spath

Documentation

Index

• Constants
• Variables
• type ExpTimeType
  • func ExpTimeFromDuration(duration time.Duration, roundUp bool) (ExpTimeType, error)
  • func (e ExpTimeType) ToDuration() time.Duration
• type HopField
  • func HopFFromRaw(b []byte) (*HopField, error)
  • func (h *HopField) CalcMac(mac hash.Hash, tsInt uint32, prev common.RawBytes) common.RawBytes
  • func (h *HopField) Equal(o *HopField) bool
  • func (h *HopField) Pack() common.RawBytes
  • func (h *HopField) String() string
  • func (h *HopField) Verify(macH hash.Hash, tsInt uint32, prev common.RawBytes) error
  • func (h *HopField) Write(b common.RawBytes)
  • func (h *HopField) WriteTo(w io.Writer) (int64, error)
• type InfoField
  • func InfoFFromRaw(b []byte) (*InfoField, error)
  • func (h *InfoField) Equal(o *InfoField) bool
  • func (inf *InfoField) String() string
  • func (inf *InfoField) Timestamp() time.Time
  • func (inf *InfoField) Write(b common.RawBytes)
  • func (inf *InfoField) WriteTo(w io.Writer) (int64, error)
• type Path
  • func New(raw common.RawBytes) *Path
  • func NewOneHop(isd addr.ISD, ifid common.IFIDType, ts time.Time, exp ExpTimeType, ...) *Path
  • func (p *Path) Copy() *Path
  • func (path *Path) GetHopField(offset int) (*HopField, error)
  • func (path *Path) GetInfoField(offset int) (*InfoField, error)
  • func (path *Path) IncOffsets() error
  • func (path *Path) InitOffsets() error
  • func (path *Path) IsEmpty() bool
  • func (p *Path) Reverse() error

Constants

const (
	HopFieldLength    = common.LineLen
	DefaultHopFExpiry = ExpTimeType(63)
	MacLen            = 3
	XoverMask         = 0x01
	VerifyOnlyMask    = 0x02
	MaxTTL            = 24 * 60 * 60 // One day in seconds
	ExpTimeUnit       = MaxTTL / 256 // ~5m38s
	MaxTTLField       = ExpTimeType(math.MaxUint8)
)

const ErrInfoFTooShort common.ErrMsg = "InfoF too short"

ErrInfoFTooShort indicates that the info field is to short to be parsed.

const InfoFieldLength = common.LineLen

InfoFieldLength is the length of the info field.

const (
	MaxTimestamp = math.MaxUint32
)

Variables

var (
	ErrorHopFTooShort = serrors.New("HopF too short")
	ErrorHopFBadMac   = serrors.New("Bad HopF MAC")
)

var (
	// MaxExpirationTime is the maximum absolute expiration time of SCION hop
	// fields.
	MaxExpirationTime = time.Unix(MaxTimestamp, 0).Add(MaxTTLField.ToDuration())
)

Types

type ExpTimeType

type ExpTimeType uint8

ExpTimeType describes the relative expiration time of the hop field.

func ExpTimeFromDuration

func ExpTimeFromDuration(duration time.Duration, roundUp bool) (ExpTimeType, error)

ExpTimeFromDuration converts a time duration to the relative expiration time.

Round Up Mode:

The round up mode guarantees that the resulting relative expiration time is more than the provided duration. The duration is rounded up to the next unit, and then 1 is subtracted from the result, e.g. 1.3 is rounded to 1. In case the requested duration exceeds the maximum value for the expiration time (256*Unit) in this mode, an error is returned.

Round Down Mode:

The round down mode guarantees that the resulting relative expiration time is less than the provided duration. The duration is rounded down to the next unit, and then 1 is subtracted from the result, e.g. 1.3 is rounded to 0. In case the requested duration is below the unit for the expiration time in this mode, an error is returned.

func (ExpTimeType) ToDuration

func (e ExpTimeType) ToDuration() time.Duration

ToDuration calculates the relative expiration time in seconds. Note that for a 0 value ExpTime, the minimal duration is ExpTimeUnit.

type HopField

type HopField struct {
	Xover      bool
	VerifyOnly bool
	// ExpTime defines for how long this HopField is valid, expressed as the number
	// of ExpTimeUnits relative to the PathSegments's InfoField.Timestamp().
	// A 0 value means the minimum expiration time of ExpTimeUnit.
	// See ToDuration() for how to convert from ExpTimeUnits to Seconds.
	ExpTime ExpTimeType
	// ConsIngress is the interface the PCB entered the AS during path construction.
	ConsIngress common.IFIDType
	// ConsEgress is the interface the PCB exited the AS during path construction.
	ConsEgress common.IFIDType
	// Mac is the message authentication code of this HF,
	// see CalcMac() to see how it should be calculated.
	Mac common.RawBytes
}

