src/vnet/srv6/sr_steering.md


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# Steering packets into a SR Policy     {#srv6_steering_doc}

## steer packets uging the sr steering policy

To steer packets in Transit into an SR policy (T.Insert, T.Encaps and T.Encaps.L2 behaviors), the user needs to create an 'sr steering policy'.

    sr steer l3 2001::/64 via index 1
    sr steer l3 2001::/64 via bsid cafe::1
    sr steer l3 2001::/64 via bsid cafe::1 fib-table 3
    sr steer l3 10.0.0.0/16 via bsid cafe::1
    sr steer l2 TenGE0/1/0 via bsid cafe::1

Disclaimer: The T.Encaps.L2 will steer L2 frames into an SR Policy. Notice that creating an SR steering policy for L2 frames will actually automatically *put the interface into promiscous mode*.

## steer packets using the classifier

Another way to steer packet is to use the classifier.

First the user need to manually add the source routing node to the list of the
ip6-inacl next nodes.
Using the python api this can be donne with:

    # jsonfiles = get list of json api files
    vpp = VPP(jsonfiles)
    vpp.add_node_next(node_name='ip6-inacl', next_name='sr-pl-rewrite-insert')

Below is a classifier mask filtering all the packets from the interface
TenGigabitEthernet5/0/0 on ip version and moving all ipv6 packets to the
sr-pl-rewrite-insert node (dropping the others) and applying the source routing
index 2.
In essence, this means "apply this sr policy to all the packets from this interface)

    vpp# classify table miss-next 0 current-data-flag 1  mask hex f000000000000000 skip 0
    vpp# classify session acl-hit-next 1 table-index 0 match hex 6000000000000000 action set-sr-policy-index 2
    vpp# set interface input acl intfc TenGigabitEthernet5/0/0 ip6-table 0
#!/usr/bin/env python3

import unittest
import binascii
from socket import AF_INET6

from framework import VppTestCase, VppTestRunner
from vpp_ip import DpoProto
from vpp_ip_route import VppIpRoute, VppRoutePath, VppIpTable

import scapy.compat
from scapy.packet import Raw
from scapy.layers.l2 import Ether, Dot1Q
from scapy.layers.inet6 import IPv6, UDP, IPv6ExtHdrSegmentRouting
from scapy.layers.inet import IP, UDP

from util import ppp


class TestSRv6(VppTestCase):
    """ SRv6 Flow-based Dynamic Proxy plugin Test Case """

    @classmethod
    def setUpClass(self):
        super(TestSRv6, self).setUpClass()

    @classmethod
    def tearDownClass(cls):
        super(TestSRv6, cls).tearDownClass()

    def setUp(self):
        """ Perform test setup before each test case.
        """
        super(TestSRv6, self).setUp()

        # packet sizes, inclusive L2 overhead
        self.pg_packet_sizes = [64, 512, 1518, 9018]

        # reset packet_infos
        self.reset_packet_infos()

    def tearDown(self):
        """ Clean up test setup after each test case.
        """
        self.teardown_interfaces()

        super(TestSRv6, self).tearDown()

    def configure_interface(self,
                            interface,
                            ipv6=False, ipv4=False,
                            ipv6_table_id=0, ipv4_table_id=0):
        """ Configure interface.
        :param ipv6: configure IPv6 on interface
        :param ipv4: configure IPv4 on interface
        :param ipv6_table_id: FIB table_id for IPv6
        :param ipv4_table_id: FIB table_id for IPv4
        """
        self.logger.debug("Configuring interface %s" % (interface.name))
        if ipv6:
            self.logger.debug("Configuring IPv6")
            interface.set_table_ip6(ipv6_table_id)
            interface.config_ip6()
            interface.resolve_ndp(timeout=5)
        if ipv4:
            self.logger.debug("Configuring IPv4")
            interface.set_table_ip4(ipv4_table_id)
            interface.config_ip4()
            interface.resolve_arp()
        interface.admin_up()

    def setup_interfaces(self, ipv6=[], ipv4=[],
                         ipv6_table_id=[], ipv4_table_id=[]):
        """ Create and configure interfaces.

