netfilter: ip6_tables: ip6t_ext_hdr is now static inline

We may hit this in xt_LOG:

net/built-in.o:xt_LOG.c:function dump_ipv6_packet:
	error: undefined reference to 'ip6t_ext_hdr'

happens with these config options:

CONFIG_NETFILTER_XT_TARGET_LOG=y
CONFIG_IP6_NF_IPTABLES=m

ip6t_ext_hdr is fairly small and it is called in the packet path.
Make it static inline.
Reported-by: Simon Kirby <sim@netnation.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter_ipv6/ip6_tables.h

@@ -287,7 +287,17 @@ extern unsigned int ip6t_do_table(struct sk_buff *skb,
 				  struct xt_table *table);
 
 /* Check for an extension */
-extern int ip6t_ext_hdr(u8 nexthdr);
+static inline int
+ip6t_ext_hdr(u8 nexthdr)
+{	return (nexthdr == IPPROTO_HOPOPTS) ||
+	       (nexthdr == IPPROTO_ROUTING) ||
+	       (nexthdr == IPPROTO_FRAGMENT) ||
+	       (nexthdr == IPPROTO_ESP) ||
+	       (nexthdr == IPPROTO_AH) ||
+	       (nexthdr == IPPROTO_NONE) ||
+	       (nexthdr == IPPROTO_DSTOPTS);
+}
+
 /* find specified header and get offset to it */
 extern int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
 			 int target, unsigned short *fragoff);

net/ipv6/netfilter/ip6_tables.c

@@ -78,19 +78,6 @@ EXPORT_SYMBOL_GPL(ip6t_alloc_initial_table);
 
    Hence the start of any table is given by get_table() below.  */
 
-/* Check for an extension */
-int
-ip6t_ext_hdr(u8 nexthdr)
-{
-	return  (nexthdr == IPPROTO_HOPOPTS)   ||
-		(nexthdr == IPPROTO_ROUTING)   ||
-		(nexthdr == IPPROTO_FRAGMENT)  ||
-		(nexthdr == IPPROTO_ESP)       ||
-		(nexthdr == IPPROTO_AH)        ||
-		(nexthdr == IPPROTO_NONE)      ||
-		(nexthdr == IPPROTO_DSTOPTS);
-}
-
 /* Returns whether matches rule or not. */
 /* Performance critical - called for every packet */
 static inline bool
@@ -2366,7 +2353,6 @@ int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
 EXPORT_SYMBOL(ip6t_register_table);
 EXPORT_SYMBOL(ip6t_unregister_table);
 EXPORT_SYMBOL(ip6t_do_table);
-EXPORT_SYMBOL(ip6t_ext_hdr);
 EXPORT_SYMBOL(ipv6_find_hdr);
 
 module_init(ip6_tables_init);