tinc-feth/src/bsd/device.c

/*
    device.c -- Interaction BSD tun/tap device
    Copyright (C) 2001-2005 Ivo Timmermans,
                  2001-2016 Guus Sliepen <guus@tinc-vpn.org>
                  2009      Grzegorz Dymarek <gregd72002@googlemail.com>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include "../system.h"

#include "../conf.h"
#include "../device.h"
#include "../logger.h"
#include "../net.h"
#include "../route.h"
#include "../utils.h"
#include "../xalloc.h"

#ifdef ENABLE_TUNEMU
#include "tunemu.h"
#endif

#ifdef HAVE_NET_IF_UTUN_H
#include <sys/sys_domain.h>
#include <sys/kern_control.h>
#include <net/if_utun.h>
#endif

#ifdef HAVE_DARWIN
#include <net/bpf.h>
#include <net/ndrv.h>
#endif

#define DEFAULT_TUN_DEVICE "/dev/tun0"
#define DEFAULT_TAP_DEVICE "/dev/tap0"

typedef enum device_type {
	DEVICE_TYPE_TUN,
	DEVICE_TYPE_TUNIFHEAD,
	DEVICE_TYPE_TAP,
#ifdef ENABLE_TUNEMU
	DEVICE_TYPE_TUNEMU,
#endif
	DEVICE_TYPE_UTUN,
#ifdef HAVE_DARWIN
	DEVICE_TYPE_FETH,
#endif
} device_type_t;

int device_fd = -1;
char *device = NULL;
char *iface = NULL;
static const char *device_info = "OS X utun device";
static uint64_t device_total_in = 0;
static uint64_t device_total_out = 0;
#if defined(ENABLE_TUNEMU)
static device_type_t device_type = DEVICE_TYPE_TUNEMU;
#elif defined(HAVE_OPENBSD) || defined(HAVE_FREEBSD) || defined(HAVE_DRAGONFLY)
static device_type_t device_type = DEVICE_TYPE_TUNIFHEAD;
#else
static device_type_t device_type = DEVICE_TYPE_TUN;
#endif

#ifdef HAVE_DARWIN
/* feth (fake ethernet) device support for macOS 10.13+
 *
 * Uses undocumented feth interfaces (like Linux veth pairs) to provide
 * Layer 2 / TAP functionality without kernel extensions.
 *
 * Architecture:
 *   feth<N> (primary) - gets IP assignments, used by tinc-up scripts
 *   feth<N+5000> (peer) - used for packet I/O via BPF read + AF_NDRV write
 *
 * Based on ZeroTier's MacEthernetTapAgent approach.
 */

#define FETH_BPF_BUFSIZE 131072
#define FETH_PEER_OFFSET 5000
#define DEFAULT_FETH_NUM 0

static int feth_ndrv_fd = -1;
static int feth_num = -1;
static char feth_primary[IFNAMSIZ];
static char feth_peer[IFNAMSIZ];
static uint8_t feth_bpf_buf[FETH_BPF_BUFSIZE];
static int feth_bpf_buf_len = 0;
static int feth_bpf_buf_offset = 0;

static bool feth_run_cmd(const char *cmd) {
	ifdebug(TRAFFIC) logger(LOG_DEBUG, "Executing: %s", cmd);

	int ret = system(cmd);

	if(ret != 0) {
		logger(LOG_ERR, "Command failed (exit %d): %s", ret, cmd);
		return false;
	}

	return true;
}

static bool setup_feth(void) {
	char cmd[512];

	/* Parse device number from Device config (e.g. "feth0" -> 0) */
	feth_num = DEFAULT_FETH_NUM;

	if(device) {
		char *p = strstr(device, "feth");

		if(p) {
			int n = atoi(p + 4);

			if(n >= 0 && n < FETH_PEER_OFFSET) {
				feth_num = n;
			}
		}
	}

	snprintf(feth_primary, sizeof(feth_primary), "feth%d", feth_num);
	snprintf(feth_peer, sizeof(feth_peer), "feth%d", feth_num + FETH_PEER_OFFSET);

	/* Create feth pair */
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s create", feth_peer);

	if(!feth_run_cmd(cmd)) {
		logger(LOG_ERR, "Could not create feth peer interface %s", feth_peer);
		return false;
	}

	usleep(10000); /* Brief delay for interface to stabilize */

	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s create", feth_primary);

	if(!feth_run_cmd(cmd)) {
		logger(LOG_ERR, "Could not create feth primary interface %s", feth_primary);
		snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s destroy 2>/dev/null", feth_peer);
		feth_run_cmd(cmd);
		return false;
	}

