tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1#!/bin/bash
2# SPDX-License-Identifier: GPL-2.0
3#
4# Testing for potential kernel soft lockup during IPv6 routing table
5# refresh under heavy outgoing IPv6 traffic. If a kernel soft lockup
6# occurs, a kernel panic will be triggered to prevent associated issues.
7#
8#
9# Test Environment Layout
10#
11# ┌----------------┐ ┌----------------┐
12# | SOURCE_NS | | SINK_NS |
13# | NAMESPACE | | NAMESPACE |
14# |(iperf3 clients)| |(iperf3 servers)|
15# | | | |
16# | | | |
17# | ┌-----------| nexthops |---------┐ |
18# | |veth_source|<--------------------------------------->|veth_sink|<┐ |
19# | └-----------|2001:0DB8:1::0:1/96 2001:0DB8:1::1:1/96 |---------┘ | |
20# | | ^ 2001:0DB8:1::1:2/96 | | |
21# | | . . | fwd | |
22# | ┌---------┐ | . . | | |
23# | | IPv6 | | . . | V |
24# | | routing | | . 2001:0DB8:1::1:80/96| ┌-----┐ |
25# | | table | | . | | lo | |
26# | | nexthop | | . └--------┴-----┴-┘
27# | | update | | ............................> 2001:0DB8:2::1:1/128
28# | └-------- ┘ |
29# └----------------┘
30#
31# The test script sets up two network namespaces, source_ns and sink_ns,
32# connected via a veth link. Within source_ns, it continuously updates the
33# IPv6 routing table by flushing and inserting IPV6_NEXTHOP_ADDR_COUNT nexthop
34# IPs destined for SINK_LOOPBACK_IP_ADDR in sink_ns. This refresh occurs at a
35# rate of 1/ROUTING_TABLE_REFRESH_PERIOD per second for TEST_DURATION seconds.
36#
37# Simultaneously, multiple iperf3 clients within source_ns generate heavy
38# outgoing IPv6 traffic. Each client is assigned a unique port number starting
39# at 5000 and incrementing sequentially. Each client targets a unique iperf3
40# server running in sink_ns, connected to the SINK_LOOPBACK_IFACE interface
41# using the same port number.
42#
43# The number of iperf3 servers and clients is set to half of the total
44# available cores on each machine.
45#
46# NOTE: We have tested this script on machines with various CPU specifications,
47# ranging from lower to higher performance as listed below. The test script
48# effectively triggered a kernel soft lockup on machines running an unpatched
49# kernel in under a minute:
50#
51# - 1x Intel Xeon E-2278G 8-Core Processor @ 3.40GHz
52# - 1x Intel Xeon E-2378G Processor 8-Core @ 2.80GHz
53# - 1x AMD EPYC 7401P 24-Core Processor @ 2.00GHz
54# - 1x AMD EPYC 7402P 24-Core Processor @ 2.80GHz
55# - 2x Intel Xeon Gold 5120 14-Core Processor @ 2.20GHz
56# - 1x Ampere Altra Q80-30 80-Core Processor @ 3.00GHz
57# - 2x Intel Xeon Gold 5120 14-Core Processor @ 2.20GHz
58# - 2x Intel Xeon Silver 4214 24-Core Processor @ 2.20GHz
59# - 1x AMD EPYC 7502P 32-Core @ 2.50GHz
60# - 1x Intel Xeon Gold 6314U 32-Core Processor @ 2.30GHz
61# - 2x Intel Xeon Gold 6338 32-Core Processor @ 2.00GHz
62#
63# On less performant machines, you may need to increase the TEST_DURATION
64# parameter to enhance the likelihood of encountering a race condition leading
65# to a kernel soft lockup and avoid a false negative result.
66#
67# NOTE: The test may not produce the expected result in virtualized
68# environments (e.g., qemu) due to differences in timing and CPU handling,
69# which can affect the conditions needed to trigger a soft lockup.
