void sr_handle_arpreq(struct sr_instance *sr, struct sr_arpreq *req){
/*Debug("\nsr_handle_arpreq called\n");*/
time_t now;
now = time(NULL);
struct sr_arpcache *cache = &(sr->cache);
/*if the arp_request has never been sent before or if the last time the
arp_request was sent was more than 1 second ago*/
if ((req->times_sent == 0)||(difftime(now, req->sent)> 1.0)){
/*Debug("\nARP request not previously sent or have not been sent within the last second\n");*/
if (req->times_sent >= 5)
{
/*Debug("\nARP request was sent 5 times previously; destroy ARP request\n");*/
/*loop through all of the IP packets waiting for the request,
call function to send ICMP msg -> host_unreachable*/
struct sr_packet *packet;
for(packet = req->packets; packet != NULL; packet = packet->next)
{
/*这里的interface是outgoing interface，有问题，send_icmp_message要的是in_interface*/
send_icmp_message(sr, packet->buf, sizeof(struct sr_packet), sr_get_interface(sr, req->packets->iface), ICMP_DESTINATION_UNREACHABLE_TYPE, ICMP_HOST_UNREACHABLE_CODE);
}
sr_arpreq_destroy(cache, req);
}
else
{
/*Debug("\nSending ARP request\n");*/
/*这里的interface是outgoing interface，有问题，send_icmp_message要的是in_interface*/
printf("interface: %s", req->packets->iface);
send_arp_request(sr, sr_get_interface(sr, req->packets->iface), req->ip);
req->sent = now;
req->times_sent++;
}
}
}
void handle_arpreq(struct sr_instance *sr, struct sr_arpreq *req) {
time_t now = time(NULL);
if (difftime(now, req->sent) >= 0.9) {
if (req->times_sent >= 5) {
struct sr_packet *pkt_pending = req->packets;
struct sr_if *interface = sr_get_interface(sr, pkt_pending->iface);
while (pkt_pending) {
icmp_handler(sr, pkt_pending->buf, 0, interface->ip, HOST_UNREACHABLE);
pkt_pending = pkt_pending->next;
}
sr_arpreq_destroy(&(sr->cache), req);
}
else {
int packet_len = sizeof(sr_ethernet_hdr_t) + sizeof(sr_arp_hdr_t);
uint8_t *pkt = malloc(packet_len);
struct sr_ethernet_hdr *eth_hdr = (struct sr_ethernet_hdr *)pkt;
struct sr_if *interface = sr_get_interface(sr, req->packets->iface);
uint8_t hrd_addr[ETHER_ADDR_LEN] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
enum sr_ethertype eth_arp = ethertype_arp;
enum sr_ethertype eth_ip = ethertype_ip;
memcpy(eth_hdr->ether_dhost, hrd_addr, ETHER_ADDR_LEN);
memcpy(eth_hdr->ether_shost, interface->addr, ETHER_ADDR_LEN);
eth_hdr->ether_type = htons(eth_arp);
struct sr_arp_hdr *arp_hdr = (struct sr_arp_hdr *)(sizeof(sr_ethernet_hdr_t) + pkt);
enum sr_arp_hrd_fmt hrd_eth = arp_hrd_ethernet;
enum sr_arp_opcode arp_op_req = arp_op_request;
arp_hdr->ar_hrd = htons(hrd_eth);
arp_hdr->ar_pro = htons(eth_ip);
arp_hdr->ar_hln = ETHER_ADDR_LEN;
arp_hdr->ar_pln = 4;
arp_hdr->ar_op = htons(arp_op_req);
arp_hdr->ar_sip = interface->ip;
arp_hdr->ar_tip = req->ip;
memcpy(arp_hdr->ar_sha, interface->addr, ETHER_ADDR_LEN);
memcpy(arp_hdr->ar_tha, hrd_addr, ETHER_ADDR_LEN);
printf("Sending Packets.. [3].\n");
sr_send_packet(sr, pkt, packet_len, interface->name);
free(pkt);
req->sent = now;
req->times_sent++;
}
}
}
/*---------------------------------------------------------------------
* Method: handle_arp_request
* Scope: local
*
* Handles an ARP request sent to an interface.
*
*---------------------------------------------------------------------*/
static void handle_arp_request(struct sr_instance *sr, struct sr_ethernet_hdr *ethernet_header,
struct sr_arphdr *arp_header, char *interface) {
printf("\tIt's an ARP request!\n");
// Get the interface address
struct sr_if* iface = sr_get_interface(sr, interface);
if ( iface == 0 ) {
fprintf( stderr, "** Error, interface %s, does not exist\n", interface);
}
// Create ARP reply :)
struct sr_arphdr arp_reply;
memcpy(&arp_reply, arp_header, sizeof(struct sr_arphdr));
arp_reply.ar_op = htons(ARP_REPLY);
memcpy(&arp_reply.ar_sha, iface->addr, ETHER_ADDR_LEN);
memcpy(&arp_reply.ar_tha, arp_header->ar_sha, ETHER_ADDR_LEN);
memcpy(&arp_reply.ar_sip, &(arp_header->ar_tip), sizeof(uint32_t));
memcpy(&arp_reply.ar_tip, &(arp_header->ar_sip), sizeof(uint32_t));
// Send the reply
uint8_t *buffer = pack_ethernet_packet(ethernet_header->ether_shost, iface->addr,
ETHERTYPE_ARP, (uint8_t *) &arp_reply, sizeof(struct sr_arphdr));
sr_send_packet(sr, buffer, sizeof(struct sr_ethernet_hdr) + sizeof(struct sr_arphdr),
interface);
}
/*
* Send ARP request.