	/* Peer the interfaces */
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s peer %s", feth_peer, feth_primary);

	if(!feth_run_cmd(cmd)) {
		logger(LOG_ERR, "Could not peer %s with %s", feth_peer, feth_primary);
		goto cleanup;
	}

	/* Set MTU */
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s mtu 1500", feth_primary);
	feth_run_cmd(cmd);
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s mtu 1500", feth_peer);
	feth_run_cmd(cmd);

	/* Bring interfaces up */
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s up", feth_primary);

	if(!feth_run_cmd(cmd)) {
		goto cleanup;
	}

	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s up", feth_peer);

	if(!feth_run_cmd(cmd)) {
		goto cleanup;
	}

	/* Open BPF device */
	char bpf_path[32];

	for(int i = 1; i < 5000; i++) {
		snprintf(bpf_path, sizeof(bpf_path), "/dev/bpf%d", i);
		device_fd = open(bpf_path, O_RDWR);

		if(device_fd >= 0) {
			break;
		}
	}

	if(device_fd < 0) {
		logger(LOG_ERR, "Could not open any BPF device: %s", strerror(errno));
		goto cleanup;
	}

#ifdef FD_CLOEXEC
	fcntl(device_fd, F_SETFD, FD_CLOEXEC);
#endif

	/* Configure BPF - order matters: BIOCSBLEN must come before BIOCSETIF */
	int bpf_bufsize = FETH_BPF_BUFSIZE;

	if(ioctl(device_fd, BIOCSBLEN, &bpf_bufsize) == -1) {
		logger(LOG_ERR, "Could not set BPF buffer size: %s", strerror(errno));
		goto cleanup_bpf;
	}

	struct ifreq ifr;
	memset(&ifr, 0, sizeof(ifr));
	strlcpy(ifr.ifr_name, feth_peer, sizeof(ifr.ifr_name));

	if(ioctl(device_fd, BIOCSETIF, &ifr) == -1) {
		logger(LOG_ERR, "Could not bind BPF to %s: %s", feth_peer, strerror(errno));
		goto cleanup_bpf;
	}

	int enable = 1;

	if(ioctl(device_fd, BIOCIMMEDIATE, &enable) == -1) {
		logger(LOG_ERR, "Could not set BIOCIMMEDIATE: %s", strerror(errno));
		goto cleanup_bpf;
	}

	int disable = 0;

	if(ioctl(device_fd, BIOCSSEESENT, &disable) == -1) {
		logger(LOG_ERR, "Could not set BIOCSSEESENT: %s", strerror(errno));
		goto cleanup_bpf;
	}

	if(ioctl(device_fd, BIOCSHDRCMPLT, &enable) == -1) {
		logger(LOG_ERR, "Could not set BIOCSHDRCMPLT: %s", strerror(errno));
		goto cleanup_bpf;
	}

	if(ioctl(device_fd, BIOCPROMISC, NULL) == -1) {
		logger(LOG_ERR, "Could not set BPF promiscuous mode: %s", strerror(errno));
		goto cleanup_bpf;
	}

	/* Set non-blocking mode for integration with tinc's event loop */
	fcntl(device_fd, F_SETFL, O_NONBLOCK);

	/* Open AF_NDRV socket for writing packets */
	feth_ndrv_fd = socket(PF_NDRV, SOCK_RAW, 0);

	if(feth_ndrv_fd < 0) {
		logger(LOG_ERR, "Could not create AF_NDRV socket: %s", strerror(errno));
		goto cleanup_bpf;
	}

#ifdef FD_CLOEXEC
	fcntl(feth_ndrv_fd, F_SETFD, FD_CLOEXEC);
#endif

	struct sockaddr_ndrv sa_ndrv;
	memset(&sa_ndrv, 0, sizeof(sa_ndrv));
	sa_ndrv.snd_len = sizeof(sa_ndrv);
	sa_ndrv.snd_family = AF_NDRV;
	strlcpy((char *)sa_ndrv.snd_name, feth_peer, sizeof(sa_ndrv.snd_name));

	if(bind(feth_ndrv_fd, (struct sockaddr *)&sa_ndrv, sizeof(sa_ndrv)) == -1) {
		logger(LOG_ERR, "Could not bind AF_NDRV socket to %s: %s", feth_peer, strerror(errno));
		goto cleanup_ndrv;
	}

	if(connect(feth_ndrv_fd, (struct sockaddr *)&sa_ndrv, sizeof(sa_ndrv)) == -1) {
		logger(LOG_ERR, "Could not connect AF_NDRV socket to %s: %s", feth_peer, strerror(errno));
		goto cleanup_ndrv;
	}

