Initial commit.

5 files changed, 737 insertions, 0 deletions

diff --git a/.hgignore b/.hgignore
new file mode 100644
index 0000000..90264e6
--- /dev/null
+++ b/.hgignore
@@ -0,0 +1,5 @@
+syntax: glob

+

+*.o

+mdns-repeater

+ 

diff --git a/LICENSE.txt b/LICENSE.txt
new file mode 100644
index 0000000..7d5393a
--- /dev/null
+++ b/LICENSE.txt
@@ -0,0 +1,278 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
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+
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+later version", you have the option of following the terms and conditions
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+Software Foundation.  If the Program does not specify a version number of
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+                            NO WARRANTY
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+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
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diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..3fc13c8
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,15 @@
+# Makefile for mdns-repeater
+
+CFLAGS=-Wall -Os
+LDFLAGS=-s
+
+.PHONY: all clean
+
+all: mdns-repeater
+
+mdns-repeater: mdns-repeater.o
+
+clean:
+	-$(RM) *.o
+	-$(RM) mdns-repeater
+
diff --git a/README.txt b/README.txt
new file mode 100644
index 0000000..b92360e
--- /dev/null
+++ b/README.txt
@@ -0,0 +1,49 @@
+mdns-repeater
+==============
+mdns-repeater is a Multicast DNS repeater for Linux. Multicast DNS uses the 
+224.0.0.51 address, which is "administratively scoped" and does not 
+leave the subnet.
+
+This program re-broadcast mDNS packets from one interface to other interfaces.
+It was written primarily to be run on my Linksys WRT54G which runs dd-wrt,
+since my wireless network is on a different subnet from my wired network and 
+I would like my zeroconf devices to work properly across the two subnets.
+
+Since the mDNS protocol sends the AA records in the packet itself, the 
+repeater does not need to forge the source address. Instead, the source 
+address is of the interface that repeats the packet.
+
+
+USAGE
+-----
+mdns-repeater only requires the interface names and it will do the rest.
+For example, the dd-wrt standard installation defines br0 for the wireless 
+interface and vlan1 as the WAN interface, I would use:
+
+    mdns-repeater br0 vlan1
+
+You can also specify the -f flag for debugging, which prints packets as they 
+are received.
+
+You are free to modify the code to repeat whatever traffic you require, as
+long as you abide by the software license.
+
+
+LICENSE
+--------
+Copyright (C) 2010 Darell Tan
+
+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.
+
diff --git a/mdns-repeater.c b/mdns-repeater.c
new file mode 100644
index 0000000..f06720b
--- /dev/null
+++ b/mdns-repeater.c
@@ -0,0 +1,390 @@
+/*
+ * mdns-repeater.c - mDNS repeater daemon
+ * Copyright (C) 2010 Darell Tan
+ * 
+ * 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 <sys/socket.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <syslog.h>
+#include <unistd.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <net/if.h>
+
+#define PACKAGE "mdns-repeater"
+#define MDNS_ADDR "224.0.0.251"
+#define MDNS_PORT 5353
+
+
+struct if_sock {
+	const char *ifname;		/* interface name  */
+	int sockfd;				/* socket filedesc */
+	struct in_addr addr;	/* interface addr  */
+	struct in_addr mask;	/* interface mask  */
+	struct in_addr net;		/* interface network (computed) */
+};
+
+int server_sockfd = -1;
+
+int num_socks = 0;
+struct if_sock socks[5];
+
+#define PACKET_SIZE 65536
+void *pkt_data = NULL;
+
+int foreground = 0;
+int shutdown_flag = 0;
+
+
+void log_message(int loglevel, char *fmt_str, ...) {
+	va_list ap;
+	char buf[2048];
+
+	va_start(ap, fmt_str);
+	vsnprintf(buf, 2047, fmt_str, ap);
+	va_end(ap);
+	buf[2047] = 0;
+
+	if (foreground) {
+		fprintf(stderr, "%s: %s\n", PACKAGE, buf);
+	} else {
+		syslog(loglevel, "%s", buf);
+	}
+}
+
