Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!TRANTOR.UMD.EDU!louie
From: louie@TRANTOR.UMD.EDU ("Louis A. Mamakos")
Newsgroups: comp.protocols.tcp-ip
Subject: Re: BSD and SunOS bug in UDP ICMP_UNREACH_PORT handling
Message-ID: <8905100412.AA12383@trantor.umd.edu>
Date: 10 May 89 04:12:08 GMT
References: <7497@spool.cs.wisc.edu>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 14

In fact, this same bug exists with TCP connections. If for instance,
an ICMP port unreachable is returned from a host for a TCP connection
(some IBM VM systems do this), all TCP connection to that remote host
get ECONNREFUSED dropped into so_error in the PCB.  Now, this doesn't
actually abort the connection; usually the applications choke on the
error returned the next time they reference the socket and close the
connection.  Our quick fix is to ignore port unreachable ICMP messages
for all TCP connections. 

Why return an ICMP port unreachable message (in addition to a TCP reset
segment)?  I'm assured that there is a good reason, and it has something to
do with a security option of some sort.

louie