Healthcheck moved to HTTP control server

internal/server/health.go

@@ -0,0 +1,27 @@
+package server
+
+import (
+	"fmt"
+	"net/http"
+)
+
+func (s *server) handleHealth(w http.ResponseWriter) {
+	// TODO option to disable
+	// TODO use mullvad API if current provider is Mullvad
+	ips, err := s.lookupIP("github.com")
+	var errorMessage string
+	switch {
+	case err != nil:
+		errorMessage = fmt.Sprintf("cannot resolve github.com (%s)", err)
+	case len(ips) == 0:
+		errorMessage = "resolved no IP addresses for github.com"
+	default: // success
+		w.WriteHeader(http.StatusOK)
+		return
+	}
+	s.logger.Warn(errorMessage)
+	w.WriteHeader(http.StatusInternalServerError)
+	if _, err := w.Write([]byte(errorMessage)); err != nil {
+		s.logger.Warn(err)
+	}
+}

internal/server/server.go

@@ -3,6 +3,7 @@ package server
 import (
 	"context"
 	"fmt"
+	"net"
 	"net/http"
 	"sync"
 	"time"
@@ -22,6 +23,7 @@ type server struct {
 	restartUnbound     func()
 	getOpenvpnSettings func() settings.OpenVPN
 	getPortForwarded   func() uint16
+	lookupIP           func(host string) ([]net.IP, error)
 }
 
 func New(address string, logger logging.Logger, restartOpenvpn, restartUnbound func(),
@@ -33,6 +35,7 @@ func New(address string, logger logging.Logger, restartOpenvpn, restartUnbound f
 		restartUnbound:     restartUnbound,
 		getOpenvpnSettings: getOpenvpnSettings,
 		getPortForwarded:   getPortForwarded,
+		lookupIP:           net.LookupIP,
 	}
 }
 
@@ -71,6 +74,8 @@ func (s *server) makeHandler() http.HandlerFunc {
 				s.handleGetPortForwarded(w)
 			case "/openvpn/settings":
 				s.handleGetOpenvpnSettings(w)
+			case "/health":
+				s.handleHealth(w)
 			default:
 				routeDoesNotExist(s.logger, w, r)
 			}