Torrent clients bring pf-based firewall to its knees...?

Peter C. Lai peter at
Fri Jul 24 21:18:15 UTC 2009

If only a reboot solves the problem sounds like a kernel problem?
mbuf leakage?

On 2009-07-24 04:56:11PM -0400, Mike Edenfield wrote:
> I've recently begun running a torrent client after hours on a PC sitting 
> behind our firewall (7.2-STABLE using pf).  I have added a 'rdr' rule to 
> redirect incoming traffic to the client PC from the firewall, and as far as 
> the client is concerned everything is fine.
> However, after a short period of torrent activity, the machine running the 
> firewall becomes extremely slow and lagged for all network traffic, but 
> appears to be operating fine locally.  Remote connections via ssh become 
> extremely unresponsive, and eventually connections start timing out, but 
> when logged in at the console, there doesn't appear to be any problem.  
> Running tcpdump does not show nusually high volume of traffic, no more than 
> I see during normal activity during the day.  The volume and length of 
> connections doesn't seem to matter much -- trying to copy a BSD or Linux 
> DVD with hundreds of connections breaks just as quickly as much smaller 
> torrents with a handful of peers.
> I know there are some cheap NAT-ing routers that get in trouble with 
> torrents because of the heavy volume of state rules required, but I've 
> never heard of anything like that being present in pf.  And I've used 
> torrent clients at home behind a pf firewall with no issues, but not on 
> this specific version of the FreeBSD.
> I've tried shutting down the torrent client, clearing out the state and nat 
> rules with pfctl, adding drop rules to reject the torrent traffic, and even 
> bringing the network adapter down completely, but only a physical reboot 
> (combined with not running the client ever again) seems to solve anything.
> Has anyone experienced this kind of problem before?  Or alternatively, is 
> there some way besides tcpdump and top (neither of which show anything 
> unusual) that I can tell what exactly the machine is doing that's causing 
> the network lag?
> --Mike
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Peter C. Lai                 | Bard College at Simon's Rock
Systems Administrator        | 84 Alford Rd.
Information Technology Svcs. | Gt. Barrington, MA 01230 USA
peter AT     | (413) 528-7428

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