[PATCH net-next v4 4/4] selftests: net: test AF_PACKET multicast dumps

[Yuyang Huang <sigefriedhyy@gmail.com>]

Dump the link-layer multicast addresses of a dummy device and verify
that ifa_index restricts the dump to that device, that the all-hosts
address joined on link up is listed without IFA_F_GLOBAL, that an
address added with SIOCADDMULTI is listed with IFA_F_GLOBAL and
IFA_MC_USERS, and that IFA_TARGET_NETNSID dumps another netns. Skip
when the kernel does not support AF_PACKET dumps.

Signed-off-by: Yuyang Huang <sigefriedhyy@gmail.com>
---
 tools/testing/selftests/net/rtnetlink.py | 75 +++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/net/rtnetlink.py b/tools/testing/selftests/net/rtnetlink.py
index 5cc3ebdcf08d..cca14c4008cf 100755
--- a/tools/testing/selftests/net/rtnetlink.py
+++ b/tools/testing/selftests/net/rtnetlink.py
@@ -1,17 +1,21 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0
 
+import errno
 import socket
 import struct
 import time
 from lib.py import bkg, ip, ksft_exit, ksft_run, ksft_eq, ksft_ge, ksft_true, KsftSkipEx
-from lib.py import ksft_not_in, ksft_not_none
-from lib.py import CmdExitFailure, NetNS, NetNSEnter, RtnlAddrFamily, RtnlRouteFamily
+from lib.py import ksft_in, ksft_not_in, ksft_not_none
+from lib.py import CmdExitFailure, NetNS, NetNSEnter, NlError, RtnlAddrFamily, RtnlRouteFamily
 from lib.py import defer
 
 IPV4_ALL_HOSTS_MULTICAST = b'\xe0\x00\x00\x01'
 IPV4_TEST_MULTICAST = b'\xef\x01\x01\x01'
 IPV6_TEST_MULTICAST = bytes.fromhex('ff020000000000000000000000000123')
+ETH_ALL_HOSTS_MULTICAST = bytes.fromhex('01005e000001')
+ETH_TEST_MULTICAST_STR = '01:00:5e:01:01:01'
+ETH_TEST_MULTICAST = bytes.fromhex(ETH_TEST_MULTICAST_STR.replace(':', ''))
 
 
 def _users_for(rtnl: RtnlAddrFamily, family: int, grp: bytes, ifindex: int):
@@ -105,6 +109,70 @@ def dump_mcaddr6_check() -> None:
                 s2.close()
 
 
+def dump_mcaddr_l2_check() -> None:
+    """
+    Verify link-layer multicast addresses in an AF_PACKET RTM_GETMULTICAST
+    dump: the ifa-index filter, mc-users, the global flag and
+    target-netnsid.
+    """
+
+    with NetNS() as ns, NetNSEnter(str(ns)):
+        for ifname in ("dummy1", "dummy2"):
+            ip(f"link add name {ifname} type dummy")
+            ip(f"link set {ifname} up")
+        dev_idx = socket.if_nametoindex("dummy1")
+        ip(f"maddr add {ETH_TEST_MULTICAST_STR} dev dummy1")
+
+        rtnl = RtnlAddrFamily()
+        defer(rtnl.close)
+        try:
+            addresses = rtnl.getmulticast(
+                {"ifa-family": socket.AF_PACKET, "ifa-index": dev_idx},
+                dump=True)
+        except NlError as e:
+            if e.error == errno.EOPNOTSUPP:
+                raise KsftSkipEx(
+                    "kernel does not support AF_PACKET multicast dump")
+            raise
+
+        # dummy2 has entries as well, only dummy1 may be listed
+        ksft_eq({addr['ifa-index'] for addr in addresses}, {dev_idx},
+                "AF_PACKET multicast dump ignored ifa-index filter")
+
+        entries = {addr['multicast']: addr for addr in addresses}
+
+        # Bringing an Ethernet device up joins 224.0.0.1, which maps
+        # to 01:00:5e:00:00:01 in the device multicast list.
+        all_hosts = entries.get(ETH_ALL_HOSTS_MULTICAST)
+        ksft_not_none(all_hosts,
+                      "dummy1 does not have the all-hosts link-layer address")
+        if all_hosts is not None:
+            ksft_not_in('global', all_hosts['flags'],
+                        "protocol entry is global")
+
+        static = entries.get(ETH_TEST_MULTICAST)
+        ksft_not_none(static, "dummy1 does not have the SIOCADDMULTI address")
+        if static is not None:
+            ksft_eq(static['mc-users'], 1,
+                    "unexpected mc-users for the SIOCADDMULTI address")
+            ksft_in('global', static['flags'],
+                    "SIOCADDMULTI entry is not global")
+
+        # target-netnsid dumps another netns, ifa-index is relative to it
+        with NetNS() as peer:
+            ip(f"netns set {peer} 5")
+            ip("link add name dummy3 type dummy", ns=peer)
+            ip("link set dummy3 up", ns=peer)
+            peer_idx = ip("link show dummy3", json=True, ns=peer)[0]['ifindex']
+
+            addresses = rtnl.getmulticast(
+                {"ifa-family": socket.AF_PACKET, "target-netnsid": 5},
+                dump=True)
+            ksft_eq({(addr['ifa-index'], addr['target-netnsid'])
+                     for addr in addresses}, {(peer_idx, 5)},
+                    "target-netnsid did not dump the peer netns")
+
+
 def ipv4_devconf_notify() -> None:
     """
     Configure an interface and set ipv4-devconf values through netlink
@@ -315,7 +383,8 @@ def ipv6_route_del_reason_absent() -> None:
 
 
 def main() -> None:
-    ksft_run([dump_mcaddr_check, dump_mcaddr6_check, ipv4_devconf_notify,
+    ksft_run([dump_mcaddr_check, dump_mcaddr6_check, dump_mcaddr_l2_check,
+              ipv4_devconf_notify,
               ipv6_route_del_reason_expired,
               ipv6_route_del_reason_ra_withdrawn,
               ipv6_route_del_reason_absent])
-- 
2.43.0