sniffer

Documentation

Overview

Package sniffer provides the implementation of data-link layer endpoints that wrap another endpoint and logs inbound and outbound packets.

Sniffer endpoints can be used in the networking stack by calling New(eID) to create a new endpoint, where eID is the ID of the endpoint being wrapped, and then passing it as an argument to Stack.CreateNIC().

Index

• Constants
• Variables
• func LogPacket(prefix string, dir Direction, protocol tcpip.NetworkProtocolNumber, ...)
• func New(lower stack.LinkEndpoint) stack.LinkEndpoint
• func NewWithPrefix(lower stack.LinkEndpoint, logPrefix string) stack.LinkEndpoint
• func NewWithWriter(lower stack.LinkEndpoint, writer io.Writer, snapLen uint32) (stack.LinkEndpoint, error)
• type Direction

Constants

const (
	// DirectionSend indicates a sent packet.
	DirectionSend = iota
	// DirectionRecv indicates a received packet.
	DirectionRecv
)

Variables

var LogPackets atomicbitops.Uint32 = atomicbitops.FromUint32(1)

LogPackets is a flag used to enable or disable packet logging via the log package. Valid values are 0 or 1.

var LogPacketsToPCAP atomicbitops.Uint32 = atomicbitops.FromUint32(1)

LogPacketsToPCAP is a flag used to enable or disable logging packets to a pcap writer. Valid values are 0 or 1. A writer must have been specified when the sniffer was created for this flag to have effect.

Functions

func LogPacket

func LogPacket(prefix string, dir Direction, protocol tcpip.NetworkProtocolNumber, pkt stack.PacketBufferPtr)

LogPacket logs a packet to stdout.

func New

func New(lower stack.LinkEndpoint) stack.LinkEndpoint

New creates a new sniffer link-layer endpoint. It wraps around another endpoint and logs packets and they traverse the endpoint.

func NewWithPrefix

func NewWithPrefix(lower stack.LinkEndpoint, logPrefix string) stack.LinkEndpoint

NewWithPrefix creates a new sniffer link-layer endpoint. It wraps around another endpoint and logs packets prefixed with logPrefix as they traverse the endpoint.

logPrefix is prepended to the log line without any separators. E.g. logPrefix = "NIC:en0/" will produce log lines like "NIC:en0/send udp [...]".

func NewWithWriter

func NewWithWriter(lower stack.LinkEndpoint, writer io.Writer, snapLen uint32) (stack.LinkEndpoint, error)

NewWithWriter creates a new sniffer link-layer endpoint. It wraps around another endpoint and logs packets as they traverse the endpoint.

Each packet is written to writer in the pcap format in a single Write call without synchronization. A sniffer created with this function will not emit packets using the standard log package.

snapLen is the maximum amount of a packet to be saved. Packets with a length less than or equal to snapLen will be saved in their entirety. Longer packets will be truncated to snapLen.

Types

type Direction

type Direction int

A Direction indicates whether the packing is being sent or received.