Ignore empty hostnames

Author: rtpt-erikgeiser

filter.go

@@ -425,7 +425,7 @@ func asSRVMatchers(matcherStrings []string) (srvMatchers, error) {
 				return nil, fmt.Errorf("parse port %q in service %q", portStr, m)
 			}
 
-			matchers = append(matchers, &srvMatcher{Service: strings.ToLower(service), Port: uint16(port)}) //nolint:gosec
+			matchers = append(matchers, &srvMatcher{Service: strings.ToLower(service), Port: uint16(port)})
 		default:
 			return nil, fmt.Errorf("SRV matcher contains more than one colon: %q", m)
 		}

hostinfo/host_info.go

@@ -163,11 +163,7 @@ func (c *Cache) toIPv4(ip net.IP) net.IP {
 		return ipv4
 	}
 
-	if ipv4 == nil {
-		return c.lookupUsingExternalHostnames(ip, mac)
-	}
-
-	return ipv4
+	return c.lookupUsingExternalHostnames(ip, mac)
 }
 
 func (c *Cache) lookupUsingExternalHostnames(ip net.IP, mac net.HardwareAddr) net.IP {
@@ -315,6 +311,10 @@ func appendUnique(oldElements []string, newElements ...string) []string {
 	}
 
 	for _, el := range newElements {
+		if strings.TrimSpace(el) == "" {
+			continue
+		}
+
 		el := strings.TrimRight(el, ".")
 
 		_, ok := present[el]

hostinfo/host_info_test.go

@@ -47,6 +47,16 @@ func TestCacheHostInfos(t *testing.T) {
 		"192.168.56.100", "test")
 }
 
+func TestAddHostnamesIgnoreEmpty(t *testing.T) {
+	c := NewCache()
+
+	ipv4 := mustParseIP(t, "192.168.56.101")
+
+	c.AddHostnamesForIP(ipv4, []string{"foo", "", "bar", " "})
+
+	assertContainsExactly(t, c.HostInfos(ipv4), "foo", "bar")
+}
+
 func TestCacheSaveMACFromIP(t *testing.T) {
 	c := NewCache()