code review 4557058: net: name-based destination address selection

net: name-based destination address selection

getaddrinfo() orders the addresses according to RFC 3484.

This means when IPv6 is working on a host we get results like:
    []string = {"2001:4810::110", "66.117.47.214"}

and when it's not working we get:
    []string = {"66.117.47.214", "2001:4810::110"}

thus can drop firstFavoriteAddr.

This also means /etc/gai.conf works on relevant systems.

[cw, 2011-05-28 07:43:58]

Hello rsc@golang.org, mikioh.mikioh@gmail.com (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[mikio, 2011-05-28 14:29:44]

On Sat, May 28, 2011 at 4:43 PM,  <cw@f00f.org> wrote:

> Description:
> net: Do not prefer IPv4 over IPv6, use the order from getaddrinfo()

"net: nicer name-based destination address selection" rather
than "do not prefer IPv4 over IPv6"?

> getaddrinfo() orders the addresses according to RFC 3484.

a) If I have no IPv6 connectivity and www.google.com has both A
and quad-A records, I have to wait more seconds for google page
loading because RFC 3484 and draft-ietf-6man-rfc3484-revise's
default policy table still recommend to prefer IPv6 than IPv4.

b) Even if I have an IPv6 connectivity but it's slower than IPv4,
my google experience will be same as (a).

c) To avoid (a) and (b), I have to run some commands; for Linux
configure gai.conf, for FreeBSD run ip6addrctl, for Windows run netsh.
But for MacOS X, there's no control command.

Probably it might be better another solution instead of dropping current
*anti RFC 3484 but practical* destination address selection stuff, but
not sure indeed.

So I say LGTM so far.

-- Mikio

[cw, 2011-05-28 15:21:10]

On Sat, May 28, 2011 at 11:29:44PM +0900, Mikio Hara wrote:

> "net: nicer name-based destination address selection" rather
> than "do not prefer IPv4 over IPv6"?

done, i'm not sure i like it anymore though

> Probably it might be better another solution instead of dropping current
> *anti RFC 3484 but practical* destination address selection stuff, but
> not sure indeed.

right now, nothing involving ipv6 is perfect, i'm just trying to mkae
behavior and expectations the same as those for typical other
applications like curl, ssh & telnet right now (i tested the behavoir
against such things with and without ipv6)

[cw, 2011-05-28 15:21:10]

Hello rsc@golang.org, mikioh.mikioh@gmail.com (cc: golang-dev@googlegroups.com),

Please take another look.

[rsc, 2011-05-31 15:40:04]

LGTM

[rsc, 2011-05-31 15:40:15]

*** Submitted as http://code.google.com/p/go/source/detail?r=b4c2ffae7034 ***

net: name-based destination address selection

getaddrinfo() orders the addresses according to RFC 3484.

This means when IPv6 is working on a host we get results like:
    []string = {"2001:4810::110", "66.117.47.214"}

and when it's not working we get:
    []string = {"66.117.47.214", "2001:4810::110"}

thus can drop firstFavoriteAddr.

This also means /etc/gai.conf works on relevant systems.

R=rsc, mikioh.mikioh
CC=golang-dev
http://codereview.appspot.com/4557058

Committer: Russ Cox <rsc@golang.org>