*/
void send_arp_request(struct sr_instance *sr, uint32_t dst_ip, char *interface) {
uint8_t *packet = (uint8_t *)malloc(sizeof(sr_ethernet_hdr_t) + sizeof(sr_arp_hdr_t));
unsigned int len = sizeof(sr_ethernet_hdr_t) + sizeof(sr_arp_hdr_t);
struct sr_if *rt_if = (struct sr_if *)sr_get_interface(sr, interface);
uint8_t brdcst_addr[ETHER_ADDR_LEN];
int i = 0;
for(i; i < ETHER_ADDR_LEN; i++){
brdcst_addr[i] = 255;
}
/* Prepare ethernet header. */
sr_ethernet_hdr_t *ether_hdr = (sr_ethernet_hdr_t *)(packet);
ether_hdr->ether_type = htons(ethertype_arp);
memcpy(ether_hdr->ether_shost, rt_if->addr, ETHER_ADDR_LEN);
memcpy(ether_hdr->ether_dhost, brdcst_addr, ETHER_ADDR_LEN);
/* Prepare ARP header. */
sr_arp_hdr_t *arp_hdr = (sr_arp_hdr_t *)(packet + sizeof(sr_ethernet_hdr_t));
arp_hdr->ar_hrd = htons(arp_hrd_ethernet);
arp_hdr->ar_pro = htons(ethertype_ip);
arp_hdr->ar_hln = ETHER_ADDR_LEN;
arp_hdr->ar_pln = 4;
arp_hdr->ar_op = htons(arp_op_request);
memcpy(arp_hdr->ar_sha, rt_if->addr, ETHER_ADDR_LEN);
arp_hdr->ar_sip = rt_if->ip;
memcpy(arp_hdr->ar_tha, brdcst_addr, ETHER_ADDR_LEN);
arp_hdr->ar_tip = dst_ip;
/* Send the packet. */
sr_send_packet(sr, packet, len, interface);
}
/*-----------------------------------------------------------------------------
* Method: void checkCachedPackets(struct sr_instance* sr, int cachedArp)
*
* searches our packet cache for a matching ip in arpCache[cachedArp]. if we
* find a match, we forward the packet. if we do not find a match we need an
* arp cache entry for it. make sure we have been waiting at least 3 seconds
* before we send the src icmp unreachable packets. this does not drop the
* packet, it just looks every 3rd second to see if we have a response. every
* time we look, we try to increment the arp counter
*---------------------------------------------------------------------------*/
void checkCachedPackets(struct sr_instance* sr, int cachedArp)
{
int i, arpMatch;
for (i = 0; i < PACKET_CACHE_SIZE; i++) {
if (packetCache[i].len > 0) {
// if we have a packet waiting
if (packetCache[i].arps <= 5) {
// and we have not sent 5 arps for this packet yet
if ((arpMatch = arpSearchCache(packetCache[i].tip)) > -1) {
// and we have an arp match for our packet's next hop
forwardPacket(sr, (uint8_t*)&packetCache[i].packet, packetCache[i].len,
// send it along
packetCache[i].nexthop->interface, arpReturnEntryMac(arpMatch));
packetCache[i].len = 0;
} else {
/* wait three seconds between each arp request */
if ((int)(difftime(time(NULL), packetCache[i].timeCached))%3 < 1) {
arpSendRequest(sr, sr_get_interface(sr, packetCache[i].nexthop->interface),
packetCache[i].nexthop->gw.s_addr);
packetCache[i].arps++;
}
}
} else {
/* then */
icmpSendUnreachable(sr, (uint8_t*)&packetCache[i].packet, packetCache[i].len,
packetCache[i].nexthop->interface, ICMP_HOST_UNREACHABLE);
packetCache[i].len = 0;
}
}
}
}
/* Insert a new mapping into the nat's mapping table.
Actually returns a copy to the new mapping, for thread safety.
*/
struct sr_nat_mapping *sr_nat_insert_mapping(struct sr_nat *nat,
uint32_t ip_int, uint16_t aux_int, sr_nat_mapping_type type ) {
pthread_mutex_lock(&(nat->lock));
/* handle insert here, create a mapping, and then return a copy of it */
struct sr_nat_mapping *mapping = malloc(sizeof(struct sr_nat_mapping));
mapping->ip_int = ip_int;
mapping->aux_int = aux_int;
mapping->type = type;
mapping->last_updated = time(NULL);
mapping->conns = NULL;
/* find free port to assign mapping to 1024-2047 */
uint16_t nxt_prt = 0;
for(nxt_prt; nxt_prt < NUM_PORTS; nxt_prt++) {
if (nat->ports_used[nxt_prt] == 0) {
break;
}
}
mapping->aux_ext = 1024+nxt_prt;
nat->ports_used[nxt_prt] == 1;
/* get ext_ip */
struct sr_if *ext_iface = sr_get_interface(nat->sr, nat->out_if_name);
mapping->ip_ext = ext_iface->ip;
mapping->next = nat->mappings; /* add to front of table */
pthread_mutex_unlock(&(nat->lock));
struct sr_nat_mapping *copy = malloc(sizeof(struct sr_nat_mapping));
memcpy(copy, mapping, sizeof(struct sr_nat_mapping));
return copy;
}
int send_packet(struct sr_instance* sr, char* iface, uint8_t* dstMAC, uint8_t* payload, unsigned int len, uint16_t type) {
assert(sr);
assert(payload);
assert(iface);
uint8_t* packet = (uint8_t*)malloc_or_die(len + 14);
struct sr_ethernet_hdr* tmpHdr = (struct sr_ethernet_hdr*) malloc_or_die(14* sizeof(uint8_t));
struct sr_vns_if* interface = sr_get_interface(sr, iface);
mac_copy(dstMAC, tmpHdr->ether_dhost);
mac_copy(interface->addr, tmpHdr->ether_shost);
tmpHdr->ether_type = htons(type);
memcpy(packet, tmpHdr, 14);
packet = packet + 14;
memcpy(packet, payload, len);
packet = packet - 14;
