I've recently upgraded my home firewall from FreeBSD 5.4 (IPfilter
v3.4.35) to FreeBSD 6.2-RELEASE (IPfilter v4.1.13) and am now having
problems with IPfilter randomly blocking packets on both the internal
and external interfaces.

This morning, I had a couple of ssh connections from an internal host
to my firewall drop out with the following logged:
Feb 17 08:50:00 fwall sshd[13919]: fatal: Write failed: Network is unreachable
Feb 17 08:50:00 fwall sshd[13747]: fatal: Write failed: Network is unreachable
Feb 17 08:50:01 fwall ipmon[13795]: 08:50:00.888727 fxp1 @20:4 b 
192.168.234.1,22 -> 192.168.234.164,51955 PR tcp len 20 468 -AP 457306297 
554349920 33304 OUT
Feb 17 08:50:01 fwall ipmon[13795]: 08:50:00.904192 fxp1 @20:4 b 
192.168.234.1,22 -> 192.168.234.164,51235 PR tcp len 20 180 -AP 1754826132 
2941552523 33304 OUT

Both connections had been up and exchanging data for a couple of
minutes and then died for no obvious reason.  I've had similar
dropouts on FTP and HTTP transfers.  I'm also seeing ntpd report
occasional "Network is unreachable" problems on the external interface
- which look like the same problem.

Can anyone offer any suggestions.

My ipf rules follow.  fxp0 is the external interface and fxp1
(192.168.234.1/24) is the internal interface.

pass out quick on lo0 all
block out quick on fxp1 all head 20
pass out quick on fxp1 proto udp from 192.168.234.1/32 to 192.168.234.0/24 port 
= ntp group 20
pass out quick on fxp1 proto tcp from 192.168.234.1/32 to 192.168.234.0/24 port 
= ssh flags S/FSRPAU keep state group 20
pass out quick on fxp1 proto tcp from 192.168.234.1/32 to 192.168.234.0/24 port 
= smtp flags S/FSRPAU keep state group 20
block out log quick all group 20
block out quick on fxp0 all head 21
block out quick on fxp0 from 192.168.0.0/16 to any group 21
block out quick on fxp0 from 172.16.0.0/12 to any group 21
block out quick on fxp0 from 10.0.0.0/8 to any group 21
block out quick on fxp0 from 127.0.0.0/8 to any group 21
block out quick on fxp0 from 0.0.0.0/8 to any group 21
block out quick on fxp0 from 169.254.0.0/16 to any group 21
block out quick on fxp0 from 192.0.2.0/24 to any group 21
block out quick on fxp0 from 204.152.64.0/23 to any group 21
block out quick on fxp0 from 224.0.0.0/3 to any group 21
pass out quick on fxp0 proto tcp from any to any flags S/FSRPAU keep state keep 
frags group 21
pass out quick on fxp0 proto udp from any to any keep state keep frags group 21
pass out quick on fxp0 proto icmp from any to any keep state group 21
block out log quick all group 21
block out log all
pass in quick on lo0 all
block in quick on fxp1 all head 10
pass in quick on fxp1 proto tcp from any to any flags S/FSRPAU keep state keep 
frags group 10
pass in quick on fxp1 proto udp from any to any keep state keep frags group 10
pass in quick on fxp1 proto icmp from any to any keep state keep frags group 10
block in log quick all group 10
block in quick on fxp0 all head 11
block in quick on fxp0 from 192.168.0.0/16 to any group 11
block in quick on fxp0 from 172.16.0.0/12 to any group 11
block in quick on fxp0 from 10.0.0.0/8 to any group 11
block in quick on fxp0 from 127.0.0.0/8 to any group 11
block in quick on fxp0 from 0.0.0.0/8 to any group 11
block in quick on fxp0 from 169.254.0.0/16 to any group 11
block in quick on fxp0 from 192.0.2.0/24 to any group 11
block in quick on fxp0 from 204.152.64.0/23 to any group 11
block in quick on fxp0 from 224.0.0.0/3 to any group 11
block in quick on fxp0 from any to 224.0.0.0/3 group 11
block in quick on fxp0 proto udp from any to any port = netbios-ns group 11
block in quick on fxp0 proto icmp from any to any icmp-type echo group 11
pass in quick on fxp0 proto tcp from any to 192.168.234.124/32 port = ssh flags 
S/FSRPAU keep state keep frags group 11
pass in quick on fxp0 proto tcp from any to 192.168.234.124/32 port = http 
flags S/FSRPAU keep state keep frags group 11
block in log quick all group 11
block in log all

-- 
Peter Jeremy

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