Messages in this thread Patch in this message |  | | Date | Thu, 16 Nov 2000 01:42:14 +0200 (IST) | From | Dan Aloni <> | Subject | Re: (iptables) ip_conntrack bug? |
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On Thu, 16 Nov 2000, Dan Aloni wrote:
> On Wed, 15 Nov 2000, Guus Sliepen wrote: > > > > I was DDoS'd today while away and came home to find the firewall unable to > > > do anything network related (although my connection to irc was still > > > working oddly). a quick dmesg showed the problem. > > > ip_conntrack: maximum limit of 2048 entries exceeded > > [...] > > > > I have also seen this happen on a box which ran test9. Apparently because of > > it's long uptime, because the logs should no signs of an attack. > > > > I guess conntrack forgets to flush some entries? Or maybe there is no way it can > > recover from a full conntrack table? Is it maybe necessary to make the maximum > > size a configurable option? Or a userspace conntrack daemon like the arpd? > > >From reading the sources I got the impression that the use count of > the ip_conntrack struct isn't decremented properly. This causes > destroy_conntrack() not to free ip_conntrack's - which results allocation > until the maximum (ip_conntrack_max), and failing to allocate new ones.
I think I got something, icmp_error_track() increases the use count (calling ip_conntrack_find_get()) when it returns with no error (not NULL). Whoever calls icmp_error_track() and gets a valid pointer to ip_conntrack, must call ip_conntrack_put() - look at ip_conntrack_in(), line 685, the pointer is just used in a boolean expression without calling ip_conntrack_put(). I'm not sure if other places needed fixing, but anyway try this patch:
--- linux-2.4.0-test11-pre5/net/ipv4/netfilter/ip_conntrack_core.c Tue Nov 14 09:56:16 2000 +++ linux/net/ipv4/netfilter/ip_conntrack_core.c Thu Nov 16 01:35:13 2000 @@ -682,8 +682,10 @@ /* It may be an icmp error... */ if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP - && icmp_error_track(*pskb, &ctinfo, hooknum)) + && (ct = icmp_error_track(*pskb, &ctinfo, hooknum))) { + ip_conntrack_put(ct); return NF_ACCEPT; + } if (!(ct = resolve_normal_ct(*pskb, proto,&set_reply,hooknum,&ctinfo))) /* Not valid part of a connection */ -- Dan Aloni dax@karrde.org
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