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[Qemu-devel] Re: [PATCH RFC 0/4] Dumping traffic when using netdev devic
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH RFC 0/4] Dumping traffic when using netdev devices |
Date: |
Fri, 16 Jul 2010 08:34:48 +0200 |
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Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Miguel Di Ciurcio Filho wrote:
> Hello,
>
> This is a prototype suggestion. I mostly copied and pasted the code from
> net/dump.c into net.c and made some adjustments. There is no command line
> parsing involved yet, just the internals and small changes in net/tap.c and
> net/slirp.c do make the thing work.
>
> In my tests, using tap as backend, e1000 as a guest device and running iperf
> from
> guest to host, the overhead of dumping the traffic caused a loss of around 30%
> of performance.
No surprise, dump writes are synchronous. The day this is actually
hurting someone, we may see asynchronous patches.
>
> I opened the dumped files in wireshark and they looked fine. When using slirp
> all requests were dumped fine too.
>
> Bugs/limitations:
> - I have no clue on how to deal with tap+vhost, is it necessary?
I don't think so. Do you can still do "tcpdump -i tap0" in that
scenario, don't you? Then definitely not.
> - When using virtio-net, I'm not sure how to handle iovec when vnet_hdr=on
Let the sending peer report (offset field or callback) where to find the
payload in a frame.
That channel - or a separate one - could also be used to detect if a
peer supports dumping at all (vhost...). Then no peer code need to be
extended with dump management code, all could be moved into net.c
> - Create a function to add dump to a netdev on the fly, is it necessary?
Yes. That way you don't need to shutdown&restart your VM just to enable
or disable dumping - quite important in certain tests.
> - Handle cleanups
>
> Miguel Di Ciurcio Filho (4):
> net/dump: Make pcap structures public
> net: Introduce NetClientDump and auxiliary functions
> net/tap: Suggested support for NetClientDump
> net/slirp: Suggested support for NetClientDump
>
> net.c | 90
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> net.h | 8 +++++
> net/dump.c | 21 -------------
> net/dump.h | 21 +++++++++++++
> net/slirp.c | 3 ++
> net/tap.c | 3 ++
> qemu-common.h | 1 +
> 7 files changed, 126 insertions(+), 21 deletions(-)
>
Thanks for picking this up!
Jan
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- [Qemu-devel] [PATCH RFC 0/4] Dumping traffic when using netdev devices, Miguel Di Ciurcio Filho, 2010/07/15
- [Qemu-devel] [PATCH RFC 1/4] net/dump: Make pcap structures public, Miguel Di Ciurcio Filho, 2010/07/15
- [Qemu-devel] [PATCH RFC 2/4] net: Introduce NetClientDump and auxiliary functions, Miguel Di Ciurcio Filho, 2010/07/15
- [Qemu-devel] [PATCH RFC 3/4] net/tap: Suggested support for NetClientDump, Miguel Di Ciurcio Filho, 2010/07/15
- [Qemu-devel] [PATCH RFC 4/4] net/slirp: Suggested support for NetClientDump, Miguel Di Ciurcio Filho, 2010/07/15
- [Qemu-devel] Re: [PATCH RFC 0/4] Dumping traffic when using netdev devices,
Jan Kiszka <=
- [Qemu-devel] Re: [PATCH RFC 0/4] Dumping traffic when using netdev devices, Anthony Liguori, 2010/07/16
- [Qemu-devel] Re: [PATCH RFC 0/4] Dumping traffic when using netdev devices, Jan Kiszka, 2010/07/16