From owner-freebsd-hackers  Wed Mar 31 10:26:11 1999
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Date: Wed, 31 Mar 1999 10:26:31 -0800
From: Tom Brown <tomb@heliox.com>
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To: Christopher Sedore <cmsedore@mailbox.syr.edu>
Cc: Graham Wheeler <gram@cdsec.com>, hackers@FreeBSD.ORG
Subject: Re: How do I write to the /dev/bpf0 interface?
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So my supposition that I could write to it like any other file handle
was correct ? 


So I can just write the following to the interface for example:


ddddddddddddXXXXXXXXXXXXiiiiiiiiiiiiiiiiiiiiiiiiiii.....
d=destination address
X=don't care
i=information 

Bash# ethergenerator.pl>/dev/bpf0

Is that correct?

What happens if I want to put in a source MAC address?

You also mentioned that it might be a bug with 2.2.8, which
combination's of card / operating systems might work?

Thanks again for your time.

Tom Brown

Christopher Sedore wrote:
> 
> On Wed, 31 Mar 1999, Graham Wheeler wrote:
> 
> > Christopher Sedore wrote:
> > >
> > > On Wed, 31 Mar 1999, Graham Wheeler wrote:
> > >
> > > > Tom Brown wrote:
> > > >
> > > > > Can anyone please tell me how to post a packet onto my LAN via this
> > > > > interface.
> > > >
> > > > You should just be able to write the frame. Make sure everything is in
> > > > network-byte order. You needn't put in a source Ethernet address as that
> > > > will get filled in, but you do need to put in a destination.
> > >
> > > Note that this is probably a bug in the bpf implementation.  BPF/the
> > > kernel shouldn't be messing with the packet on a write to a bpf
> > > descriptor.  I've filed a bug report (with patch) that addresses this.
> > >
> >
> > It probably isn't the bpf code that is doing this, but the NIC driver
> > code...
> 
> Actually, its a cooperative effort by bpfwrite() and ether_output().
> 
> -Chris


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