text: import os
  import socket
  from socket import inet_pton, inet_ntop
  import struct
  import time
  from traceback import format_exc, format_stack
  
  import scapy.compat
  from scapy.utils import wrpcap, rdpcap, PcapReader
  from scapy.plist import PacketList
  from vpp_interface import VppInterface
  from vpp_papi import VppEnum
  
  from scapy.layers.l2 import Ether, ARP
  from scapy.layers.inet6 import IPv6, ICMPv6ND_NS, ICMPv6ND_NA,\
      ICMPv6NDOptSrcLLAddr, ICMPv6NDOptDstLLAddr, ICMPv6ND_RA, RouterAlert, \
      IPv6ExtHdrHopByHop
  from util import ppp, ppc
  from scapy.utils6 import in6_getnsma, in6_getnsmac, in6_ismaddr
  
  
  class CaptureTimeoutError(Exception):
      """ Exception raised if capture or packet doesn't appear within timeout """
      pass
  
  
  def is_ipv6_misc(p):
      """ Is packet one of uninteresting IPv6 broadcasts? """
      if p.haslayer(ICMPv6ND_RA):
          if in6_ismaddr(p[IPv6].dst):
              return True
      if p.haslayer(IPv6ExtHdrHopByHop):
          for o in p[IPv6ExtHdrHopByHop].options:
              if isinstance(o, RouterAlert):
                  return True
      return False
  
  
  class VppPGInterface(VppInterface):
      """
      VPP packet-generator interface
      """
  
      @property
      def pg_index(self):
          """packet-generator interface index assigned by VPP"""
          return self._pg_index
  
      @property
      def gso_enabled(self):
          """gso enabled on packet-generator interface"""
          if self._gso_enabled == 0:
              return "gso-disabled"
          return "gso-enabled"
  
      @property
      def gso_size(self):
          """gso size on packet-generator interface"""
          return self._gso_size
  
      @property
      def coalesce_is_enabled(self):
          """coalesce enabled on packet-generator interface"""
          if self._coalesce_enabled == 0:
              return "coalesce-disabled"
          return "coalesce-enabled"
  
      @property
      def out_path(self):
          """pcap file path - captured packets"""
          return self._out_path
  
      def get_in_path(self, worker):
          """ pcap file path - injected packets"""
          if worker is not None:
              return "%s/pg%u_wrk%u_in.pcap" % (self.test.tempdir, self.pg_index,
                                                worker)
          return "%s/pg%u_in.pcap" % (self.test.tempdir, self.pg_index)
  
      @property
      def capture_cli(self):
          """CLI string to start capture on this interface"""
          return self._capture_cli
  
      def get_cap_name(self, worker=None):
          """return capture name for this interface and given worker"""
          if worker is not None:
              return self._cap_name + "-worker%d" % worker
          return self._cap_name
  
      def get_input_cli(self, nb_replays=None, worker=None):
          """return CLI string to load the injected packets"""
          input_cli = "packet-generator new pcap %s source pg%u name %s" % (
              self.get_in_path(worker), self.pg_index, self.get_cap_name(worker))
          if nb_replays is not None:
              return "%s limit %d" % (input_cli, nb_replays)
          if worker is not None:
              return "%s worker %d" % (input_cli, worker)
          return input_cli
  
      @property
      def in_history_counter(self):
          """Self-incrementing counter used when renaming old pcap files"""
          v = self._in_history_counter
          self._in_history_counter += 1
          return v
  
