tests: Add regression test for #16197 to ospf6_ecmp_inter_area topotest

The new test_multipath_inter_area() function reliably checks for #16197 and
will fail until it is fixed.

Signed-off-by: Martin Buck <mb-tmp-tvguho.pbz@gromit.dyndns.org>

tests/topotests/ospf6_ecmp_inter_area/r1/show_ipv6_routes_ospf6-1.json

@@ -108,6 +108,23 @@
       ]
     }
   ],
+  "2001:db8:9::/64": [
+    {
+      "internalNextHopActiveNum": 2,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        },
+        {
+          "fib": true,
+          "interfaceName": "r1-eth1",
+          "active": true
+        }
+      ]
+    }
+  ],
   "2001:db8:8007::/64": [
     {
       "internalNextHopActiveNum": 3,
@@ -151,5 +168,22 @@
         }
       ]
     }
+  ],
+  "2001:db8:8009::/64": [
+    {
+      "internalNextHopActiveNum": 2,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        },
+        {
+          "fib": true,
+          "interfaceName": "r1-eth1",
+          "active": true
+        }
+      ]
+    }
   ]
 }

tests/topotests/ospf6_ecmp_inter_area/r1/show_ipv6_routes_ospf6-2.json

@@ -93,6 +93,18 @@
       ]
     }
   ],
+  "2001:db8:9::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
   "2001:db8:8007::/64": [
     {
       "internalNextHopActiveNum": 2,
@@ -126,5 +138,17 @@
         }
       ]
     }
+  ],
+  "2001:db8:8009::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
   ]
 }

tests/topotests/ospf6_ecmp_inter_area/r1/show_ipv6_routes_ospf6-3.json

@@ -83,6 +83,18 @@
       ]
     }
   ],
+  "2001:db8:9::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
   "2001:db8:8007::/64": [
     {
       "internalNextHopActiveNum": 1,
@@ -106,5 +118,17 @@
         }
       ]
     }
+  ],
+  "2001:db8:8009::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
   ]
 }

tests/topotests/ospf6_ecmp_inter_area/r1/show_ipv6_routes_ospf6-4.json

@@ -0,0 +1,98 @@
+{
+  "2001:db8:2::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:4::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:5::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:6::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:7::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:9::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:8007::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:8009::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ]
+}

tests/topotests/ospf6_ecmp_inter_area/r1/show_ipv6_routes_ospf6-5.json

@@ -0,0 +1,108 @@
+{
+  "2001:db8:2::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:4::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:5::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:6::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:7::/64": [
+    {
+      "internalNextHopActiveNum": 2,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        },
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:9::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:8007::/64": [
+    {
+      "internalNextHopActiveNum": 2,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth0",
+          "active": true
+        },
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ],
+  "2001:db8:8009::/64": [
+    {
+      "internalNextHopActiveNum": 1,
+      "nexthops": [
+        {
+          "fib": true,
+          "interfaceName": "r1-eth2",
+          "active": true
+        }
+      ]
+    }
+  ]
+}

tests/topotests/ospf6_ecmp_inter_area/r6/frr.conf

@@ -25,6 +25,11 @@ interface r6-eth3
  ipv6 ospf6 hello-interval 2
  ipv6 ospf6 dead-interval 10
 !
+interface r6-eth4
+ ipv6 ospf6 area 1
+ ipv6 ospf6 hello-interval 2
+ ipv6 ospf6 dead-interval 10
+!
 router ospf6
  ospf6 router-id 10.254.254.6
  redistribute connected

tests/topotests/ospf6_ecmp_inter_area/r9/frr.conf

@@ -0,0 +1,22 @@
+hostname r9
+!
+ipv6 forwarding
+!
+interface lo
+ ipv6 address 2001:db8:9::1/64
+!
+interface r9-eth0
+ ipv6 ospf6 area 1
+ ipv6 ospf6 hello-interval 2
+ ipv6 ospf6 dead-interval 10
+!
+interface r9-eth1
+ ipv6 address 2001:db8:8009::1/64
+ ipv6 ospf6 area 1
+ ipv6 ospf6 hello-interval 2
+ ipv6 ospf6 dead-interval 10
+!
+router ospf6
+ ospf6 router-id 10.254.254.9
+ redistribute connected
+!

tests/topotests/ospf6_ecmp_inter_area/test_ospf6_ecmp_inter_area.py

@@ -3,7 +3,7 @@
 
 # test_ospf6_ecmp_inter_area.py
 #
-# Copyright (c) 2021, 2022, 2024 by Martin Buck
+# Copyright (c) 2021, 2022, 2024, 2025 by Martin Buck
 # Copyright (c) 2016 by
 # Network Device Education Foundation, Inc. ("NetDEF")
 #
@@ -20,33 +20,52 @@ without ospf6d having to do anything.
 
 Useful as a regression test for #9720 and #15777.
 
+Also checks summary LSA origination/updates in case of topology changes in
+remote areas via route nexthop checks.
+
+Useful as a regression test for #16197.
+
 Topology:
                    .
             Area 0 . Area 1
                    .
-    -- R2 ------ R5 -----
+     -- R2 ------ R5 ---
-   /              .\     \
+    /            / .    \
-  /               . |     \
+   /           R8  .     R7
-R1 --- R3 ------ R6 ------ R7
+  /              \ .    /
-  \            / |. |
+R1 ---- R3 ------ R6 ---
-   \          /  |. |
+  \              / .\
-    -- R4 ----   |. |
+   \            /  . \
-                / ./
+    \          /   .  \
-              R8 --
+     -- R4 ----    .   R9
                    .
 
-We check routes on R1, primarily those towards R7/8. Those to R7 are
+We check routes on R1, primarily those towards R7/8/9. Those to R7/9 are
 inter-area routes with R5/6 being ABRs, those to R8 are intra-area routes
-and are used for reference. R7/R8 announce one internal and one external
+and are used for reference. R7/8/9 announce one internal and one external
-route each.
+route each. With all links up, we expect 3 ECMP paths and 3 nexthops on R1
+towards R7/8 and 2 ECMP paths/nexthops towards R9.
 
-With all links up, we expect 3 ECMP paths and 3 nexthops on R1 towards each
+Then we bring down the R3-R6 link, causing only 2 remaining paths and 2
-of R7/8. Then we bring down the R3-R6 link, causing only 2 remaining
+nexthops on R1 towards R7/8 and 1 towards R9. Then we bring down the R2-R5
-paths and 2 nexthops on R1. Then we bring down the R2-R5 link, causing only
+link, causing only 1 remaining path and 1 nexthop towards R7/8/9 on R1.
-1 remaining path and 1 nexthop on R1.
 
 The test is successful if the number of nexthops and their interfaces for
 the routes on R1 is as expected.
+
+
+To check summary LSA origination after topology changes, we start again with
+the original topology and disconnect R3 and R8 from it to simplify it and to
+avoid unwanted shortcuts (LSAs between R5 and R6 via area 0 should travel
+via R2/1/4 and not take the shortcut via R8). We also bring down the R6-R7
+link initially so R5 and R6 can't exchange their area 1 LSAs. Initially, we
+expect 1 path/nexthop on R1 towards R7 (via R2) and R9 (via R4).
+
+Then we bring up the R6-R7 link, causing 2 paths/nexthops on R1 towards R7
+(via R2 and R4) and still 1 path/nexthop towards R9 (still via R4). With
+#16197, we would see 1 path/nexthop towards R9 but via R2 instead of R4,
+because R6 doesn't re-originate the summary LSAs towards area 0 properly
+after the topology change.
 """
 
 import json
@@ -73,8 +92,8 @@ pytestmark = [pytest.mark.ospf6d]
 def build_topo(tgen):
     "Build function"
 
-    # Create 8 routers
+    # Create 9 routers
-    for routern in range(1, 9):
+    for routern in range(1, 10):
         tgen.add_router("r{}".format(routern))
     tgen.gears["r1"].add_link(tgen.gears["r2"])
     tgen.gears["r1"].add_link(tgen.gears["r3"])
@@ -86,11 +105,13 @@ def build_topo(tgen):
     tgen.gears["r5"].add_link(tgen.gears["r8"])
     tgen.gears["r6"].add_link(tgen.gears["r7"])
     tgen.gears["r6"].add_link(tgen.gears["r8"])
+    tgen.gears["r6"].add_link(tgen.gears["r9"])
     # Additional "loopback" interfaces. Not used for communication, just to
     # hold an address we use to inject intra-/inter-area routes (the one on
     # the real "lo" loopback is used for external routes).
     tgen.gears["r7"].add_link(tgen.gears["r7"])
     tgen.gears["r8"].add_link(tgen.gears["r8"])
+    tgen.gears["r9"].add_link(tgen.gears["r9"])
 
 
 def setup_module(mod):
@@ -200,6 +221,46 @@ def test_ecmp_inter_area(request):
 
     expect_routes_json("r1", "show_ipv6_routes_ospf6-3.json", "post-R2-R5-link-down")
 
+    step("restoring links R2-R5/R3-R6")
+    tgen.gears["r3"].run("ip link set r3-eth1 up")
+    tgen.gears["r2"].run("ip link set r2-eth1 up")
+
+    expect_routes_json(
+        "r1", "show_ipv6_routes_ospf6-1.json", "post-R2-R5/R3-R6-link-up"
+    )
+
+    write_test_footer(tc_name)
+
+
+def test_multipath_inter_area(request):
+    """
+    Test OSPFv3 routes with (non-equal) multipath and topology changes in
+    non-backbone area requiring summary LSA updates
+    """
+    tc_name = request.node.name
+    write_test_header(tc_name)
+
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    step("links R1-R3/R3-R6/R5-R8/R6-R8 down (simplify topology, disconnect R3/R8)")
+    tgen.gears["r3"].run("ip link set r3-eth0 down")
+    tgen.gears["r3"].run("ip link set r3-eth1 down")
+    tgen.gears["r8"].run("ip link set r8-eth0 down")
+    tgen.gears["r8"].run("ip link set r8-eth1 down")
+    step("link R6-R7 down (initial summary LSAs)")
+    tgen.gears["r6"].run("ip link set r6-eth2 down")
+
+    expect_routes_json(
+        "r1", "show_ipv6_routes_ospf6-4.json", "post-R3-R6/R6-R7-link-down"
+    )
+
+    step("triggering R6-R7 link up")
+    tgen.gears["r6"].run("ip link set r6-eth2 up")
+
+    expect_routes_json("r1", "show_ipv6_routes_ospf6-5.json", "post-R6-R7-link-up")
+
     write_test_footer(tc_name)