tools: ynl: cli: add --policy support

Add --policy flag which can be combined with --do or --dump to query
the kernel's netlink policy for an operation instead of executing it.

Examples:

  $ ynl --family netdev --do dev-get --policy
  {'ifindex': {'max-value': 4294967295, 'min-value': 1, 'type': 'u32'}}

  $ ynl --family ethtool --do channels-get --policy --output-json
  {"header": {"type": "nested", "policy": {"dev-index": ...}}}

  $ ynl --family netdev --dump dev-get --policy
  {}

Link: https://patch.msgid.link/20260310005337.3594225-6-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/tools/net/ynl/pyynl/cli.py b/tools/net/ynl/pyynl/cli.py
index b452d4fb9434..fc9e84754e4b 100755
--- a/tools/net/ynl/pyynl/cli.py
+++ b/tools/net/ynl/pyynl/cli.py
@@ -256,6 +256,8 @@ def main():
     schema_group.add_argument('--no-schema', action='store_true')
 
     dbg_group = parser.add_argument_group('Debug options')
+    io_group.add_argument('--policy', action='store_true',
+                          help='Query kernel policy for the operation instead of executing it')
     dbg_group.add_argument('--dbg-small-recv', default=0, const=4000,
                            action='store', nargs='?', type=int, metavar='INT',
                            help="Length of buffers used for recv()")
@@ -308,6 +310,16 @@ def main():
     if args.dbg_small_recv:
         ynl.set_recv_dbg(True)
 
+    if args.policy:
+        if args.do:
+            pol = ynl.get_policy(args.do, 'do')
+            output(pol.attrs if pol else None)
+            args.do = None
+        if args.dump:
+            pol = ynl.get_policy(args.dump, 'dump')
+            output(pol.attrs if pol else None)
+            args.dump = None
+
     if args.ntf:
         ynl.ntf_subscribe(args.ntf)