selftests: net: add test for IPv4 devconf netlink notifications

Introduce a new test, `ipv4_devconf_notify`, to verify that the kernel
sends the appropriate netlink notifications when IPv4 devconf parameters
are modified.

The test depends on the newly introduced iproute2 command:

`ip link set dev <ifname> inet`

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Link: https://patch.msgid.link/20260609204520.4670-3-fmancera@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/testing/selftests/net/rtnetlink.py b/tools/testing/selftests/net/rtnetlink.py
index e9ad5e88da97ff979c560d63121f82b87c8ea836..3622413d793da9dd42c937ac3b75776a3f6ddbd5 100755 (executable)
--- a/tools/testing/selftests/net/rtnetlink.py
+++ b/tools/testing/selftests/net/rtnetlink.py
@@ -1,17 +1,20 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0
 
-from lib.py import ksft_exit, ksft_run, ksft_ge, RtnlAddrFamily
 import socket
+import time
+from lib.py import bkg, ip, ksft_exit, ksft_run, ksft_ge, ksft_true, KsftSkipEx
+from lib.py import CmdExitFailure, NetNS, NetNSEnter, RtnlAddrFamily
 
 IPV4_ALL_HOSTS_MULTICAST = b'\xe0\x00\x00\x01'
 
-def dump_mcaddr_check(rtnl: RtnlAddrFamily) -> None:
+def dump_mcaddr_check() -> None:
     """
     Verify that at least one interface has the IPv4 all-hosts multicast address.
     At least the loopback interface should have this address.
     """
 
+    rtnl = RtnlAddrFamily()
     addresses = rtnl.getmulticast({"ifa-family": socket.AF_INET}, dump=True)
 
     all_host_multicasts = [
@@ -21,9 +24,39 @@ def dump_mcaddr_check(rtnl: RtnlAddrFamily) -> None:
     ksft_ge(len(all_host_multicasts), 1,
             "No interface found with the IPv4 all-hosts multicast address")
 
+def ipv4_devconf_notify() -> None:
+    """
+    Configure an interface and set ipv4-devconf values through netlink
+    to verify that the appropriate netlink notifications are being sent.
+    """
+
+    with NetNS() as ns:
+        with NetNSEnter(str(ns)):
+            ifname = "dummy1"
+            ip(f"link add name {ifname} type dummy", ns=str(ns))
+
+            with bkg("ip monitor", ns=str(ns)) as cmd_obj:
+                time.sleep(1)
+                try:
+                    ip(f"link set dev {ifname} inet forwarding on")
+                    ip(f"link set dev {ifname} inet proxy_arp on")
+                    ip(f"link set dev {ifname} inet rp_filter 1")
+                    ip(f"link set dev {ifname} inet ignore_routes_with_linkdown on")
+                except CmdExitFailure:
+                    raise KsftSkipEx("iproute2 does not support IPv4 devconf attributes")
+                time.sleep(1)
+
+    ksft_true(f"inet {ifname} ignore_routes_with_linkdown on" in cmd_obj.stdout,
+              f"No 'ignore_routes_with_linkdown on' notificiation found for interface {ifname}")
+    ksft_true(f"inet {ifname} rp_filter strict" in cmd_obj.stdout,
+              f"No 'rp_filter strict' notificiation found for interface {ifname}")
+    ksft_true(f"inet {ifname} proxy_neigh on" in cmd_obj.stdout,
+              f"No 'proxy_neigh on' notificiation found for interface {ifname}")
+    ksft_true(f"inet {ifname} forwarding on" in cmd_obj.stdout,
+              f"No 'forwarding on' notificiation found for interface {ifname}")
+
 def main() -> None:
-    rtnl = RtnlAddrFamily()
-    ksft_run([dump_mcaddr_check], args=(rtnl, ))
+    ksft_run([dump_mcaddr_check, ipv4_devconf_notify])
     ksft_exit()
 
 if __name__ == "__main__":