	/* Set interface name for tinc-up scripts */
	iface = xstrdup(feth_primary);
	device_info = "macOS feth device";

	/* Initialize BPF read buffer state */
	feth_bpf_buf_len = 0;
	feth_bpf_buf_offset = 0;

	logger(LOG_INFO, "%s is a %s (peer: %s, bpf: %s)", feth_primary, device_info, feth_peer, bpf_path);

	return true;

cleanup_ndrv:
	close(feth_ndrv_fd);
	feth_ndrv_fd = -1;
cleanup_bpf:
	close(device_fd);
	device_fd = -1;
cleanup:
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s destroy 2>/dev/null", feth_primary);
	feth_run_cmd(cmd);
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s destroy 2>/dev/null", feth_peer);
	feth_run_cmd(cmd);
	return false;
}

static void close_feth(void) {
	char cmd[256];

	if(feth_ndrv_fd >= 0) {
		close(feth_ndrv_fd);
		feth_ndrv_fd = -1;
	}

	if(device_fd >= 0) {
		close(device_fd);
		device_fd = -1;
	}

	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s destroy 2>/dev/null", feth_primary);
	feth_run_cmd(cmd);
	snprintf(cmd, sizeof(cmd), "/sbin/ifconfig %s destroy 2>/dev/null", feth_peer);
	feth_run_cmd(cmd);

	logger(LOG_INFO, "Destroyed feth pair %s/%s", feth_primary, feth_peer);
}

static bool read_feth_packet(vpn_packet_t *packet) {
	/* BPF returns multiple packets per read() in a buffer with bpf_hdr prefixes.
	 * We maintain a static buffer and return one packet per call. */

	if(feth_bpf_buf_offset >= feth_bpf_buf_len) {
		/* Buffer exhausted, read more from BPF */
		feth_bpf_buf_len = read(device_fd, feth_bpf_buf, FETH_BPF_BUFSIZE);

		if(feth_bpf_buf_len <= 0) {
			if(errno == EAGAIN || errno == EWOULDBLOCK) {
				return false;
			}

			logger(LOG_ERR, "Error reading from BPF: %s", strerror(errno));
			return false;
		}

		feth_bpf_buf_offset = 0;
	}

	/* Parse next packet from buffer */
	struct bpf_hdr *bh = (struct bpf_hdr *)(feth_bpf_buf + feth_bpf_buf_offset);
	uint8_t *frame = feth_bpf_buf + feth_bpf_buf_offset + bh->bh_hdrlen;
	int caplen = bh->bh_caplen;

	/* Advance offset to next packet (word-aligned) */
	feth_bpf_buf_offset += BPF_WORDALIGN(bh->bh_hdrlen + bh->bh_caplen);

	if(caplen <= 0 || caplen > MTU) {
		ifdebug(TRAFFIC) logger(LOG_DEBUG, "Dropping oversized feth packet (%d bytes)", caplen);
		return false;
	}

	memcpy(packet->data, frame, caplen);
	packet->len = caplen;

	return true;
}

static bool write_feth_packet(vpn_packet_t *packet) {
	if(write(feth_ndrv_fd, packet->data, packet->len) < 0) {
		logger(LOG_ERR, "Error writing to feth AF_NDRV: %s", strerror(errno));
		return false;
	}

	return true;
}
#endif /* HAVE_DARWIN */

#ifdef HAVE_NET_IF_UTUN_H
static bool setup_utun(void) {
	device_fd = socket(PF_SYSTEM, SOCK_DGRAM, SYSPROTO_CONTROL);

	if(device_fd == -1) {
		logger(LOG_ERR, "Could not open PF_SYSTEM socket: %s\n", strerror(errno));
		return false;
	}

	struct ctl_info info = {};

	strlcpy(info.ctl_name, UTUN_CONTROL_NAME, sizeof(info.ctl_name));

	if(ioctl(device_fd, CTLIOCGINFO, &info) == -1) {
		logger(LOG_ERR, "ioctl(CTLIOCGINFO) failed: %s", strerror(errno));
		return false;
	}

	int unit = -1;
	char *p = strstr(device, "utun"), *e = NULL;

	if(p) {
		unit = strtol(p + 4, &e, 10);

