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++;
}
}
}
static enum ofp_return_code ofp_ip_output_add_eth(odp_packet_t pkt,
struct ip_out *odata)
{
uint8_t l2_size = 0;
void *l2_addr;
if (!odata->gw) /* link local */
odata->gw = odata->ip->ip_dst.s_addr;
if (ETH_WITHOUT_VLAN(odata->vlan, odata->out_port))
l2_size = sizeof(struct ofp_ether_header);
else
l2_size = sizeof(struct ofp_ether_vlan_header);
if (odp_packet_l2_offset(pkt) + l2_size == odp_packet_l3_offset(pkt)) {
l2_addr = odp_packet_l2_ptr(pkt, NULL);
} else if (odp_packet_l3_offset(pkt) >= l2_size) {
odp_packet_l2_offset_set(pkt,
odp_packet_l3_offset(pkt) - l2_size);
l2_addr = odp_packet_l2_ptr(pkt, NULL);
} else {
l2_addr = odp_packet_push_head(pkt,
l2_size - odp_packet_l3_offset(pkt));
odp_packet_l2_offset_set(pkt, 0);
odp_packet_l3_offset_set(pkt, l2_size);
odp_packet_l4_offset_set(pkt, l2_size + (odata->ip->ip_hl<<2));
}
if (odp_unlikely(l2_addr == NULL)) {
OFP_DBG("l2_addr == NULL");
return OFP_PKT_DROP;
}
if (ETH_WITHOUT_VLAN(odata->vlan, odata->out_port)) {
struct ofp_ether_header *eth =
(struct ofp_ether_header *)l2_addr;
uint32_t addr = odp_be_to_cpu_32(odata->ip->ip_dst.s_addr);
if (OFP_IN_MULTICAST(addr)) {
eth->ether_dhost[0] = 0x01;
eth->ether_dhost[1] = 0x00;
eth->ether_dhost[2] = 0x5e;
eth->ether_dhost[3] = (addr >> 16) & 0x7f;
eth->ether_dhost[4] = (addr >> 8) & 0xff;
eth->ether_dhost[5] = addr & 0xff;
} else if (odata->dev_out->ip_addr == odata->ip->ip_dst.s_addr) {
odata->is_local_address = 1;
ofp_copy_mac(eth->ether_dhost, &(odata->dev_out->mac[0]));
} else if (ofp_get_mac(odata->dev_out, odata->gw, eth->ether_dhost) < 0) {
send_arp_request(odata->dev_out, odata->gw);
return ofp_arp_save_ipv4_pkt(pkt, odata->nh,
odata->gw, odata->dev_out);
}
ofp_copy_mac(eth->ether_shost, odata->dev_out->mac);
eth->ether_type = odp_cpu_to_be_16(OFP_ETHERTYPE_IP);
} else {
void arp_queue_add(struct sr_instance* sr, uint8_t* packet, unsigned int len, const char* out_iface_name, struct in_addr *next_hop)
{
assert(sr);
assert(packet);
assert(out_iface_name);
assert(next_hop);
router_state *rs = get_router_state(sr);
/* Is there an existing queue entry for this IP? */
arp_queue_entry* aqe = get_from_arp_queue(sr, next_hop);
if (!aqe) {
/* create a new queue entry */
aqe = (arp_queue_entry*)malloc(sizeof(arp_queue_entry));
bzero(aqe, sizeof(arp_queue_entry));
memcpy(aqe->out_iface_name, out_iface_name, IF_LEN);
aqe->next_hop = *next_hop;
/* send a request */
time(&(aqe->last_req_time));
aqe->requests = 1;
send_arp_request(sr, next_hop->s_addr, out_iface_name);
arp_queue_entry_add_packet(aqe, packet, len);
/* create a node, add this entry to the node, and push it into our linked list */
node* n = node_create();
n->data = aqe;
if (rs->arp_queue == NULL) {
rs->arp_queue = n;
} else {
node_push_back(rs->arp_queue, n);
}
} else {
/* entry exists, just add the packet */
