netdev - [PATCH iproute2-next] tc: htb: improve burst error messages

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Date:   Thu,  6 May 2021 12:42:06 +0200
From:   Andrea Claudi <aclaudi@...hat.com>
To:     netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, dsahern@...il.com
Subject: [PATCH iproute2-next] tc: htb: improve burst error messages

When a wrong value is provided for "burst" or "cburst" parameters, the
resulting error message is unclear and can be misleading:

$ tc class add dev dummy0 parent 1: classid 1:1 htb rate 100KBps burst errtrigger
Illegal "buffer"

The message claims an illegal "buffer" is provided, but neither the
inline help nor the man page list "buffer" among the htb parameters, and
the only way to know that "burst", "maxburst" and "buffer" are synonyms
is to look into tc/q_htb.c.

This commit tries to improve this simply changing the error string to
the parameter name provided in the user-given command, clearly pointing
out where the wrong value is.

$ tc class add dev dummy0 parent 1: classid 1:1 htb rate 100KBps burst errtrigger
Illegal "burst"

$ tc class add dev dummy0 parent 1: classid 1:1 htb rate 100Kbps maxburst errtrigger
Illegal "maxburst"

Reported-by: Sebastian Mitterle <smitterl@...hat.com>
Signed-off-by: Andrea Claudi <aclaudi@...hat.com>
---
 tc/q_htb.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tc/q_htb.c b/tc/q_htb.c
index 42566355..b5f95f67 100644
--- a/tc/q_htb.c
+++ b/tc/q_htb.c
@@ -125,6 +125,7 @@ static int htb_parse_class_opt(struct qdisc_util *qu, int argc, char **argv, str
 	unsigned int linklayer  = LINKLAYER_ETHERNET; /* Assume ethernet */
 	struct rtattr *tail;
 	__u64 ceil64 = 0, rate64 = 0;
+	char *param;
 
 	while (argc > 0) {
 		if (matches(*argv, "prio") == 0) {
@@ -160,17 +161,19 @@ static int htb_parse_class_opt(struct qdisc_util *qu, int argc, char **argv, str
 		} else if (matches(*argv, "burst") == 0 ||
 			   strcmp(*argv, "buffer") == 0 ||
 			   strcmp(*argv, "maxburst") == 0) {
+			param = *argv;
 			NEXT_ARG();
 			if (get_size_and_cell(&buffer, &cell_log, *argv) < 0) {
-				explain1("buffer");
+				explain1(param);
 				return -1;
 			}
 		} else if (matches(*argv, "cburst") == 0 ||
 			   strcmp(*argv, "cbuffer") == 0 ||
 			   strcmp(*argv, "cmaxburst") == 0) {
+			param = *argv;
 			NEXT_ARG();
 			if (get_size_and_cell(&cbuffer, &ccell_log, *argv) < 0) {
-				explain1("cbuffer");
+				explain1(param);
 				return -1;
 			}
 		} else if (strcmp(*argv, "ceil") == 0) {
-- 
2.30.2