if((sr_integ_low_level_output(sr, packet, (unsigned int)(len + 14), iface)) == 0) {
printf("********** %s successfully sent a packet reply\n", __func__);
return 1;
}
else {
printf("\n @@@@@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ %s sending packet failed?\n", __func__);
return 0;
}
return -1;
}
/* Sends an ARP looking for target IP */
void sr_send_arp(struct sr_instance *sr, enum sr_arp_opcode code, char *iface, unsigned char *target_eth_addr, uint32_t target_ip){
sr_arp_hdr_t *arp_hdr = malloc(sizeof(sr_arp_hdr_t));
if(arp_hdr){
arp_hdr->ar_hrd = htons(arp_hrd_ethernet);
arp_hdr->ar_pro = htons(ethertype_ip);
arp_hdr->ar_hln = ETHER_ADDR_LEN;
arp_hdr->ar_pln = 4;
arp_hdr->ar_op = htons(code);
struct sr_if *node = sr_get_interface(sr, iface);
memcpy(arp_hdr->ar_sha, node->addr, ETHER_ADDR_LEN);
arp_hdr->ar_sip = node->ip;
memcpy(arp_hdr->ar_tha, target_eth_addr, ETHER_ADDR_LEN);
arp_hdr->ar_tip = target_ip;
sr_send_eth(sr, (uint8_t *)arp_hdr, sizeof(sr_arp_hdr_t), (uint8_t *)target_eth_addr, iface, ethertype_arp);
free(arp_hdr);
}
}
void sr_handlepacket(struct sr_instance* sr,
uint8_t * packet/* lent */,
unsigned int len,
char* interface/* lent */)
{
/* REQUIRES */
assert(sr);
assert(packet);
assert(interface);
printf("*** -> Received packet of length %d \n",len);
/* Error handling */
if (len < sizeof(sr_ethernet_hdr_t))
{
printf("Invalid packet, insufficient length.\n");
return;
}
struct sr_if* iface = sr_get_interface(sr, interface);
if (iface == 0)
{
printf("Invalid interface, interface not found.\n");
}
/* Handle ARP packet */
if (ethertype(packet) == ethertype_arp)
{
sr_handle_arp_packet(sr, packet, len, interface, iface);
}
/* Handle IP packet */
else if (ethertype(packet) == ethertype_ip)
{
sr_handle_ip_packet(sr, packet, len, interface, iface);
}
}/* end sr_ForwardPacket */
void sr_handlepacket(struct sr_instance* sr,
uint8_t * packet/* lent */,
unsigned int len,
char* interface/* lent */)
{
/* REQUIRES */
assert(sr);
assert(packet);
assert(interface);
printf("*** -> Received packet of length %d \n",len);
/* check length */
if (len < sizeof(sr_ethernet_hdr_t)) {
fprintf(stderr, "Failed to process ETHERNET header, insufficient length\n");
return;
}
sr_ethernet_hdr_t *eth_hdr = (sr_ethernet_hdr_t *)packet;
uint16_t ether_type = ntohs(eth_hdr->ether_type);
struct sr_if *iface = sr_get_interface(sr, interface);
if (ether_type == ethertype_ip) {
sr_handle_ip(sr, packet, len, iface);
} else if (ether_type == ethertype_arp) {
sr_handle_arp(sr, packet, len, iface);
}
}
void sr_forward_ip(struct sr_instance *sr, uint8_t *packet, unsigned int len)
{
assert(sr);
assert(packet);
sr_ip_hdr_t *ip_hdr = (sr_ip_hdr_t *)(packet + sizeof(sr_ethernet_hdr_t));
ip_hdr->ip_ttl--;
if (ip_hdr->ip_ttl == 0) {
sr_send_icmp(sr, packet, len, 11, 0);
return;
}
ip_hdr->ip_sum = 0;
ip_hdr->ip_sum = cksum(ip_hdr, ip_hdr->ip_hl * 4);
struct sr_rt *rt = sr_longest_prefix_match_lookup(sr, ip_hdr->ip_dst);
if (!rt) {
sr_send_icmp(sr, packet, len, 3, 0);
return;
}
struct sr_if *oiface = sr_get_interface(sr, rt->interface);
sr_lookup_and_send(sr, packet, len, oiface, rt->gw.s_addr);
}
void ipForwarding(struct sr_instance *sr, uint8_t *packet, unsigned int len){
// Construct IP Header
sr_ip_hdr_t *ipHeader = (sr_ip_hdr_t *)(packet + ethernetHeaderSize);
/* Forwading Logistics */
// Decrement TTL
ipHeader->ip_ttl = ipHeader->ip_ttl - 1;
// Check if TTL Expried
if (ipHeader->ip_ttl == 0) {
sendICMP(sr, packet, len, TIME_EXCEEDED, TTL_CODE);
return;
}
// New Checksum
ipHeader->ip_sum = 0; // reset to 0 first
ipHeader->ip_sum = cksum(ipHeader, ipHeader->ip_hl * 4);
/// Look for the LPM
struct sr_rt *matchingEntry = findLPM(sr, ipHeader->ip_dst);
// No LPM => Send ICMP
if (matchingEntry == NULL) {
printf("No LPM Match found... sending ICMP.\n");
sendICMP(sr, packet, len, DESTINATION_UNREACHABLE, NET_UNREACHABLE_CODE);
return;
}
// Get the outgoing interface to send through
struct sr_if *sendingInterface = sr_get_interface(sr, matchingEntry->interface);
sendToInterface(sr, packet, len, sendingInterface, matchingEntry->gw.s_addr);
}
void ip_handlepacket(struct sr_instance *sr,
uint8_t *packet,
unsigned int len,
char *interface) {
printf("** Recieved IP packet\n");
struct sr_ip_hdr *ip_hdr = ip_header(packet);
struct sr_if *r_interface = sr_get_interface(sr, interface);
if (!ip_validpacket(packet, len))
return;
/* Check whether NAT is enabled */
if (!natEnabled(sr)){
printf("** NO NAT\n");
/* Check interface IP to determine whether this IP packet is for me */
if (sr_packet_is_for_me(sr, ip_hdr->ip_dst)) {
ip_handlepacketforme(sr, ip_hdr, interface);
} else {
/* Packet is not for me，forward it */
