1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
|
// 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() {
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.FileConn(files[0])
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(127)
}
var dat [4096]byte
for {
n, err := sync_sock.Read(dat[:])
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(127)
}
if n > 0 {
os.Exit(0)
}
}
}
|