      @property
      def out_history_counter(self):
          """Self-incrementing counter used when renaming old pcap files"""
          v = self._out_history_counter
          self._out_history_counter += 1
          return v
  
      def __init__(self, test, pg_index, gso, gso_size, mode):
          """ Create VPP packet-generator interface """
          super().__init__(test)
  
          r = test.vapi.pg_create_interface_v2(pg_index, gso, gso_size, mode)
          self.set_sw_if_index(r.sw_if_index)
  
          self._in_history_counter = 0
          self._out_history_counter = 0
          self._out_assert_counter = 0
          self._pg_index = pg_index
          self._gso_enabled = gso
          self._gso_size = gso_size
          self._coalesce_enabled = 0
          self._out_file = "pg%u_out.pcap" % self.pg_index
          self._out_path = self.test.tempdir + "/" + self._out_file
          self._capture_cli = "packet-generator capture pg%u pcap %s" % (
              self.pg_index, self.out_path)
          self._cap_name = "pcap%u-sw_if_index-%s" % (
              self.pg_index, self.sw_if_index)
  
      def rename_old_pcap_file(self, path, counter):
          filename = os.path.basename(path)
          try:
              if os.path.isfile(path):
                  name = "%s/history.[timestamp:%f].[%s-counter:%04d].%s" % \
                      (self.test.tempdir,
                       time.time(),
                       self.name,
                       counter,
                       filename)
                  self.test.logger.debug("Renaming %s->%s" %
                                         (path, name))
                  os.rename(path, name)
          except OSError:
              self.test.logger.debug("OSError: Could not rename %s %s" %
                                     (path, filename))
  
      def enable_capture(self):
          """ Enable capture on this packet-generator interface
              of at most n packets.
              If n < 0, this is no limit
          """
          # disable the capture to flush the capture
          self.disable_capture()
          self.rename_old_pcap_file(self.out_path, self.out_history_counter)
          # FIXME this should be an API, but no such exists atm
          self.test.vapi.cli(self.capture_cli)
          self._pcap_reader = None
  
      def disable_capture(self):
          self.test.vapi.cli("%s disable" % self.capture_cli)
  
      def coalesce_enable(self):
          """ Enable packet coalesce on this packet-generator interface"""
          self._coalesce_enabled = 1
          self.test.vapi.pg_interface_enable_disable_coalesce(self.sw_if_index,
                                                              1)
  
      def coalesce_disable(self):
          """ Disable packet coalesce on this packet-generator interface"""
          self._coalesce_enabled = 0
          self.test.vapi.pg_interface_enable_disable_coalesce(self.sw_if_index,
                                                              0)
  
      def add_stream(self, pkts, nb_replays=None, worker=None):
          """
          Add a stream of packets to this packet-generator
  
          :param pkts: iterable packets
  
          """
          wrpcap(self.get_in_path(worker), pkts)
          self.test.register_pcap(self, worker)
          # FIXME this should be an API, but no such exists atm
          self.test.vapi.cli(self.get_input_cli(nb_replays, worker))
  
      def generate_debug_aid(self, kind):
          """ Create a hardlink to the out file with a counter and a file
          containing stack trace to ease debugging in case of multiple capture
          files present. """
          self.test.logger.debug("Generating debug aid for %s on %s" %
                                 (kind, self._name))
          link_path, stack_path = ["%s/debug_%s_%s_%s.%s" %
                                   (self.test.tempdir, self._name,
                                    self._out_assert_counter, kind, suffix)
                                   for suffix in ["pcap", "stack"]
                                   ]
          os.link(self.out_path, link_path)
          with open(stack_path, "w") as f:
              f.writelines(format_stack())
          self._out_assert_counter += 1
  
      def _get_capture(self, timeout, filter_out_fn=is_ipv6_misc):
          """ Helper method to get capture and filter it """
          try:
              if not self.wait_for_capture_file(timeout):
                  return None
              output = rdpcap(self.out_path)
              self.test.logger.debug("Capture has %s packets" % len(output.res))
          except:
              self.test.logger.debug("Exception in scapy.rdpcap (%s): %s" %
                                     (self.out_path, format_exc()))
              return None
          before = len(output.res)
          if filter_out_fn:
              output.res = [p for p in output.res if not filter_out_fn(p)]
          removed = before - len(output.res)
          if removed:
              self.test.logger.debug(
                  "Filtered out %s packets from capture (returning %s)" %
                  (removed, len(output.res)))
          return output
  
      def get_capture(self, expected_count=None, remark=None, timeout=1,
                      filter_out_fn=is_ipv6_misc):
          """ Get captured packets
  
