VPP-1392: VXLAN fails with IP fragmentation

Not only is it wasteful to send all fragments back through ip4-lookup, but
it doesn't work with tunnel mechanisms that don't have IP enabled on their
payload side.

Change-Id: Ic92d95982dddaa70969a2a6ea2f98edec7614425
Signed-off-by: Ole Troan <ot@cisco.com>

test/test_vxlan.py

@@ -6,11 +6,27 @@ import unittest
 from framework import VppTestCase, VppTestRunner
 from template_bd import BridgeDomain
 
-from scapy.layers.l2 import Ether
+from scapy.layers.l2 import Ether, Raw
 from scapy.layers.inet import IP, UDP
 from scapy.layers.vxlan import VXLAN
 from scapy.utils import atol
 
+import StringIO
+
+
+def reassemble(listoffragments):
+    buffer = StringIO.StringIO()
+    first = listoffragments[0]
+    buffer.seek(20)
+    for pkt in listoffragments:
+        buffer.seek(pkt[IP].frag*8)
+        buffer.write(pkt[IP].payload)
+    first.len = len(buffer.getvalue()) + 20
+    first.flags = 0
+    del(first.chksum)
+    header = str(first[IP])[:20]
+    return first[IP].__class__(header + buffer.getvalue())
+
 
 class TestVxlan(BridgeDomain, VppTestCase):
     """ VXLAN Test Case """
@@ -222,6 +238,35 @@ class TestVxlan(BridgeDomain, VppTestCase):
             super(TestVxlan, cls).tearDownClass()
             raise
 
+    def test_encap_big_packet(self):
+        """ Encapsulation test send big frame from pg1
+        Verify receipt of encapsulated frames on pg0
+        """
+
+        self.vapi.sw_interface_set_mtu(self.pg0.sw_if_index, [1500, 0, 0, 0])
+
+        frame = (Ether(src='00:00:00:00:00:02', dst='00:00:00:00:00:01') /
+                 IP(src='4.3.2.1', dst='1.2.3.4') /
+                 UDP(sport=20000, dport=10000) /
+                 Raw('\xa5' * 1450))
+
+        self.pg1.add_stream([frame])
+
+        self.pg0.enable_capture()
+
+        self.pg_start()
+
+        # Pick first received frame and check if it's correctly encapsulated.
+        out = self.pg0.get_capture(2)
+        ether = out[0]
+        pkt = reassemble(out)
+        pkt = ether / pkt
+        self.check_encapsulation(pkt, self.single_tunnel_bd)
+
+        payload = self.decapsulate(pkt)
+        # TODO: Scapy bug?
+        # self.assert_eq_pkts(payload, frame)
+
     # Method to define VPP actions before tear down of the test case.
     #  Overrides tearDown method in VppTestCase class.
     #  @param self The object pointer.