+static int create_recv_sock() {
+	int sd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sd < 0) {
+		perror("socket()");
+		return sd;
+	}
+
+	int r = -1;
+
+	int on = 1;
+	if ((r = setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on))) < 0) {
+		perror("setsockopt(SO_REUSEADDR)");
+		return r;
+	}
+
+	/* bind to an address */
+	struct sockaddr_in serveraddr;
+	memset(&serveraddr, 0, sizeof(serveraddr));
+	serveraddr.sin_family = AF_INET;
+	serveraddr.sin_port = htons(MDNS_PORT);
+	serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);	/* receive multicast */
+	if ((r = bind(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr))) < 0) {
+		perror("bind()");
+	}
+
+	// enable loopback in case someone else needs the data
+	if ((r = setsockopt(sd, IPPROTO_IP, IP_MULTICAST_LOOP, &on, sizeof(on))) < 0) {
+		perror("setsockopt(IP_MULTICAST_LOOP)");
+		return r;
+	}
+
+#ifdef IP_PKTINFO
+	if ((r = setsockopt(sd, SOL_IP, IP_PKTINFO, &on, sizeof(on))) < 0) {
+		perror("setsockopt(IP_PKTINFO)");
+		return r;
+	}
+#endif
+
+	return sd;
+}
+
+static int create_send_sock(int recv_sockfd, const char *ifname, struct if_sock *sockdata) {
+	int sd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sd < 0) {
+		perror("socket()");
+		return sd;
+	}
+
+	sockdata->ifname = ifname;
+	sockdata->sockfd = sd;
+
+	int r = -1;
+
+	struct ifreq ifr;
+	memset(&ifr, 0, sizeof(ifr));
+	strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
+	struct in_addr *if_addr = &((struct sockaddr_in *) &ifr.ifr_addr)->sin_addr;
+
+#ifdef SO_BINDTODEVICE
+	if ((r = setsockopt(sd, SOL_SOCKET, SO_BINDTODEVICE, &ifr, sizeof(struct ifreq))) < 0) {
+		perror("setsockopt(SO_BINDTODEVICE)");
+		return r;
+	}
+#endif
+
+	// get netmask
+	if (ioctl(sd, SIOCGIFNETMASK, &ifr) == 0) {
+		memcpy(&sockdata->mask, if_addr, sizeof(struct in_addr));
+	}
+
+	// .. and interface address
+	if (ioctl(sd, SIOCGIFADDR, &ifr) == 0) {
+		memcpy(&sockdata->addr, if_addr, sizeof(struct in_addr));
+	}
+
+	// compute network (address & mask)
+	sockdata->net.s_addr = sockdata->addr.s_addr & sockdata->mask.s_addr;
+
+	int on = 1;
+	if ((r = setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on))) < 0) {
+		perror("setsockopt(SO_REUSEADDR)");
+		return r;
+	}
+
+	// bind to an address
+	struct sockaddr_in serveraddr;
+	memset(&serveraddr, 0, sizeof(serveraddr));
+	serveraddr.sin_family = AF_INET;
+	serveraddr.sin_port = htons(MDNS_PORT);
+	serveraddr.sin_addr.s_addr = if_addr->s_addr;
+	if ((r = bind(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr))) < 0) {
+		perror("bind()");
+	}
+
+	// add membership to receiving socket
+	struct ip_mreq mreq;
+	memset(&mreq, 0, sizeof(struct ip_mreq));
+	mreq.imr_interface.s_addr = if_addr->s_addr;
+	mreq.imr_multiaddr.s_addr = inet_addr(MDNS_ADDR);
+	if ((r = setsockopt(recv_sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq))) < 0) {
+		perror("setsockopt(IP_ADD_MEMBERSHIP)");
+		return r;
+	}
+
+	// enable loopback in case someone else needs the data
+	if ((r = setsockopt(sd, IPPROTO_IP, IP_MULTICAST_LOOP, &on, sizeof(on))) < 0) {
+		perror("setsockopt(IP_MULTICAST_LOOP)");
+		return r;
+	}
+
+	char *addr_str = strdup(inet_ntoa(sockdata->addr));
+	char *mask_str = strdup(inet_ntoa(sockdata->mask));
+	char *net_str  = strdup(inet_ntoa(sockdata->net));
+	log_message(LOG_INFO, "dev %s addr %s mask %s net %s", ifr.ifr_name, addr_str, mask_str, net_str);
+	free(addr_str);
+	free(mask_str);
+	free(net_str);
+
+	return sd;
+}
+
+static ssize_t send_packet(int fd, const void *data, size_t len) {
+	static struct sockaddr_in toaddr;
+	if (toaddr.sin_family != AF_INET) {
+		memset(&toaddr, 0, sizeof(struct sockaddr_in));
+		toaddr.sin_family = AF_INET;
+		toaddr.sin_port = htons(MDNS_PORT);
+		toaddr.sin_addr.s_addr = inet_addr(MDNS_ADDR);
+	}
+
+	return sendto(fd, data, len, 0, (struct sockaddr *) &toaddr, sizeof(struct sockaddr_in));
+}
+
+static void mdns_repeater_shutdown(int sig) {
+	shutdown_flag = 1;
+}
+
+static void daemonize() {
