The RPC client now reports the maximum payload size supported by the chosen
 transport method.  This is something a little less than 64KB for RPC over
 UDP, and about 2GB - 1 for RPC over TCP.  The effective rsize and wsize
 values are not allowed to exceed the reported maximum RPC payload size.
Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>