selftests: net: fib_nexthops: add test for group refcount imbalance bug

The new selftest runs a sequence which causes circular refcount
dependency between deleted objects which cannot be released and results
in a netdevice refcount imbalance.

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/tools/testing/selftests/net/fib_nexthops.sh b/tools/testing/selftests/net/fib_nexthops.sh
index b5a69ad..d444ee6 100755 (executable)
--- a/tools/testing/selftests/net/fib_nexthops.sh
+++ b/tools/testing/selftests/net/fib_nexthops.sh
@@ -629,6 +629,66 @@ ipv6_fcnal()
        log_test $? 0 "Nexthops removed on admin down"
 }
 
+ipv6_grp_refs()
+{
+       if [ ! -x "$(command -v mausezahn)" ]; then
+               echo "SKIP: Could not run test; need mausezahn tool"
+               return
+       fi
+
+       run_cmd "$IP link set dev veth1 up"
+       run_cmd "$IP link add veth1.10 link veth1 up type vlan id 10"
+       run_cmd "$IP link add veth1.20 link veth1 up type vlan id 20"
+       run_cmd "$IP -6 addr add 2001:db8:91::1/64 dev veth1.10"
+       run_cmd "$IP -6 addr add 2001:db8:92::1/64 dev veth1.20"
+       run_cmd "$IP -6 neigh add 2001:db8:91::2 lladdr 00:11:22:33:44:55 dev veth1.10"
+       run_cmd "$IP -6 neigh add 2001:db8:92::2 lladdr 00:11:22:33:44:55 dev veth1.20"
+       run_cmd "$IP nexthop add id 100 via 2001:db8:91::2 dev veth1.10"
+       run_cmd "$IP nexthop add id 101 via 2001:db8:92::2 dev veth1.20"
+       run_cmd "$IP nexthop add id 102 group 100"
+       run_cmd "$IP route add 2001:db8:101::1/128 nhid 102"
+
+       # create per-cpu dsts through nh 100
+       run_cmd "ip netns exec me mausezahn -6 veth1.10 -B 2001:db8:101::1 -A 2001:db8:91::1 -c 5 -t tcp "dp=1-1023, flags=syn" >/dev/null 2>&1"
+
+       # remove nh 100 from the group to delete the route potentially leaving
+       # a stale per-cpu dst which holds a reference to the nexthop's net
+       # device and to the IPv6 route
+       run_cmd "$IP nexthop replace id 102 group 101"
+       run_cmd "$IP route del 2001:db8:101::1/128"
+
+       # add both nexthops to the group so a reference is taken on them
+       run_cmd "$IP nexthop replace id 102 group 100/101"
+
+       # if the bug described in commit "net: nexthop: release IPv6 per-cpu
+       # dsts when replacing a nexthop group" exists at this point we have
+       # an unlinked IPv6 route (but not freed due to stale dst) with a
+       # reference over the group so we delete the group which will again
+       # only unlink it due to the route reference
+       run_cmd "$IP nexthop del id 102"
+
+       # delete the nexthop with stale dst, since we have an unlinked
+       # group with a ref to it and an unlinked IPv6 route with ref to the
+       # group, the nh will only be unlinked and not freed so the stale dst
+       # remains forever and we get a net device refcount imbalance
+       run_cmd "$IP nexthop del id 100"
+
+       # if a reference was lost this command will hang because the net device
+       # cannot be removed
+       timeout -s KILL 5 ip netns exec me ip link del veth1.10 >/dev/null 2>&1
+
+       # we can't cleanup if the command is hung trying to delete the netdev
+       if [ $? -eq 137 ]; then
+               return 1
+       fi
+
+       # cleanup
+       run_cmd "$IP link del veth1.20"
+       run_cmd "$IP nexthop flush"
+
+       return 0
+}
+
 ipv6_grp_fcnal()
 {
        local rc
@@ -734,6 +794,9 @@ ipv6_grp_fcnal()
 
        run_cmd "$IP nexthop add id 108 group 31/24"
        log_test $? 2 "Nexthop group can not have a blackhole and another nexthop"
+
+       ipv6_grp_refs
+       log_test $? 0 "Nexthop group replace refcounts"
 }
 
 ipv6_res_grp_fcnal()