Merge branch 'xdp-netlink-ext-ack'

Jakub Kicinski says:

====================
xdp: use netlink extended ACK reporting

This series is an attempt to make XDP more user friendly by
enabling exploiting the recently added netlink extended ACK
reporting to carry messages to user space.

David Ahern's iproute2 ext ack patches for ip link are sufficient
to show the errors like this:

Error: nfp: MTU too large w/ XDP enabled

Where the message is coming directly from the driver.  There could
still be a bit of a leap for a complete novice from the message
above to the right settings, but it's a big improvement over the
standard "Invalid argument" message.

v1/non-rfc:
 - add a separate macro in patch 1;
 - add KBUILD_MODNAME as part of the message (Daniel);
 - don't print the error to logs in patch 1.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 16 insertions, 2 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 6847714a5ae3..9c23bd2efb56 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -813,11 +813,16 @@ enum xdp_netdev_command {
 	XDP_QUERY_PROG,
 };
 
+struct netlink_ext_ack;
+
 struct netdev_xdp {
 	enum xdp_netdev_command command;
 	union {
 		/* XDP_SETUP_PROG */
-		struct bpf_prog *prog;
+		struct {
+			struct bpf_prog *prog;
+			struct netlink_ext_ack *extack;
+		};
 		/* XDP_QUERY_PROG */
 		bool prog_attached;
 	};
@@ -3291,7 +3296,8 @@ int dev_get_phys_port_id(struct net_device *dev,
 int dev_get_phys_port_name(struct net_device *dev,
 			   char *name, size_t len);
 int dev_change_proto_down(struct net_device *dev, bool proto_down);
-int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags);
+int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
+		      int fd, u32 flags);
 struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *dev);
 struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 				    struct netdev_queue *txq, int *ret);
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 8d2a8924705c..c20395edf2de 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -92,6 +92,14 @@ struct netlink_ext_ack {
 	(extack)->_msg = _msg;			\
 } while (0)
 
+#define NL_MOD_TRY_SET_ERR_MSG(extack, msg) do {		\
+	static const char _msg[] = KBUILD_MODNAME ": " msg;	\
+	struct netlink_ext_ack *_extack = (extack);		\
+								\
+	if (_extack)						\
+		_extack->_msg = _msg;				\
+} while (0)
+
 extern void netlink_kernel_release(struct sock *sk);
 extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);