Re: [Qemu-devel] [PATCH v2 0/5] For QEMU 2.5: Network traffic dumping for -netdev devices

[Yang Hongyang]

Hi Thomas, Jason, Stefan

  I'm reading the QEMU network subsystem and am thinking implement a
network filter between network backend and NIC devices. All packets
will pass by this filter, therefore, dump can be easily done with
the filter.

                  +--------------+       +-------------+
    +----------+  |    filter    |       |frontend(NIC)|
    | real     |  |              |       |             |
    | network  <--+backend       <-------+             |
    | backend  |  |         peer +-------> peer        |
    +----------+  +--------------+       +-------------+

The filter is actually a full featured network backend, either you
can call this a transparent proxy.

A prototype patch will be sent in reply to this mail. The patch tested
with tap backend.

I want your input about whether this is plausible or the design of this
is completely wrong?

Thank you in advance.

On 07/13/2015 03:39 PM, Thomas Huth wrote:
> The "-net dump" option only works with the "-net" option. So far, it
> is not possible to dump network traffic with the "-netdev" option yet.
> This patch series now fixes this ugliness by enabling dumping for the
> "-netdev" option, too.
>
> Unlike with the "-net dump" option, the "-netdev" parameter does not
> "abuse" the disliked internal vlan hub infrastructure to achieve this
> functionality. This patch series introduces a new, clean "dumpfile=xxx"
> option for the -netdev parameters instead.
>
> The patches are intended for QEMU version 2.5, but I'm sending them
> now already in case somebody got some spare minutes left for reviewing
> them again.
>
> Note: I did not address multiqueue devices yet (but added a TODO in the
> source code) ... I will address that later when the basic patches have
> been accepted.
>
> v2:
> - Restructured the code a little bit
> - Updated target QEMU version from 2.4. to 2.5
> - Addressed review feedback from Jason, Stefan and Markus:
>    - Use iov_copy() instead of copying the iov manually
>    - Fix return value of net_dump_receive_iov() if fd is invalid
>    - Use get_vhost_net() to detect vhost devices
>    - Close the fd when netdev is deleted
>    - Added some more comments in the source code
>
> Thomas Huth (5):
>    net/dump: Add support for receive_iov function
>    net/dump: Move DumpState into NetClientState
>    net/dump: Rework net-dump init functions
>    net/dump: Add dump option for netdev devices
>    qemu options: Add information about dumpfile to help text
>
>   include/net/net.h |  8 +++++
>   net/clients.h     |  6 ++++
>   net/dump.c        | 99 +++++++++++++++++++++++++++++++++++++++----------------
>   net/net.c         | 38 ++++++++++++++++++++-
>   qapi-schema.json  | 12 +++++--
>   qemu-options.hx   | 26 ++++++++++-----
>   6 files changed, 149 insertions(+), 40 deletions(-)

--
Thanks,
Yang.