netfilter: Make legacy configs user selectable

This option makes legacy Netfilter Kconfig user selectable, giving users
the option to configure iptables without enabling any other config.

Make the following KConfig entries user selectable:
 * BRIDGE_NF_EBTABLES_LEGACY
 * IP_NF_ARPTABLES
 * IP_NF_IPTABLES_LEGACY
 * IP6_NF_IPTABLES_LEGACY

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: leitao

net/bridge/netfilter/Kconfig

@@ -41,7 +41,13 @@ config NF_CONNTRACK_BRIDGE
 
 # old sockopt interface and eval loop
 config BRIDGE_NF_EBTABLES_LEGACY
-	tristate
+	tristate "Legacy EBTABLES support"
+	depends on BRIDGE && NETFILTER_XTABLES
+	default n
+	help
+	 Legacy ebtables packet/frame classifier.
+	 This is not needed if you are using ebtables over nftables
+	 (iptables-nft).
 
 menuconfig BRIDGE_NF_EBTABLES
 	tristate "Ethernet Bridge tables (ebtables) support"

net/ipv4/netfilter/Kconfig

@@ -12,7 +12,13 @@ config NF_DEFRAG_IPV4
 
 # old sockopt interface and eval loop
 config IP_NF_IPTABLES_LEGACY
-	tristate
+	tristate "Legacy IP tables support"
+	default	n
+	select NETFILTER_XTABLES
+	help
+	  iptables is a legacy packet classifier.
+	  This is not needed if you are using iptables over nftables
+	  (iptables-nft).
 
 config NF_SOCKET_IPV4
 	tristate "IPv4 socket lookup support"
@@ -318,7 +324,13 @@ endif # IP_NF_IPTABLES
 
 # ARP tables
 config IP_NF_ARPTABLES
-	tristate
+	tristate "Legacy ARPTABLES support"
+	depends on NETFILTER_XTABLES
+	default n
+	help
+	  arptables is a legacy packet classifier.
+	  This is not needed if you are using arptables over nftables
+	  (iptables-nft).
 
 config NFT_COMPAT_ARP
 	tristate

net/ipv6/netfilter/Kconfig

@@ -8,7 +8,14 @@ menu "IPv6: Netfilter Configuration"
 
 # old sockopt interface and eval loop
 config IP6_NF_IPTABLES_LEGACY
-	tristate
+	tristate "Legacy IP6 tables support"
+	depends on INET && IPV6
+	select NETFILTER_XTABLES
+	default n
+	help
+	  ip6tables is a legacy packet classifier.
+	  This is not needed if you are using iptables over nftables
+	  (iptables-nft).
 
 config NF_SOCKET_IPV6
 	tristate "IPv6 socket lookup support"