netdev - Re: [PATCH] netpoll: Fix skb tail pointer in netpoll_send

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Message-ID: <1339508049.22704.143.camel@edumazet-glaptop>
Date:	Tue, 12 Jun 2012 15:34:09 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Bogdan Hamciuc <bogdan.hamciuc@...escale.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH] netpoll: Fix skb tail pointer in netpoll_send_udp()

On Tue, 2012-06-12 at 15:15 +0200, Eric Dumazet wrote:
> On Tue, 2012-06-12 at 14:22 +0200, Eric Dumazet wrote:

> > Hmm, real question is why skb_realloc_headroom() is even necessary...
> > 
> > I suspect we need to reserve more bytes.
> > 
> > 	total_len = ip_len + ETH_HLEN + NET_IP_ALIGN + NET_SKB_PAD;
> > 
> > or something like that ?
> > 
> > Which driver triggers the bug ?
> > 

In case you wonder why I try so hard to avoid the
skb_realloc_headroom() :

netpoll has complicated^Wspecial^Wnice skb cache, to make sure it can
work even if memory is exhausted.

But if we trigger skb_realloc_headroom() the whole thing is useless. 

Thanks


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