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// 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"
"syscall"
"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 {
// BUG(lukeshu): Spoofing the socket credentials is
// not implemnted on non-Linux kernels. If you are
// knowledgable about how to do this on other kernels,
// please let me know at <lukeshu@lukeshu.com>!
havePid = false
}
// 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) {
syscall.ForkLock.RLock()
fd, err := unix.Socket(unix.AF_UNIX, unix.SOCK_DGRAM, 0)
if err == nil {
syscall.CloseOnExec(fd)
}
syscall.ForkLock.RUnlock()
if err != nil {
return nil, os.NewSyscallError("socket", err)
}
defer unix.Close(fd)
if err = unix.SetNonblock(fd, true); err != nil {
return nil, os.NewSyscallError("setnonblock", err)
}
conn, err := net.FileConn(os.NewFile(uintptr(fd), name))
if err != nil {
return nil, err
}
unixConn := conn.(*net.UnixConn)
return unixConn, nil
}
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