Sending packets from within the kernel

Sending packets from within the kernel

[bp]

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Hello,

I am working on an kernel module which forwards TCP segments from one
interface to another (basic routing, no proxy or listener socket), but
which needs to be able to generate some segments completely independently
of the client<-->server data stream.  For example, when receiving a SYN
segment from the client, I want the module to be able to respond itself
with a SYN+ACK on behalf of the server (and drop the SYN).

I understand how silly this sounds.  Setting aside the reasoning and
pitfalls of such a desire, technically what is the best way to do it?  I've
reviewed the SYN_COOKIE and RST_COOKIE logic and it seems we must create a
dummy socket which is not attached to any inode.

Is there a cheaper way of accomplishing the same thing, assuming I don't
need to record any state for the endpoints?

Sincerely,
- -bp
- --
# bp at terran dot org
# http://www.terran.org/~bryan

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Re: Sending packets from within the kernel

[bert hubert]

On Fri, May 04, 2001 at 02:09:16PM -0700, bp@terran.org wrote:
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> 
> Hello,
> 
> I am working on an kernel module which forwards TCP segments from one
> interface to another (basic routing, no proxy or listener socket), but
> which needs to be able to generate some segments completely independently
> of the client<-->server data stream.  For example, when receiving a SYN
> segment from the client, I want the module to be able to respond itself
> with a SYN+ACK on behalf of the server (and drop the SYN).

The iptables MIRROR target does some stuff you might be able to use.

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