          :param expected_count: expected number of packets to capture, if None,
                                 then self.test.packet_count_for_dst_pg_idx is
                                 used to lookup the expected count
          :param remark: remark printed into debug logs
          :param timeout: how long to wait for packets
          :param filter_out_fn: filter applied to each packet, packets for which
                                the filter returns True are removed from capture
          :returns: iterable packets
          """
          remaining_time = timeout
          capture = None
          name = self.name if remark is None else "%s (%s)" % (self.name, remark)
          based_on = "based on provided argument"
          if expected_count is None:
              expected_count = \
                  self.test.get_packet_count_for_if_idx(self.sw_if_index)
              based_on = "based on stored packet_infos"
              if expected_count == 0:
                  raise Exception(
                      "Internal error, expected packet count for %s is 0!" %
                      name)
          self.test.logger.debug("Expecting to capture %s (%s) packets on %s" % (
              expected_count, based_on, name))
          while remaining_time > 0:
              before = time.time()
              capture = self._get_capture(remaining_time, filter_out_fn)
              elapsed_time = time.time() - before
              if capture:
                  if len(capture.res) == expected_count:
                      # bingo, got the packets we expected
                      return capture
                  elif len(capture.res) > expected_count:
                      self.test.logger.error(
                          ppc("Unexpected packets captured:", capture))
                      break
                  else:
                      self.test.logger.debug("Partial capture containing %s "
                                             "packets doesn't match expected "
                                             "count %s (yet?)" %
                                             (len(capture.res), expected_count))
              elif expected_count == 0:
                  # bingo, got None as we expected - return empty capture
                  return PacketList()
              remaining_time -= elapsed_time
          if capture:
              self.generate_debug_aid("count-mismatch")
              raise Exception("Captured packets mismatch, captured %s packets, "
                              "expected %s packets on %s" %
                              (len(capture.res), expected_count, name))
          else:
              raise Exception("No packets captured on %s" % name)
  
      def assert_nothing_captured(self, remark=None, filter_out_fn=is_ipv6_misc):
          """ Assert that nothing unfiltered was captured on interface
  
          :param remark: remark printed into debug logs
          :param filter_out_fn: filter applied to each packet, packets for which
                                the filter returns True are removed from capture
          """
          if os.path.isfile(self.out_path):
              try:
                  capture = self.get_capture(
                      0, remark=remark, filter_out_fn=filter_out_fn)
                  if not capture or len(capture.res) == 0:
                      # junk filtered out, we're good
                      return
              except:
                  pass
              self.generate_debug_aid("empty-assert")
              if remark:
                  raise AssertionError(
                      "Non-empty capture file present for interface %s (%s)" %
                      (self.name, remark))
              else:
                  raise AssertionError("Capture file present for interface %s" %
                                       self.name)
  
      def wait_for_pg_stop(self):
          # wait till packet-generator is stopped
          # "show packet-generator" while it is still running gives this:
          # Name               Enabled        Count     Parameters
          # pcap0-sw_if_inde     Yes           64       limit 64, ...
          #
          # also have a 5-minute timeout just in case things go terribly wrong...
          deadline = time.time() + 300
          while self.test.vapi.cli('show packet-generator').find("Yes") != -1:
              self._test.sleep(0.01)  # yield
              if time.time() > deadline:
                  self.test.logger.debug("Timeout waiting for pg to stop")
                  break
  
      def wait_for_capture_file(self, timeout=1):
          """
          Wait until pcap capture file appears
  
          :param timeout: How long to wait for the packet (default 1s)
  
