ospf6d: justify multicast group management

* ospf6_network.[ch]
  * ospf6_sso(): new function supersedes ospf6_join_allspfrouters(),
    ospf6_leave_allspfrouters(), ospf6_join_alldrouters() and
    ospf6_leave_alldrouters()
* ospf6_interface.c
  * ospf6_interface_state_change(): update respectively
  * interface_up(): ditto
  * interface_down(): ditto
diff --git a/ospf6d/ospf6_interface.c b/ospf6d/ospf6_interface.c
index 13d6980..f642051 100644
--- a/ospf6d/ospf6_interface.c
+++ b/ospf6d/ospf6_interface.c
@@ -399,12 +399,12 @@
        prev_state == OSPF6_INTERFACE_BDR) &&
       (next_state != OSPF6_INTERFACE_DR &&
        next_state != OSPF6_INTERFACE_BDR))
-    ospf6_leave_alldrouters (oi->interface->ifindex);
+    ospf6_sso (oi->interface->ifindex, &alldrouters6, IPV6_LEAVE_GROUP);
   if ((prev_state != OSPF6_INTERFACE_DR &&
        prev_state != OSPF6_INTERFACE_BDR) &&
       (next_state == OSPF6_INTERFACE_DR ||
        next_state == OSPF6_INTERFACE_BDR))
-    ospf6_join_alldrouters (oi->interface->ifindex);
+    ospf6_sso (oi->interface->ifindex, &alldrouters6, IPV6_JOIN_GROUP);
 
   OSPF6_ROUTER_LSA_SCHEDULE (oi->area);
   if (next_state == OSPF6_INTERFACE_DOWN)
@@ -612,7 +612,7 @@
     }
 
   /* Join AllSPFRouters */
-  ospf6_join_allspfrouters (oi->interface->ifindex);
+  ospf6_sso (oi->interface->ifindex, &allspfrouters6, IPV6_JOIN_GROUP);
 
   /* Update interface route */
   ospf6_interface_connected_route_update (oi->interface);
@@ -707,7 +707,7 @@
 
   /* Leave AllSPFRouters */
   if (oi->state > OSPF6_INTERFACE_DOWN)
-    ospf6_leave_allspfrouters (oi->interface->ifindex);
+    ospf6_sso (oi->interface->ifindex, &allspfrouters6, IPV6_LEAVE_GROUP);
 
   ospf6_interface_state_change (OSPF6_INTERFACE_DOWN, oi);
 
diff --git a/ospf6d/ospf6_network.c b/ospf6d/ospf6_network.c
index 3372238..e5a1436 100644
--- a/ospf6d/ospf6_network.c
+++ b/ospf6d/ospf6_network.c
@@ -120,86 +120,22 @@
   return 0;
 }
 
+/* ospf6 set socket option */
 void
-ospf6_join_allspfrouters (u_int ifindex)
+ospf6_sso (u_int ifindex, struct in6_addr *group, int option)
 {
   struct ipv6_mreq mreq6;
-  int retval;
+  int ret;
 
   assert (ifindex);
   mreq6.ipv6mr_interface = ifindex;
-  memcpy (&mreq6.ipv6mr_multiaddr, &allspfrouters6,
-          sizeof (struct in6_addr));
+  memcpy (&mreq6.ipv6mr_multiaddr, group, sizeof (struct in6_addr));
 
-  retval = setsockopt (ospf6_sock, IPPROTO_IPV6, IPV6_JOIN_GROUP,
-                       &mreq6, sizeof (mreq6));
-
-  if (retval < 0)
-    zlog_err ("Network: Join AllSPFRouters on ifindex %d failed: %s",
-              ifindex, safe_strerror (errno));
-#if 0
-  else
-    zlog_debug ("Network: Join AllSPFRouters on ifindex %d", ifindex);
-#endif
-}
-
-void
-ospf6_leave_allspfrouters (u_int ifindex)
-{
-  struct ipv6_mreq mreq6;
-
-  assert (ifindex);
-  mreq6.ipv6mr_interface = ifindex;
-  memcpy (&mreq6.ipv6mr_multiaddr, &allspfrouters6,
-          sizeof (struct in6_addr));
-
-  if (setsockopt (ospf6_sock, IPPROTO_IPV6, IPV6_LEAVE_GROUP,
-                  &mreq6, sizeof (mreq6)) < 0)
-    zlog_warn ("Network: Leave AllSPFRouters on ifindex %d Failed: %s",
-               ifindex, safe_strerror (errno));
-#if 0
-  else
-    zlog_debug ("Network: Leave AllSPFRouters on ifindex %d", ifindex);
-#endif
-}
-
-void
-ospf6_join_alldrouters (u_int ifindex)
-{
-  struct ipv6_mreq mreq6;
-
-  assert (ifindex);
-  mreq6.ipv6mr_interface = ifindex;
-  memcpy (&mreq6.ipv6mr_multiaddr, &alldrouters6,
-          sizeof (struct in6_addr));
-
-  if (setsockopt (ospf6_sock, IPPROTO_IPV6, IPV6_JOIN_GROUP,
-                  &mreq6, sizeof (mreq6)) < 0)
-    zlog_warn ("Network: Join AllDRouters on ifindex %d Failed: %s",
-               ifindex, safe_strerror (errno));
-#if 0
-  else
-    zlog_debug ("Network: Join AllDRouters on ifindex %d", ifindex);
-#endif
-}
-
-void
-ospf6_leave_alldrouters (u_int ifindex)
-{
-  struct ipv6_mreq mreq6;
-
-  assert (ifindex);
-  mreq6.ipv6mr_interface = ifindex;
-  memcpy (&mreq6.ipv6mr_multiaddr, &alldrouters6,
-          sizeof (struct in6_addr));
-
-  if (setsockopt (ospf6_sock, IPPROTO_IPV6, IPV6_LEAVE_GROUP,
-                  &mreq6, sizeof (mreq6)) < 0)
-    zlog_warn ("Network: Leave AllDRouters on ifindex %d Failed", ifindex);
-#if 0
-  else
-    zlog_debug ("Network: Leave AllDRouters on ifindex %d", ifindex);
-#endif
+  ret = setsockopt (ospf6_sock, IPPROTO_IPV6, option,
+                    &mreq6, sizeof (mreq6));
+  if (ret < 0)
+    zlog_err ("Network: setsockopt (%d) on ifindex %d failed: %s",
+              option, ifindex, safe_strerror (errno));
 }
 
 static int
diff --git a/ospf6d/ospf6_network.h b/ospf6d/ospf6_network.h
index fd8758e..0526b3e 100644
--- a/ospf6d/ospf6_network.h
+++ b/ospf6d/ospf6_network.h
@@ -35,11 +35,7 @@
 extern void ospf6_set_checksum (void);
 
 extern int ospf6_serv_sock (void);
-
-extern void ospf6_join_allspfrouters (u_int);
-extern void ospf6_leave_allspfrouters (u_int);
-extern void ospf6_join_alldrouters (u_int);
-extern void ospf6_leave_alldrouters (u_int);
+extern void ospf6_sso (u_int ifindex, struct in6_addr *group, int option);
 
 extern int ospf6_sendmsg (struct in6_addr *, struct in6_addr *,
                           unsigned int *, struct iovec *);