arp_queue_entry_add_packet(aqe, packet, len);
}
}
void handle_arpreq(struct sr_instance* sr, struct sr_arpreq* req) {
time_t curtime = time(NULL);
if (difftime(curtime,req->sent) > 1.0) {
if (req->times_sent >= 5) {
struct sr_packet* sr_pckt = req->packets;
while (sr_pckt != NULL) {
send_icmp_destination_host_unreachable(sr, sr_pckt->buf,
sr_pckt->len);
sr_pckt = sr_pckt->next;
}
sr_arpreq_destroy(&sr->cache, req);
} else {
send_arp_request(sr, req);
req->sent = curtime;
req->times_sent = req->times_sent + 1;
}
}
}
int zcip_main(int argc UNUSED_PARAM, char **argv)
{
char *r_opt;
const char *l_opt = "169.254.0.0";
int state;
int nsent;
unsigned opts;
// Ugly trick, but I want these zeroed in one go
struct {
const struct ether_addr null_ethaddr;
struct ifreq ifr;
uint32_t chosen_nip;
int conflicts;
int timeout_ms; // must be signed
int verbose;
} L;
#define null_ethaddr (L.null_ethaddr)
#define ifr (L.ifr )
#define chosen_nip (L.chosen_nip )
#define conflicts (L.conflicts )
#define timeout_ms (L.timeout_ms )
#define verbose (L.verbose )
memset(&L, 0, sizeof(L));
INIT_G();
#define FOREGROUND (opts & 1)
#define QUIT (opts & 2)
// Parse commandline: prog [options] ifname script
// exactly 2 args; -v accumulates and implies -f
opt_complementary = "=2:vv:vf";
opts = getopt32(argv, "fqr:l:v", &r_opt, &l_opt, &verbose);
#if !BB_MMU
// on NOMMU reexec early (or else we will rerun things twice)
if (!FOREGROUND)
bb_daemonize_or_rexec(0 /*was: DAEMON_CHDIR_ROOT*/, argv);
#endif
// Open an ARP socket
// (need to do it before openlog to prevent openlog from taking
// fd 3 (sock_fd==3))
xmove_fd(xsocket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)), sock_fd);
if (!FOREGROUND) {
// do it before all bb_xx_msg calls
openlog(applet_name, 0, LOG_DAEMON);
logmode |= LOGMODE_SYSLOG;
}
bb_logenv_override();
{ // -l n.n.n.n
struct in_addr net;
if (inet_aton(l_opt, &net) == 0
|| (net.s_addr & htonl(IN_CLASSB_NET)) != net.s_addr
) {
bb_error_msg_and_die("invalid network address");
}
G.localnet_ip = ntohl(net.s_addr);
}
if (opts & 4) { // -r n.n.n.n
struct in_addr ip;
if (inet_aton(r_opt, &ip) == 0
|| (ntohl(ip.s_addr) & IN_CLASSB_NET) != G.localnet_ip
) {
bb_error_msg_and_die("invalid link address");
}
chosen_nip = ip.s_addr;
}
argv += optind - 1;
/* Now: argv[0]:junk argv[1]:intf argv[2]:script argv[3]:NULL */
/* We need to make space for script argument: */
argv[0] = argv[1];
argv[1] = argv[2];
/* Now: argv[0]:intf argv[1]:script argv[2]:junk argv[3]:NULL */
#define argv_intf (argv[0])
xsetenv("interface", argv_intf);
// Initialize the interface (modprobe, ifup, etc)
if (run(argv, "init", 0))
return EXIT_FAILURE;
// Initialize G.iface_sockaddr
// G.iface_sockaddr is: { u16 sa_family; u8 sa_data[14]; }
//memset(&G.iface_sockaddr, 0, sizeof(G.iface_sockaddr));
//TODO: are we leaving sa_family == 0 (AF_UNSPEC)?!
