selftests: net: add a test case for nsid in all nsid notifications

The test subscribes to link events from all namespaces and makes
sure that local events do not carry NSID in their ancillary data
(even if there is a self-referential NSID allocated for the local
namespace), and remote events do.

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://patch.msgid.link/20260520172317.175168-5-i.maximets@ovn.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 59 insertions, 2 deletions

diff --git a/tools/testing/selftests/net/link_netns.py b/tools/testing/selftests/net/link_netns.py
index aab043c59d69..6d1f863b6262 100755
--- a/tools/testing/selftests/net/link_netns.py
+++ b/tools/testing/selftests/net/link_netns.py
@@ -3,13 +3,14 @@
 
 import time
 
-from lib.py import ksft_run, ksft_exit, ksft_true
+from lib.py import ksft_run, ksft_exit, ksft_eq, ksft_true
 from lib.py import ip
 from lib.py import NetNS, NetNSEnter
 from lib.py import RtnlFamily
 
 
 LINK_NETNSID = 100
+LINK_NETNSID2 = 200
 
 
 def test_event() -> None:
@@ -32,6 +33,57 @@ def test_event() -> None:
                   "Received unexpected link notification")
 
 
+def test_event_all_nsid() -> None:
+    """NETLINK_LISTEN_ALL_NSID notifications: local events must not
+    carry nsid even with a self-referential mapping.  Remote events
+    must carry the correct nsid."""
+
+    with NetNS() as ns1, NetNS() as ns2:
+        net1, net2 = str(ns1), str(ns2)
+
+        with NetNSEnter(net1):
+            rtnl = RtnlFamily()
+        rtnl.ntf_listen_all_nsid()
+        rtnl.ntf_subscribe("rtnlgrp-link")
+
+        # Case 1: no nsid assigned, local event, no nsid expected.
+        ip("link add dummy-lo type dummy", ns=net1)
+
+        # Case 2: self-referential nsid, local event, still no nsid.
+        ip(f"netns set {net1} {LINK_NETNSID}", ns=net1)
+        ip("link add dummy-sr type dummy", ns=net1)
+
+        # Case 3: remote event, nsid present.
+        ip(f"netns set {net2} {LINK_NETNSID2}", ns=net1)
+        ip("link add dummy-re type dummy", ns=net2)
+
+        # Collect the three newlink events, ignoring unrelated noise.
+        events = {}
+        for msg in rtnl.poll_ntf(duration=1):
+            if msg['name'] == 'getlink':
+                ifname = msg['msg'].get('ifname')
+                if ifname in ('dummy-lo', 'dummy-sr', 'dummy-re'):
+                    events[ifname] = msg
+            if len(events) == 3:
+                break
+
+        ksft_true('dummy-lo' in events, "missing local event")
+        ksft_true(events['dummy-lo'].get('nsid') is None,
+                  "local event without nsid should not carry nsid")
+
+        ksft_true('dummy-sr' in events, "missing self-ref event")
+        ksft_true(events['dummy-sr'].get('nsid') is None,
+                  "local event with self-ref nsid should not carry nsid")
+
+        ksft_true('dummy-re' in events, "missing remote event")
+        ksft_eq(events['dummy-re'].get('nsid'), LINK_NETNSID2,
+                "remote event should carry nsid")
+
+        ip("link del dummy-lo", ns=net1)
+        ip("link del dummy-sr", ns=net1)
+        ip("link del dummy-re", ns=net2)
+
+
 def validate_link_netns(netns, ifname, link_netnsid) -> bool:
     link_info = ip(f"-d link show dev {ifname}", ns=netns, json=True)
     if not link_info:
@@ -133,7 +185,12 @@ def test_peer_net() -> None:
 
 
 def main() -> None:
-    ksft_run([test_event, test_link_net, test_peer_net])
+    ksft_run([
+        test_event,
+        test_event_all_nsid,
+        test_link_net,
+        test_peer_net,
+    ])
     ksft_exit()