Add DNS record RDATA validation

src/DNS/Message.php

@@ -278,6 +278,22 @@ public function encode(?int $maxSize = null): string
         return $header->encode() . substr($packet, Header::LENGTH);
     }
 
+    /**
+     * Validate all response records without encoding the message.
+     */
+    public function validate(): void
+    {
+        foreach ([
+            $this->answers,
+            $this->authority,
+            $this->additional,
+        ] as $records) {
+            foreach ($records as $record) {
+                $record->validateRdata();
+            }
+        }
+    }
+
     /**
      * @param list<Record> $records
      */

src/DNS/Message/Record.php

@@ -386,6 +386,14 @@ public function encode(string $packet = ''): string
         return $data;
     }
 
+    /**
+     * Validate RDATA for this record type without encoding the full record.
+     */
+    public function validateRdata(): void
+    {
+        $this->encodeRdata('');
+    }
+
     /**
      * Encode RDATA based on record type.
      */

tests/unit/DNS/Message/RecordTest.php

@@ -513,6 +513,37 @@ class: Record::CLASS_IN,
         $this->assertSame(600, $decoded->ttl);
     }
 
+    public function testValidateRdataRejectsHostnameForARecord(): void
+    {
+        $record = new Record(
+            name: 'example.com',
+            type: Record::TYPE_A,
+            class: Record::CLASS_IN,
+            ttl: 300,
+            rdata: 'ns2.appwrite.zone'
+        );
+
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid IPv4 address: ns2.appwrite.zone');
+
+        $record->validateRdata();
+    }
+
+    public function testValidateRdataAcceptsHostnameForNsRecord(): void
+    {
+        $record = new Record(
+            name: 'example.com',
+            type: Record::TYPE_NS,
+            class: Record::CLASS_IN,
+            ttl: 300,
+            rdata: 'ns2.appwrite.zone'
+        );
+
+        $record->validateRdata();
+
+        $this->addToAssertionCount(1);
+    }
+
     public function testConstructorTrimsWhitespaceFromName(): void
     {
         $record = new Record(

tests/unit/DNS/MessageTest.php

@@ -2,6 +2,7 @@
 
 namespace Tests\Unit\Utopia\DNS;
 
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 use Utopia\DNS\Exception\Message\DecodingException;
 use Utopia\DNS\Exception\Message\PartialDecodingException;
@@ -726,6 +727,46 @@ public function testExtremeAnswerTruncationPreservesAuthoritativeFlag(): void
         );
     }
 
+    #[DataProvider('invalidSectionProvider')]
+    public function testValidateChecksAnswerAuthorityAndAdditionalRecords(string $invalidSection): void
+    {
+        $question = new Question('example.com', Record::TYPE_A);
+        $query = Message::query($question, id: 0x5508);
+
+        $invalid = [
+            new Record('ns2.appwrite.zone', Record::TYPE_A, Record::CLASS_IN, 300, 'ns2.appwrite.zone'),
+        ];
+        $valid = [
+            new Record('example.com', Record::TYPE_NS, Record::CLASS_IN, 300, 'ns2.appwrite.zone'),
+        ];
+
+        $response = Message::response(
+            $query->header,
+            Message::RCODE_NOERROR,
+            questions: $query->questions,
+            answers: $invalidSection === 'answers' ? $invalid : $valid,
+            authority: $invalidSection === 'authority' ? $invalid : $valid,
+            additional: $invalidSection === 'additional' ? $invalid : $valid
+        );
+
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid IPv4 address: ns2.appwrite.zone');
+
+        $response->validate();
+    }
+
+    /**
+     * @return array<string, array<int, string>>
+     */
+    public static function invalidSectionProvider(): array
+    {
+        return [
+            'answers' => ['answers'],
+            'authority' => ['authority'],
+            'additional' => ['additional'],
+        ];
+    }
+
     /**
      * NODATA-style response: zero answers but populated authority. When the
      * authority section can't fit, it's dropped without setting TC — there