[PATCH net-next 1/6] net/sched: netem: replace pr_info with netlink extack error messages

[Stephen Hemminger <stephen@networkplumber.org>]

netem predates the netlink extended ack mechanism and uses pr_info()
to report configuration errors. These messages go to the kernel log
where the user running tc may never see them, and in unprivileged
user namespace contexts they can be used for log spam.

Replace pr_info() with NL_SET_ERR_MSG() and NL_SET_ERR_MSG_FMT()
which return error details to the caller via netlink.
Remove the uninformative "netem: change failed" message from netem_init()
since the error is already propagated.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 net/sched/sch_netem.c | 42 ++++++++++++++++++++++++------------------
 1 file changed, 24 insertions(+), 18 deletions(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 5de1c932944a..73d0e85eeadc 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -804,19 +804,24 @@ static void dist_free(struct disttable *d)
  * signed 16 bit values.
  */
 
-static int get_dist_table(struct disttable **tbl, const struct nlattr *attr)
+static int get_dist_table(struct disttable **tbl, const struct nlattr *attr,
+			  struct netlink_ext_ack *extack)
 {
 	size_t n = nla_len(attr)/sizeof(__s16);
 	const __s16 *data = nla_data(attr);
 	struct disttable *d;
 	int i;
 
-	if (!n || n > NETEM_DIST_MAX)
+	if (!n || n > NETEM_DIST_MAX) {
+		NL_SET_ERR_MSG(extack, "invalid distribution table length");
 		return -EINVAL;
+	}
 
 	d = kvmalloc_flex(*d, table, n);
-	if (!d)
+	if (!d) {
+		NL_SET_ERR_MSG(extack, "allocation of distribution table failed");
 		return -ENOMEM;
+	}
 
 	d->size = n;
 	for (i = 0; i < n; i++)
@@ -887,7 +892,8 @@ static void get_rate(struct netem_sched_data *q, const struct nlattr *attr)
 		q->cell_size_reciprocal = (struct reciprocal_value) { 0 };
 }
 
-static int get_loss_clg(struct netem_sched_data *q, const struct nlattr *attr)
+static int get_loss_clg(struct netem_sched_data *q, const struct nlattr *attr,
+			struct netlink_ext_ack *extack)
 {
 	const struct nlattr *la;
 	int rem;
@@ -900,7 +906,7 @@ static int get_loss_clg(struct netem_sched_data *q, const struct nlattr *attr)
 			const struct tc_netem_gimodel *gi = nla_data(la);
 
 			if (nla_len(la) < sizeof(struct tc_netem_gimodel)) {
-				pr_info("netem: incorrect gi model size\n");
+				NL_SET_ERR_MSG(extack, "incorrect gi model size");
 				return -EINVAL;
 			}
 
@@ -919,7 +925,7 @@ static int get_loss_clg(struct netem_sched_data *q, const struct nlattr *attr)
 			const struct tc_netem_gemodel *ge = nla_data(la);
 
 			if (nla_len(la) < sizeof(struct tc_netem_gemodel)) {
-				pr_info("netem: incorrect ge model size\n");
+				NL_SET_ERR_MSG(extack, "incorrect ge model size");
 				return -EINVAL;
 			}
 
@@ -933,7 +939,7 @@ static int get_loss_clg(struct netem_sched_data *q, const struct nlattr *attr)
 		}
 
 		default:
-			pr_info("netem: unknown loss type %u\n", type);
+			NL_SET_ERR_MSG_FMT(extack, "unknown loss type %u", type);
 			return -EINVAL;
 		}
 	}
@@ -956,12 +962,13 @@ static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
 };
 
 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
-		      const struct nla_policy *policy, int len)
+		      const struct nla_policy *policy, size_t len,
+		      struct netlink_ext_ack *extack)
 {
 	int nested_len = nla_len(nla) - NLA_ALIGN(len);
 
 	if (nested_len < 0) {
-		pr_info("netem: invalid attributes len %d\n", nested_len);
+		NL_SET_ERR_MSG(extack, "invalid attribute len");
 		return -EINVAL;
 	}
 
@@ -1010,8 +1017,7 @@ static int check_netem_in_tree(struct Qdisc *sch, bool duplicates,
 }
 
 /* Parse netlink message to set options */
-static int netem_change(struct Qdisc *sch, struct nlattr *opt,
-			struct netlink_ext_ack *extack)
+static int netem_change(struct Qdisc *sch, struct nlattr *opt, struct netlink_ext_ack *extack)
 {
 	struct netem_sched_data *q = qdisc_priv(sch);
 	struct nlattr *tb[TCA_NETEM_MAX + 1];
@@ -1023,18 +1029,18 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt,
 	int ret;
 
 	qopt = nla_data(opt);
-	ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
+	ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt), extack);
 	if (ret < 0)
 		return ret;
 
 	if (tb[TCA_NETEM_DELAY_DIST]) {
-		ret = get_dist_table(&delay_dist, tb[TCA_NETEM_DELAY_DIST]);
+		ret = get_dist_table(&delay_dist, tb[TCA_NETEM_DELAY_DIST], extack);
 		if (ret)
 			goto table_free;
 	}
 
 	if (tb[TCA_NETEM_SLOT_DIST]) {
-		ret = get_dist_table(&slot_dist, tb[TCA_NETEM_SLOT_DIST]);
+		ret = get_dist_table(&slot_dist, tb[TCA_NETEM_SLOT_DIST], extack);
 		if (ret)
 			goto table_free;
 	}
@@ -1045,7 +1051,7 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt,
 	old_loss_model = q->loss_model;
 
 	if (tb[TCA_NETEM_LOSS]) {
-		ret = get_loss_clg(q, tb[TCA_NETEM_LOSS]);
+		ret = get_loss_clg(q, tb[TCA_NETEM_LOSS], extack);
 		if (ret) {
 			q->loss_model = old_loss_model;
 			q->clg = old_clg;
@@ -1134,13 +1140,13 @@ static int netem_init(struct Qdisc *sch, struct nlattr *opt,
 
 	qdisc_watchdog_init(&q->watchdog, sch);
 
-	if (!opt)
+	if (!opt) {
+		NL_SET_ERR_MSG(extack, "missing parameters");
 		return -EINVAL;
+	}
 
 	q->loss_model = CLG_RANDOM;
 	ret = netem_change(sch, opt, extack);
-	if (ret)
-		pr_info("netem: change failed\n");
 	return ret;
 }
 
-- 
2.53.0