wire

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 Go to latest Published: Oct 4, 2025 License: MPL-2.0 Imports: 10 Imported by: 0

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Index

Constants

View Source 
const (
	Version4 = 4
	Version6 = 6
)

Valid Version values.

View Source 
const IP4HeaderLength = 20

IP4HeaderLength is the length of an IPv4 header with no IP options.

View Source 
const IP4SrcAddrOffset = 12
View Source 
const IP6HeaderLength = 40

IP6HeaderLength is the length of an IPv6 header with no IP options.

View Source 
const IP6SrcAddrOffset = 9
View Source 
const MinTCPHeaderSize = 20

Variables

View Source 
var (
	// PreferredNames is the set of protocol names that re produced by
	// MarshalText, and are the preferred representation.
	PreferredNames = map[Proto]string{
		51:     "ah",
		DCCP:   "dccp",
		8:      "egp",
		50:     "esp",
		47:     "gre",
		ICMPv4: "icmp",
		IGMP:   "igmp",
		9:      "igp",
		4:      "ipv4",
		ICMPv6: "ipv6-icmp",
		SCTP:   "sctp",
		TCP:    "tcp",
		UDP:    "udp",
	}

	// AcceptedNames is the set of protocol names that are accepted by
	// UnmarshalText.
	AcceptedNames = map[string]Proto{
		"ah":        51,
		"dccp":      DCCP,
		"egp":       8,
		"esp":       50,
		"gre":       47,
		"icmp":      ICMPv4,
		"icmpv4":    ICMPv4,
		"icmpv6":    ICMPv6,
		"igmp":      IGMP,
		"igp":       9,
		"ip-in-ip":  4,
		"ipv4":      4,
		"ipv6-icmp": ICMPv6,
		"sctp":      SCTP,
		"tcp":       TCP,
		"tsmp":      TSMP,
		"udp":       UDP,
	}
)

Prefer names from https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml unless otherwise noted.

View Source 
var Pool = ParsedPool{New: func() any { return new(Parsed) }}

Pool holds a pool of Parsed structs for use in filtering.

Functions

func Generate 

func Generate(h Header, payload []byte) []byte

Generate generates a new packet with the given Header and payload. This function allocates memory, see Header.Marshal for an allocation-free option.

func Hexdump 

func Hexdump(b []byte) string

func UpdateDstAddr 

func UpdateDstAddr(q *Parsed, dst netip.Addr)

UpdateDstAddr updates the destination address in the packet buffer (e.g. during DNAT). It also updates the checksum. Currently (2022-12-10) only TCP/UDP/ICMP is supported. It panics if provided with an address in a different family to the parsed packet.

func UpdateSrcAddr 

func UpdateSrcAddr(q *Parsed, src netip.Addr)

UpdateSrcAddr updates the source address in the packet buffer (e.g. during SNAT). It also updates the checksum. Currently (2023-09-22) only TCP/UDP/ICMP is supported. It panics if provided with an address in a different family to the parsed packet.

Types

type CaptureMeta 

type CaptureMeta struct {
	DidSNAT     bool           // SNAT was performed & the address was updated.
	OriginalSrc netip.AddrPort // The source address before SNAT was performed.
	DidDNAT     bool           // DNAT was performed & the address was updated.
	OriginalDst netip.AddrPort // The destination address before DNAT was performed.
}

CaptureMeta contains metadata that is used when debugging. 

type Header interface {
	// Len returns the length of the marshaled packet.
	Len() int
	// Marshal serializes the header into buf, which must be at
	// least Len() bytes long. Implementations of Marshal assume
	// that bytes after the first Len() are payload bytes for the
	// purpose of computing length and checksum fields. Marshal
	// implementations must not allocate memory.
	Marshal(buf []byte) error
}

Header is a packet header capable of marshaling itself into a byte buffer.

type HeaderChecksummer 

type HeaderChecksummer interface {
	Header

	// WriteCheck writes the correct checksum into buf, which should
	// be be the already-marshalled header and payload.
	WriteChecksum(buf []byte)
}

HeaderChecksummer is implemented by Header implementations that need to do a checksum over their payloads.

type ICMP4Code 

type ICMP4Code uint8

ICMP4Code is an ICMPv4 code, as specified in https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml 

const (
	ICMP4NoCode ICMP4Code = 0
)

type ICMP4Header 

type ICMP4Header struct {
	IP4Header
	Type ICMP4Type
	Code ICMP4Code
}

ICMP4Header is an IPv4+ICMPv4 header.

func (ICMP4Header) Len 

func (h ICMP4Header) Len() int

Len implements Header.

func (ICMP4Header) Marshal 

func (h ICMP4Header) Marshal(buf []byte) error

Marshal implements Header.

func (*ICMP4Header) ToResponse 

func (h *ICMP4Header) ToResponse()

ToResponse implements Header. TODO: it doesn't implement it correctly, instead it statically generates an ICMP Echo Reply packet.