        :param ipv6: list of interface IPv6 capabilities
        :param ipv4: list of interface IPv4 capabilities
        :param ipv6_table_id: list of intf IPv6 FIB table_ids
        :param ipv4_table_id: list of intf IPv4 FIB table_ids
        :returns: List of created interfaces.
        """
        # how many interfaces?
        if len(ipv6):
            count = len(ipv6)
        else:
            count = len(ipv4)
        self.logger.debug("Creating and configuring %d interfaces" % (count))

        # fill up ipv6 and ipv4 lists if needed
        # not enabled (False) is the default
        if len(ipv6) < count:
            ipv6 += (count - len(ipv6)) * [False]
        if len(ipv4) < count:
            ipv4 += (count - len(ipv4)) * [False]

        # fill up table_id lists if needed
        # table_id 0 (global) is the default
        if len(ipv6_table_id) < count:
            ipv6_table_id += (count - len(ipv6_table_id)) * [0]
        if len(ipv4_table_id) < count:
            ipv4_table_id += (count - len(ipv4_table_id)) * [0]

        # create 'count' pg interfaces
        self.create_pg_interfaces(range(count))

        # setup all interfaces
        for i in range(count):
            intf = self.pg_interfaces[i]
            self.configure_interface(intf,
                                     ipv6[i], ipv4[i],
                                     ipv6_table_id[i], ipv4_table_id[i])

        if any(ipv6):
            self.logger.debug(self.vapi.cli("show ip6 neighbors"))
        if any(ipv4):
            self.logger.debug(self.vapi.cli("show ip4 neighbors"))
        self.logger.debug(self.vapi.cli("show interface"))
        self.logger.debug(self.vapi.cli("show hardware"))

        return self.pg_interfaces

    def teardown_interfaces(self):
        """ Unconfigure and bring down interface.
        """
        self.logger.debug("Tearing down interfaces")
        # tear down all interfaces
        # AFAIK they cannot be deleted
        for i in self.pg_interfaces:
            self.logger.debug("Tear down interface %s" % (i.name))
            i.admin_down()
            i.unconfig()
            i.set_table_ip4(0)
            i.set_table_ip6(0)

    def test_SRv6_End_AD_IPv6(self):
        """ Test SRv6 End.AD behavior with IPv6 traffic.
        """
        self.src_addr = 'a0::'
        self.sid_list = ['a1::', 'a2::a6', 'a3::']
        self.test_sid_index = 1

        # send traffic to one destination interface
        # source and destination interfaces are IPv6 only
        self.setup_interfaces(ipv6=[True, True])

        # configure route to next segment
        route = VppIpRoute(self, self.sid_list[self.test_sid_index + 1], 128,
                           [VppRoutePath(self.pg0.remote_ip6,
                                         self.pg0.sw_if_index,
                                         proto=DpoProto.DPO_PROTO_IP6)])
        route.add_vpp_config()

        # configure SRv6 localSID behavior
        cli_str = "sr localsid address " + \
                  self.sid_list[self.test_sid_index] + \
                  " behavior end.ad.flow" + \
                  " nh " + self.pg1.remote_ip6 + \
                  " oif " + self.pg1.name + \
                  " iif " + self.pg1.name
        self.vapi.cli(cli_str)

        # log the localsids
        self.logger.debug(self.vapi.cli("show sr localsid"))

        # send one packet per packet size
        count = len(self.pg_packet_sizes)

        # prepare IPv6 in SRv6 headers
        packet_header1 = self.create_packet_header_IPv6_SRH_IPv6(
            srcaddr=self.src_addr,
            sidlist=self.sid_list[::-1],
            segleft=len(self.sid_list) - self.test_sid_index - 1)

        # generate packets (pg0->pg1)
        pkts1 = self.create_stream(self.pg0, self.pg1, packet_header1,
                                   self.pg_packet_sizes, count)

        # send packets and verify received packets
        self.send_and_verify_pkts(self.pg0, pkts1, self.pg1,
                                  self.compare_rx_tx_packet_End_AD_IPv6_out)

        # log the localsid counters
        self.logger.info(self.vapi.cli("show sr localsid"))

        # prepare IPv6 header for returning packets
        packet_header2 = self.create_packet_header_IPv6()

        # generate returning packets (pg1->pg0)
        pkts2 = self.create_stream(self.pg1, self.pg0, packet_header2,
                                   self.pg_packet_sizes, count)

        # send packets and verify received packets
        self.send_and_verify_pkts(self.pg1, pkts2, self.pg0,
                                  self.compare_rx_tx_packet_End_AD_IPv6_in)

