OpenBSD's pf and traffic

[Peter N. M. Hansteen]

"Eugene M. Minkovskii" <emin at mccme.ru> writes:

> block in log on $ext_ip inet from any to $ext_ip label $ext_ip
> pass  in     on $ext_ip inet from any to $ext_ip port 22 keep sate
>
> As you can see, ssh packets match to all rule and pass in because
> last rule win. Does it mean, that I can't see ssh's packet using
> command
> # pfctl -sl

here you label the blocked packets but not the ones you pass, which
means your ssh packets would count toward the packets passed counter only.

> And if I use
>
> block in log on $ext_ip inet from any to $ext_ip label $ext_ip
> pass  in     on $ext_ip inet from any to $ext_ip port 22 keep sate label $ext_ip
>
> ... I see label twice ?

No. But both rules would increment the $ext_ip counter, which means that
your $ext_ip counter would be essentially packet totals. Last matching
rule wins (with state instead of sate it would work), so each packet
increments the relevant counters only once.

> Perhaps you know where I can find workable example of this?

Randal Schwartz has a nice article called "Monitoring Net Traffic with
OpenBSD's Packet Filter" at http://www.samag.com/documents/s=9053/sam0403j/0403j.htm

-- 
Peter N. M. Hansteen, member of the first RFC 1149 implementation team
http://www.blug.linux.no/rfc1149/ http://www.datadok.no/ http://www.nuug.no/
"First, we kill all the spammers" The Usenet Bard, "Twice-forwarded tales"