Coda File System

Re: yer port numbers suck

From: <>
Date: 17 Apr 1998 02:50:49 -0000
In article <>, you wrote:

>I don't see how tcpmux could really translate to UDP, which is unfortunate.
>I'd much prefer to connect to services on other machines by names like 
>"telnet", "ftp", and "http" than by names like "23", "21", and "80".
>(Even if I *do* have `http' in /etc/services.  It would be better to do
>the mapping on the server side, not the client.)

I'm sure someone else has noted this, but ONC RPC supports this via
'forwarding'.  You can send a packet to the portmapper (port 111) instructing
it to forward the packet to the appropriate service on the server.  The
portmap process will then send the remainder of the packet to the service's
port address via loopback, and forward the reply to the original sender.

They originally introduced this for the purpose of broadcast -- since a
broadcast packet has to go to the same port on all machines, to make a
broadcast RPC request you have to send to the portmapper and have it do the
appropriate forwarding on each machine.

This has become quite deprecated because of the security ramifications.
All too many ONC RPC-based protocols use host IP address for authentication,
and using the forwarding facility of "portmap" makes it look like your packet
originated from the server host itself.

But, as you point out, this has little to do with Coda.

Received on 1998-04-16 22:54:14