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Re: [lwip-users] portscan

From: Kieran Mansley
Subject: Re: [lwip-users] portscan
Date: Thu, 02 Jul 2009 12:59:07 +0100

On Thu, 2009-07-02 at 10:52 +0200, Bernhard 'Gustl' Bauer wrote:

> - a ethernet tx throttles back if the connected rx has misses

Ethernet doesn't back-off, it just tries its best and drops things if
there is too much for the network to handle, but TCP will back-off if it
detects loss or congestion to try and prevent the network from being
overloaded.  Your driver shouldn't rely on this though as there are
other protocols that don't back-off, and TCP doesn't always get it

> - a packet received by a rx has to be processed under all circumstances

At what level are you referring to the rx?  If by the driver, no, it can
drop packets if it wants to as TCP will cope and deal with the
retransmissions.  If it can avoiding dropping, that's a good idea as TCP
retransmissions are expensive and time consuming so will affect the
bandwidth achieved.

If by "received an rx" you mean after TCP has acknowledged the packet,
then yes, it should do its best to deliver to the application, or reset
the connection if there is some failure that means it can't (e.g.
application has closed the socket).

If by "received an rx" you mean the application, well it can do whatever
it likes assuming it's prepared to put up with the consequences of not
processing receives.

Hope that helps,


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