vlib: add virtual time support

Type: feature

Change-Id: Iabd76558e9c72ed8286cfeeb1fbaa4fde4832a90
Signed-off-by: Benoît Ganne <bganne@cisco.com>

src/vlib/CMakeLists.txt

@@ -90,6 +90,7 @@ add_vpp_library(vlib
   punt_node.c
   threads.c
   threads_cli.c
+  time.c
   trace.c
   unix/cli.c
   unix/input.c
@@ -130,6 +131,7 @@ add_vpp_library(vlib
   physmem.h
   punt.h
   threads.h
+  time.h
   trace_funcs.h
   trace.h
   unix/mc_socket.h

src/vlib/threads.c

@@ -1637,7 +1637,6 @@ static clib_error_t *
 show_clock_command_fn (vlib_main_t * vm,
 		       unformat_input_t * input, vlib_cli_command_t * cmd)
 {
-  int i;
   int verbose = 0;
   clib_timebase_t _tb, *tb = &_tb;
 
@@ -1650,24 +1649,19 @@ show_clock_command_fn (vlib_main_t * vm,
 		   verbose, format_clib_timebase_time,
 		   clib_timebase_now (tb));
 
-  if (vlib_get_n_threads () == 1)
-    return 0;
-
   vlib_cli_output (vm, "Time last barrier release %.9f",
 		   vm->time_last_barrier_release);
 
-  for (i = 1; i < vlib_get_n_threads (); i++)
+  foreach_vlib_main ()
     {
-      vlib_main_t *ovm = vlib_get_main_by_index (i);
-      if (ovm == 0)
-	continue;
+      vlib_cli_output (vm, "%d: %U", this_vlib_main->thread_index,
+		       format_clib_time, &this_vlib_main->clib_time, verbose);
 
-      vlib_cli_output (vm, "%d: %U", i, format_clib_time, &ovm->clib_time,
-		       verbose);
-
-      vlib_cli_output (
-	vm, "Thread %d offset %.9f error %.9f", i, ovm->time_offset,
-	vm->time_last_barrier_release - ovm->time_last_barrier_release);
+      vlib_cli_output (vm, "Thread %d offset %.9f error %.9f",
+		       this_vlib_main->thread_index,
+		       this_vlib_main->time_offset,
+		       vm->time_last_barrier_release -
+			 this_vlib_main->time_last_barrier_release);
     }
   return 0;
 }

