genetlink: pass extended ACK report down

Pass the extended ACK reporting struct down from generic netlink to
the families, using the existing struct genl_info for simplicity.

Also add support to set the extended ACK information from generic
netlink users.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/genetlink.h

@@ -84,6 +84,7 @@ struct nlattr **genl_family_attrbuf(const struct genl_family *family);
  * @attrs: netlink attributes
  * @_net: network namespace
  * @user_ptr: user pointers
+ * @extack: extended ACK report struct
  */
 struct genl_info {
 	u32			snd_seq;
@@ -94,6 +95,7 @@ struct genl_info {
 	struct nlattr **	attrs;
 	possible_net_t		_net;
 	void *			user_ptr[2];
+	struct netlink_ext_ack *extack;
 };
 
 static inline struct net *genl_info_net(struct genl_info *info)
@@ -106,6 +108,16 @@ static inline void genl_info_net_set(struct genl_info *info, struct net *net)
 	write_pnet(&info->_net, net);
 }
 
+#define GENL_SET_ERR_MSG(info, msg) NL_SET_ERR_MSG((info)->extack, msg)
+
+static inline int genl_err_attr(struct genl_info *info, int err,
+				struct nlattr *attr)
+{
+	info->extack->bad_attr = attr;
+
+	return err;
+}
+
 /**
  * struct genl_ops - generic netlink operations
  * @cmd: command identifier

net/netlink/genetlink.c

@@ -497,7 +497,8 @@ static int genl_lock_done(struct netlink_callback *cb)
 
 static int genl_family_rcv_msg(const struct genl_family *family,
 			       struct sk_buff *skb,
-			       struct nlmsghdr *nlh)
+			       struct nlmsghdr *nlh,
+			       struct netlink_ext_ack *extack)
 {
 	const struct genl_ops *ops;
 	struct net *net = sock_net(skb->sk);
@@ -584,6 +585,7 @@ static int genl_family_rcv_msg(const struct genl_family *family,
 	info.genlhdr = nlmsg_data(nlh);
 	info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
 	info.attrs = attrbuf;
+	info.extack = extack;
 	genl_info_net_set(&info, net);
 	memset(&info.user_ptr, 0, sizeof(info.user_ptr));
 
@@ -618,7 +620,7 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (!family->parallel_ops)
 		genl_lock();
 
-	err = genl_family_rcv_msg(family, skb, nlh);
+	err = genl_family_rcv_msg(family, skb, nlh, extack);
 
 	if (!family->parallel_ops)
 		genl_unlock();