derp

Documentation

Overview

Package derp implements DERP, the Detour Encrypted Routing Protocol.

DERP routes packets to clients using curve25519 keys as addresses.

DERP is used by Tailscale nodes to proxy encrypted WireGuard packets through the Tailscale cloud servers when a direct path cannot be found or opened. DERP is a last resort. Both sides between very aggressive NATs, firewalls, no IPv6, etc? Well, DERP.

Index

• Constants
• type BytesSentRecv
• type Client
  • func NewClient(privateKey key.Private, nc Conn, brw *bufio.ReadWriter, logf logger.Logf, ...) (*Client, error)
  • func (c *Client) ClosePeer(target key.Public) error
  • func (c *Client) ForwardPacket(srcKey, dstKey key.Public, pkt []byte) (err error)
  • func (c *Client) NotePreferred(preferred bool) (err error)
  • func (c *Client) Recv() (m ReceivedMessage, err error)
  • func (c *Client) Send(dstKey key.Public, pkt []byte) error
  • func (c *Client) SendPong(data [8]byte) error
  • func (c *Client) ServerPublicKey() key.Public
  • func (c *Client) WatchConnectionChanges() error
• type ClientOpt
  • func CanAckPings(v bool) ClientOpt
  • func IsProber(v bool) ClientOpt
  • func MeshKey(key string) ClientOpt
  • func ServerPublicKey(key key.Public) ClientOpt
• type Conn
• type HealthMessage
• type KeepAliveMessage
• type PacketForwarder
• type PeerGoneMessage
• type PeerPresentMessage
• type PingMessage
• type ReceivedMessage
• type ReceivedPacket
• type Server
  • func NewServer(privateKey key.Private, logf logger.Logf) *Server
  • func (s *Server) Accept(nc Conn, brw *bufio.ReadWriter, remoteAddr string)
  • func (s *Server) AddPacketForwarder(dst key.Public, fwd PacketForwarder)
  • func (s *Server) Close() error
  • func (s *Server) ConsistencyCheck() error
  • func (s *Server) ExpVar() expvar.Var
  • func (s *Server) HasMeshKey() bool
  • func (s *Server) MeshKey() string
  • func (s *Server) MetaCert() []byte
  • func (s *Server) PrivateKey() key.Private
  • func (s *Server) PublicKey() key.Public
  • func (s *Server) RemovePacketForwarder(dst key.Public, fwd PacketForwarder)
  • func (s *Server) ServeDebugTraffic(w http.ResponseWriter, r *http.Request)
  • func (s *Server) SetMeshKey(v string)
  • func (s *Server) SetVerifyClient(v bool)
• type ServerInfoMessage
• type ServerRestartingMessage

Constants

const MaxPacketSize = 64 << 10

MaxPacketSize is the maximum size of a packet sent over DERP. (This only includes the data bytes visible to magicsock, not including its on-wire framing overhead)

const ProtocolVersion = 2

ProtocolVersion is bumped whenever there's a wire-incompatible change.

• version 1 (zero on wire): consistent box headers, in use by employee dev nodes a bit
• version 2: received packets have src addrs in frameRecvPacket at beginning

Types

type BytesSentRecv

type BytesSentRecv struct {
	Sent uint64
	Recv uint64
	// Key is the public key of the client which sent/received these bytes.
	Key key.Public
}

BytesSentRecv records the number of bytes that have been sent since the last traffic check for a given process, as well as the public key of the process sending those bytes.

type Client

type Client struct {
	// contains filtered or unexported fields
}

Client is a DERP client.

func NewClient

func NewClient(privateKey key.Private, nc Conn, brw *bufio.ReadWriter, logf logger.Logf, opts ...ClientOpt) (*Client, error)

func (*Client) ClosePeer

func (c *Client) ClosePeer(target key.Public) error

ClosePeer asks the server to close target's TCP connection. It's a fatal error if the client wasn't created using MeshKey.

func (*Client) ForwardPacket

func (c *Client) ForwardPacket(srcKey, dstKey key.Public, pkt []byte) (err error)

func (*Client) NotePreferred

func (c *Client) NotePreferred(preferred bool) (err error)

NotePreferred sends a packet that tells the server whether this client is the user's preferred server. This is only used in the server for stats.

func (*Client) Recv

func (c *Client) Recv() (m ReceivedMessage, err error)

Recv reads a message from the DERP server.

The returned message may alias memory owned by the Client; it should only be accessed until the next call to Client.

Once Recv returns an error, the Client is dead forever.

func (*Client) Send

func (c *Client) Send(dstKey key.Public, pkt []byte) error

Send sends a packet to the Tailscale node identified by dstKey.

