tinc/src/multicast_device.c

/*
    device.c -- multicast socket
    Copyright (C) 2002-2005 Ivo Timmermans,
                  2002-2013 Guus Sliepen <guus@tinc-vpn.org>

    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 "net.h"
#include "logger.h"
#include "netutl.h"
#include "utils.h"
#include "route.h"
#include "xalloc.h"

static char *device_info;

static struct addrinfo *ai = NULL;
static mac_t ignore_src = {{0}};

static bool setup_device(void) {
	char *host = NULL;
	char *port;
	char *space;
	int ttl = 1;

	device_info = "multicast socket";

	get_config_string(lookup_config(config_tree, "Interface"), &iface);

	if(!get_config_string(lookup_config(config_tree, "Device"), &device)) {
		logger(DEBUG_ALWAYS, LOG_ERR, "Device variable required for %s", device_info);
		goto error;
	}

	host = xstrdup(device);
	space = strchr(host, ' ');
	if(!space) {
		logger(DEBUG_ALWAYS, LOG_ERR, "Port number required for %s", device_info);
		goto error;
	}

	*space++ = 0;
	port = space;
	space = strchr(port, ' ');

	if(space) {
		*space++ = 0;
		ttl = atoi(space);
	}

	ai = str2addrinfo(host, port, SOCK_DGRAM);
	if(!ai)
		goto error;

	device_fd = socket(ai->ai_family, SOCK_DGRAM, IPPROTO_UDP);
	if(device_fd < 0) {
		logger(DEBUG_ALWAYS, LOG_ERR, "Creating socket failed: %s", sockstrerror(sockerrno));
		goto error;
	}

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

	static const int one = 1;
	setsockopt(device_fd, SOL_SOCKET, SO_REUSEADDR, (void *)&one, sizeof one);

	if(bind(device_fd, ai->ai_addr, ai->ai_addrlen)) {
		logger(DEBUG_ALWAYS, LOG_ERR, "Can't bind to %s %s: %s", host, port, sockstrerror(sockerrno));
		goto error;
	}

	switch(ai->ai_family) {
#ifdef IP_ADD_MEMBERSHIP
		case AF_INET: {
			struct ip_mreq mreq;
			struct sockaddr_in in;
			memcpy(&in, ai->ai_addr, sizeof in);
			mreq.imr_multiaddr.s_addr = in.sin_addr.s_addr;
			mreq.imr_interface.s_addr = htonl(INADDR_ANY);
			if(setsockopt(device_fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void *)&mreq, sizeof mreq)) {
				logger(DEBUG_ALWAYS, LOG_ERR, "Cannot join multicast group %s %s: %s", host, port, sockstrerror(sockerrno));
				goto error;
			}
#ifdef IP_MULTICAST_LOOP
			setsockopt(device_fd, IPPROTO_IP, IP_MULTICAST_LOOP, (const void *)&one, sizeof one);
#endif
#ifdef IP_MULTICAST_TTL
			setsockopt(device_fd, IPPROTO_IP, IP_MULTICAST_TTL, (void *)&ttl, sizeof ttl);
#endif
		} break;
#endif

#ifdef IPV6_JOIN_GROUP
		case AF_INET6: {
			struct ipv6_mreq mreq;
			struct sockaddr_in6 in6;
			memcpy(&in6, ai->ai_addr, sizeof in6);
			memcpy(&mreq.ipv6mr_multiaddr, &in6.sin6_addr, sizeof mreq.ipv6mr_multiaddr);
			mreq.ipv6mr_interface = in6.sin6_scope_id;
			if(setsockopt(device_fd, IPPROTO_IPV6, IPV6_JOIN_GROUP, (void *)&mreq, sizeof mreq)) {
				logger(DEBUG_ALWAYS, LOG_ERR, "Cannot join multicast group %s %s: %s", host, port, sockstrerror(sockerrno));
				goto error;
			}
#ifdef IPV6_MULTICAST_LOOP
			setsockopt(device_fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, (const void *)&one, sizeof one);
#endif
#ifdef IPV6_MULTICAST_HOPS
			setsockopt(device_fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, (void *)&ttl, sizeof ttl);
#endif
		} break;
#endif

		default:
			logger(DEBUG_ALWAYS, LOG_ERR, "Multicast for address family %x unsupported", ai->ai_family);
			goto error;
	}

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

	return true;

error:
	if(device_fd >= 0)
		closesocket(device_fd);
	if(ai)
		freeaddrinfo(ai);
	free(host);

	return false;
}

static void close_device(void) {
	close(device_fd); device_fd = -1;

	free(device); device = NULL;
	free(iface); iface = NULL;

	if(ai) {
		freeaddrinfo(ai); ai = NULL;
	}
	device_info = NULL;
}

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

	if((lenin = recv(device_fd, (void *)packet->data, MTU, 0)) <= 0) {
		logger(DEBUG_ALWAYS, LOG_ERR, "Error while reading from %s %s: %s", device_info,
			   device, sockstrerror(sockerrno));
		return false;
	}

	if(!memcmp(&ignore_src, packet->data + 6, sizeof ignore_src)) {
		logger(DEBUG_SCARY_THINGS, LOG_DEBUG, "Ignoring loopback packet of %d bytes from %s", lenin, device_info);
		return false;
	}

	packet->len = lenin;

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

	return true;
}

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

	if(sendto(device_fd, (void *)packet->data, packet->len, 0, ai->ai_addr, ai->ai_addrlen) < 0) {
		logger(DEBUG_ALWAYS, LOG_ERR, "Can't write to %s %s: %s", device_info, device,
			   sockstrerror(sockerrno));
		return false;
	}

	memcpy(&ignore_src, packet->data + 6, sizeof ignore_src);

	return true;
}

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