FYI, we noticed the following commit (built with gcc-7): commit: cc3a86c802f0ba9a2627aef256d95ae3b3fa6e91 ("ipv6: Change rt6_probe to take a fib6_nh") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master in testcase: hwsim with following parameters: group: hwsim-12 on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 4G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): 2019-05-11 15:54:02 ./run-tests.py proxyarp_open DEV: wlan0: 02:00:00:00:00:00 DEV: wlan1: 02:00:00:00:01:00 DEV: wlan2: 02:00:00:00:02:00 APDEV: wlan3 APDEV: wlan4 START proxyarp_open 1/1 Test: ProxyARP with open network Starting AP wlan3 Starting AP wlan4 Connect STA wlan0 to AP Connect STA wlan1 to AP Connect STA wlan2 to AP Bridge setup: bridge namebridge idSTP enabledinterfaces ap-br08000.020000000300nowlan3 wlan4 Bridge showstp: ap-br0 bridge id8000.020000000300 designated root8000.020000000300 root port 0path cost 0 max age 20.00bridge max age 20.00 hello time 2.00bridge hello time 2.00 forward delay 0.00bridge forward delay 0.00 ageing time 300.00 hello timer 0.00tcn timer 0.00 topology change timer 0.00gc timer 299.09 flags wlan3 (1) port id8001state forwarding designated root8000.020000000300path cost 100 designated bridge8000.020000000300message age timer 0.00 designated port8001forward delay timer 0.00 designated cost 0hold timer 0.00 flags hairpin mode 1 wlan4 (2) port id8002state forwarding designated root8000.020000000300path cost 100 designated bridge8000.020000000300message age timer 0.00 designated port8002forward delay timer 0.00 designated cost 0hold timer 0.00 flags After connect (showmacs): port nomac addris local?ageing timer 1 02:00:00:00:00:00no 0.51 1 02:00:00:00:01:00no 0.11 2 02:00:00:00:02:00no 0.13 1 02:00:00:00:03:00yes 0.00 1 02:00:00:00:03:00yes 0.00 2 02:00:00:00:04:00yes 0.00 2 02:00:00:00:04:00yes 0.00 After connect: ['192.168.1.123 dev ap-br0 lladdr 02:00:00:00:00:00 PERMANENT', 'fe80::ff:fe00:100 dev ap-br0 lladdr 02:00:00:00:01:00 PERMANENT'] Unexpected number of neighbor entries after connect Traceback (most recent call last): File "./run-tests.py", line 503, in main t(dev, apdev, params) File "/lkp/benchmarks/hwsim/tests/hwsim/test_ap_hs20.py", line 5197, in test_proxyarp_open _test_proxyarp_open(dev, apdev, params) File "/lkp/benchmarks/hwsim/tests/hwsim/test_ap_hs20.py", line 4777, in _test_proxyarp_open raise Exception("Unexpected number of neighbor entries after connect") Exception: Unexpected number of neighbor entries after connect FAIL proxyarp_open 1.5456 2019-05-11 15:54:04.617420 passed 0 test case(s) skipped 0 test case(s) failed tests: proxyarp_open 2019-05-11 15:54:04 ./run-tests.py proxyarp_open_ebtables DEV: wlan0: 02:00:00:00:00:00 DEV: wlan1: 02:00:00:00:01:00 DEV: wlan2: 02:00:00:00:02:00 APDEV: wlan3 APDEV: wlan4 START proxyarp_open_ebtables 1/1 Test: ProxyARP with open network Starting AP wlan3 Starting AP wlan4 Connect STA wlan0 to AP Connect STA wlan1 to AP Connect STA wlan2 to AP Bridge setup: bridge namebridge idSTP enabledinterfaces ap-br08000.020000000300nowlan3 wlan4 Bridge showstp: ap-br0 bridge id8000.020000000300 designated root8000.020000000300 root port 0path cost 0 max age 20.00bridge max age 20.00 hello time 2.00bridge hello time 2.00 forward delay 0.00bridge forward delay 0.00 ageing time 300.00 hello timer 0.00tcn timer 0.00 topology change timer 0.00gc timer 299.16 flags wlan3 (1) port id8001state forwarding designated root8000.020000000300path cost 100 designated bridge8000.020000000300message age timer 0.00 designated port8001forward delay timer 0.00 designated cost 0hold timer 0.00 flags hairpin mode 1 wlan4 (2) port id8002state forwarding designated root8000.020000000300path cost 100 designated bridge8000.020000000300message age timer 0.00 designated port8002forward delay timer 0.00 designated cost 0hold timer 0.00 flags After connect (showmacs): port nomac addris local?ageing timer 1 02:00:00:00:00:00no 0.28 1 02:00:00:00:01:00no 0.15 2 02:00:00:00:02:00no 0.03 1 02:00:00:00:03:00yes 0.00 1 02:00:00:00:03:00yes 0.00 2 02:00:00:00:04:00yes 0.00 2 02:00:00:00:04:00yes 0.00 After connect: ['192.168.1.123 dev ap-br0 lladdr 02:00:00:00:00:00 PERMANENT', 'fe80::ff:fe00:0 dev ap-br0 lladdr 02:00:00:00:00:00 PERMANENT'] Unexpected number of neighbor entries after connect Traceback (most recent call last): File "./run-tests.py", line 503, in main t(dev, apdev, params) File "/lkp/benchmarks/hwsim/tests/hwsim/test_ap_hs20.py", line 5217, in test_proxyarp_open_ebtables _test_proxyarp_open(dev, apdev, params, ebtables=True) File "/lkp/benchmarks/hwsim/tests/hwsim/test_ap_hs20.py", line 4777, in _test_proxyarp_open raise Exception("Unexpected number of neighbor entries after connect") Exception: Unexpected number of neighbor entries after connect FAIL proxyarp_open_ebtables 1.593676 2019-05-11 15:54:06.399407 passed 0 test case(s) skipped 0 test case(s) failed tests: proxyarp_open_ebtables If you fix the issue, kindly add following tag Reported-by: kernel test robot <rong.a.chen(a)intel.com&gt; To reproduce: # build kernel cd linux cp config-5.1.0-rc4-00620-gcc3a86c .config make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 olddefconfig make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 prepare make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 modules_prepare make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 SHELL=/bin/bash make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 bzImage git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email Thanks, Rong Chen