filtering: imp docs

internal/filtering/filter.go

@@ -90,7 +90,7 @@ func (d *DNSFilter) filterSetProperties(
 
 	filt := &filters[i]
 	log.Debug(
-		"set name to %q, url to %s, enabled to %t for filter %s",
+		"filtering: set name to %q, url to %s, enabled to %t for filter %s",
 		newList.Name,
 		newList.URL,
 		newList.Enabled,
@@ -109,7 +109,7 @@ func (d *DNSFilter) filterSetProperties(
 	filt.Name = newList.Name
 
 	if filt.URL != newList.URL {
-		if d.filterExistsIntl(newList.URL) {
+		if d.filterExistsLocked(newList.URL) {
 			return false, errFilterExists
 		}
 
@@ -142,19 +142,20 @@ func (d *DNSFilter) filterSetProperties(
 	return shouldRestart, err
 }
 
-// filterExists returns true if a filter with the same url exists in d.
+// filterExists returns true if a filter with the same url exists in d.  It's
+// safe for concurrent use.
 func (d *DNSFilter) filterExists(url string) (ok bool) {
 	d.filtersMu.RLock()
 	defer d.filtersMu.RUnlock()
 
-	r := d.filterExistsIntl(url)
+	r := d.filterExistsLocked(url)
 
 	return r
 }
 
-// filterExistsIntl returns true if d contains the filter with the same url.
-// For internal use only.
-func (d *DNSFilter) filterExistsIntl(url string) (ok bool) {
+// filterExistsLocked returns true if d contains the filter with the same url.
+// d.filtersMu is expected to be locked.
+func (d *DNSFilter) filterExistsLocked(url string) (ok bool) {
 	for _, f := range d.Filters {
 		if f.URL == url {
 			return true
@@ -177,7 +178,7 @@ func (d *DNSFilter) filterAdd(flt FilterYAML) bool {
 	defer d.filtersMu.Unlock()
 
 	// Check for duplicates
-	if d.filterExistsIntl(flt.URL) {
+	if d.filterExistsLocked(flt.URL) {
 		return false
 	}
 

internal/filtering/filter_test.go

@@ -17,8 +17,9 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-// serveFiltersLocally is a helper that concurrently listens on a free port
-// to respond with fltContent.
+// serveFiltersLocally is a helper that concurrently listens on a free port to
+// respond with fltContent.  It also gracefully closes the listener when the
+// test under t finishes.
 func serveFiltersLocally(t *testing.T, fltContent []byte) (ipp netip.AddrPort) {
 	t.Helper()
 

internal/filtering/filtering.go

@@ -366,7 +366,7 @@ func (d *DNSFilter) SetFilters(blockFilters, allowFilters []Filter, async bool)
 
 	err := d.initFiltering(allowFilters, blockFilters)
 	if err != nil {
-		log.Error("can't initialize filtering subsystem: %s", err)
+		log.Error("filtering: can't initialize filtering subsystem: %s", err)
 
 		return err
 	}