preserve only manually added ndp table entries in startup config

nsh was mistakenly adding all ndp table entries to startup-config
when the configuration was saved with write-config. This results
in spurious 'permanent' ndp entries when the written config is loaded.

If you find spurious permanent ndp entries on your system these entries
must be removed via 'no ndp <IPv6 address>', then use 'write-config' to
save the fixed the configuration. Alternatively, remove all lines which
set unwanted permanent NDP entries from /etc/nshrc and reboot.

Problem reported and fix tested by Tom.

ok Tom

ndp.c

@@ -756,8 +756,6 @@ conf_ndp(FILE *output, char *delim)
 		rtm = (struct rt_msghdr *)next;
 		if (rtm->rtm_version != RTM_VERSION)
 			continue;
-		if (!(rtm->rtm_flags & RTF_HOST))
-			continue;
 		conf_ndp_entry(output, delim, rtm);
 	}
 	freertdump(rtdump);
@@ -769,13 +767,35 @@ conf_ndp_entry(FILE *output, char *delim, struct rt_msghdr *rtm)
 {
 	struct sockaddr_in6 *sin6;
 	struct sockaddr_dl *sdl;
+	static struct in6_nbrinfo *nbi;
+
+	/* Ignore entries which describe routes to networks. */
+	if (!(rtm->rtm_flags & RTF_HOST))
+		return;
+
+	/*
+	 * Ignore local entries. These correspond to addresses configured
+	 * on our network interfaces, and will already be preserved in case
+	 * of static IPs, and should not be preserved for dynamic IPs.
+	 */
+	if (rtm->rtm_flags & RTF_LOCAL)
+		return;
 
 	sin6 = (struct sockaddr_in6 *)((char *)rtm + rtm->rtm_hdrlen);
 	in6_fillscopeid(sin6);
 	sdl = (struct sockaddr_dl *)((char *)sin6 + ROUNDUP(sin6->sin6_len));
 	if (sdl->sdl_family != AF_LINK)
 		return;
 
+	/* Skip table entries for addresses learned via NDP protocol. */
+	nbi = getnbrinfo(&sin6->sin6_addr, sdl->sdl_index, 0);
+	if (nbi == NULL || nbi->expire != 0)
+		return;
+
+	/*
+	 * This is a 'permanent' non-local entry. We assume this entry
+	 * was manually added to the NDP table, and should be preserved.
+	 */
 	fprintf(output, "%s%s %s", delim, routename6(sin6), ether_str(sdl));
 	if (rtm->rtm_flags & RTF_ANNOUNCE)
 		fputs(" proxy", output);