70
71source lib.sh
72
73TEST_DURATION=300
74ROUTING_TABLE_REFRESH_PERIOD=0.01
75
76IPERF3_BITRATE="300m"
77
78
79IPV6_NEXTHOP_ADDR_COUNT="128"
80IPV6_NEXTHOP_ADDR_MASK="96"
81IPV6_NEXTHOP_PREFIX="2001:0DB8:1"
82
83
84SOURCE_TEST_IFACE="veth_source"
85SOURCE_TEST_IP_ADDR="2001:0DB8:1::0:1/96"
86
87SINK_TEST_IFACE="veth_sink"
88# ${SINK_TEST_IFACE} is populated with the following range of IPv6 addresses:
89# 2001:0DB8:1::1:1 to 2001:0DB8:1::1:${IPV6_NEXTHOP_ADDR_COUNT}
90SINK_LOOPBACK_IFACE="lo"
91SINK_LOOPBACK_IP_MASK="128"
92SINK_LOOPBACK_IP_ADDR="2001:0DB8:2::1:1"
93
94nexthop_ip_list=""
95termination_signal=""
96kernel_softlokup_panic_prev_val=""
97
98terminate_ns_processes_by_pattern() {
99 local ns=$1
100 local pattern=$2
101
102 for pid in $(ip netns pids ${ns}); do
103 [ -e /proc/$pid/cmdline ] && grep -qe "${pattern}" /proc/$pid/cmdline && kill -9 $pid
104 done
105}
106
107cleanup() {
108 echo "info: cleaning up namespaces and terminating all processes within them..."
109
110
111 # Terminate iperf3 instances running in the source_ns. To avoid race
112 # conditions, first iterate over the PIDs and terminate those
113 # associated with the bash shells running the
114 # `while true; do iperf3 -c ...; done` loops. In a second iteration,
115 # terminate the individual `iperf3 -c ...` instances.
116 terminate_ns_processes_by_pattern ${source_ns} while
117 terminate_ns_processes_by_pattern ${source_ns} iperf3
118
119 # Repeat the same process for sink_ns
120 terminate_ns_processes_by_pattern ${sink_ns} while
121 terminate_ns_processes_by_pattern ${sink_ns} iperf3
122
123 # Check if any iperf3 instances are still running. This could happen
124 # if a core has entered an infinite loop and the timeout for detecting
125 # the soft lockup has not expired, but either the test interval has
126 # already elapsed or the test was terminated manually (e.g., with ^C)
127 for pid in $(ip netns pids ${source_ns}); do
128 if [ -e /proc/$pid/cmdline ] && grep -qe 'iperf3' /proc/$pid/cmdline; then
129 echo "FAIL: unable to terminate some iperf3 instances. Soft lockup is underway. A kernel panic is on the way!"
130 exit ${ksft_fail}
131 fi
132 done
133
134 if [ "$termination_signal" == "SIGINT" ]; then
135 echo "SKIP: Termination due to ^C (SIGINT)"
136 elif [ "$termination_signal" == "SIGALRM" ]; then
137 echo "PASS: No kernel soft lockup occurred during this ${TEST_DURATION} second test"
138 fi
139
140 cleanup_ns ${source_ns} ${sink_ns}
141
142 sysctl -qw kernel.softlockup_panic=${kernel_softlokup_panic_prev_val}
143}
144
145setup_prepare() {
146 setup_ns source_ns sink_ns
147
148 ip -n ${source_ns} link add name ${SOURCE_TEST_IFACE} type veth peer name ${SINK_TEST_IFACE} netns ${sink_ns}
149
150 # Setting up the Source namespace
151 ip -n ${source_ns} addr add ${SOURCE_TEST_IP_ADDR} dev ${SOURCE_TEST_IFACE}
152 ip -n ${source_ns} link set dev ${SOURCE_TEST_IFACE} qlen 10000
153 ip -n ${source_ns} link set dev ${SOURCE_TEST_IFACE} up
154 ip netns exec ${source_ns} sysctl -qw net.ipv6.fib_multipath_hash_policy=1
155
156 # Setting up the Sink namespace
157 ip -n ${sink_ns} addr add ${SINK_LOOPBACK_IP_ADDR}/${SINK_LOOPBACK_IP_MASK} dev ${SINK_LOOPBACK_IFACE}
158 ip -n ${sink_ns} link set dev ${SINK_LOOPBACK_IFACE} up
159 ip netns exec ${sink_ns} sysctl -qw net.ipv6.conf.${SINK_LOOPBACK_IFACE}.forwarding=1
160
161 ip -n ${sink_ns} link set ${SINK_TEST_IFACE} up
162 ip netns exec ${sink_ns} sysctl -qw net.ipv6.conf.${SINK_TEST_IFACE}.forwarding=1
163
164
165 # Populate nexthop IPv6 addresses on the test interface in the sink_ns
166 echo "info: populating ${IPV6_NEXTHOP_ADDR_COUNT} IPv6 addresses on the ${SINK_TEST_IFACE} interface ..."
