socket: Add osmo_sock_mcast_iface_set() to bind multicast to device
Change-Id: Ib52d22710020b56965aefcef09bde8247ace4a9c
Related: OS#2966
diff --git a/include/osmocom/core/socket.h b/include/osmocom/core/socket.h
index e26ca0d..129612c 100644
--- a/include/osmocom/core/socket.h
+++ b/include/osmocom/core/socket.h
@@ -87,6 +87,7 @@
int osmo_sock_mcast_loop_set(int fd, bool enable);
int osmo_sock_mcast_ttl_set(int fd, uint8_t ttl);
int osmo_sock_mcast_all_set(int fd, bool enable);
+int osmo_sock_mcast_iface_set(int fd, const char *ifname);
int osmo_sock_mcast_subscribe(int fd, const char *grp_addr);
int osmo_sock_local_ip(char *local_ip, const char *remote_ip);
diff --git a/src/socket.c b/src/socket.c
index 9b1d30e..503ceaf 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -41,6 +41,7 @@
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/un.h>
+#include <net/if.h>
#include <netinet/in.h>
#include <arpa/inet.h>
@@ -1194,6 +1195,27 @@
}
}
+/*! Set the network device to which we should bind the multicast socket
+ * \param[in] fd file descriptor of related socket
+ * \param[in] ifname name of network interface to user for multicast
+ * \returns 0 on success; negative otherwise */
+int osmo_sock_mcast_iface_set(int fd, const char *ifname)
+{
+ unsigned int ifindex;
+ struct ip_mreqn mr;
+
+ /* first, resolve interface name to ifindex */
+ ifindex = if_nametoindex(ifname);
+ if (ifindex == 0)
+ return -errno;
+
+ /* next, configure kernel to use that ifindex for this sockets multicast traffic */
+ memset(&mr, 0, sizeof(mr));
+ mr.imr_ifindex = ifindex;
+ return setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, &mr, sizeof(mr));
+}
+
+
/*! Enable/disable receiving all multicast packets, even for non-subscribed groups
* \param[in] fd file descriptor of related socket
* \param[in] enable Enable or Disable receiving of all packets