src/vlib/time.c

@@ -0,0 +1,84 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright(c) 2021 Cisco Systems, Inc.
+ */
+
+/* Virtual time allows to adjust VPP clock by arbitrary amount of time.
+ * It is done such that the order of timer expirations is maintained,
+ * and if a timer expiration callback reschedule another timer, this
+ * timer will also properly expire in the right order. IOW, the order
+ * of events is preserved.
+ *
+ * When moving time forward, each VPP thread (main and workers) runs an
+ * instance of the input node 'virtual-time-input' below. This node is
+ * responsible of advancing its own VPP thread clock to the next timer
+ * expiration.  IOW each thread will move its clock independently one
+ * timer at a time. This also means that while moving time forward, each
+ * thread might not have the exact same view of what 'now' means. Once
+ * the main thread has finished moving its time forward, the worker thread
+ * barrier will ensure the timer between main and workers is synchronized.
+ *
+ * Using an input node in poll-mode has several advantages, including
+ * preventing 'unix-epoll-input' to sleep (as it will not sleep if at
+ * least one polling node is active). */
+
+#include <vlib/vlib.h>
+#include <vlib/time.h>
+
+static f64 vlib_time_virtual_stop;
+
+static uword
+vlib_time_virtual_input (vlib_main_t *vm, vlib_node_runtime_t *node,
+			 vlib_frame_t *frame)
+{
+  const f64 next = vlib_time_get_next_timer (vm);
+  /* each thread will advance its own time. In case a thread is much faster
+   * than another, we must make sure it does not run away... */
+  if (vlib_time_now (vm) + next > vlib_time_virtual_stop)
+    vlib_node_set_state (vm, node->node_index, VLIB_NODE_STATE_DISABLED);
+  else
+    vlib_time_adjust (vm, next);
+  return 0;
+}
+
+VLIB_REGISTER_NODE (vlib_time_virtual_input_node) = {
+  .function = vlib_time_virtual_input,
+  .type = VLIB_NODE_TYPE_INPUT,
+  .name = "virtual-time-input",
+  .state = VLIB_NODE_STATE_DISABLED,
+};
+
+static clib_error_t *
+vlib_time_virtual_adjust_command_fn (vlib_main_t *vm, unformat_input_t *input,
+				     vlib_cli_command_t *cmd)
+{
+  f64 val;
+
+  if (!unformat (input, "%f", &val))
+    return clib_error_create ("unknown input `%U'", format_unformat_error,
+			      input);
+
+  vlib_time_virtual_stop = vlib_time_now (vm) + val;
+
+  foreach_vlib_main ()
+    vlib_node_set_state (this_vlib_main, vlib_time_virtual_input_node.index,
+			 VLIB_NODE_STATE_POLLING);
+
+  vlib_worker_thread_barrier_release (vm);
+  while ((val = vlib_process_wait_for_event_or_clock (vm, val)) >= 0.001)
+    ;
+  /* this barrier sync will resynchronize all the clocks, so even if the main
+   * thread was faster than some workers, this will make sure the workers will
+   * disable their virtual-time-input node on their next iteration (as stop
+   * time is reached). If a worker is too slow, there is a slight chance
+   * several of its timers expire at the same time at this point. Time will
+   * tell... */
+  vlib_worker_thread_barrier_sync (vm);
+  return 0;
+}
+
+VLIB_CLI_COMMAND (vlib_time_virtual_command) = {
+  .path = "set clock adjust",
+  .short_help = "set clock adjust <nn>",
+  .function = vlib_time_virtual_adjust_command_fn,
+};

src/vlib/time.h

@@ -0,0 +1,26 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright(c) 2021 Cisco Systems, Inc.
+ */
+
+#ifndef included_vlib_time_h
+#define included_vlib_time_h
+
+#include <vlib/vlib.h>
+#include <vppinfra/tw_timer_1t_3w_1024sl_ov.h>
+
+static inline f64
+vlib_time_get_next_timer (vlib_main_t *vm)
+{
+  vlib_node_main_t *nm = &vm->node_main;
+  TWT (tw_timer_wheel) *wheel = nm->timing_wheel;
+  return TW (tw_timer_first_expires_in_ticks) (wheel) * wheel->timer_interval;
+}
+
+static inline void
+vlib_time_adjust (vlib_main_t *vm, f64 offset)
+{
+  vm->time_offset += offset;
+}
+
+#endif /* included_vlib_time_h */

test/framework.py

@@ -1284,6 +1284,10 @@ class VppTestCase(CPUInterface, unittest.TestCase):
             "Finished sleep (%s) - slept %es (wanted %es)",
             remark, after - before, timeout)
 
+    def virtual_sleep(self, timeout, remark=None):
+        self.logger.debug("Moving VPP time by %s (%s)", timeout, remark)
+        self.vapi.cli("set clock adjust %s" % timeout)
+
     def pg_send(self, intf, pkts, worker=None, trace=True):
         intf.add_stream(pkts, worker=worker)
         self.pg_enable_capture(self.pg_interfaces)

test/test_cnat.py

@@ -430,16 +430,9 @@ class TestCNatTranslation(CnatCommonTestCase):
         # all disapper
         #
         self.vapi.cli("test cnat scanner on")
-
-        n_tries = 0
+        self.virtual_sleep(2)
         sessions = self.vapi.cnat_session_dump()
-        while (len(sessions) and n_tries < 100):
-            n_tries += 1
-            sessions = self.vapi.cnat_session_dump()
-            self.sleep(2)
-            self.logger.info(self.vapi.cli("show cnat session verbose"))
-
-        self.assertTrue(n_tries < 100)
+        self.assertEqual(len(sessions), 0)
         self.vapi.cli("test cnat scanner off")
 
