[PATCH 3/3 net-next v4] selftests: net: add test for IPv4 devconf netlink notifications

[Fernando Fernandez Mancera <fmancera@suse.de>]

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

Since YNL currently has a bug where it declares an array of u32 values
instead of the nested attributes expected by the kernel for devconf set
operations, a temporary hack (`patched_add_attr`) is included to
pack the netlink attributes correctly.

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
v3: added this patch to the series as requested by Paolo.
v4: fixed lint warnings, some of them cannot be fixed as they are
related to the YNL hack.
---
 tools/testing/selftests/net/rtnetlink.py | 74 ++++++++++++++++++++++--
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/net/rtnetlink.py b/tools/testing/selftests/net/rtnetlink.py
index e9ad5e88da97..c4136e73b6d0 100755
--- a/tools/testing/selftests/net/rtnetlink.py
+++ b/tools/testing/selftests/net/rtnetlink.py
@@ -1,17 +1,22 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0
 
-from lib.py import ksft_exit, ksft_run, ksft_ge, RtnlAddrFamily
 import socket
+import struct
+import time
+import types
+from lib.py import bkg, ip, ksft_exit, ksft_run, ksft_ge, ksft_true
+from lib.py import NetNS, NetNSEnter, RtnlAddrFamily, RtnlFamily
 
 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 +26,70 @@ 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)):
+            rtnl = RtnlFamily()
+
+            ifname = "dummy1"
+            ip(f"link add name {ifname} type dummy", ns=str(ns))
+
+            link_info = ip(f"link show dev {ifname}", ns=str(ns), json=True)
+            ksft_true(bool(link_info), f"Failed to retrieve link info for {ifname}")
+            ifindex = link_info[0]["ifindex"]
+
+            # YNL do not support netconf notifications yet
+            with bkg("ip monitor", ns=str(ns)) as cmd_obj:
+                original_add_attr = rtnl._add_attr
+                time.sleep(0.5)
+
+                # Currently YNL has a bug for applying devconf values,
+                # this hack fixes it. In essence, YNL is declaring an
+                # array of u32 values, while kernel expects a nested attribute
+                # on set operation.
+                def patched_add_attr(self, space, name, value, search_attrs):
+                    if name == 'conf' and value == b"MAGIC_CONF":
+                        fwd_attr = struct.pack("=HHI", 8, 1, 1)
+                        proxy_arp_attr = struct.pack("=HHI", 8, 3, 1)
+                        rp_filter_attr = struct.pack("=HHI", 8, 8, 1)
+                        ignore_routes_attr = struct.pack("=HHI", 8, 29, 1)
+
+                        return struct.pack("=HH", 36, 0x8001) + fwd_attr \
+                                + proxy_arp_attr \
+                                + rp_filter_attr \
+                                + ignore_routes_attr
+
+                    return original_add_attr(space, name, value, search_attrs)
+
+                rtnl._add_attr = types.MethodType(patched_add_attr, rtnl)
+
+                req = {
+                    "ifi-index": ifindex,
+                    "af-spec": {
+                        "inet": {
+                            "conf": b"MAGIC_CONF"
+                        }
+                    }
+                }
+                rtnl.newlink(req)
+                time.sleep(0.5)
+
+    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__":
-- 
2.53.0