Re: tcp/ip bug (2.2.12) or telnet client bug

Craig Milo Rogers (rogers@ISI.EDU)
Mon, 27 Sep 1999 10:28:15 -0700

>while [ 1 ]; to telnet 127.0.0.1 1234; done
>
>(where 1234 is a tcp port not being bind()'d, works with any other
>unused port):
...
>I insist, there is no daemon listening on the specified port.
>Anything i type in is simply echo'd.

This is a known deficiency in the Linux TCP/IP implementation;
we discussed it on this list last month (30-Aug-1999). Th policy
should be that when the kernel allocates a local port number to a
socket, it should not use the local port number that is the same as
the remote port number for the socket; this policy will avoid the
unpredictable self-connects when a port-not-in-use error would be
expected.

The fix is very easy, so easy that I, ah, didn't distribute a
proper patch file. I'll try to do so in the next day or two, if no
one beats me to it.

Craig Milo Rogers

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