RN/Blatt02/A203/tuntap.c
2024-11-23 18:09:49 +01:00

109 lines
2.3 KiB
C

#include "arp_packet.h"
#define CLEAR(x) memset(&(x), 0x00, sizeof(x))
#define IFNAME "tap0"
// #define IFNAME "tun0"
#define BUFLEN 1600
static int tun_alloc(char *dev)
{
struct ifreq ifr;
int fd, err;
if( (fd = open("/dev/net/tun", O_RDWR)) < 0 ) {
perror("Cannot open TUN/TAP dev\n"
"Make sure one exists with "
"'$ mknod /dev/net/tun c 10 200'");
exit(1);
}
CLEAR(ifr);
/* Flags: IFF_TUN - TUN device (no Ethernet headers)
* IFF_TAP - TAP device
*
* IFF_NO_PI - Do not provide packet information
*/
ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
if( *dev ) {
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
}
if( (err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0 ){
perror("ERR: Could not ioctl tun");
close(fd);
return err;
}
strcpy(dev, ifr.ifr_name);
return fd;
}
// int check_ip(uint8_t * ip, int length){
// if(length != TARGET_IP_A_S) return UNEQUAL;
// int8_t pc2[4]={10,5,1,2};
// for(size_t i = 0 ; i < length ; i++)
// printf("%X, %X \n", ip[i], pc2[i]);
//
// for(size_t i = 0 ; i < length ; i++)
// if(ip[i]!=pc2[i]) return FAILED;
// return SUCCESS;
//}
//
int main (int argc, char *argv[]){
char dev[IFNAMSIZ];
int tun_fd;
uint8_t local_ip[4] = {10, 5, 1, 10};
uint8_t local_mac[6] = {0xD6,0x74,0x45,0xDC,0x5A,0xCD};
if (argc > 1) {
assert(strlen(argv[1]) < IFNAMSIZ);
strcpy(dev, argv[1]);
} else {
strcpy(dev, IFNAME);
}
printf("device name: %s\n", dev);
tun_fd = tun_alloc(dev);
int running = 1;
uint8_t buf[BUFLEN];
while (running) {
int nread;
if ((nread = read(tun_fd, buf, BUFLEN)) < 0) {
perror("ERR: Read from tun_fd");
break;
}
// buf[nread] = '\0';
printf("buf :");
print_hex(buf, nread);
mac_hdr hdr;
pkt_data pkt;
if(parse_arp_packet(&hdr, &pkt, buf, nread) == FAILED){
perror("ERR: Cannot parse the packet");
}
if(receive_arp_packet(&hdr, &pkt, buf, nread, local_ip, local_mac) == FAILED){
perror("ERR: Cannot process the packet");
}
if(send_arp_response(tun_fd, buf, nread, &pkt, &hdr) == FAILED){
perror("ERR: Cannot send the response");
}
printf("Read %d bytes from device %s\n\n", nread, dev);
}
close(tun_fd);
return EXIT_SUCCESS;
}