safe_strncpy(G.iface_sockaddr.sa_data, argv_intf, sizeof(G.iface_sockaddr.sa_data));
// Bind to the interface's ARP socket
xbind(sock_fd, &G.iface_sockaddr, sizeof(G.iface_sockaddr));
// Get the interface's ethernet address
//memset(&ifr, 0, sizeof(ifr));
strncpy_IFNAMSIZ(ifr.ifr_name, argv_intf);
xioctl(sock_fd, SIOCGIFHWADDR, &ifr);
memcpy(&G.our_ethaddr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
// Start with some stable ip address, either a function of
// the hardware address or else the last address we used.
// we are taking low-order four bytes, as top-order ones
// aren't random enough.
// NOTE: the sequence of addresses we try changes only
// depending on when we detect conflicts.
{
uint32_t t;
move_from_unaligned32(t, ((char *)&G.our_ethaddr + 2));
t += getpid();
srand(t);
}
// FIXME cases to handle:
// - zcip already running!
// - link already has local address... just defend/update
// Daemonize now; don't delay system startup
if (!FOREGROUND) {
#if BB_MMU
bb_daemonize(0 /*was: DAEMON_CHDIR_ROOT*/);
#endif
bb_info_msg("start, interface %s", argv_intf);
}
// Run the dynamic address negotiation protocol,
// restarting after address conflicts:
// - start with some address we want to try
// - short random delay
// - arp probes to see if another host uses it
// 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff arp who-has 169.254.194.171 tell 0.0.0.0
// - arp announcements that we're claiming it
// 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff arp who-has 169.254.194.171 (00:04:e2:64:23:c2) tell 169.254.194.171
// - use it
// - defend it, within limits
// exit if:
// - address is successfully obtained and -q was given:
// run "<script> config", then exit with exitcode 0
// - poll error (when does this happen?)
// - read error (when does this happen?)
// - sendto error (in send_arp_request()) (when does this happen?)
// - revents & POLLERR (link down). run "<script> deconfig" first
if (chosen_nip == 0) {
new_nip_and_PROBE:
chosen_nip = pick_nip();
}
nsent = 0;
state = PROBE;
while (1) {
struct pollfd fds[1];
unsigned deadline_us;
struct arp_packet p;
int ip_conflict;
int n;
fds[0].fd = sock_fd;
fds[0].events = POLLIN;
fds[0].revents = 0;
// Poll, being ready to adjust current timeout
if (!timeout_ms) {
timeout_ms = random_delay_ms(PROBE_WAIT);
// FIXME setsockopt(sock_fd, SO_ATTACH_FILTER, ...) to
// make the kernel filter out all packets except
// ones we'd care about.
}
// Set deadline_us to the point in time when we timeout
deadline_us = MONOTONIC_US() + timeout_ms * 1000;
VDBG("...wait %d %s nsent=%u\n",
timeout_ms, argv_intf, nsent);
n = safe_poll(fds, 1, timeout_ms);
if (n < 0) {
//bb_perror_msg("poll"); - done in safe_poll
return EXIT_FAILURE;
}
if (n == 0) { // timed out?
VDBG("state:%d\n", state);
switch (state) {
case PROBE:
// No conflicting ARP packets were seen:
// we can progress through the states
if (nsent < PROBE_NUM) {
nsent++;
VDBG("probe/%u %s@%s\n",
nsent, argv_intf, nip_to_a(chosen_nip));
timeout_ms = PROBE_MIN * 1000;
timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
send_arp_request(0, &null_ethaddr, chosen_nip);
continue;
}
// Switch to announce state
nsent = 0;
state = ANNOUNCE;
goto send_announce;
case ANNOUNCE:
// No conflicting ARP packets were seen:
// we can progress through the states
if (nsent < ANNOUNCE_NUM) {
send_announce:
nsent++;
VDBG("announce/%u %s@%s\n",
nsent, argv_intf, nip_to_a(chosen_nip));
timeout_ms = ANNOUNCE_INTERVAL * 1000;
send_arp_request(chosen_nip, &G.our_ethaddr, chosen_nip);
continue;
}
// Switch to monitor state
// FIXME update filters
run(argv, "config", chosen_nip);
// NOTE: all other exit paths should deconfig...
