Change in libosmocore[master]: socket: Add osmo_sock_mcast_iface_set() to bind multicast to device

[laforge]

laforge has submitted this change. ( https://gerrit.osmocom.org/c/libosmocore/+/17418 )

Change subject: socket: Add osmo_sock_mcast_iface_set() to bind multicast to device
......................................................................

socket: Add osmo_sock_mcast_iface_set() to bind multicast to device

Change-Id: Ib52d22710020b56965aefcef09bde8247ace4a9c
Related: OS#2966
---
M include/osmocom/core/socket.h
M src/socket.c
2 files changed, 23 insertions(+), 0 deletions(-)

Approvals:
  laforge: Looks good to me, approved
  fixeria: Looks good to me, but someone else must approve
  Jenkins Builder: Verified



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

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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Change-Id: Ib52d22710020b56965aefcef09bde8247ace4a9c
Gerrit-Change-Number: 17418
Gerrit-PatchSet: 5
Gerrit-Owner: laforge <laforge at osmocom.org>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria <axilirator at gmail.com>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-CC: neels <nhofmeyr at sysmocom.de>
Gerrit-MessageType: merged
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