From 244ad56cf6714daba50c61a10201a60b77ae74cb Mon Sep 17 00:00:00 2001 From: Darell Tan Date: Sun, 2 Jan 2011 02:05:01 +0800 Subject: Initial commit. --- .hgignore | 5 + LICENSE.txt | 278 ++++++++++++++++++++++++++++++++++++++++ Makefile | 15 +++ README.txt | 49 +++++++ mdns-repeater.c | 390 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 737 insertions(+) create mode 100644 .hgignore create mode 100644 LICENSE.txt create mode 100644 Makefile create mode 100644 README.txt create mode 100644 mdns-repeater.c 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 + of this license document, but changing it is not allowed. + + Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. 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IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING +WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR +REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, +INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING +OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED +TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY +YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER +PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE +POSSIBILITY OF SUCH DAMAGES. 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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 ] ...\n", progname); + fprintf(stderr, "\n" + " 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; +} -- cgit v1.2.3