netfilter: x_tables: add module alias for icmp matches

The icmp matches are implemented in ip_tables and ip6_tables,
respectively, so for normal iptables they are always available:
those modules are loaded once iptables calls getsockopt() to fetch
available module revisions.

In iptables-over-nftables case probing occurs via nfnetlink, so
these modules might not be loaded.  Add aliases so modprobe can load
these when icmp/icmp6 is requested.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/ip_tables.c

@@ -34,6 +34,7 @@
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
 MODULE_DESCRIPTION("IPv4 packet filter");
+MODULE_ALIAS("ipt_icmp");
 
 void *ipt_alloc_initial_table(const struct xt_table *info)
 {

net/ipv6/netfilter/ip6_tables.c

@@ -38,6 +38,7 @@
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
 MODULE_DESCRIPTION("IPv6 packet filter");
+MODULE_ALIAS("ip6t_icmp6");
 
 void *ip6t_alloc_initial_table(const struct xt_table *info)
 {