1 files changed, 84 insertions, 13 deletions
diff --git a/systemd-timesyncd-wait.go b/systemd-timesyncd-wait.go
index 9275502..f5327ff 100644
--- a/systemd-timesyncd-wait.go
+++ b/systemd-timesyncd-wait.go
@@ -1,29 +1,100 @@
+// Copyright 2017 Luke Shumaker
+//
+// For just ListenFds:
+//
+// Copyright 2015 CoreOS, Inc.
+// Copyright 2015-2016 Luke Shumaker
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package main
 
 import (
+	"fmt"
 	"net"
 	"os"
+	"strconv"
+	"strings"
+
+	unix "syscall"
 )
 
+// ListenFds returns a list of file descriptors passed in by the
+// service manager as part of the socket-based activation logic.
+//
+// If unsetEnv is true, then (regardless of whether the function call
+// itself succeeds or not) it will unset the environmental variables
+// LISTEN_FDS and LISTEN_PID, which will cause further calls to this
+// function to fail.
+//
+// In the case of an error, this function returns nil.
+func ListenFds(unsetEnv bool) []*os.File {
+	if unsetEnv {
+		defer func() {
+			_ = os.Unsetenv("LISTEN_PID")
+			_ = os.Unsetenv("LISTEN_FDS")
+			_ = os.Unsetenv("LISTEN_FDNAMES")
+		}()
+	}
+
+	pid, err := strconv.Atoi(os.Getenv("LISTEN_PID"))
+	if err != nil || pid != os.Getpid() {
+		return nil
+	}
+
+	nfds, err := strconv.Atoi(os.Getenv("LISTEN_FDS"))
+	if err != nil || nfds < 1 {
+		return nil
+	}
+
+	names := strings.Split(os.Getenv("LISTEN_FDNAMES"), ":")
+
+	files := make([]*os.File, 0, nfds)
+	for i := 0; i < nfds; i++ {
+		fd := i + 3
+		unix.CloseOnExec(fd)
+		name := "unknown"
+		if i < len(names) {
+			name = names[i]
+		}
+		files = append(files, os.NewFile(uintptr(fd), name))
+	}
+
+	return files
+}
+
 func main() {
-	sync_sockname := "/run/timesyncd/time-sync.sock"
+	files := ListenFds(false)
+	if len(files) != 1 {
+		fmt.Fprintf(os.Stderr, "expected 1 fd, got %d\n", len(files))
+		os.Exit(1)
+	}
 
-	sync_sock, err := net.ListenUnixgram("unixgram", &net.UnixAddr{Net: "unixgram", Name: sync_sockname})
+	sync_sock, err := net.FileConn(files[0])
 	if err != nil {
-		os.Stderr.WriteString(err.Error())
-		os.Stderr.Write([]byte{'\n'})
+		fmt.Fprintln(os.Stderr, err)
 		os.Exit(127)
 	}
 
 	var dat [4096]byte
-	n, err := sync_sock.Read(dat[:])
-	if err != nil {
-		os.Stderr.WriteString(err.Error())
-		os.Stderr.Write([]byte{'\n'})
-		os.Exit(127)
-	}
-	if string(dat[:n]) != "READY=1" {
-		os.Exit(127)
+	for {
+		n, err := sync_sock.Read(dat[:])
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(127)
+		}
+		if n > 0 {
+			os.Exit(0)
+		}
 	}
-	os.Exit(0)
 }