* core: allow all CIDR ranges in zone specifications

Allow (e.g.) a v4 reverse on a /17. If a zone is specified in such a
way a FilterFunc is set in the config. This filter is checked against
incoming queries.

For all other queries this adds a 'x != nil' check which will not impact
performace too much. Benchmark function is added as well to check for
this as wel.

Add multiple tests in tests/server_reverse_test.go.

Benchmark shows in the non-reverse case this hardly impact the speed:

~~~
classless:
pkg: github.com/coredns/coredns/core/dnsserver
BenchmarkCoreServeDNS-4   	 1000000	      1431 ns/op	      16 B/op	       1 allocs/op

pkg: github.com/coredns/coredns/core/dnsserver
BenchmarkCoreServeDNS-4   	 1000000	      1429 ns/op	      16 B/op	       1 allocs/op

master:
pkg: github.com/coredns/coredns/core/dnsserver
BenchmarkCoreServeDNS-4   	 1000000	      1412 ns/op	      16 B/op	       1 allocs/op

pkg: github.com/coredns/coredns/core/dnsserver
BenchmarkCoreServeDNS-4   	 1000000	      1429 ns/op	      16 B/op	       1 allocs/op
~~~

* README.md updates

This flakyness is driving me crazy. Add the sleep(3s) back.

* stalebot: use wontfix-stalebot

I've added two new labels: wontfix-stalebot and pinned.

Wontfix-stalebot will be used by stalebot and pinned can be used to keep
issues open.

* later as well

Make the locking slightly smarter in Evict and add benchmark function.

Seems a bit faster (there was some variance while performing these
benchmarks)

Master:
BenchmarkCache-2   	 1000000	      2317 ns/op	       0 B/op	       0 allocs/op
BenchmarkCache-2   	 1000000	      2032 ns/op	       0 B/op	       0 allocs/op

This branch:
BenchmarkCache-2   	 1000000	      1806 ns/op	       0 B/op	       0 allocs/op
BenchmarkCache-2   	 1000000	      1809 ns/op	       0 B/op	       0 allocs/op

These file still had middleware in their name, rename to plugin.

* core: add ServeDNS benchmark

Add benchmark function so we can perf test future additions to the
servers' ServeDNS function.

* naming

* plugin/kubernetes: wait until api is ready

Wait for HasSynced before allowing startup to avoid startup race.

Also do a small refactor in findServices() to pull a check out of the
loop - only needs to be done once.

* sigh

Various other changes.

* plugin/dnssec; insert and sign DS records

Sign a delegation as well and insert DS records.

Fixes #698

* better

We support ENV variables in config files, add an example in the one for
metric, note that `localhost:` is a valid host (in Go), so the
TestReadme will parse this correctly.

Fixes #1150

* indexing

* corrections

* Don't number the plugins

The number is not needed, because the ordering is already specified.
It's also annoying when you move plugins, because you need to renumber
them. Remove this.

'go gen' shows no changes in the generated files, meaning this just
works.

* better naming

* plugin/autopath: Add namespace selector and metrics

Add a namespace, so autopathing only is performed in this namespace.
This will make caching work for the cluster again.

Also export metrics that we've done a successful autopath

* dont shadow

* Fix

* Back the namespacing changes

* healthchecks: check on every 3rd failure

Check on every third failure and some cleanups to make this possible. A
failed healthcheck will never increase Fails, a successfull healthceck
will reset Fails to 0. This is a chance this counter now drops below 0,
making the upstream super? healthy.

This removes the okUntil smartness and condences everything back to 1
metrics: Fails; so it's simpler in that regard.

Timout errors are *not* attributed to the local upstream, and don't get
counted into the Fails anymore. Meaning the 'dig any isc.org' won't kill
your upstream.

Added extra test the see if the Fails counter gets reset after 3 failed
connection.

There is still a disconnect beween HTTP healthceck working the proxy (or
lookup) not being able to connect to the upstream.

* Fix tests

Small optimization.

Flaky test because it used a fix port; just drop it. Might be worthwhile
to return it as a unit tests, but on that level we can't use a coredns
"process" to exercise the reload.

See https://github.com/kubernetes/kubernetes/pull/53604, explicitaly add
test to make sure we do the right thing.

* doc update

Go through all README and fix mistakes, extend example and let more
corefile snippets be test for validity.

* Cant use spefic addr in test

Add Counter metrics and fix duration to use upstream name (and only use
it when we have one).

Fix the documentation to reflect this.

Fixes #1134

* add NSEC-records if entry exists but the requested type is missing

* added test for dnssec fix

Clean out the imports in coredns.go and just leave the server import.

Fixes #1119

Use team@coredns.io for reporting sec. vulnerablities. Currenttly this
has john@coredns.io and miek@coredns.io

Make it work with root zone in the query.

close stale issues and stop the merging of PR with WIP in the name.

