Commit 51c352bd authored by Edward Cree's avatar Edward Cree Committed by Jakub Kicinski
Browse files

netlink: add support for formatted extack messages 



Include an 80-byte buffer in struct netlink_ext_ack that can be used
 for scnprintf()ed messages.  This does mean that the resulting string
 can't be enumerated, translated etc. in the way NL_SET_ERR_MSG() was
 designed to allow.

Signed-off-by: default avatarEdward Cree <ecree.xilinx@gmail.com>
Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a526a3cc

include/linux/netlink.h

+27 −2
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg) 


/* this can be increased when necessary - don't expose to userland */

#define NETLINK_MAX_COOKIE_LEN	20

#define NETLINK_MAX_FMTMSG_LEN	80



/**

 * struct netlink_ext_ack - netlink extended ACK report struct
@@ -75,6 +76,8 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg) 
 * @miss_nest: nest missing an attribute (%NULL if missing top level attr)

 * @cookie: cookie data to return to userspace (for success)

 * @cookie_len: actual cookie data length

 * @_msg_buf: output buffer for formatted message strings - don't access

 *	directly, use %NL_SET_ERR_MSG_FMT

 */

struct netlink_ext_ack {

	const char *_msg;
@@ -84,13 +87,13 @@ struct netlink_ext_ack { 
	u16 miss_type;

	u8 cookie[NETLINK_MAX_COOKIE_LEN];

	u8 cookie_len;

	char _msg_buf[NETLINK_MAX_FMTMSG_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.)

 * If string formatting is needed use NL_SET_ERR_MSG_FMT.

 */

#define NL_SET_ERR_MSG(extack, msg) do {		\

	static const char __msg[] = msg;		\
@@ -102,9 +105,31 @@ struct netlink_ext_ack { 
		__extack->_msg = __msg;			\

} while (0)



/* We splice fmt with %s at each end even in the snprintf so that both calls

 * can use the same string constant, avoiding its duplication in .ro

 */

#define NL_SET_ERR_MSG_FMT(extack, fmt, args...) do {			       \

	struct netlink_ext_ack *__extack = (extack);			       \

									       \

	if (!__extack)							       \

		break;							       \

	if (snprintf(__extack->_msg_buf, NETLINK_MAX_FMTMSG_LEN,	       \

		     "%s" fmt "%s", "", ##args, "") >=			       \

	    NETLINK_MAX_FMTMSG_LEN)					       \

		net_warn_ratelimited("%s" fmt "%s", "truncated extack: ",      \

				     ##args, "\n");			       \

									       \

	do_trace_netlink_extack(__extack->_msg_buf);			       \

									       \

	__extack->_msg = __extack->_msg_buf;				       \

} while (0)



#define NL_SET_ERR_MSG_MOD(extack, msg)			\

	NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)



#define NL_SET_ERR_MSG_FMT_MOD(extack, fmt, args...)	\

	NL_SET_ERR_MSG_FMT((extack), KBUILD_MODNAME ": " fmt, ##args)



#define NL_SET_BAD_ATTR_POLICY(extack, attr, pol) do {	\

	if ((extack)) {					\

		(extack)->bad_attr = (attr);		\