ip_forwardpacket(sr, ip_hdr, len, interface);
}
} else {
printf("** NAT ENABLED\n");
sr_nat_handle_ip_packet(sr, ip_hdr, ntohs(ip_hdr->ip_len), r_interface);
}
}
void arp_handle(struct sr_instance* sr, uint8_t * packet, unsigned int length, char* interface) {
if(!arp_valid(packet, length)) {
fprintf(stderr, "ARP packet does not match the recognized format.\n");
return;
}
struct sr_if *sr_interface = sr_get_interface(sr, interface);
if(sr_interface == 0) {
fprintf(stderr, "Failed to retrieve interface %s.\n", interface);
return;
}
struct sr_arphdr *arp_hdr = (struct sr_arphdr *)(packet + sizeof(struct sr_ethernet_hdr));
if(ntohs(arp_hdr->ar_op) == ARP_REQUEST) {
if(arp_hdr->ar_tip == sr_interface->ip)
arp_respond(sr, packet, sr_interface);
else printf("Received ARP packet destined for %d\n", arp_hdr->ar_tip);
}
else if(ntohs(arp_hdr->ar_op) == ARP_REPLY) {
struct sr_arp_record *record = cache_add_record(sr, packet);
if(record == NULL) {
fprintf(stderr, "Received ARP response that does not match any outstanding ARP requests.\n");
return;
}
cache_send_outstanding(sr, record);
}
else {
fprintf(stderr, "ARP packet opcode must be of type request or reply.\n");
}
}
void sr_handleARPpacket(struct sr_instance *sr, uint8_t* packet, unsigned int len, struct sr_if * iface) {
assert(packet);
sr_ethernet_hdr_t* ethHeader = (sr_ethernet_hdr_t*) packet;
sr_arp_hdr_t * arpHeader = (sr_arp_hdr_t *) (packet+14);
enum sr_arp_opcode request = arp_op_request;
enum sr_arp_opcode reply = arp_op_reply;
struct sr_if *interface = sr_get_interface_from_ip(sr, htonl(arpHeader->ar_tip));
/* handle an arp request.*/
if (ntohs(arpHeader->ar_op) == request) {
/* found an ip->mac mapping. send a reply to the requester's MAC addr */
if (interface){
arpHeader->ar_op = ntohs(reply);
uint32_t temp = arpHeader->ar_sip;
arpHeader->ar_sip = arpHeader->ar_tip;
arpHeader->ar_tip = temp;
memcpy(arpHeader->ar_tha, arpHeader->ar_sha,6);
memcpy(arpHeader->ar_sha, iface->addr,6);
/*swapping outgoing and incoming addr*/
set_addr(ethHeader, iface->addr, ethHeader->ether_shost);
sr_send_packet(sr,(uint8_t*)ethHeader,len,iface->name);
}
}
/* handle an arp reply */
else {
struct sr_packet *req_packet = NULL;
struct sr_arpreq *req = NULL;
pthread_mutex_lock(&(sr->cache.lock));
for (req = sr->cache.requests; req != NULL; req = req->next){
if(req->ip == arpHeader->ar_sip){
/* find the interface the packets should be sent out of */
struct sr_rt * rt = (struct sr_rt *)sr_find_routing_entry_int(sr, req->ip);
if (rt) {
iface = sr_get_interface(sr, rt->interface);
/* send all packets waiting on the request that was replied to */
for (req_packet = req->packets; req_packet != NULL; req_packet = req_packet->next) {
sr_ethernet_hdr_t * outEther = (sr_ethernet_hdr_t *)req_packet->buf;
memcpy(outEther->ether_shost, iface->addr,6);
memcpy(outEther->ether_dhost, ethHeader->ether_shost,6);
sr_ip_hdr_t * outIP = (sr_ip_hdr_t *)(req_packet->buf+14);
outIP->ip_ttl = outIP->ip_ttl-1;
outIP->ip_sum = 0;
outIP->ip_sum = cksum((uint8_t *)outIP,20);
sr_send_packet(sr,req_packet->buf,req_packet->len,iface->name);
}
sr_arpreq_destroy(&(sr->cache), req);
}
break;
}
}
pthread_mutex_unlock(&(sr->cache.lock));
sr_arpcache_insert(&(sr->cache),arpHeader->ar_sha,arpHeader->ar_sip);
}
}
void sr_handle_arpreq(struct sr_instance *sr, struct sr_arpreq *req) {
time_t curtime = time(NULL);
if (difftime(curtime, req->sent) < 1.0) return;
if (req->times_sent <= 4) {
/* Find out which interface it's on */
char *interface = req->packets->iface;
struct sr_if* iface = sr_get_interface(sr, interface);
/* Allocate a new packet */
size_t out_len = ARP_REPLY_SIZE;
uint8_t *packet_out = malloc(out_len);
/* ====== Headers ====== */
/* Allow easy access to the headers */
sr_ethernet_hdr_t *eth_header_out = (sr_ethernet_hdr_t*) packet_out;
sr_arp_hdr_t *arp_header_out =
(sr_arp_hdr_t*) (packet_out + ARP_HEAD_OFF);
/* Create the ethernet header */
char bcast_addr[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
memcpy(eth_header_out->ether_dhost, bcast_addr,
ETHER_ADDR_LEN);
memcpy(eth_header_out->ether_shost, iface->addr,
ETHER_ADDR_LEN);
eth_header_out->ether_type = htons(ethertype_arp);
/* ====== Body ====== */
/* Create the ARP packet */
arp_header_out->ar_hrd = htons(0x1);
arp_header_out->ar_pro = htons(ethertype_ip);
arp_header_out->ar_hln = ETHER_ADDR_LEN;
arp_header_out->ar_pln = IP_ADDR_LEN;
arp_header_out->ar_op = htons(arp_op_request);
memcpy(arp_header_out->ar_sha, iface->addr, ETHER_ADDR_LEN);
arp_header_out->ar_sip = iface->ip;
char zeroes[] = {0,0,0,0,0,0};
memcpy(arp_header_out->ar_tha,
zeroes, ETHER_ADDR_LEN);
arp_header_out->ar_tip = req->ip;
