From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Thu, 14 Dec 2017 10:14:35 +0000 (+0100)
Subject: rec: Add regression tests for UDP outgoing buffer size
X-Git-Tag: dnsdist-1.3.0~178^2~1
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fb611f07566e08adf31c374e6453a6494df7d696;p=pdns

rec: Add regression tests for UDP outgoing buffer size
---

diff --git a/regression-tests.recursor-dnssec/recursortests.py b/regression-tests.recursor-dnssec/recursortests.py
index a33c25966..720477ed2 100644
--- a/regression-tests.recursor-dnssec/recursortests.py
+++ b/regression-tests.recursor-dnssec/recursortests.py
@@ -575,7 +575,7 @@ distributor-threads=1""".format(confdir=confdir,
                 raise
 
     @classmethod
-    def sendUDPQuery(cls, query, timeout=2.0, fwparams=dict()):
+    def sendUDPQuery(cls, query, timeout=2.0, decode=True, fwparams=dict()):
         if timeout:
             cls._sock.settimeout(timeout)
 
@@ -590,6 +590,8 @@ distributor-threads=1""".format(confdir=confdir,
 
         message = None
         if data:
+            if not decode:
+                return data
             message = dns.message.from_wire(data, **fwparams)
         return message
 
diff --git a/regression-tests.recursor-dnssec/test_LargeAnswer.py b/regression-tests.recursor-dnssec/test_LargeAnswer.py
new file mode 100644
index 000000000..c8300dc28
--- /dev/null
+++ b/regression-tests.recursor-dnssec/test_LargeAnswer.py
@@ -0,0 +1,110 @@
+import dns
+import os
+import socket
+import struct
+import threading
+import time
+
+from recursortests import RecursorTest
+from twisted.internet.protocol import DatagramProtocol
+from twisted.internet import reactor
+
+largeReactorRunning = False
+
+class LargeAnswerTest(RecursorTest):
+    """
+    This test makes sure that we correctly process an answer matching our exact
+    udp-truncation-threshold buffer size.
+    """
+    _confdir = 'LargeAnswer'
+    _udpTruncationThreshold = 1680
+
+    _config_template = """
+forward-zones=large-answer.example=%s.22
+udp-truncation-threshold=%d
+    """ % (os.environ['PREFIX'], _udpTruncationThreshold)
+
+    @classmethod
+    def startResponders(cls):
+        global largeReactorRunning
+        print("Launching responders..")
+
+        address = cls._PREFIX + '.22'
+        port = 53
+
+        if not largeReactorRunning:
+            reactor.listenUDP(port, UDPLargeResponder(), interface=address)
+            largeReactorRunning = True
+
+        if not reactor.running:
+            cls._UDPResponder = threading.Thread(name='UDP Large Responder', target=reactor.run, args=(False,))
+            cls._UDPResponder.setDaemon(True)
+            cls._UDPResponder.start()
+
+    @classmethod
+    def setUpClass(cls):
+        cls.setUpSockets()
+
+        cls.startResponders()
+
+        confdir = os.path.join('configs', cls._confdir)
+        cls.createConfigDir(confdir)
+
+        cls.generateRecursorConfig(confdir)
+        cls.startRecursor(confdir, cls._recursorPort)
+
+        print("Launching tests..")
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.tearDownRecursor()
+
+    def checkResponseContent(self, rawResponse, value):
+       self.assertEquals(len(rawResponse), self._udpTruncationThreshold)
+       response = dns.message.from_wire(rawResponse)
+
+       self.assertRcodeEqual(response, dns.rcode.NOERROR)
+       self.assertFalse(response.flags & dns.flags.TC)
+
+       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)
+
+    def testLargeAnswer(self):
+        # why the same query 10 times, do you ask? because if we are reading from
+        # unintialized buffer memory, there is small risk that we find exactly the
+        # value we expected by chance so let's  massage our buffer a bit
+        query = dns.message.make_query('AAAA.large-answer.example.', 'TXT', 'IN', use_edns=True, payload=4096)
+        for _ in range(10):
+            raw = self.sendUDPQuery(query, decode=False)
+            self.checkResponseContent(raw, 'A')
+
+        query = dns.message.make_query('ZZZZ.large-answer.example.', 'TXT', 'IN', use_edns=True, payload=4096)
+        for _ in range(10):
+            raw = self.sendUDPQuery(query, decode=False)
+            self.checkResponseContent(raw, 'Z')
+
+class UDPLargeResponder(DatagramProtocol):
+
+    def datagramReceived(self, datagram, address):
+        request = dns.message.from_wire(datagram)
+
+        response = dns.message.make_response(request)
+        response.use_edns(edns=False)
+        response.flags |= dns.flags.AA
+
+        if request.question[0].name == dns.name.from_text('AAAA.large-answer.example.'):
+            value = 'A'
+        else:
+            value = 'Z'
+
+        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)
+        response.answer.append(answer)
+        self.transport.write(response.to_wire(max_size=65535), address)