code review 58120045: net: only return unique hosts during hostname lookup on...

net: only return unique hosts during hostname lookup on plan 9

TestLookupHost expects that no duplicate addresses are returned. when cs is consulted for a name, e.g net!localhost!1, it will possibly return multiple available paths, e.g. via il and tcp. this confuses the tests.

[mischief, 2014-01-30 07:19:19]

Hello jas@corpus-callosum.com, 0intro@gmail.com (cc:
golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go/

[jas, 2014-01-30 07:28:37]

Per dns, a lookup can return more than one address and should't be filtered
here.

The case for localhost is special, if you are getting multiple entries, you'd
probably want to look at /lib/ndb to see why.

[mischief, 2014-01-30 07:33:24]

On 2014/01/30 07:28:37, jas wrote:
> Per dns, a lookup can return more than one address and should't be filtered
> here.

it's only removing duplicates. it should not prevent multiple different
addresses being returned.

> 
> The case for localhost is special, if you are getting multiple entries, you'd
> probably want to look at /lib/ndb to see why.

; ndb/csquery
> net!localhost!1
/net/il/clone 127.0.0.1!1!fasttimeout
/net/tcp/clone 127.0.0.1!1
/net/il/clone 127.0.0.1!1
> 

and in my /lib/ndb/common:

ip=127.0.0.1 sys=localhost dom=localhost

[jas, 2014-01-30 08:07:11]

Have you tried with:
proto=tcp

[jas, 2014-01-30 08:08:41]

Have you tried with:

ip=127.0.0.1 sys=localhost dom=localhost
    proto=tcp

[mischief, 2014-01-30 08:40:17]

On 2014/01/30 08:08:41, jas wrote:
> Have you tried with:
> 
> ip=127.0.0.1 sys=localhost dom=localhost
>     proto=tcp

adding proto=tcp does not seem to change the situation.

perhaps you can test this more accurately if you compile il into your kernel. i
just noticed it has been removed from the pcf kernel configuration file on
sources, but it remains in 9front.

[aram, 2014-01-30 10:42:48]

LGTM

First I was uncertain this is the correct fix, but after some more thinking I
believe it is the correct fix.

[aram, 2014-01-30 10:45:43]

On 2014/01/30 08:07:11, jas wrote:
> Have you tried with:
> proto=tcp

I thought of this as well, but this doesn't seem like a good idea. There's no
reason for name lookup to be restrictive like this. We should get all the names.
Unfortunately, the names we get are "richer" that what Go understands or cares
about, so if after filtering we get duplicates, it's Go's job to remove them.

[jas, 2014-01-30 15:52:20]

Richer may be an over generous use of the term.  Considering ndb doesn't support
all the protocols or lookups you get with a modern day bind, we will get a few
exceptions, e.g., RFC 2782.

[aram, 2014-01-30 16:00:53]

On Thu, Jan 30, 2014 at 4:52 PM, <jas@corpus-callosum.com> wrote:
>
> Richer may be an over generous use of the term.  Considering ndb doesn't
> support all the protocols or lookups you get with a modern day bind, we
> will get a few exceptions, e.g., RFC 2782.

The interface is richer in the sense that the format of the data is richer,
although the data might be lacking.

    /net/il/clone 199.102.76.134!1!fasttimeout
    /net/il/clone 199.102.76.134!1

In Plan 9, the distinction between these two is useful.
For Go's Lookup function they should be the same thing.

-- 
Aram Hăvărneanu

[mischief, 2014-02-06 21:13:10]

ping.

[rsc, 2014-02-13 15:26:23]

*** Submitted as https://code.google.com/p/go/source/detail?r=19f24bb3c8f8 ***

net: only return unique hosts during hostname lookup on plan 9

TestLookupHost expects that no duplicate addresses are returned. when cs is
consulted for a name, e.g net!localhost!1, it will possibly return multiple
available paths, e.g. via il and tcp. this confuses the tests.

LGTM=aram
R=jas, 0intro, aram
CC=golang-codereviews
https://codereview.appspot.com/58120045

Committer: Russ Cox <rsc@golang.org>

[gobot, 2014-02-13 15:38:57]

This CL appears to have broken the darwin-amd64 builder.