26.6 IPFW: Couple things

Brett Proctor brettproctor at gmail.com
Fri Apr 14 11:42:55 UTC 2006


First off, let me say thank you to whoever is responsible for writing
all this. Really helpfull stuff. I implemented the NAT-ed statefull
ruleset (the last example) and found a bug I believe. The offending
line:
# Allow out access to my ISP's Domain name server.
# x.x.x.x must be the IP address of your ISP's DNS
# Dup these lines if your ISP has more than one DNS server
# Get the IP addresses from /etc/resolv.conf file
$cmd 020 $skip tcp from any to x.x.x.x 53 out via $pif setup keep-state
the TCP part should be UDP I believe. In some previous sections it
seemed it listed both TCP and UDP rules for DNS, but I believe that
DNS only uses TCP.

Also, is this a bit logically inconsistent? (Very last line)
# This is skipto location for outbound stateful rules
$cmd 800 divert natd ip from any to any out via $pif
$cmd 801 allow ip from any to any

# Everything else is denied by default
# deny and log all packets that fell through to see what they are
$cmd 999 deny log all from any to any

Isn't it impossible for anything to get past rule 801? Doesn't it
essentially make it a default allow-all policy? If i'm not mistaken
shouldn't rule 999 be moved and changed to 799?

Thanks again for all this. The handbook is truly an invaluable resource.



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