static int net_socket_mcast_create(struct sockaddr_in *mcastaddr, struct in_addr *localaddr) { struct ip_mreq imr; int fd; int val, ret; if (!IN_MULTICAST(ntohl(mcastaddr->sin_addr.s_addr))) { fprintf(stderr, "qemu: error: specified mcastaddr \"%s\" (0x%08x) does not contain a multicast address\n", inet_ntoa(mcastaddr->sin_addr), (int)ntohl(mcastaddr->sin_addr.s_addr)); return -1; } fd = qemu_socket(PF_INET, SOCK_DGRAM, 0); if (fd < 0) { perror("socket(PF_INET, SOCK_DGRAM)"); return -1; } val = 1; ret=setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (const char *)&val, sizeof(val)); if (ret < 0) { perror("setsockopt(SOL_SOCKET, SO_REUSEADDR)"); goto fail; } ret = bind(fd, (struct sockaddr *)mcastaddr, sizeof(*mcastaddr)); if (ret < 0) { perror("bind"); goto fail; } /* Add host to multicast group */ imr.imr_multiaddr = mcastaddr->sin_addr; if (localaddr) { imr.imr_interface = *localaddr; } else { imr.imr_interface.s_addr = htonl(INADDR_ANY); } ret = setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (const char *)&imr, sizeof(struct ip_mreq)); if (ret < 0) { perror("setsockopt(IP_ADD_MEMBERSHIP)"); goto fail; } /* Force mcast msgs to loopback (eg. several QEMUs in same host */ val = 1; ret=setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, (const char *)&val, sizeof(val)); if (ret < 0) { perror("setsockopt(SOL_IP, IP_MULTICAST_LOOP)"); goto fail; } /* If a bind address is given, only send packets from that address */ if (localaddr != NULL) { ret = setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, (const char *)localaddr, sizeof(*localaddr)); if (ret < 0) { perror("setsockopt(IP_MULTICAST_IF)"); goto fail; } } socket_set_nonblock(fd); return fd; fail: if (fd >= 0) closesocket(fd); return -1; }