TCP: pass data after a ZeroWindowProbe to subdissectors

If the single byte within a ZeroWindowProbe triggers reassembly within a
subdissector, a new MSP will be created with just a single byte. Be sure
not to mark subsequent segments that contain the full segment data as
retransmission as this prevents the subdissector from seeing the data.

Bug: 15427
Change-Id: I36ae2622689c6606c99cdff70b6beba4b9d25ca7
Reviewed-on: https://code.wireshark.org/review/31732
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Jasper Bongertz <jasper@packet-foo.com>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

2 files changed, 25 insertions, 0 deletions

diff --git a/test/captures/retrans-tls.pcap b/test/captures/retrans-tls.pcap
new file mode 100644
index 0000000000..90be0de74b
--- /dev/null
+++ b/test/captures/retrans-tls.pcap
diff --git a/test/suite_dissection.py b/test/suite_dissection.py
index 9af19ec2cd..9a62e933cc 100644
--- a/test/suite_dissection.py
+++ b/test/suite_dissection.py
@@ -121,3 +121,28 @@ class case_dissect_tcp(subprocesstest.SubprocessTestCase):
         # H - second retransmission.
         self.assertIn('7\t\t', lines[6])
         self.assertNotIn('[TCP segment of a reassembled PDU]', lines[6])
+
+    def test_tcp_reassembly_more_data_1(self, cmd_tshark, capture_file):
+        '''
+        Tests that reassembly also works when a new packet begins at the same
+        sequence number as the initial segment. This models behavior with the
+        ZeroWindowProbe: the initial segment contains a single byte. The second
+        segment contains that byte, plus the remainder.
+        '''
+        proc = self.assertRun((cmd_tshark,
+            '-r', capture_file('retrans-tls.pcap'),
+            '-Ytls', '-Tfields', '-eframe.number', '-etls.record.length',))
+        output = proc.stdout_str.replace('\r', '')
+        # First pass dissection actually accepted the first frame as TLS, but
+        # subsequently requested reassembly.
+        self.assertEqual(output, '1\t\n2\t16\n')
+
+    def test_tcp_reassembly_more_data_2(self, cmd_tshark, capture_file):
+        '''
+        Like test_tcp_reassembly_more_data_1, but checks the second pass (-2).
+        '''
+        proc = self.assertRun((cmd_tshark,
+            '-r', capture_file('retrans-tls.pcap'),
+            '-Ytls', '-Tfields', '-eframe.number', '-etls.record.length', '-2'))
+        output = proc.stdout_str.replace('\r', '')
+        self.assertEqual(output, '2\t16\n')