packet
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Documentation¶
Overview¶
Package packet contains packet parsing and marshaling utilities.
Parsed provides allocation-free minimal packet header decoding, foruse in packet filtering. The other types in the package are forconstructing and marshaling packets into []bytes.
To support allocation-free parsing, this package defines IPv4 andIPv6 address types. You should prefer to use netaddr's types,except where you absolutely need allocation-free IP handling(i.e. in the tunnel datapath) and are willing to implement allcodepaths and data structures twice, once per IP family.
Index¶
- func Generate(h Header, payload []byte) []byte
- func Hexdump(b []byte) string
- func ICMPEchoPayload(payload []byte) (idSeq uint32, buf []byte)
- type CaptureMeta
- type Header
- type HeaderChecksummer
- type ICMP4Code
- type ICMP4Header
- type ICMP4Type
- type ICMP6Code
- type ICMP6Header
- type ICMP6Type
- type IP4Header
- type IP6Header
- type Parsed
- func (pp *Parsed) AsTSMPPing() (h TSMPPingRequest, ok bool)
- func (pp *Parsed) AsTSMPPong() (pong TSMPPongReply, ok bool)
- func (pp *Parsed) AsTailscaleRejectedHeader() (h TailscaleRejectedHeader, ok bool)
- func (q *Parsed) Buffer() []byte
- func (q *Parsed) Decode(b []byte)
- func (q *Parsed) EchoIDSeq() uint32
- func (q *Parsed) ICMP4Header() ICMP4Header
- func (q *Parsed) ICMP6Header() ICMP6Header
- func (q *Parsed) IP4Header() IP4Header
- func (q *Parsed) IP6Header() IP6Header
- func (q *Parsed) IsEchoRequest() bool
- func (q *Parsed) IsEchoResponse() bool
- func (q *Parsed) IsError() bool
- func (q *Parsed) IsTCPSyn() bool
- func (q *Parsed) Payload() []byte
- func (p *Parsed) String() string
- func (q *Parsed) StuffForTesting(len int)
- func (p *Parsed) Transport() []byte
- func (q *Parsed) UDP4Header() UDP4Header
- type TCPFlag
- type TSMPPingRequest
- type TSMPPongReply
- type TSMPType
- type TailscaleRejectReason
- type TailscaleRejectedHeader
- type UDP4Header
- type UDP6Header
Constants¶
This section is empty.
Variables¶
This section is empty.
Functions¶
funcGenerate¶
Generate generates a new packet with the given Header andpayload. This function allocates memory, see Header.Marshal for anallocation-free option.
funcICMPEchoPayload¶added inv1.26.0
ICMPEchoPayload generates a new random ID/Sequence pair, and returns a uint32derived from them, along with the id, sequence and given payload in a buffer.It returns an error if the random source could not be read.
Types¶
typeCaptureMeta¶added inv1.40.0
type CaptureMeta struct {DidSNATbool// SNAT was performed & the address was updated.OriginalSrcnetip.AddrPort// The source address before SNAT was performed.DidDNATbool// DNAT was performed & the address was updated.OriginalDstnetip.AddrPort// The destination address before DNAT was performed.}CaptureMeta contains metadata that is used when debugging.
typeHeader¶
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 bytebuffer.
typeHeaderChecksummer¶added inv1.20.0
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 thatneed to do a checksum over their payloads.
typeICMP4Code¶
type ICMP4Codeuint8
ICMP4Code is an ICMPv4 code, as specified inhttps://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml
const (ICMP4NoCodeICMP4Code = 0)typeICMP4Header¶
ICMP4Header is an IPv4+ICMPv4 header.
func (*ICMP4Header)ToResponse¶
func (h *ICMP4Header) ToResponse()
ToResponse implements Header. TODO: it doesn't implement itcorrectly, instead it statically generates an ICMP Echo Replypacket.
