5 #include <sys/socket.h>
6 #include <netinet/in.h>
10 #include <linux/if_tun.h>
12 #include <sys/ioctl.h>
18 static void usage(FILE *out)
20 fprintf(out, "usage: mctap [-hd] [-D TAPNAME] MCASTGROUP PORT\n");
23 static __attribute__ ((unused)) char *formataddress(struct sockaddr *arg, socklen_t arglen)
25 struct sockaddr_in *ipv4;
26 struct sockaddr_in6 *ipv6;
27 static char *ret = NULL;
33 switch(arg->sa_family)
36 ret = sstrdup("Unix socket");
39 ipv4 = (struct sockaddr_in *)arg;
40 if(inet_ntop(AF_INET, &ipv4->sin_addr, buf, sizeof(buf)) == NULL)
42 ret = sprintf2("%s:%i", buf, (int)ntohs(ipv4->sin_port));
45 ipv6 = (struct sockaddr_in6 *)arg;
46 if(inet_ntop(AF_INET6, &ipv6->sin6_addr, buf, sizeof(buf)) == NULL)
48 ret = sprintf2("[%s]:%i", buf, (int)ntohs(ipv6->sin6_port));
57 static int mkmcastsk4(struct in_addr group, int port)
61 struct sockaddr_in nm;
64 fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
66 if(setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &soval, sizeof(soval)))
68 memset(&nm, 0, sizeof(nm));
69 nm.sin_family = AF_INET;
70 nm.sin_port = htons(port);
71 if(bind(fd, (struct sockaddr *)&nm, sizeof(nm)))
73 memset(&mreq, 0, sizeof(mreq));
74 mreq.imr_multiaddr = group;
75 if(setsockopt(fd, SOL_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)))
78 if(setsockopt(fd, SOL_IP, IP_MULTICAST_LOOP, &soval, sizeof(soval)))
83 static __attribute__ ((unused)) void test(int fd)
92 ret = poll(&pfd, 1, -1);
94 fprintf(stderr, "mctap: poll: %s\n", strerror(errno));
98 ret = read(fd, buf, sizeof(buf));
100 fprintf(stderr, "mctap: read: %s\n", strerror(errno));
103 for(i = 0; i < ret; i++) {
104 printf("%02x ", (unsigned char)buf[i]);
113 static void bridge(int sock, int tap, struct sockaddr *dst, socklen_t dstlen)
117 struct pollfd pfds[2];
120 fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_NONBLOCK);
121 fcntl(tap, F_SETFL, fcntl(tap, F_GETFL) | O_NONBLOCK);
124 pfds[0].events = POLLIN;
126 pfds[1].events = POLLIN;
127 ret = poll(pfds, 2, -1);
130 syslog(LOG_ERR, "mctap: poll: %s", strerror(errno));
135 if(pfds[0].revents) {
136 ret = read(sock, buf, sizeof(buf));
138 if((errno != EINTR) && (errno != EAGAIN)) {
139 syslog(LOG_ERR, "mctap: mcast packet: %s", strerror(errno));
143 if(sizeof(buf) - ret < sizeof(pi)) {
146 memmove(buf + sizeof(pi), buf, ret);
149 memcpy(buf, &pi, sizeof(pi));
150 write(tap, buf, sizeof(pi) + ret);
154 if(pfds[1].revents) {
155 ret = read(tap, buf, sizeof(buf));
157 if((errno != EINTR) && (errno != EAGAIN)) {
158 syslog(LOG_ERR, "mctap: mcast packet: %s", strerror(errno));
162 if(ret < sizeof(pi)) {
165 memcpy(&pi, buf, sizeof(pi));
166 if(pi.flags & TUN_PKT_STRIP) {
169 sendto(sock, buf + sizeof(pi), ret - sizeof(pi), 0, dst, dstlen);
177 static int maketap(char *name)
182 if((fd = open("/dev/net/tun", O_RDWR)) < 0)
184 memset(&rb, 0, sizeof(rb));
185 rb.ifr_flags = IFF_TAP;
186 strncpy(rb.ifr_name, name, IFNAMSIZ);
187 if(ioctl(fd, TUNSETIFF, &rb))
192 int main(int argc, char **argv)
196 struct in_addr group;
200 struct sockaddr_in dst;
204 while((c = getopt(argc, argv, "hD:d")) >= 0) {
220 if(argc - optind < 2) {
224 if(!inet_aton(argv[optind], &group)) {
225 fprintf(stderr, "mctap: invalid group address: %s\n", argv[optind]);
228 port = atoi(argv[optind + 1]);
229 if((sock = mkmcastsk4(group, port)) < 0) {
230 fprintf(stderr, "mctap: could not create multicast socket: %s\n", strerror(errno));
233 if((tap = maketap(tapname)) < 0) {
234 fprintf(stderr, "mctap: could not create TAP device: %s\n", strerror(errno));
237 openlog(sprintf2("mctap-%s", tapname), LOG_PID, LOG_DAEMON);
242 memset(&dst, 0, sizeof(dst));
243 dst.sin_family = AF_INET;
244 dst.sin_addr = group;
245 dst.sin_port = htons(port);
246 bridge(sock, tap, (struct sockaddr *)&dst, sizeof(dst));