netfilter: nat: merge ipv4/ipv6 masquerade code into main nat module

Instead of using extra modules for these, turn the config options into
an implicit dependency that adds masq feature to the protocol specific nf_nat module.

before:
text data bss dec hex filename
2001 860 4 2865 b31 net/ipv4/netfilter/nf_nat_masquerade_ipv4.ko
5579 780 2 6361 18d9 net/ipv4/netfilter/nf_nat_ipv4.ko
2860 836 8 3704 e78 net/ipv6/netfilter/nf_nat_masquerade_ipv6.ko
6648 780 2 7430 1d06 net/ipv6/netfilter/nf_nat_ipv6.ko

after:
text data bss dec hex filename
7245 872 8 8125 1fbd net/ipv4/netfilter/nf_nat_ipv4.ko
9165 848 12 10025 2729 net/ipv6/netfilter/nf_nat_ipv6.ko

Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/ipv4/netfilter/Kconfig

···
 	  source and destination ports.
 
 config NF_NAT_MASQUERADE_IPV4
-	tristate "IPv4 masquerade support"
-	help
-	  This is the kernel functionality to provide NAT in the masquerade
-	  flavour (automatic source address selection).
+	bool
 
 config NFT_MASQ_IPV4
 	tristate "IPv4 masquerading support for nf_tables"

net/ipv4/netfilter/Makefile

···
 obj-$(CONFIG_NF_CONNTRACK_IPV4) += nf_conntrack_ipv4.o
 
 nf_nat_ipv4-y		:= nf_nat_l3proto_ipv4.o nf_nat_proto_icmp.o
+nf_nat_ipv4-$(CONFIG_NF_NAT_MASQUERADE_IPV4) += nf_nat_masquerade_ipv4.o
 obj-$(CONFIG_NF_NAT_IPV4) += nf_nat_ipv4.o
 
 # defrag
···
 nf_nat_snmp_basic-y := nf_nat_snmp_basic.asn1.o nf_nat_snmp_basic_main.o
 $(obj)/nf_nat_snmp_basic_main.o: $(obj)/nf_nat_snmp_basic.asn1.h
 obj-$(CONFIG_NF_NAT_SNMP_BASIC) += nf_nat_snmp_basic.o
-
-obj-$(CONFIG_NF_NAT_MASQUERADE_IPV4) += nf_nat_masquerade_ipv4.o
-
 
 # NAT protocols (nf_nat)
 obj-$(CONFIG_NF_NAT_PROTO_GRE) += nf_nat_proto_gre.o

net/ipv4/netfilter/nf_nat_masquerade_ipv4.c

···
  */
 
 #include <linux/types.h>
-#include <linux/module.h>
 #include <linux/atomic.h>
 #include <linux/inetdevice.h>
 #include <linux/ip.h>
···
 	unregister_inetaddr_notifier(&masq_inet_notifier);
 }
 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_unregister_notifier);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Rusty Russell <[e-mail]>");

net/ipv6/netfilter/Kconfig

···
 if NF_NAT_IPV6
 
 config NF_NAT_MASQUERADE_IPV6
-	tristate "IPv6 masquerade support"
-	help
-	  This is the kernel functionality to provide NAT in the masquerade
-	  flavour (automatic source address selection) for IPv6.
+	bool
 
 endif # NF_NAT_IPV6
 

net/ipv6/netfilter/Makefile

···
 obj-$(CONFIG_NF_CONNTRACK_IPV6) += nf_conntrack_ipv6.o
 
 nf_nat_ipv6-y		:= nf_nat_l3proto_ipv6.o nf_nat_proto_icmpv6.o
+nf_nat_ipv6-$(CONFIG_NF_NAT_MASQUERADE_IPV6) += nf_nat_masquerade_ipv6.o
 obj-$(CONFIG_NF_NAT_IPV6) += nf_nat_ipv6.o
-obj-$(CONFIG_NF_NAT_MASQUERADE_IPV6) += nf_nat_masquerade_ipv6.o
 
 # defrag
 nf_defrag_ipv6-y := nf_defrag_ipv6_hooks.o nf_conntrack_reasm.o

net/ipv6/netfilter/nf_nat_masquerade_ipv6.c

···
  */
 
 #include <linux/kernel.h>
-#include <linux/module.h>
 #include <linux/atomic.h>
 #include <linux/netdevice.h>
 #include <linux/ipv6.h>
···
 	unregister_netdevice_notifier(&masq_dev_notifier);
 }
 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6_unregister_notifier);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Patrick McHardy <[e-mail]>");