Introduced by changeset 
95e41e93e18d8e1e272ce23d96bae4f17ce11d42
("[IPV6]: Make ndisc_flow_init() common for later use.")
Reported by Stephen Rothwell.
In file included from net/ipv6/netfilter/ip6_tables.c:21:
include/linux/icmpv6.h:192: warning: 'struct in6_addr' declared inside parameter list
include/linux/icmpv6.h:192: warning: its scope is only this definition or declaration, which is probably not what you want
Signed-off-by: David S. Miller <davem@davemloft.net>
                                                          int code, int pos);
 
 struct flowi;
+struct in6_addr;
 extern void                            icmpv6_flow_init(struct sock *sk,
                                                         struct flowi *fl,
                                                         u8 type,