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49eb1b5d26
The test had two problems: 1. runFileWatcher passed hardcoded "/etc/" to the inotify watcher, but the test filesystem uses a temp directory prefix. The watcher was watching the real /etc/, never seeing the test's file writes. 2. The test's watchFile used gonotify.NewDirWatcher which creates goroutines that block on real inotify syscalls. These don't work inside synctest's fake-time bubble. The test only passed standalone by accident: gonotify walks /etc/ on startup producing fake events that happened to trigger trample detection at the right time. Fix the path issue by adding ActualPath to the wholeFileFS interface, which translates logical paths (like "/etc/resolv.conf") to real filesystem paths (respecting any test prefix). Use it in runFileWatcher so the inotify watch targets the correct directory. Replace gonotify in the test with a one-shot timer that synctest can advance through fake time, reliably triggering the trample check. Fixes #19400 Change-Id: Idb252881ec24d0ab3b3c1d154dbdaf532db837d4 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
95 lines
2.5 KiB
Go
95 lines
2.5 KiB
Go
// Copyright (c) Tailscale Inc & contributors
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build linux
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package dns
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import (
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"context"
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"net/netip"
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"os"
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"path/filepath"
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"testing"
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"testing/synctest"
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"time"
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"tailscale.com/util/dnsname"
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"tailscale.com/util/eventbus/eventbustest"
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)
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func TestDNSTrampleRecovery(t *testing.T) {
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t.Cleanup(HookWatchFile.SetForTest(watchFile))
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synctest.Test(t, func(t *testing.T) {
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tmp := t.TempDir()
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if err := os.MkdirAll(filepath.Join(tmp, "etc"), 0700); err != nil {
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t.Fatal(err)
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}
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const resolvPath = "/etc/resolv.conf"
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fs := directFS{prefix: tmp}
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readFile := func(t *testing.T, path string) string {
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t.Helper()
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b, err := fs.ReadFile(path)
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if err != nil {
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t.Errorf("Reading DNS config: %v", err)
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}
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return string(b)
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}
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bus := eventbustest.NewBus(t)
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eventbustest.LogAllEvents(t, bus)
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m := newDirectManagerOnFS(t.Logf, nil, bus, fs)
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defer m.Close()
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if err := m.SetDNS(OSConfig{
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Nameservers: []netip.Addr{netip.MustParseAddr("8.8.8.8"), netip.MustParseAddr("8.8.4.4")},
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SearchDomains: []dnsname.FQDN{"ts.net.", "ts-dns.test."},
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MatchDomains: []dnsname.FQDN{"ignored."},
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}); err != nil {
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t.Fatal(err)
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}
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const want = `# resolv.conf(5) file generated by tailscale
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# For more info, see https://tailscale.com/s/resolvconf-overwrite
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# DO NOT EDIT THIS FILE BY HAND -- CHANGES WILL BE OVERWRITTEN
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nameserver 8.8.8.8
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nameserver 8.8.4.4
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search ts.net ts-dns.test
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`
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if got := readFile(t, resolvPath); got != want {
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t.Fatalf("resolv.conf:\n%s, want:\n%s", got, want)
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}
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tw := eventbustest.NewWatcher(t, bus)
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const trample = "Hvem er det som tramper på min bro?"
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if err := fs.WriteFile(resolvPath, []byte(trample), 0644); err != nil {
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t.Fatal(err)
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}
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synctest.Wait()
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if err := eventbustest.Expect(tw, eventbustest.Type[TrampleDNS]()); err != nil {
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t.Errorf("did not see trample event: %s", err)
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}
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})
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}
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// watchFile is a test implementation of the file watcher that uses a timer
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// instead of inotify. Real inotify (gonotify.NewDirWatcher) creates goroutines
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// that block on real syscalls, which don't work inside synctest's fake-time
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// bubble. Instead, we use a one-shot timer that synctest.Wait() will advance,
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// triggering a callback to check for file trampling.
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func watchFile(ctx context.Context, dir, filename string, cb func()) error {
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timer := time.NewTimer(time.Millisecond)
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defer timer.Stop()
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select {
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case <-ctx.Done():
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return ctx.Err()
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case <-timer.C:
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cb()
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}
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<-ctx.Done()
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return ctx.Err()
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}
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