On Wed, Nov 8, 2017 at 3:36 PM, Dave Taht <dave.t...@gmail.com> wrote:
> On Wed, Nov 8, 2017 at 3:24 PM, Stephen Hemminger
> <step...@networkplumber.org> wrote:
>> On Wed, 8 Nov 2017 15:12:27 -0800
>> Dave Taht <dave.t...@gmail.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?
>
> Personally I find things simpler to reason about when signed, and the
> userspace side of the code (currently) offers the ability to generically
> have signed time values for "other stuff".
>
> The constrained range of 63 vs 64 bits we can debate in 272 years or so.
ktime_get_ns() returns number of nanosec in u64, since machine _boot_
So we wont have overflows, unless a linux host can stay up for more
than 500 years.
This seems unlikely.
