Treat ND option 31 as userland (DNSSL support)

As specified in RFC6106, DNSSL option contains one or more domain names
of DNS suffixes.  8-bit identifier of the DNSSL option type as assigned
by the IANA is 31.  This option should also be treated as userland.
Signed-off-by: NAlexey I. Froloff <raorn@raorn.name>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/ndisc.h

@@ -34,6 +34,7 @@ enum {
 	__ND_OPT_ARRAY_MAX,
 	ND_OPT_ROUTE_INFO = 24,		/* RFC4191 */
 	ND_OPT_RDNSS = 25,		/* RFC5006 */
+	ND_OPT_DNSSL = 31,		/* RFC6106 */
 	__ND_OPT_MAX
 };
 

net/ipv6/ndisc.c

@@ -15,6 +15,7 @@
 /*
  *	Changes:
  *
+ *	Alexey I. Froloff		:	RFC6106 (DNSSL) support
  *	Pierre Ynard			:	export userland ND options
  *						through netlink (RDNSS support)
  *	Lars Fenneberg			:	fixed MTU setting on receipt
@@ -228,7 +229,8 @@ static struct nd_opt_hdr *ndisc_next_option(struct nd_opt_hdr *cur,
 
 static inline int ndisc_is_useropt(struct nd_opt_hdr *opt)
 {
-	return opt->nd_opt_type == ND_OPT_RDNSS;
+	return opt->nd_opt_type == ND_OPT_RDNSS ||
+		opt->nd_opt_type == ND_OPT_DNSSL;
 }
 
 static struct nd_opt_hdr *ndisc_next_useropt(struct nd_opt_hdr *cur,