netdev - Re: [PATCHv2 iproute2 net-next] tc: m_mirred: Fix parsing of 'index' optional argument

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Date:   Thu, 27 Oct 2016 17:22:39 +0300
From:   Shmulik Ladkani <shmulik.ladkani@...il.com>
To:     Phil Sutter <phil@....cc>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        Jamal Hadi Salim <jhs@...atatu.com>, netdev@...r.kernel.org
Subject: Re: [PATCHv2 iproute2 net-next] tc: m_mirred: Fix parsing of
 'index' optional argument

Hi Phil,

On Thu, 27 Oct 2016 11:46:33 +0200, phil@....cc wrote:
> According to the action's help text (and the man page which is based
> upon that), this behaviour is perfectly fine:
> 
> | Usage: mirred <DIRECTION> <ACTION> [index INDEX] <dev DEVICENAME>
> 
> So first argument *must* be the direction, second one *must* be the
> action, then an optional index and the last one *must* be the interface.

There is an inconsistency betweem man/help and code.

Actual code, since first committed, attempts to parse "index" as 1st
argument (without success), see parse_mirred():

	if (matches(*argv, "egress") == 0 || matches(*argv, "index") == 0) {
		int ret = parse_egress(a, &argc, &argv, tca_id, n);

> While I don't see a problem with changing that (apart from that I don't
> think it's necessary)

Not "changing" per-se, but rather "fixing", at least according code
author's intention :)

As I suggested in the notes part of the commit log,

>> An alternative solution: banning "index" as 1st argument in parse_mirred

I ok with removing the code trying to support "index" as 1st argument as
well.
I only assumed one might want this behaviour due to intention expressed
by original code.