Re: [PATCH v4 bluetooth-next] 6lowpan: Use pskb_expand_head in IPHC decompression.

[Martin Townsend <martin.townsend@xsilon.com>]

Hi  Alex,

I completely missed it, unless reassembly can result in a shared skb? can you confirm that it doesn't then I'll remove the line.

Thanks, Martin.

On 08/10/14 15:59, Alexander Aring wrote:
> Hi Martin,
>
> On Wed, Oct 08, 2014 at 02:46:55PM +0100, Martin Townsend wrote:
>> Currently there are potentially 2 skb_copy_expand calls in IPHC
>> decompression.  This patch replaces this with one call to
>> pskb_expand_head.  It also checks to see if there is enough headroom
>> first to ensure it's only done if necessary.
>> As pskb_expand_head must only have one reference the calling code
>> now ensures this.
>>
>> Signed-off-by: Martin Townsend <martin.townsend@xsilon.com>
> ...
>> --- a/net/ieee802154/6lowpan_rtnl.c
>> +++ b/net/ieee802154/6lowpan_rtnl.c
>> @@ -537,6 +537,11 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
>>  		if (ret == NET_RX_DROP)
>>  			goto drop;
>>  	} else {
>> +		/* Decompression may use pskb_expand_head so no shared skb's */
>> +		skb = skb_share_check(skb, GFP_ATOMIC);
>> +		if (!skb)
>> +			goto drop;
>> +
> We do this already at [0], is it really necessary do it here again?
>
> This ensures that 6lowpan header replacing doesn't affect the af_802154
> implementation.
>
> - Alex
>
> [0] http://lxr.free-electrons.com/source/net/ieee802154/6lowpan_rtnl.c#L466
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