Fix truncation threshold

diff --git a/pdns/pdns_recursor.cc b/pdns/pdns_recursor.cc
index 181183087f4c9b06223ceb61cc3cd765c40e9f54..beaccd2f9ebdcc2e97a0eaf3502c2c0c79a1f765 100644 (file)
--- a/pdns/pdns_recursor.cc
+++ b/pdns/pdns_recursor.cc
@@ -889,6 +889,7 @@ static void startDoResolve(void *p)
       }
       ednsOpts = edo.d_options;
       haveEDNS=true;
+      maxanswersize -= 11; // EDNS header size
 
       for (const auto& o : edo.d_options) {
         if (o.first == EDNSOptionCode::ECS && g_useIncomingECS && !dc->d_ecsParsed) {

diff --git a/regression-tests.recursor-dnssec/test_LargeAnswer.py b/regression-tests.recursor-dnssec/test_LargeAnswer.py
index 866564ff66f7cd415a19aced50fa2053dc15a14e..6f078b15aa775a6835c073b84b68fafdeed89a7a 100644 (file)
--- a/regression-tests.recursor-dnssec/test_LargeAnswer.py
+++ b/regression-tests.recursor-dnssec/test_LargeAnswer.py
@@ -42,19 +42,23 @@ udp-truncation-threshold=%d
             cls._UDPResponder.start()
 
     def checkResponseContent(self, rawResponse, value):
-       self.assertEquals(len(rawResponse), self._udpTruncationThreshold)
-       response = dns.message.from_wire(rawResponse)
+        response = dns.message.from_wire(rawResponse)
 
-       self.assertRcodeEqual(response, dns.rcode.NOERROR)
-       self.assertFalse(response.flags & dns.flags.TC)
+        self.assertEquals(len(rawResponse), self._udpTruncationThreshold)
+        self.assertRcodeEqual(response, dns.rcode.NOERROR)
 
-       for record in response.answer:
-           self.assertEquals(record.rdtype, dns.rdatatype.TXT)
-           for part in record:
-               for string in part.strings:
-                   self.assertTrue(len(string) == 255 or len(string) == 16)
-                   for c in string:
-                       self.assertEquals(c, value)
+        self.assertMessageHasFlags(response, ['QR', 'RD', 'RA'])
+
+        for record in response.answer:
+            self.assertEquals(record.rdtype, dns.rdatatype.TXT)
+            for part in record:
+                for string in part.strings:
+                    self.assertTrue(len(string) == 255 or len(string) == 5)
+                    for c in string:
+                        self.assertEquals(c, value)
+
+    def checkTruncatedResponse(self, message):
+        self.assertMessageHasFlags(message, ['QR', 'RD', 'RA', 'TC'])
 
     def testLargeAnswer(self):
         # why the same query 10 times, do you ask? because if we are reading from
@@ -70,6 +74,20 @@ udp-truncation-threshold=%d
             raw = self.sendUDPQuery(query, decode=False)
             self.checkResponseContent(raw, 'Z')
 
+    def testLargeAnswerTruncate(self):
+        """
+        Check that we get a TC answer
+        """
+        query = dns.message.make_query('BBBB.large-answer.example.', 'TXT', 'IN', use_edns=True, payload=4096)
+        for _ in range(10):
+            response = self.sendUDPQuery(query)
+            self.checkTruncatedResponse(response)
+
+        query = dns.message.make_query('CCCC.large-answer.example.', 'TXT', 'IN', use_edns=True, payload=4096)
+        for _ in range(10):
+            response = self.sendUDPQuery(query)
+            self.checkTruncatedResponse(response)
+
 class UDPLargeResponder(DatagramProtocol):
 
     def datagramReceived(self, datagram, address):
@@ -81,12 +99,20 @@ class UDPLargeResponder(DatagramProtocol):
 
         if request.question[0].name == dns.name.from_text('AAAA.large-answer.example.'):
             value = 'A'
-        else:
+            final_count = 5
+        elif request.question[0].name == dns.name.from_text('ZZZZ.large-answer.example.'):
             value = 'Z'
+            final_count = 5
+        elif request.question[0].name == dns.name.from_text('BBBB.large-answer.example.'):
+            value = 'B'
+            final_count = 6
+        elif request.question[0].name == dns.name.from_text('CCCC.large-answer.example.'):
+            value = 'C'
+            final_count = 6
 
         answer = dns.rrset.from_text(request.question[0].name, 0, dns.rdataclass.IN, 'TXT', value*255)
         for _ in range(6):
             response.answer.append(answer)
-        answer = dns.rrset.from_text(request.question[0].name, 0, dns.rdataclass.IN, 'TXT', value*16)
+        answer = dns.rrset.from_text(request.question[0].name, 0, dns.rdataclass.IN, 'TXT', value*final_count)
         response.answer.append(answer)
         self.transport.write(response.to_wire(max_size=65535), address)