		if(!e) {
			unit = -1;
		}
	}

	struct sockaddr_ctl sc = {
		.sc_id = info.ctl_id,
		.sc_len = sizeof(sc),
		.sc_family = AF_SYSTEM,
		.ss_sysaddr = AF_SYS_CONTROL,
		.sc_unit = unit + 1,
	};

	if(connect(device_fd, (struct sockaddr *)&sc, sizeof(sc)) == -1) {
		logger(LOG_ERR, "Could not connect utun socket: %s\n", strerror(errno));
		return false;
	}

	char name[64] = "";
	socklen_t len = sizeof(name);

	if(getsockopt(device_fd, SYSPROTO_CONTROL, UTUN_OPT_IFNAME, name, &len)) {
		iface = xstrdup(device);
	} else {
		iface = xstrdup(name);
	}

	logger(LOG_INFO, "%s is a %s", device, device_info);

	return true;
}
#endif

static bool setup_device(void) {
	// Find out which device file to open

	if(!get_config_string(lookup_config(config_tree, "Device"), &device)) {
		if(routing_mode == RMODE_ROUTER) {
			device = xstrdup(DEFAULT_TUN_DEVICE);
		} else {
			device = xstrdup(DEFAULT_TAP_DEVICE);
		}
	}

	// Find out if it's supposed to be a tun or a tap device

	char *type;

	if(get_config_string(lookup_config(config_tree, "DeviceType"), &type)) {
		if(!strcasecmp(type, "tun"))
			/* use default */;

#ifdef ENABLE_TUNEMU
		else if(!strcasecmp(type, "tunemu")) {
			device_type = DEVICE_TYPE_TUNEMU;
		}

#endif
#ifdef HAVE_NET_IF_UTUN_H
		else if(!strcasecmp(type, "utun")) {
			device_type = DEVICE_TYPE_UTUN;
		}

#endif
#ifdef HAVE_DARWIN
		else if(!strcasecmp(type, "feth")) {
			device_type = DEVICE_TYPE_FETH;
		}

#endif
		else if(!strcasecmp(type, "tunnohead")) {
			device_type = DEVICE_TYPE_TUN;
		} else if(!strcasecmp(type, "tunifhead")) {
			device_type = DEVICE_TYPE_TUNIFHEAD;
		} else if(!strcasecmp(type, "tap")) {
			device_type = DEVICE_TYPE_TAP;
		} else {
			logger(LOG_ERR, "Unknown device type %s!", type);
			return false;
		}
	} else {
#ifdef HAVE_NET_IF_UTUN_H

		if(strncmp(device, "utun", 4) == 0 || strncmp(device, "/dev/utun", 9) == 0) {
			device_type = DEVICE_TYPE_UTUN;
		} else
#endif
#ifdef HAVE_DARWIN

		if(strncmp(device, "feth", 4) == 0) {
			device_type = DEVICE_TYPE_FETH;
		} else
#endif
			if(strstr(device, "tap") || routing_mode != RMODE_ROUTER) {
				device_type = DEVICE_TYPE_TAP;
			}
	}

#ifdef HAVE_DARWIN

	if(routing_mode == RMODE_SWITCH && device_type != DEVICE_TYPE_TAP && device_type != DEVICE_TYPE_FETH) {
		logger(LOG_ERR, "Only tap or feth devices support switch mode!");
		return false;
	}

#else

	if(routing_mode == RMODE_SWITCH && device_type != DEVICE_TYPE_TAP) {
		logger(LOG_ERR, "Only tap devices support switch mode!");
		return false;
	}

#endif

	// Open the device

	switch(device_type) {
#ifdef ENABLE_TUNEMU

	case DEVICE_TYPE_TUNEMU: {
		char dynamic_name[256] = "";
		device_fd = tunemu_open(dynamic_name);
	}
	break;
#endif
#ifdef HAVE_NET_IF_UTUN_H

	case DEVICE_TYPE_UTUN:
		return setup_utun();
#endif
#ifdef HAVE_DARWIN

	case DEVICE_TYPE_FETH:
		return setup_feth();
#endif

	default:
		device_fd = open(device, O_RDWR | O_NONBLOCK);
	}

	if(device_fd < 0) {
		logger(LOG_ERR, "Could not open %s: %s", device, strerror(errno));
		return false;
	}

#ifdef FD_CLOEXEC
	fcntl(device_fd, F_SETFD, FD_CLOEXEC);
#endif

	// Guess what the corresponding interface is called

	char *realname = NULL;

