netdev - Re: [PATCH v4 net-next 6/9] net/sched: mqprio: allow per-TC user input of FP adminStatus

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Message-ID: <20230411170151.ii7onipewbd27uw6@skbuf>
Date:   Tue, 11 Apr 2023 20:01:51 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Gerhard Engleder <gerhard@...leder-embedded.com>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Ferenc Fejes <ferenc.fejes@...csson.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Roger Quadros <rogerq@...nel.org>,
        Pranavi Somisetty <pranavi.somisetty@....com>,
        Harini Katakam <harini.katakam@....com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>,
        Mohammad Athari Bin Ismail <mohammad.athari.ismail@...el.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Jacob Keller <jacob.e.keller@...el.com>,
        linux-kernel@...r.kernel.org, Ferenc Fejes <fejes@....elte.hu>,
        Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH v4 net-next 6/9] net/sched: mqprio: allow per-TC user
 input of FP adminStatus

On Wed, Apr 05, 2023 at 06:12:34PM -0700, Jakub Kicinski wrote:
> On Mon,  3 Apr 2023 13:34:37 +0300 Vladimir Oltean wrote:
> > +static int mqprio_parse_tc_entry(u32 fp[TC_QOPT_MAX_QUEUE],
> > +				 struct nlattr *opt,
> > +				 unsigned long *seen_tcs,
> > +				 struct netlink_ext_ack *extack)
> > +{
> > +	struct nlattr *tb[TCA_MQPRIO_TC_ENTRY_MAX + 1] = { };
> 
> nit: no need to clear it nla_parse*() zeros the memory

ok.

> > +	int err, tc;
> > +
> > +	err = nla_parse_nested(tb, TCA_MQPRIO_TC_ENTRY_MAX, opt,
> > +			       mqprio_tc_entry_policy, extack);
> > +	if (err < 0)
> > +		return err;
> > +
> > +	if (!tb[TCA_MQPRIO_TC_ENTRY_INDEX]) {
> > +		NL_SET_ERR_MSG(extack, "TC entry index missing");
> 
> Are you not using NL_REQ_ATTR_CHECK() because iproute can't actually
> parse the result? :(

I could use it though.. let's assume that iproute2 is "reference code"
and gets the nlattr structure right. Thus, the NLMSGERR_ATTR_MISS_NEST
would be of more interest for custom user programs.

Speaking of which, is there any reference example of how to use
NLMSGERR_ATTR_MISS_NEST? My search came up empty handed:
https://github.com/search?p=1&q=NLMSGERR_ATTR_MISS_NEST&type=Code

I usually steal from hostap's error_handler(), but it looks like it
hasn't gotten that advanced yet as to re-parse the netlink message to
understand the reason why it got rejected.

> 
> > +		return -EINVAL;
> > +	}
> > +
> > +	tc = nla_get_u32(tb[TCA_MQPRIO_TC_ENTRY_INDEX]);
> > +	if (*seen_tcs & BIT(tc)) {
> > +		NL_SET_ERR_MSG(extack, "Duplicate tc entry");
> 
> set attr in extack?

ok

> minor heads up - I'll take the trivial cleanup patch from Pedro
> so make sure you rebase:
> https://lore.kernel.org/all/20230404203449.1627033-1-pctammela@mojatatu.com/

ok