typeICMP4Type¶
type ICMP4Typeuint8
ICMP4Type is an ICMPv4 type, as specified inhttps://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml
typeICMP6Code¶
type ICMP6Codeuint8
ICMP6Code is an ICMPv6 code, as specified inhttps://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml
const (ICMP6NoCodeICMP6Code = 0)typeICMP6Header¶added inv1.20.0
ICMP6Header is an IPv4+ICMPv4 header.
func (ICMP6Header)Marshal¶added inv1.20.0
func (hICMP6Header) Marshal(buf []byte)error
Marshal implements Header.
func (*ICMP6Header)ToResponse¶added inv1.20.0
func (h *ICMP6Header) ToResponse()
ToResponse implements Header. TODO: it doesn't implement itcorrectly, instead it statically generates an ICMP Echo Replypacket.
func (ICMP6Header)WriteChecksum¶added inv1.20.0
func (hICMP6Header) WriteChecksum(p []byte)
WriteChecksum implements HeaderChecksummer, writing just the checksum bytesinto the otherwise fully marshaled ICMP6 packet p (which should include theIPv6 header, ICMPv6 header, and payload).
typeICMP6Type¶
type ICMP6Typeuint8
ICMP6Type is an ICMPv6 type, as specified inhttps://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml
typeIP6Header¶
type IP6Header struct {IPProtoipproto.ProtoIPIDuint32// only lower 20 bits usedSrcnetip.AddrDstnetip.Addr}IP6Header represents an IPv6 packet header.
typeParsed¶
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.IPVersionuint8// IPProto is the IP subprotocol (UDP, TCP, etc.). Valid iff IPVersion != 0.IPProtoipproto.Proto// SrcIP4 is the source address. Family matches IPVersion. Port is// valid iff IPProto == TCP || IPProto == UDP.Srcnetip.AddrPort// DstIP4 is the destination address. Family matches IPVersion.Dstnetip.AddrPort// TCPFlags is the packet's TCP flag bits. Valid iff IPProto == TCP.TCPFlagsTCPFlag// CaptureMeta contains metadata that is used when debugging.CaptureMetaCaptureMeta// contains filtered or unexported fields}Parsed is a minimal decoding of a packet suitable for use in filters.
func (*Parsed)AsTSMPPing¶added inv1.8.0
func (pp *Parsed) AsTSMPPing() (hTSMPPingRequest, okbool)
func (*Parsed)AsTSMPPong¶added inv1.8.0
func (pp *Parsed) AsTSMPPong() (pongTSMPPongReply, okbool)
AsTSMPPong returns pp as a TSMPPongReply and whether it is one.The pong.IPHeader field is not populated.
func (*Parsed)AsTailscaleRejectedHeader¶
func (pp *Parsed) AsTailscaleRejectedHeader() (hTailscaleRejectedHeader, okbool)
AsTailscaleRejectedHeader parses pp as an incoming rejectionconnection TSMP message.
ok reports whether pp was a valid TSMP rejection packet.
func (*Parsed)Buffer¶
Buffer returns the entire packet buffer.This is a read-only view; that is, q retains the ownership of the buffer.
func (*Parsed)Decode¶
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¶added inv1.26.0
EchoIDSeq extracts the identifier/sequence bytes from an ICMP Echo response,and returns them as a uint32, used to lookup internally routed ICMP echoresponses. This function is intentionally lightweight as it is called onevery incoming ICMP packet.
func (*Parsed)ICMP4Header¶
func (q *Parsed) ICMP4Header()ICMP4Header
func (*Parsed)ICMP6Header¶added inv1.20.0
func (q *Parsed) ICMP6Header()ICMP6Header
func (*Parsed)IsEchoRequest¶
IsEchoRequest reports whether q is an ICMP Echo Request.
func (*Parsed)IsEchoResponse¶
IsEchoResponse reports whether q is an IPv4 ICMP Echo Response.
func (*Parsed)IsTCPSyn¶
IsTCPSyn reports whether q is a TCP SYN packet,without ACK set. (i.e. the first packet in a new connection)
func (*Parsed)Payload¶
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)StuffForTesting¶added inv1.6.0
StuffForTesting makes Parsed contain a len-bytes buffer. Used intests to build up a synthetic parse result with a non-zero buffer.
func (*Parsed)Transport¶added inv1.20.2
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
typeTSMPPingRequest¶added inv1.8.0
type TSMPPingRequest struct {Data [8]byte}TSMPPingRequest is a TSMP message that's like an ICMP ping request.
