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Date:      Wed, 20 May 1998 13:48:10 -0700 (PDT)
From:      "L.C." <lc001@yahoo.com>
To:        Mike Smith <mike@smith.net.au>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: Questions about Packet Filter 
Message-ID:  <19980520204810.7890.rocketmail@send1c.yahoomail.com>

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Thanks a lot Mike.

Are these BPF alike devices capable of "intercept" packages passing
through them?

I mean is it possible that after it intercepts the outgoing package it
can modify the package contents(e.g. destination port) and inject into
NIC?
Or, modify the package contents when intercept the incoming packages
and poll them back to the higher level protocols or applications?

Carl




---Mike Smith <mike@smith.net.au> wrote:
>
> > Very appreciated if anybody can answer the questions:
> > 
> > 1. Does BPF support the monitoring of out going packages? how? I
know
> > it can monitor the receiving packages and directly write a new
package
> > into the specified network interface. How about the packages written
> > by other network or transport protocols?
> 
> Yes.  A simple test would have show you this.
> 
> > 2. Solaris seems having a similar soft-driver called "Network
> > Interface Tap". Anybody use that before? Can it monitoring both
> > incoming and outgoing packages?
> 
> Yes.
> 
> > 3. Any similar programming interface in the socket level? 
> 
> No.
> 
> > 4. How about in HP-UX, Linux, and AIX?
> 
> Most support something similar.
> 
> > I may need to port my code to these OSs.
> 
> Use libpcap, which provides a unified abstraction on top of most of 
> these platforms already.
> 
> -- 
> \\  Sometimes you're ahead,       \\  Mike Smith
> \\  sometimes you're behind.      \\  mike@smith.net.au
> \\  The race is long, and in the  \\  msmith@freebsd.org
> \\  end it's only with yourself.  \\  msmith@cdrom.com
> 
> 
> 
 
==

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