netdev - Re: [PATCH net] net: Clear local_df only if crossing namespace.

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Date:	Fri, 7 Feb 2014 14:49:20 -0800
From:	Pravin Shelar <pshelar@...ira.com>
To:	Pravin <pshelar@...ira.com>, David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"Templin, Fred L" <Fred.L.Templin@...ing.com>
Subject: Re: [PATCH net] net: Clear local_df only if crossing namespace.

On Fri, Feb 7, 2014 at 2:28 PM, Hannes Frederic Sowa
<hannes@...essinduktion.org> wrote:
> Hi!
>
> On Fri, Feb 07, 2014 at 02:12:38PM -0800, Pravin wrote:
>> --- a/net/core/skbuff.c
>> +++ b/net/core/skbuff.c
>> @@ -3905,12 +3905,13 @@ EXPORT_SYMBOL(skb_try_coalesce);
>>   */
>>  void skb_scrub_packet(struct sk_buff *skb, bool xnet)
>>  {
>> -     if (xnet)
>> +     if (xnet) {
>>               skb_orphan(skb);
>> +             skb->local_df = 0;
>> +     }
>>       skb->tstamp.tv64 = 0;
>>       skb->pkt_type = PACKET_HOST;
>>       skb->skb_iif = 0;
>> -     skb->local_df = 0;
>>       skb_dst_drop(skb);
>>       skb->mark = 0;
>>       secpath_reset(skb);
>
> I wonder if this should be the right behaviour for tunnels, which should just
> do fragmentation based on IP_DF, even if the packet originated locally from a
> socket which allowed local fragmentation (inet->pmtudisc < IP_PMTUDISC_DO).
>
This is not about tunneling, skb_scrub_packet() is generic function
which should not reset local_df on all packets.

We can have separate discussion about use of local_df and tunneling in
another thread.
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