Add ipv6 support (DO NOT MERGE YET)

[nojb]

See mirage/mirage-tcpip#70 and mirage/mirage#319. I did just enough to be able to run the cohttp examples over ipv6.

Right now you are forced to listen for connections over both IPv4 and IPv6 together (see function serve). We can fix this by making the type of mode have variants TCPv4 of int and TCPv6 of int.

[avsm]

Would you have a rebased version of this for the latest tree?

[nojb]

I can rebase but this would require to have STACKV6 in mirage-tcpip (and a corresponding signature in mirage-types), which used to exist but not anymore. If you want to, I can revive STACKV6 and then rebase this to get it back into working shape.

[samoht]

This PR would be better solved if we manage to get a V1_LWT.STACK module in mirage-types. cc/ @nojb do you still have patches laying around for that?

[nojb]

Do you mean V1_LWT.STACK to be a common signature for a stack that handles either V4 or V6 ? or a stack that handles both V4 and V6 ? I think both would be easy to do. The reason I didn't move forward with this patch is that the current STACKV4 seems to be very much in need of a redesign, and duplicating its functionality for the V6 version (under either of the above escenarios) didn't seem a very good idea.

Having said that, I have the code somewhere because I needed it in order to get mirage-www working over IPv6, so I could revive it if you want ...

[samoht]

Do you mean V1_LWT.STACK to be a common signature for a stack that handles either V4 or V6

yea. I agree that the STACKV4 needs a complete redesign, I think all options (either, both or redesign) are ok and are better than merging this pull request (as it adds again one new argument to the functor).

[ansiwen]

What's the status of this? It never got merged or closed.
And what is the status of IPv6 in general? Is there a conduit that supports IPv6? From reading all the conversations of different pull requests regarding IPv6 I'm a bit lost. :-)

[nojb]

This was written as a quick hack to test the IPv6 implementation in mirage-tcpip some time ago, it is most surely in need of updating, maybe of a complete rewrite.

As for the status of IPv6, there is an implementation of it in mirage-tcpip (probably needing more testing) but AFAIK it is not integrated into the rest of the Mirage infrastructure (the STACK implementation, conduit, etc.)

[nojb]

Not relevant anymore.

[dinosaure]

Yes, due to the ability to define by yourself the type 'edn, it's possible to return an IPv6. Then, a protocol which handles IPv6 must exists (such the tcp/ip UNIX stack).