if (QUIT)
return EXIT_SUCCESS;
// fall through: switch to MONITOR
default:
// case DEFEND:
// case MONITOR: (shouldn't happen, MONITOR timeout is infinite)
// Defend period ended with no ARP replies - we won
timeout_ms = -1; // never timeout in monitor state
state = MONITOR;
continue;
}
}
// Packet arrived, or link went down.
// We need to adjust the timeout in case we didn't receive
// a conflicting packet.
if (timeout_ms > 0) {
unsigned diff = deadline_us - MONOTONIC_US();
if ((int)(diff) < 0) {
// Current time is greater than the expected timeout time.
diff = 0;
}
VDBG("adjusting timeout\n");
timeout_ms = (diff / 1000) | 1; // never 0
}
if ((fds[0].revents & POLLIN) == 0) {
if (fds[0].revents & POLLERR) {
// FIXME: links routinely go down;
// this shouldn't necessarily exit.
bb_error_msg("iface %s is down", argv_intf);
if (state >= MONITOR) {
// Only if we are in MONITOR or DEFEND
run(argv, "deconfig", chosen_nip);
}
return EXIT_FAILURE;
}
continue;
}
// Read ARP packet
if (safe_read(sock_fd, &p, sizeof(p)) < 0) {
bb_perror_msg_and_die(bb_msg_read_error);
}
if (p.eth.ether_type != htons(ETHERTYPE_ARP))
continue;
if (p.arp.arp_op != htons(ARPOP_REQUEST)
&& p.arp.arp_op != htons(ARPOP_REPLY)
) {
continue;
}
#ifdef DEBUG
{
struct ether_addr *sha = (struct ether_addr *) p.arp.arp_sha;
struct ether_addr *tha = (struct ether_addr *) p.arp.arp_tha;
struct in_addr *spa = (struct in_addr *) p.arp.arp_spa;
struct in_addr *tpa = (struct in_addr *) p.arp.arp_tpa;
VDBG("source=%s %s\n", ether_ntoa(sha), inet_ntoa(*spa));
VDBG("target=%s %s\n", ether_ntoa(tha), inet_ntoa(*tpa));
}
#endif
ip_conflict = 0;
if (memcmp(&p.arp.arp_sha, &G.our_ethaddr, ETH_ALEN) != 0) {
if (memcmp(p.arp.arp_spa, &chosen_nip, 4) == 0) {
// A probe or reply with source_ip == chosen ip
ip_conflict = 1;
}
if (p.arp.arp_op == htons(ARPOP_REQUEST)
&& memcmp(p.arp.arp_spa, &const_int_0, 4) == 0
&& memcmp(p.arp.arp_tpa, &chosen_nip, 4) == 0
) {
// A probe with source_ip == 0.0.0.0, target_ip == chosen ip:
// another host trying to claim this ip!
ip_conflict |= 2;
}
}
VDBG("state:%d ip_conflict:%d\n", state, ip_conflict);
if (!ip_conflict)
continue;
// Either src or target IP conflict exists
if (state <= ANNOUNCE) {
// PROBE or ANNOUNCE
conflicts++;
timeout_ms = PROBE_MIN * 1000
+ CONFLICT_MULTIPLIER * random_delay_ms(conflicts);
goto new_nip_and_PROBE;
}
// MONITOR or DEFEND: only src IP conflict is a problem
if (ip_conflict & 1) {
if (state == MONITOR) {
// Src IP conflict, defend with a single ARP probe
VDBG("monitor conflict - defending\n");
timeout_ms = DEFEND_INTERVAL * 1000;
state = DEFEND;
send_arp_request(chosen_nip, &G.our_ethaddr, chosen_nip);
continue;
}
// state == DEFEND
// Another src IP conflict, start over
VDBG("defend conflict - starting over\n");
run(argv, "deconfig", chosen_nip);
conflicts = 0;
timeout_ms = 0;
goto new_nip_and_PROBE;
}
// Note: if we only have a target IP conflict here (ip_conflict & 2),
// IOW: if we just saw this sort of ARP packet:
// aa:bb:cc:dd:ee:ff > xx:xx:xx:xx:xx:xx arp who-has <chosen_nip> tell 0.0.0.0
// we expect _kernel_ to respond to that, because <chosen_nip>
// is (expected to be) configured on this iface.
