* Revert "pkg/typify: empty messages are OtherError (#1531)"

This reverts commit fc1d73ff.

* plugin/cache: add failsafeTTL

If we can not see what TTL we should put on a message to be cached, use
5 seconds as minimal TTL. We used to apply the maximum TTL to these
  messages.

* add noendpoints option

* go fmt

* add upstream

* docs

* tests

* move file, auto, secondary to new upstream

* include context in request

Messages with nothing in them are considered OtherError, they can not
serve any purpose for normal clients (i.e. dyn update or notifies might
have a use for them).

Also update a test in the cache plugin, so that we explicitaly test for
this case.

* add namespace watch

* start ns watch, and add sync check

* plugin/forward: on demand healtchecking

Only start doing health checks when we encouner an error (any error).
This uses the new pluing/pkg/up package to abstract away the actual
checking. This reduces the LOC quite a bit; does need more testing, unit
testing and tcpdumping a bit.

* fix tests

* Fix readme

* Use pkg/up for healthchecks

* remove unused channel

* more cleanups

* update readme

* * Again do go generate and go build; still referencing the wrong forward
  repo? Anyway fixed.
* Use pkg/up for doing the healtchecks to cut back on unwanted queries
  * Change up.Func to return an error instead of a boolean.
  * Drop the string target argument as it doesn't make sense.
* Add healthcheck test on failing to get an upstream answer.

TODO(miek): double check Forward and Lookup and how they interact with
HC, and if we correctly call close() on those

* actual test

* Tests here

* more tests

* try getting rid of host

* Get rid of the host indirection

* Finish removing hosts

* moar testing

* import fmt

* field is not used

* docs

* move some stuff

* bring back health_check

* maxfails=0 test

* git and merging, bah

* review

* add upstream @self and loop count

* 1st round of feedback

* allow argless upstream

* update test

* readmes

* feedback

* prevent nil pointer when query frpc client that could not open

* add UT checking we can now safely request DNS query on an invalid hostname, query for gRPC connection

* fix ortograph

* fix format

* fix package declaration, fix UT - grpclogger, use fatalf, build pool with known addresses

* type, useless error check - after review

* Extend bind to allow multiple addresses. UTs added. Changes the log for server starting, adding address when available

* update readme for bind

* fixes after review

* minor fix on readme

* accept multiple BIND directives in blocserver, consolidate the addresses

* fixes after review - format logging server address, variable names

This fix enables goimports check and fixes several imports format
so that the import sections are prettier, e.g.:
```
 import (
-       "github.com/miekg/dns"
        "regexp"
        "strconv"
        "strings"
+
+       "github.com/miekg/dns"
 )
```
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Stop noisy modifications

* Review comments, tests

* More coverage

* vet

* Make it obvious new port name is not a typo

Remove `fallthrough` from the federation example in the README.  `fallthrough` isn't needed here and has no effect (federation has an implicit fallthrough for non-federated queries).  
It's inclusion is confusing.

Reloading should work (kill -TERM reload the coredns process), but a lot
of plugins can't handle it proper. Disable to reload plugin until we fix
(most) of the plugins

Pinged me, still interested in helping out \o/

This fix add a test case for case insensitive/preserving with
whoami plugin.

This fix is part of the effort for 1403.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* plugin/kubernetes: axfr

Hook up dynamic SOA serial by setting ResourceEventHandlerFuncs in
dnsController.

Add prototype of returns msg.Services via the Transfer function. Leave
expanding this to RRs out of scope for a bit.

* plugin/kubernetes: axfr

Respond to AXFR queries

* Fixing race condition

* Fixing instantiation of dnstest writer

* Updates from review

Forward still wasn't right; run make -f Makefile.doc, as well for good
measure.

Retweak this a little to make it slightly easier to *not* forget this,
but it is hardly perfect. Should probably make it an interface a plugin
can implement and then unblock if we see that interface.

We have OWNERS file throughout the repo. The top level OWNERS file
replaces the MAINTAINERS file (sans email addresses that is).

This should have everyone, but the process was quite manual. The rename
from middleware -> plugin also meant I had to do some extra digging on
who actually submitted the PR. I also double checked the current list of
people with commit access.

Every plugin now has an OWNERS, except *reverse*. I'll file a bug for
that.

* remove setdo

* gofmt

* allow only one k8s section

* add test

* plugin/forward: add it

This moves coredns/forward into CoreDNS. Fixes as a few bugs, adds a
policy option and more tests to the plugin.

Update the documentation, test IPv6 address and add persistent tests.

* Always use random policy when spraying

* include scrub fix here as well

* use correct var name

* Code review

* go vet

* Move logging to metrcs

* Small readme updates

* Fix readme

This adds a generic way of start a check function to check a backend.
This package can be used to kick off healthchecks. The package makes
sure only 1 is run at any one time.

It should allow for:
See upstream error -> kick off healthcheck

and not to worry about overwhelming the upstream with a barrage of
queries.

Add man-pages for the new plugins.

* tune usage of var global, add limit to options

* update readme for minimal values

* useless change to quick-off codecov

* fix msgs for min values and tune the flag for end of reload usage, with a 'maybe' option

* adding UT for min values, adding MD5 of corefile on the log

* add new policy always_first to mimic windows dns resolvers
fill documentation, add UT and cleanup fmt

* change name of policy from always_first to first. Update docs

As plugin/proxy always returns compressed messages, it's important to
set this before calling Scrub(), as some messages will be unnecessarily
truncated otherwise.

HTTP healthchecking will be implicitely activated for proxy upstream
hosts, even if not configured. The README states that not using the
health_check directive will disable HTTP healthchecks though.

It seems to me that the availability of the HealthCheck.Path attribute
is used as indicator whether HTTP healthchecks should be used or not.
The normalizeCheckURL() function didn't check that attribute though,
always returning a CheckURL. This would increase the healthcheck failure
on every third failure in plugin/proxy, without any possibility for the
upstream host to be marked as healthy again. This would eventually
remove all upstream hosts from the serving pool.

This adds the inital top-level OWNERS file. Each plugin should also get
one, but that will be more work.

Ref: #1454