Subject: Re: SIMPLEX interfaces, broadcast packets and BPF
To: Ignatios Souvatzis <>
From: Matt Thomas <>
List: tech-net
Date: 03/20/1997 11:53:25
In  <> , you wrote:

> While looking through old PRs, searching for something else:
> PR's 1313, 1693 and 2793 describe the same problem:
> Broadcast Packets sent to SIMPLEX interfaces are loopedback to
> ourselves through looutput(). If BPF listens to "lo", these packets
> are shown to it (possibly again), but with an incorrect header... BPF
> thinks they are lo packets, which get an artificial header containing
> only the address family ID, while in reality they have (if coming from
> Ethernet, depending on the address family) no header, or a 14-byte
> Ethernet header.

My drivers tap all input and output packets (including broadcasts)
so BPF will see all the packets, regardless if broadcasts are looped back
through lo0.

I'm having a hard time understanding what the problem, primarily because
I don't see a problem.
Matt Thomas               Internet:
3am Software Foundry      WWW URL:
Westford, MA              Disclaimer: I disavow all knowledge of this message