Messages in this thread | | | Subject | Re: Questions about Packet Filter | Date | Thu, 21 May 1998 10:10:20 +0200 (MET DST) | From | (Rogier Wolff) |
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Alan Cox wrote: > > > 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.
But wouldn't you be able to make your application feed the packet that filtered through the BPF back to the kernel, modified as needed?
There is a kernel/userland network packet interface that I've never looked into. If worse comes to worse, you'll have to open a pty, and shove the packet, ppp encapsulated onto that....
Roger.
-- If it's there and you can see it, it's REAL |___R.E.Wolff@BitWizard.nl | If it's there and you can't see it, it's TRANSPARENT | Tel: +31-15-2137555 | If it's not there and you can see it, it's VIRTUAL |__FAX:_+31-15-2138217 | If it's not there and you can't see it, it's GONE! -- Roy Wilks, 1983 |_____|
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