A possible network bug in Sun unix?

Richard Johnson netser%limbo.uci.edu at icsg.UCI.EDU
Thu Dec 18 10:56:07 AEST 1986


One of our Computing Support people here (Scott Menter) noticed a strange
problem today.  We investigated and we don't know exactly what to make of
the situation.  Let me explain:

1) You rlogin from your sun workstation (Sun-3/50 in this case) to another
   system on the network.
2) Your sun workstation crashes.
3) After rebooting you try to rlogin to the same other system again and
   you can't even after multiple tries.

We investigated and found that Sun seems to always allocate the first
unused port number above 1021 for an rlogin connection.  Since the
other end of the rlogin will stick around until some I/O forces it to
recognize the connection is broken (we just cat'ed to the pty on the remote
system and it closed), you'll get the same hosta:porta - hostb:portb pair
EVERY time and that HAS to be rejected by the remote system because of the
way TCP connections are defined!

Of course all you have to do to work around it is just rlogin to some OTHER
system and then rlogin to the one you want!

Is this a bug?  Am I missing something?  (By the way, this is SUN 3.0.)

----------------------------------------------------------------------------
Richard Johnson                          netser at ics.uci.edu       (Internet)
UCI ICS Network Services                 ...!ucbvax!ucivax!netser     (UUCP)



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