/* Send the packet */
sr_send_packet(sr, packet_out, out_len, interface);
free(packet_out);
return;
} else {
struct sr_packet *packet = req->packets;
while (packet) {
struct sr_packet *next = packet->next;
send_icmp_error(sr, packet->buf, packet->len, packet->iface, 3, 1);
packet = next;
}
sr_arpreq_destroy(&(sr->cache), req);
}
return;
}
sr_if_t *get_external_iface(struct sr_instance *sr)
{
sr_if_t *int_iface = sr_get_interface(sr,sr->nat.int_iface_name);
for (sr_if_t *iface = sr->if_list; iface != NULL; iface = iface->next) {
if (iface != int_iface)
return iface;
}
return NULL;
}
/*******************************************************************
* Finds interface the ARP Request was received from and constructs ARP Reply to send back out of
* the received interface.
*******************************************************************/
void got_Request(struct packet_state * ps, struct sr_arphdr * arp_hdr, const struct sr_ethernet_hdr* eth)
{
assert(ps);
assert(arp_hdr);
assert(eth);
struct sr_if *iface = sr_get_interface(ps->sr, ps->interface);
assert(iface);
construct_reply(ps, arp_hdr, iface->addr, eth);
}
/*---------------------------------------------------------------------
* Method: destined_to_nat_external
*
* Scope: Local
*
* returns true if the destination IP address of a packet's is that
* of the NAT itself (its external facing IP address)
*
* parameters:
* sr - a reference to the router structure
* ip_dst - the ip_dst of the received packet.
*
*---------------------------------------------------------------------*/
bool destined_to_nat_external(struct sr_instance* sr, uint32_t ip_dst) {
sr_if_t *int_iface = sr_get_interface(sr,sr->nat.int_iface_name);
for (sr_if_t *iface = sr->if_list; iface != NULL; iface = iface->next) {
if (iface == int_iface)
continue;
if (ip_dst == iface->ip)
return true;
}
return false;
}
bool match_interface_etheraddr(struct sr_instance *sr,uint8_t *ethaddr,const char * interface)
{
sr_if_t *ifptr = sr_get_interface(sr,interface);
//check if interface exists
if (ifptr == 0)
return false;
return ether_addr_equals(ifptr->addr,ethaddr);
}
void handle_arpreq(struct sr_instance *sr, struct sr_arpreq *req) {
time_t now = time(NULL);
if(difftime(now, req->sent) > 1.0) {
/* request timeout */
if(req->times_sent > 5) {
struct sr_packet *packets = req->packets;
/* iterate through all packets on queue */
while(packets) {
uint8_t *reply_packet = 0;
sr_ip_hdr_t *ip_hdr = (sr_ip_hdr_t *)(packets->buf+sizeof(sr_ethernet_hdr_t));
reply_packet = sr_generate_icmp((sr_ethernet_hdr_t *)packets->buf, ip_hdr, sr_get_interface(sr, packets->iface), 3, 1); /* create ICMP type 3, code 1 (host unreachable) */
/* if ICMP packet fails to generate */
if(reply_packet == 0) {
fprintf(stderr, "Error: failed to generate ICMP packet\n");
}
/* send ICMP packet to ip of packet in queue */
if(sr_send_packet(sr, reply_packet, sizeof(sr_ethernet_hdr_t) + sizeof(sr_ip_hdr_t) + sizeof(sr_icmp_t3_hdr_t), (const char*)(packets->iface)) == -1) {
fprintf(stderr, "Error: sending packet failed (handle_arpreq)");
}
packets = packets->next;
free(reply_packet);
}
sr_arpreq_destroy(&(sr->cache), req);
} else {
/* generate ARP packet */
struct sr_if *iface = 0;
/* if interface is not found */
if((iface = sr_get_interface(sr, req->packets->iface)) == 0) {
fprintf(stderr, "Error: interface does not exist (handle_arpreq)");
return;
}
uint8_t *arp_pkt = sr_new_arpreq_packet(NULL, iface->addr, req->ip, iface->ip); /* create ARP request packet to re-send */
/* send ARP request packet */
if (sr_send_packet(sr, arp_pkt, sizeof(sr_ethernet_hdr_t) + sizeof(sr_arp_hdr_t), (const char*)(iface->name))==-1) {
fprintf(stderr, "Error: sending packet failed.");
}
/* update arpreq fields */
req->times_sent++;
req->sent = now;
free(arp_pkt);
}
}
}
/* Sends ICMP messages to all the packets waiting on this request */
void sr_send_icmp_to_waiting(struct sr_instance *sr, struct sr_arpreq *req){
struct sr_packet *packet = req->packets;
while(packet){
struct sr_if* node = sr_get_interface(sr, packet->iface);
struct sr_ethernet_hdr *eth = (sr_ethernet_hdr_t *)(packet->buf);
struct sr_ip_hdr *ip_hdr = (sr_ip_hdr_t *)(eth + 1);
sr_send_icmp3(sr, icmp_unreach, icmp_host_unreach, node->ip, ip_hdr->ip_src, (uint8_t*)ip_hdr, (4*(ip_hdr->ip_hl)) + MORSEL);
packet = packet->next;
}
}
int sr_handle_arpreq(struct sr_instance *sr, struct sr_arpreq *request){
time_t now = get_now(&now);
struct sr_packet * packetptr = request->packets;
int i;
if(difftime(now, request->sent) > 1.0){
if(request->times_sent >= 5){
while(packetptr != NULL){
