selftests/net: Add selftest for IPv4 RTM_GETMULTICAST support

This change introduces a new selftest case to verify the functionality
of dumping IPv4 multicast addresses using the RTM_GETMULTICAST netlink
message. The test utilizes the ynl library to interact with the
netlink interface and validate that the kernel correctly reports the
joined IPv4 multicast addresses.

To run the test, execute the following command:

$ vng -v --user root --cpus 16 -- \
    make -C tools/testing/selftests TARGETS=net \
    TEST_PROGS=rtnetlink.py TEST_GEN_PROGS="" run_tests

Cc: Maciej Żenczykowski <maze@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Yuyang Huang <yuyanghuang@google.com>
Link: https://patch.msgid.link/20250207110836.2407224-2-yuyanghuang@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tools/testing/selftests/net/lib/py/ynl.py b/tools/testing/selftests/net/lib/py/ynl.py
index ad1e36baee2a..8986c584cb37 100644
--- a/tools/testing/selftests/net/lib/py/ynl.py
+++ b/tools/testing/selftests/net/lib/py/ynl.py
@@ -42,6 +42,10 @@ class RtnlFamily(YnlFamily):
         super().__init__((SPEC_PATH / Path('rt_link.yaml')).as_posix(),
                          schema='', recv_size=recv_size)
 
+class RtnlAddrFamily(YnlFamily):
+    def __init__(self, recv_size=0):
+        super().__init__((SPEC_PATH / Path('rt_addr.yaml')).as_posix(),
+                         schema='', recv_size=recv_size)
 
 class NetdevFamily(YnlFamily):
     def __init__(self, recv_size=0):