packet

Documentation

Overview

Package packet support for TCP/IP packet manipulations needed by the Aporeto infrastructure.

Index

• Constants
• Variables
• func TCPFlagsToStr(flags uint8) string
• type Packet
  • func New(context uint64, bytes []byte, mark string) (packet *Packet, err error)
  • func (p *Packet) CheckTCPAuthenticationOption(iOptionLength int) (err error)
  • func (p *Packet) DecreaseTCPAck(decr uint32)
  • func (p *Packet) DecreaseTCPSeq(decr uint32)
  • func (p *Packet) DropDetachedBytes()
  • func (p *Packet) DropDetachedDataBytes()
  • func (p *Packet) FixupIPHdrOnDataModify(old, new uint16)
  • func (p *Packet) FixupTCPHdrOnTCPDataAttach(tcpOptions []byte, tcpData []byte)
  • func (p *Packet) FixupTCPHdrOnTCPDataDetach(dataLength uint16, optionLength uint16)
  • func (p *Packet) GetBytes() []byte
  • func (p *Packet) GetIPLength() uint16
  • func (p *Packet) GetTCPData() []byte
  • func (p *Packet) GetTCPOptions() []byte
  • func (p *Packet) ID() string
  • func (p *Packet) IncreaseTCPAck(incr uint32)
  • func (p *Packet) IncreaseTCPSeq(incr uint32)
  • func (p *Packet) IsEmptyTCPPayload() bool
  • func (p *Packet) L4FlowHash() string
  • func (p *Packet) L4ReverseFlowHash() string
  • func (p *Packet) Print(context uint64)
  • func (p *Packet) ReadTCPData() []byte
  • func (p *Packet) ReadTCPDataString() string
  • func (p *Packet) SetTCPData(b []byte)
  • func (p *Packet) SourcePortHash(stage uint64) string
  • func (p *Packet) String() string
  • func (p *Packet) TCPDataAttach(tcpOptions []byte, tcpData []byte) (err error)
  • func (p *Packet) TCPDataDetach(optionLength uint16) (err error)
  • func (p *Packet) TCPDataLength() int
  • func (p *Packet) TCPDataStartBytes() uint16
  • func (p *Packet) TCPOptionLength() int
  • func (p *Packet) UpdateIPChecksum()
  • func (p *Packet) UpdateTCPChecksum()
  • func (p *Packet) VerifyIPChecksum() bool
  • func (p *Packet) VerifyTCPChecksum() bool

Constants

const (
	// IPProtocolTCP defines the constant for UDP protocol number
	IPProtocolTCP = 6

	// IPProtocolUDP defines the constant for UDP protocol number
	IPProtocolUDP = 17
)

IP Protocol numbers

const (

	// TCPSynMask is a mask for the TCP Syn flags
	TCPSynMask = 0x2

	// TCPSynAckMask  mask idenitifies a TCP SYN-ACK packet
	TCPSynAckMask = 0x12

	// TCPRstMask mask that identifies RST packets
	TCPRstMask = 0x4

	// TCPAckMask mask that identifies ACK packets
	TCPAckMask = 0x10

	// TCPFinMask mask that identifies FIN packets
	TCPFinMask = 0x1
)

TCP Header masks

const (
	// TCPAuthenticationOption is the option number will be using
	TCPAuthenticationOption = uint8(34)

	// TCPMssOption is the type for MSS option
	TCPMssOption = uint8(2)

	// TCPMssOptionLen is the type for MSS option
	TCPMssOptionLen = uint8(4)
)

TCP Options Related constants

const (
	// PacketTypeNetwork is enum for from-network packets
	PacketTypeNetwork = 0x1000
	// PacketTypeApplication is enum for from-application packets
	PacketTypeApplication = 0x2000

