Re: [uml-devel] Connecting UML_SWITCH and Wireshark

[Jeff Dike <jdike@addtoit.com>]

On Mon, Sep 01, 2008 at 05:44:39PM +0200, Julien Iguchi-Cartigny wrote:
> I'm using Netkit (www.netkit.org): it's a network simulator using UML
> and I want to show packets exchanged between the UML machines. I believe
> the best way is to
> 
> - use wireshark with the flag "-" to capture packets in the standard input.
> - use netcat to read the data socket of uml_switch and print to the
> standard output
> 
> But uml_switch uses a ctl socket to open new port. I need a way to
> manually open a port by uml_switch to connect netcat. I don't think
> uml_switch offer command-line instruction for this, so is the best way
> to write a short program writing on the ctl socket of uml_switch ? If
> yes, what data to send to uml_switch ?

If you want to capture UML network traffic going over uml_switch (be
it with wireshark or tcpdump - it doesn't matter), there are two basic
ways of doing it:
	enable hub mode (uml_switch -hub) and then either

	sniff from a UML's eth0 (a third UML if you don't want to
interfere with the communicating UMLs), or
	add a host tap device to the switch (uml_switch -tap tap<n>)
and sniff that.

				Jeff

-- 
Work email - jdike at linux dot intel dot com

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