rsh and rcp problems between Solaris and FreeBSD

[Matthew Seaman]

On Wed, Dec 31, 2003 at 10:08:03AM -0500, John Von Essen wrote:
> I can do two rsh's back to back with no problems, its the third (and 4th
> and so on) that hang.
> 
> On the FreeBSD side, after the first rsh, netstat shows:
> 
> tcp4       0      0  mx100.851              embryo.bluebell..1021 
> TIME_WAIT
> tcp4       0      0  mx100.shell            embryo.bluebell..1022
> TIME_WAIT
> 
> Those connections stay around for awhile, about 30 seconds. Only when they
> disappear does the next rsh work.

OK.  Some progress.  This rules out problems due to limitations in the
number of possible connections you can have open at any one time -- if
the limit is just two, then there would be a lot more things
complaining than just rcp(1).  And you'ld have to try exceedingly hard
to get a FBSD system that limited.

Hmmm...  What flags are you invoking inetd(8) with on the FreeBSD
side?  Specifically are you using any of these (quoting from the
manual page):

     -c maximum
             Specify the default maximum number of simultaneous invocations of
             each service; the default is unlimited.  May be overridden on a
             per-service basis with the "max-child" parameter.

     -C rate
             Specify the default maximum number of times a service can be
             invoked from a single IP address in one minute; the default is
             unlimited.  May be overridden on a per-service basis with the
             "max-connections-per-ip-per-minute" parameter.

     -R rate
             Specify the maximum number of times a service can be invoked in
             one minute; the default is 256.  A rate of 0 allows an unlimited
             number of invocations.

     -s maximum
             Specify the default maximum number of simultaneous invocations of
             each service from a single IP address; the default is unlimited.
             May be overridden on a per-service basis with the "max-child-per-
             ip" parameter.

The symptoms you describe could be caused eg. by running with '-s 2'
in the inetd flags (you're getting two socket connections per rsh or
rcp invocation because a second channel is opened to carry the stderr
from the invoked command, but that doesn't count towards inetd's
connection limits).

The default for all of these is unlimited (ie. inetd_flags="-wW") and
there aren't any per-service limits on the rsh (shell) service in the
default inetd.conf.  I generally use:

    inetd_flags="-wWl -R 1024 -c 128 -a ${hostname}"

in my /etc/rc.conf on internet facing machines where I run inetd(8) --
if this is a purely internal machine (which it certainly should be if
you're using rsh(1) on it) then I wouldn't bother with any sort of
connection rate-limiting, at least for the time being.

Hmmm... As well -- what's the output of:

    % sysctl net.inet.tcp.delayed_ack

You might try setting that to zero to turn off delayed ack. That's
where the system will wait for about a minute before sending an ACK in
order to try and coalesce it with a data packet.  Usually that's a win
performance-wise.  See tcp(4).  There's also the RFC1644 support you
might want to try toggling: see ttcp(4) -- I'm unable to find any
definitive statement on the net about Solaris support for this, so no
idea if it will actually help or not.

> As for the rcp, I was missing a trailing slash, apparently rcp -r syntax
> between Solaris and FreeBSD is a little different. So the rcp's work, but
> that take just as long as the rsh calls.

That's one problem down then.  Good.

> As for name resolution, the Solaris box uses dns, and so does FreeBSD.
> Both have some entries in the hosts file.

That's good too.  Rules out some more areas which could be causing the
trouble.

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP: http://www.infracaninophile.co.uk/pgpkey         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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