netdev - Re: [PATCH iproute2] fq: don't allow set options to zero

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Date:	Mon, 12 May 2014 08:23:45 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Yang Yingliang <yangyingliang@...wei.com>
Cc:	stephen@...workplumber.org, netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] fq: don't allow set options to zero

On Mon, 2014-05-12 at 14:59 +0800, Yang Yingliang wrote:
> On 2014/5/12 13:58, Eric Dumazet wrote:
> > On Mon, 2014-05-12 at 12:18 +0800, Yang Yingliang wrote:
> >> Now options of fair queue can be zero but cannot be (~0U).
> >> Zero is useless, so don't allow set the options to zero.
> >> Also, maxrate cannot be reset to unlimited because it
> >> cannot be (~0U).
> >>
> >> Cc: Eric Dumazet <edumazet@...gle.com>
> >> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> >> ---
> >>  tc/q_fq.c | 24 ++++++++++++------------
> >>  1 file changed, 12 insertions(+), 12 deletions(-)
> > 
> > No, you are changing behavior for existing scripts.
> > 
> > If you really want to fix these cases, you need to do it properly.
> > 
> Do you mean options cannot be zero changing the behavior ?

I mean that you need to do something like the following.

diff --git a/tc/q_fq.c b/tc/q_fq.c
index c1f658e..26ecac3 100644
--- a/tc/q_fq.c
+++ b/tc/q_fq.c
@@ -76,7 +76,8 @@ static int fq_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 	unsigned int quantum = ~0U;
 	unsigned int initial_quantum = ~0U;
 	unsigned int buckets = 0;
-	unsigned int maxrate = ~0U;
+	unsigned int maxrate;
+	int set_maxrate = 0;
 	unsigned int defrate = ~0U;
 	int pacing = -1;
 	struct rtattr *tail;
@@ -106,6 +107,7 @@ static int fq_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 				fprintf(stderr, "Illegal \"maxrate\"\n");
 				return -1;
 			}
+			set_maxrate = 1;
 		} else if (strcmp(*argv, "defrate") == 0) {
 			NEXT_ARG();
 			if (get_rate(&defrate, *argv)) {
@@ -161,7 +163,7 @@ static int fq_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 	if (pacing != -1)
 		addattr_l(n, 1024, TCA_FQ_RATE_ENABLE,
 			  &pacing, sizeof(pacing));
-	if (maxrate != ~0U)
+	if (set_maxrate)
 		addattr_l(n, 1024, TCA_FQ_FLOW_MAX_RATE,
 			  &maxrate, sizeof(maxrate));
 	if (defrate != ~0U)


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