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Re: [lwip-users] Establishing TCP Connection after power-up

From: farid mahini
Subject: Re: [lwip-users] Establishing TCP Connection after power-up
Date: Mon, 21 Feb 2011 12:58:18 -0800 (PST)

It worked. Thank you Simon.
What else does ARP_QUEUEING activate/do besides buffering SYN message?

From: "address@hidden" <address@hidden>
To: Mailing list for lwIP users <address@hidden>
Sent: Mon, February 21, 2011 1:10:33 PM
Subject: Re: [lwip-users] Establishing TCP Connection after power-up

farid mahini wrote:
> Question:  Since the SYN message has both source and destination addresses (IP and MAC), why does MyServer request it? Wouldn't it get added to ARP table as the SYN message travels up the stack to TCP layer.
You can configure lwIP to behave like that, but it's not a good idea to do so as it
a) is a security issue and
b) can have a large performance impact as every incoming packet leads to scanning the ARP table for a hit to update.

You should enable ARP_QUEUEING instead (define it to 1 in lwipopts.h) so that the outgoing SYN is buffered by lwIP until the ARP response is received. 1.4.0rc2 does this automatically.


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