selftests: fib_nexthops: Test blackhole nexthops when loopback goes down

Test that blackhole nexthops are not flushed when the loopback device
goes down.

Output without previous patch:

 # ./fib_nexthops.sh -t basic

 Basic functional tests
 ----------------------
 TEST: List with nothing defined                                     [ OK ]
 TEST: Nexthop get on non-existent id                                [ OK ]
 TEST: Nexthop with no device or gateway                             [ OK ]
 TEST: Nexthop with down device                                      [ OK ]
 TEST: Nexthop with device that is linkdown                          [ OK ]
 TEST: Nexthop with device only                                      [ OK ]
 TEST: Nexthop with duplicate id                                     [ OK ]
 TEST: Blackhole nexthop                                             [ OK ]
 TEST: Blackhole nexthop with other attributes                       [ OK ]
 TEST: Blackhole nexthop with loopback device down                   [FAIL]
 TEST: Create group                                                  [ OK ]
 TEST: Create group with blackhole nexthop                           [FAIL]
 TEST: Create multipath group where 1 path is a blackhole            [ OK ]
 TEST: Multipath group can not have a member replaced by blackhole   [ OK ]
 TEST: Create group with non-existent nexthop                        [ OK ]
 TEST: Create group with same nexthop multiple times                 [ OK ]
 TEST: Replace nexthop with nexthop group                            [ OK ]
 TEST: Replace nexthop group with nexthop                            [ OK ]
 TEST: Nexthop group and device                                      [ OK ]
 TEST: Test proto flush                                              [ OK ]
 TEST: Nexthop group and blackhole                                   [ OK ]

 Tests passed:  19
 Tests failed:   2

Output with previous patch:

 # ./fib_nexthops.sh -t basic

 Basic functional tests
 ----------------------
 TEST: List with nothing defined                                     [ OK ]
 TEST: Nexthop get on non-existent id                                [ OK ]
 TEST: Nexthop with no device or gateway                             [ OK ]
 TEST: Nexthop with down device                                      [ OK ]
 TEST: Nexthop with device that is linkdown                          [ OK ]
 TEST: Nexthop with device only                                      [ OK ]
 TEST: Nexthop with duplicate id                                     [ OK ]
 TEST: Blackhole nexthop                                             [ OK ]
 TEST: Blackhole nexthop with other attributes                       [ OK ]
 TEST: Blackhole nexthop with loopback device down                   [ OK ]
 TEST: Create group                                                  [ OK ]
 TEST: Create group with blackhole nexthop                           [ OK ]
 TEST: Create multipath group where 1 path is a blackhole            [ OK ]
 TEST: Multipath group can not have a member replaced by blackhole   [ OK ]
 TEST: Create group with non-existent nexthop                        [ OK ]
 TEST: Create group with same nexthop multiple times                 [ OK ]
 TEST: Replace nexthop with nexthop group                            [ OK ]
 TEST: Replace nexthop group with nexthop                            [ OK ]
 TEST: Nexthop group and device                                      [ OK ]
 TEST: Test proto flush                                              [ OK ]
 TEST: Nexthop group and blackhole                                   [ OK ]

 Tests passed:  21
 Tests failed:   0
Signed-off-by: NIdo Schimmel <idosch@nvidia.com>
Reviewed-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tools/testing/selftests/net/fib_nexthops.sh

@@ -1524,6 +1524,14 @@ basic()
 	run_cmd "$IP nexthop replace id 2 blackhole dev veth1"
 	log_test $? 2 "Blackhole nexthop with other attributes"
 
+	# blackhole nexthop should not be affected by the state of the loopback
+	# device
+	run_cmd "$IP link set dev lo down"
+	check_nexthop "id 2" "id 2 blackhole"
+	log_test $? 0 "Blackhole nexthop with loopback device down"
+
+	run_cmd "$IP link set dev lo up"
+
 	#
 	# groups
 	#