netdev - Re: [PATCH v3 net-next 2/2] Special handling for IP & MPLS.

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Date:   Mon, 18 Nov 2019 12:30:11 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Martin Varghese <martinvarghesenokia@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>, corbet@....net,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        scott.drennan@...ia.com, Jiri Benc <jbenc@...hat.com>,
        martin.varghese@...ia.com
Subject: Re: [PATCH v3 net-next 2/2] Special handling for IP & MPLS.

On Sat, Nov 16, 2019 at 12:45 AM Martin Varghese
<martinvarghesenokia@...il.com> wrote:
>
> From: Martin Varghese <martin.varghese@...ia.com>
>
> Special handling is needed in bareudp module for IP & MPLS as they support
> more than one ethertypes.
>
> MPLS has 2 ethertypes. 0x8847 for MPLS unicast and 0x8848 for MPLS multicast.
> While decapsulating MPLS packet from UDP packet the tunnel destination IP
> address is checked to determine the ethertype. The ethertype of the packet
> will be set to 0x8848 if the  tunnel destination IP address is a multicast
> IP address. The ethertype of the packet will be set to 0x8847 if the
> tunnel destination IP address is a unicast IP address.
>
> IP has 2 ethertypes.0x0800 for IPV4 and 0x86dd for IPv6. The version field
> of the IP header tunnelled will be checked to determine the ethertype.

If using ipv6 dual stack, it might make more sense to use extended
mode with the ipv6 device instead of the ipv4 device.

Also, the term extended mode is not self describing. Dual stack as
term would be, but is not relevant to MPLS. Maybe "dual_proto"?

> diff --git a/Documentation/networking/bareudp.rst b/Documentation/networking/bareudp.rst
> index 2828521..1f01dfd 100644
> --- a/Documentation/networking/bareudp.rst
> +++ b/Documentation/networking/bareudp.rst
> @@ -12,6 +12,15 @@ The Bareudp tunnel module provides a generic L3 encapsulation tunnelling
>  support for tunnelling different L3 protocols like MPLS, IP, NSH etc. inside
>  a UDP tunnel.
>
> +Special Handling
> +----------------
> +The bareudp device supports special handling for MPLS & IP as they can have
> +multiple ethertypes.
> +MPLS procotcol can have ethertypes ETH_P_MPLS_UC  (unicast) & ETH_P_MPLS_MC (multicast).
> +IP proctocol can have ethertypes ETH_P_IP (v4) & ETH_P_IPV6 (v6).

proctocol -> protocol