         #

test/test_det44.py

@@ -4,7 +4,6 @@ import socket
 import struct
 import unittest
 import scapy.compat
-from time import sleep
 from framework import VppTestCase, running_extended_tests
 from ipfix import IPFIX, Set, Template, Data, IPFIXDecoder
 from scapy.layers.inet import IP, TCP, UDP, ICMP
@@ -577,7 +576,6 @@ class TestDET44(VppTestCase):
             self.logger.error("TCP session termination failed")
             raise
 
-    @unittest.skipUnless(running_extended_tests, "part of extended tests")
     def test_session_timeout(self):
         """ Deterministic NAT session timeouts """
         self.vapi.det44_add_del_map(is_add=1, in_addr=self.pg0.remote_ip4,
@@ -599,7 +597,7 @@ class TestDET44(VppTestCase):
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
         self.pg1.get_capture(len(pkts))
-        sleep(15)
+        self.virtual_sleep(15)
 
         dms = self.vapi.det44_map_dump()
         self.assertEqual(0, dms[0].ses_num)
@@ -663,7 +661,6 @@ class TestDET44(VppTestCase):
 
         # verify IPFIX logging
         self.vapi.ipfix_flush()
-        sleep(1)
         capture = self.pg2.get_capture(2)
         ipfix = IPFIXDecoder()
         # first load template

test/test_l2_fib.py

@@ -486,7 +486,7 @@ class TestL2fib(VppTestCase):
         self.vapi.want_l2_macs_events()
         self.learn_hosts(bd1, hosts)
 
-        self.sleep(1)
+        self.virtual_sleep(1)
         self.logger.info(self.vapi.ppcli("show l2fib"))
         evs = self.vapi.collect_events()
         action = VppEnum.vl_api_mac_event_action_t.MAC_EVENT_ACTION_API_ADD
@@ -509,7 +509,7 @@ class TestL2fib(VppTestCase):
         self.sleep(1)
         self.learn_hosts(bd1, hosts)
 
-        self.sleep(1)
+        self.virtual_sleep(1)
         self.logger.info(self.vapi.ppcli("show l2fib"))
         evs = self.vapi.collect_events()
         action = VppEnum.vl_api_mac_event_action_t.MAC_EVENT_ACTION_API_ADD
@@ -560,7 +560,7 @@ class TestL2fib(VppTestCase):
         self.sleep(1)
         self.learn_hosts(bd1, hosts)
 
-        self.sleep(1)
+        self.virtual_sleep(1)
         self.logger.info(self.vapi.ppcli("show l2fib"))
         evs = self.vapi.collect_events()
         self.vapi.want_l2_macs_events2(enable_disable=0)
@@ -577,6 +577,5 @@ class TestL2fib(VppTestCase):
             self.assertLess(len(e), ev_macs * 10)
         self.assertEqual(len(learned_macs ^ macs), 0)
 
-
 if __name__ == '__main__':
     unittest.main(testRunner=VppTestRunner)

test/test_nat44_ed.py

@@ -2520,7 +2520,7 @@ class TestNAT44EDMW(TestNAT44ED):
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
         self.pg1.get_capture(len(pkts))
-        self.sleep(1.5, "wait for timeouts")
+        self.virtual_sleep(1.5, "wait for timeouts")
 
         pkts = []
         for i in range(0, self.max_sessions - 1):
@@ -2555,7 +2555,7 @@ class TestNAT44EDMW(TestNAT44ED):
         self.pg_start()
         self.pg1.get_capture(1)
 
