Make CoreDNS a server type plugin for Caddy (#220)

* Make CoreDNS a server type plugin for Caddy

Remove code we don't need and port all middleware over. Fix all tests
and rework the documentation.

Also make `go generate` build a caddy binary which we then copy into
our directory. This means `go build`-builds remain working as-is.

And new etc instances in each etcd test for better isolation.
Fix more tests and rework test.Server with the newer support Caddy offers.

Fix Makefile to support new mode of operation.

1 files changed, 0 insertions, 102 deletions

diff --git a/core/helpers.go b/core/helpers.go
deleted file mode 100644
index 82a0150af..000000000
--- a/core/helpers.go
+++ /dev/null
@@ -1,102 +0,0 @@
-package core
-
-import (
-	"bytes"
-	"fmt"
-	"io/ioutil"
-	"log"
-	"os"
-	"os/exec"
-	"runtime"
-	"strconv"
-	"strings"
-	"sync"
-)
-
-// isLocalhost returns true if host looks explicitly like a localhost address.
-func isLocalhost(host string) bool {
-	return host == "localhost" || host == "::1" || strings.HasPrefix(host, "127.")
-}
-
-// checkFdlimit issues a warning if the OS max file descriptors is below a recommended minimum.
-func checkFdlimit() {
-	const min = 4096
-
-	// Warn if ulimit is too low for production sites
-	if runtime.GOOS == "linux" || runtime.GOOS == "darwin" {
-		out, err := exec.Command("sh", "-c", "ulimit -n").Output() // use sh because ulimit isn't in Linux $PATH
-		if err == nil {
-			// Note that an error here need not be reported
-			lim, err := strconv.Atoi(string(bytes.TrimSpace(out)))
-			if err == nil && lim < min {
-				fmt.Printf("Warning: File descriptor limit %d is too low for production sites. At least %d is recommended. Set with \"ulimit -n %d\".\n", lim, min, min)
-			}
-		}
-	}
-}
-
-// signalSuccessToParent tells the parent our status using pipe at index 3.
-// If this process is not a restart, this function does nothing.
-// Calling this function once this process has successfully initialized
-// is vital so that the parent process can unblock and kill itself.
-// This function is idempotent; it executes at most once per process.
-func signalSuccessToParent() {
-	signalParentOnce.Do(func() {
-		if IsRestart() {
-			ppipe := os.NewFile(3, "")               // parent is reading from pipe at index 3
-			_, err := ppipe.Write([]byte("success")) // we must send some bytes to the parent
-			if err != nil {
-				log.Printf("[ERROR] Communicating successful init to parent: %v", err)
-			}
-			ppipe.Close()
-		}
-	})
-}
-
-// signalParentOnce is used to make sure that the parent is only
-// signaled once; doing so more than once breaks whatever socket is
-// at fd 4 (the reason for this is still unclear - to reproduce,
-// call Stop() and Start() in succession at least once after a
-// restart, then try loading first host of Corefile in the browser).
-// Do not use this directly - call signalSuccessToParent instead.
-var signalParentOnce sync.Once
-
-// corefileGob maps bind address to index of the file descriptor
-// in the Files array passed to the child process. It also contains
-// the corefile contents and other state needed by the new process.
-// Used only during graceful restarts where a new process is spawned.
-type corefileGob struct {
-	ListenerFds            map[string]uintptr
-	Corefile               Input
-	OnDemandTLSCertsIssued int32
-}
-
-// IsRestart returns whether this process is, according
-// to env variables, a fork as part of a graceful restart.
-func IsRestart() bool {
-	return os.Getenv("COREDNS_RESTART") == "true"
-}
-
-// writePidFile writes the process ID to the file at PidFile, if specified.
-func writePidFile() error {
-	pid := []byte(strconv.Itoa(os.Getpid()) + "\n")
-	return ioutil.WriteFile(PidFile, pid, 0644)
-}
-
-// CorefileInput represents a Corefile as input
-// and is simply a convenient way to implement
-// the Input interface.
-type CorefileInput struct {
-	Filepath string
-	Contents []byte
-	RealFile bool
-}
-
-// Body returns c.Contents.
-func (c CorefileInput) Body() []byte { return c.Contents }
-
-// Path returns c.Filepath.
-func (c CorefileInput) Path() string { return c.Filepath }
-
-// IsFile returns true if the original input was a real file on the file system.
-func (c CorefileInput) IsFile() bool { return c.RealFile }