netdev - Re: [PATCH net-next] mpls: allow TTL propagation to/from IP packets to be configured

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Message-ID: <bffe7633-9285-bd2a-8cfa-3b0918ca62ce@cumulusnetworks.com>
Date:   Thu, 2 Feb 2017 21:02:47 -0700
From:   David Ahern <dsa@...ulusnetworks.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Robert Shearman <rshearma@...cade.com>,
        roopa <roopa@...ulusnetworks.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] mpls: allow TTL propagation to/from IP packets
 to be configured

On 2/2/17 8:21 PM, Eric W. Biederman wrote:
> 
> My brain is mostly elswhere right now so I don't have an implementation
> on how it should be implemented.   However Linux fundamentally gets used
> interesting ways, and if we don't implement the option as per mpls exit
> now someone will come along and need to do the work later.
> 
> Perhaps it will only be used with hard coded static configurations, and
> it is fundamentally a per tunnel property.
> 
> It will be less work to maintain, and the code will run faster in the
> long run if we don't have two code paths to maintain.

I can see the argument for per-tunnel knobs, but looking at ios and nx-os docs it seems appropriate to have a global knob as well. In that regards having sysctl knobs solves the global setting and when/if needed we can add MPLS_IPTUNNEL_ZZZZZ encap attributes for the per-tunnel settings.

Does that seem reasonable?