1 files changed, 166 insertions, 0 deletions
diff --git a/core/restart.go b/core/restart.go
new file mode 100644
index 000000000..82567d35c
--- /dev/null
+++ b/core/restart.go
@@ -0,0 +1,166 @@
+// +build !windows
+
+package core
+
+import (
+	"bytes"
+	"encoding/gob"
+	"errors"
+	"io/ioutil"
+	"log"
+	"net"
+	"os"
+	"os/exec"
+	"path"
+	"sync/atomic"
+
+	"github.com/miekg/coredns/core/https"
+)
+
+func init() {
+	gob.Register(CaddyfileInput{})
+}
+
+// Restart restarts the entire application; gracefully with zero
+// downtime if on a POSIX-compatible system, or forcefully if on
+// Windows but with imperceptibly-short downtime.
+//
+// The restarted application will use newCaddyfile as its input
+// configuration. If newCaddyfile is nil, the current (existing)
+// Caddyfile configuration will be used.
+//
+// Note: The process must exist in the same place on the disk in
+// order for this to work. Thus, multiple graceful restarts don't
+// work if executing with `go run`, since the binary is cleaned up
+// when `go run` sees the initial parent process exit.
+func Restart(newCaddyfile Input) error {
+	log.Println("[INFO] Restarting")
+
+	if newCaddyfile == nil {
+		caddyfileMu.Lock()
+		newCaddyfile = caddyfile
+		caddyfileMu.Unlock()
+	}
+
+	// Get certificates for any new hosts in the new Caddyfile without causing downtime
+	err := getCertsForNewCaddyfile(newCaddyfile)
+	if err != nil {
+		return errors.New("TLS preload: " + err.Error())
+	}
+
+	if len(os.Args) == 0 { // this should never happen, but...
+		os.Args = []string{""}
+	}
+
+	// Tell the child that it's a restart
+	os.Setenv("CADDY_RESTART", "true")
+
+	// Prepare our payload to the child process
+	cdyfileGob := caddyfileGob{
+		ListenerFds:            make(map[string]uintptr),
+		Caddyfile:              newCaddyfile,
+		OnDemandTLSCertsIssued: atomic.LoadInt32(https.OnDemandIssuedCount),
+	}
+
+	// Prepare a pipe to the fork's stdin so it can get the Caddyfile
+	rpipe, wpipe, err := os.Pipe()
+	if err != nil {
+		return err
+	}
+
+	// Prepare a pipe that the child process will use to communicate
+	// its success with us by sending > 0 bytes
+	sigrpipe, sigwpipe, err := os.Pipe()
+	if err != nil {
+		return err
+	}
+
+	// Pass along relevant file descriptors to child process; ordering
+	// is very important since we rely on these being in certain positions.
+	extraFiles := []*os.File{sigwpipe} // fd 3
+
+	// Add file descriptors of all the sockets
+	serversMu.Lock()
+	for i, s := range servers {
+		extraFiles = append(extraFiles, s.ListenerFd())
+		cdyfileGob.ListenerFds[s.Addr] = uintptr(4 + i) // 4 fds come before any of the listeners
+	}
+	serversMu.Unlock()
+
+	// Set up the command
+	cmd := exec.Command(os.Args[0], os.Args[1:]...)
+	cmd.Stdin = rpipe      // fd 0
+	cmd.Stdout = os.Stdout // fd 1
+	cmd.Stderr = os.Stderr // fd 2
+	cmd.ExtraFiles = extraFiles
+
+	// Spawn the child process
+	err = cmd.Start()
+	if err != nil {
+		return err
+	}
+
+	// Immediately close our dup'ed fds and the write end of our signal pipe
+	for _, f := range extraFiles {
+		f.Close()
+	}
+
+	// Feed Caddyfile to the child
+	err = gob.NewEncoder(wpipe).Encode(cdyfileGob)
+	if err != nil {
+		return err
+	}
+	wpipe.Close()
+
+	// Determine whether child startup succeeded
+	answer, readErr := ioutil.ReadAll(sigrpipe)
+	if answer == nil || len(answer) == 0 {
+		cmdErr := cmd.Wait() // get exit status
+		log.Printf("[ERROR] Restart: child failed to initialize (%v) - changes not applied", cmdErr)
+		if readErr != nil {
+			log.Printf("[ERROR] Restart: additionally, error communicating with child process: %v", readErr)
+		}
+		return errIncompleteRestart
+	}
+
+	// Looks like child is successful; we can exit gracefully.
+	return Stop()
+}
+
+func getCertsForNewCaddyfile(newCaddyfile Input) error {
+	// parse the new caddyfile only up to (and including) TLS
+	// so we can know what we need to get certs for.
+	configs, _, _, err := loadConfigsUpToIncludingTLS(path.Base(newCaddyfile.Path()), bytes.NewReader(newCaddyfile.Body()))
+	if err != nil {
+		return errors.New("loading Caddyfile: " + err.Error())
+	}
+
+	// first mark the configs that are qualified for managed TLS
+	https.MarkQualified(configs)
+
+	// since we group by bind address to obtain certs, we must call
+	// EnableTLS to make sure the port is set properly first
+	// (can ignore error since we aren't actually using the certs)
+	https.EnableTLS(configs, false)
+
+	// find out if we can let the acme package start its own challenge listener
+	// on port 80
+	var proxyACME bool
+	serversMu.Lock()
+	for _, s := range servers {
+		_, port, _ := net.SplitHostPort(s.Addr)
+		if port == "80" {
+			proxyACME = true
+			break
+		}
+	}
+	serversMu.Unlock()
+
+	// place certs on the disk
+	err = https.ObtainCerts(configs, false, proxyACME)
+	if err != nil {
+		return errors.New("obtaining certs: " + err.Error())
+	}
+
+	return nil
+}