type ICMP4Type 

type ICMP4Type uint8

ICMP4Type is an ICMPv4 type, as specified in https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml 

const (
	ICMP4EchoReply    ICMP4Type = 0x00
	ICMP4EchoRequest  ICMP4Type = 0x08
	ICMP4Unreachable  ICMP4Type = 0x03
	ICMP4TimeExceeded ICMP4Type = 0x0b
	ICMP4ParamProblem ICMP4Type = 0x12
)

func (ICMP4Type) String 

func (t ICMP4Type) String() string

type ICMP6Code 

type ICMP6Code uint8

ICMP6Code is an ICMPv6 code, as specified in https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml 

const (
	ICMP6NoCode ICMP6Code = 0
)

type ICMP6Header 

type ICMP6Header struct {
	IP6Header
	Type ICMP6Type
	Code ICMP6Code
}

ICMP6Header is an IPv4+ICMPv4 header.

func (ICMP6Header) Len 

func (h ICMP6Header) Len() int

Len implements Header.

func (ICMP6Header) Marshal 

func (h ICMP6Header) Marshal(buf []byte) error

Marshal implements Header.

func (*ICMP6Header) ToResponse 

func (h *ICMP6Header) ToResponse()

ToResponse implements Header. TODO: it doesn't implement it correctly, instead it statically generates an ICMP Echo Reply packet.

func (ICMP6Header) WriteChecksum 

func (h ICMP6Header) WriteChecksum(p []byte)

WriteChecksum implements HeaderChecksummer, writing just the checksum bytes into the otherwise fully marshaled ICMP6 packet p (which should include the IPv6 header, ICMPv6 header, and payload).

type ICMP6Type 

type ICMP6Type uint8

ICMP6Type is an ICMPv6 type, as specified in https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml 

const (
	ICMP6Unreachable  ICMP6Type = 1
	ICMP6PacketTooBig ICMP6Type = 2
	ICMP6TimeExceeded ICMP6Type = 3
	ICMP6ParamProblem ICMP6Type = 4
	ICMP6EchoRequest  ICMP6Type = 128
	ICMP6EchoReply    ICMP6Type = 129
)

func (ICMP6Type) String 

func (t ICMP6Type) String() string

type IP4Header 

type IP4Header struct {
	IPProto Proto
	IPID    uint16
	Src     netip.Addr
	Dst     netip.Addr
}

IP4Header represents an IPv4 packet header.

func (IP4Header) Len 

func (h IP4Header) Len() int

Len implements Header.

func (IP4Header) Marshal 

func (h IP4Header) Marshal(buf []byte) error

Marshal implements Header.

func (*IP4Header) ToResponse 

func (h *IP4Header) ToResponse()

ToResponse implements Header.

type IP6Header 

type IP6Header struct {
	IPProto Proto
	IPID    uint32 // only lower 20 bits used
	Src     netip.Addr
	Dst     netip.Addr
}

IP6Header represents an IPv6 packet header.

func (IP6Header) Len 

func (h IP6Header) Len() int

Len implements Header.

func (IP6Header) Marshal 

func (h IP6Header) Marshal(buf []byte) error

Marshal implements Header.

func (*IP6Header) ToResponse 

func (h *IP6Header) ToResponse()

ToResponse implements Header.

type Parsed 

type Parsed struct {

	// IPVersion is the IP protocol version of the packet (4 or
	// 6), or 0 if the packet doesn't look like IPv4 or IPv6.
	IPVersion uint8
	// IPProto is the IP subprotocol (UDP, TCP, etc.). Valid iff IPVersion != 0.
	IPProto Proto
	// Src is the source address. Family matches IPVersion. Port is
	// valid iff IPProto == TCP || IPProto == UDP || IPProto == SCTP.
	Src netip.AddrPort
	// Dst is the destination address. Family matches IPVersion. Port is
	// valid iff IPProto == TCP || IPProto == UDP || IPProto == SCTP.
	Dst netip.AddrPort
	// TCPFlags is the packet's TCP flag bits. Valid iff IPProto == TCP.
	TCPFlags TCPFlag

	// CaptureMeta contains metadata that is used when debugging.
	CaptureMeta CaptureMeta
	// contains filtered or unexported fields
}

Parsed is a minimal decoding of a packet suitable for use in filters.

func (*Parsed) Buffer 

func (q *Parsed) Buffer() []byte

Buffer returns the entire packet buffer. This is a read-only view; that is, q retains the ownership of the buffer.

func (*Parsed) Decode 

func (q *Parsed) Decode(b []byte)

Decode extracts data from the packet in b into q. It performs extremely simple packet decoding for basic IPv4 and IPv6 packet types. It extracts only the subprotocol id, IP addresses, and (if any) ports, and shouldn't need any memory allocation.

func (*Parsed) EchoIDSeq 

func (q *Parsed) EchoIDSeq() uint32

EchoIDSeq extracts the identifier/sequence bytes from an ICMP Echo response, and returns them as a uint32, used to lookup internally routed ICMP echo responses. This function is intentionally lightweight as it is called on every incoming ICMP packet.