          :returns: True/False if the file is present or appears within timeout
          """
          self.wait_for_pg_stop()
          deadline = time.time() + timeout
          if not os.path.isfile(self.out_path):
              self.test.logger.debug("Waiting for capture file %s to appear, "
                                     "timeout is %ss" % (self.out_path, timeout))
          else:
              self.test.logger.debug("Capture file %s already exists" %
                                     self.out_path)
              return True
          while time.time() < deadline:
              if os.path.isfile(self.out_path):
                  break
              self._test.sleep(0)  # yield
          if os.path.isfile(self.out_path):
              self.test.logger.debug("Capture file appeared after %fs" %
                                     (time.time() - (deadline - timeout)))
          else:
              self.test.logger.debug("Timeout - capture file still nowhere")
              return False
          return True
  
      def verify_enough_packet_data_in_pcap(self):
          """
          Check if enough data is available in file handled by internal pcap
          reader so that a whole packet can be read.
  
          :returns: True if enough data present, else False
          """
          orig_pos = self._pcap_reader.f.tell()  # save file position
          enough_data = False
          # read packet header from pcap
          packet_header_size = 16
          caplen = None
          end_pos = None
          hdr = self._pcap_reader.f.read(packet_header_size)
          if len(hdr) == packet_header_size:
              # parse the capture length - caplen
              sec, usec, caplen, wirelen = struct.unpack(
                  self._pcap_reader.endian + "IIII", hdr)
              self._pcap_reader.f.seek(0, 2)  # seek to end of file
              end_pos = self._pcap_reader.f.tell()  # get position at end
              if end_pos >= orig_pos + len(hdr) + caplen:
                  enough_data = True  # yay, we have enough data
          self._pcap_reader.f.seek(orig_pos, 0)  # restore original position
          return enough_data
  
      def wait_for_packet(self, timeout, filter_out_fn=is_ipv6_misc):
          """
          Wait for next packet captured with a timeout
  
          :param timeout: How long to wait for the packet
  
          :returns: Captured packet if no packet arrived within timeout
          :raises Exception: if no packet arrives within timeout
          """
          deadline = time.time() + timeout
          if self._pcap_reader is None:
              if not self.wait_for_capture_file(timeout):
                  raise CaptureTimeoutError("Capture file %s did not appear "
                                            "within timeout" % self.out_path)
              while time.time() < deadline:
                  try:
                      self._pcap_reader = PcapReader(self.out_path)
                      break
                  except:
                      self.test.logger.debug(
                          "Exception in scapy.PcapReader(%s): %s" %
                          (self.out_path, format_exc()))
          if not self._pcap_reader:
              raise CaptureTimeoutError("Capture file %s did not appear within "
                                        "timeout" % self.out_path)
  
          poll = False
          if timeout > 0:
              self.test.logger.debug("Waiting for packet")
          else:
              poll = True
              self.test.logger.debug("Polling for packet")
          while time.time() < deadline or poll:
              if not self.verify_enough_packet_data_in_pcap():
                  self._test.sleep(0)  # yield
                  poll = False
                  continue
              p = self._pcap_reader.recv()
              if p is not None:
                  if filter_out_fn is not None and filter_out_fn(p):
                      self.test.logger.debug(
                          "Packet received after %ss was filtered out" %
                          (time.time() - (deadline - timeout)))
                  else:
                      self.test.logger.debug(
                          "Packet received after %fs" %
                          (time.time() - (deadline - timeout)))
                      return p
              self._test.sleep(0)  # yield
              poll = False
          self.test.logger.debug("Timeout - no packets received")
          raise CaptureTimeoutError("Packet didn't arrive within timeout")
  
      def create_arp_req(self):
          """Create ARP request applicable for this interface"""
          return (Ether(dst="ff:ff:ff:ff:ff:ff", src=self.remote_mac) /
                  ARP(op=ARP.who_has, pdst=self.local_ip4,
                      psrc=self.remote_ip4, hwsrc=self.remote_mac))
  
