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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.
> [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.
N.B: I think that all of the proposals would fwmark services without
any extra magic.
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