netdev - Re: iproute2: ip address add prefer keyword confusion

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Message-ID: <cee42fde-e171-6484-3091-fba1e65271df@gmail.com>
Date:   Thu, 27 May 2021 22:31:24 -0600
From:   David Ahern <dsahern@...il.com>
To:     Norman Rasmussen <norman@...mussen.co.za>, netdev@...r.kernel.org
Subject: Re: iproute2: ip address add prefer keyword confusion

On 5/27/21 2:58 PM, Norman Rasmussen wrote:
> commit 78d04c7b27cf ("ipaddress: Add support for address metric")
> added "priority" and "preference" as aliases for the "metric" keyword,
> but they are entirely undocumented.
> 
> I only noticed because I was adding addresses with a preferred
> lifetime, but I was using "pref" as the keyword. The metric code was
> added _above_ the lifetime code, so after the change "pref" matches
> "preference", instead of "preferred_lft".
> 
> Is there an existing way to deal with conflicts between keyword
> prefixes? Should "prefer" (or shorter) fail with a clear error
> instead? Should the metric code have been added below the lifetime
> code? Should it be moved or is it too late?
> 

It is in general a known problem with iproute2's use of "matches" to
allow shorthand commands.

The change where "pref" goes to metric vs "preferred_lft" was
unintentional. At this point (3 years after the commit) it would be hard
to revert the change.