"""Address Resolution Protocol."""

from pypacker import pypacker

# Hardware address format
ARP_HRD_ETH	= 0x0001		# ethernet hardware
ARP_HRD_IEEE802	= 0x0006		# IEEE 802 hardware

# Protocol address format
ARP_PRO_IP	= 0x0800		# IP protocol

# ARP operation
ARP_OP_REQUEST		= 1		# request to resolve ha given pa
ARP_OP_REPLY		= 2		# response giving hardware address
ARP_OP_REVREQUEST	= 3		# request to resolve pa given ha
ARP_OP_REVREPLY		= 4		# response giving protocol address


class ARP(pypacker.Packet):
	__hdr__ = (
		("hrd", "H", ARP_HRD_ETH),
		("pro", "H", ARP_PRO_IP),
		("hln", "B", 6),			# hardware address length
		("pln", "B", 4),			# protocol address length
		("op", "H", ARP_OP_REQUEST),
		("sha", "6s", b"\x00" * 6),		# sender mac
		("spa", "4s", b"\x00" * 6),		# sender ip
		("tha", "6s", b"\x00" * 6),		# target mac
		("tpa", "4s", b"\x00" * 6)		# target ip
	)

	# convenient access
	sha_s = pypacker.get_property_mac("sha")
	spa_s = pypacker.get_property_ip4("spa")
	tha_s = pypacker.get_property_mac("tha")
	tpa_s = pypacker.get_property_ip4("tpa")