icmp_send_reply(sr, (uint8_t *)packetptr, packetptr->len, packetptr->iface, 3, 1); /* send unreachable */
packetptr = packetptr->next;
}
sr_arpreq_destroy(&(sr->cache), request);
return -1;
}else{
struct sr_rt* entry;
struct sr_rt* routing = sr->routing_table;
for(entry = routing; entry != NULL; entry = routing->next){
struct sr_if * interface2 = sr_get_interface(sr, entry->interface);
/*create arp packet*/
enum sr_arp_opcode opcode = arp_op_request;
struct sr_packet *raw = malloc(sizeof(struct sr_arp_hdr) + ETHER_HDR_LEN);
/* may need to memset here*/
struct sr_ethernet_hdr *eth = (struct sr_ethernet_hdr *)raw;
struct sr_arp_hdr *req = (struct sr_arp_hdr *)(raw + ETHER_HDR_LEN);
req->ar_hrd = 0;
req->ar_pro = 0;
req->ar_hln = 0;
req->ar_pln = 0;
req->ar_op = opcode;
req->ar_sip = sr->sr_addr.sin_addr.s_addr;
req->ar_tip = request->ip;
for (i = 0; i < ETHER_ADDR_LEN; i++){
req->ar_tha[i] = 0xff;
req->ar_sha[i] = interface2->addr[i];
eth->ether_dhost[i] = 0xff;
eth->ether_shost[i] = interface2->addr[i];
}
/*send packet to the interface on routing_table*/
sr_send_packet(sr, (uint8_t *)raw, sizeof(struct sr_arp_hdr) + ETHER_HDR_LEN, request->packets->iface);
free(raw);
}
request->sent = now;
request->times_sent++;
}
}
return 0;
}
/*
The handle_arpreq() function is a function you should write, and it should
handle sending ARP requests if necessary:
function handle_arpreq(request):
if difftime(now, request->sent) > 1.0
if request->times_sent >= 5:
send icmp host unreachable to source addr of all pkts waiting
on this request
arpreq_destroy(request)
else:
send arp request
request->sent = now
request->times_sent++
*/
void handle_arpreq(struct sr_instance *sr, struct sr_arpreq *request){
//assert(sr);
//assert(request);
// If time since last sent is more than 1 second
if (difftime(time(NULL), request->sent) >= 1.0) {
/* If an ARP request has been sent 5 times with no response,
a destination host unreachable should go back to all the sender of packets that were waiting on
a reply to this ARP request. */
if (request->times_sent >= 5) {
// Iniitalize variables for the loop
struct sr_packet *packetPointer = NULL;
sr_ethernet_hdr_t *ethernetHeader = NULL;
struct sr_if *interface = NULL;
// get a pointer to a array of all packets waiting
packetPointer = request->packets;
// For every xender of packets waiting, send host unreachable
while (packetPointer != NULL) {
ethernetHeader = (sr_ethernet_hdr_t *)(packetPointer->buf);
interface = getAddressInterface(sr, ethernetHeader->ether_dhost);
/* do not send an ICMP message for an ICMP message */
// If we got an interface of a waiting sender, send the ICMP host unreachable
if (interface) {
sendICMP(sr, packetPointer->buf, packetPointer->len, DESTINATION_UNREACHABLE, HOST_UNREACHABLE_CODE);
}
// Go to the next exisiting packet
packetPointer = packetPointer->next;
}
sr_arpreq_destroy(&(sr->cache), request);
}
// Otherwise, just send arp request with its sent time = now and increment times sent
else {
struct sr_if *sendingInterface = sr_get_interface(sr, request->packets->iface);
arpRequest(sr, sendingInterface, request->ip);
// Set sent time to NOW
request->sent = time(NULL); // time(NULL) = NOW
// Increment # of times sent
request->times_sent = request->times_sent + 1;
}
}
}
/*
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);
}
/* prepare arp into ethernet frame and send it */
int boardcast_arpreq(struct sr_instance *sr, struct sr_arpreq *arp_req){
struct sr_if *o_interface;
/*first package the arp package header first...*/
o_interface = sr_get_interface(sr, arp_req->packets->iface);
struct sr_arp_hdr arp_hdr;
uint8_t *arp_package;
uint8_t *e_pack;
arp_hdr.ar_hrd = sr_arp_hrd_fmt hfmt = arp_hrd_ethernet; /* format of hardware address */
arp_hdr.ar_pro = 0X800; /*from http:/*www.networksorcery.com/enp/protocol/arp.htm#Protocol%20address%20length*/
arp_hdr.ar_hln = ETHER_ADDR_LEN = 8; /*from http:/*www.networksorcery.com/enp/protocol/arp.htm#Protocol%20address%20length*/
arp_hdr.ar_pln = 8; /*from http:/*www.networksorcery.com/enp/protocol/arp.htm#Protocol%20address%20length*/
sr_arp_opcode code = arp_op_request;
arp_hdr.ar_op = code; /* ARP opcode (command) */
memcpy(arp_hdr.ar_sha, o_interface->addr, ETHER_ADDR_LEN); /* sender hardware address */
arp_hdr.ar_sip = o_interface.ip; /* sender IP address */
arp_hdr.ar_tip = arp_req.ip; /* target IP address */
/*copy everything into the arp_header*/
arp_package = malloc(sizeof(sr_arp_hdr_t));
print_hdr_arp(arp_package);
memcpy(arp_package, &apr_hdr, sizeof(sr_arp_hdr_t));
/*then package the ethernet header along with the arp header...*/
e_pack = eth_hdr_package(uint8_t ether_dhost, sr, o_interface->addr, arp_package, sizeof(struct sr_arp_hdr));