167 for IP in $(seq 1 ${IPV6_NEXTHOP_ADDR_COUNT}); do
168 ip -n ${sink_ns} addr add ${IPV6_NEXTHOP_PREFIX}::$(printf "1:%x" "${IP}")/${IPV6_NEXTHOP_ADDR_MASK} dev ${SINK_TEST_IFACE};
169 done
170
171 # Preparing list of nexthops
172 for IP in $(seq 1 ${IPV6_NEXTHOP_ADDR_COUNT}); do
173 nexthop_ip_list=$nexthop_ip_list" nexthop via ${IPV6_NEXTHOP_PREFIX}::$(printf "1:%x" $IP) dev ${SOURCE_TEST_IFACE} weight 1"
174 done
175}
176
177
178test_soft_lockup_during_routing_table_refresh() {
179 # Start num_of_iperf_servers iperf3 servers in the sink_ns namespace,
180 # each listening on ports starting at 5001 and incrementing
181 # sequentially. Since iperf3 instances may terminate unexpectedly, a
182 # while loop is used to automatically restart them in such cases.
183 echo "info: starting ${num_of_iperf_servers} iperf3 servers in the sink_ns namespace ..."
184 for i in $(seq 1 ${num_of_iperf_servers}); do
185 cmd="iperf3 --bind ${SINK_LOOPBACK_IP_ADDR} -s -p $(printf '5%03d' ${i}) --rcv-timeout 200 &>/dev/null"
186 ip netns exec ${sink_ns} bash -c "while true; do ${cmd}; done &" &>/dev/null
187 done
188
189 # Wait for the iperf3 servers to be ready
190 for i in $(seq ${num_of_iperf_servers}); do
191 port=$(printf '5%03d' ${i});
192 wait_local_port_listen ${sink_ns} ${port} tcp
193 done
194
195 # Continuously refresh the routing table in the background within
196 # the source_ns namespace
197 ip netns exec ${source_ns} bash -c "
198 while \$(ip netns list | grep -q ${source_ns}); do
199 ip -6 route add ${SINK_LOOPBACK_IP_ADDR}/${SINK_LOOPBACK_IP_MASK} ${nexthop_ip_list};
200 sleep ${ROUTING_TABLE_REFRESH_PERIOD};
201 ip -6 route delete ${SINK_LOOPBACK_IP_ADDR}/${SINK_LOOPBACK_IP_MASK};
202 done &"
203
204 # Start num_of_iperf_servers iperf3 clients in the source_ns namespace,
205 # each sending TCP traffic on sequential ports starting at 5001.
206 # Since iperf3 instances may terminate unexpectedly (e.g., if the route
207 # to the server is deleted in the background during a route refresh), a
208 # while loop is used to automatically restart them in such cases.
209 echo "info: starting ${num_of_iperf_servers} iperf3 clients in the source_ns namespace ..."
210 for i in $(seq 1 ${num_of_iperf_servers}); do
211 cmd="iperf3 -c ${SINK_LOOPBACK_IP_ADDR} -p $(printf '5%03d' ${i}) --length 64 --bitrate ${IPERF3_BITRATE} -t 0 --connect-timeout 150 &>/dev/null"
212 ip netns exec ${source_ns} bash -c "while true; do ${cmd}; done &" &>/dev/null
213 done
214
215 echo "info: IPv6 routing table is being updated at the rate of $(echo "1/${ROUTING_TABLE_REFRESH_PERIOD}" | bc)/s for ${TEST_DURATION} seconds ..."
216 echo "info: A kernel soft lockup, if detected, results in a kernel panic!"
217
218 wait
219}
220
221# Make sure 'iperf3' is installed, skip the test otherwise
222if [ ! -x "$(command -v "iperf3")" ]; then
223 echo "SKIP: 'iperf3' is not installed. Skipping the test."
224 exit ${ksft_skip}
225fi
226
227# Determine the number of cores on the machine
228num_of_iperf_servers=$(( $(nproc)/2 ))
229
230# Check if we are running on a multi-core machine, skip the test otherwise
231if [ "${num_of_iperf_servers}" -eq 0 ]; then
232 echo "SKIP: This test is not valid on a single core machine!"
233 exit ${ksft_skip}
234fi
235
236# Since the kernel soft lockup we're testing causes at least one core to enter
237# an infinite loop, destabilizing the host and likely affecting subsequent
238# tests, we trigger a kernel panic instead of reporting a failure and
239# continuing
240kernel_softlokup_panic_prev_val=$(sysctl -n kernel.softlockup_panic)
241sysctl -qw kernel.softlockup_panic=1
242
243handle_sigint() {
244 termination_signal="SIGINT"
245 cleanup
246 exit ${ksft_skip}
247}
248
249handle_sigalrm() {
250 termination_signal="SIGALRM"
251 cleanup
252 exit ${ksft_pass}
253}
254
255trap handle_sigint SIGINT
256trap handle_sigalrm SIGALRM
257
258(sleep ${TEST_DURATION} && kill -s SIGALRM $$)&
259
260setup_prepare
261test_soft_lockup_during_routing_table_refresh