netdev - [PATCH netnext] net: tc: improve qdisc error messages

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Message-ID: <20250116195642.2794-1-ouster@cs.stanford.edu>
Date: Thu, 16 Jan 2025 11:56:41 -0800
From: John Ousterhout <ouster@...stanford.edu>
To: netdev@...r.kernel.org
Cc: jhs@...atatu.com,
	xiyou.wangcong@...il.com,
	jiri@...nulli.us,
	John Ousterhout <ouster@...stanford.edu>
Subject: [PATCH netnext] net: tc: improve qdisc error messages

The existing error message ("Invalid qdisc name") is confusing
because it suggests that there is no qdisc with the given name. In
fact, the name does refer to a valid qdisc, but it doesn't match
the kind of an existing qdisc being modified or replaced. The
new error message provides more detail to eliminate confusion.

Signed-off-by: John Ousterhout <ouster@...stanford.edu>
---
 net/sched/sch_api.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 300430b8c4d2..5d017c06a96f 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1560,7 +1560,7 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 	}

 	if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], q->ops->id)) {
-		NL_SET_ERR_MSG(extack, "Invalid qdisc name");
+		NL_SET_ERR_MSG(extack, "Invalid qdisc name: must match existing qdisc");
 		return -EINVAL;
 	}

@@ -1670,7 +1670,7 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 				}
 				if (tca[TCA_KIND] &&
 				    nla_strcmp(tca[TCA_KIND], q->ops->id)) {
-					NL_SET_ERR_MSG(extack, "Invalid qdisc name");
+					NL_SET_ERR_MSG(extack, "Invalid qdisc name: must match existing qdisc");
 					return -EINVAL;
 				}
 				if (q->flags & TCQ_F_INGRESS) {
@@ -1746,7 +1746,7 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 		return -EEXIST;
 	}
 	if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], q->ops->id)) {
-		NL_SET_ERR_MSG(extack, "Invalid qdisc name");
+		NL_SET_ERR_MSG(extack, "Invalid qdisc name: must match existing qdisc");
 		return -EINVAL;
 	}
 	err = qdisc_change(q, tca, extack);
--
2.34.1