void send_arp(struct link_int *l, u_char * device)
{
int n;
u_char *buf;
buf = (u_char *) malloc(ARP_H + ETH_H);
if (!buf) {
perror("no packet memory");
exit(EXIT_FAILURE);
}
memset(buf, 0, ARP_H + ETH_H);
build_ethernet(enet_dst, enet_src, ETHERTYPE_ARP, NULL, 0, buf);
build_arp(ARPHRD_ETHER, ETHERTYPE_IP, 6, 4, ARPOP_REQUEST, enet_src,
(void *)&ip_dst, enet_dst, (void *)&ip_dst, NULL, 0, buf + ETH_H);
n = write_link_layer(l, device, buf, ARP_H + ETH_H);
printf("Wrote %d byte ARP packet through linktype %d\n", n, l->linktype);
}
/* Send ARP Reply packet */
void inject_arp_reply(char *eth_src, char *ip_src, char *eth_target, char *ip_target)
{
packet_t *p = NULL;
ether_t *ether = NULL;
arp_t *arp;
p = packet_new_empty();
ether = build_ethernet(eth_src, eth_target, ETHER_TYPE_ARP);
packet_append_header(p, PROTO_NAME_ETHER, (void *)ether, ETHER_HDR_LEN);
arp = build_arp_ethip(ARP_OP_REPLY, eth_src, ip_src, eth_target, ip_target);
packet_append_header(p, PROTO_NAME_ARP, (void *)arp, sizeof(arp_t) + sizeof(arp_ethip_t));
inject(p);
packet_free(p);
free(ether);
free(arp);
}
/* Send custom ARP message */
void inject_arp(char *eth_src, char *eth_dst, _uint16 opcode, char *sha, char *spa, char *tha, char *tpa)
{
packet_t *p = NULL;
ether_t *ether = NULL;
arp_t *arp;
p = packet_new_empty();
ether = build_ethernet(eth_src, eth_dst, ETHER_TYPE_ARP);
packet_append_header(p, PROTO_NAME_ETHER, (void *)ether, ETHER_HDR_LEN);
arp = build_arp_ethip(opcode, sha, spa, tha, tpa);
packet_append_header(p, PROTO_NAME_ARP, (void *)arp, sizeof(arp_t) + sizeof(arp_ethip_t));
inject(p);
packet_free(p);
free(ether);
free(arp);
}
int
main(int argc, char *argv[])
{
libnet_t *l;
char *device = "eth0";
char errbuf[LIBNET_ERRBUF_SIZE];
libnet_ptag_t ipo_ptag = 0;
libnet_ptag_t ip_ptag = 0;
libnet_ptag_t eth_ptag = 0;
int ip_len = 0;
l = libnet_init( LIBNET_LINK, device, errbuf);
assert(l);
printf("Packet: options=4, payload=0\n");
ip_len = 20 + 4 + 0; /* ip + options + payload */
ipo_ptag = build_ipo(l, ipo_ptag, 4);
ip_ptag = build_ipv4(l, ip_ptag, 0, 24);
eth_ptag = build_ethernet(l, eth_ptag);
assert_lengths(l, 24, 6, 0);
ipo_ptag = ip_ptag = eth_ptag = 0;
libnet_clear_packet(l);
printf("Packet: options=3, payload=1\n");
ip_len = 20 + 4 + 1; /* ip + options + payload */
ipo_ptag = build_ipo(l, ipo_ptag, 3);
ip_ptag = build_ipv4(l, ip_ptag, 1, 25);
eth_ptag = build_ethernet(l, eth_ptag);
assert_lengths(l, 25, 6, 1);
ipo_ptag = ip_ptag = eth_ptag = 0;
libnet_clear_packet(l);
printf("Packet: options=3, payload=1\n");
ip_len = 20 + 4 + 1; /* ip + options + payload */
ipo_ptag = build_ipo(l, ipo_ptag, 3);
ip_ptag = build_ipv4(l, ip_ptag, 1, ip_len);
eth_ptag = build_ethernet(l, eth_ptag);
assert_lengths(l, 25, 6, 1);
printf("... modify -> options=40\n");
ip_len = 20 + 40 + 1; /* ip + options + payload */
ipo_ptag = build_ipo(l, ipo_ptag, 40);
assert_lengths(l, ip_len, 15, 1);
printf("... modify -> options=0\n");
ip_len = 20 + 0 + 1; /* ip + options + payload */
ipo_ptag = build_ipo(l, ipo_ptag, 0);
assert_lengths(l, ip_len, 5, 1);
printf("... modify -> options=5\n");
ip_len = 20 + 8 + 1; /* ip + options + payload */
ipo_ptag = build_ipo(l, ipo_ptag, 5);
assert_lengths(l, ip_len, 7, 1);
printf("... modify -> ip_payload=5\n");
ip_len = 20 + 8 + 5; /* ip + options + payload */
ip_ptag = build_ipv4(l, ip_ptag, 5, ip_len);
assert_lengths(l, ip_len, 7, 1);
ipo_ptag = ip_ptag = eth_ptag = 0;
libnet_clear_packet(l);
return (EXIT_SUCCESS);
}