Clarifying and fixing SCTP btl_sctp_if_11 parameter

This commit was SVN r17834.

ompi/mca/btl/sctp/btl_sctp_component.c

@@ -239,8 +239,11 @@ int mca_btl_sctp_component_open(void)
     /* use a single one-to-many socket by default except in Solaris (see
      *  the configure.m4 file)
      */
-    mca_btl_sctp_component.sctp_if_11 =
-        mca_btl_sctp_param_register_int ("if_11", OMPI_MCA_BTL_SCTP_USE_ONE_TO_ONE_SOCKET);
+    mca_base_param_reg_int(&mca_btl_sctp_component.super.btl_version,
+                           "if_11", "If 0, have one SCTP BTL module and let SCTP do multilink scheduling. If non-zero, have an SCTP BTL module per link and let the PML do the scheduling.",
+                           false, false,
+                           OMPI_MCA_BTL_SCTP_USE_ONE_TO_ONE_SOCKET,
+                           &mca_btl_sctp_component.sctp_if_11);
 
     /* have lower exclusivity than tcp */
     mca_btl_sctp_module.super.btl_exclusivity = MCA_BTL_EXCLUSIVITY_LOW;

ompi/mca/btl/sctp/btl_sctp_proc.c

@@ -203,7 +203,16 @@ int mca_btl_sctp_proc_insert(
         if(endpoint_addr->addr_inuse != 0) {
             continue;
         }
-        if(net1 == net2) {
+        /* in the 1-to-many code, we sctp_bindx all addresses to one
+         *  association, and only represent this multi-NIC endpoint
+         *  internally as one BTL. this is within mca_btl_sctp_create.
+         *  this is done so that SCTP itself handles multi-path scenarios
+         *  since the transport has multihoming.  as a result, we simply
+         *  have to pick one of the addresses in the association (it doesn't
+         *  matter to the API which is chosen); we pick the one which bind
+         *  is called (NOT sctp_bindx) even if it is a private IP...
+         */
+        if(net1 == net2 || 0 == mca_btl_sctp_component.sctp_if_11) {
             btl_endpoint->endpoint_addr = endpoint_addr;
             break;
         } else if(btl_endpoint->endpoint_addr != 0) {