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fix(runner): safely reload DAWG files during rotation #181

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fix(runner): safely reload DAWG files during rotation #181

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7 changes: 4 additions & 3 deletions pkg/runner/runner.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1786,16 +1786,17 @@ func (wkd *wellKnownDomainsTracker) sendUpdate(ipBytes []byte, msg *dns.Msg, daw
func (wkd *wellKnownDomainsTracker) rotateTracker(edm *dnstapMinimiser, dawgFile string, rotationTime time.Time) (*wellKnownDomainsData, error) {
dawgFileChanged := false
var dawgFinder dawg.Finder
var dawgModTime time.Time

fileInfo, err := os.Stat(dawgFile)
if err != nil {
return nil, fmt.Errorf("rotateTracker: unable to stat dawgFile '%s': %w", dawgFile, err)
}

if fileInfo.ModTime() != wkd.dawgModTime {
dawgFinder, err = dawg.Load(dawgFile)
dawgFinder, dawgModTime, err = loadDawgFile(dawgFile)
if err != nil {
return nil, fmt.Errorf("rotateTracker: dawg.Load(): %w", err)
return nil, fmt.Errorf("rotateTracker: loadDawgFile(): %w", err)
}
dawgFileChanged = true
edm.log.Info("dawg file modification changed, will reload file", "prev_time", wkd.dawgModTime, "cur_time", fileInfo.ModTime())
Expand All @@ -1810,7 +1811,7 @@ func (wkd *wellKnownDomainsTracker) rotateTracker(edm *dnstapMinimiser, dawgFile
wkd.m = map[int]*histogramData{}
if dawgFileChanged {
wkd.dawgFinder = dawgFinder
wkd.dawgModTime = fileInfo.ModTime()
wkd.dawgModTime = dawgModTime
prevWKD.dawgIsRotated = true
}
wkd.mutex.Unlock()
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36 changes: 36 additions & 0 deletions pkg/runner/runner_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ package runner
import (
"bytes"
"encoding/binary"
"errors"
"flag"
"io"
"log/slog"
Expand Down Expand Up @@ -215,6 +216,41 @@ func TestWKD(t *testing.T) {
}
}

func TestRotateTrackerUsesSafeDawgLoader(t *testing.T) {
dBuilder := dawg.New()
dBuilder.Add("example.com.")
dFinder := dBuilder.Finish()

dawgFile := t.TempDir() + "/well-known-domains.dawg"
if _, err := dFinder.Save(dawgFile); err != nil {
t.Fatalf("Save: %s", err)
}
fileInfo, err := os.Stat(dawgFile)
if err != nil {
t.Fatalf("Stat: %s", err)
}

wkd, err := newWellKnownDomainsTracker(dFinder, fileInfo.ModTime())
if err != nil {
t.Fatalf("newWellKnownDomainsTracker: %s", err)
}
edm := &dnstapMinimiser{
log: slog.New(slog.NewTextHandler(io.Discard, nil)),
}

if err := os.WriteFile(dawgFile, nil, 0o644); err != nil {
t.Fatalf("WriteFile: %s", err)
}
nextModTime := fileInfo.ModTime().Add(time.Second)
if err := os.Chtimes(dawgFile, nextModTime, nextModTime); err != nil {
t.Fatalf("Chtimes: %s", err)
}

if _, err := wkd.rotateTracker(edm, dawgFile, time.Now()); !errors.Is(err, errEmptyDawgFile) {
t.Fatalf("rotateTracker error have: %v, want: %v", err, errEmptyDawgFile)
}
}

func TestIgnoredClientIPsValid(t *testing.T) {
discardLogger := slog.NewTextHandler(io.Discard, nil)
logger := slog.New(discardLogger)
Expand Down