Re: Questions about Packet Filter

Alan Cox (
Thu, 21 May 1998 00:30:30 +0100 (BST)

> Are the BPF devices capable of "intercept" packages passing through
> them?

There are no BPF 'devices'. 2.1.x allows BPF filters on arbitary sockets
BPF does not write packets just test 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?

Not trivially.

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