Re: Replace time_second with time_uptime in some places

[Ryota Ozaki <ozaki-r%netbsd.org@localhost>]

On Thu, Aug 6, 2015 at 1:27 AM, Greg Troxel <gdt%ir.bbn.com@localhost> wrote:
>
> Ryota Ozaki <ozaki-r%netbsd.org@localhost> writes:
>
>> Some codes in sys/net* use time_second to
>> manage time periods such as cache expirations.
>> However, time_second doesn't increase monotonically
>> and can leap by say settimeofday(2) according to
>> time_second(9). We should use time_uptime
>> instead of it to avoid such time leaps.
>>
>> http://www.netbsd.org/~ozaki-r/use-time_uptime.diff
>
> Generally this sounds sensible.  One thing to consider is whether this
> change results in leaking uptime to hosts over the network.  (That could
> be used to help identify roving hosts.)

Right. A possible leakage is ia6t_expire, but a TTL is
calculated by ia6t_expire - time_uptime so time_uptime
itself isn't leaked.

Here is a list of variables to which time_uptime can
be assigned and how they are used:

- rmx_expire      : exchanged with userland
- ia6t_expire     : used to calculate TTL and
                    passed from userland
                    (but not used for now)
- ia6t_preferred  : passed from userland
                    (but not used for now)
- ia6_updatetime  : passed to userland
                    (via ia6t_expire and ia6t_preferred)
- ia6_createtime  : internal use only
- ip6_log_time    : internal use only
- ru_reseed       : internal use only
- ln_expire       : passed to userland
                    (should be passed from userland too
                     but not used for now. See PR/50127)
- ndpr_lastupdate : passed to userland
                    (via in6_prefix#expire)
- ndpr_preferred  : internal use only
- ndpr_expire     : internal use only

...so I found I forgot some conversions on passing/getting
values to/from userland. Fixed them.

http://www.netbsd.org/~ozaki-r/use-time_uptime.diff

Anyway we would need to add some tests for the IPv6
lifetime management.

Thanks,
  ozaki-r