_t3_hdr->icmp_code = htons(3);
new_icmp_t3_hdr->unused = 0;
new_icmp_t3_hdr->next_mtu = 0;
memcpy(new_icmp_t3_hdr->data, new_ip_hdr, ICMP_DATA_SIZE);
new_icmp_t3_hdr->icmp_sum = 0;
new_icmp_t3_hdr->icmp_sum = cksum(new_icmp_t3_hdr, sizeof(sr_icmp_t3_hdr_t));
struct sr_if *out_iface = sr_get_router_if(sr, ip_hdr->ip_dst);
sr_send_packet(sr, icmp_t3_hdr, packet_len, out_iface->name);
/* unlist the my_pkt */
if (my_pkt == nat->unsolicited_packet) {
nat->unsolicited_packet = next_pkt;
prev_pkt = next_pkt;
my_pkt = next_pkt;
next_pkt = next_pkt->next;
} else {
prev_pkt->next = next_pkt;
my_pkt = next_pkt;
next_pkt = next_pkt->next;
}
}
prev_pkt = my_pkt;
my_pkt = next_pkt;
next_pkt = next_pkt->next;
}
time_t pkt_time = my_pkt->time_updated;
/* if the time difference is bigger than 6 seconds */
if (difftime(curtime, pkt_time) >= 6) {
/* get all the headers */
uint8_t *packet = my_pkt->buf;
sr_ethernet_hdr_t *eth_hdr = get_eth_hdr(packet);
sr_ip_hdr_t *ip_hdr = get_ip_hdr(packet);
/* create a new icmp t3 port unreachable */
int packet_len = ICMP_T3_PACKET_LEN;
uint8_t *icmp_t3_hdr = (uint8_t *)malloc(packet_len);
/* create ethernet header */
sr_ethernet_hdr_t *new_eth_hdr = (sr_ethernet_hdr_t *)icmp_t3_hdr;
memcpy(new_eth_hdr->ether_dhost, eth_hdr->ether_shost, ETHER_ADDR_LEN);
memcpy(new_eth_hdr->ether_shost, eth_hdr->ether_dhost, ETHER_ADDR_LEN);
/* create ip header */
sr_ip_hdr_t *new_ip_hdr = (sr_ip_hdr_t *)((char *)icmp_t3_hdr + ETHER_PACKET_LEN);
new_ip_hdr->ip_hl = ip_hdr->ip_hl; /* header length */
new_ip_hdr->ip_v = ip_hdr->ip_v; /* header version */
new_ip_hdr->ip_tos = ip_hdr->ip_tos; /* type of service */
new_ip_hdr->ip_len = htons(56); /* total length */
new_ip_hdr->ip_id = 0; /* identification */
new_ip_hdr->ip_off = htons(0b0100000000000000); /* fragment offset field */
new_ip_hdr->ip_ttl = 64; /* time to live */
new_ip_hdr->ip_p = ip_protocol_icmp; /* protocol */
new_ip_hdr->ip_src = ip_hdr->ip_dst; /* source address */
new_ip_hdr->ip_dst = ip_hdr->ip_src; /* dest address */
new_ip_hdr->ip_sum = 0;
new_ip_hdr->ip_sum = cksum(new_ip_hdr, sizeof(sr_ip_hdr_t));; /* checksum */
/* create icmp t3 header */
sr_icmp_t3_hdr_t *new_icmp_t3_hdr = (sr_icmp_t3_hdr_t *)((char *)icmp_t3_hdr + IP_PACKET_LEN);
new_icmp_t3_hdr->icmp_type = htons(3);
new_icmp_t3_hdr->icmp_code = htons(3);
new_icmp_t3_hdr->unused = 0;
new_icmp_t3_hdr->next_mtu = 0;
memcpy(new_icmp_t3_hdr->data, new_ip_hdr, ICMP_DATA_SIZE);
new_icmp_t3_hdr->icmp_sum = 0;
new_icmp_t3_hdr->icmp_sum = cksum(new_icmp_t3_hdr, sizeof(sr_icmp_t3_hdr_t));
struct sr_if *out_iface = sr_get_router_if(sr, ip_hdr->ip_dst);
sr_send_packet(sr, icmp_t3_hdr, packet_len, out_iface->name);
/* set the last packet to be NULL */
prev_pkt->next = NULL;
}
pthread_mutex_unlock(&(nat->lock));
}
}
}
return NULL;
}
