Re: Bridging console port to a telnet session

On Jan 17, 2007, at 11:00 AM, Kailas Ramasamy wrote:

Hi Mike,

Thanks a lot. This is what I was looking for.

-Kailas

On 1/17/07, Mike Meyer <mwm@xxxxxxxxx> wrote:

In <ecd0bee40701171024p7c5b4944of45b4c407ed3c5f4@xxxxxxxxxxxxxx>, Kailas
Ramasamy <kailasr@xxxxxxxxx> typed:
> Hi Mike,
> I read through fork() and exec() man pages but I couldn't find anything
> related to
> this. Basically, I want to launch a telnet session from a process and
pass
> in
> /dev/console as stdin and stdout.

Well, you don't really need fork(), though fork() follows exec() so
often than some OS's combine them into a single call. And I just
noticed that if you do "man exec", you get the shell's page - you want
exec(3), to get the C calls.

Anyway, the sequence is:

Use open() to get an fd pointing at /dev/console.
Use dup2() to copy that fd to stdin and stdout (and probably stderr).
Use an exec() function to launch telnet.

<mike


> Thanks
> Kailas
>
> On 1/16/07, Mike Meyer <mwm@xxxxxxxxx> wrote:
> >
> > In <ecd0bee40701161732v26112f24o2d8323c2777d2f7@xxxxxxxxxxxxxx>,
Kailas
> > Ramasamy <kailasr@xxxxxxxxx> typed:
> > > Hi Mike,
> > > Yes, that what I am planing but I want to do this dynamically. Do
you
> > know
> > > how to launch a
> > > telnet session from a process?. How do I pass stdin and stdout to
the
> > telnet
> > > from a process?.
> >
> > See the fork() and exec() man pages.
> >
> > <mike
> >
> >
> > > On 1/16/07, Mike Meyer <mwm@xxxxxxxxx> wrote:
> > > >
> > > > In <ecd0bee40701161503k385819ddgba5562e137630617@xxxxxxxxxxxxxx>,
> > Kailas
> > > > Ramasamy <kailasr@xxxxxxxxx> typed:
> > > > > Hi,
> > > > > Within a FreeBSD system, I want to telnet to another system and
> > bridge
> > > > that
> > > > > session to the
> > > > > console port so that when an user connects to the system via
console
> > > > port,
> > > > > it is automatically
> > > > > redirected to other system for I have already established a
telnet
> > > > session.
> > > >
> > > > What's wrong with simply leaving a telnet session running on the
> > > > console, maybe with some support to relaunch it should it ever
exit?
> > > >
> > > > <mike
> > > > --
> > > > Mike Meyer <mwm@xxxxxxxxx>
> > > > http://www.mired.org/consulting.html
> > > > Independent Network/Unix/Perforce consultant, email for more
> > information.
> > > >
> > > _______________________________________________
> > > freebsd-hackers@xxxxxxxxxxx mailing list
> > > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
> > > To unsubscribe, send any mail to "
> > freebsd-hackers-unsubscribe@xxxxxxxxxxx"
> > >
> >
> > --
> > Mike Meyer <mwm@xxxxxxxxx>
> > http://www.mired.org/consulting.html
> > Independent Network/Unix/Perforce consultant, email for more
information.
> >
> Hi Mike,<br>I read through fork() and exec() man pages but I
couldn&#39;t find anything related to<br>this. Basically, I want to launch a
telnet session from a process and pass in <br>/dev/console as stdin and
stdout. <br>
> <br>Thanks<br>Kailas<br><br><div><span class="gmail_quote">On 1/16/07,
<b class="gmail_sendername">Mike Meyer</b> &lt;<a href="mailto:
mwm@xxxxxxxxx">mwm@xxxxxxxxx</a>&gt; wrote:</span><blockquote
class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204);
margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
> In &lt;<a href="mailto:
ecd0bee40701161732v26112f24o2d8323c2777d2f7@xxxxxxxxxxxxxx">
ecd0bee40701161732v26112f24o2d8323c2777d2f7@xxxxxxxxxxxxxx</ a>&gt;, Kailas
Ramasamy &lt;<a href="mailto:kailasr@xxxxxxxxx";>kailasr@xxxxxxxxx
> </a>&gt; typed:<br>&gt; Hi Mike,<br>&gt; Yes, that what I am planing but
I want to do this dynamically. Do you know<br>&gt; how to launch a<br>&gt;
telnet session from a process?. How do I pass stdin and stdout to the telnet
> <br>&gt; from a process?.<br><br>See the fork() and exec() man
pages.<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;mik e<br><br><br>&gt;
On 1/16/07, Mike Meyer &lt;<a href="mailto:mwm@xxxxxxxxx";>mwm@xxxxxxxxx</a>&gt;
wrote:<br>&gt; &gt;<br>&gt; &gt; In &lt;
> <a href="mailto:
ecd0bee40701161503k385819ddgba5562e137630617@xxxxxxxxxxxxxx">
ecd0bee40701161503k385819ddgba5562e137630617@xxxxxxxxxxxxxx</a>&gt;,
Kailas<br>&gt; &gt; Ramasamy &lt;<a href="mailto:kailasr@xxxxxxxxx";>
kailasr@xxxxxxxxx
> </a>&gt; typed:<br>&gt; &gt; &gt; Hi,<br>&gt; &gt; &gt; Within a FreeBSD
system, I want to telnet to another system and bridge<br>&gt; &gt;
that<br>&gt; &gt; &gt; session to the<br>&gt; &gt; &gt; console port so that
when an user connects to the system via console
> <br>&gt; &gt; port,<br>&gt; &gt; &gt; it is automatically<br>&gt; &gt;
&gt; redirected to other system for I have already established a
telnet<br>&gt; &gt; session.<br>&gt; &gt;<br>&gt; &gt; What&#39;s wrong with
simply leaving a telnet session running on the
> <br>&gt; &gt; console, maybe with some support to relaunch it should it
ever exit?<br>&gt; &gt;<br>&gt;
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;mike<br>&gt; &gt;
--<br>&gt; &gt; Mike Meyer &lt;<a href="mailto:mwm@xxxxxxxxx";>
mwm@xxxxxxxxx</a>&gt;
> <br>&gt; &gt; <a href="http://www.mired.org/consulting.html";>
http://www.mired.org/consulting.html</a><br>&gt; &gt; Independent
Network/Unix/Perforce consultant, email for more information.<br>&gt;
&gt;<br>&gt;

Kailas cross posted this to the questions@ list too. I gave a possible answer there.
-Garrett
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