[NET]: Add CONFIG_NETDEBUG to suppress bad packet messages.

If you are on a hostile network, or are running protocol tests, you can
easily get the logged swamped by messages about bad UDP and ICMP packets.
This turns those messages off unless a config option is enabled.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Acked-by: Dave Jones <davej@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -1354,12 +1354,12 @@ extern int sock_get_timestamp(struct sock *, struct timeval __user *);
  *	Enable debug/info messages 
  */
 
-#if 0
-#define NETDEBUG(fmt, args...)	do { } while (0)
-#define LIMIT_NETDEBUG(fmt, args...) do { } while(0)
-#else
+#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
 
 /*

net/Kconfig

@@ -27,6 +27,13 @@ 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"