Re: [Divert] Basic questions about functionaly of divert sockets

[Ilia B. <ib...@pi...>]

Victor Foitzik wrote:

> Hello folks,
>
> I am currently working on a divert based filtering software for HTTP requests.
> This should work this way:
>
> SERVER -> DIVERT -> CLIENT
>
> The software catches the entire HTTP stream from a server destined for a certain
> client and filters it based on several criterias. The main aspect is, that this
> is completely transparent, the server sees request coming from the client and
> vice versa, the software between is completely invisible. In order to achieve
> this, src and dest ip are corrected, but also sequence numbers, etc. Since some
> of the HTTP data must be cached before sending it to the client, fake ACK
> packets are sent to the server.
>
> Now my questions:
> 1. What exactly happens to packets reinserted into the TCP stack which cannot be
>    delivered to the client ? Do I have to resend them manually, or does the TCP
>    stack take care for this ?

The packets reinserted into the IP stack behave like any other packets. If they
cannot
be delivered, regular TCP mechanisms are envolved (sending an RST and all that).

> 2. Is the order of inserted packets relevant ?

For TCP it is. Best if you reinsert in the same order you receive them.

>

> 3. Does anyone know of a similar software ?
>

Don't know.

>
> Thank you for your time
>
> Victor Foitzik
>
> -------------------------------------------------------------------------
> Divert Sockets for Linux List
> mailto:di...@li...
> http://www.anr.mcnc.org/~divert
> -------------------------------------------------------------------------

Remember: divert sockets are an IP mechanism - they don't care about
the transport protocol in the IP datagrams, so its up to you to insure
everything is sane.

-ilia


--
-------------------------------------+----------------------
Ilia Baldine, PhD                    | ib...@an...
Network Research Engineer,           | ph#:(919)248-1847
Advanced Networking Research, MCNC   | FAX:(919)248-1455
http://people.anr.mcnc.org/~ibaldin  |
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"I used to think the brain was the most important part
of the body, but then I realized who was telling me that."
                        -Emo Philips
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