        # log the localsid counters
        self.logger.info(self.vapi.cli("show sr localsid"))

        # remove SRv6 localSIDs
        cli_str = "sr localsid del address " + \
                  self.sid_list[self.test_sid_index]
        self.vapi.cli(cli_str)

        # cleanup interfaces
        self.teardown_interfaces()

    def compare_rx_tx_packet_End_AD_IPv6_out(self, tx_pkt, rx_pkt):
        """ Compare input and output packet after passing End.AD with IPv6

        :param tx_pkt: transmitted packet
        :param rx_pkt: received packet
        """

        # get first (outer) IPv6 header of rx'ed packet
        rx_ip = rx_pkt.getlayer(IPv6)

        tx_ip = tx_pkt.getlayer(IPv6)
        tx_ip2 = tx_pkt.getlayer(IPv6, 2)

        # verify if rx'ed packet has no SRH
        self.assertFalse(rx_pkt.haslayer(IPv6ExtHdrSegmentRouting))

        # the whole rx_ip pkt should be equal to tx_ip2
        # except for the hlim field
        #   -> adjust tx'ed hlim to expected hlim
        tx_ip2.hlim = tx_ip2.hlim - 1

        self.assertEqual(rx_ip, tx_ip2)

        self.logger.debug("packet verification: SUCCESS")

    def compare_rx_tx_packet_End_AD_IPv6_in(self, tx_pkt, rx_pkt):
        """ Compare input and output packet after passing End.AD

        :param tx_pkt: transmitted packet
        :param rx_pkt: received packet
        """

        # get first (outer) IPv6 header of rx'ed packet
        rx_ip = rx_pkt.getlayer(IPv6)
        # received ip.src should be equal to SR Policy source
        self.assertEqual(rx_ip.src, self.src_addr)
        # received ip.dst should be equal to expected sidlist next segment
        self.assertEqual(rx_ip.dst, self.sid_list[self.test_sid_index + 1])

        # rx'ed packet should have SRH
        self.assertTrue(rx_pkt.haslayer(IPv6ExtHdrSegmentRouting))

        # get SRH
        rx_srh = rx_pkt.getlayer(IPv6ExtHdrSegmentRouting)
        # rx'ed seglist should be equal to SID-list in reversed order
        self.assertEqual(rx_srh.addresses, self.sid_list[::-1])
        # segleft should be equal to previous segleft value minus 1
        self.assertEqual(rx_srh.segleft,
                         len(self.sid_list) - self.test_sid_index - 2)
        # lastentry should be equal to the SID-list length minus 1
        self.assertEqual(rx_srh.lastentry, len(self.sid_list) - 1)

        # the whole rx'ed pkt beyond SRH should be equal to tx'ed pkt
        # except for the hop-limit field
        tx_ip = tx_pkt.getlayer(IPv6)
        #   -> update tx'ed hlim to the expected hlim
        tx_ip.hlim -= 1
        #   -> check payload
        self.assertEqual(rx_srh.payload, tx_ip)

        self.logger.debug("packet verification: SUCCESS")

    def test_SRv6_End_AD_IPv4(self):
        """ Test SRv6 End.AD behavior with IPv4 traffic.
        """
        self.src_addr = 'a0::'
        self.sid_list = ['a1::', 'a2::a4', 'a3::']
        self.test_sid_index = 1

        # send traffic to one destination interface
        # source and destination interfaces are IPv6 only
        self.setup_interfaces(ipv6=[True, False], ipv4=[False, True])

        # configure route to next segment
        route = VppIpRoute(self, self.sid_list[self.test_sid_index + 1], 128,
                           [VppRoutePath(self.pg0.remote_ip6,
                                         self.pg0.sw_if_index,
                                         proto=DpoProto.DPO_PROTO_IP6)])
        route.add_vpp_config()

        # configure SRv6 localSID behavior
        cli_str = "sr localsid address " + \
                  self.sid_list[self.test_sid_index] + \
                  " behavior end.ad.flow" + \
                  " nh " + self.pg1.remote_ip4 + \
                  " oif " + self.pg1.name + \
                  " iif " + self.pg1.name
        self.vapi.cli(cli_str)

