nuttx/net/nat/Kconfig

#
# For a description of the syntax of this configuration file,
# see the file kconfig-language.txt in the NuttX tools repository.
#

config NET_NAT
	bool "Network Address Translation (NAT)"
	default n
	depends on NET_IPFORWARD && IOB_BUFSIZE >= 68
	---help---
		Enable or disable Network Address Translation (NAT) function.

		Note: When forwarding IPv4 packet and applying NAT, NAT may be
		applied directly on a single I/O buffer containing L3 packet header,
		and NAT may need a continuous buffer of at least 68 Bytes
		(IPv4 20B + ICMP 8B + IPv4 20B + TCP 20B).

choice
	prompt "NAT Type"
	default NET_NAT_FULL_CONE
	depends on NET_NAT

config NET_NAT_FULL_CONE
	bool "Full Cone NAT"
	---help---
		Full Cone NAT is easier to traverse than Symmetric NAT, and uses
		less resources than Symmetric NAT.

config NET_NAT_SYMMETRIC
	bool "Symmetric NAT"
	---help---
		Symmetric NAT will be safer than Full Cone NAT, be more difficult
		to traverse, and has more entries which may lead to heavier load.

endchoice

config NET_NAT_HASH_BITS
	int "The bits of NAT entry hashtable"
	default 5
	range 1 10
	depends on NET_NAT
	---help---
		The hashtable of NAT entries will have (1 << bits) buckets.

config NET_NAT_TCP_EXPIRE_SEC
	int "TCP NAT entry expiration seconds"
	default 86400
	depends on NET_NAT
	---help---
		The expiration time for idle TCP entry in NAT.

		Note: The default value 86400 is suggested by RFC2663, Section 2.6,
		Page 5.

config NET_NAT_UDP_EXPIRE_SEC
	int "UDP NAT entry expiration seconds"
	default 240
	depends on NET_NAT
	---help---
		The expiration time for idle UDP entry in NAT.

		Note: RFC2663 (Section 2.6, Page 5) suggests that non-TCP sessions
		that have not been used for a couple of minutes can be assumed to be
		terminated.

config NET_NAT_ICMP_EXPIRE_SEC
	int "ICMP NAT entry expiration seconds"
	default 60
	depends on NET_NAT
	---help---
		The expiration time for idle ICMP entry in NAT.

		Note: The default value 60 is suggested by RFC5508, Section 3.2,
		Page 8.

config NET_NAT_ENTRY_RECLAIM_SEC
	int "The time to auto reclaim all expired entries"
	default 3600
	depends on NET_NAT
	---help---
		The time to auto reclaim all expired entries. A value of zero will
		disable auto reclaiming.

		Note: Expired entries will be automatically reclaimed when matching
		inbound/outbound entries, so this config does not have significant
		impact when NAT is normally used, but very useful when the hashtable
		is big and there are only a few connections using NAT (which will
		only trigger reclaiming on a few chains in hashtable).