64 lines
1.8 KiB
Go
64 lines
1.8 KiB
Go
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// Copyright (C) 2023-2024 Umorpha Systems
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// SPDX-License-Identifier: AGPL-3.0-or-later
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package main
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import (
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"fmt"
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"net"
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"os"
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"strconv"
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"strings"
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sd "git.lukeshu.com/go/libsystemd/sd_daemon"
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)
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// netListen is like [net.Listen], but with support for our special
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// "fd" address family.
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//
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// The purpose of doing this is that for development I really want to
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// be able to have it listen on a TCP port, but for actual deployment
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// I want it to be able to accept an already-opened socket from
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// systemd, and so I wrote a reasonably genereral solution.
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//
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// Did I avoid unnecessary complexity writing special-purpose code, or
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// did I introduce it by failing to remember that YAGNI?
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func netListen(stype, saddr string) (net.Listener, error) {
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switch stype {
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case "fd":
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switch saddr {
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case "stdin", "0":
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return net.FileListener(os.Stdin)
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case "stdout", "1":
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return net.FileListener(os.Stdout)
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case "stderr", "2":
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return net.FileListener(os.Stderr)
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case "systemd":
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sdFds := sd.ListenFds(true)
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if len(sdFds) == 0 {
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return nil, fmt.Errorf("fd:systemd given, but no systemd file descriptors passed in")
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}
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return net.FileListener(sdFds[0])
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default:
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if fd, _ := strconv.Atoi(saddr); fd > 0 {
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return net.FileListener(os.NewFile(uintptr(fd), fmt.Sprintf("/dev/fd/%d", fd)))
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}
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if name, ok := strings.CutPrefix(saddr, "systemd:"); ok {
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sdFiles := sd.ListenFds(true)
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for _, file := range sdFiles {
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if file.Name() == name {
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return net.FileListener(file)
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}
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}
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if n, err := strconv.Atoi(name); err == nil && n >= 0 && n < len(sdFiles) {
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return net.FileListener(sdFiles[n])
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}
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return nil, fmt.Errorf("does not match any systemd file descriptor: %q", name)
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}
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return nil, fmt.Errorf("invalid file descriptor name: %q", saddr)
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}
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default:
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return net.Listen(stype, saddr)
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}
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}
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