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

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Date:	Sun, 28 Sep 2008 21:13:37 -0500
From:	Ali Saidi <saidi@...in.umich.edu>
To:	netdev@...r.kernel.org
Subject: [PATCH] Fix possible double-ack w/ user dma

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

Download attachment "fix_double_ack.diff" of type "application/octet-stream" (407 bytes)