netdev - Re: [PATCH net] ip_tunnel: allow to inherit from VLAN encapsulated IP frames

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Date:   Wed, 6 Jul 2022 09:07:36 +0200
From:   Matthias May <matthias.may@...termo.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     <netdev@...r.kernel.org>, <davem@...emloft.net>,
        <yoshfuji@...ux-ipv6.org>, <dsahern@...nel.org>,
        <edumazet@...gle.com>, <pabeni@...hat.com>
Subject: Re: [PATCH net] ip_tunnel: allow to inherit from VLAN encapsulated IP
 frames


On 06/07/2022 03:25, Jakub Kicinski wrote:
> Please make sure to CC folks pointed out by scripts/get_maintainer.pl
> 
> On Tue, 5 Jul 2022 16:54:42 +0200 Matthias May wrote:
>> Subject: [PATCH net] ip_tunnel: allow to inherit from VLAN encapsulated IP frames
> 
> net-next may be more appropriate, since this never worked.
> Unless it did, in which case we need a Fixes tag.
> 

I'm not aware that this ever worked. I tested back to 4.4.302.
Will send v2 to net-next.

>> The current code allows to inherit the TOS, TTL, DF from the payload
>> when skb->protocol is ETH_P_IP or ETH_P_IPV6.
>> However when the payload is VLAN encapsulated (e.g because the tunnel
>> is of type GRETAP), then this inheriting does not work, because the
>> visible skb->protocol is of type ETH_P_8021Q.
>>
>> Add a check on ETH_P_8021Q and subsequently check the payload protocol.
> 
> Do we need to check for 8021AD as well?
> 

Yeah that would make sense.
I can add the check for ETH_P_8021AD in v2.
Will have to find some hardware that is AD capable to test.

>> Signed-off-by: Matthias May <matthias.may@...termo.com>
>> ---
>>   net/ipv4/ip_tunnel.c | 21 +++++++++++++--------
> 
> Does ipv6 need the same treatment?

I don't think i changed anything regarding the behaviour for ipv6
by allowing to skip from the outer protocol to the payload protocol.
The previous code already
* got the TOS via ipv6_get_dsfield,
* the TTL was derived from the hop_limit,
* and DF does not exist for ipv6 so it doesn't check for ETH_P_IPV6.

BR
Matthias

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