[NET]: Replace CONFIG_NET_DEBUG with sysctl.

Covert network warning messages from a compile time to runtime choice.
Removes kernel config option and replaces it with new /proc/sys/net/core/warnings.
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/filesystems/proc.txt

@@ -1421,6 +1421,15 @@ fewer messages that will be written. Message_burst controls when messages will
 be dropped.  The  default  settings  limit  warning messages to one every five
 seconds.
 
+warnings
+--------
+
+This controls console messages from the networking stack that can occur because
+of problems on the network like duplicate address or bad checksums. Normally,
+this should be enabled, but if the problem persists the messages can be
+disabled.
+
+
 netdev_max_backlog
 ------------------
 

include/linux/sysctl.h

@@ -290,6 +290,7 @@ enum
 	NET_CORE_BUDGET=19,
 	NET_CORE_AEVENT_ETIME=20,
 	NET_CORE_AEVENT_RSEQTH=21,
+	NET_CORE_WARNINGS=22,
 };
 
 /* /proc/sys/net/ethernet */

include/net/sock.h

@@ -1334,14 +1334,12 @@ extern int sock_get_timestampns(struct sock *, struct timespec __user *);
 /* 
  *	Enable debug/info messages 
  */
+extern int net_msg_warn;
+#define NETDEBUG(fmt, args...) \
+	do { if (net_msg_warn) printk(fmt,##args); } while (0)
 
-#ifdef CONFIG_NETDEBUG
-#define NETDEBUG(fmt, args...)	printk(fmt,##args)
-#define LIMIT_NETDEBUG(fmt, args...) do { if (net_ratelimit()) printk(fmt,##args); } while(0)
-#else
-#define NETDEBUG(fmt, args...)	do { } while (0)
-#define LIMIT_NETDEBUG(fmt, args...) do { } while(0)
-#endif
+#define LIMIT_NETDEBUG(fmt, args...) \
+	do { if (net_msg_warn && net_ratelimit()) printk(fmt,##args); } while(0)
 
 /*
  * Macros for sleeping on a socket. Use them like this:

net/Kconfig

@@ -27,13 +27,6 @@ if NET
 
 menu "Networking options"
 
-config NETDEBUG
-	bool "Network packet debugging"
-	help
-	  You can say Y here if you want to get additional messages useful in
-	  debugging bad packets, but can overwhelm logs under denial of service
-	  attacks.
-
 source "net/packet/Kconfig"
 source "net/unix/Kconfig"
 source "net/xfrm/Kconfig"

net/core/sysctl_net_core.c

@@ -136,6 +136,14 @@ ctl_table core_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec
 	},
+	{
+		.ctl_name	= NET_CORE_WARNINGS,
+		.procname	= "warnings",
+		.data		= &net_msg_warn,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec
+	},
 	{ .ctl_name = 0 }
 };
 

net/core/utils.c

@@ -32,6 +32,8 @@
 
 int net_msg_cost = 5*HZ;
 int net_msg_burst = 10;
+int net_msg_warn = 1;
+EXPORT_SYMBOL(net_msg_warn);
 
 /*
  * All net warning printk()s should be guarded by this function.