1 files changed, 114 insertions, 0 deletions
diff --git a/sd_daemon/notify_linux.go b/sd_daemon/notify_linux.go
new file mode 100644
index 0000000..903f1ad
--- /dev/null
+++ b/sd_daemon/notify_linux.go
@@ -0,0 +1,114 @@
+// Incorporates: git://github.com/docker/docker.git 18c7c67308bd4a24a41028e63c2603bb74eac85e pkg/systemd/sd_notify.go
+// Incorporates: git://github.com/coreos/go-systemd.git a606a1e936df81b70d85448221c7b1c6d8a74ef1 daemon/sdnotify.go
+//
+// Copyright 2013, 2015 Docker, Inc.
+// Copyright 2014 CoreOS, Inc.
+// Copyright 2015-2019 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.
+
+// +build linux
+
+package sd_daemon
+
+import (
+	"bytes"
+	"net"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func (msg Notification) send(unsetEnv bool) error {
+	if unsetEnv {
+		defer func() { _ = os.Unsetenv("NOTIFY_SOCKET") }()
+	}
+
+	socketAddr := &net.UnixAddr{
+		Name: os.Getenv("NOTIFY_SOCKET"),
+		Net:  "unixgram",
+	}
+
+	if socketAddr.Name == "" {
+		return ErrDisabled
+	}
+
+	conn, err := socketUnixgram(socketAddr.Name)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = conn.Close() }()
+
+	var cmsgs [][]byte
+
+	if len(msg.Files) > 0 {
+		fds := make([]int, len(msg.Files))
+		for i := range msg.Files {
+			fds[i] = int(msg.Files[i].Fd())
+		}
+		cmsg := unix.UnixRights(fds...)
+		cmsgs = append(cmsgs, cmsg)
+	}
+
+	havePid := msg.PID > 0 && msg.PID != os.Getpid()
+	if havePid {
+		cmsg := unix.UnixCredentials(&unix.Ucred{
+			Pid: int32(msg.PID),
+			Uid: uint32(os.Getuid()),
+			Gid: uint32(os.Getgid()),
+		})
+		cmsgs = append(cmsgs, cmsg)
+	}
+
+	// If the 2nd argument is empty, this is equivalent to
+	//
+	//    conn, _ := net.DialUnix(socketAddr.Net, nil, socketAddr)
+	//    conn.Write([]byte(msg.State))
+	_, _, err = conn.WriteMsgUnix([]byte(msg.State), bytes.Join(cmsgs, nil), socketAddr)
+
+	if err != nil && havePid {
+		// Maybe it failed because we don't have privileges to
+		// spoof our pid; retry without spoofing the pid.
+		//
+		// I'm not too happy that we do this silently without
+		// notifying the caller, but that's what
+		// sd_pid_notify_with_fds does.
+		cmsgs = cmsgs[:len(cmsgs)-1]
+		_, _, err = conn.WriteMsgUnix([]byte(msg.State), bytes.Join(cmsgs, nil), socketAddr)
+	}
+
+	return err
+}
+
+// socketUnixgram wraps socket(2), but doesn't bind(2) or connect(2)
+// the socket to anything.  This is an ugly hack because none of the
+// functions in "net" actually allow you to get a AF_UNIX socket not
+// bound/connected to anything.
+//
+// At some point you begin to question if it is worth it to keep up
+// the high-level interface of "net", and messing around with FileConn
+// and UnixConn.  Maybe we just drop to using unix.Socket and
+// unix.SendmsgN directly.
+func socketUnixgram(name string) (*net.UnixConn, error) {
+	fd, err := unix.Socket(unix.AF_UNIX, unix.SOCK_DGRAM|unix.SOCK_CLOEXEC, 0)
+	if err != nil {
+		return nil, os.NewSyscallError("socket", err)
+	}
+	defer unix.Close(fd)
+	conn, err := net.FileConn(os.NewFile(uintptr(fd), name))
+	if err != nil {
+		return nil, err
+	}
+	unixConn := conn.(*net.UnixConn)
+	return unixConn, nil
+}