netdev - Re: [PATCH] netpoll: fix netpoll_send

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Message-ID: <jra6c7$tj4$1@dough.gmane.org>
Date:	Wed, 13 Jun 2012 13:59:35 +0000 (UTC)
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	netdev@...r.kernel.org
Subject: Re: [PATCH] netpoll: fix netpoll_send_udp() bugs

On Wed, 13 Jun 2012 at 05:30 GMT, Eric Dumazet <eric.dumazet@...il.com> 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.
>

Reviewed-by: Cong Wang <xiyou.wangcong@...il.com>

Need to apply to -stable?

Thanks.

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