code review 75180043: net: improve behavior of native Go DNS queries

net: improve behavior of native Go DNS queries

See https://groups.google.com/forum/#!topic/golang-dev/lV-0aHqxVeo

Fixes issue 6579.

Benchmark results on linux/amd64:

benchmark                                  old ns/op    new ns/op    delta
BenchmarkGoLookupIP                         59284398     35349632  -40.37%
BenchmarkGoLookupIPNoSuchHost              131102584     34241062  -73.88%
BenchmarkGoLookupIPWithBrokenNameServer  20048604097   5024381059  -74.94%

benchmark                                 old allocs   new allocs    delta
BenchmarkGoLookupIP                              107          112    4.67%
BenchmarkGoLookupIPNoSuchHost                    212          110  -48.11%
BenchmarkGoLookupIPWithBrokenNameServer          165          161   -2.42%

benchmark                                  old bytes    new bytes    delta
BenchmarkGoLookupIP                            11416        11863    3.92%
BenchmarkGoLookupIPNoSuchHost                  23331        12053  -48.34%
BenchmarkGoLookupIPWithBrokenNameServer        25696        21728  -15.44%

[axaxs, 2014-03-15 02:25:04]

Hello golang-codereviews@googlegroups.com,

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

[gobot, 2014-03-15 14:40:37]

R=mikioh.mikioh@gmail.com (assigned by josharian@gmail.com)

[rsc, 2014-04-17 02:57:32]

R=close

Thanks for working on this. I'm sorry, but the release freeze was March 1.
Please run 'hg mail' once Go 1.3 is out and we can pick this up for 1.4. The
improvements do look impressive.