} // while (1)
#undef argv_intf
}
void main() {
struct hw_ip_pair *hi_pair;
char IP_str[20], cache_hw_addr[6];
fd_set rset;
int cache_ifindex, cache_hatype;
struct hw_addr HWaddr;
hi_pair = malloc(sizeof(struct hw_ip_pair));
get_hw_ip_pair(hi_pair);
printf("My IP :%s,\t HW addr", hi_pair->ip_addr);
print_mac_to_string(hi_pair->hw_addr);
printf("\n");
int pf_pack_sockfd = create_pf_pack_socket();
void* buffer = (void*)malloc(ETH_FRAME_LEN);
int listen_sockfd, conn_sockfd, clilen, n;
struct sockaddr_un servaddr, cliaddr;
char sendline[MAXLINE], recvline[MAXLINE];
struct sockaddr_in *destIP = malloc(sizeof(struct sockaddr_in));
char ip_addr[20];
struct arp_packet *arp_req = malloc(sizeof(struct arp_packet));
struct arp_packet *arp_rep = malloc(sizeof(struct arp_packet));
struct arp_packet *arp_recv = malloc(sizeof(struct arp_packet));
struct sockaddr_ll socket_address;
int ll_len = sizeof(struct sockaddr_ll);
int i=0;
listen_sockfd = Socket(AF_LOCAL, SOCK_STREAM, 0);
unlink(SUN_PATH_ARP);
bzero(&servaddr, sizeof(servaddr));
servaddr.sun_family = AF_LOCAL;
strcpy(servaddr.sun_path, SUN_PATH_ARP);
Bind(listen_sockfd, (SA *) &servaddr, sizeof(servaddr));
Listen(listen_sockfd, LISTENQ);
int lookup_flag=0;
clilen = sizeof(struct sockaddr_un);
while(1) {
FD_ZERO(&rset);
FD_SET(listen_sockfd, &rset);
FD_SET(pf_pack_sockfd, &rset);
FD_SET(conn_sockfd, &rset);
int max;
if(conn_sockfd != 0)
max = max(max(listen_sockfd, conn_sockfd),pf_pack_sockfd);
else
max = max(listen_sockfd,pf_pack_sockfd);
int ret = select(max+1, &rset, NULL, NULL, NULL);
if(FD_ISSET(listen_sockfd, &rset)) {
conn_sockfd = Accept(listen_sockfd, (SA *) &cliaddr, &clilen);
/* n = read(conn_sockfd, destIP, sizeof(struct sockaddr_in));
Inet_ntop(AF_INET, &(destIP->sin_addr), ip_addr, 20);
// Lookup for the <HW,IP> pair in the ARP cache
lookup_arp_cache(ip_addr, cache_hw_addr, &cache_ifindex, &cache_hatype,&lookup_flag);
if(lookup_flag == 0) {
printf("Entry not found from cache\n");
create_arp_request_packet(arp_req, ip_addr, hi_pair);
send_arp_request(pf_pack_sockfd, arp_req, hi_pair, conn_sockfd);
}
else{
printf("Entry found from cache\n");
// Send from cache
HWaddr.sll_ifindex = cache_ifindex;
HWaddr.sll_hatype = cache_hatype;
HWaddr.sll_halen = sizeof(cache_hatype);
memcpy(HWaddr.mac_addr, cache_hw_addr,6);
print_mac_to_string(HWaddr.mac_addr);
Write(conn_sockfd, (void *)&HWaddr, sizeof(HWaddr));
close(conn_sockfd);
}
printf("Sent ARP request\n");
*/ }
else if(ret!= -1 && FD_ISSET(conn_sockfd, &rset)) {
n = read(conn_sockfd, destIP, sizeof(struct sockaddr_in));
Inet_ntop(AF_INET, &(destIP->sin_addr), ip_addr, 20);
// Lookup for the <HW,IP> pair in the ARP cache
lookup_arp_cache(ip_addr, cache_hw_addr, &cache_ifindex, &cache_hatype,&lookup_flag);
if(lookup_flag == 0) {
