mirror of
https://github.com/tailscale/tailscale.git
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60 lines
1.5 KiB
Go
60 lines
1.5 KiB
Go
// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package dns
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import (
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"bufio"
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"bytes"
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"os"
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"os/exec"
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"tailscale.com/types/logger"
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)
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// isResolvconfActive indicates whether the system appears to be using resolvconf.
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// If this is true, then directManager should be avoided:
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// resolvconf has exclusive ownership of /etc/resolv.conf.
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func isResolvconfActive() bool {
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_, err := exec.LookPath("resolvconf")
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if err != nil {
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return false
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}
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f, err := os.Open("/etc/resolv.conf")
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if err != nil {
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return false
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}
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defer f.Close()
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scanner := bufio.NewScanner(f)
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for scanner.Scan() {
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line := scanner.Bytes()
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// Look for the word "resolvconf" until comments end.
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if len(line) > 0 && line[0] != '#' {
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return false
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}
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if bytes.Contains(line, []byte("resolvconf")) {
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return true
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}
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}
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return false
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}
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func newResolvconfManager(logf logger.Logf) OSConfigurator {
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_, err := exec.Command("resolvconf", "--version").CombinedOutput()
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if err != nil {
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if exitErr, ok := err.(*exec.ExitError); ok && exitErr.ExitCode() == 99 {
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// Debian resolvconf doesn't understand --version, and
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// exits with a specific error code.
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return newDebianResolvconfManager(logf)
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}
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}
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// If --version works, or we got some surprising error while
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// probing, use openresolv. It's the more common implementation,
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// so in cases where we can't figure things out, it's the least
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// likely to misbehave.
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return newOpenresolvManager()
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}
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