From: Hangbin Liu <liuhangbin@xxxxxxxxx> commit bbe4c0896d25009a7c86285d2ab024eed4374eea upstream. Some distros may enable rp_filter by default. After ns1 change addr to 10.0.2.99 and set default router to 10.0.2.1, while the connected router address is still 10.0.1.1. The router will not reply the arp request from ns1. Fix it by setting the router's veth0 rp_filter to 0. Before the fix: # ./nft_fib.sh PASS: fib expression did not cause unwanted packet drops Netns nsrouter-HQkDORO2 fib counter doesn't match expected packet count of 1 for 1.1.1.1 table inet filter { chain prerouting { type filter hook prerouting priority filter; policy accept; ip daddr 1.1.1.1 fib saddr . iif oif missing counter packets 0 bytes 0 drop ip6 daddr 1c3::c01d fib saddr . iif oif missing counter packets 0 bytes 0 drop } } After the fix: # ./nft_fib.sh PASS: fib expression did not cause unwanted packet drops PASS: fib expression did drop packets for 1.1.1.1 PASS: fib expression did drop packets for 1c3::c01d Fixes: 82944421243e ("selftests: netfilter: add fib test case") Signed-off-by: Yi Chen <yiche@xxxxxxxxxx> Signed-off-by: Hangbin Liu <liuhangbin@xxxxxxxxx> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- tools/testing/selftests/netfilter/nft_fib.sh | 1 + 1 file changed, 1 insertion(+) --- a/tools/testing/selftests/netfilter/nft_fib.sh +++ b/tools/testing/selftests/netfilter/nft_fib.sh @@ -174,6 +174,7 @@ test_ping() { ip netns exec ${nsrouter} sysctl net.ipv6.conf.all.forwarding=1 > /dev/null ip netns exec ${nsrouter} sysctl net.ipv4.conf.veth0.forwarding=1 > /dev/null ip netns exec ${nsrouter} sysctl net.ipv4.conf.veth1.forwarding=1 > /dev/null +ip netns exec ${nsrouter} sysctl net.ipv4.conf.veth0.rp_filter=0 > /dev/null sleep 3 Patches currently in stable-queue which might be from liuhangbin@xxxxxxxxx are queue-5.15/selftests-netfilter-disable-rp_filter-on-router.patch queue-5.15/selftests-netfilter-fix-exit-value-for-nft_concat_range.patch