Re: [uml-devel] Connecting UML_SWITCH and Wireshark

[Julien Iguchi-C. <jul...@un...>]

Hello Jeff,

Both solutions don't satisfy my needs.

- My UML machines run only in terminal mode (no X)
- I don't want to use mechanisms which require root rights.

I've investigated the code of uml_switch and I think a slight
modification can offer a user-level sniff for UML: add a new request
type (uml_switch.c) and create a simple program which connect to the
uml_switch and just dump (in raw or libpcap format) in standard input
the traffic.

I don't think it requires a lot of works...

Julien.

Jeff Dike wrote:
> 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
> 


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