netdev - [PATCH v4 net-next 2/9] net/sched: mqprio: simplify handling of nlattr portion of TCA

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Date:   Mon,  3 Apr 2023 13:34:33 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        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: [PATCH v4 net-next 2/9] net/sched: mqprio: simplify handling of nlattr portion of TCA_OPTIONS

In commit 4e8b86c06269 ("mqprio: Introduce new hardware offload mode and
shaper in mqprio"), the TCA_OPTIONS format of mqprio was extended to
contain a fixed portion (of size NLA_ALIGN(sizeof struct tc_mqprio_qopt))
and a variable portion of other nlattrs (in the TCA_MQPRIO_* type space)
following immediately afterwards.

In commit feb2cf3dcfb9 ("net/sched: mqprio: refactor nlattr parsing to a
separate function"), we've moved the nlattr handling to a smaller
function, but yet, a small parse_attr() still remains, and the larger
mqprio_parse_nlattr() still does not have access to the beginning, and
the length, of the TCA_OPTIONS region containing these other nlattrs.

In a future change, the mqprio qdisc will need to iterate through this
nlattr region to discover other attributes, so eliminate parse_attr()
and add 2 variables in mqprio_parse_nlattr() which hold the beginning
and the length of the nlattr range.

We avoid the need to memset when nlattr_opt_len has insufficient length
by pre-initializing the table "tb".

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
Reviewed-by: Ferenc Fejes <fejes@....elte.hu>
Reviewed-by: Simon Horman <simon.horman@...igine.com>
---
v1->v4: none

 net/sched/sch_mqprio.c | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
index 48ed87b91086..94093971da5e 100644
--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -146,32 +146,26 @@ static const struct nla_policy mqprio_policy[TCA_MQPRIO_MAX + 1] = {
 	[TCA_MQPRIO_MAX_RATE64]	= { .type = NLA_NESTED },
 };
 
-static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
-		      const struct nla_policy *policy, int len)
-{
-	int nested_len = nla_len(nla) - NLA_ALIGN(len);
-
-	if (nested_len >= nla_attr_size(0))
-		return nla_parse_deprecated(tb, maxtype,
-					    nla_data(nla) + NLA_ALIGN(len),
-					    nested_len, policy, NULL);
-
-	memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
-	return 0;
-}
-
+/* Parse the other netlink attributes that represent the payload of
+ * TCA_OPTIONS, which are appended right after struct tc_mqprio_qopt.
+ */
 static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
 			       struct nlattr *opt)
 {
+	struct nlattr *nlattr_opt = nla_data(opt) + NLA_ALIGN(sizeof(*qopt));
+	int nlattr_opt_len = nla_len(opt) - NLA_ALIGN(sizeof(*qopt));
 	struct mqprio_sched *priv = qdisc_priv(sch);
-	struct nlattr *tb[TCA_MQPRIO_MAX + 1];
+	struct nlattr *tb[TCA_MQPRIO_MAX + 1] = {};
 	struct nlattr *attr;
 	int i, rem, err;
 
-	err = parse_attr(tb, TCA_MQPRIO_MAX, opt, mqprio_policy,
-			 sizeof(*qopt));
-	if (err < 0)
-		return err;
+	if (nlattr_opt_len >= nla_attr_size(0)) {
+		err = nla_parse_deprecated(tb, TCA_MQPRIO_MAX, nlattr_opt,
+					   nlattr_opt_len, mqprio_policy,
+					   NULL);
+		if (err < 0)
+			return err;
+	}
 
 	if (!qopt->hw)
 		return -EINVAL;
-- 
2.34.1