netdev - Re: [PATCH] Fix possible double-ack w/ user dma

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Message-Id: <DCA6A06C-CE49-453F-91D8-23A6C4187FD6@engin.umich.edu>
Date:	Sun, 28 Sep 2008 22:45:51 -0500
From:	Ali Saidi <saidi@...in.umich.edu>
To:	netdev@...r.kernel.org
Subject: Re: [PATCH] Fix possible double-ack w/ user dma

I attached a broken patch. This one is correct, although there are  
probably other ways to fix the issue.

Ali



Download attachment "fix_double_ack.diff" of type "application/octet-stream" (373 bytes)


On Sep 28, 2008, at 9:13 PM, Ali Saidi wrote:

> When TCP receive copy offload is enabled it's possible that   
> tcp_rcv_established() will cause two acks to be sent for a single  
> packet. In the case that a tcp_dma_early_copy() is successful,  
> copied_early is set to true which causes tcp_cleanup_rbuf() to be  
> called early which can send an ack. Further along in  
> tcp_rcv_established(),  __tcp_ack_snd_check() is called and will  
> schedule a delayed ACK. If no packets are processed before the  
> delayed ack timer expires the packet will be acked twice.
>
> Attached is a patch that addresses the problem.
>
> Ali
>
>
>
> <fix_double_ack.diff>