From owner-freebsd-net  Thu May  2  8:40:35 2002
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Date: Thu, 2 May 2002 08:28:42 -0700 (PDT)
From: Julian Elischer <julian@elischer.org>
To: Matt Impett <M.Impett@flarion.com>
Cc: "'freebsd-net@FreeBSD.org'" <freebsd-net@FreeBSD.org>
Subject: Re: source MAC address
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look at the following alternat ways to get data out of the kernel:

1/ ipfw + divert
2/ netgraph (can attach to sockets and interfaces and can provide sockets
and interfaces.. mix-n-match)


On Thu, 2 May 2002, Matt Impett wrote:

> Hello all,
> 
> I am implementing mobileIP in user space on freeBSD and was curious about
> something.  In order to do mobileIP IP address assignment, my process on
> freeBSD has to be able to receive an IP packet and learn the source MAC
> address that it came from (I am sure that the packet is only going one hop).
> I have been able to do this using the BPF device, but am concerned about a
> few things:
> 1)  When using the BPF device, the IP packet still goes to the IP stack, and
> since I am no longer listening on the UDP port number, a ICMP port
> unreachable is sent.  I guess I could us ip_fw to fix this.
> 2)  When using the BPF device, I am bypassing the IP stack.  Therefore, I am
> losing things like reassembly, IPSEC, etc..
> 
> Is there another way to get this info up to an application without using
> BPF?
> 
> Likewise, I also want to be able to force IP packets out to a particular MAC
> address, regardless of the IP destination address of the packet.  Once
> again, I know BPF can do this, but then I have similar concerns to the ones
> above.  For example, what do I set the IP ID field to??  If I accidentally
> match an ID field that the kernel has used previously, then reassembly could
> get confused on the end host.
> 
> thanks a lot,
> matt
> 
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