* Add edns0 code rewrite

* check arg count

* change `new`; set EDNS0 if request doesn't have it set

* change set to replace_or_append

* change to append_or_replace

* return error in new

* update documents

* fixt UT

* return error

* go fmt

* Rework for more general EDNS0 use

Also changed how rules are created and validated. Implements
EDNS0 NSID in addition to local.

* go fmt

* README updates, NSID tests and fixes

* gofmt -s -w

* Fix tests for rewrite syntax change

* Add tests, fix error message

* Review nits

* Missed on nit

* More tests, integration test, fix edns0 parse issue

* Fix README, use RewriteIgnored

* go fmt

In both etcd and k8s don't error log NXDOMAIN as this log spams the logs
for no good reason.

Fixes #568

Better long term solution is log rate limiting for both *log* and
*error*.

Set of small cleanups.

This fix updates the Makefile to add the `go lint` check
for the build. This fix also fixes several go lint issues.

NOTE: This fix does not enforce `go lint` (suggestion only).
This fix also ignores the `go lint` error:
```
middleware/middleware.go:72:1: context.Context should be the first parameter of a function
```
as it requires too many changes in API.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add CNCF Code of Conduct
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

* Fix reference to CNCF

https://cncf.io

This fixes a crash when we resolve (or try to) an external CNAME
when no proxy is set.

Add test as well.

Make the docker release part of the normal CoreDNS release

* checkpoint

* Pass context through ServeDNS, enable gRPC tracing

* Fix types and make tracer available to proxy. go fmt

* Fix imports

* Use the DoNotStartTrace option

* Change to SpanFilter from DoNotStartTrace

* Use new name (IncludeSpan)

* Final names

* Add tests; fix possible client/conn leaks in grpc

* go fmt

This fix adds the dependency of `go fmt` in `Makefile`
so that any new check in will have to properly fmt the source code
with `gofmt -s -w`.

* Gofmt all code

* fmt

This fix fixes incorrect link of the CodeCov in README.md.

* linter fixes

* Golint and format code

* fmt

This fix fixes import path from
`github.com/miekg/coredns`
->
`github.com/coredns/coredns`

This fix fixes badge in README.md so that it will correctly reflect
github.com/coredns/coredns

We now sit under coredns/coredns this means the logo can be in it's
repository.

* middleware/metrics: survive restart

Keep the handler running during restart. Stopping and starting the
handler results in "address in use" - sometimes, meaning the reload
will be flaky. In turn this behavior means any changes to the monitor
stanza are not picked up.

* remove resync

* Document fallthrough and fix *reverse*

While documenting the fallthrough behavior and testing it I noticed
the did not properly work. This PR does a tiny bit too much as it

- Documents fallthrough
- Fixes fallthrough in reverse
- Makes directives_generate complain on duplicate priorities
- Moved reverse *before* file in middleware.cfg
- Add a test that tests the reverse fallthrough behavior with a file
  backend

Fixes #515

* ....and fix the tests

Add additional section processing for MX and SRV records. Update the
tests.

* all-middleware-equal

* Revert "all-middleware-equal"

This reverts commit ee77b2a9816b1953a19fefb863875399aacd0c2a.

* middleware: treat external and local the same

Make the middleware generation simpler and also specify the local
middleware, meaning that it can now be removed as well. Simplify
the code a bit and regen everything.

* remove lineNR, not used

* server: fix data race

This fixes the detected race.

Fixes #534

* Remove the listener and packetconn from Server

There does not seem a need to store the listener and packetconn again
in the Server structure. The dns.Servers already has access to them
and can also shutdown the handlers.

When using an external middleware, the generated file was failing to compile.
The issue is a typo in directives_generate.go that left imports with an
unterminated string.

* WIP: Client-side of gRPC proxy

* Add tests

* gofmt

* Implement OnShutdown; add a little logging

* Update for context in Exchange change

* go fmt

* Update README

* Review comments

* Compiling is good

* More README improvements

Remove the "gen" directory and move directives_generate.go out of it.
Add a build ignore tag so it isn't build by default. Cleanup the go gen
invocations so there are not seen as package docs.

Simplify the code a bit and don't run go gen twice.

* middleware/proxy: give Exchange a context

Make context.Context the first paramater in the Exchange method.
This is inline with all other query functions.

* up the version

* core: make coredns.Server a caddy.GracefulServer

We needed to also implement the Address() method.

Fixes: #519

* Add compile time check if we implement caddy.GracefulServer

* Check if we should shutdown

* middleware/reverse: random updates

Make the documentation somewhat shorter (and hopefully clearer in the
process). Also to be on-par with the *auto* middleware, start counting
the referenced zones from 1 (instead of 0).
Some variable cleanups and use the NextOrFailure in the ServeDNS
function.

* More TODOs

* fix k8s next middleware chaining

* add chain to integration tests

* if nit