print_hdr_eth(e_pack);
/*send it out*/
sr_send_packet(sr, e_pack, sizeof(struct sr_arp_hdr) + sizeof(struct sr_ethernet_hdr), o_interface);
/* build the ethernet frame to be broadcast */
int eth_hdr_package(uint8_t ether_dhost, uint8_t ether_shost, uint16_t ether_type, uint8_t *content, int len){
uint8_t *output;
int total_length;
struct sr_ethernet_hdr e_hdr;
/*first step is to create a ethernet header...*/
memcpy(e_hdr.ether_dhost,ether_dhost,ETHER_ADDR_LEN); /* destination ethernet address */
memcpy(e_hdr.ether_shost,ether_shost,ETHER_ADDR_LEN); /* source ethernet address */
e_hdr.ether_type = ether_type;
/*calculate the length of the entire thing...*/
total_length = sizeof(sr_ethernet_hdr_t) + len;
/*put everything together*/
output = malloc(total_length);
/*put the ethernet header in the front*/
memcpy(output, &e_hdr, sizeof(sr_ethernet_hdr_t));
memcpy(output + sizeof(sr_ethernet_hdr_t), content,len);
return output;
}
void handle_arpreq(struct sr_instance* sr, struct sr_arpreq *cache_req_ptr) {
char *iface_name = cache_req_ptr->packets->iface;
struct sr_if *interface = sr_get_interface(sr, iface_name);
/*Only broadcast if this hasn't been sent out before:
*Otherwise, our packet has been added to the end of the
* request's linkedlist in the cache: do nothing*/
if (difftime(time(0), cache_req_ptr->sent) > 1.0) {
if (cache_req_ptr->times_sent >= 5) {
struct sr_packet *req_pkt_ptr = cache_req_ptr->packets;
for (; req_pkt_ptr; req_pkt_ptr = req_pkt_ptr->next) {
send_icmp(sr, req_pkt_ptr->buf, req_pkt_ptr->len, interface, dest_host_unreach_type, dest_host_unreach_code);
}
sr_arpreq_destroy(&(sr->cache), cache_req_ptr);
}
else {
/*Create space for the request*/
uint8_t* eth_pkt_buf = (uint8_t *) malloc(sizeof(sr_ethernet_hdr_t) + sizeof(sr_arp_hdr_t));
uint8_t* arp_pkt_buf;
/*Pointers to where different header structs start in the packet*/
sr_ethernet_hdr_t* req_eth_header = (sr_ethernet_hdr_t*) eth_pkt_buf; /* Allocate mem for reply packet buffer */
/* Copy addresses and type into the ethernet header */
uint8_t broadcast_addr[ETHER_ADDR_LEN] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
memcpy(req_eth_header->ether_dhost, broadcast_addr, ETHER_ADDR_LEN);
memcpy(req_eth_header->ether_shost, interface->addr, ETHER_ADDR_LEN);
req_eth_header->ether_type = ethertype_arp;
/* Convert to network byte ordering */
hton_eth_hdr(&req_eth_header);
/* Get the Arp Buffer and Build the Arp packet*/
arp_pkt_buf = eth_pkt_buf + sizeof(sr_ethernet_hdr_t);
sr_create_arp_req_packet(arp_pkt_buf, cache_req_ptr, interface);
/* Send the ARP request packet */
sr_send_packet(sr, eth_pkt_buf, sizeof(sr_ethernet_hdr_t) + sizeof(sr_arp_hdr_t),
interface->name);
cache_req_ptr->sent = time(0);
cache_req_ptr->times_sent++;
free(eth_pkt_buf);
}
}
}
void sr_icmp_ttl_exceeded(struct sr_instance *sr, uint8_t * packet,
unsigned int len, char* interface,
struct sr_ethernet_hdr *e_hdr, struct ip *ip_hdr)
{
struct sr_if *iface = sr_get_interface(sr, interface);
/* Send ICMP time exceeded message. This is
need for traceroute to work. */
uint8_t *new_pkt = (uint8_t *) calloc(1, 70);
struct sr_ethernet_hdr *new_e_hdr = (struct sr_ethernet_hdr *) new_pkt;
struct ip *new_ip_hdr = (struct ip *) (new_pkt + 14);
struct sr_icmphdr *new_icmp_hdr = (struct sr_icmphdr *) (new_pkt + 34);
/* ethernet header */
memcpy(new_e_hdr->ether_dhost, e_hdr->ether_shost, 6);
memcpy(new_e_hdr->ether_shost, e_hdr->ether_dhost, 6);
new_e_hdr->ether_type = htons(0x0800);
/* IP header */
new_ip_hdr->ip_hl = 5;
new_ip_hdr->ip_v = 4;
new_ip_hdr->ip_tos = 0;
new_ip_hdr->ip_len = htons(56);
new_ip_hdr->ip_id = ip_hdr->ip_id;
new_ip_hdr->ip_off = ip_hdr->ip_off;
new_ip_hdr->ip_ttl = 64;
new_ip_hdr->ip_p = 1;
new_ip_hdr->ip_src.s_addr = iface->ip;
new_ip_hdr->ip_dst = ip_hdr->ip_src;
new_ip_hdr->ip_sum = 0;
new_ip_hdr->ip_sum = checksum(new_ip_hdr, 20);
/* ICMP ttl exceeded: type: 11, code: 0 */
new_icmp_hdr->icmp_type = 11;
new_icmp_hdr->icmp_code = 0;
new_icmp_hdr->id = 0;
new_icmp_hdr->seqno = 0;
memcpy(new_pkt+42, ip_hdr, 28);
new_icmp_hdr->icmp_chksum = 0;
new_icmp_hdr->icmp_chksum = checksum((uint16_t *)new_icmp_hdr, 36);
int success = sr_send_packet(sr, new_pkt, 70, interface);
if (success != 0) {
fprintf(stderr, "%s: Sending packet failed!\n", __func__);
}
}
/*---------------------------------------------------------------------
* Method: process_arp(struct sr_instance* sr,
* uint8_t * packet,
* unsigned int len,
* char* interface)
* Scope: Internal
*
* This function processes an arp packe that was received. It handles
* two cases, one where it is a request and one where it is a response.