On the wire, after the IP header, it's currently 9 bytes:
- 'p' (TSMPTypePing)
- 8 opaque ping bytes to copy back in the response
typeTSMPPongReply¶added inv1.8.0
func (TSMPPongReply)Len¶added inv1.8.0
func (hTSMPPongReply) Len()int
func (TSMPPongReply)Marshal¶added inv1.8.0
func (hTSMPPongReply) Marshal(buf []byte)error
typeTailscaleRejectReason¶
type TailscaleRejectReasonbyte
const (// TailscaleRejectReasonNone is the TailscaleRejectReason zero value.TailscaleRejectReasonNoneTailscaleRejectReason = 0// RejectedDueToACLs means that the host rejected the connection due to ACLs.RejectedDueToACLsTailscaleRejectReason = 'A'// RejectedDueToShieldsUp means that the host rejected the connection due to shields being up.RejectedDueToShieldsUpTailscaleRejectReason = 'S'// RejectedDueToIPForwarding means that the relay node's IP// forwarding is disabled.RejectedDueToIPForwardingTailscaleRejectReason = 'F'// RejectedDueToHostFirewall means that the target host's// firewall is blocking the traffic.RejectedDueToHostFirewallTailscaleRejectReason = 'W')
func (TailscaleRejectReason)IsZero¶added inv1.4.3
func (rTailscaleRejectReason) IsZero()bool
IsZero reports whether r is the zero value, representing no rejection.
func (TailscaleRejectReason)String¶
func (rTailscaleRejectReason) String()string
typeTailscaleRejectedHeader¶
type TailscaleRejectedHeader struct {IPSrcnetip.Addr// IPv4 or IPv6 header's src IPIPDstnetip.Addr// IPv4 or IPv6 header's dst IPSrcnetip.AddrPort// rejected flow's srcDstnetip.AddrPort// rejected flow's dstProtoipproto.Proto// proto that was rejected (TCP or UDP)ReasonTailscaleRejectReason// why the connection was rejected// MaybeBroken is whether the rejection is non-terminal (the// client should not fail immediately). This is sent by a// target when it's not sure whether it's totally broken, but// it might be. For example, the target tailscaled might think// its host firewall or IP forwarding aren't configured// properly, but tailscaled might be wrong (not having enough// visibility into what the OS is doing). When true, the// message is simply an FYI as a potential reason to use for// later when the pendopen connection tracking timer expires.MaybeBrokenbool}TailscaleRejectedHeader is a TSMP message that says that oneTailscale node has rejected the connection from another. Unlike aTCP RST, this includes a reason.
On the wire, after the IP header, it's currently 7 or 8 bytes:
- '!'
- IPProto byte (IANA protocol number: TCP or UDP)
- 'A' or 'S' (RejectedDueToACLs, RejectedDueToShieldsUp)
- srcPort big endian uint16
- dstPort big endian uint16
- [optional] byte of flag bits:lowest bit (0x1): MaybeBroken
In the future it might also accept 16 byte IP flow src/dst IPsafter the header, if they're different than the IP-level ones.
func (TailscaleRejectedHeader)Flow¶
func (rhTailscaleRejectedHeader) Flow()flowtrack.Tuple
func (TailscaleRejectedHeader)Len¶
func (hTailscaleRejectedHeader) Len()int
func (TailscaleRejectedHeader)Marshal¶
func (hTailscaleRejectedHeader) Marshal(buf []byte)error
func (TailscaleRejectedHeader)String¶
func (rhTailscaleRejectedHeader) String()string
typeUDP4Header¶
UDP4Header is an IPv4+UDP header.
typeUDP6Header¶
UDP6Header is an IPv6+UDP header.
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