IPv6 in jails

[Arthur Chance]

On 19/03/2020 14:01, Victor Sudakov wrote:
> Bjoern A. Zeeb wrote:
>>
>>>> If it does, can you add a
>>>>
>>>> 	exec.start += "sleep  2 ";
>>>>
>>>> to your config
>>>
>>> OK, I've added it to the configs of 3 experimental jails.
>>>
>>>> and see if your problem goes away?
>>>
>>> It goes away partially (only for sshd in 2 of the 3 available jails),
>>> and
>>> not for syslogd in any of the 3 available jails. Restarting the daemons
>>> from within the jail fixes the problem. An example from a problem jail:
>>>
>> ..
>>>
>>>> If it does, the reason is
>>>> that you configure an IPv6 address to an interface and DUD has not
>>>> yet
>>>> completed by the time sshd or other daemons start.  Giving it the 2
> 
> What is "DUD" BTW?
> 

I suspect it's a typo for DAD - duplicate address detection which is
part of IPv6.

>>>> seconds
>>>> avoids this problem and the address is usable at that time.
>>>
>>> There is obviously a race somewhere, but the 2 second sleep does not
>>> eliminate it entirely.
>>
>> Well not so much of a race but than a “gap”.
>>
>> The point is you are configuring an address on the base system and the jail
>> knows nothing about it so it’ll simply start the daemons.  Normally the
>> startup scripts would do the right thing.
>>
>> I don’t think “polluting” jail(8) with logic to check that the addresses
>> become available or not is a good idea.  However I agree that it should
>> automatically do the right thing somehow ..
>>
>>
>>
>>> Thank you for the hint in the right direction, what would you suggest
>>> further?
>>
>> If you make it 3 seconds, does it deterministically work then?
> 
> Not quite: https://termbin.com/arvb
> syslogd sometimes remains deprived of the IPv6 address.
> 


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