        # log the localsids
        self.logger.debug(self.vapi.cli("show sr localsid"))

        # send one packet per packet size
        count = len(self.pg_packet_sizes)

        # prepare IPv4 in SRv6 headers
        packet_header1 = self.create_packet_header_IPv6_SRH_IPv4(
            srcaddr=self.src_addr,
            sidlist=self.sid_list[::-1],
            segleft=len(self.sid_list) - self.test_sid_index - 1)

        # generate packets (pg0->pg1)
        pkts1 = self.create_stream(self.pg0, self.pg1, packet_header1,
                                   self.pg_packet_sizes, count)

        # send packets and verify received packets
        self.send_and_verify_pkts(self.pg0, pkts1, self.pg1,
                                  self.compare_rx_tx_packet_End_AD_IPv4_out)

        # log the localsid counters
        self.logger.info(self.vapi.cli("show sr localsid"))

        # prepare IPv6 header for returning packets
        packet_header2 = self.create_packet_header_IPv4()

        # generate returning packets (pg1->pg0)
        pkts2 = self.create_stream(self.pg1, self.pg0, packet_header2,
                                   self.pg_packet_sizes, count)

        # send packets and verify received packets
        self.send_and_verify_pkts(self.pg1, pkts2, self.pg0,
                                  self.compare_rx_tx_packet_End_AD_IPv4_in)

        # log the localsid counters
        self.logger.info(self.vapi.cli("show sr localsid"))

        # remove SRv6 localSIDs
        cli_str = "sr localsid del address " + \
                  self.sid_list[self.test_sid_index]
        self.vapi.cli(cli_str)

        # cleanup interfaces
        self.teardown_interfaces()

    def compare_rx_tx_packet_End_AD_IPv4_out(self, tx_pkt, rx_pkt):
        """ Compare input and output packet after passing End.AD with IPv4

        :param tx_pkt: transmitted packet
        :param rx_pkt: received packet
        """

        # get IPv4 header of rx'ed packet
        rx_ip = rx_pkt.getlayer(IP)

        tx_ip = tx_pkt.getlayer(IPv6)
        tx_ip2 = tx_pkt.getlayer(IP)

        # verify if rx'ed packet has no SRH
        self.assertFalse(rx_pkt.haslayer(IPv6ExtHdrSegmentRouting))

        # the whole rx_ip pkt should be equal to tx_ip2
        # except for the ttl field and ip checksum
        #   -> adjust tx'ed ttl to expected ttl
        tx_ip2.ttl = tx_ip2.ttl - 1
        #   -> set tx'ed ip checksum to None and let scapy recompute
        tx_ip2.chksum = None
        # read back the pkt (with str()) to force computing these fields
        # probably other ways to accomplish this are possible
        tx_ip2 = IP(scapy.compat.raw(tx_ip2))

        self.assertEqual(rx_ip, tx_ip2)

        self.logger.debug("packet verification: SUCCESS")

    def compare_rx_tx_packet_End_AD_IPv4_in(self, tx_pkt, rx_pkt):
        """ Compare input and output packet after passing End.AD

        :param tx_pkt: transmitted packet
        :param rx_pkt: received packet
        """

        # get first (outer) IPv6 header of rx'ed packet
        rx_ip = rx_pkt.getlayer(IPv6)
        # received ip.src should be equal to SR Policy source
        self.assertEqual(rx_ip.src, self.src_addr)
        # received ip.dst should be equal to expected sidlist next segment
        self.assertEqual(rx_ip.dst, self.sid_list[self.test_sid_index + 1])

        # rx'ed packet should have SRH
        self.assertTrue(rx_pkt.haslayer(IPv6ExtHdrSegmentRouting))

        # get SRH
        rx_srh = rx_pkt.getlayer(IPv6ExtHdrSegmentRouting)
        # rx'ed seglist should be equal to SID-list in reversed order
        self.assertEqual(rx_srh.addresses, self.sid_list[::-1])
        # segleft should be equal to previous segleft value minus 1
        self.assertEqual(rx_srh.segleft,
                         len(self.sid_list) - self.test_sid_index - 2)
        # lastentry should be equal to the SID-list length minus 1
        self.assertEqual(rx_srh.lastentry, len(self.sid_list) - 1)

        # the whole rx'ed pkt beyond SRH should be equal to tx'ed pkt
        # except for the ttl field and ip checksum
        tx_ip = tx_pkt.getlayer(IP)
        #   -> adjust tx'ed ttl to expected ttl
        tx_ip.ttl = tx_ip.ttl - 1
        #   -> set tx'ed ip checksum to None and let scapy recompute
        tx_ip.chksum = None
        #   -> read back the pkt (with str()) to force computing these fields
        # probably other ways to accomplish this are possible
        self.assertEqual(rx_srh.payload, IP(scapy.compat.raw(tx_ip)))

        self.logger.debug("packet verification: SUCCESS")

    def create_stream(self, src_if, dst_if, packet_header, packet_sizes,
                      count):
        """Create SRv6 input packet stream for defined interface.

