const (
// VLANNone is a special VLAN ID which indicates that no VLAN is being
// used in a Frame. In this case, the VLAN's other fields may be used
// to indicate a Frame's priority.
VLANNone = 0x000
// VLANMax is a reserved VLAN ID which may indicate a wildcard in some
// management systems, but may not be configured or transmitted in a
// VLAN tag.
VLANMax = 0xfff
)
Broadcast is a special hardware address which indicates a Frame should be sent to every device on a given LAN segment.
var Broadcast = net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
ErrInvalidFCS is returned when Frame.UnmarshalFCS detects an incorrect Ethernet frame check sequence in a byte slice for a Frame.
var ErrInvalidFCS = errors.New("invalid frame check sequence")
ErrInvalidVLAN is returned when a VLAN tag is invalid due to one of the following reasons:
var ErrInvalidVLAN = errors.New("invalid VLAN")
An EtherType is a value used to identify an upper layer protocol encapsulated in a Frame.
A list of IANA-assigned EtherType values may be found here: http://www.iana.org/assignments/ieee-802-numbers/ieee-802-numbers.xhtml.
type EtherType uint16
Common EtherType values frequently used in a Frame.
const (
EtherTypeIPv4 EtherType = 0x0800
EtherTypeARP EtherType = 0x0806
EtherTypeIPv6 EtherType = 0x86DD
// EtherTypeVLAN and EtherTypeServiceVLAN are used as 802.1Q Tag Protocol
// Identifiers (TPIDs).
EtherTypeVLAN EtherType = 0x8100
EtherTypeServiceVLAN EtherType = 0x88a8
)
func (i EtherType) String() string
A Frame is an IEEE 802.3 Ethernet II frame. A Frame contains information such as source and destination hardware addresses, zero or more optional 802.1Q VLAN tags, an EtherType, and payload data.
type Frame struct {
// Destination specifies the destination hardware address for this Frame.
//
// If this address is set to Broadcast, the Frame will be sent to every
// device on a given LAN segment.
Destination net.HardwareAddr
// Source specifies the source hardware address for this Frame.
//
// Typically, this is the hardware address of the network interface used to
// send this Frame.
Source net.HardwareAddr
// ServiceVLAN specifies an optional 802.1Q service VLAN tag, for use with
// 802.1ad double tagging, or "Q-in-Q". If ServiceVLAN is not nil, VLAN must
// not be nil as well.
//
// Most users should leave this field set to nil and use VLAN instead.
ServiceVLAN *VLAN
// VLAN specifies an optional 802.1Q customer VLAN tag, which may or may
// not be present in a Frame. It is important to note that the operating
// system may automatically strip VLAN tags before they can be parsed.
VLAN *VLAN
// EtherType is a value used to identify an upper layer protocol
// encapsulated in this Frame.
EtherType EtherType
// Payload is a variable length data payload encapsulated by this Frame.
Payload []byte
}
func (f *Frame) MarshalBinary() ([]byte, error)
MarshalBinary allocates a byte slice and marshals a Frame into binary form.
func (f *Frame) MarshalFCS() ([]byte, error)
MarshalFCS allocates a byte slice, marshals a Frame into binary form, and finally calculates and places a 4-byte IEEE CRC32 frame check sequence at the end of the slice.
Most users should use MarshalBinary instead. MarshalFCS is provided as a convenience for rare occasions when the operating system cannot automatically generate a frame check sequence for an Ethernet frame.
func (f *Frame) UnmarshalBinary(b []byte) error
UnmarshalBinary unmarshals a byte slice into a Frame.
func (f *Frame) UnmarshalFCS(b []byte) error
UnmarshalFCS computes the IEEE CRC32 frame check sequence of a Frame, verifies it against the checksum present in the byte slice, and finally, unmarshals a byte slice into a Frame.
Most users should use UnmarshalBinary instead. UnmarshalFCS is provided as a convenience for rare occasions when the operating system cannot automatically verify a frame check sequence for an Ethernet frame.
Priority is an IEEE P802.1p priority level. Priority can be any value from 0 to 7.
It is important to note that priority 1 (PriorityBackground) actually has a lower priority than 0 (PriorityBestEffort). All other Priority constants indicate higher priority as the integer values increase.
type Priority uint8
IEEE P802.1p recommended priority levels. Note that PriorityBackground has a lower priority than PriorityBestEffort.
const (
PriorityBackground Priority = 1
PriorityBestEffort Priority = 0
PriorityExcellentEffort Priority = 2
PriorityCriticalApplications Priority = 3
PriorityVideo Priority = 4
PriorityVoice Priority = 5
PriorityInternetworkControl Priority = 6
PriorityNetworkControl Priority = 7
)
A VLAN is an IEEE 802.1Q Virtual LAN (VLAN) tag. A VLAN contains information regarding traffic priority and a VLAN identifier for a given Frame.
type VLAN struct {
// Priority specifies a IEEE P802.1p priority level. Priority can be any
// value from 0 to 7.
Priority Priority
// DropEligible indicates if a Frame is eligible to be dropped in the
// presence of network congestion.
DropEligible bool
// ID specifies the VLAN ID for a Frame. ID can be any value from 0 to
// 4094 (0x000 to 0xffe), allowing up to 4094 VLANs.
//
// If ID is 0 (0x000, VLANNone), no VLAN is specified, and the other fields
// simply indicate a Frame's priority.
ID uint16
}
func (v *VLAN) MarshalBinary() ([]byte, error)
MarshalBinary allocates a byte slice and marshals a VLAN into binary form.
func (v *VLAN) UnmarshalBinary(b []byte) error
UnmarshalBinary unmarshals a byte slice into a VLAN.