#if defined(HAVE_FDEVNAME)
	realname = fdevname(device_fd);
#elif defined(HAVE_DEVNAME)
	struct stat buf;

	if(!fstat(device_fd, &buf)) {
		realname = devname(buf.st_rdev, S_IFCHR);
	}

#endif

	if(!realname) {
		realname = device;
	}

	if(!get_config_string(lookup_config(config_tree, "Interface"), &iface)) {
		iface = xstrdup(strrchr(realname, '/') ? strrchr(realname, '/') + 1 : realname);
	} else if(strcmp(iface, strrchr(realname, '/') ? strrchr(realname, '/') + 1 : realname)) {
		logger(LOG_WARNING, "Warning: Interface does not match Device. $INTERFACE might be set incorrectly.");
	}

	// Configure the device as best as we can

	switch(device_type) {
	default:
		device_type = DEVICE_TYPE_TUN;

	case DEVICE_TYPE_TUN:
#ifdef TUNSIFHEAD
		{
			const int zero = 0;

			if(ioctl(device_fd, TUNSIFHEAD, &zero, sizeof(zero)) == -1) {
				logger(LOG_ERR, "System call `%s' failed: %s", "ioctl", strerror(errno));
				return false;
			}
		}

#endif
#if defined(TUNSIFMODE) && defined(IFF_BROADCAST) && defined(IFF_MULTICAST)
		{
			const int mode = IFF_BROADCAST | IFF_MULTICAST;
			ioctl(device_fd, TUNSIFMODE, &mode, sizeof(mode));
		}
#endif

		device_info = "Generic BSD tun device";
		break;

	case DEVICE_TYPE_TUNIFHEAD:
#ifdef TUNSIFHEAD
		{
			const int one = 1;

			if(ioctl(device_fd, TUNSIFHEAD, &one, sizeof(one)) == -1) {
				logger(LOG_ERR, "System call `%s' failed: %s", "ioctl", strerror(errno));
				return false;
			}
		}

#endif
#if defined(TUNSIFMODE) && defined(IFF_BROADCAST) && defined(IFF_MULTICAST)
		{
			const int mode = IFF_BROADCAST | IFF_MULTICAST;
			ioctl(device_fd, TUNSIFMODE, &mode, sizeof(mode));
		}
#endif

		device_info = "Generic BSD tun device";
		break;

	case DEVICE_TYPE_TAP:
		if(routing_mode == RMODE_ROUTER) {
			overwrite_mac = true;
		}

		device_info = "Generic BSD tap device";
#ifdef TAPGIFNAME
		{
			struct ifreq ifr;

			if(ioctl(device_fd, TAPGIFNAME, (void *)&ifr) == 0) {
				if(iface) {
					free(iface);
				}

				iface = xstrdup(ifr.ifr_name);
			}
		}

#endif
		break;
#ifdef ENABLE_TUNEMU

	case DEVICE_TYPE_TUNEMU:
		device_info = "BSD tunemu device";
		break;
#endif
	}

#ifdef SIOCGIFADDR

	if(overwrite_mac) {
		ioctl(device_fd, SIOCGIFADDR, mymac.x);
	}

#endif

	logger(LOG_INFO, "%s is a %s", device, device_info);

	return true;
}

static void close_device(void) {
	switch(device_type) {
#ifdef ENABLE_TUNEMU

	case DEVICE_TYPE_TUNEMU:
		tunemu_close(device_fd);
		break;
#endif
#ifdef HAVE_DARWIN

	case DEVICE_TYPE_FETH:
		close_feth();
		break;
#endif

	default:
		close(device_fd);
	}

	free(device);
	free(iface);
}

static bool read_packet(vpn_packet_t *packet) {
	int lenin;

	switch(device_type) {
	case DEVICE_TYPE_TUN:
#ifdef ENABLE_TUNEMU
	case DEVICE_TYPE_TUNEMU:
		if(device_type == DEVICE_TYPE_TUNEMU) {
			lenin = tunemu_read(device_fd, packet->data + 14, MTU - 14);
		} else
#endif
			lenin = read(device_fd, packet->data + 14, MTU - 14);

		if(lenin <= 0) {
			logger(LOG_ERR, "Error while reading from %s %s: %s", device_info,
			       device, strerror(errno));
			return false;
		}

		switch(packet->data[14] >> 4) {
		case 4:
			packet->data[12] = 0x08;
			packet->data[13] = 0x00;
			break;

		case 6:
			packet->data[12] = 0x86;
			packet->data[13] = 0xDD;
			break;

