improve LookupNetIP performance

client_resolver.go

@@ -39,20 +39,21 @@ func (c *Client) AppendLookupNetIP(dst []netip.Addr, ctx context.Context, networ
 		return nil, err
 	}
 
-	cname := make([]byte, 0, 64)
+	var cname []byte
 	for r := range resp.Records {
 		switch r.Type {
 		case TypeCNAME:
-			cname = resp.DecodeName(cname[:0], r.Data)
+			cname = r.Data
 		case TypeA:
 			dst = append(dst, netip.AddrFrom4(*(*[4]byte)(r.Data)))
 		case TypeAAAA:
 			dst = append(dst, netip.AddrFrom16(*(*[16]byte)(r.Data)))
 		}
 	}
 
-	if len(cname) != 0 && len(dst) == 0 {
-		dst, err = c.AppendLookupNetIP(dst, ctx, network, b2s(cname))
+	if cname != nil && len(dst) == 0 {
+		b := resp.DecodeName(make([]byte, 0, 64), cname)
+		dst, err = c.AppendLookupNetIP(dst, ctx, network, b2s(b))
 	}
 
 	return dst, err

client_test.go

@@ -157,6 +157,21 @@ func TestClientLookup(t *testing.T) {
 	}
 }
 
+func TestClientLookupNetIP(t *testing.T) {
+	host := "ip.phus.lu"
+
+	client := &Client{
+		Addr:    "1.1.1.1:53",
+		Timeout: 1 * time.Second,
+	}
+
+	ips, err := client.LookupNetIP(context.Background(), "ip", host)
+	if err != nil {
+		t.Errorf("dns_server=%+v LookupNetIP(%#v) error: %+v\n", client.Addr, host, err)
+	}
+	t.Logf("dns_server=%+v LookupNetIP(%#v) return %+v", client.Addr, host, ips)
+}
+
 func BenchmarkResolverPureGo(b *testing.B) {
 	resolver := net.Resolver{PreferGo: true}