create_arp_request_packet(arp_req, ip_addr, hi_pair);
printf("send 1\n");
send_arp_request(pf_pack_sockfd, arp_req, hi_pair, conn_sockfd);
}
else{
// Send from cache
HWaddr.sll_ifindex = cache_ifindex;
HWaddr.sll_hatype = cache_hatype;
HWaddr.sll_halen = sizeof(cache_hatype);
memcpy(HWaddr.mac_addr, cache_hw_addr,6);
// print_mac_to_string(HWaddr.mac_addr);
Write(conn_sockfd, (void *)&HWaddr, sizeof(HWaddr));
close(conn_sockfd);
conn_sockfd = 0;
}
}
else if(FD_ISSET(pf_pack_sockfd, &rset)) {
Recvfrom(pf_pack_sockfd, buffer, ETH_FRAME_LEN, 0, (SA *)&socket_address, &ll_len);
void *data = buffer + 14;
arp_rep = (struct arp_packet *)data;
if (arp_rep->id == ARP_ID){
if(arp_rep->op == ARP_REQ) {
if(strcmp(arp_rep->dest_IP, hi_pair->ip_addr) == 0) {
printf("Printing Ethernet Header and ARP Request Packet Received\n");
print_ethernet_and_arp(arp_rep->src_mac, arp_rep->dest_mac, arp_rep);
add_to_arp_cache_list(arp_rep->src_IP, arp_rep->src_mac, socket_address.sll_ifindex, socket_address.sll_hatype, conn_sockfd, 1);
// print_arp_cache_list();
create_arp_reply_packet(arp_recv, arp_rep->src_IP, hi_pair, arp_rep->src_mac, arp_rep->id);
send_arp_reply(pf_pack_sockfd, arp_recv, hi_pair, socket_address.sll_ifindex);
}
else {
update_arp_cache(arp_rep->src_IP, arp_rep->src_mac, socket_address.sll_ifindex, 0, conn_sockfd);
}
continue;
}
else if(arp_rep->op == ARP_REP) {
if(ret == -1) {
delete_from_arp_cache(arp_rep->src_IP);
// print_arp_cache_list();
continue;
}
printf("Printing Ethernet Header and ARP Reply Packet Received\n");
print_ethernet_and_arp(arp_rep->src_mac, arp_rep->dest_mac, arp_rep);
update_arp_cache(arp_rep->src_IP, arp_rep->src_mac, socket_address.sll_ifindex, 0, conn_sockfd);
// print_arp_cache_list();
HWaddr.sll_ifindex = socket_address.sll_ifindex;
HWaddr.sll_hatype = socket_address.sll_hatype;
HWaddr.sll_halen = socket_address.sll_halen;
memcpy(HWaddr.mac_addr, arp_rep->src_mac,6);
// print_mac_to_string(HWaddr.mac_addr);
Write(conn_sockfd, (void *)&HWaddr, sizeof(HWaddr));
close(conn_sockfd);
conn_sockfd = 0;
update_arp_cache(arp_rep->src_IP, arp_rep->src_mac, socket_address.sll_ifindex, 0, -1);
// print_arp_cache_list();
}
}
}
}
}
static void route_ip_packet(struct sr_instance *sr, uint8_t *packet, size_t len, char *interface) {
// Copy the IP header
struct ip *ip_header = calloc(1, sizeof(struct ip));
memcpy(ip_header, packet + sizeof(struct sr_ethernet_hdr), sizeof(struct ip));
// The IP header is a dirty liar
int actual_header_length = ip_header->ip_hl * 4;
int ip_packet_len = len - sizeof(struct sr_ethernet_hdr);
// Decrement the TTL and check if it's 0
ip_header->ip_ttl -= 1;
if(ip_header->ip_ttl <= 0) {
return;
}
// Zero out the old checksum
ip_header->ip_sum = 0;
// Create a buffer to calculate the checksum
uint16_t *header_buffer;
// Create a chunk of memory aligned to 16 bits