	// PacketStageIncoming is an enum for incoming stage
	PacketStageIncoming = 0x0100
	// PacketStageAuth is an enum for authentication stage
	PacketStageAuth = 0x0200
	// PacketStageService is an enum for crypto stage
	PacketStageService = 0x0400
	// PacketStageOutgoing is an enum for outgoing stage
	PacketStageOutgoing = 0x0800

	// PacketFailureCreate is the drop reason for packet
	PacketFailureCreate = 0x0010
	// PacketFailureAuth is a drop reason for packet due to authentication error
	PacketFailureAuth = 0x0020
	// PacketFailureService is a drop reason for packet due to crypto error
	PacketFailureService = 0x00040
)

const (

	// ipIDPos is location of IP Identifier
	IPIDPos = 4
)

IP Header field position constants

const (

	// TCPChecksumPos is the location of TCP checksum
	TCPChecksumPos = 36
)

TCP Header field position constants

Variables

var (
	// PacketLogLevel determines if packet logging is turned on
	PacketLogLevel bool
)

Functions

func TCPFlagsToStr

func TCPFlagsToStr(flags uint8) string

TCPFlagsToStr converts the TCP Flags to a string value that is human readable

Types

type Packet

type Packet struct {

	// Mark is the nfqueue Mark
	Mark string

	// Buffers : input/output buffer
	Buffer []byte

	IPProto       uint8
	IPTotalLength uint16

	SourceAddress      net.IP
	DestinationAddress net.IP

	// L4 Header Fields
	SourcePort      uint16
	DestinationPort uint16

	// TCP Specific fields
	TCPSeq uint32
	TCPAck uint32

	TCPFlags    uint8
	TCPChecksum uint16

	// Service Metadata
	SvcMetadata interface{}
	// Connection Metadata
	ConnectionMetadata interface{}
	// contains filtered or unexported fields
}

Packet is the main structure holding packet information

func New

func New(context uint64, bytes []byte, mark string) (packet *Packet, err error)

New returns a pointer to Packet structure built from the provided bytes buffer which is expected to contain valid TCP/IP packet bytes.

func (*Packet) CheckTCPAuthenticationOption

func (p *Packet) CheckTCPAuthenticationOption(iOptionLength int) (err error)

CheckTCPAuthenticationOption ensures authentication option exists at the offset provided

func (*Packet) DecreaseTCPAck

func (p *Packet) DecreaseTCPAck(decr uint32)

DecreaseTCPAck decreases TCP ack number by decr

func (*Packet) DecreaseTCPSeq

func (p *Packet) DecreaseTCPSeq(decr uint32)

DecreaseTCPSeq decreases TCP seq number by decr

func (*Packet) DropDetachedBytes

func (p *Packet) DropDetachedBytes()

DropDetachedBytes removes any bytes that have been detached and stored locally

func (*Packet) DropDetachedDataBytes

func (p *Packet) DropDetachedDataBytes()

DropDetachedDataBytes removes any bytes that have been detached and stored locally

func (*Packet) FixupIPHdrOnDataModify

func (p *Packet) FixupIPHdrOnDataModify(old, new uint16)

FixupIPHdrOnDataModify modifies the IP header fields and checksum

func (*Packet) FixupTCPHdrOnTCPDataAttach

func (p *Packet) FixupTCPHdrOnTCPDataAttach(tcpOptions []byte, tcpData []byte)

FixupTCPHdrOnTCPDataAttach modifies the TCP header fields and checksum

func (*Packet) FixupTCPHdrOnTCPDataDetach

func (p *Packet) FixupTCPHdrOnTCPDataDetach(dataLength uint16, optionLength uint16)