		default:
			ifdebug(TRAFFIC) logger(LOG_ERR,
			                        "Unknown IP version %d while reading packet from %s %s",
			                        packet->data[14] >> 4, device_info, device);
			return false;
		}

		memset(packet->data, 0, 12);
		packet->len = lenin + 14;
		break;

	case DEVICE_TYPE_UTUN:
	case DEVICE_TYPE_TUNIFHEAD: {
		if((lenin = read(device_fd, packet->data + 10, MTU - 10)) <= 0) {
			logger(LOG_ERR, "Error while reading from %s %s: %s", device_info,
			       device, strerror(errno));
			return false;
		}

		switch(packet->data[14] >> 4) {
		case 4:
			packet->data[12] = 0x08;
			packet->data[13] = 0x00;
			break;

		case 6:
			packet->data[12] = 0x86;
			packet->data[13] = 0xDD;
			break;

		default:
			ifdebug(TRAFFIC) logger(LOG_ERR,
			                        "Unknown IP version %d while reading packet from %s %s",
			                        packet->data[14] >> 4, device_info, device);
			return false;
		}

		memset(packet->data, 0, 12);
		packet->len = lenin + 10;
		break;
	}

	case DEVICE_TYPE_TAP:
		if((lenin = read(device_fd, packet->data, MTU)) <= 0) {
			logger(LOG_ERR, "Error while reading from %s %s: %s", device_info,
			       device, strerror(errno));
			return false;
		}

		packet->len = lenin;
		break;

#ifdef HAVE_DARWIN

	case DEVICE_TYPE_FETH:
		if(!read_feth_packet(packet)) {
			return false;
		}

		break;
#endif

	default:
		return false;
	}

	device_total_in += packet->len;

	ifdebug(TRAFFIC) logger(LOG_DEBUG, "Read packet of %d bytes from %s",
	                        packet->len, device_info);

	return true;
}

static bool write_packet(vpn_packet_t *packet) {
	ifdebug(TRAFFIC) logger(LOG_DEBUG, "Writing packet of %d bytes to %s",
	                        packet->len, device_info);

	switch(device_type) {
	case DEVICE_TYPE_TUN:
		if(write(device_fd, packet->data + 14, packet->len - 14) < 0) {
			logger(LOG_ERR, "Error while writing to %s %s: %s", device_info,
			       device, strerror(errno));
			return false;
		}

		break;

	case DEVICE_TYPE_UTUN:
	case DEVICE_TYPE_TUNIFHEAD: {
		int af = (packet->data[12] << 8) + packet->data[13];
		uint32_t type;

		switch(af) {
		case 0x0800:
			type = htonl(AF_INET);
			break;

		case 0x86DD:
			type = htonl(AF_INET6);
			break;

		default:
			ifdebug(TRAFFIC) logger(LOG_ERR,
			                        "Unknown address family %x while writing packet to %s %s",
			                        af, device_info, device);
			return false;
		}

		memcpy(packet->data + 10, &type, sizeof(type));

		if(write(device_fd, packet->data + 10, packet->len - 10) < 0) {
			logger(LOG_ERR, "Can't write to %s %s: %s", device_info, device,
			       strerror(errno));
			return false;
		}

		break;
	}

	case DEVICE_TYPE_TAP:
		if(write(device_fd, packet->data, packet->len) < 0) {
			logger(LOG_ERR, "Error while writing to %s %s: %s", device_info,
			       device, strerror(errno));
			return false;
		}

		break;

#ifdef ENABLE_TUNEMU

	case DEVICE_TYPE_TUNEMU:
		if(tunemu_write(device_fd, packet->data + 14, packet->len - 14) < 0) {
			logger(LOG_ERR, "Error while writing to %s %s: %s", device_info,
			       device, strerror(errno));
			return false;
		}

		break;
#endif

#ifdef HAVE_DARWIN

	case DEVICE_TYPE_FETH:
		if(!write_feth_packet(packet)) {
			return false;
		}

		break;
#endif

	default:
		return false;
	}

	device_total_out += packet->len;

	return true;
}

static void dump_device_stats(void) {
	logger(LOG_DEBUG, "Statistics for %s %s:", device_info, device);
	logger(LOG_DEBUG, " total bytes in:  %10"PRIu64, device_total_in);
	logger(LOG_DEBUG, " total bytes out: %10"PRIu64, device_total_out);
}

const devops_t os_devops = {
	.setup = setup_device,
	.close = close_device,
	.read = read_packet,
	.write = write_packet,
	.dump_stats = dump_device_stats,
};