: Add a comment describing what a NUD stands for.

When I studied the neighbor code I puzzled over what the NUD can mean for quite a long time.

Finally I asked Alexey and he said that this was smth like "neighbor unreachability detection".

Does it worth adding a comment helping future developers understand what's going on?

---

index 09f9fc6..bc34144 100644
@@ -26,6 +26,10 @@
 #include <linux/sysctl.h>
 #include <net/rtnetlink.h>
 
+/*
+ * NUD stands for "neighbor unreachability detection"
+ */
+
 #define NUD_IN_TIMER	(NUD_INCOMPLETE|NUD_REACHABLE|NUD_DELAY|NUD_PROBE)
 #define NUD_VALID	(NUD_PERMANENT|NUD_NOARP|NUD_REACHABLE|NUD_PROBE|NUD_STALE|NUD_DELAY)
 #define NUD_CONNECTED	(NUD_PERMANENT|NUD_NOARP|NUD_REACHABLE)

From: Pavel Emelyanov <[email protected]>
Date: Thu, 10 Jan 2008 18:05:25 +0300

NUD is a common acronym in the IPV6 RFCs and various books on the topic, but it doesn't hurt to add this comment so I applied this patch thanks.