GRE

class os_ken.lib.packet.gre.gre(version=0, protocol=2048, checksum=None, key=None, vsid=None, flow_id=None, seq_number=None)

GRE (RFC2784,RFC2890) header encoder/decoder class.

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

version

Version.

protocol

Protocol Type field. The Protocol Type is defined as "ETHER TYPES".

checksum

Checksum field(optional). When you set a value other than None, this field will be automatically calculated.

key

Key field(optional) This field is intended to be used for identifying an individual traffic flow within a tunnel.

vsid

Virtual Subnet ID field(optional) This field is a 24-bit value that is used to identify the NVGRE-based Virtual Layer 2 Network.

flow_id

FlowID field(optional) This field is an 8-bit value that is used to provide per-flow entropy for flows in the same VSID.

seq_number

Sequence Number field(optional)
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.

os_ken.lib.packet.gre.nvgre(version=0, vsid=0, flow_id=0)

Generate instance of GRE class with information for NVGRE (RFC7637).

Parameters:

  • version -- Version.

  • vsid -- Virtual Subnet ID.

  • flow_id -- FlowID.

Returns:

Instance of GRE class with information for NVGRE.