      def create_ndp_req(self, addr=None):
          """Create NDP - NS applicable for this interface"""
          if not addr:
              addr = self.local_ip6
          nsma = in6_getnsma(inet_pton(socket.AF_INET6, addr))
          d = inet_ntop(socket.AF_INET6, nsma)
  
          return (Ether(dst=in6_getnsmac(nsma)) /
                  IPv6(dst=d, src=self.remote_ip6) /
                  ICMPv6ND_NS(tgt=addr) /
                  ICMPv6NDOptSrcLLAddr(lladdr=self.remote_mac))
  
      def resolve_arp(self, pg_interface=None):
          """Resolve ARP using provided packet-generator interface
  
          :param pg_interface: interface used to resolve, if None then this
              interface is used
  
          """
          if pg_interface is None:
              pg_interface = self
          self.test.logger.info("Sending ARP request for %s on port %s" %
                                (self.local_ip4, pg_interface.name))
          arp_req = self.create_arp_req()
          pg_interface.add_stream(arp_req)
          pg_interface.enable_capture()
          self.test.pg_start()
          self.test.logger.info(self.test.vapi.cli("show trace"))
          try:
              captured_packet = pg_interface.wait_for_packet(1)
          except:
              self.test.logger.info("No ARP received on port %s" %
                                    pg_interface.name)
              return
          arp_reply = captured_packet.copy()  # keep original for exception
          try:
              if arp_reply[ARP].op == ARP.is_at:
                  self.test.logger.info("VPP %s MAC address is %s " %
                                        (self.name, arp_reply[ARP].hwsrc))
                  self._local_mac = arp_reply[ARP].hwsrc
              else:
                  self.test.logger.info("No ARP received on port %s" %
                                        pg_interface.name)
          except:
              self.test.logger.error(
                  ppp("Unexpected response to ARP request:", captured_packet))
              raise
  
      def resolve_ndp(self, pg_interface=None, timeout=1, link_layer=False):
          """Resolve NDP using provided packet-generator interface
  
          :param pg_interface: interface used to resolve, if None then this
              interface is used
          :param timeout: how long to wait for response before giving up
          :param link_layer: resolve for global address if False (default)
              or for link-layer address if True
  
          """
          if pg_interface is None:
              pg_interface = self
          addr = self.local_ip6_ll if link_layer else self.local_ip6
          self.test.logger.info("Sending NDP request for %s on port %s" %
                                (addr, pg_interface.name))
          ndp_req = self.create_ndp_req(addr)
          pg_interface.add_stream(ndp_req)
          pg_interface.enable_capture()
          self.test.pg_start()
          now = time.time()
          deadline = now + timeout
          # Enabling IPv6 on an interface can generate more than the
          # ND reply we are looking for (namely MLD). So loop through
          # the replies to look for want we want.
          while now < deadline:
              try:
                  captured_packet = pg_interface.wait_for_packet(
                      deadline - now, filter_out_fn=None)
              except:
                  self.test.logger.error(
                      "Timeout while waiting for NDP response")
                  raise
              ndp_reply = captured_packet.copy()  # keep original for exception
              try:
                  ndp_na = ndp_reply[ICMPv6ND_NA]
                  opt = ndp_na[ICMPv6NDOptDstLLAddr]
                  self.test.logger.info("VPP %s MAC address is %s " %
                                        (self.name, opt.lladdr))
                  self._local_mac = opt.lladdr
                  self.test.logger.debug(self.test.vapi.cli("show trace"))
                  # we now have the MAC we've been after
                  return
              except:
                  self.test.logger.info(
                      ppp("Unexpected response to NDP request:",
                          captured_packet))
              now = time.time()
  
          self.test.logger.debug(self.test.vapi.cli("show trace"))
          raise Exception("Timeout while waiting for NDP response")
  