5 #include <sys/socket.h>
6 #include <netinet/in.h>
10 #include <linux/if_tun.h>
12 #include <sys/ioctl.h>
17 static void usage(FILE *out)
19 fprintf(out, "usage: mctap [-h] [-D TAPNAME] MCASTGROUP PORT\n");
22 static __attribute__ ((unused)) char *formataddress(struct sockaddr *arg, socklen_t arglen)
24 struct sockaddr_in *ipv4;
25 struct sockaddr_in6 *ipv6;
26 static char *ret = NULL;
32 switch(arg->sa_family)
35 ret = sstrdup("Unix socket");
38 ipv4 = (struct sockaddr_in *)arg;
39 if(inet_ntop(AF_INET, &ipv4->sin_addr, buf, sizeof(buf)) == NULL)
41 ret = sprintf2("%s:%i", buf, (int)ntohs(ipv4->sin_port));
44 ipv6 = (struct sockaddr_in6 *)arg;
45 if(inet_ntop(AF_INET6, &ipv6->sin6_addr, buf, sizeof(buf)) == NULL)
47 ret = sprintf2("[%s]:%i", buf, (int)ntohs(ipv6->sin6_port));
56 static int mkmcastsk4(struct in_addr group, int port)
60 struct sockaddr_in nm;
63 fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
65 if(setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &soval, sizeof(soval)))
67 memset(&nm, 0, sizeof(nm));
68 nm.sin_family = AF_INET;
69 nm.sin_port = htons(port);
70 if(bind(fd, (struct sockaddr *)&nm, sizeof(nm)))
72 memset(&mreq, 0, sizeof(mreq));
73 mreq.imr_multiaddr = group;
74 if(setsockopt(fd, SOL_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)))
77 if(setsockopt(fd, SOL_IP, IP_MULTICAST_LOOP, &soval, sizeof(soval)))
82 static __attribute__ ((unused)) void test(int fd)
91 ret = poll(&pfd, 1, -1);
93 fprintf(stderr, "mctap: poll: %s\n", strerror(errno));
97 ret = read(fd, buf, sizeof(buf));
99 fprintf(stderr, "mctap: read: %s\n", strerror(errno));
102 for(i = 0; i < ret; i++) {
103 printf("%02x ", (unsigned char)buf[i]);
112 static void bridge(int sock, int tap, struct sockaddr *dst, socklen_t dstlen)
116 struct pollfd pfds[2];
119 fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_NONBLOCK);
120 fcntl(tap, F_SETFL, fcntl(tap, F_GETFL) | O_NONBLOCK);
123 pfds[0].events = POLLIN;
125 pfds[1].events = POLLIN;
126 ret = poll(pfds, 2, -1);
129 fprintf(stderr, "mctap: poll: %s\n", strerror(errno));
134 if(pfds[0].revents) {
135 ret = read(sock, buf, sizeof(buf));
137 if((errno != EINTR) && (errno != EAGAIN)) {
138 fprintf(stderr, "mctap: mcast packet: %s\n", strerror(errno));
142 if(sizeof(buf) - ret < sizeof(pi)) {
145 memmove(buf + sizeof(pi), buf, ret);
148 memcpy(buf, &pi, sizeof(pi));
149 write(tap, buf, ret);
153 if(pfds[1].revents) {
154 ret = read(tap, buf, sizeof(buf));
156 if((errno != EINTR) && (errno != EAGAIN)) {
157 fprintf(stderr, "mctap: mcast packet: %s\n", strerror(errno));
161 if(ret < sizeof(pi)) {
164 memcpy(&pi, buf, sizeof(pi));
165 if(pi.flags & TUN_PKT_STRIP) {
168 sendto(sock, buf + sizeof(pi), ret - sizeof(pi), 0, dst, dstlen);
176 static int maketap(char *name)
181 if((fd = open("/dev/net/tun", O_RDWR)) < 0)
183 memset(&rb, 0, sizeof(rb));
184 rb.ifr_flags = IFF_TAP;
185 strncpy(rb.ifr_name, name, IFNAMSIZ);
186 if(ioctl(fd, TUNSETIFF, &rb))
191 int main(int argc, char **argv)
195 struct in_addr group;
198 struct sockaddr_in dst;
201 while((c = getopt(argc, argv, "hD:")) >= 0) {
214 if(argc - optind < 2) {
218 if(!inet_aton(argv[optind], &group)) {
219 fprintf(stderr, "mctap: invalid group address: %s\n", argv[optind]);
222 port = atoi(argv[optind + 1]);
223 if((sock = mkmcastsk4(group, port)) < 0) {
224 fprintf(stderr, "mctap: could not create multicast socket: %s\n", strerror(errno));
227 if((tap = maketap(tapname)) < 0) {
228 fprintf(stderr, "mctap: could not create TAP device: %s\n", strerror(errno));
232 memset(&dst, 0, sizeof(dst));
233 dst.sin_family = AF_INET;
234 dst.sin_addr = group;
235 dst.sin_port = htons(port);
236 bridge(sock, tap, (struct sockaddr *)&dst, sizeof(dst));