        :param VppInterface src_if: Interface to create packet stream for
        :param VppInterface dst_if: destination interface of packet stream
        :param packet_header: Layer3 scapy packet headers,
                L2 is added when not provided,
                Raw(payload) with packet_info is added
        :param list packet_sizes: packet stream pckt sizes,sequentially applied
               to packets in stream have
        :param int count: number of packets in packet stream
        :return: list of packets
        """
        self.logger.info("Creating packets")
        pkts = []
        for i in range(0, count - 1):
            payload_info = self.create_packet_info(src_if, dst_if)
            self.logger.debug(
                "Creating packet with index %d" % (payload_info.index))
            payload = self.info_to_payload(payload_info)
            # add L2 header if not yet provided in packet_header
            if packet_header.getlayer(0).name == 'Ethernet':
                p = packet_header / Raw(payload)
            else:
                p = Ether(dst=src_if.local_mac, src=src_if.remote_mac) / \
                    packet_header / Raw(payload)
            size = packet_sizes[i % len(packet_sizes)]
            self.logger.debug("Packet size %d" % (size))
            self.extend_packet(p, size)
            # we need to store the packet with the automatic fields computed
            # read back the dumped packet (with str())
            # to force computing these fields
            # probably other ways are possible
            p = Ether(scapy.compat.raw(p))
            payload_info.data = p.copy()
            self.logger.debug(ppp("Created packet:", p))
            pkts.append(p)
        self.logger.info("Done creating packets")
        return pkts

    def send_and_verify_pkts(self, input, pkts, output, compare_func):
        """Send packets and verify received packets using compare_func

        :param input: ingress interface of DUT
        :param pkts: list of packets to transmit
        :param output: egress interface of DUT
        :param compare_func: function to compare in and out packets
        """
        # add traffic stream to input interface
        input.add_stream(pkts)

        # enable capture on all interfaces
        self.pg_enable_capture(self.pg_interfaces)

        # start traffic
        self.logger.info("Starting traffic")
        self.pg_start()

        # get output capture
        self.logger.info("Getting packet capture")
        capture = output.get_capture()

        # assert nothing was captured on input interface
        # input.assert_nothing_captured()

        # verify captured packets
        self.verify_captured_pkts(output, capture, compare_func)

    def create_packet_header_IPv6(self, saddr='1234::1', daddr='4321::1',
                                  sport=1234, dport=1234):
        """Create packet header: IPv6 header, UDP header

        :param dst: IPv6 destination address

        IPv6 source address is 1234::1
        IPv6 destination address is 4321::1
        UDP source port and destination port are 1234
        """

        p = IPv6(src=saddr, dst=daddr) / UDP(sport=sport, dport=dport)
        return p

    def create_packet_header_IPv6_SRH_IPv6(self, srcaddr, sidlist, segleft,
                                           insrc='1234::1', indst='4321::1',
                                           sport=1234, dport=1234):
        """Create packet header: IPv6 encapsulated in SRv6:
        IPv6 header with SRH, IPv6 header, UDP header

        :param int srcaddr: outer source address
        :param list sidlist: segment list of outer IPv6 SRH
        :param int segleft: segments-left field of outer IPv6 SRH

        Outer IPv6 source address is set to srcaddr
        Outer IPv6 destination address is set to sidlist[segleft]
        Inner IPv6 source addresses is 1234::1
        Inner IPv6 destination address is 4321::1
        UDP source port and destination port are 1234
        """

        p = IPv6(src=srcaddr, dst=sidlist[segleft]) / \
            IPv6ExtHdrSegmentRouting(addresses=sidlist,
                                     segleft=segleft, nh=41) / \
            IPv6(src=insrc, dst=indst) / \
            UDP(sport=sport, dport=dport)
        return p

    def create_packet_header_IPv4(self):
        """Create packet header: IPv4 header, UDP header

