netdev - Re: [PATCH v2] tipc: prevent dropped connections due to rcvbuf overflow

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Date:	Thu, 04 Oct 2012 15:55:03 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	erik.hugne@...csson.com
Cc:	netdev@...r.kernel.org, jon.maloy@...csson.com,
	ying.xue@...driver.com, paul.gortmaker@...driver.com,
	tipc-discussion@...ts.sourceforge.net
Subject: Re: [PATCH v2] tipc: prevent dropped connections due to rcvbuf
 overflow

From: <erik.hugne@...csson.com>
Date: Thu, 4 Oct 2012 17:00:43 +0200

> From: Erik Hugne <erik.hugne@...csson.com>
> 
> When large buffers are sent over connected TIPC sockets, it
> is likely that the sk_backlog will be filled up on the
> receiver side, but the TIPC flow control mechanism is happily
> unaware of this since that is based on message count.
> 
> The sender will receive a TIPC_ERR_OVERLOAD message when this occurs
> and drop it's side of the connection, leaving it stale on
> the receiver end.
> 
> By increasing the sk_rcvbuf to a 'worst case' value, we avoid the
> overload caused by a full backlog queue and the flow control
> will work properly.
> 
> This worst case value is the max TIPC message size times
> the flow control window, multiplied by two because a sender
> will transmit up to double the window size before a port is marked
> congested.
> We multiply this by 2 to account for the sk_buff and other overheads.
> 
> Signed-off-by: Erik Hugne <erik.hugne@...csson.com>

Applied.
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