I got the following message about the problems with Ultrix and connections
that suddenly are closed:

From sendmail-r8-request@CS.Berkeley.EDU Tue Oct 12 15:55:12 1993
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To: sendmail-r8@CS.Berkeley.EDU
From: Eric Allman <eric@CS.Berkeley.EDU>
Subject: IDENT protocol info
Date: Tue, 12 Oct 1993 07:47:26 -0700
Sender: eric@mastodon.CS.Berkeley.EDU
Keywords: pidentd

I received the following describing the changes needed to run IDENT
on Ultrix.

eric

------- Forwarded Message

From: Dan Mosedale <mosedale@genome.stanford.edu>
Message-Id: <199310111806.AA06654@aeffle.Stanford.EDU>
Subject: Re: anonymous mail
To: eric@CS.Berkeley.EDU
Date: Mon, 11 Oct 1993 11:06:25 +119303928 (PDT)
Newsgroups: comp.security.misc
Organization: Stanford University Genetics Department

In article <294d8i$il8@agate.berkeley.edu> you write:
>In article <2948np$6eu@usenet.INS.CWRU.Edu>, mcn@nostromo.cwru.edu (Michael Neuman) writes:
>|> 2) Hack up sendmail to use rfc931.
>
>Unfortunately, TCP/IP bugs in many operating systems make it impossible
>to implement RFC931 (actually RFC 1413 -- 931 has been obsoleted).  In
>particular, I've had problems with HP-UX and Ultrix, among others.

FWIW, I've got pidentd 2.1.2 running under Ultrix 4.3 with a few
caveats.  For one thing, it doesn't work properly from inetd, it has
to be run in daemon mode.  However, the fact that it runs at all is
probably due to the fact that I've got the following patch installed:

/usr/sys/MIPS/BINARY/in_pcb.o                   (CLD CXO-8919)
CHECKSUM:  56412 72
/usr/sys/MIPS/BINARY/ip_icmp.o
CHECKSUM:  30060 43
/usr/sys/MIPS/BINARY/tcp_subr.o
CHECKSUM:  58085 56 
/usr/sys/MIPS/BINARY/udp_usrreq.o
CHECKSUM:  24862 74
/usr/sys/MIPS/BINARY/uipc_domain.o
CHECKSUM:  29573 17
- ----------------------------------

Establish an ftp session with a host across the gateway and put the
process in background. Telnet to the same host using an unused port to
force a "Host Unreachable" situation. Go back to the ftp session and
it is dead.

In order to fix the problem, the in_pcbnotify() routine in in_pcb.c should
be aware of the local and foreign ports for a given connection. To fascilitate
this the lport and fport parameters were added to in_pcbnotify. This required
the calling routines (tcp_ctlinput and udp_ctlinput) to be called with an
additional parameter, a pointer to the ip structure. The tcp header can be
accessed in this ip structure.  The tcp header yields the foreign and local
ports.

- -Dan

------- End of Forwarded Message