make the code work for bridge interfaces

[project/mdnsd.git] / util.c

diff --git a/util.c b/util.c
index a4a117b..1708a40 100644 (file)
--- a/util.c
+++ b/util.c
@@ -98,6 +98,28 @@ get_iface_ipv4(const char *ifname)
        return ret;
 }
 
+int
+get_iface_index(const char *ifname)
+{
+       struct ifreq ir;
+       int sock;
+
+       sock = socket(AF_INET, SOCK_DGRAM, 0);
+       if (sock < 0)
+               return 0;
+
+       memset(&ir, 0, sizeof(struct ifreq));
+
+       strncpy(ir.ifr_name, ifname, sizeof(ir.ifr_name));
+
+       if (ioctl(sock, SIOCGIFINDEX, &ir) < 0)
+               return 0;
+
+       close(sock);
+
+       return ir.ifr_ifindex;
+}
+
 char*
 get_hostname(void)
 {
@@ -116,15 +138,19 @@ socket_setup(int fd, const char *ip)
        uint8_t ttl = 255;
        int yes = 1;
        int no = 0;
-       struct sockaddr_in sa;
+       struct sockaddr_in sa = { 0 };
+       struct in_addr in;
+
+       inet_aton(iface_ip, &in);
 
        sa.sin_family = AF_INET;
        sa.sin_port = htons(MCAST_PORT);
        inet_pton(AF_INET, MCAST_ADDR, &sa.sin_addr);
 
        memset(&mreq, 0, sizeof(mreq));
-       mreq.imr_address.s_addr = htonl(INADDR_ANY);
+       mreq.imr_address.s_addr = in.s_addr;
        mreq.imr_multiaddr = sa.sin_addr;
+       mreq.imr_ifindex = iface_index;
 
        if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)) < 0)
                fprintf(stderr, "ioctl failed: IP_MULTICAST_TTL\n");
@@ -132,6 +158,13 @@ socket_setup(int fd, const char *ip)
        if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) < 0)
                fprintf(stderr, "ioctl failed: SO_REUSEADDR\n");
 
+       /* Some network drivers have issues with dropping membership of
+        * mcast groups when the iface is down, but don't allow rejoining
+        * when it comes back up. This is an ugly workaround
+        * -- this was copied from avahi --
+        */
+       setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
+
        if (setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
                fprintf(stderr, "failed to join multicast group: %s\n", strerror(errno));
                close(fd);