netdev - Re: [PATCH net] Revert "vxlan: fix tos value before xmit"

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Date:   Wed, 5 Aug 2020 10:44:27 +0200
From:   Guillaume Nault <gnault@...hat.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     netdev@...r.kernel.org, Petr Machata <pmachata@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        David Ahern <dsahern@...nel.org>,
        Andreas Karis <akaris@...hat.com>
Subject: Re: [PATCH net] Revert "vxlan: fix tos value before xmit"

On Wed, Aug 05, 2020 at 10:41:31AM +0800, Hangbin Liu wrote:
> This reverts commit 71130f29979c7c7956b040673e6b9d5643003176.
> 
> In commit 71130f29979c ("vxlan: fix tos value before xmit") we want to
> make sure the tos value are filtered by RT_TOS() based on RFC1349.
> 
>        0     1     2     3     4     5     6     7
>     +-----+-----+-----+-----+-----+-----+-----+-----+
>     |   PRECEDENCE    |          TOS          | MBZ |
>     +-----+-----+-----+-----+-----+-----+-----+-----+
> 
> But RFC1349 has been obsoleted by RFC2474. The new DSCP field defined like
> 
>        0     1     2     3     4     5     6     7
>     +-----+-----+-----+-----+-----+-----+-----+-----+
>     |          DS FIELD, DSCP           | ECN FIELD |
>     +-----+-----+-----+-----+-----+-----+-----+-----+
> 
> So with
> 
> IPTOS_TOS_MASK          0x1E
> RT_TOS(tos)		((tos)&IPTOS_TOS_MASK)
> 
> the first 3 bits DSCP info will get lost.
> 
> To take all the DSCP info in xmit, we should revert the patch and just push
> all tos bits to ip_tunnel_ecn_encap(), which will handling ECN field later.
> 
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>

I guess an explicit
Fixes: 71130f29979c ("vxlan: fix tos value before xmit").
tag would help the -stable maintainers.

Apart from that,
Acked-by: Guillaume Nault <gnault@...hat.com>