Re: [Exim] IPv6 ?

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Wed, 19 Feb 2003 16:03:45 +0100, Lionel Elie Mamane <lionel@???> ×ÙÛÅÕÐÏÍÑÎÕÔÙÊ:

> No, this doesn't work portably. Binding to :: on a BSD machine does
> NOT listen for IPv4 connects! It does on Linux, but one should not
> rely on it.

True, however, IP methods typically do differ operating system to operating system. Fact is, that's how Linux has been since 2.2/3, and it still is in 2.5, and likely will be in 2.6.

Making Exim not bind to IPv4 by default when binding to IPv6 on Linux systems would be a misimplementation, and thus a bug. As it stands, it's really up to the operator to understand her/his operating system and how it handles binding on the 2 stacks, as low level as it is. This is all documented quite well somewhere in the bowels of the Linux+IPv6 Howto, not that I would expect anybody to get that far.

In either case, I think it's nothing more than a footnote, as far as it goes being a bug. It's hardly inconveniencing, and doesn't impede on the general operation of Exim, assuming it's handled correctly.

If for instance, you were to patch Exim to bind to v4, then go back and attempt to bind to v6, it will /work/, but it's also a misimplementation. Fact is Exim asks Linux to bind to ALL addresses on IPv6. IPv6 includes IPv4 mapped IPv4s, and should, because at that point they /are/ IPv6. Thus, it binds them as well. I wouldn't even call it a Linux bug; it does exactly what I would expect. Albeit, possibly confusing to somebody new to IPv6, or even somebody unfamiliar with IP in general.

--Dan
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