FixupTCPHdrOnTCPDataDetach modifies the TCP header fields and checksum

func (*Packet) GetBytes

func (p *Packet) GetBytes() []byte

GetBytes returns the bytes in the packet. It consolidates in case of changes as well

func (*Packet) GetIPLength

func (p *Packet) GetIPLength() uint16

GetIPLength returns the IP length

func (*Packet) GetTCPData

func (p *Packet) GetTCPData() []byte

GetTCPData returns any additional data in the packet

func (*Packet) GetTCPOptions

func (p *Packet) GetTCPOptions() []byte

GetTCPOptions returns any additional options in the packet

func (*Packet) ID

func (p *Packet) ID() string

ID returns the IP ID of the packet

func (*Packet) IncreaseTCPAck

func (p *Packet) IncreaseTCPAck(incr uint32)

IncreaseTCPAck increases TCP ack number by incr

func (*Packet) IncreaseTCPSeq

func (p *Packet) IncreaseTCPSeq(incr uint32)

IncreaseTCPSeq increases TCP seq number by incr

func (*Packet) IsEmptyTCPPayload

func (p *Packet) IsEmptyTCPPayload() bool

IsEmptyTCPPayload returns the TCP data offset

func (*Packet) L4FlowHash

func (p *Packet) L4FlowHash() string

L4FlowHash calculate a hash string based on the 4-tuple

func (*Packet) L4ReverseFlowHash

func (p *Packet) L4ReverseFlowHash() string

L4ReverseFlowHash calculate a hash string based on the 4-tuple by reversing source and destination information

func (*Packet) Print

func (p *Packet) Print(context uint64)

Print is a print helper function

func (*Packet) ReadTCPData

func (p *Packet) ReadTCPData() []byte

ReadTCPData returns ths payload in a string variable It does not remove the payload from the packet

func (*Packet) ReadTCPDataString

func (p *Packet) ReadTCPDataString() string

ReadTCPDataString returns ths payload in a string variable It does not remove the payload from the packet

func (*Packet) SetTCPData

func (p *Packet) SetTCPData(b []byte)

SetTCPData returns any additional data in the packet

func (*Packet) SourcePortHash

func (p *Packet) SourcePortHash(stage uint64) string

SourcePortHash calculates a hash based on dest ip/port for net packet and src ip/port for app packet.

func (*Packet) String

func (p *Packet) String() string

String returns a string representation of fields contained in this packet.

func (*Packet) TCPDataAttach

func (p *Packet) TCPDataAttach(tcpOptions []byte, tcpData []byte) (err error)

TCPDataAttach modifies the TCP and IP header fields and checksum

func (*Packet) TCPDataDetach

func (p *Packet) TCPDataDetach(optionLength uint16) (err error)

TCPDataDetach performs the following:

• Removes all TCP data from Buffer to TCPData.
• Removes "optionLength" bytes of options from TCP header to tcpOptions
• Updates IP Hdr (lengths, checksums)
• Updates TCP header (checksums)

func (*Packet) TCPDataLength

func (p *Packet) TCPDataLength() int

TCPDataLength -- returns the length of tcp options

func (*Packet) TCPDataStartBytes

func (p *Packet) TCPDataStartBytes() uint16

TCPDataStartBytes provides the tcp data start offset in bytes

func (*Packet) TCPOptionLength

func (p *Packet) TCPOptionLength() int

TCPOptionLength returns the length of tcpoptions

func (*Packet) UpdateIPChecksum

func (p *Packet) UpdateIPChecksum()

UpdateIPChecksum computes the IP header checksum and updates the packet with the value.

func (*Packet) UpdateTCPChecksum

func (p *Packet) UpdateTCPChecksum()

UpdateTCPChecksum computes the TCP header checksum and updates the packet with the value.

func (*Packet) VerifyIPChecksum

func (p *Packet) VerifyIPChecksum() bool

VerifyIPChecksum returns true if the IP header checksum is correct for this packet, false otherwise. Note that the checksum is not modified.

func (*Packet) VerifyTCPChecksum

func (p *Packet) VerifyTCPChecksum() bool

VerifyTCPChecksum returns true if the TCP header checksum is correct for this packet, false otherwise. Note that the checksum is not modified.