FreeBSD 7, bridge, PF and syn flood = very bad performance
max at love2party.net
Sat Jan 26 13:27:40 PST 2008
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?
# sysctl debug.lock.prof.enable=1 && sleep 60 && \
sysctl debug.lock.prof.enable=0 && \
sysctl debug.lock.prof.stats > log
while under attack to sample one minute of lock statistics.
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