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Hi simon,
From: Simon Horman <horms@xxxxxxxxxxxx>
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> On Mon, Aug 02, 2010 at 06:35:49PM +0900, Sohgo Takeuchi wrote:
>>
>> Hi,
>>
>> I have been working on improving IPv6 support of ldirectord
>> for a few weeks. I would like to hear your opinion or ideas
>> about how to write ldirectord.conf.
>
> A tricky topic, thanks for thinking it through.
>
>> Q1. Should ldirectord support an IPv6 hostname in ldirectord.conf?
>>
>> A manual of ldirectord says that a hostname can be written
>> in "virtual", "real", "fallback" and so on. Current
>> implementation of ldirectord handles the hostname as only
>> IPv4. It partially supports IPv6, and can write only IPv6
>> addresses. But it does not have a way to write a hostname as
>> IPv6. Because there is no way to distinguish between IPv4
>> and IPv6. Should ldirectord support an IPv6 hostname in
>> ldirectord.conf?
>>
>> Q2. If the answer of Q1 is yes, how do you want to write?
>>
>> [Candidate 1] Adding a new keyword like a "ipversion".
>> A default value of "ipversion" is 4 (IPv4).
>>
>> fallback=fallback.example.com
>> fallback6=fallback.example.com
>> virtual=virtual.example.com:daytime
>> real=real1.example.com:daytime gate
>> real=10.10.10.10:daytime gate
>>
>> virtual=virtual.example.com:daytime
>> ipversion=6
>> real=real1.example.com:daytime gate
>> real=[2001:db8::10]:daytime gate
>>
>> This way cannot handle a global "fallback" variable. We must
>> have a way to distinguish between IPv4 and IPv6 when a
>> hostname is specified in the global "fallback" variable. To
>> achieve this, there is a way to add a new variable of
>> "fallback6". Any other good ideas?
>
> This "fallback" problem seems to be the most difficult issue.
>
>> [Candidate 2] Adding new keywords of "virtual6" and
>> "fallback6".
>>
>> "virtual6" is an IPv6 version of "virtual". If a hostname
>> and an IP address are specified in the "virtual6" line and
>> in its section, they are treated as an IPv6 address and the
>> hostname will be resolved into an IPv6 address.
>>
>> "fallback6" is just a global variable. It cannot be
>> specified in a virtual section. If no "fallback" in a
>> "virtual6" section is defined, the variable of "fallback6"
>> will be used. If "fallback" in the "virtual6" section is
>> defined, it is treated as an IPv6 address.
>>
>>
>> fallback=fallback.example.com
>> fallback6=fallback.example.com
>> virtual=virtual.example.com:daytime
>> real=real1.example.com:daytime gate
>> real=10.10.10.10:daytime gate
>>
>> virtual6=virtual.example.com:daytime
>> real=real1.example.com:daytime gate
>> real=[2001:db8::10]:daytime gate
>>
>> This way breaks a backward compatibility. Current ldirectord
>> can write an IPv6 address in a "virtual" line. But this way
>> cannot.
>
> I'm not particularly concerned about backwards compatibility here,
> IPv6 for ldirectord is pretty green.
That's good.
>> [Candidate 3] Completely separate IPv4 and IPv6 using
>> "hoge6" keywords.
>>
>> Adding new keywords which denote IPv6. These keywords can
>> handle IPv6 only and have a name "hoge6".
>>
>> fallback=fallback.example.com
>> fallback6=fallback.example.com
>> virtual=virtual.example.com:daytime
>> real=real1.example.com:daytime gate
>> real=10.10.10.10:daytime gate
>>
>> virtual6=virtual.example.com:daytime
>> real6=real1.example.com:daytime gate
>> real6=[2001:db8::10]:daytime gate
>> fallback6=localhost:daytime
>>
>> This way is very similar to [Candidate 2]. But it is
>> consistent and easy to read. A demerit is a bit redundant?
>
> I like candidate 3. Yes, it is redundant, but it is also very clear
> and consistent.
Yes.
I have implemented [candidate 3]. Now it works good.
> N.B: I think that all of the proposals would fwmark services without
> any extra magic.
Oh, thank you. I have not considered fwmark. I think so too as
you say.
--
Sohgo Takeuchi
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