bcastfwd/bcastfwd.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <time.h>

#include "configfile.h"
#include "event.h"
#include "list.h"
#include "logging.h"
#include "sockaddr.h"

struct host_entry {
	struct list_head	list;
	struct sockaddr_in	address;
	int			flags;
};

#define HOST_ACTIVE		0x0001
#define HOST_LOCAL		0x0010
#define HOST_REMOTE		0x0020

static LIST_HEAD(host_list);
static int raw_sock;
static int listen_sock;

static struct event_fd *listen_event;
static struct event_timeout *local_timeout;
static struct event_timeout *remote_timeout;

static int add_host_cb(const char *parameter, void *privdata)
{
	struct host_entry *entry = malloc(sizeof(struct host_entry));
	if (entry == NULL) {
		log_print(LOG_WARN, "add_host_cb(): out of memory");
		return -1;
	}

	if (parse_sockaddr(parameter, &entry->address)) {
		log_print(LOG_WARN, "add_host_cb(): invalid host: '%s'", parameter);
		free(entry);
		return -1;
	}

	entry->flags = (int)privdata | HOST_ACTIVE;

	log_print(LOG_INFO, "Forwarding to %s (%s)", get_sockaddr_buf(&entry->address), (entry->flags == HOST_LOCAL) ? "local" : "remote");
	list_add_tail(&entry->list, &host_list);
	return 0;
}

static int check_local_host_cb(void *privdata)
{
	struct host_entry *entry;
	list_for_each_entry(entry, &host_list, list) {
		if (!(entry->flags & HOST_LOCAL))
			continue;

		int sock = socket(AF_INET, SOCK_DGRAM, 0);
		if (sock < 0) {
			log_print(LOG_WARN, "check_local_host_cb(): socket()");
			continue;
		}

		if (bind(sock,(struct sockaddr *)&entry->address, sizeof(struct sockaddr_in)) < 0) {
			/* port in use, host seems to be active */
			if (!(entry->flags & HOST_ACTIVE)) {
				log_print(LOG_INFO, "Host active: %s", get_sockaddr_buf(&entry->address));
				entry->flags |= HOST_ACTIVE;
			}

		} else {
			/* port not in use, host can not be active */
			if (entry->flags & HOST_ACTIVE) {
				log_print(LOG_INFO, "Host not active: %s", get_sockaddr_buf(&entry->address));
				entry->flags &= ~(HOST_ACTIVE);
			}
		}

		close(sock);
	}

	return 0;
}

#if 0
static int check_remote_host_cb(void *privdata)
{
	// TODO: don't know how to check
	return 0;
}
#endif

static int send_raw_udp(int fd, struct sockaddr_in *src, struct sockaddr_in *dst, const char *buf, int offset, int size)
{
	if (offset < sizeof(struct iphdr) + sizeof(struct udphdr))
		return -1;

	struct iphdr *ip = (struct iphdr *)buf;
	struct udphdr *udp = (struct udphdr *)(buf + sizeof(struct iphdr));

	ip->version = 4;	/* IPv4 */
	ip->ihl = sizeof(struct iphdr) / sizeof(int);
	ip->tos = 0;
	ip->id = 0;
	ip->frag_off = 0;
	ip->ttl = 64;
	ip->protocol = IPPROTO_UDP;
	ip->check = 0;		/* computed by kernel */
	ip->saddr = src->sin_addr.s_addr;
	ip->daddr = dst->sin_addr.s_addr;

	int packetsize = sizeof(struct iphdr) + sizeof(struct udphdr) + size;
	ip->tot_len = htons(packetsize);

	udp->source = src->sin_port;
	udp->dest = dst->sin_port;
	udp->check = 0;		/* ignore */
	udp->len = htons(sizeof(struct udphdr) + size);

	if (sendto(fd, buf, packetsize, 0, (struct sockaddr *)dst, sizeof(struct sockaddr)) < 0) {
		log_print(LOG_WARN, "send_raw_udp(): sendto()");
		return -1;
	}

