[NETFILTER]: ip6_tables: fix explanation of valid upper protocol number

This explains the allowed upper protocol numbers. IP6T_F_NOPROTO was
introduced to use 0 as Hop-by-Hop option header, not wildcard. But that
seemed to be forgotten. 0 has been used as wildcard since 2002-08-23.

Signed-off-by: Yasuyuki Kozakai <yasuyuki@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 2 deletions

diff --git a/include/linux/netfilter_ipv6/ip6_tables.h b/include/linux/netfilter_ipv6/ip6_tables.h
index 4686f8342cbd..9a720f05888f 100644
--- a/include/linux/netfilter_ipv6/ip6_tables.h
+++ b/include/linux/netfilter_ipv6/ip6_tables.h
@@ -44,8 +44,14 @@ struct ip6t_ip6 {
         char iniface[IFNAMSIZ], outiface[IFNAMSIZ];
         unsigned char iniface_mask[IFNAMSIZ], outiface_mask[IFNAMSIZ];
 
-        /* ARGH, HopByHop uses 0, so can't do 0 = ANY,
-           instead IP6T_F_NOPROTO must be set */
+        /* Upper protocol number
+         * - The allowed value is 0 (any) or protocol number of last parsable
+         *   header, which is 50 (ESP), 59 (No Next Header), 135 (MH), or
+         *   the non IPv6 extension headers.
+         * - The protocol numbers of IPv6 extension headers except of ESP and
+         *   MH do not match any packets.
+         * - You also need to set IP6T_FLAGS_PROTO to "flags" to check protocol.
+         */
         u_int16_t proto;
         /* TOS to match iff flags & IP6T_F_TOS */
         u_int8_t tos;