DHCP6¶

DHCPv6 packet parser/serializer

[RFC 3315] DHCPv6 packet format:

The following diagram illustrates the format of DHCP messages sent between clients and servers:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    msg_type   |               transaction_id                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
.                            options                            .
.                           (variable)                          .
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

There are two relay agent messages, which share the following format:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    msg_type   |   hop_count   |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
|                                                               |
|                         link_address                          |
|                                                               |
|                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|                               |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
|                                                               |
|                         peer_address                          |
|                                                               |
|                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|                               |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
.                                                               .
.            options (variable number and length)   ....        .
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

class os_ken.lib.packet.dhcp6.dhcp6(msg_type, options, transaction_id=None, hop_count=0, link_address='::', peer_address='::')¶

DHCPv6 (RFC 3315) header encoder/decoder class.

The serialized packet would looks like the ones described in the following sections.

• RFC 3315 DHCP packet format

An instance has the following attributes at least. Most of them are same to the on-wire counterparts but in host byte order. __init__ takes the corresponding args in this order.

Attribute	Description
msg_type	Identifies the DHCP message type
transaction_id	For unrelayed messages only: the transaction ID for this message exchange.
hop_count	For relayed messages only: number of relay agents that have relayed this message.
link_address	For relayed messages only: a global or site-local address that will be used by the server to identify the link on which the client is located.
peer_address	For relayed messages only: the address of the client or relay agent from which the message to be relayed was received.
options	Options carried in this message

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=None, prev=None)¶

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.

class os_ken.lib.packet.dhcp6.option(code, data, length=0)¶

DHCP (RFC 3315) options encoder/decoder class.

This is used with os_ken.lib.packet.dhcp6.dhcp6.options.

An instance has the following attributes at least. Most of them are same to the on-wire counterparts but in host byte order. __init__ takes the corresponding args in this order.

The format of DHCP options is:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          option-code          |           option-len          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                          option-data                          |
|                      (option-len octets)                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Attribute	Description
option-code	An unsigned integer identifying the specific option type carried in this option.
option-len	An unsigned integer giving the length of the option-data field in this option in octets.
option-data	The data for the option; the format of this data depends on the definition of the option.

class os_ken.lib.packet.dhcp6.options(option_list=None, options_len=0)¶

DHCP (RFC 3315) options encoder/decoder class.

This is used with os_ken.lib.packet.dhcp6.dhcp6.