On 12/12/05, Graham Menhennitt <[EMAIL PROTECTED]> wrote:
> I got the following output from "ipfw show" in my daily security run output 
> email.
>
> +++ /tmp/security.yri47lgA      Mon Dec 12 03:01:45 2005
> +00522  3530 1204158 deny ip from 10.0.0.0/8 to any via sis1
> +02522    18     784 deny tcp from any to any in via sis1 setup
> +65530     0       0 deny ip from any to any
> +65535     2     688 deny ip from any to any
>
> Could somebody please explain to me how those packets got past rule 65530 to 
> be stopped by (the identical) rule 65535? The ipfw rules have not changed 
> since the machine rebooted. The only explanation I have is that the packets 
> arrived between the time when the machine started accepting incoming packets 
> and when the rules were loaded in /etc/rc.d/ipfw.
>
> If that's the case, it's a pretty good argument for defaulting to rejecting 
> packets. Didn't somebody here suggest that this wasn't really necessary a few 
> weeks ago (something to do with using pf)?
>
This is exactly what compiling your kernel with IPFIREWALL does, it
defaults to denying packets by default.  You can change this behavior
by adding IPFIREWALL_DEFAULT_TO_ACCEPT but is strongly discouraged.

See sys/conf/NOTES (
http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/conf/NOTES?rev=1.1337&content-type=text/x-cvsweb-markup
)

for pf you need to add IPFILTER_DEFAULT_BLOCK to block packets by default.

Scot
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