2005-10-20 Andrew J. Schorr <ajschorr@alumni.princeton.edu>

	* sockopt.c: (setsockopt_multicast_ipv4) If IP_ADD_MEMBERSHIP
	  fails with errno equal to EADDRINUSE, then issue an info
	  message and try IP_DROP_MEMBERSHIP followed by IP_ADD_MEMBERSHIP.

diff --git a/lib/ChangeLog b/lib/ChangeLog
index c94e5639ca0d1ccf61c7c7c8c56bb6045c1d3fac..26b478bf1662f55a6dffc546447651feada2e026 100644 (file)
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,3 +1,9 @@
+2005-10-20 Andrew J. Schorr <ajschorr@alumni.princeton.edu>
+
+       * sockopt.c: (setsockopt_multicast_ipv4) If IP_ADD_MEMBERSHIP
+         fails with errno equal to EADDRINUSE, then issue an info
+         message and try IP_DROP_MEMBERSHIP followed by IP_ADD_MEMBERSHIP.
+
 2005-10-20 Andrew J. Schorr <ajschorr@alumni.princeton.edu>
 
        * memory.c: (show_memory_vty) Omit zero statistics.  Print separators

diff --git a/lib/sockopt.c b/lib/sockopt.c
index 655ecdc06ed7273245bd0f5e8090eff8f47a86e2..6ddbded132c5430f9e5c6566cbf210f115408555 100644 (file)
--- a/lib/sockopt.c
+++ b/lib/sockopt.c
@@ -162,6 +162,16 @@ getsockopt_ipv6_ifindex (struct msghdr *msgh)
  * using a single socket.  The limit is typically 20, derived from the
  * original BSD multicast implementation.  Some systems have
  * mechanisms for increasing this limit.
+ *
+ * In many 4.4BSD-derived systems, multicast group operations are not
+ * allowed on interfaces that are not UP.  Thus, a previous attempt to
+ * leave the group may have failed, leaving it still joined, and we
+ * drop/join quietly to recover.  This may not be necessary, but aims to
+ * defend against unknown behavior in that we will still return an error
+ * if the second join fails.  It is not clear how other systems
+ * (e.g. Linux, Solaris) behave when leaving groups on down interfaces,
+ * but this behavior should not be harmful if they behave the same way,
+ * allow leaves, or implicitly leave all groups joined to down interfaces.
  */
 int
 setsockopt_multicast_ipv4(int sock, 
@@ -174,6 +184,7 @@ setsockopt_multicast_ipv4(int sock,
 #ifdef HAVE_STRUCT_IP_MREQN_IMR_IFINDEX
   /* This is better because it uses ifindex directly */
   struct ip_mreqn mreqn;
+  int ret;
   
   switch (optname)
     {
@@ -190,7 +201,24 @@ setsockopt_multicast_ipv4(int sock,
       else
        mreqn.imr_address = if_addr;
       
-      return setsockopt(sock, IPPROTO_IP, optname, (void *)&mreqn, sizeof(mreqn));
+      ret = setsockopt(sock, IPPROTO_IP, optname,
+                      (void *)&mreqn, sizeof(mreqn));
+      if ((ret < 0) && (optname == IP_ADD_MEMBERSHIP) && (errno == EADDRINUSE))
+        {
+         /* see above: handle possible problem when interface comes back up */
+         char buf[2][INET_ADDRSTRLEN];
+         zlog_info("setsockopt_multicast_ipv4 attempting to drop and "
+                   "re-add (fd %d, ifaddr %s, mcast %s, ifindex %u)",
+                   sock,
+                   inet_ntop(AF_INET, &if_addr, buf[0], sizeof(buf[0])),
+                   inet_ntop(AF_INET, &mreqn.imr_multiaddr,
+                             buf[1], sizeof(buf[1])), ifindex);
+         setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP,
+                    (void *)&mreqn, sizeof(mreqn));
+         ret = setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP,
+                          (void *)&mreqn, sizeof(mreqn));
+        }
+      return ret;
       break;
 
     default:
@@ -210,6 +238,7 @@ setsockopt_multicast_ipv4(int sock,
 
   struct in_addr m;
   struct ip_mreq mreq;
+  int ret;
 
 #ifdef HAVE_BSD_STRUCT_IP_MREQ_HACK
   if (ifindex)
@@ -230,11 +259,23 @@ setsockopt_multicast_ipv4(int sock,
       mreq.imr_multiaddr.s_addr = mcast_addr;
       mreq.imr_interface = m;
       
-      return setsockopt (sock, 
-                        IPPROTO_IP, 
-                        optname, 
-                        (void *)&mreq, 
-                        sizeof(mreq));
+      ret = setsockopt (sock, IPPROTO_IP, optname, (void *)&mreq, sizeof(mreq));
+      if ((ret < 0) && (optname == IP_ADD_MEMBERSHIP) && (errno == EADDRINUSE))
+        {
+         /* see above: handle possible problem when interface comes back up */
+         char buf[2][INET_ADDRSTRLEN];
+         zlog_info("setsockopt_multicast_ipv4 attempting to drop and "
+                   "re-add (fd %d, ifaddr %s, mcast %s, ifindex %u)",
+                   sock,
+                   inet_ntop(AF_INET, &if_addr, buf[0], sizeof(buf[0])),
+                   inet_ntop(AF_INET, &mreq.imr_multiaddr,
+                             buf[1], sizeof(buf[1])), ifindex);
+         setsockopt (sock, IPPROTO_IP, IP_DROP_MEMBERSHIP,
+                     (void *)&mreq, sizeof(mreq));
+         ret = setsockopt (sock, IPPROTO_IP, IP_ADD_MEMBERSHIP,
+                           (void *)&mreq, sizeof(mreq));
+        }
+      return ret;
       break;
       
     default: