Re: [PATCH RESEND net-next] netlink: add tracepoint at NL_SET_ERR_MSG
From: Jakub Kicinski <kuba@kernel.org>
Date: 2021-02-03 22:32:02
On Mon, 1 Feb 2021 15:12:19 -0300 Marcelo Ricardo Leitner wrote:
Often userspace won't request the extack information, or they don't log it because of log level or so, and even when they do, sometimes it's not enough to know exactly what caused the error. Netlink extack is the standard way of reporting erros with descriptive error messages. With a trace point on it, we then can know exactly where the error happened, regardless of userspace app. Also, we can even see if the err msg was overwritten. The wrapper do_trace_netlink_extack() is because trace points shouldn't be called from .h files, as trace points are not that small, and the function call to do_trace_netlink_extack() on the macros is not protected by tracepoint_enabled() because the macros are called from modules, and this would require exporting some trace structs. As this is error path, it's better to export just the wrapper instead. Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
quoted hunk ↗ jump to hunk
--- a/include/linux/netlink.h +++ b/include/linux/netlink.h@@ -6,11 +6,15 @@ #include <linux/capability.h> #include <linux/skbuff.h> #include <linux/export.h> +#include <linux/tracepoint.h>
Do we need the include...
#include <net/scm.h> #include <uapi/linux/netlink.h> struct net; +DECLARE_TRACEPOINT(netlink_extack);
... and the declaration? Seems to be a leftover.
quoted hunk ↗ jump to hunk
+void do_trace_netlink_extack(const char *msg); + static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb) { return (struct nlmsghdr *)skb->data;@@ -90,6 +94,8 @@ struct netlink_ext_ack { static const char __msg[] = msg; \ struct netlink_ext_ack *__extack = (extack); \ \ + do_trace_netlink_extack(__msg); \ + \ if (__extack) \ __extack->_msg = __msg; \ } while (0)@@ -110,6 +116,8 @@ struct netlink_ext_ack { static const char __msg[] = msg; \ struct netlink_ext_ack *__extack = (extack); \ \ + do_trace_netlink_extack(__msg); \ + \ if (__extack) { \ __extack->_msg = __msg; \ __extack->bad_attr = (attr); \