        :param dst: IPv4 destination address

        IPv4 source address is 123.1.1.1
        IPv4 destination address is 124.1.1.1
        UDP source port and destination port are 1234
        """

        p = IP(src='123.1.1.1', dst='124.1.1.1') / UDP(sport=1234, dport=1234)
        return p

    def create_packet_header_IPv6_SRH_IPv4(self, srcaddr, sidlist, segleft):
        """Create packet header: IPv4 encapsulated in SRv6:
        IPv6 header with SRH, IPv4 header, UDP header

        :param int srcaddr: outer source address
        :param list sidlist: segment list of outer IPv6 SRH
        :param int segleft: segments-left field of outer IPv6 SRH

        Outer IPv6 source address is set to srcaddr
        Outer IPv6 destination address is set to sidlist[segleft]
        Inner IPv4 source address is 123.1.1.1
        Inner IPv4 destination address is 124.1.1.1
        UDP source port and destination port are 1234
        """

        p = IPv6(src=srcaddr, dst=sidlist[segleft]) / \
            IPv6ExtHdrSegmentRouting(addresses=sidlist,
                                     segleft=segleft, nh=4) / \
            IP(src='123.1.1.1', dst='124.1.1.1') / \
            UDP(sport=1234, dport=1234)
        return p

    def get_payload_info(self, packet):
        """ Extract the payload_info from the packet
        """
        # in most cases, payload_info is in packet[Raw]
        # but packet[Raw] gives the complete payload
        # (incl L2 header) for the T.Encaps L2 case
        try:
            payload_info = self.payload_to_info(packet[Raw])

        except:
            # remote L2 header from packet[Raw]:
            # take packet[Raw], convert it to an Ether layer
            # and then extract Raw from it
            payload_info = self.payload_to_info(
                Ether(scapy.compat.raw(packet[Raw]))[Raw])

        return payload_info

    def verify_captured_pkts(self, dst_if, capture, compare_func):
        """
        Verify captured packet stream for specified interface.
        Compare ingress with egress packets using the specified compare fn

        :param dst_if: egress interface of DUT
        :param capture: captured packets
        :param compare_func: function to compare in and out packet
        """
        self.logger.info("Verifying capture on interface %s using function %s"
                         % (dst_if.name, compare_func.__name__))

        last_info = dict()
        for i in self.pg_interfaces:
            last_info[i.sw_if_index] = None
        dst_sw_if_index = dst_if.sw_if_index

        for packet in capture:
            try:
                # extract payload_info from packet's payload
                payload_info = self.get_payload_info(packet)
                packet_index = payload_info.index

                self.logger.debug("Verifying packet with index %d"
                                  % (packet_index))
                # packet should have arrived on the expected interface
                self.assertEqual(payload_info.dst, dst_sw_if_index)
                self.logger.debug(
                    "Got packet on interface %s: src=%u (idx=%u)" %
                    (dst_if.name, payload_info.src, packet_index))

                # search for payload_info with same src and dst if_index
                # this will give us the transmitted packet
                next_info = self.get_next_packet_info_for_interface2(
                    payload_info.src, dst_sw_if_index,
                    last_info[payload_info.src])
                last_info[payload_info.src] = next_info
                # next_info should not be None
                self.assertTrue(next_info is not None)
                # index of tx and rx packets should be equal
                self.assertEqual(packet_index, next_info.index)
                # data field of next_info contains the tx packet
                txed_packet = next_info.data

                self.logger.debug(ppp("Transmitted packet:",
                                      txed_packet))  # ppp=Pretty Print Packet

                self.logger.debug(ppp("Received packet:", packet))

                # compare rcvd packet with expected packet using compare_func
                compare_func(txed_packet, packet)

            except:
                self.logger.error(ppp("Unexpected or invalid packet:", packet))
                raise

        # have all expected packets arrived?
        for i in self.pg_interfaces:
            remaining_packet = self.get_next_packet_info_for_interface2(
                i.sw_if_index, dst_sw_if_index, last_info[i.sw_if_index])
            self.assertTrue(remaining_packet is None,
                            "Interface %s: Packet expected from interface %s "
                            "didn't arrive" % (dst_if.name, i.name))


if __name__ == '__main__':
    unittest.main(testRunner=VppTestRunner)