iptables: enable basic kernel options

Enable the basic kernel options for iptables to be useful at least to
filter incoming connections.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

linux/linux.mk

@@ -212,6 +212,11 @@ define LINUX_CONFIGURE_CMDS
 		$(call KCONFIG_ENABLE_OPT,CONFIG_SECURITY,$(@D)/.config)
 		$(call KCONFIG_ENABLE_OPT,CONFIG_SECURITY_SMACK,$(@D)/.config)
 		$(call KCONFIG_ENABLE_OPT,CONFIG_SECURITY_NETWORK,$(@D)/.config))
+	$(if $(BR2_PACKAGE_IPTABLES),
+		$(call KCONFIG_ENABLE_OPT,CONFIG_IP_NF_IPTABLES,$(@D)/.config)
+		$(call KCONFIG_ENABLE_OPT,CONFIG_IP_NF_FILTER,$(@D)/.config)
+		$(call KCONFIG_ENABLE_OPT,CONFIG_NETFILTER,$(@D)/.config)
+		$(call KCONFIG_ENABLE_OPT,CONFIG_NETFILTER_XTABLES,$(@D)/.config))
 	$(if $(BR2_LINUX_KERNEL_APPENDED_DTB),
 		$(call KCONFIG_ENABLE_OPT,CONFIG_ARM_APPENDED_DTB,$(@D)/.config))
 	yes '' | $(TARGET_MAKE_ENV) $(MAKE1) $(LINUX_MAKE_FLAGS) -C $(@D) oldconfig