Fixed two problems:

1. The code that looks at btl_tcp_if_exclude before doing a
   modex_send uses strcmp rather than strncmp. That means that
   "lo0" gets sent even though "lo" is excluded.

2. The code that determines whether a particular local TCP
   interface can connect to a particular remote interface doesn't
   check for loopback interfaces. With this fix, users can now
   enable "lo" and be assured that it will only be used for intra-
   node communication.

This commit was SVN r22762.

ompi/mca/btl/tcp/btl_tcp_component.c

@@ -610,7 +610,7 @@ static int mca_btl_tcp_component_create_instances(void)
             /* check to see if this interface exists in the exclude list */
             argv = exclude;
             while(argv && *argv) {
-                if(strcmp(*argv,if_name) == 0)
+                if(strncmp(*argv,if_name,strlen(*argv)) == 0)
                     break;
                 argv++;
             }

ompi/mca/btl/tcp/btl_tcp_proc.c

@@ -504,8 +504,18 @@ int mca_btl_tcp_proc_insert( mca_btl_tcp_proc_t* btl_proc,
             if(NULL != local_interfaces[i]->ipv4_address &&
                NULL != peer_interfaces[j]->ipv4_address) {
 
+                /*  check for loopback */
+                if ((opal_net_islocalhost((struct sockaddr *)local_interfaces[i]->ipv4_address)
+                     && !opal_net_islocalhost((struct sockaddr *)peer_interfaces[j]->ipv4_address))
+                    || (opal_net_islocalhost((struct sockaddr *)peer_interfaces[j]->ipv4_address)
+                        && !opal_net_islocalhost((struct sockaddr *)local_interfaces[i]->ipv4_address))
+                    || (opal_net_islocalhost((struct sockaddr *)local_interfaces[i]->ipv4_address)
+                        && !opal_ifislocal(btl_proc->proc_ompi->proc_hostname))) {
+
+                    /* No connection is possible on these interfaces */
+                
                 /*  check for RFC1918 */
-                if(opal_net_addr_isipv4public((struct sockaddr*) local_interfaces[i]->ipv4_address)
+                } else if(opal_net_addr_isipv4public((struct sockaddr*) local_interfaces[i]->ipv4_address)
                    && opal_net_addr_isipv4public((struct sockaddr*) 
                                                  peer_interfaces[j]->ipv4_address)) {
                     if(opal_net_samenetwork((struct sockaddr*) local_interfaces[i]->ipv4_address,
@@ -534,7 +544,18 @@ int mca_btl_tcp_proc_insert( mca_btl_tcp_proc_t* btl_proc,
              */
             if(NULL != local_interfaces[i]->ipv6_address &&
                NULL != peer_interfaces[j]->ipv6_address) {
-                if(opal_net_samenetwork((struct sockaddr*) local_interfaces[i]->ipv6_address,
+
+                /*  check for loopback */
+                if ((opal_net_islocalhost((struct sockaddr *)local_interfaces[i]->ipv6_address)
+                     && !opal_net_islocalhost((struct sockaddr *)peer_interfaces[j]->ipv6_address))
+                    || (opal_net_islocalhost((struct sockaddr *)peer_interfaces[j]->ipv6_address)
+                        && !opal_net_islocalhost((struct sockaddr *)local_interfaces[i]->ipv6_address))
+                    || (opal_net_islocalhost((struct sockaddr *)local_interfaces[i]->ipv6_address)
+                        && !opal_ifislocal(btl_proc->proc_ompi->proc_hostname))) {
+
+                    /* No connection is possible on these interfaces */
+
+                } else if(opal_net_samenetwork((struct sockaddr*) local_interfaces[i]->ipv6_address,
                                         (struct sockaddr*) peer_interfaces[j]->ipv6_address,
                                         local_interfaces[i]->ipv6_netmask)) {
                     weights[i][j] = CQ_PUBLIC_SAME_NETWORK;