Index: mcast.cpp
===================================================================
--- mcast.cpp	(revision 392)
+++ mcast.cpp	(working copy)
@@ -124,6 +124,11 @@
             if(ifr.ifr_flags&IFF_MULTICAST)     ifi->if_flags|=IF_MULTICAST;
         }
 
+        if(ioctl(s,SIOCGIFINDEX,&ifr)!=-1)
+        {
+            ifi->if_index=ifr.ifr_ifindex;
+        }
+
         close(s);
     }
 
@@ -229,6 +234,7 @@
     if(!iface)
         iface="";
 
+    mcast_if_index=0;
     mcast_ttl=ttl;
     mcast_loop=loop;
 
@@ -278,6 +284,7 @@
             if_info ifi;
             get_if_info(iface,&ifi);
             memcpy((char*)&mcast_if_sin,&ifi.if_sin,sizeof(sockaddr_in));
+            mcast_if_index=ifi.if_index;
         }else
             mcast_if_sin.sin_addr.s_addr=inet_addr(iface);
     }
@@ -293,6 +300,7 @@
     {
         fprintf(verb_fp,"multicast interface address: '%s'\n",mcast_if_sin.sin_addr.s_addr==INADDR_ANY?"any":inet_ntoa(mcast_if_sin.sin_addr));
         fprintf(verb_fp,"multicast group address: '%s:%i'\n",inet_ntoa(mcast_sin.sin_addr),ntohs(mcast_sin.sin_port));
+        fprintf(verb_fp,"multicast interface index: %d\n",mcast_if_index);
     }
 
     snprintf(interface,sizeof(interface),"%s",inet_ntoa(mcast_if_sin.sin_addr));
@@ -320,17 +328,28 @@
 
         if(!bind(sock,(sockaddr*)&sin,sizeof(sin)))
         {
+            in_addr local_addr;
+            local_addr.s_addr=mcast_if_sin.sin_addr.s_addr;
+#ifdef __FreeBSD__
             ip_mreq mcast_group;
+#else
+            ip_mreqn mcast_group;
+#endif
             memset((char*)&mcast_group,0,sizeof(mcast_group));
             mcast_group.imr_multiaddr.s_addr=mcast_sin.sin_addr.s_addr;
-            mcast_group.imr_interface.s_addr=mcast_if_sin.sin_addr.s_addr;
+#ifdef __FreeBSD__
+            mcast_group.imr_interface.s_addr=local_addr.s_addr;
+#else
+            mcast_group.imr_address.s_addr=local_addr.s_addr;
+            mcast_group.imr_ifindex=mcast_if_index;
+#endif
 
             if(!setsockopt(sock,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mcast_group,sizeof(mcast_group)))
             {
                 if(verb_fp)
                 {
                     fprintf(verb_fp,"join to multicast group '%s:%i' on ",inet_ntoa(mcast_group.imr_multiaddr),ntohs(sin.sin_port));
-                    fprintf(verb_fp,"interface '%s'\n",mcast_group.imr_interface.s_addr==INADDR_ANY?"any":inet_ntoa(mcast_group.imr_interface));
+                    fprintf(verb_fp,"interface '%s'\n",local_addr.s_addr==INADDR_ANY?"any":inet_ntoa(local_addr));
                 }
 
                 return sock;
@@ -352,24 +371,35 @@
 
 int mcast::mcast_grp::leave(int sock) const
 {
+    in_addr local_addr;
+    local_addr.s_addr=mcast_if_sin.sin_addr.s_addr;
+#ifdef __FreeBSD__
     ip_mreq mcast_group;
+#else
+    ip_mreqn mcast_group;
+#endif
     memset((char*)&mcast_group,0,sizeof(mcast_group));
     mcast_group.imr_multiaddr.s_addr=mcast_sin.sin_addr.s_addr;
-    mcast_group.imr_interface.s_addr=mcast_if_sin.sin_addr.s_addr;
+#ifdef __FreeBSD__
+    mcast_group.imr_interface.s_addr=local_addr.s_addr;
+#else
+    mcast_group.imr_address.s_addr=local_addr.s_addr;
+    mcast_group.imr_ifindex=mcast_if_index;
+#endif
 
     if(!setsockopt(sock,IPPROTO_IP,IP_DROP_MEMBERSHIP,&mcast_group,sizeof(mcast_group)))
     {
         if(verb_fp)
         {
             fprintf(verb_fp,"leave multicast group '%s' on ",inet_ntoa(mcast_group.imr_multiaddr));
-            fprintf(verb_fp,"interface '%s'\n",mcast_group.imr_interface.s_addr==INADDR_ANY?"any":inet_ntoa(mcast_group.imr_interface));
+            fprintf(verb_fp,"interface '%s'\n",local_addr.s_addr==INADDR_ANY?"any":inet_ntoa(local_addr));
         }
     }else
     {
         if(verb_fp)
         {
             fprintf(verb_fp,"can`t leave multicast group '%s' on ",inet_ntoa(mcast_group.imr_multiaddr));
-            fprintf(verb_fp,"interface '%s'\n",mcast_group.imr_interface.s_addr==INADDR_ANY?"any":inet_ntoa(mcast_group.imr_interface));
+            fprintf(verb_fp,"interface '%s'\n",local_addr.s_addr==INADDR_ANY?"any":inet_ntoa(local_addr));
         }
     }
 
@@ -386,7 +416,16 @@
     {
         setsockopt(sock,IPPROTO_IP,IP_MULTICAST_TTL,&mcast_ttl,sizeof(mcast_ttl));
         setsockopt(sock,IPPROTO_IP,IP_MULTICAST_LOOP,&mcast_loop,sizeof(mcast_loop));
+#ifdef __FreeBSD__
         setsockopt(sock,IPPROTO_IP,IP_MULTICAST_IF,&mcast_if_sin.sin_addr,sizeof(in_addr));
+#else
+        ip_mreqn mcast_group;
+        memset((char*)&mcast_group,0,sizeof(mcast_group));
+        mcast_group.imr_multiaddr.s_addr=mcast_sin.sin_addr.s_addr;
+        mcast_group.imr_address.s_addr=mcast_if_sin.sin_addr.s_addr;
+        mcast_group.imr_ifindex=mcast_if_index;
+        setsockopt(sock,IPPROTO_IP,IP_MULTICAST_IF,&mcast_group,sizeof(mcast_group));
+#endif
 
         sockaddr_in sin;
         sin.sin_family=AF_INET;
Index: mcast.h
===================================================================
--- mcast.h	(revision 392)
+++ mcast.h	(working copy)
@@ -34,6 +34,7 @@
         char if_name[IF_NAME_LEN];
         char if_addr[IF_ADDR_LEN];
         sockaddr_in if_sin;
+        int if_index;
         u_int32_t if_flags;
     };
 
@@ -56,6 +57,7 @@
     protected:
         sockaddr_in mcast_sin;
         sockaddr_in mcast_if_sin;
+        int mcast_if_index;
         int mcast_ttl;
         int mcast_loop;
     public: