Date: Fri, 10 Sep 2010 03:18:16 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: Gareth de Vaux <bsd@lordcow.org> Cc: stable@freebsd.org Subject: Re: ipfw: Too many dynamic rules Message-ID: <20100910023132.E73353@sola.nimnet.asn.au> In-Reply-To: <20100909153902.GA28341@lordcow.org> References: <20100909153902.GA28341@lordcow.org>
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On Thu, 9 Sep 2010, Gareth de Vaux wrote: > Hi again, I use some keep-state rules in ipfw, but get the following > kernel message: > > kernel: ipfw: install_state: Too many dynamic rules > > when presumably my state table reaches its limit (and I effectively > get DoS'd). > > netstat shows tons of connections in FIN_WAIT_2 state, mostly to > my webserver. Consequently net.inet.ip.fw.dyn_count is large too. > > I can increase my net.inet.ip.fw.dyn_max but the new limit will > simply be reached later on. Try using 'limit' rather than the unlimited 'keep-state' for inbound dynamic connections to your server/s. eg, derived from ipfw(8): ipfw add allow tcp from any to me 80 setup limit src-addr 4 ".. can be placed on a server to make sure that a single client does not use more than 4 simultaneous connections." You could add 'in recv $ext_if' to avoid limiting internal clients. > I currently get around this with a cronjob that sets > net.inet.ip.fw.dyn_keepalive to 0 for just less than 5 minutes > every night. If I leave it at 0 for longer or indefinitely then > idle ssh sessions and the like are dropped. This works fine for > me but it looks like there's some bug with net.inet.ip.fw.dyn_keepalive=1? > Or with Apache? Limiting the number of source connections per source address to what apache is happy to deal with, you mightn't need to fuss with that? cheers, Ian > I'm using 8.1-STABLE, GENERIC kernel. Experienced the same behaviour > on 8.0-RELEASE, but not on 6.1-RELEASE where I had a similar setup. I > have a KeepAliveTimeout of 4 in Apache (2.2.16).
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