Allow to specify UDPv4/6 multicast interface

[paraslash.git] / udp_send.c

diff --git a/udp_send.c b/udp_send.c
index 8eee7e61ac83bd60d56c171bdf01986492e4526b..140458e7ed9b1d4e3a03d05c2e26a6b36d66db54 100644 (file)
--- a/udp_send.c
+++ b/udp_send.c
@@ -74,19 +74,24 @@ static void udp_delete_target(struct udp_target *ut, const char *msg)
  * \param fd   The connected socket descriptor.
  * \param ttl  UDPv4 multicast TTL or UDPv6 multicast number of hops.
  *             Use -1 to mean default, 0..255 otherwise.
-
- ** \return Zero if okay, negative on error.
+ * \param iface        The outgoing multicast interface, or NULL for the default.
+ *
+ * \return Zero if okay, negative on error.
  */
-static int mcast_sender_setup(struct udp_target *ut, int ttl)
+static int mcast_sender_setup(struct udp_target *ut, int ttl, char *iface)
 {
        struct sockaddr_storage ss;
        socklen_t sslen = sizeof(ss);
 
        const int on = 1;
+       int id = iface == NULL ? 0 : if_nametoindex(iface);
 
        if (getpeername(ut->fd, (struct sockaddr *)&ss, &sslen) < 0)
                goto err;
 
+       if (iface != NULL && id == 0)
+               PARA_WARNING_LOG("could not resolve interface %s, using default", iface);
+
        /* RFC 3493, 5.2: -1 means 'use kernel default' */
        if (ttl < 0 || ttl > 255)
                ttl = -1;
@@ -95,6 +100,18 @@ static int mcast_sender_setup(struct udp_target *ut, int ttl)
        case AF_INET:
                if (!IN_MULTICAST(htonl(((struct sockaddr_in *)&ss)->sin_addr.s_addr)))
                        return 0;
+               if (id != 0) {
+#ifdef HAVE_IP_MREQN
+                       struct ip_mreqn mn;
+
+                       memset(&mn, 0, sizeof(mn));
+                       mn.imr_ifindex = id;
+                       if (setsockopt(ut->fd, IPPROTO_IP, IP_MULTICAST_IF, &mn, sizeof(mn)) < 0)
+                               goto err;
+#else
+                       PARA_ERROR_LOG("No support for setting outgoing IPv4 mcast interface.");
+#endif
+               }
                /*
                 * Enable receiving multicast messages generated on the local host
                 * At least on Linux, this is enabled by default.
@@ -111,6 +128,9 @@ static int mcast_sender_setup(struct udp_target *ut, int ttl)
        case AF_INET6:
                if (!IN6_IS_ADDR_MULTICAST(&((struct sockaddr_in6 *)&ss)->sin6_addr))
                        return 0;
+               if (id != 0 &&
+                   setsockopt(ut->fd, IPPROTO_IPV6, IPV6_MULTICAST_IF, &id, sizeof(id)) < 0)
+                       break;
                if (setsockopt(ut->fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &on, sizeof(on)) < 0)
                        break;
                if (setsockopt(ut->fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl)) < 0)
@@ -130,6 +150,7 @@ err:
 static int udp_init_session(struct udp_target *ut)
 {
        int ret;
+       char *iface = NULL;
 
        if (ut->fd >= 0) /* nothing to do */
                return 0;
@@ -139,7 +160,10 @@ static int udp_init_session(struct udp_target *ut)
                return ret;
        ut->fd = ret;
 
-       ret = mcast_sender_setup(ut, conf.udp_ttl_arg);
+       if (conf.udp_mcast_iface_given)
+               iface = conf.udp_mcast_iface_arg;
+
+       ret = mcast_sender_setup(ut, conf.udp_ttl_arg, iface);
        if (ret < 0) {
                close(ut->fd);
                return ret;