netdev - [RFC net-next 9/9] genetlink: allow dumping command-specific policy

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Date:   Wed, 30 Sep 2020 17:05:18 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     netdev@...r.kernel.org
Cc:     andrew@...n.ch, johannes@...solutions.net, jiri@...nulli.us,
        mkubecek@...e.cz, dsahern@...nel.org, pablo@...filter.org,
        Jakub Kicinski <kuba@...nel.org>
Subject: [RFC net-next 9/9] genetlink: allow dumping command-specific policy

Right now CTRL_CMD_GETPOLICY can only dump the family-wide
policy. Support dumping policy of a specific op.

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
 include/uapi/linux/genetlink.h |  1 +
 net/netlink/genetlink.c        | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/genetlink.h b/include/uapi/linux/genetlink.h
index 9c0636ec2286..7dbe2d5d7d46 100644
--- a/include/uapi/linux/genetlink.h
+++ b/include/uapi/linux/genetlink.h
@@ -64,6 +64,7 @@ enum {
 	CTRL_ATTR_OPS,
 	CTRL_ATTR_MCAST_GROUPS,
 	CTRL_ATTR_POLICY,
+	CTRL_ATTR_OP,
 	__CTRL_ATTR_MAX,
 };
 
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index f2833e9165c7..12e9f323af35 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1113,12 +1113,14 @@ static int genl_ctrl_event(int event, const struct genl_family *family,
 struct ctrl_dump_policy_ctx {
 	unsigned long state;
 	unsigned int fam_id;
+	u8 cmd;
 };
 
 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 },
+	[CTRL_ATTR_OP]		= { .type = NLA_U8 },
 };
 
 static int ctrl_dumppolicy_start(struct netlink_callback *cb)
@@ -1127,6 +1129,8 @@ static int ctrl_dumppolicy_start(struct netlink_callback *cb)
 	struct ctrl_dump_policy_ctx *ctx = (void *)cb->args;
 	struct nlattr **tb = info->attrs;
 	const struct genl_family *rt;
+	struct genl_ops op;
+	int err;
 
 	if (!tb[CTRL_ATTR_FAMILY_ID] && !tb[CTRL_ATTR_FAMILY_NAME])
 		return -EINVAL;
@@ -1145,10 +1149,23 @@ static int ctrl_dumppolicy_start(struct netlink_callback *cb)
 	if (!rt)
 		return -ENOENT;
 
-	if (!rt->policy)
+	if (tb[CTRL_ATTR_OP]) {
+		ctx->cmd = nla_get_u8(tb[CTRL_ATTR_OP]);
+
+		err = genl_get_cmd(ctx->cmd, rt, &op);
+		if (err) {
+			NL_SET_BAD_ATTR(cb->extack, tb[CTRL_ATTR_OP]);
+			return err;
+		}
+	} else {
+		op.policy = rt->policy;
+		op.maxattr = rt->maxattr;
+	}
+
+	if (!op.policy)
 		return -ENODATA;
 
-	return netlink_policy_dump_start(rt->policy, rt->maxattr, &ctx->state);
+	return netlink_policy_dump_start(op.policy, op.maxattr, &ctx->state);
 }
 
 static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
@@ -1167,6 +1184,8 @@ static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
 
 		if (nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, ctx->fam_id))
 			goto nla_put_failure;
+		if (ctx->cmd && nla_put_u8(skb, CTRL_ATTR_OP, ctx->cmd))
+			goto nla_put_failure;
 
 		nest = nla_nest_start(skb, CTRL_ATTR_POLICY);
 		if (!nest)
-- 
2.26.2