posix_memalign((void **) &header_buffer, CHECKSUM_ALIGNMENT, actual_header_length);
bzero(header_buffer, actual_header_length);
// Copy required IP header fields
memcpy(header_buffer, ip_header, sizeof(struct ip));
// Copy the original IP header flags
memcpy(header_buffer, packet + sizeof(struct sr_ethernet_hdr) + sizeof(struct ip),
actual_header_length - sizeof(struct ip));
// Calculate the new checksum
ip_header->ip_sum = header_checksum(header_buffer, actual_header_length / 2);
free(header_buffer);
// Get the IP packet's destination
struct in_addr destination_addr = ip_header->ip_dst;
uint32_t destination_ip = destination_addr.s_addr;
// Check if we're the destination
struct sr_if *iface = sr_get_interface(sr, interface);
if(destination_ip == iface->ip) {
printf("Dropping packet bound for router on %s\n", interface);
return;
}
// Check the routing table for the correct gateway to forward the packet through
struct sr_rt *table_entry = search_routing_table(sr, destination_ip);
printf("\tThe nexthop is %s\n", inet_ntoa(table_entry->gw));
if(table_entry) {
// Get the interface for the gateway
struct sr_if *gw_iface = sr_get_interface(sr, table_entry->interface);
// Determine the IP to forward to
struct in_addr nexthop;
// Determine if the IP to forward to is in our network
if(table_entry->gw.s_addr == 0) {
nexthop = destination_addr;
} else {
nexthop = table_entry->gw;
}
// Create an updated IP packet with the correct headers/data
uint8_t *updated_packet = calloc(ip_packet_len, sizeof(uint8_t));
memcpy(updated_packet, ip_header, actual_header_length);
memcpy(updated_packet + actual_header_length,
packet + sizeof(struct sr_ethernet_hdr ) + actual_header_length,
len - sizeof(struct sr_ethernet_hdr ) - actual_header_length);
// Search the ARP cache for the nexthop
uint8_t *gw_addr = search_arp_cache(cache, nexthop.s_addr);
if(gw_addr) {
printf("\tForwarding packet bound for %s through next hop @ ",
inet_ntoa(destination_addr));
printf("%s (", inet_ntoa(table_entry->gw));
print_ethernet_addr(gw_addr, stdout);
printf(")\n");
uint8_t *buffer = pack_ethernet_packet(gw_addr, gw_iface->addr, ETHERTYPE_IP,
updated_packet, ip_packet_len);
sr_send_packet(sr, buffer, len, gw_iface->name);
} else {
// Otherwise we cache the IP packet and make an ARP request
printf("\tSending ARP request to %s (%s), to forward packet bound for ",
inet_ntoa(nexthop), gw_iface->name);
printf("%s\n", inet_ntoa(destination_addr));
add_ip_cache_entry(ip_cache, updated_packet, nexthop, ip_packet_len);
send_arp_request(sr, gw_iface, nexthop);
}
} else {
// TODO: What do we do here?
}
}
/**
* \brief detect and resolve IP conflict
* \param the ethernet interface entry in the MIB for which we change the IP
* \param interface the name of this interface (eth0/enp2s0/lo...)
