text: #!/usr/bin/env python
  """IP4 and IP6 MTU functional tests"""
  
  #
  # Add tests for:
  # - sub interfaces
  # - Verify that adjacencies inherit MTU correctly
  # - Verify that sub-interfaces inherit MTU correctly
  # - Different types of interfaces?
  #
  import unittest
  from scapy.layers.inet6 import IPv6, Ether, IP, UDP, ICMPv6PacketTooBig
  from scapy.layers.inet import ICMP
  from framework import VppTestCase, VppTestRunner
  from vpp_ip import DpoProto
  from vpp_ip_route import VppIpRoute, VppRoutePath, FibPathProto
  from socket import AF_INET, AF_INET6, inet_pton
  from util import reassemble4
  
  
  """ Test_mtu is a subclass of VPPTestCase classes.
      MTU tests.
  """
  
  
  class TestMTU(VppTestCase):
      """ MTU Test Case """
      maxDiff = None
  
      @classmethod
      def setUpClass(cls):
          super(TestMTU, cls).setUpClass()
          cls.create_pg_interfaces(range(2))
          cls.interfaces = list(cls.pg_interfaces)
  
      @classmethod
      def tearDownClass(cls):
          super(TestMTU, cls).tearDownClass()
  
      def setUp(self):
          super(TestMTU, self).setUp()
          for i in self.interfaces:
              i.admin_up()
              i.config_ip4()
              i.config_ip6()
              i.disable_ipv6_ra()
              i.resolve_arp()
              i.resolve_ndp()
  
      def tearDown(self):
          super(TestMTU, self).tearDown()
          if not self.vpp_dead:
              for i in self.pg_interfaces:
                  i.unconfig_ip4()
                  i.unconfig_ip6()
                  i.admin_down()
  
      def validate(self, rx, expected):
          self.assertEqual(rx, expected.__class__(expected))
  
      def validate_bytes(self, rx, expected):
          self.assertEqual(rx, expected)
  
      def payload(self, len):
          return 'x' * len
  
      def get_mtu(self, sw_if_index):
          rv = self.vapi.sw_interface_dump(sw_if_index=sw_if_index)
          for i in rv:
              if i.sw_if_index == sw_if_index:
                  return i.mtu[0]
          return 0
  
      def test_ip4_mtu(self):
          """ IP4 MTU test """
  
          p_ether = Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac)
          p_ip4 = IP(src=self.pg0.remote_ip4, dst=self.pg1.remote_ip4,
                     flags='DF')
  
          current_mtu = self.get_mtu(self.pg1.sw_if_index)
  
          p_payload = UDP(sport=1234, dport=1234) / self.payload(
              current_mtu - 20 - 8)
  
          p4 = p_ether / p_ip4 / p_payload
          p4_reply = p_ip4 / p_payload
          p4_reply.ttl -= 1
          rx = self.send_and_expect(self.pg0, p4*11, self.pg1)
          for p in rx:
              self.validate(p[1], p4_reply)
  
          # MTU
          self.vapi.sw_interface_set_mtu(self.pg1.sw_if_index, [576, 0, 0, 0])
          self.assertEqual(576, self.get_mtu(self.pg1.sw_if_index))
  
          # Should fail. Too large MTU
          p_icmp4 = ICMP(type='dest-unreach', code='fragmentation-needed',
                         nexthopmtu=576, chksum=0x2dbb)
          icmp4_reply = (IP(src=self.pg0.local_ip4,
                            dst=self.pg0.remote_ip4,
                            ttl=254, len=576, id=0) /
                         p_icmp4 / p_ip4 / p_payload)
          icmp4_reply[1].ttl -= 1
          n = icmp4_reply.__class__(icmp4_reply)
          s = bytes(icmp4_reply)
          icmp4_reply = s[0:576]
          rx = self.send_and_expect(self.pg0, p4*11, self.pg0)
          for p in rx:
              # p.show2()
              # n.show2()
              self.validate_bytes(bytes(p[1]), icmp4_reply)
  
          # Now with DF off. Expect fragments.
          # First go with 1500 byte packets.
          p_payload = UDP(sport=1234, dport=1234) / self.payload(
              1500 - 20 - 8)
          p4 = p_ether / p_ip4 / p_payload
          p4.flags = 0
          p4_reply = p_ip4 / p_payload
          p4_reply.ttl = 62  # check this
          p4_reply.flags = 0
          p4_reply.id = 256
          self.pg_enable_capture()
          self.pg0.add_stream(p4*1)
          self.pg_start()
          rx = self.pg1.get_capture(3)
          reass_pkt = reassemble4(rx)
          self.validate(reass_pkt, p4_reply)
  
          '''
          # Now what happens with a 9K frame
          p_payload = UDP(sport=1234, dport=1234) / self.payload(
              current_mtu - 20 - 8)
          p4 = p_ether / p_ip4 / p_payload
          p4.flags = 0
          p4_reply = p_ip4 / p_payload
          p4_reply.ttl = 62 # check this
          p4_reply.flags = 0
          p4_reply.id = 512
  
          self.pg_enable_capture()
          self.pg0.add_stream(p4*1)
          self.pg_start()
          rx = self.pg1.get_capture(16)
          reass_pkt = reassemble4(rx)
          reass_pkt.show2()
          p4_reply.show2()
          self.validate(reass_pkt, p4_reply)
          '''
  
          # Reset MTU
          self.vapi.sw_interface_set_mtu(self.pg1.sw_if_index,
                                         [current_mtu, 0, 0, 0])
  
      def test_ip6_mtu(self):
          """ IP6 MTU test """
  
          current_mtu = self.get_mtu(self.pg1.sw_if_index)
  
          p_ether = Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac)
          p_ip6 = IPv6(src=self.pg0.remote_ip6, dst=self.pg1.remote_ip6)
  
          p_payload = UDP(sport=1234, dport=1234) / self.payload(
              current_mtu - 40 - 8)
  
          p6 = p_ether / p_ip6 / p_payload
          p6_reply = p_ip6 / p_payload
          p6_reply.hlim -= 1
          rx = self.send_and_expect(self.pg0, p6*9, self.pg1)
          for p in rx:
              self.validate(p[1], p6_reply)
  
          # MTU (only checked on encap)
          self.vapi.sw_interface_set_mtu(self.pg1.sw_if_index, [1280, 0, 0, 0])
          self.assertEqual(1280, self.get_mtu(self.pg1.sw_if_index))
  
          # Should fail. Too large MTU
          p_icmp6 = ICMPv6PacketTooBig(mtu=1280, cksum=0x4c7a)
          icmp6_reply = (IPv6(src=self.pg0.local_ip6,
                              dst=self.pg0.remote_ip6,
                              hlim=255, plen=1240) /
                         p_icmp6 / p_ip6 / p_payload)
          icmp6_reply[2].hlim -= 1
          n = icmp6_reply.__class__(icmp6_reply)
          s = bytes(icmp6_reply)
          icmp6_reply_str = s[0:1280]
  
          rx = self.send_and_expect(self.pg0, p6*9, self.pg0)
          for p in rx:
              self.validate_bytes(bytes(p[1]), icmp6_reply_str)
  
          # Reset MTU
          self.vapi.sw_interface_set_mtu(self.pg1.sw_if_index,
                                         [current_mtu, 0, 0, 0])
  
  
  if __name__ == '__main__':
      unittest.main(testRunner=VppTestRunner)
  