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-rw-r--r--test/test_nat.py52
1 files changed, 52 insertions, 0 deletions
diff --git a/test/test_nat.py b/test/test_nat.py
index 5baadd89863..a705bd98fc0 100644
--- a/test/test_nat.py
+++ b/test/test_nat.py
@@ -139,6 +139,7 @@ class MethodHolder(VppTestCase):
self.verify_no_nat44_user()
self.vapi.nat_set_timeouts()
self.vapi.nat_set_addr_and_port_alloc_alg()
+ self.vapi.nat_set_mss_clamping()
def nat44_add_static_mapping(self, local_ip, external_ip='0.0.0.0',
local_port=0, external_port=0, vrf_id=0,
@@ -1002,6 +1003,21 @@ class MethodHolder(VppTestCase):
# sourceIPv4Address
self.assertEqual(src_addr, record[8])
+ def verify_mss_value(self, pkt, mss):
+ """
+ Verify TCP MSS value
+
+ :param pkt:
+ :param mss:
+ """
+ if not pkt.haslayer(IP) or not pkt.haslayer(TCP):
+ raise TypeError("Not a TCP/IP packet")
+
+ for option in pkt[TCP].options:
+ if option[0] == 'MSS':
+ self.assertEqual(option[1], mss)
+ self.assert_tcp_checksum_valid(pkt)
+
class TestNAT44(MethodHolder):
""" NAT44 Test Cases """
@@ -3295,6 +3311,42 @@ class TestNAT44(MethodHolder):
nsessions = nsessions + user.nsessions
self.assertLess(nsessions, 2 * max_sessions)
+ def test_mss_clamping(self):
+ """ TCP MSS clamping """
+ self.nat44_add_address(self.nat_addr)
+ self.vapi.nat44_interface_add_del_feature(self.pg0.sw_if_index)
+ self.vapi.nat44_interface_add_del_feature(self.pg1.sw_if_index,
+ is_inside=0)
+
+ p = (Ether(src=self.pg0.remote_mac, dst=self.pg0.local_mac) /
+ IP(src=self.pg0.remote_ip4, dst=self.pg1.remote_ip4) /
+ TCP(sport=self.tcp_port_in, dport=self.tcp_external_port,
+ flags="S", options=[('MSS', 1400)]))
+
+ self.vapi.nat_set_mss_clamping(enable=1, mss_value=1000)
+ self.pg0.add_stream(p)
+ self.pg_enable_capture(self.pg_interfaces)
+ self.pg_start()
+ capture = self.pg1.get_capture(1)
+ # Negotiated MSS value greater than configured - changed
+ self.verify_mss_value(capture[0], 1000)
+
+ self.vapi.nat_set_mss_clamping(enable=0)
+ self.pg0.add_stream(p)
+ self.pg_enable_capture(self.pg_interfaces)
+ self.pg_start()
+ capture = self.pg1.get_capture(1)
+ # MSS clamping disabled - negotiated MSS unchanged
+ self.verify_mss_value(capture[0], 1400)
+
+ self.vapi.nat_set_mss_clamping(enable=1, mss_value=1500)
+ self.pg0.add_stream(p)
+ self.pg_enable_capture(self.pg_interfaces)
+ self.pg_start()
+ capture = self.pg1.get_capture(1)
+ # Negotiated MSS value smaller than configured - unchanged
+ self.verify_mss_value(capture[0], 1400)
+
def tearDown(self):
super(TestNAT44, self).tearDown()
if not self.vpp_dead: