tests: topotests/ospf_topo1: negative-path ietf-ospf YANG tests

Add five negative tests that exercise the VALIDATE-phase rejection paths
the config-write callbacks rely on:

- test_ospf_yang_negative_missing_instance: commits targeting a
  control-plane-protocol name that doesn't match an FRR ospf / ospf6
  instance must be rejected (resolve_instance helper).
- test_ospf_yang_negative_missing_interface: commits targeting an
  unknown interface name under areas/area/interfaces/interface must be
  rejected (resolve_interface helper; closes the leafref-relaxation
  hole).
- test_ospf_yang_negative_default_cost_on_normal_area: setting
  default-cost on the backbone area must be rejected (defence in depth
  alongside the YANG `when` clause).
- test_ospf_yang_negative_v3_unsupported_interface_type: setting
  ospf6 interface-type=non-broadcast must be rejected (ospf6d only
  accepts broadcast / point-to-point / point-to-multipoint).
- test_ospf_yang_area_delete_recreate_cleanup: a stub area with
  non-default summary and default-cost is deleted via the list-destroy
  path then recreated as a normal area; the previous per-leaf state
  must not survive.

The helper _mgmt_commit_attempt issues the candidate change, applies,
then aborts the candidate so the rejected entry doesn't survive into
the next test's commit attempt. Tests confirm rejection by checking
that the candidate value did NOT land in show running-config (more
robust than parsing libyang's error string, which varies by version).

Signed-off-by: Eric Parsonage <eric@eparsonage.com>

Author: lamestllama

tests/topotests/ospf_topo1/test_ospf_topo1.py

@@ -1182,6 +1182,213 @@ def test_ospf_yang_area_summary_default_cost_config():
     )
 
 
+def _mgmt_commit_attempt(router, set_cmd):
+    """Run a mgmt set-config + commit and return the vty output.
+
+    The caller verifies the rejection by confirming the candidate value
+    did NOT land in `show running-config` (more robust than parsing the
+    error string, which varies by libyang version). `mgmt commit abort`
+    follows the apply so a rejected candidate doesn't survive into the
+    next test's commit attempt.
+    """
+    return router.vtysh_cmd(
+        "configure terminal file-lock\n"
+        "{}\n"
+        "mgmt commit apply\n"
+        "mgmt commit abort".format(set_cmd),
+        isjson=False,
+    )
+
+
+def test_ospf_yang_negative_missing_instance():
+    """Reject YANG config that targets an OSPF instance the daemon doesn't have.
+
+    The branch's resolve_instance helper rejects at NB_EV_VALIDATE when no
+    FRR-side ospf / ospf6 instance matches the control-plane-protocol name
+    key. Confirm a commit against name='ghost' does not land.
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip("skipped because of router(s) failure")
+
+    r1 = tgen.gears["r1"]
+
+    ghost_v2 = (
+        "/ietf-routing:routing/control-plane-protocols/"
+        "control-plane-protocol[type='ietf-ospf:ospfv2'][name='ghost']/"
+        "ietf-ospf:ospf/explicit-router-id"
+    )
+    _mgmt_commit_attempt(
+        r1,
+        "mgmt set-config {} 9.9.9.9".format(ghost_v2),
+    )
+    # The default instance is unchanged; the ghost one was never created.
+    running = r1.vtysh_cmd("show running-config ospfd")
+    assert "router-id 9.9.9.9" not in running, (
+        "ghost router-id must not have landed, got:\n" + running
+    )
+
+    ghost_v3 = (
+        "/ietf-routing:routing/control-plane-protocols/"
+        "control-plane-protocol[type='ietf-ospf:ospfv3'][name='ghost']/"
+        "ietf-ospf:ospf/explicit-router-id"
+    )
+    _mgmt_commit_attempt(
+        r1,
+        "mgmt set-config {} 9.9.9.9".format(ghost_v3),
+    )
+    running = r1.vtysh_cmd("show running-config ospf6d")
+    assert "router-id 9.9.9.9" not in running, (
+        "ghost ospf6 router-id must not have landed, got:\n" + running
+    )
+
+
+def test_ospf_yang_negative_missing_interface():
+    """Reject per-interface YANG config that names a non-existent interface.
+
+    frr-deviations-ietf-routing-ospf relaxes the RFC 9129 interface-name
+    leafref, so libyang no longer rejects names that aren't in
+    /ietf-interfaces. The branch's resolve_interface helper restores that
+    rejection inside the callback at NB_EV_VALIDATE.
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip("skipped because of router(s) failure")
+
+    r1 = tgen.gears["r1"]
+
+    bogus_v2 = (
+        _yang_area_xpath("ietf-ospf:ospfv2", "0.0.0.0")
+        + "/interfaces/interface[name='r1-eth42']/cost"
+    )
+    _mgmt_commit_attempt(
+        r1,
+        "mgmt set-config {} 7".format(bogus_v2),
+    )
+    running = r1.vtysh_cmd("show running-config ospfd")
+    assert "r1-eth42" not in running, (
+        "interface r1-eth42 must not appear in running-config, got:\n" + running
+    )
+
+    bogus_v3 = (
+        _yang_area_xpath("ietf-ospf:ospfv3", "0.0.0.0")
+        + "/interfaces/interface[name='r1-eth42']/cost"
+    )
+    _mgmt_commit_attempt(
+        r1,
+        "mgmt set-config {} 7".format(bogus_v3),
+    )
+    running = r1.vtysh_cmd("show running-config ospf6d")
+    assert "r1-eth42" not in running, (
+        "interface r1-eth42 must not appear in v3 running-config, got:\n" + running
+    )
+
+
+def test_ospf_yang_negative_default_cost_on_normal_area():
+    """Reject default-cost on a non-stub / non-NSSA area.
+
+    RFC 9129's `when` clause restricts default-cost to stub or NSSA areas;
+    the callback also rejects at VALIDATE as a defence-in-depth measure.
+    Area 0 is the backbone (normal); setting default-cost on it must fail.
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip("skipped because of router(s) failure")
+
+    r1 = tgen.gears["r1"]
+
+    area_path = _yang_area_xpath("ietf-ospf:ospfv2", "0.0.0.0")
+    _mgmt_commit_attempt(
+        r1,
+        "mgmt set-config {}/default-cost 99".format(area_path),
+    )
+    running = r1.vtysh_cmd("show running-config ospfd")
+    assert "default-cost 99" not in running, (
+        "default-cost 99 must not appear on the backbone area, got:\n" + running
+    )
+
+
+def test_ospf_yang_negative_v3_unsupported_interface_type():
+    """Reject ospf6 interface-type enum values that ospf6d doesn't accept.
+
+    RFC 9129 declares non-broadcast and hybrid; ospf6d only supports
+    broadcast, point-to-point and point-to-multipoint. The callback must
+    reject the unsupported enum values at VALIDATE.
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip("skipped because of router(s) failure")
+
+    r1 = tgen.gears["r1"]
+
+    iface_v3 = (
+        _yang_area_xpath("ietf-ospf:ospfv3", "0.0.0.0")
+        + "/interfaces/interface[name='r1-eth1']"
+    )
+    _mgmt_commit_attempt(
+        r1,
+        "mgmt set-config {}/interface-type non-broadcast".format(iface_v3),
+    )
+    running = r1.vtysh_cmd("show running-config ospf6d")
+    assert "non-broadcast" not in running, (
+        "unsupported interface-type must not appear in v3 running-config, "
+        "got:\n" + running
+    )
+
+
+def test_ospf_yang_area_delete_recreate_cleanup():
+    """Delete then recreate an area; per-leaf state must reset cleanly.
+
+    Sets a non-default summary and default-cost on a stub area, then deletes
+    the area via the list-destroy path, then recreates it as a normal area,
+    and confirms the previous stub / default-cost state is gone. Catches
+    regressions where destroy callbacks leave stale per-leaf state.
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip("skipped because of router(s) failure")
+
+    r1 = tgen.gears["r1"]
+    area_path = _yang_area_xpath("ietf-ospf:ospfv2", "0.0.0.51")
+
+    # Set area-type=stub + summary=false + default-cost=77 in one commit.
+    # libyang materialises the area list entry implicitly when a child leaf
+    # is set; no separate list-create step is needed.
+    r1.vtysh_cmd(
+        "configure terminal file-lock\n"
+        "mgmt set-config {}/area-type stub-area\n"
+        "mgmt set-config {}/summary false\n"
+        "mgmt set-config {}/default-cost 77\n"
+        "mgmt commit apply".format(area_path, area_path, area_path)
+    )
+    running = r1.vtysh_cmd("show running-config ospfd")
+    assert "area 0.0.0.51 stub no-summary" in running, running
+    assert "area 0.0.0.51 default-cost 77" in running, running
+
+    _clear_yang_area(r1, "ietf-ospf:ospfv2", "0.0.0.51")
+    running = r1.vtysh_cmd("show running-config ospfd")
+    assert "0.0.0.51" not in running, (
+        "area 0.0.0.51 must be gone after delete, got:\n" + running
+    )
+
+    # Recreate by setting only area-type=normal-area; previous stub /
+    # default-cost must not bleed through.
+    r1.vtysh_cmd(
+        "configure terminal file-lock\n"
+        "mgmt set-config {}/area-type normal-area\n"
+        "mgmt commit apply".format(area_path)
+    )
+    running = r1.vtysh_cmd("show running-config ospfd")
+    assert "area 0.0.0.51 stub" not in running, (
+        "stub setting must not survive delete + recreate, got:\n" + running
+    )
+    assert "area 0.0.0.51 default-cost" not in running, (
+        "default-cost must not survive delete + recreate, got:\n" + running
+    )
+
+    _clear_yang_area(r1, "ietf-ospf:ospfv2", "0.0.0.51")
+
+
 def test_ospf_convergence():
     "Test OSPF daemon convergence"
     tgen = get_topogen()