tncattach/TAP.c

#include "TAP.h"

char tap_name[IFNAMSIZ];

extern bool verbose;
extern bool noipv6;
extern bool set_ipv4;
extern bool set_netmask;
extern bool noup;
extern int mtu;
extern int device_type;
extern char if_name[IFNAMSIZ];
extern char* ipv4_addr;
extern char* netmask;
extern void cleanup();

int open_tap(void) {
	struct ifreq ifr;
	int fd = open("/dev/net/tun", O_RDWR);

	if (fd < 0) {
		perror("Could not open clone device");
		exit(1);
	} else {
		memset(&ifr, 0, sizeof(ifr));
		// TODO: Enable PI header again?

		if (device_type == IF_TAP) {
			ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
		} else if (device_type == IF_TUN) {
			ifr.ifr_flags = IFF_TUN;
		} else {
			printf("Error: Unsupported interface type\r\n");
			cleanup();
			exit(1);
		}

		strcpy(tap_name, "tnc%d");
		strncpy(ifr.ifr_name, tap_name, IFNAMSIZ);

		if (ioctl(fd, TUNSETIFF, &ifr) < 0) {
			perror("Could not configure network interface");
			exit(1);
		} else {
			strcpy(if_name, ifr.ifr_name);
			
			int inet = socket(AF_INET, SOCK_DGRAM, 0);
			if (inet == -1) {
				perror("Could not open AF_INET socket\r\n");
				cleanup();
				exit(1);
			} else {
				if (ioctl(inet, SIOCGIFMTU, &ifr) < 0) {
					perror("Could not get interface flags from kernel");
					close(inet);
					cleanup();
					exit(1);
				} else {
					ifr.ifr_mtu = mtu;
					if (ioctl(inet, SIOCSIFMTU, &ifr) < 0) {
						perror("Could not configure interface MTU");
						close(inet);
						cleanup();
						exit(1);
					}

					// Configure TX queue length
					if (ioctl(inet, SIOCGIFTXQLEN, &ifr) < 0) {
						perror("Could not get interface flags from kernel");
						close(inet);
						cleanup();
						exit(1);
					} else {
						ifr.ifr_qlen = TXQUEUELEN;
						if (ioctl(inet, SIOCSIFTXQLEN, &ifr) < 0) {
							perror("Could not set interface TX queue length");
							close(inet);
							cleanup();
							exit(1);
						}
					}

					// Configure ARP characteristics
					char path_buf[256];
					if (device_type == IF_TAP) {
						snprintf(path_buf, sizeof(path_buf), "/proc/sys/net/ipv4/neigh/%s/base_reachable_time_ms", ifr.ifr_name);
						int arp_fd = open(path_buf, O_WRONLY);
						if (arp_fd < 0) {
							perror("Could not open proc entry for ARP parameters");
							close(inet);
							cleanup();
							exit(1);
						} else {
							if (dprintf(arp_fd, "%d", ARP_BASE_REACHABLE_TIME*1000) <= 0) {
								perror("Could not configure interface ARP parameter base_reachable_time_ms");
								close(inet);
								close(arp_fd);
								cleanup();
								exit(1);
							} else {
								close(arp_fd);
							}
						}

						snprintf(path_buf, sizeof(path_buf), "/proc/sys/net/ipv4/neigh/%s/retrans_time_ms", ifr.ifr_name);
						arp_fd = open(path_buf, O_WRONLY);
						if (arp_fd < 0) {
							perror("Could not open proc entry for ARP parameters");
							close(inet);
							cleanup();
							exit(1);
						} else {
							if (dprintf(arp_fd, "%d", ARP_RETRANS_TIME*1000) <= 0) {
								perror("Could not configure interface ARP parameter retrans_time_ms");
								close(inet);
								close(arp_fd);
								cleanup();
								exit(1);
							} else {
								close(arp_fd);
							}
						}
					}

					// Bring up if requested
					if (!noup) {
						if (ioctl(inet, SIOCGIFFLAGS, &ifr) < 0) {
							perror("Could not get interface flags from kernel");
							close(inet);
							cleanup();
							exit(1);
						} else {
							ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
							if (ioctl(inet, SIOCSIFFLAGS, &ifr) < 0) {
								perror("Could not bring up interface");
								close(inet);
								cleanup();
								exit(1);
							} else {
								if (set_ipv4) {
									struct ifreq a_ifr;
									struct sockaddr_in addr, snm;

									memset(&a_ifr, 0, sizeof(a_ifr));
									memset(&addr, 0, sizeof(addr));
									memset(&snm, 0, sizeof(addr));
									strncpy(a_ifr.ifr_name, ifr.ifr_name, IFNAMSIZ);
									addr.sin_family = AF_INET;
									snm.sin_family = AF_INET;

									int addr_conversion = inet_pton(AF_INET, ipv4_addr, &(addr.sin_addr));
									if (addr_conversion != 1) {
										printf("Error: Invalid IPv4 address specified\r\n");
										close(inet);
										cleanup();
										exit(1);
									} else {
										a_ifr.ifr_addr = *(struct sockaddr*)&addr;
										if (ioctl(inet, SIOCSIFADDR, &a_ifr) < 0) {
											perror("Could not set IP-address");
											close(inet);
											cleanup();
											exit(1);
										} else {
											if (set_netmask) {
												int snm_conversion = inet_pton(AF_INET, netmask, &(snm.sin_addr));
												if (snm_conversion != 1) {
													printf("Error: Invalid subnet mask specified\r\n");
													close(inet);
													cleanup();
													exit(1);
												} else {
													a_ifr.ifr_addr = *(struct sockaddr*)&snm;
													if (ioctl(inet, SIOCSIFNETMASK, &a_ifr) < 0) {
														perror("Could not set subnet mask");
														close(inet);
														cleanup();
														exit(1);
													}
												}
											}
										}
									}
								}
							}
						}
					}
				}
			}

			return fd;
		}
	}
}

int close_tap(int tap_fd) {
	return close(tap_fd);
}