* \return TRUE if conflict could be resolved, FALSE otherwise
*/
gboolean ip_conflict_detection( struct ethernetIfTableEntry *if_entry, gchar *interface ){
g_debug ("ip_conflict_detection()" );
/* select a random time to wait between 0 en PROBE_WAIT */
srand(time(NULL));
/* PROBE_WAIT is given in second, if we want a integer value for microsecond , we should multiply it by 1000000 */
gdouble probe_wait = ((gdouble) rand()/ (gdouble)(RAND_MAX)) * PROBE_WAIT;
/* send PROB_NUM ARP PROBE messages between space randomly between PROBE_MIN and PROBE_MAX number*/
gdouble space = (((gdouble) rand()/ (gdouble)(RAND_MAX)) / (gdouble) ((PROBE_MAX - PROBE_MIN) * PROBE_NUM));
gdouble time_passed = 0 ;
gboolean conflict = TRUE ;
in_addr_t max_ip_value = inet_addr ( DEFAULT_STATIC_IP ) ;
GTimer *timer = g_timer_new();
/* wait probe_wait */
g_debug ("waiting %G second(s)", probe_wait);
g_timer_start( timer );
while(time_passed < probe_wait){
time_passed = g_timer_elapsed ( timer, NULL );
}
int sending_socket_fd;
struct sockaddr_ll sa;
if ( !prepare_arp_request_socket (if_entry , &sending_socket_fd , &sa )){
g_critical("cannot prepare socket for ARP request");
return FALSE;
}
/* variable for the ethernet frame to build */
struct arp_packet pkt;
int ethernet_frame_length;
uint8_t *ethernet_frame;
while ( conflict ){
/* build the ethernet frame */
ethernet_frame = init_ethernet_frame (if_entry , &pkt, ðernet_frame_length, TRUE );
if ( !ethernet_frame ){
g_critical("cannot build ethernet frame for ARP request");
return FALSE;
}
/* wait PROBE_MIN */
g_debug ("waiting %d second(s)", PROBE_MIN);
g_timer_reset( timer );
time_passed = g_timer_elapsed ( timer, NULL );
while( time_passed < (PROBE_MIN) ){
time_passed = g_timer_elapsed ( timer, NULL );
}
/* send ARP PROBE message PROBE_NUM times with an interval probe_wait */
g_debug("send ARP Probe message %d times every %G second(s)", PROBE_NUM, space);
for( int i = 1 ; i <= PROBE_NUM ; i ++){
g_timer_reset( timer );
time_passed = g_timer_elapsed ( timer, NULL );
while( time_passed < space ){
time_passed = g_timer_elapsed ( timer, NULL );
}
send_arp_request( sending_socket_fd , ethernet_frame, ethernet_frame_length, sa );
}
conflict = receive_arp_reply( ) ;
/* if receive_arp_reply return FALSE there is a conflict, else, we are fine with this IP */
if ( conflict ){
struct in_addr device_ip;
device_ip.s_addr = if_entry->ethernetIfIpAddress ;
g_debug("IP address %s already in use", inet_ntoa ( device_ip ));
/* pick up a new random IP */
if_entry->ethernetIfIpAddressConflict = if_entry->ethernetIfIpAddress ;
if_entry->ethernetIfIpAddress = random_ip_for_conflict(interface);
if ( if_entry->ethernetIfIpAddress == max_ip_value )
return TRUE;
/* send trap */
send_ipAddressConflict_trap();
}
}
/* build and send probe message */
ethernet_frame = init_ethernet_frame (if_entry , &pkt, ðernet_frame_length, FALSE );
send_arp_request( sending_socket_fd , ethernet_frame, ethernet_frame_length, sa );
/* close sockets */
close ( sending_socket_fd );
/* free the ethernet frame build */
free(ethernet_frame);
return FALSE;
}
/*
* 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;
}
}
