binding RPC communication socket to a specific interface

I faced the problem, that a background daemon process needed to communication with an
external tool via RPC-calls.

The problem at the customer site is, that the daemon executes on a server which runs
in a cluster and gets a dynamic interface. So the outgoing traffic must be from the dynamic interface. This is necessary for the firewall, to have all packets on the network the
same origin adress.

The clnttcp_create() allows to supply a filedescriptor.
Now it is possible to create a socket and bind it to a specific interface.

After starting and tracing with truss, it shows, that the portmap-Call to port 111
is done via the default interface and not the binding interface.

After searching for the librcpsoc-Source on opensolaris for clnttcp_create, it is
known that without a target port the lib creates an own connection to the portmapper
to request the port number on the remote system.

The open point is now, that the RPC-server should be bound to a fixed port, which I have to
verify now.