-        self.sleep(6)
+        self.virtual_sleep(6)
 
         p = (Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
              IP(src=self.pg0.remote_ip4, dst=self.pg1.remote_ip4) /
@@ -3211,7 +3211,7 @@ class TestNAT44EDMW(TestNAT44ED):
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
 
-        self.sleep(new_transitory, "wait for transitory timeout")
+        self.virtual_sleep(new_transitory, "wait for transitory timeout")
         self.pg0.assert_nothing_captured(0)
 
         # session should still exist
@@ -3330,7 +3330,7 @@ class TestNAT44EDMW(TestNAT44ED):
             '/err/nat44-ed-in2out/drops due to TCP in transitory timeout')
         self.assertEqual(stats - in2out_drops, 1)
 
-        self.sleep(3)
+        self.virtual_sleep(3)
         # extra ACK packet in -> out - this will cause session to be wiped
         p = (Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
              IP(src=self.pg0.remote_ip4, dst=self.pg1.remote_ip4) /
@@ -3432,7 +3432,7 @@ class TestNAT44EDMW(TestNAT44ED):
             '/err/nat44-ed-in2out/drops due to TCP in transitory timeout')
         self.assertEqual(stats - in2out_drops, 1)
 
-        self.sleep(3)
+        self.virtual_sleep(3)
         # extra ACK packet in -> out - this will cause session to be wiped
         p = (Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
              IP(src=self.pg0.remote_ip4, dst=self.pg1.remote_ip4) /
@@ -3542,7 +3542,7 @@ class TestNAT44EDMW(TestNAT44ED):
             '/err/nat44-ed-in2out/drops due to TCP in transitory timeout')
         self.assertEqual(stats - in2out_drops, 1)
 
-        self.sleep(3)
+        self.virtual_sleep(3)
         # extra ACK packet in -> out - this will cause session to be wiped
         p = (Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
              IP(src=self.pg0.remote_ip4, dst=self.pg1.remote_ip4) /

test/test_nat44_ei.py

@@ -6,7 +6,6 @@ import socket
 import struct
 import unittest
 from io import BytesIO
-from time import sleep
 
 import scapy.compat
 from framework import VppTestCase, VppTestRunner
@@ -2342,7 +2341,6 @@ class TestNAT44EI(MethodHolder):
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
         self.pg1.assert_nothing_captured()
-        sleep(1)
         self.vapi.ipfix_flush()
         capture = self.pg3.get_capture(7)
         ipfix = IPFIXDecoder()
@@ -2404,7 +2402,6 @@ class TestNAT44EI(MethodHolder):
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
         self.pg1.assert_nothing_captured()
-        sleep(1)
         self.vapi.ipfix_flush()
         capture = self.pg3.get_capture(7)
         ipfix = IPFIXDecoder()
@@ -3446,7 +3443,7 @@ class TestNAT44EI(MethodHolder):
 
         # do not send ACK, active retry send HA event again
         self.pg_enable_capture(self.pg_interfaces)
-        sleep(12)
+        self.virtual_sleep(12)
         stats = self.statistics['/nat44-ei/ha/retry-count']
         self.assertEqual(stats[:, 0].sum(), 3)
         stats = self.statistics['/nat44-ei/ha/missed-count']

test/test_nat64.py

@@ -6,7 +6,6 @@ import socket
 import struct
 import unittest
 from io import BytesIO
-from time import sleep
 
 import scapy.compat
 from framework import tag_fixme_vpp_workers
@@ -934,7 +933,6 @@ class TestNAT64(VppTestCase):
 
         self.assertEqual(ses_num_end - ses_num_start, 3)
 
-    @unittest.skipUnless(running_extended_tests, "part of extended tests")
     def test_session_timeout(self):
         """ NAT64 session timeout """
         self.icmp_id_in = 1234
@@ -959,7 +957,7 @@ class TestNAT64(VppTestCase):
 
         ses_num_before_timeout = self.nat64_get_ses_num()
 
