code review 2420041: SRV support and RFC compliance

SRV support and RFC compliance

LookupSRV() always fails because isDomainName() returns false for any
valid SRV query. Specifically, it rejects the leading _ character on
the first two domain name parts. This patch changes the behavior of
isDomainName() to be in keeping with RFC 2181, which allows SRV
queries to work. However, that RFC appears to contradict the other
cited RFCs. It's likely that a correct reading requires a delicate
interpretation of "DNS record" vs. "DNS name" or something similar.

This change also adds LookupSRVByNet(), which uses the three
parameters listed in RFC 2782: service, proto, and name. This
function could use a better name; I'm guessing we can't replace the
old LookupSRV() with it, because it would be an incompatible API
change.

[cjyar, 2010-10-10 06:41:10]

Hello golang-dev@googlegroups.com (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[rsc, 2010-10-11 15:31:38]

Please sync with the latest tip.  I believe half of this CL is covered by

changeset:   6473:9b27e48edf12
user:        Russ Cox <rsc@golang.org>
date:        Thu Oct 07 06:45:50 2010 -0400
summary:     net: allow _ in names

I'd be happy to replace LookupSRV instead of adding a new function.

Thanks.
Russ

[cjyar, 2010-10-15 04:43:59]

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

Please take another look.

[cjyar, 2010-10-15 04:44:24]

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

Please take another look.

[cjyar, 2010-10-15 04:46:50]

On 2010/10/15 04:44:24, cjyar wrote:
> Hello mailto:golang-dev@googlegroups.com, rsc (cc:
mailto:golang-dev@googlegroups.com),
> 
> Please take another look.

Replaced the old LookupSRV() with the new 3-argument syntax. I think this is
more in keeping with the relevant RFC.

I also changed dnsname_test.go a bit. There are some names that I really don't
know if we should accept or not, so I removed them as test cases. :)

I added a bit of logic to isDomainName() to check the overall length of the name
and the lengths of its parts.

[chris_cjones.org, 2010-10-30 02:33:05]

It's been a couple of weeks. Could somebody take a look at this?

Chris

On 10/14/2010 10:46 PM, chris.jones.yar@gmail.com wrote:
> On 2010/10/15 04:44:24, cjyar wrote:
>> Hello mailto:golang-dev@googlegroups.com, rsc (cc:
> mailto:golang-dev@googlegroups.com),
>
>> Please take another look.
>
> Replaced the old LookupSRV() with the new 3-argument syntax. I think
> this is more in keeping with the relevant RFC.
>
> I also changed dnsname_test.go a bit. There are some names that I really
> don't know if we should accept or not, so I removed them as test cases.
> :)
>
> I added a bit of logic to isDomainName() to check the overall length of
> the name and the lengths of its parts.
>
> http://codereview.appspot.com/2420041/

[rsc1, 2010-11-01 18:54:05]

LGTM

[rsc1, 2010-11-01 20:21:01]

Could you please complete a CLA as described at
http://golang.org/doc/contribute.html#copyright ?

Thanks.
Russ

[chris_cjones.org, 2010-11-01 20:40:25]

Done.

On 11/1/2010 2:21 PM, rsc@google.com wrote:
> Could you please complete a CLA as described at
> http://golang.org/doc/contribute.html#copyright ?
>
> Thanks.
> Russ
>
>
> http://codereview.appspot.com/2420041/

[rsc, 2010-11-04 14:30:42]

*** Submitted as e4191df7dd41 ***

net: fix LookupSRV

R=rsc, chris
CC=golang-dev
http://codereview.appspot.com/2420041

Committer: Russ Cox <rsc@golang.org>