Merge branch 'netlink_ext_ACK'

Johannes Berg says:

====================
netlink extended ACK reporting

Changes since v4:
 * use __NLMSGERR_ATTR_MAX instead of NUM_NLMSGERR_ATTRS

Changes since v3:
 * Add NLM_F_CAPPED and NLM_F_ACK_TLVS flags, to allow entirely
   stateless parsing of the ACK messages by looking at the new
   flags. Need to check NLM_F_ACK_TLVS first, since capping can
   be done in kernels before this patchset without setting the
   flag.
 * Remove "missing_attr" functionality - this can obviously be
   added back rather easily, but I'd rather have more discussion
   about the nesting problem there.
 * Improve documentation of NLMSGERR_ATTR_OFFS
 * Improve message structure documentation, documenting that the
   request message is always capped for success cases
 * fix nlmsg_len of the outer message by calling nlmsg_end()
 * fix memcpy() of the request in success cases, going back to
   the original code that I'd changed before due to the payload
   adjustments that I reverted when introducing tlvlen

Changes since v2:
 * add NUM_NLMSGERR_ATTRS, NLMSGERR_ATTR_MAX
 * fix cookie length to 20 (sha-1 length)
 * move struct members for cookie to patch 3 where they should be
 * another cleanup suggested by David Ahern

Changes since v1:
 * credit Pablo and Jamal
 * incorporate suggestion from David Ahern
 * fix compilation in decnet
====================

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

1 files changed, 32 insertions, 1 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index da14ab61f363..8d2a8924705c 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -62,11 +62,42 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
 	return __netlink_kernel_create(net, unit, THIS_MODULE, cfg);
 }
 
+/* this can be increased when necessary - don't expose to userland */
+#define NETLINK_MAX_COOKIE_LEN	20
+
+/**
+ * struct netlink_ext_ack - netlink extended ACK report struct
+ * @_msg: message string to report - don't access directly, use
+ *	%NL_SET_ERR_MSG
+ * @bad_attr: attribute with error
+ * @cookie: cookie data to return to userspace (for success)
+ * @cookie_len: actual cookie data length
+ */
+struct netlink_ext_ack {
+	const char *_msg;
+	const struct nlattr *bad_attr;
+	u8 cookie[NETLINK_MAX_COOKIE_LEN];
+	u8 cookie_len;
+};
+
+/* Always use this macro, this allows later putting the
+ * message into a separate section or such for things
+ * like translation or listing all possible messages.
+ * Currently string formatting is not supported (due
+ * to the lack of an output buffer.)
+ */
+#define NL_SET_ERR_MSG(extack, msg) do {	\
+	static const char _msg[] = (msg);	\
+						\
+	(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);
 extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
-extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
+extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
+			const struct netlink_ext_ack *extack);
 extern int netlink_has_listeners(struct sock *sk, unsigned int group);
 
 extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);