func (*Parsed) ICMP4Header 

func (q *Parsed) ICMP4Header() ICMP4Header

func (*Parsed) ICMP6Header 

func (q *Parsed) ICMP6Header() ICMP6Header

func (*Parsed) IP4Header 

func (q *Parsed) IP4Header() IP4Header

func (*Parsed) IP6Header 

func (q *Parsed) IP6Header() IP6Header

func (*Parsed) IsEchoRequest 

func (q *Parsed) IsEchoRequest() bool

IsEchoRequest reports whether q is an ICMP Echo Request.

func (*Parsed) IsEchoResponse 

func (q *Parsed) IsEchoResponse() bool

IsEchoResponse reports whether q is an IPv4 ICMP Echo Response.

func (*Parsed) IsError 

func (q *Parsed) IsError() bool

IsError reports whether q is an ICMP "Error" packet.

func (*Parsed) IsTCPSyn 

func (q *Parsed) IsTCPSyn() bool

IsTCPSyn reports whether q is a TCP SYN packet, without ACK set. (i.e. the first packet in a new connection)

func (*Parsed) Payload 

func (q *Parsed) Payload() []byte

Payload returns the payload of the IP subprotocol section. This is a read-only view; that is, q retains the ownership of the buffer.

func (*Parsed) String 

func (p *Parsed) String() string

func (*Parsed) Transport 

func (p *Parsed) Transport() []byte

Transport returns the transport header and payload (IP subprotocol, such as TCP or UDP). This is a read-only view; that is, p retains the ownership of the buffer.

func (*Parsed) UDP4Header 

func (q *Parsed) UDP4Header() UDP4Header

type ParsedPool 

type ParsedPool sync.Pool

func (*ParsedPool) Get 

func (p *ParsedPool) Get() *Parsed

func (*ParsedPool) Put 

func (p *ParsedPool) Put(parsed *Parsed)

type Proto 

type Proto uint8

Proto is an IP subprotocol as defined by the IANA protocol numbers list (https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml), or the special values Unknown or Fragment. 

const (
	// Unknown represents an unknown or unsupported protocol; it's
	// deliberately the zero value. Strictly speaking the zero
	// value is IPv6 hop-by-hop extensions, but we don't support
	// those, so this is still technically correct.
	UnknownProto Proto = 0x00

	// Values from the IANA registry.
	ICMPv4 Proto = 0x01
	IGMP   Proto = 0x02
	ICMPv6 Proto = 0x3a
	TCP    Proto = 0x06
	UDP    Proto = 0x11
	DCCP   Proto = 0x21
	GRE    Proto = 0x2f
	SCTP   Proto = 0x84

	// TSMP is the Tailscale Message Protocol (our ICMP-ish
	// thing), an IP protocol used only between Tailscale nodes
	// (still encrypted by WireGuard) that communicates why things
	// failed, etc.
	//
	// Proto number 99 is reserved for "any private encryption
	// scheme". We never accept these from the host OS stack nor
	// send them to the host network stack. It's only used between
	// nodes.
	TSMP Proto = 99

	// Fragment represents any non-first IP fragment, for which we
	// don't have the sub-protocol header (and therefore can't
	// figure out what the sub-protocol is).
	//
	// 0xFF is reserved in the IANA registry, so we steal it for
	// internal use.
	Fragment Proto = 0xFF
)

func (Proto) String deprecated 

func (p Proto) String() string

Deprecated: use MarshalText instead.

type TCPFlag 

type TCPFlag uint8
const (
	TCPFlagsOffset = 13

	TCPFin     TCPFlag = 0x01
	TCPSyn     TCPFlag = 0x02
	TCPRst     TCPFlag = 0x04
	TCPPsh     TCPFlag = 0x08
	TCPAck     TCPFlag = 0x10
	TCPUrg     TCPFlag = 0x20
	TCPECNEcho TCPFlag = 0x40
	TCPCWR     TCPFlag = 0x80
	TCPSynAck  TCPFlag = TCPSyn | TCPAck
	TCPECNBits TCPFlag = TCPECNEcho | TCPCWR
)

type UDP4Header 

type UDP4Header struct {
	IP4Header
	SrcPort uint16
	DstPort uint16
}

UDP4Header is an IPv4+UDP header.

func (UDP4Header) Len 

func (h UDP4Header) Len() int

Len implements Header.

func (UDP4Header) Marshal 

func (h UDP4Header) Marshal(buf []byte) error

Marshal implements Header.

func (*UDP4Header) ToResponse 

func (h *UDP4Header) ToResponse()

ToResponse implements Header.

type UDP6Header 

type UDP6Header struct {
	IP6Header
	SrcPort uint16
	DstPort uint16
}

UDP6Header is an IPv6+UDP header.

func (UDP6Header) Len 

func (h UDP6Header) Len() int

Len implements Header.

func (UDP6Header) Marshal 

func (h UDP6Header) Marshal(buf []byte) error

Marshal implements Header.

func (*UDP6Header) ToResponse 

func (h *UDP6Header) ToResponse()

ToResponse implements Header.

type Version 

type Version uint8

Version describes the IP address version.

func (Version) String 

func (p Version) String() string

Source Files

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