netdev - Re: [PATCH v3 net-next 2/3] netem: add uapi to express delay and jitter in nanoseconds

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Date:   Thu, 9 Nov 2017 08:24:11 +0900
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Dave Taht <dave.taht@...il.com>
Cc:     netdev@...r.kernel.org, edumazet@...gle.com
Subject: Re: [PATCH v3 net-next 2/3] netem: add uapi to express delay and
 jitter in nanoseconds

On Wed,  8 Nov 2017 15:12:27 -0800
Dave Taht <dave.taht@...il.com> wrote:

> --- a/net/sched/sch_netem.c
> +++ b/net/sched/sch_netem.c
> @@ -819,6 +819,8 @@ static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
>  	[TCA_NETEM_LOSS]	= { .type = NLA_NESTED },
>  	[TCA_NETEM_ECN]		= { .type = NLA_U32 },
>  	[TCA_NETEM_RATE64]	= { .type = NLA_U64 },
> +	[TCA_NETEM_LATENCY64]	= { .type = NLA_S64 },
> +	[TCA_NETEM_JITTER64]	= { .type = NLA_S64 },
>  };
>  
>  static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
> @@ -916,6 +918,12 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt)
>  		q->rate = max_t(u64, q->rate,
>  				nla_get_u64(tb[TCA_NETEM_RATE64]));
>  
> +	if (tb[TCA_NETEM_LATENCY64])
> +		q->latency = nla_get_s64(tb[TCA_NETEM_LATENCY64]);
> +
> +	if (tb[TCA_NETEM_JITTER64])
> +		q->jitter = nla_get_s64(tb[TCA_NETEM_JITTER64]);
> +
>  	if (tb[TCA_NETEM_ECN])
>  		q->ecn = nla_get_u32(tb[TCA_NETEM_ECN]);
>  

Although some of the maths use signed 64 bit.
I think the API should be unsigned 64 bit.  Or do you want to allow
negative latency?