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Re: mirage xen pcap example

On Thu, Sep 20, 2012 at 10:37 PM, Anil Madhavapeddy <anil@xxxxxxxxxx> wrote:
> On 20 Sep 2012, at 16:54, David Scott <scott.dj@xxxxxxxxx> wrote:
>> Hi,
>> I did a bit of refactoring to the pcap stuff. It now consists of the
>> following pieces:
>> 1. The master branch of mirage-net
>> https://github.com/mirage/mirage-net
>> has an extended "promiscuous hook"
>> 2. The master branch of ocaml-pcap
>> https://github.com/mirage/ocaml-pcap
>> has a library "pcap.mirage"
>> There's an example showing how to turn it on in my branch of mirage-www:
>> https://github.com/djs55/mirage-www/tree/pcap
>> It will start appending packets to its first disk (disk 0 =/= 51712 =/= 
>> 'xvda')
>> I added "make run" which invokes "mir-run" and "xl", but it would also
>> be easy with xapi -- just make sure there's a disk for it to write to.
> This will make debugging those TCP bugs hello easier. Thanks!
> To be clear, it will dump the raw pcap to the block device as-is, and not 
> using
> the FAT32 library, right?  So it's best to make sure the first disk is a 
> blktap
> file, which will make it a valid pcap file to use from dom0... ?

Yup, it dumps to a raw block device. The 'make run' in the mirage-www
branch will create a temporary file by dd'ing 128M of zeroes. If you
tell tcpdump to read that then it will work, although it will get a
bit confused by all the zeroes at the end. It works well enough to
diagnose problems anyway!


Dave Scott



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