IPv4¶

class os_ken.lib.packet.ipv4.ipv4(version=4, header_length=5, tos=0, total_length=0, identification=0, flags=0, offset=0, ttl=255, proto=0, csum=0, src='10.0.0.1', dst='10.0.0.2', option=None)¶

IPv4 (RFC 791) header encoder/decoder class.

NOTE: When decoding, this implementation tries to decode the upper layer protocol even for a fragmented datagram. It isn't likely what a user would want.

An instance has the following attributes at least. Most of them are same to the on-wire counterparts but in host byte order. IPv4 addresses are represented as a string like '192.0.2.1'. __init__ takes the corresponding args in this order.

Attribute	Description	Example
version	Version
header_length	IHL
tos	Type of Service
total_length	Total Length (0 means automatically-calculate when encoding)
identification	Identification
flags	Flags
offset	Fragment Offset
ttl	Time to Live
proto	Protocol
csum	Header Checksum (Ignored and automatically-calculated when encoding)
src	Source Address	'192.0.2.1'
dst	Destination Address	'192.0.2.2'
option	A bytearray which contains the entire Options, or None for no Options

classmethod parser(buf)¶

Decode a protocol header.

This method is used only when decoding a packet.

Decode a protocol header at offset 0 in bytearray buf. Returns the following three objects.

• An object to describe the decoded header.
• A packet_base.PacketBase subclass appropriate for the rest of the packet. None when the rest of the packet should be considered as raw payload.
• The rest of packet.

serialize(payload, prev)¶

Encode a protocol header.

This method is used only when encoding a packet.

Encode a protocol header. Returns a bytearray which contains the header.

payload is the rest of the packet which will immediately follow this header.

prev is a packet_base.PacketBase subclass for the outer protocol header. prev is None if the current header is the outer-most. For example, prev is ipv4 or ipv6 for tcp.serialize.