openbsd-compat/port-tun.c

/*
 * Copyright (c) 2005 Reyk Floeter <reyk@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "includes.h"

#include "log.h"
#include "misc.h"
#include "bufaux.h"

/*
 * This is the portable version of the SSH tunnel forwarding, it
 * uses some preprocessor definitions for various platform-specific
 * settings.
 *
 * SSH_TUN_LINUX	Use the (newer) Linux tun/tap device
 * SSH_TUN_COMPAT_AF	Translate the OpenBSD address family
 * SSH_TUN_PREPEND_AF	Prepend/remove the address family
 */

/*
 * System-specific tunnel open function
 */

#if defined(SSH_TUN_LINUX)
#include <linux/if_tun.h>

int
sys_tun_open(int tun, int mode)
{
	struct ifreq ifr;
	int fd = -1;
	const char *name = NULL;

	if ((fd = open("/dev/net/tun", O_RDWR)) == -1) {
		debug("%s: failed to open tunnel control interface: %s",
		    __func__, strerror(errno));
		return (-1);
	}

	bzero(&ifr, sizeof(ifr));	

	if (mode == SSH_TUNMODE_ETHERNET) {
		ifr.ifr_flags = IFF_TAP;
		name = "tap%d";
	} else {
		ifr.ifr_flags = IFF_TUN;
		name = "tun%d";
	}
	ifr.ifr_flags |= IFF_NO_PI;

	if (tun != SSH_TUNID_ANY) {
		if (tun > SSH_TUNID_MAX) {
			debug("%s: invalid tunnel id %x: %s", __func__,
			    tun, strerror(errno));
			goto failed;
		}
		snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), name, tun);
	}

	if (ioctl(fd, TUNSETIFF, &ifr) == -1) {
		debug("%s: failed to configure tunnel (mode %d): %s", __func__,
		    mode, strerror(errno));
		goto failed;
	}

	if (tun == SSH_TUNID_ANY)
		debug("%s: tunnel mode %d fd %d", __func__, mode, fd);
	else
		debug("%s: %s mode %d fd %d", __func__, ifr.ifr_name, mode, fd);

	return (fd);

 failed:
	close(fd);
	return (-1);
}
#endif /* SSH_TUN_LINUX */

/*
 * System-specific channel filters
 */

#if defined(SSH_TUN_FILTER)
#define OPENBSD_AF_INET		2
#define OPENBSD_AF_INET6	24

int
sys_tun_infilter(struct Channel *c, char *buf, int len)
{
#if defined(SSH_TUN_PREPEND_AF)
	char rbuf[CHAN_RBUF];
#endif
	u_int32_t *af;
	char *ptr = buf;

#if defined(SSH_TUN_PREPEND_AF)
	if (len > (int)(sizeof(rbuf) - sizeof(*af)))
		return (-1);
	ptr = (char *)&rbuf[0];
	bcopy(buf, ptr + sizeof(u_int32_t), len);
	len += sizeof(u_int32_t);
#endif

#if defined(SSH_TUN_COMPAT_AF)
	if (len < (int)sizeof(u_int32_t))
		return (-1);

	af = (u_int32_t *)ptr;
	if (*af == htonl(AF_INET6))
		*af = htonl(OPENBSD_AF_INET6);
	else
		*af = htonl(OPENBSD_AF_INET);
#endif
	buffer_put_string(&c->input, ptr, len);
	return (0);
}

u_char *
sys_tun_outfilter(struct Channel *c, u_char **data, u_int *dlen)
{
	u_char *buf;
	u_int32_t *af;

	*data = buffer_get_string(&c->output, dlen);
	if (*dlen < sizeof(*af))
		return (NULL);
	buf = *data;

#if defined(SSH_TUN_PREPEND_AF)
	*dlen -= sizeof(u_int32_t);
	buf = *data + sizeof(u_int32_t);
#elif defined(SSH_TUN_COMPAT_AF)
	af = ntohl(*(u_int32_t *)buf);
	if (*af == OPENBSD_AF_INET6)
		*af = htonl(AF_INET6);
	else
		*af = htonl(AF_INET);
#endif

	return (buf);
}
#endif /* SSH_TUN_FILTER */