[IPv6]Re: How are AdvReachableTime and AdvCurHopLimit in RFC4861 used?

[Timothy Winters <[e-mail]>]

Hi Ted,

7.3.2 <https://datatracker.ietf.org/doc/html/rfc4861#section-7.3.2> defines
the state machines that use ReachTime.

~Tim

On Sat, May 25, 2024 at 1:50 PM Ole Trøan <otroan=
[e-mail]> wrote:

> 20 uses of ReachableTime. 8 uses of “Reachable Time”.
> Read those sections. But it might be hard to understand ND completely
> unless you read it all.
> It’s a long document and the most complicated core IPv6 protocol
> specification.
>
> O.
>
> On 25 May 2024, at 16:38, Ted Lemon <[e-mail]> wrote:
>
> 
> Right. My question is, where is the rfc that describes what these
> variables do? Hop
> Limit is somewhat straightforward, I guess, but where is the rfc that
> explains what to do with the reachable time? I’m not saying these things
> don’t exist, but there is no reference to them in this RFC.
>
> Op za 25 mei 2024 om 09:58 schreef Mark Smith <[e-mail]>
>
>> On Sat, 25 May 2024 at 21:22, Ted Lemon <[e-mail]> wrote:
>> >
>> > Maybe we should write this down somewhere…
>> >
>>
>> Pretty sure it is in RFC 4861:
>>
>> 6.3.4.  Processing Received Router Advertisements
>> ...
>>    If the received Cur Hop Limit value is non-zero, the host SHOULD set
>>    its CurHopLimit variable to the received value.
>>
>> ...
>> If the received Reachable Time value is non-zero, the host SHOULD set
>>    its BaseReachableTime variable to the received value.  If the new
>>    value differs from the previous value,...
>>
>> > Op za 25 mei 2024 om 02:05 schreef Erik Kline <[e-mail]>
>> >>
>> >> I think they update the per-interface ND state defaults, vis.:
>> >>
>> >>
>> https://elixir.bootlin.com/linux/v6.9.1/source/net/ipv6/ndisc.c#L1457
>> >>
>> >> and
>> >>
>> >>
>> https://elixir.bootlin.com/linux/v6.9.1/source/net/ipv6/ndisc.c#L1426
>> >>
>> >> On Fri, May 24, 2024 at 1:58 PM Ted Lemon <[e-mail]> wrote:
>> >>>
>> >>> We've spent the past half hour in the SNAC interim trying to
>> understand what these do, and we've come up empty. Are they in fact used?
>> What do they do? We don't know what values to specify for them in SNAC
>> router RAs.
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