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#!/usr/bin/python3
#
# Copyright 2017 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import posix
import select
from socket import * # pylint: disable=wildcard-import
import time
import unittest
from math import pow
import multinetwork_base
def accumulate(lis):
total = 0
for x in lis:
total += x
yield total
# This test attempts to validate time related behavior of the kernel
# under test and is therefore inherently prone to races. To avoid
# flakes, this test is biased to declare RFC 7559 RS backoff is
# present on the assumption that repeated runs will detect
# non-compliant kernels with high probability.
#
# If higher confidence is required, REQUIRED_SAMPLES and
# SAMPLE_INTERVAL can be increased at the cost of increased runtime.
class ResilientRouterSolicitationTest(multinetwork_base.MultiNetworkBaseTest):
"""Tests for IPv6 'resilient rs' RFC 7559 backoff behaviour.
Relevant kernel commits:
upstream:
bd11f0741fa5 ipv6 addrconf: implement RFC7559 router solicitation backoff
android-4.4:
e246a2f11fcc UPSTREAM: ipv6 addrconf: implement RFC7559 router solicitation backoff
android-4.1:
c6e9a50816a0 UPSTREAM: ipv6 addrconf: implement RFC7559 router solicitation backoff
android-3.18:
2a7561c61417 UPSTREAM: ipv6 addrconf: implement RFC7559 router solicitation backoff
android-3.10:
ce2d59ac01f3 BACKPORT: ipv6 addrconf: implement RFC7559 router solicitation backoff
"""
ROUTER_SOLICIT = 133
_TEST_NETID = 123
_PROC_NET_TUNABLE = "/proc/sys/net/ipv6/conf/%s/%s"
@classmethod
def setUpClass(cls):
return
def setUp(self):
return
@classmethod
def tearDownClass(cls):
return
def tearDown(self):
return
@classmethod
def isIPv6RouterSolicitation(cls, packet):
def ToByte(c):
return c if isinstance(c, int) else ord(c)
return ((len(packet) >= 14 + 40 + 1) and
# Use net_test.ETH_P_IPV6 here
(ToByte(packet[12]) == 0x86) and
(ToByte(packet[13]) == 0xdd) and
(ToByte(packet[14]) >> 4 == 6) and
(ToByte(packet[14 + 40]) == cls.ROUTER_SOLICIT))
def makeTunInterface(self, netid):
defaultDisableIPv6Path = self._PROC_NET_TUNABLE % ("default", "disable_ipv6")
savedDefaultDisableIPv6 = self.GetSysctl(defaultDisableIPv6Path)
self.SetSysctl(defaultDisableIPv6Path, 1)
tun = self.CreateTunInterface(netid)
self.SetSysctl(defaultDisableIPv6Path, savedDefaultDisableIPv6)
return tun
def testFeatureExists(self):
return
def testRouterSolicitationBackoff(self):
# Test error tolerance
EPSILON = 0.15
# Minimum RFC3315 S14 backoff
MIN_EXP = 1.9 - EPSILON
# Maximum RFC3315 S14 backoff
MAX_EXP = 2.1 + EPSILON
SOLICITATION_INTERVAL = 1
# Linear backoff for 4 samples yields 3.5 < T < 4.5
# Exponential backoff for 4 samples yields 4.36 < T < 10.39
REQUIRED_SAMPLES = 4
# Give up after 10 seconds. Tuned for REQUIRED_SAMPLES = 4
SAMPLE_INTERVAL = 10
# Practically unlimited backoff
SOLICITATION_MAX_INTERVAL = 1000
MIN_LIN = SOLICITATION_INTERVAL * (0.9 - EPSILON)
MAX_LIN = SOLICITATION_INTERVAL * (1.1 + EPSILON)
netid = self._TEST_NETID
tun = self.makeTunInterface(netid)
poll = select.poll()
poll.register(tun, select.POLLIN | select.POLLPRI)
PROC_SETTINGS = [
("router_solicitation_delay", 1),
("router_solicitation_interval", SOLICITATION_INTERVAL),
("router_solicitation_max_interval", SOLICITATION_MAX_INTERVAL),
("router_solicitations", -1),
("disable_ipv6", 0) # MUST be last
]
iface = self.GetInterfaceName(netid)
for tunable, value in PROC_SETTINGS:
self.SetSysctl(self._PROC_NET_TUNABLE % (iface, tunable), value)
start = time.time()
deadline = start + SAMPLE_INTERVAL
rsSendTimes = []
while True:
now = time.time();
poll.poll((deadline - now) * 1000)
try:
packet = posix.read(tun.fileno(), 4096)
except OSError:
break
txTime = time.time()
if txTime > deadline:
break;
if not self.isIPv6RouterSolicitation(packet):
continue
# Record time relative to first router solicitation
rsSendTimes.append(txTime - start)
# Exit early if we have at least REQUIRED_SAMPLES
if len(rsSendTimes) >= REQUIRED_SAMPLES:
continue
# Expect at least REQUIRED_SAMPLES router solicitations
self.assertLessEqual(REQUIRED_SAMPLES, len(rsSendTimes))
# Compute minimum and maximum bounds for RFC3315 S14 exponential backoff.
# First retransmit is linear backoff, subsequent retransmits are exponential
min_exp_bound = accumulate([MIN_LIN * pow(MIN_EXP, i) for i in range(0, len(rsSendTimes))])
max_exp_bound = accumulate([MAX_LIN * pow(MAX_EXP, i) for i in range(0, len(rsSendTimes))])
# Assert that each sample falls within the worst case interval. If all samples fit we accept
# the exponential backoff hypothesis
for (t, min_exp, max_exp) in zip(rsSendTimes[1:], min_exp_bound, max_exp_bound):
self.assertLess(min_exp, t)
self.assertGreater(max_exp, t)
if __name__ == "__main__":
unittest.main()
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