	return 0;
}

static int listen_cb(int fd, void *privdata)
{
	struct sockaddr_in src_addr;
	char buf[512];

	socklen_t i = sizeof(src_addr);
	int offset = sizeof(struct iphdr) + sizeof(struct udphdr);

	int len = recvfrom(fd, buf + offset, sizeof(buf) - offset, 0, (struct sockaddr *)&src_addr, &i);
	if (len <= 0) {
		log_print(LOG_WARN, "listen_cb(): recvfrom()");
		return -1;
	}

	struct host_entry *entry;
	list_for_each_entry(entry, &host_list, list) {
		if (!(entry->flags & HOST_ACTIVE))
			continue;

		send_raw_udp(raw_sock, &src_addr, &entry->address, buf, offset, len);
	}

	return 0;
}

int bcast_close(void)
{
	if (remote_timeout != NULL) {
		event_remove_timeout(remote_timeout);
		remote_timeout = NULL;
	}

	if (local_timeout != NULL) {
		event_remove_timeout(local_timeout);
		local_timeout = NULL;
	}

	struct host_entry *entry, *tmp;
	list_for_each_entry_safe(entry, tmp, &host_list, list) {
		list_del(&entry->list);
		free(entry);
	}

	event_remove_fd(listen_event);
	close(listen_sock);
	close(raw_sock);

	return 0;
}

int bcast_init(void)
{
	raw_sock = socket(PF_INET, SOCK_RAW, IPPROTO_UDP);
	if (raw_sock < 0) {
		log_print(LOG_ERROR, "bcast_init(): socket(raw)");
		return -1;
	}

	int i = 1;
	if (setsockopt(raw_sock, IPPROTO_IP, IP_HDRINCL, &i, sizeof(i)) < 0 ) {
		log_print(LOG_ERROR, "bcast_init(): setsockopt(IP_HDRINCL)");
		close(raw_sock);
		return -1;
	}

	int listen_port = 0;
	if (config_get_int("global", "listen", &listen_port, 0)) {
		log_print(LOG_ERROR, "bcast_init(): Invalid listen port: %d", listen_port);
		close(raw_sock);
		return -1;
	}

	struct sockaddr_in listen_addr;
	listen_addr.sin_family = AF_INET,
	listen_addr.sin_addr.s_addr = INADDR_ANY;
	listen_addr.sin_port = htons(listen_port);

	listen_sock = socket(AF_INET, SOCK_DGRAM, 0);
	if (listen_sock < 0) {
		log_print(LOG_ERROR, "bcast_init(): socket(listen)");
		close(raw_sock);
		return -1;
	}

	if (bind(listen_sock, (struct sockaddr *)&listen_addr, sizeof(struct sockaddr_in)) < 0) {
		log_print(LOG_ERROR, "bcast_init(): bind()");
		close(listen_sock);
		close(raw_sock);
		return -1;
	}

	log_print(LOG_INFO, "Listening on %s", get_sockaddr_buf(&listen_addr));
	listen_event = event_add_readfd(NULL, listen_sock, listen_cb, NULL);

	int localcount, remotecount;
	localcount = config_get_strings("local", "host", add_host_cb, (void *)HOST_LOCAL);
	remotecount = config_get_strings("remote", "host", add_host_cb, (void *)HOST_REMOTE);

	if ((localcount + remotecount) == 0) {
		log_print(LOG_ERROR, "bcast_init(): no hosts given");
		event_remove_fd(listen_event);
		close(listen_sock);
		close(raw_sock);
		return -1;
	}

	int check_interval = 0;
	struct timeval tv;
	tv.tv_usec = 0;

	if (localcount > 0) {
		config_get_int("local", "check_interval", &check_interval, 10);
		tv.tv_sec = check_interval;
		local_timeout = event_add_timeout(&tv, check_local_host_cb, NULL);
	}
#if 0
	if (remotecount > 0) {
		config_get_int("remote", "check_interval", &check_interval, 60);
		tv.tv_sec = check_interval;
		remote_timeout = event_add_timeout(&tv, check_remote_host_cb, NULL);
	}
#endif
	return 0;
}