[RFC net-next 8/9] genetlink: use per-op policy for CTRL_CMD_GETPOLICY

[Jakub Kicinski <kuba@kernel.org>]

Wire up per-op policy for CTRL_CMD_GETPOLICY.
This saves us a call to genlmsg_parse() and will soon allow
dumping this policy.

Create a new policy definition, since we don't want to pollute
ctrl_policy with attributes which CTRL_CMD_GETFAMILY does not
support.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/netlink/genetlink.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 7ceb2dc92a09..f2833e9165c7 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1115,17 +1115,18 @@ struct ctrl_dump_policy_ctx {
 	unsigned int fam_id;
 };
 
+static const struct nla_policy ctrl_policy_policy[] = {
+	[CTRL_ATTR_FAMILY_ID]	= { .type = NLA_U16 },
+	[CTRL_ATTR_FAMILY_NAME]	= { .type = NLA_NUL_STRING,
+				    .len = GENL_NAMSIZ - 1 },
+};
+
 static int ctrl_dumppolicy_start(struct netlink_callback *cb)
 {
+	const struct genl_dumpit_info *info = genl_dumpit_info(cb);
 	struct ctrl_dump_policy_ctx *ctx = (void *)cb->args;
-	struct nlattr *tb[CTRL_ATTR_MAX + 1];
+	struct nlattr **tb = info->attrs;
 	const struct genl_family *rt;
-	int err;
-
-	err = genlmsg_parse(cb->nlh, &genl_ctrl, tb, genl_ctrl.maxattr,
-			    genl_ctrl.policy, cb->extack);
-	if (err)
-		return err;
 
 	if (!tb[CTRL_ATTR_FAMILY_ID] && !tb[CTRL_ATTR_FAMILY_NAME])
 		return -EINVAL;
@@ -1196,6 +1197,8 @@ static const struct genl_ops genl_ctrl_ops[] = {
 	},
 	{
 		.cmd		= CTRL_CMD_GETPOLICY,
+		.policy		= ctrl_policy_policy,
+		.maxattr	= ARRAY_SIZE(ctrl_policy_policy) - 1,
 		.start		= ctrl_dumppolicy_start,
 		.dumpit		= ctrl_dumppolicy,
 	},
-- 
2.26.2