*
*---------------------------------------------------------------------*/
void process_arp(struct sr_instance* sr,
uint8_t * packet,
unsigned int len,
char* interface)
{
struct sr_arpentry *arp_entry;
struct sr_arpreq *arp_req;
struct sr_arp_hdr *arp_hdr;
struct sr_if* rec_if;
/* Validate the arp packet */
if (!valid_arp(packet, len))
return;
/* Is the arp addressed to me? NOTE: I do not follow the RFC recommendation to
* update existing cache entries with the received arp packet's ip-mac mapping
* before checking whether the packet was addressed me. This is because we do
* not have a good way to strictly 'update' cache entries without inserting a new
* one and I would like to avoid duplicate valid cache entries for the same ip. */
rec_if = sr_get_interface(sr, interface);
arp_hdr = arp_header(packet);
if (rec_if->ip != arp_hdr->ar_tip)
return;
/* Add the sender's protocol address to my table. */
arp_entry = sr_arpcache_lookup(&sr->cache, arp_hdr->ar_sip);
/* Arp entry already exists. NOTE: arp_entry is a copy in this case so free it.*/
if (arp_entry != 0) {
free(arp_entry);
/* Arp entry doesn't exist so add it. */
} else {
arp_req = sr_arpcache_insert(&sr->cache, arp_hdr->ar_sha, arp_hdr->ar_sip);
/* There are packets waiting on this arp request. Send them. */
if (arp_req != 0) {
sr_arpreq_send_packets(sr, arp_req);
}
}
/* Handle a request. */
if (arp_opcode(arp_hdr) == arp_op_request) {
process_arp_request(sr, arp_hdr, rec_if);
}
}
/*
* Send an ICMP Error.
*/
void send_icmp_error(uint8_t type, uint8_t code, struct sr_instance *sr,
char *interface, unsigned int len, uint8_t *pkt) {
int new_len = sizeof(sr_ethernet_hdr_t) + sizeof(sr_ip_hdr_t) + sizeof(sr_icmp_t3_hdr_t);
uint8_t *packet = (uint8_t *) malloc(new_len);
struct sr_if *rt_if = (struct sr_if *)malloc(sizeof(struct sr_if));
rt_if = (struct sr_if *)sr_get_interface(sr, interface);
/* Prepare ethernet header. */
sr_ethernet_hdr_t *ether_hdr = (sr_ethernet_hdr_t *) pkt;
sr_ethernet_hdr_t *ether_newhdr = (sr_ethernet_hdr_t *) packet;
ether_newhdr->ether_type = htons(ethertype_ip);
memcpy(ether_newhdr->ether_shost, rt_if->addr, ETHER_ADDR_LEN);
memcpy(ether_newhdr->ether_dhost, ether_hdr->ether_shost, ETHER_ADDR_LEN);
/* Prepare IP header. */
sr_ip_hdr_t *ip_hdr = (sr_ip_hdr_t *)(pkt + sizeof(sr_ethernet_hdr_t));
sr_ip_hdr_t *ip_newhdr = (sr_ip_hdr_t *)(packet + sizeof(sr_ethernet_hdr_t));
memcpy(ip_newhdr, ip_hdr, sizeof(sr_ip_hdr_t));
ip_newhdr->ip_src = rt_if->ip;
ip_newhdr->ip_dst = ip_hdr->ip_src;
ip_newhdr->ip_len = htons(56);
ip_newhdr->ip_id = 0;
ip_newhdr->ip_hl = 5;
ip_newhdr->ip_off = 0;
ip_newhdr->ip_ttl = 64;
ip_newhdr->ip_p = ip_protocol_icmp;
ip_newhdr->ip_sum = 0;
ip_newhdr->ip_sum = cksum(packet + sizeof(sr_ethernet_hdr_t), sizeof(sr_ip_hdr_t));
/* Prepare the ICMP t3 header. */
sr_icmp_t3_hdr_t *icmp_t3_hdr = (sr_icmp_t3_hdr_t *)(packet +
sizeof(sr_ethernet_hdr_t) +
sizeof(sr_ip_hdr_t));
icmp_t3_hdr->icmp_type = type;
icmp_t3_hdr->icmp_code = code;
icmp_t3_hdr->icmp_sum = 0;
memcpy(icmp_t3_hdr->data, ip_hdr, 20);
memcpy(icmp_t3_hdr->data + 20, pkt + sizeof(sr_ethernet_hdr_t) + sizeof(sr_ip_hdr_t), 8);
icmp_t3_hdr->icmp_sum = cksum(packet + sizeof(sr_ethernet_hdr_t) + sizeof(sr_ip_hdr_t),
sizeof(sr_icmp_t3_hdr_t));
/* Send the ICMP error packet. */
sr_send_packet(sr, packet, new_len, interface);
}