-        sleep(15)
+        self.virtual_sleep(15)
 
         # ICMP and TCP session after timeout
         ses_num_after_timeout = self.nat64_get_ses_num()
@@ -1700,7 +1698,6 @@ class TestNAT64(VppTestCase):
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
         self.pg1.assert_nothing_captured()
-        sleep(1)
         self.vapi.ipfix_flush()
         capture = self.pg3.get_capture(7)
         ipfix = IPFIXDecoder()
@@ -1728,7 +1725,6 @@ class TestNAT64(VppTestCase):
         self.pg_enable_capture(self.pg_interfaces)
         self.pg_start()
         self.pg1.assert_nothing_captured()
-        sleep(1)
         self.vapi.ipfix_flush()
         capture = self.pg3.get_capture(1)
         # verify events in data set

test/test_nat66.py

@@ -6,7 +6,6 @@ import socket
 import struct
 import unittest
 from io import BytesIO
-from time import sleep
 
 import scapy.compat
 from framework import VppTestCase, VppTestRunner, running_extended_tests

test/test_neighbor.py

@@ -1999,16 +1999,6 @@ class NeighborAgeTestCase(VppTestCase):
             i.unconfig_ip6()
             i.admin_down()
 
-    def wait_for_no_nbr(self, intf, address,
-                        n_tries=50, s_time=1):
-        while (n_tries):
-            if not find_nbr(self, intf, address):
-                return True
-            n_tries = n_tries - 1
-            self.sleep(s_time)
-
-        return False
-
     def verify_arp_req(self, rx, smac, sip, dip):
         ether = rx[Ether]
         self.assertEqual(ether.dst, "ff:ff:ff:ff:ff:ff")
@@ -2099,10 +2089,13 @@ class NeighborAgeTestCase(VppTestCase):
 
         self.vapi.cli("sh ip4 neighbor-sorted")
 
+        # age out neighbors
+        self.virtual_sleep(3)
+
         #
         # expect probes from all these ARP entries as they age
         # 3 probes for each neighbor 3*200 = 600
-        rxs = self.pg0.get_capture(600, timeout=8)
+        rxs = self.pg0.get_capture(600, timeout=2)
 
         for ii in range(3):
             for jj in range(200):
@@ -2113,9 +2106,7 @@ class NeighborAgeTestCase(VppTestCase):
         # 3 probes sent then 1 more second to see if a reply comes, before
         # they age out
         #
-        for jj in range(1, 201):
-            self.wait_for_no_nbr(self.pg0.sw_if_index,
-                                 self.pg0.remote_hosts[jj].ip4)
+        self.virtual_sleep(1)
 
         self.assertFalse(self.vapi.ip_neighbor_dump(sw_if_index=0xffffffff,
                                                     af=vaf.ADDRESS_IP4))
@@ -2142,7 +2133,7 @@ class NeighborAgeTestCase(VppTestCase):
             self.assertEqual(e.neighbor.mac_address,
                              self.pg0.remote_hosts[ii].mac)
 
-        self.sleep(10)
+        self.virtual_sleep(10)
         self.assertFalse(self.vapi.ip_neighbor_dump(sw_if_index=0xffffffff,
                                                     af=vaf.ADDRESS_IP4))
 
@@ -2190,7 +2181,7 @@ class NeighborAgeTestCase(VppTestCase):
                                      max_age=0,
                                      recycle=False)
 
-        self.sleep(10)
+        self.virtual_sleep(10)
         self.assertTrue(find_nbr(self,
                                  self.pg0.sw_if_index,
                                  self.pg0.remote_hosts[0].ip4))

test/test_reassembly.py

@@ -57,7 +57,7 @@ class TestIPv4Reassembly(VppTestCase):
         self.vapi.ip_reassembly_set(timeout_ms=0, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(timeout_ms=1000000, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10000)
@@ -480,7 +480,7 @@ Ethernet-Payload.IPv4-Packet.IPv4-Header.Fragment-Offset; Test-case: 5737'''
         self.src_if.add_stream(fragments)
         self.pg_start()
 