Hop Field 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|r r r r r r V X|    ExpTime    |      ConsIngress      |  ...  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...ConsEgress |                      MAC                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The absolute expiration time in seconds of a Hop Field is calculated as:

TS + ( (1 + ExpTime) * ExpTimeUnit ), where TS is the Info Field Timestamp.

func HopFFromRaw

func HopFFromRaw(b []byte) (*HopField, error)

HopFFromRaw returns a HopField object from the raw content in b.

func (*HopField) CalcMac

func (h *HopField) CalcMac(mac hash.Hash, tsInt uint32, prev common.RawBytes) common.RawBytes

CalcMac calculates the MAC of a HopField and its preceding HopField, if any. prev does not contain flags byte. This implies that the length of prev can either be 0 or k*8+7, where k >=0. WARN: If prev is of different length, this function panics.

MAC input block 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Timestamp                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       0       |    ExpTime    |      ConsIngress      |  ...  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...ConsEgress |                                               |
+-+-+-+-+-+-+-+-+                                               |
|                           PrevHopF                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

func (*HopField) Equal

func (h *HopField) Equal(o *HopField) bool

func (*HopField) Pack

func (h *HopField) Pack() common.RawBytes

Pack packs the hop field.

func (*HopField) String

func (h *HopField) String() string

func (*HopField) Verify

func (h *HopField) Verify(macH hash.Hash, tsInt uint32, prev common.RawBytes) error

Verify checks the MAC. The same restrictions on prev as in CalcMac apply, and the function may panic otherwise.

func (*HopField) Write

func (h *HopField) Write(b common.RawBytes)

func (*HopField) WriteTo

func (h *HopField) WriteTo(w io.Writer) (int64, error)

WriteTo implements the io.WriterTo interface.

type InfoField

type InfoField struct {
	// Previously Up, ConsDir = !Up
	ConsDir  bool
	Shortcut bool
	Peer     bool
	// TsInt is the timestamp that denotes when the propagation of a path segment started.
	// Use Timestamp() to get a time.Time value.
	TsInt uint32
	// ISD denotes the origin ISD of a path segment.
	ISD  uint16
	Hops uint8
}

InfoField hast 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|r r r r r P S C|                  Timestamp ...                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      ...      |              ISD              |     Hops      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

func InfoFFromRaw

func InfoFFromRaw(b []byte) (*InfoField, error)

func (*InfoField) Equal

func (h *InfoField) Equal(o *InfoField) bool

func (*InfoField) String

func (inf *InfoField) String() string

func (*InfoField) Timestamp

func (inf *InfoField) Timestamp() time.Time

Timestamp returns TsInt as a time.Time.

func (*InfoField) Write

func (inf *InfoField) Write(b common.RawBytes)

func (*InfoField) WriteTo

func (inf *InfoField) WriteTo(w io.Writer) (int64, error)

WriteTo implements the io.WriterTo interface.

type Path

type Path struct {
	Raw    common.RawBytes
	InfOff int // Offset of current Info Field
	HopOff int // Offset of current Hop Field
}

func New

func New(raw common.RawBytes) *Path

func NewOneHop

func NewOneHop(isd addr.ISD, ifid common.IFIDType, ts time.Time, exp ExpTimeType,
	hfmac hash.Hash) *Path

NewOneHop creates a new one hop path with. If necessary, the caller has to initialize the offsets.

func (*Path) Copy

func (p *Path) Copy() *Path

func (*Path) GetHopField

func (path *Path) GetHopField(offset int) (*HopField, error)

func (*Path) GetInfoField

func (path *Path) GetInfoField(offset int) (*InfoField, error)

func (*Path) IncOffsets

func (path *Path) IncOffsets() error

IncOffsets updates the info and hop indices to the next routing field, while skipping verify only fields.

func (*Path) InitOffsets

func (path *Path) InitOffsets() error

InitOffsets computes the initial Hop Field offset (in bytes) for a newly created packet.

func (*Path) IsEmpty

func (path *Path) IsEmpty() bool

IsEmpty returns true if the path is nil or empty (no raw data).

func (*Path) Reverse

func (p *Path) Reverse() error