Fix file/fuzz.go build and docs in Makefile.fuzz
Each plugin can add a fuzz.go to join the fuzzing craze.
pkg/fuzz/do.go could be made a lot smarter, but is probably good enough
for starters.

$ make -f Makefile.fuzz <plugin>

will build with go-fuzz-build and then execute a go-fuzz run. Each
plugin's fuzz run uses a per-plugin directory to store the fuzz data.

We can still be on the receiving end of invalid packet. Drop them
here.

Enable dnstap plugin to insert other plugin's specific data into extra field of tap.Dnstap message (#1101)

* Add custom data into dnstap context

* Fix error and fix UT compile errors

* Add UTs

* Change as per review comments.  Use boolean to indicate which Dnstap message to send out

* Merge with master and fix lint warning

* Remove newline

* Fix review comments

* vendor

* code

* don't spam Travis + valid dnstap payload

* log instead of fmt

* Revert "log instead of fmt"

This reverts commit 88f09c39390e97c8f3a1f070aefee66fdf87ae48.

* log the right way

* log the final way

* minor enhancements

Don't cache these - may be lead to weird side effects.

Fixes #1113

Only output when something is wrong, not by default when you just run
with -v.

Cleans the test output a little.

* test: fix zone file

Add missing $TTL 3600 as the top.

Recent change in Go DNS made this mandatory - old behavior wasn't
standards compliant.

* and here

* adds the dnstap I/O thread and should fix a lot of mistakes

* docs

* -race test

* oops

* docs

Turn down the timeouts and numbers a bit:
FailTimeout 10s -> 5s
Future 60s -> 12s
TryDuration 60s -> 16s
The timeout for decrementing the fails in a host: 10s -> 2s

And the biggest change: don't set fails when the error is Timeout(),
meaning we loop for a bit and may try the same server again, but we
don't mark our upstream as bad, see comments in proxy.go. Testing this
with "ANY isc.org" and "MX miek.nl" we see:

~~~
::1 - [24/Sep/2017:08:06:17 +0100] "ANY IN isc.org. udp 37 false 4096" SERVFAIL qr,rd 37 10.001621221s
24/Sep/2017:08:06:17 +0100 [ERROR 0 isc.org. ANY] unreachable backend: read udp 192.168.1.148:37420->8.8.8.8:53: i/o timeout

::1 - [24/Sep/2017:08:06:17 +0100] "MX IN miek.nl. udp 37 false 4096" NOERROR qr,rd,ra,ad 170 35.957284ms

127.0.0.1 - [24/Sep/2017:08:06:18 +0100] "ANY IN isc.org. udp 37 false 4096" SERVFAIL qr,rd 37 10.002051726s
24/Sep/2017:08:06:18 +0100 [ERROR 0 isc.org. ANY] unreachable backend: read udp 192.168.1.148:54901->8.8.8.8:53: i/o timeout

::1 - [24/Sep/2017:08:06:19 +0100] "MX IN miek.nl. udp 37 false 4096" NOERROR qr,rd,ra,ad 170 56.848416ms
127.0.0.1 - [24/Sep/2017:08:06:21 +0100] "MX IN miek.nl. udp 37 false 4096" NOERROR qr,rd,ra,ad 170 48.118349ms
::1 - [24/Sep/2017:08:06:21 +0100] "MX IN miek.nl. udp 37 false 4096" NOERROR qr,rd,ra,ad 170 1.055172915s
~~~

So the ANY isc.org queries show up twice, because we retry internally -
this is I think WAI.

The `miek.nl MX` queries are just processed normally as no backend is
marked as unreachable.

May fix #1035 #486

* healhcheck: various cleanups

Network wasn't used. IgnorePaths wasn't used. Move checkdown function to
common function shared between proxy protocols. And some naming fixed.

Also reset the Fails on a succesful healthcheck back to 0.

remove newlines from log

* compile

* fix test

* Use gometalinter and enforcing go fmt/lint/vet

Before this PR go fmt is enabled, go lint is suggest only.
From time to time we have to manually check for go lint and go vet
for any issues.

This fix uses gometalinter and enforcing go fmt/lint/vet.
Several reasons:
- gometalinter could handle multiple linters concurrently
- gometalinter supports suppression with `// nolint[: <linter>]`

Previously one reason we didn't enable go lint was due to the
```
warning: context.Context should be the first parameter of a function (golint)
```
this is now possible with gometalinter and `// nolint: golint` (See changes).

This fix also discovered several go vet issues and fixes it.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Fix several issues reported by gometalinter (go vet)

This commit fixes several issues reported by gometalinter (go vet).
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Increase deadline
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

This fix address several issues related to golint/vet/misspell.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>