+	pid_t pid = fork();
+	if (pid < 0) {
+		perror("fork()");
+		exit(1);
+	}
+
+	// exit parent process
+	if (pid > 0)
+		exit(0);
+
+	// signals
+	signal(SIGCHLD, SIG_IGN);
+	signal(SIGHUP, SIG_IGN);
+	signal(SIGTERM, mdns_repeater_shutdown);
+
+	setsid();
+	umask(0027);
+	chdir("/");
+
+	int i = getdtablesize();
+	while (i--)
+		close(i);
+
+	i = open("/dev/null", O_RDWR);
+	dup(i);
+	dup(i);
+}
+
+static void show_help(const char *progname) {
+	fprintf(stderr, "mDNS repeater\n");
+	fprintf(stderr, "usage: %s [ -f ] <ifdev> ...\n", progname);
+	fprintf(stderr, "\n"
+					"<ifdev> specifies an interface like \"eth0\"\n"
+					"packets received on an interface is repeated across all other specified interfaces\n"
+					"maximum number of interfaces is 5\n"
+					"\n"
+					" flags:\n"
+					"	-f	runs in foreground for debugging\n"
+					"	-h	shows this help\n"
+					"\n"
+		);
+}
+
+static int parse_opts(int argc, char *argv[]) {
+	int c;
+	int help = 0;
+	while ((c = getopt(argc, argv, "hf")) != -1) {
+		switch (c) {
+			case 'h': help = 1; break;
+			case 'f': foreground = 1; break;
+			default:
+				fprintf(stderr, "unknown option %c\n", optopt);
+				exit(2);
+		}
+	}
+
+	if (help) {
+		show_help(argv[0]);
+		exit(0);
+	}
+
+	return optind;
+}
+
+int main(int argc, char *argv[]) {
+	fd_set sockfd_set;
+
+	parse_opts(argc, argv);
+
+	if ((argc - optind) <= 1) {
+		show_help(argv[0]);
+		fprintf(stderr, "error: at least 2 interfaces must be specified\n");
+		exit(2);
+	}
+
+	openlog(PACKAGE, LOG_PID | LOG_CONS, LOG_DAEMON);
+
+	// create receiving socket
+	server_sockfd = create_recv_sock();
+	if (server_sockfd < 0) {
+		log_message(LOG_ERR, "unable to create server socket");
+		return 1;
+	}
+
+	// create sending sockets
+	int i;
+	for (i = optind; i < argc; i++) {
+		int sockfd = create_send_sock(server_sockfd, argv[i], &socks[num_socks]);
+		if (sockfd < 0) {
+			log_message(LOG_ERR, "unable to create socket for interface %s", argv[i]);
+			return 1;
+		}
+		num_socks++;
+	}
+
+	pkt_data = malloc(PACKET_SIZE);
+	if (pkt_data == NULL) {
+		log_message(LOG_ERR, "cannot malloc() packet buffer");
+		return 1;
+	}
+
+	if (! foreground)
+		daemonize();
+
+	while (! shutdown_flag) {
+		struct timeval tv = {
+			.tv_sec = 10,
+			.tv_usec = 0,
+		};
+
+		FD_ZERO(&sockfd_set);
+		FD_SET(server_sockfd, &sockfd_set);
+		int numfd = select(server_sockfd + 1, &sockfd_set, NULL, NULL, &tv);
+		if (numfd == 0)
+			continue;
+
+		if (FD_ISSET(server_sockfd, &sockfd_set)) {
+			struct sockaddr_in fromaddr;
+			socklen_t sockaddr_size = sizeof(struct sockaddr_in);
+
+			ssize_t recvsize = recvfrom(server_sockfd, pkt_data, PACKET_SIZE, 0, 
+				(struct sockaddr *) &fromaddr, &sockaddr_size);
+			if (recvsize < 0) {
+				perror("recv()");
+			}
+
+			int j;
+			char self_generated_packet = 0;
+			for (j = 0; j < num_socks; j++) {
+				// check for loopback
+				if (fromaddr.sin_addr.s_addr == socks[j].addr.s_addr) {
+					self_generated_packet = 1;
+					break;
+				}
+			}
+
+			if (self_generated_packet)
+				continue;
+
+			if (foreground)
+				printf("data from=%s size=%ld\n", inet_ntoa(fromaddr.sin_addr), recvsize);
+
+			for (j = 0; j < num_socks; j++) {
+				// do not repeat packet back to the same network from which it originated
+				if ((fromaddr.sin_addr.s_addr & socks[j].mask.s_addr) == socks[j].net.s_addr)
+					continue;
+
+				if (foreground)
+					printf("repeating data to %s\n", socks[j].ifname);
+
+				// repeat data
+				ssize_t sentsize = send_packet(socks[j].sockfd, pkt_data, (size_t) recvsize);
+				if (sentsize != recvsize) {
+					if (sentsize < 0)
+						perror("send()");
+					else
+						log_message(LOG_ERR, "send_packet size differs: sent=%ld actual=%ld",
+							recvsize, sentsize);
+				}
+			}
+		}
+	}
+
+	log_message(LOG_INFO, "shutting down...");
+
+	if (pkt_data != NULL) 
+		free(pkt_data);
+
+	if (server_sockfd >= 0)
+		close(server_sockfd);
+
+	for (i = 0; i < num_socks; i++) 
+		close(socks[i].sockfd);
+
+	return 0;
+}