Fix codec-dns tests

chrisvest · chrisvest · commit 943edb361423 · 2026-05-04T13:29:43.000-07:00
diff --git a/codec-dns/src/main/java/io/netty/handler/codec/dns/DnsCodecUtil.java b/codec-dns/src/main/java/io/netty/handler/codec/dns/DnsCodecUtil.java
@@ -38,10 +38,16 @@ static void encodeDomainName(String name, ByteBuf buf) {
 
         int totalLength = 0;
         final String[] labels = name.split("\\.");
-        for (String label : labels) {
+        for (int i = 0; i < labels.length; i++) {
+            String label = labels[i];
             final int labelLen = label.length();
             if (labelLen == 0) {
-                throw new IllegalArgumentException("DNS name contains empty label: " + name);
+                if (i == labels.length - 1) {
+                    // zero-length label at the end means the end of the name.
+                    break;
+                } else {
+                    throw new IllegalArgumentException("DNS name contains empty label: " + name);
+                }
             }
             if (labelLen > 63) {
                 throw new IllegalArgumentException(
diff --git a/codec-dns/src/test/java/io/netty/handler/codec/dns/DnsCodecUtilTest.java b/codec-dns/src/test/java/io/netty/handler/codec/dns/DnsCodecUtilTest.java
@@ -61,6 +61,18 @@ void rejectTooLongLabelWhileEncoding() {
         buf.release();
     }
 
+    @Test
+    void rejectEmptyLabelWhileEncoding() {
+        ByteBuf buf = Unpooled.buffer(256);
+        // 63 is the maximum label length
+        StringBuilder sb = new StringBuilder();
+        appendLabel(sb, 5);
+        appendLabel(sb, 0);
+        appendLabel(sb, 5);
+        assertThrows(IllegalArgumentException.class, () -> DnsCodecUtil.encodeDomainName(sb.toString(), buf));
+        buf.release();
+    }
+
     @Test
     void rejectTooLongDomainNameWhileEncoding() {
         ByteBuf buf = Unpooled.buffer(256);
