netlink: implement nla_put_in_addr and nla_put_in6_addr

IP addresses are often stored in netlink attributes. Add generic functions
to do that.

For nla_put_in_addr, it would be nicer to pass struct in_addr but this is
not used universally throughout the kernel, in way too many places __be32 is
used to store IPv4 address.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_tunnel.c

@@ -1739,10 +1739,8 @@ static int ip6_tnl_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	struct __ip6_tnl_parm *parm = &tunnel->parms;
 
 	if (nla_put_u32(skb, IFLA_IPTUN_LINK, parm->link) ||
-	    nla_put(skb, IFLA_IPTUN_LOCAL, sizeof(struct in6_addr),
-		    &parm->laddr) ||
-	    nla_put(skb, IFLA_IPTUN_REMOTE, sizeof(struct in6_addr),
-		    &parm->raddr) ||
+	    nla_put_in6_addr(skb, IFLA_IPTUN_LOCAL, &parm->laddr) ||
+	    nla_put_in6_addr(skb, IFLA_IPTUN_REMOTE, &parm->raddr) ||
 	    nla_put_u8(skb, IFLA_IPTUN_TTL, parm->hop_limit) ||
 	    nla_put_u8(skb, IFLA_IPTUN_ENCAP_LIMIT, parm->encap_limit) ||
 	    nla_put_be32(skb, IFLA_IPTUN_FLOWINFO, parm->flowinfo) ||