-        self.sleep(.25, "wait before sending rest of fragments")
+        self.virtual_sleep(.25, "wait before sending rest of fragments")
 
         self.src_if.add_stream(fragments2)
         self.pg_start()
@@ -539,7 +539,7 @@ class TestIPv4SVReassembly(VppTestCase):
             max_reassembly_length=1000,
             type=VppEnum.vl_api_ip_reass_type_t.IP_REASS_TYPE_SHALLOW_VIRTUAL,
             expire_walk_interval_ms=10)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(
             timeout_ms=1000000, max_reassemblies=1000,
             max_reassembly_length=1000,
@@ -672,7 +672,7 @@ class TestIPv4SVReassembly(VppTestCase):
             self.assertEqual(sent[Raw].payload, recvd[Raw].payload)
 
         # wait for cleanup
-        self.sleep(.25, "wait before sending rest of fragments")
+        self.virtual_sleep(.25, "wait before sending rest of fragments")
 
         # send rest of fragments - shouldn't be forwarded
         self.pg_enable_capture()
@@ -825,7 +825,7 @@ class TestIPv4MWReassembly(VppTestCase):
         self.vapi.ip_reassembly_set(timeout_ms=0, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(timeout_ms=1000000, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10000)
@@ -997,7 +997,7 @@ class TestIPv6Reassembly(VppTestCase):
         self.vapi.ip_reassembly_set(timeout_ms=0, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10, is_ip6=1)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(timeout_ms=1000000, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10000, is_ip6=1)
@@ -1337,7 +1337,7 @@ class TestIPv6Reassembly(VppTestCase):
         self.src_if.add_stream(fragments)
         self.pg_start()
 
-        self.sleep(.25, "wait before sending rest of fragments")
+        self.virtual_sleep(.25, "wait before sending rest of fragments")
 
         self.src_if.add_stream(fragments2)
         self.pg_start()
@@ -1473,7 +1473,7 @@ class TestIPv6MWReassembly(VppTestCase):
         self.vapi.ip_reassembly_set(timeout_ms=0, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10, is_ip6=1)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(timeout_ms=1000000, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=1000, is_ip6=1)
@@ -1638,7 +1638,7 @@ class TestIPv6SVReassembly(VppTestCase):
             max_reassembly_length=1000,
             type=VppEnum.vl_api_ip_reass_type_t.IP_REASS_TYPE_SHALLOW_VIRTUAL,
             expire_walk_interval_ms=10, is_ip6=1)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(
             timeout_ms=1000000, max_reassemblies=1000,
             max_reassembly_length=1000,
@@ -1769,7 +1769,7 @@ class TestIPv6SVReassembly(VppTestCase):
             self.assertEqual(sent[Raw].payload, recvd[Raw].payload)
 
         # wait for cleanup
-        self.sleep(.25, "wait before sending rest of fragments")
+        self.virtual_sleep(.25, "wait before sending rest of fragments")
 
         # send rest of fragments - shouldn't be forwarded
         self.pg_enable_capture()
@@ -1845,7 +1845,7 @@ class TestIPv4ReassemblyLocalNode(VppTestCase):
         self.vapi.ip_reassembly_set(timeout_ms=0, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(timeout_ms=1000000, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10000)
@@ -1981,7 +1981,7 @@ class TestFIFReassembly(VppTestCase):
         self.vapi.ip_reassembly_set(timeout_ms=0, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10, is_ip6=1)
-        self.sleep(.25)
+        self.virtual_sleep(.25)
         self.vapi.ip_reassembly_set(timeout_ms=1000000, max_reassemblies=1000,
                                     max_reassembly_length=1000,
                                     expire_walk_interval_ms=10000)