Re: Packet manipulation in user space, drop/reinject modified packets

[Changli Gao <xiaosuo@gmail.com>]

On Sat, Apr 10, 2010 at 12:53 AM, Hamid Nassiby <h.nassiby@gmail.com> wrote:
> Hello,
>
> I'm working on a project which wants to port a Windows-based network
> protocol to Linux. The protocol works as a VPN/Firewall, on packets
> copied from Data-Link Layer to user space. In MS Windows
> WinpkFilter(C) does copying from kernel space (Data-Link layer)  to
> user space and then drops the original packet. In user space, our
> protocol does some operation on packet ( e.g. checks  the packet
> authority and/or encrypts/decrypts it, ...) and then injects the
> packet upward to application layer or downward or simply drops it. The injected
> modified packet may not be as the same size of original one.
>
> So our requirements are:
>
> 1-Capture each packet which is coming inside or going outside the
> computer in Data-link Layer.
> 2-Create a copy of the packet and drop the original one.
> 3-Copy of packet must be available in user space to be manipulated by
> our protocol.
> 4-After manipulation in user space, inject encrypted/decrypted version
> of the privileged (copy of) packets to the network or upward to the
> application layer.
>

Refer to: Documentation/networking/tuntap.txt

-- 
Regards，
Changli Gao(xiaosuo@gmail.com)
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