Watching /var/log/pflog grow

cpghost cpghost at
Tue Nov 4 11:12:43 PST 2008

How can I watch /var/log/pflog grow with tcpdump, "tail -f" style?

This won't work:
  $ tail -f /var/log/pflog | tcpdump -n -s 116 -r -
because tail doesn't start at the right location.

Using a blocksize (-b) with tail may also not be right,
because the captured packets are not the same size.

This seems to work:
  $ tcpdump -n -s 116 -i pflog0
but now, both tcpdump and pflogd are competing for the same
interface pflog0.

I'm afraid that in the latter case, every packet will be
  EITHER logged by pflogd
  XOR    displayed by tcpdump.
Is that so?

If yes, /var/log/pflog would be incomplete, because some packets
would have been snatched away from pflog0 by tcpdump, before
pflogd ever got a chance to read them out.

Is there a way to watch /var/log/pflog grow, while
still making sure that pflogd logs EVERY packet that appears
on the pflog0 interface? How?


Cordula's Web.

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