netdev - Re: [PATCH] netpoll: fix netpoll_send

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Message-ID: <20120613111854.GA14339@hmsreliant.think-freely.org>
Date:	Wed, 13 Jun 2012 07:18:54 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Bogdan Hamciuc <bogdan.hamciuc@...escale.com>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH] netpoll: fix netpoll_send_udp() bugs

On Wed, Jun 13, 2012 at 07:30:21AM +0200, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> Bogdan Hamciuc diagnosed and fixed following bug in netpoll_send_udp() :
> 
> "skb->len += len;" instead of "skb_put(skb, len);"
> 
> Meaning that _if_ a network driver needs to call skb_realloc_headroom(),
> only packet headers would be copied, leaving garbage in the payload.
> 
> However the skb_realloc_headroom() must be avoided as much as possible
> since it requires memory and netpoll tries hard to work even if memory
> is exhausted (using a pool of preallocated skbs)
> 
> It appears netpoll_send_udp() reserved 16 bytes for the ethernet header,
> which happens to work for typicall drivers but not all.
> 
> Right thing is to use LL_RESERVED_SPACE(dev)
> (And also add dev->needed_tailroom of tailroom)
> 
> This patch combines both fixes.
> 
> Many thanks to Bogdan for raising this issue.
> 
> Reported-by: Bogdan Hamciuc <bogdan.hamciuc@...escale.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Tested-by: Bogdan Hamciuc <bogdan.hamciuc@...escale.com>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: Neil Horman <nhorman@...driver.com>
Reviewed-by: Neil Horman <nhorman@...driver.com>

> 
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