Date: Sun, 27 Jan 2008 14:22:17 +0100 From: Max Laier <max@love2party.net> To: Stefan Lambrev <stefan.lambrev@moneybookers.com> Cc: freebsd-current@freebsd.org Subject: Re: FreeBSD 7, bridge, PF and syn flood = very bad performance Message-ID: <200801271422.23340.max@love2party.net> In-Reply-To: <479C4F31.7090804@moneybookers.com> References: <479A2389.2000802@moneybookers.com> <200801262227.36970.max@love2party.net> <479C4F31.7090804@moneybookers.com>
next in thread | previous in thread | raw e-mail | index | archive | help
--nextPart2828494.SRAVsIoMmF Content-Type: text/plain; charset="iso-8859-6" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On Sunday 27 January 2008, Stefan Lambrev wrote: > Goo Day, > > Max Laier wrote: > > On Saturday 26 January 2008, Stefan Lambrev wrote: > >> Max Laier wrote: > >>> On Friday 25 January 2008, Stefan Lambrev wrote: > >>>> Greetings, > >>>> > >>>> Does anyone try to see PF with "keep state" in action when under > >>>> syn flood attack? > >>>> I tried to get some help in freebsd-pf@, because the test > >>>> firewall, that I build hardly can handle 2-5MB/s syn flood. > >>>> Unfortunately I do not saw useful advice. > >>>> The problem is that a quad core bridge firewall running freebsd 7 > >>>> amd64 with PF is near useless and can't handle "small" SYN ddos. > >>>> > >>>> Here is the schema that I'm testing: > >>>> web server (freebsd) - freebsd (bridged interfaces) - gigabit > >>>> switch - clients + flooders > >>>> In this configuration ~25MB/s syn flood (and I think this limit is > >>>> because of my switch) is not a problem and the web server responds > >>>> without a problem. > >>>> With this configuration netperf -l 610 -p 10303 -H 10.3.3.1 shows > >>>> 116MB/s stable speed , so I guess there are no problems with > >>>> cables, hardware and etc :) > >>>> > >>>> But when I start pf (see below the config file) the traffic drops > >>>> to 2-3MB/s and the web server is hardly accessible. > >>>> It seems that device polling helps a lot in this situation, and at > >>>> least the bridge firewall is accessible. Without "polling" the > >>>> firewall is so heavily loaded > >>>> that even commands like "date" take few seconds to finish, with 2 > >>>> cores at ~100% idle at same time. > >>>> > >>>> I have "flat profiles" from hwpmc, and I think it indicates a > >>>> problem: > >>>> > >>>> (bridge, pf enabled, polling enabled, sched_ule - I have profiles > >>>> and for other combinations too if needed) > >>>> % cumulative self self total > >>>> time seconds seconds calls ms/call ms/call name > >>>> 24.0 268416.00 268416.00 0 100.00% > >>>> _mtx_lock_sleep > >>> > >>> Can you build a kernel with LOCK_PROFILING and try to figure out > >>> which lock is causing this? > >> > >> Yes I can build kernel with LOCK_PROFILING. > >> But I have no idea how to use it :) > >> Can you point me to some documentation? > > > > man LOCK_PROFILING > > > > basically: > > # sysctl debug.lock.prof.enable=3D1 && sleep 60 && \ > > sysctl debug.lock.prof.enable=3D0 && \ > > sysctl debug.lock.prof.stats > log > > > > while under attack to sample one minute of lock statistics. > > Well I think the interesting lines from this experiment are: > max total wait_total count avg > wait_avg cnt_hold cnt_lock name > 39 25328476 70950955 9015860 2 7 > 5854948 6309848 /usr/src/sys/contrib/pf/net/pf.c:6729 (sleep > mutex:pf task mtx) > 936935 10645209 350 50 212904 7 > 110 47 /usr/src/sys/contrib/pf/net/pf.c:980 (sleep mutex:pf > task mtx) Yeah, those two mostly are the culprit, but a quick fix is not really=20 available. You can try to "set timeout interval" to something bigger=20 (e.g. 60 seconds) which will decrease the average hold time of the second=20 lock instance at the cost of increased peak memory usage. I have the ideas how to fix this, but it will take much much more time=20 than I currently have for FreeBSD :-\ In general this requires a bottom=20 up redesign of pf locking and some data structures involved in the state=20 tree handling. The first(=3Dmain) lock instance is also far from optimal (i.e. pf is a=20 congestion point in the bridge forwarding path). For this I have also a=20 plan how to make at least state table lookups run in parallel to some=20 extend, but again the lack of free time to spend coding prevents me from=20 doing it at the moment :-\ =2D-=20 /"\ Best regards, | mlaier@freebsd.org \ / Max Laier | ICQ #67774661 X http://pf4freebsd.love2party.net/ | mlaier@EFnet / \ ASCII Ribbon Campaign | Against HTML Mail and News --nextPart2828494.SRAVsIoMmF Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQBHnIWPXyyEoT62BG0RAo/PAJ9+jlOo/Sf/pSVmqvSyMO7jiMnbtgCeKSkX vrtQrvezUl30zCrFCDvUk8A= =/psX -----END PGP SIGNATURE----- --nextPart2828494.SRAVsIoMmF--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200801271422.23340.max>