Re: draft-cmetz-v6ops-v4mapped-api-harmful-00.txt and draft-itojun-v6ops-v4mapped-harmful-01.txt

[Mauro Tortonesi <mtortonesi@ing.unife.it>]

On Fri, 12 Sep 2003, Iljitsch van Beijnum wrote:

> On vrijdag, sep 12, 2003, at 11:33 Europe/Amsterdam, Mauro Tortonesi
> wrote:
>
> > then my credo as a developer is "ipv6 is a brand new protocol", because
> > AF_INET6 sockets have many options that are not applicable to ipv4
> > connections, and writing applications that make use of the ipv4-mapped
> > catch-all approach will be a great problem for developers (that will
> > find
> > themselves writing __a lot__ of checks/workarounds for special cases
> > and
> > will become crazy during the testing/debugging process).
>
> So what's the alternative? Ripping mapped addresses out of current
> implementations doesn't make sense for many reasons.

sure, but we could deprecate usage of ipv4-mapped addresses.


> The only question is whether you should/want to use them. If you want
> to do stuff with IPv6 that you can't do with IPv4, you'll have to do a
> lot of checking regardless of how you do it.

yes, but they're always less than the checks you would do if you were
also supporting ipv4-mapped addresses.


> If you feel using the IPv6 socket API for IPv6 and the IPv4 socket API
> for IPv4 makes more sense, then by all means, do it that way. But for
> simple applications I think it's a huge plus to be able to talk to the
> network in a unified way without having to spend time and effort on
> making the IPv4/IPv6 distinction. Obviously this means you can't do any
> IPv6-specific stuff.

this could be a plus only for for very simple apps where the developers
don't care for portability or robustness.


> > moreover, i think that the ipv4-mapped catch-all approach in the
> > development of ipv6-enabled apps may eventually become an obstacle for
> > widespread adoption of production quality ipv6-enabled software (since
> > it
> > makes more difficult the use of the advanced ipv6 capabilities)
>
> I don't agree. Just tell the stack you don't want to talk IPv4.

not all the stacks support IPv6_V6ONLY, yet.


> Also, in the document I read it seems half or more of the trouble comes
> from mixing IPv4 and IPv6 calls. So don't do that.

actually, this is not true. in fact, half or more of the trouble comes
from the fact that nearly every stack has a different bind(2) behaviour.


-- 
Aequam memento rebus in arduis servare mentem...

Mauro Tortonesi                 mtortonesi@ing.unife.it
                                mauro@deepspace6.net
                                mauro@ferrara.linux.it
Deep Space 6 - IPv6 with Linux  http://www.deepspace6.net
Ferrara Linux User Group        http://www.ferrara.linux.it