Add support of IP_MULTICAST_IF in UDP sockets.

net/udp/udp_socket_libevent.cc

Index: net/udp/udp_socket_libevent.cc
diff --git a/net/udp/udp_socket_libevent.cc b/net/udp/udp_socket_libevent.cc
index 990aa5758cca8f463ec0caf615432091a2847ac1..0ae12ebbe472e28222214b8458815c2d8a532bb9 100644
--- a/net/udp/udp_socket_libevent.cc
+++ b/net/udp/udp_socket_libevent.cc
@@ -42,6 +42,7 @@ UDPSocketLibevent::UDPSocketLibevent(
         : socket_(kInvalidSocket),
           addr_family_(0),
           socket_options_(SOCKET_OPTION_MULTICAST_LOOP),
+          multicast_interface_(0),
           multicast_time_to_live_(1),
           bind_type_(bind_type),
           rand_int_cb_(rand_int_cb),
@@ -532,6 +533,32 @@ int UDPSocketLibevent::SetSocketOptions() {
     if (rv < 0)
       return MapSystemError(errno);
   }
+  if (multicast_interface_ != 0) {
+    switch (addr_family_) {
+      case AF_INET: {
+        in_addr address;
+        address.s_addr = htonl(multicast_interface_);

[Noam Samuel, 2013/12/02 22:05:54]

I know that the 0.x.x.x address convention for numbered interfaces is used in
Windows, but are you sure it exists in Linux/Mac OSX?

[szym, 2013/12/03 07:42:11]

In Linux, IP_MULTICAST_IF option has to be one of:
struct in_addr
struct ip_mreq
struct ip_mreqn

In the first two, the interface is looked up by IP address (ip_dev_find). In the
last one, if imr_ifindex is non-zero, then it is used as the interface index
(dev_get_by_index).

See: http://lxr.free-electrons.com/source/net/ipv4/ip_sockglue.c#L666

+        int rv = setsockopt(socket_, IPPROTO_IP, IP_MULTICAST_IF,
+                            reinterpret_cast<const char*>(&address),
+                            sizeof(address));
+        if (rv)
+          return MapSystemError(errno);
+        break;
+      }
+      case AF_INET6: {
+        uint32 interface_index = multicast_interface_;
+        int rv = setsockopt(socket_, IPPROTO_IPV6, IPV6_MULTICAST_IF,
+                            reinterpret_cast<const char*>(&interface_index),
+                            sizeof(interface_index));
+        if (rv)
+          return MapSystemError(errno);
+        break;
+      }
+      default:
+        NOTREACHED() << "Invalid address family";
+        return ERR_ADDRESS_INVALID;
+    }
+  }
   return OK;
 }
 
@@ -557,7 +584,7 @@ int UDPSocketLibevent::RandomBind(const IPEndPoint& address) {
   return DoBind(IPEndPoint(ip, 0));
 }
 
-int UDPSocketLibevent::JoinGroup(const IPAddressNumber& group_address) const {
+int UDPSocketLibevent::JoinGroup(const IPAddressNumber& group_address) {
   DCHECK(CalledOnValidThread());
   if (!is_connected())
     return ERR_SOCKET_NOT_CONNECTED;
@@ -567,7 +594,7 @@ int UDPSocketLibevent::JoinGroup(const IPAddressNumber& group_address) const {
       if (addr_family_ != AF_INET)
         return ERR_ADDRESS_INVALID;
       ip_mreq mreq;
-      mreq.imr_interface.s_addr = INADDR_ANY;
+      mreq.imr_interface.s_addr = htonl(multicast_interface_);

[Noam Samuel, 2013/12/02 22:05:54]

Same question

       memcpy(&mreq.imr_multiaddr, &group_address[0], kIPv4AddressSize);
       int rv = setsockopt(socket_, IPPROTO_IP, IP_ADD_MEMBERSHIP,
                           &mreq, sizeof(mreq));
@@ -579,7 +606,7 @@ int UDPSocketLibevent::JoinGroup(const IPAddressNumber& group_address) const {
       if (addr_family_ != AF_INET6)
         return ERR_ADDRESS_INVALID;
       ipv6_mreq mreq;
-      mreq.ipv6mr_interface = 0;  // 0 indicates default multicast interface.
+      mreq.ipv6mr_interface = multicast_interface_;
       memcpy(&mreq.ipv6mr_multiaddr, &group_address[0], kIPv6AddressSize);
       int rv = setsockopt(socket_, IPPROTO_IPV6, IPV6_JOIN_GROUP,
                           &mreq, sizeof(mreq));
@@ -593,7 +620,7 @@ int UDPSocketLibevent::JoinGroup(const IPAddressNumber& group_address) const {
   }
 }
 
-int UDPSocketLibevent::LeaveGroup(const IPAddressNumber& group_address) const {
+int UDPSocketLibevent::LeaveGroup(const IPAddressNumber& group_address) {
   DCHECK(CalledOnValidThread());
 
   if (!is_connected())
@@ -630,6 +657,14 @@ int UDPSocketLibevent::LeaveGroup(const IPAddressNumber& group_address) const {
   }
 }
 
+int UDPSocketLibevent::SetMulticastInterface(uint32 interface_index) {
+  DCHECK(CalledOnValidThread());
+  if (is_connected())
+    return ERR_SOCKET_IS_CONNECTED;
+  multicast_interface_ = interface_index;
+  return OK;
+}
+
 int UDPSocketLibevent::SetMulticastTimeToLive(int time_to_live) {
   DCHECK(CalledOnValidThread());
   if (is_connected())