Date: Tue, 17 Sep 2002 23:48:01 -0400 From: dfolkins <dfolkins@comcast.net> To: freebsd-security@FreeBSD.ORG Subject: Re: Unexpected keep state behaviour in ipfw Message-ID: <001601c25ec6$2fd4dc90$0a00a8c0@groovy3xp> References: <20020915224154.GD495@gsmx07.alcatel.com.au> <001a01c25e17$39edcde0$0a00a8c0@groovy3xp> <20020917210004.GW495@gsmx07.alcatel.com.au>
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> net.inet.ip.fw.dyn_ack_lifetime is a tradeoff between keeping active > connections alive and minimising the impact of massive numbers of > dynamic rules. I also feel that 300 seconds is too short (note that > IPFilter uses 120 hours, which I think is far too long). My problem > is that the connections are being dropped after less than > net.inet.ip.fw.dyn_ack_lifetime seconds of idle time. I have tried > juggling net.inet.tcp.keepidle, net.inet.tcp.keepintvl and > net.inet.ip.fw.dyn_ack_lifetime so that the latter is longer than > the former (in ipfw) and this still didn't work. It would appear > that the dynamic rule timers are never being reset. > > >as to why your ssh connection stays alive even through the night - i > >suspect that is because your ssh server on your firewall has a > >configuration setting that makes it send keep-alives, i.e. your > >clientaliveinterval in sshd_config is set to some value which is less > >than your net.inet.ip.fw.dyn_ack_lifetime value. > > Nope. I'm using the default ClientAliveInterval value (ie disabled). > > Based on comments in another thread here, I suspect the underlying > problem is that ipfw dynamic rules don't work with ipnat. (Though > I don't understand why - ipnat should be invisible to ipfw). My > ssh connectins remain working courtesy of either normal or ipfw2 > keepalives (since that connection isn't NAT'd). > well, given this description, i guess maybe you are right, and its having problems with ipnat. i had some problems with natd/ipfw myself (cf recent thread in -security), so its possible ipfw doesnt behave well with ipnat either. maybe the solution is to switch to ipfilter after all... sorry i couldnt be more helpful. -- dfolkins To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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