It is an error if the packet is larger than 64KB.

func (*Client) SendPong

func (c *Client) SendPong(data [8]byte) error

func (*Client) ServerPublicKey

func (c *Client) ServerPublicKey() key.Public

ServerPublicKey returns the server's public key.

func (*Client) WatchConnectionChanges

func (c *Client) WatchConnectionChanges() error

WatchConnectionChanges sends a request to subscribe to the peer's connection list. It's a fatal error if the client wasn't created using MeshKey.

type ClientOpt

type ClientOpt interface {
	// contains filtered or unexported methods
}

ClientOpt is an option passed to NewClient.

func CanAckPings

func CanAckPings(v bool) ClientOpt

CanAckPings returns a ClientOpt to set whether it advertises to the server that it's capable of acknowledging ping requests.

func IsProber

func IsProber(v bool) ClientOpt

IsProber returns a ClientOpt to pass to the DERP server during connect to declare that this client is a a prober.

func MeshKey

func MeshKey(key string) ClientOpt

MeshKey returns a ClientOpt to pass to the DERP server during connect to get access to join the mesh.

An empty key means to not use a mesh key.

func ServerPublicKey

func ServerPublicKey(key key.Public) ClientOpt

ServerPublicKey returns a ClientOpt to declare that the server's DERP public key is known. If key is the zero value, the returned ClientOpt is a no-op.

type Conn

type Conn interface {
	io.WriteCloser

	SetDeadline(time.Time) error
	SetReadDeadline(time.Time) error
	SetWriteDeadline(time.Time) error
}

Conn is the subset of the underlying net.Conn the DERP Server needs. It is a defined type so that non-net connections can be used.

type HealthMessage

type HealthMessage struct {
	// Problem, if non-empty, is a description of why the connection
	// is unhealthy.
	//
	// The empty string means the connection is healthy again.
	//
	// The default condition is healthy, so the server doesn't
	// broadcast a HealthMessage until a problem exists.
	Problem string
}

HealthMessage is a one-way message from server to client, declaring the connection health state.

type KeepAliveMessage

type KeepAliveMessage struct{}

KeepAliveMessage is a one-way empty message from server to client, just to keep the connection alive. It's like a PingMessage, but doesn't solicit a reply from the client.

type PacketForwarder

type PacketForwarder interface {
	ForwardPacket(src, dst key.Public, payload []byte) error
}

PacketForwarder is something that can forward packets.

It's mostly an interface for circular dependency reasons; the typical implementation is derphttp.Client. The other implementation is a multiForwarder, which this package creates as needed if a public key gets more than one PacketForwarder registered for it.

type PeerGoneMessage

type PeerGoneMessage key.Public

PeerGoneMessage is a ReceivedMessage that indicates that the client identified by the underlying public key had previously sent you a packet but has now disconnected from the server.

type PeerPresentMessage

type PeerPresentMessage key.Public

PeerPresentMessage is a ReceivedMessage that indicates that the client is connected to the server. (Only used by trusted mesh clients)

type PingMessage

type PingMessage [8]byte

PingMessage is a request from a client or server to reply to the other side with a PongMessage with the given payload.

type ReceivedMessage

type ReceivedMessage interface {
	// contains filtered or unexported methods
}

ReceivedMessage represents a type returned by Client.Recv. Unless otherwise documented, the returned message aliases the byte slice provided to Recv and thus the message is only as good as that buffer, which is up to the caller.

type ReceivedPacket

type ReceivedPacket struct {
	Source key.Public
	// Data is the received packet bytes. It aliases the memory
	// passed to Client.Recv.
	Data []byte
}

ReceivedPacket is a ReceivedMessage representing an incoming packet.

type Server

type Server struct {
	// WriteTimeout, if non-zero, specifies how long to wait
	// before failing when writing to a client.
	WriteTimeout time.Duration
	// contains filtered or unexported fields
}

Server is a DERP server.

func NewServer

func NewServer(privateKey key.Private, logf logger.Logf) *Server

NewServer returns a new DERP server. It doesn't listen on its own. Connections are given to it via Server.Accept.

func (*Server) Accept

func (s *Server) Accept(nc Conn, brw *bufio.ReadWriter, remoteAddr string)

Accept adds a new connection to the server and serves it.

The provided bufio ReadWriter must be already connected to nc. Accept blocks until the Server is closed or the connection closes on its own.

Accept closes nc.

func (*Server) AddPacketForwarder

func (s *Server) AddPacketForwarder(dst key.Public, fwd PacketForwarder)

AddPacketForwarder registers fwd as a packet forwarder for dst. fwd must be comparable.

func (*Server) Close

func (s *Server) Close() error

Close closes the server and waits for the connections to disconnect.

func (*Server) ConsistencyCheck

func (s *Server) ConsistencyCheck() error

func (*Server) ExpVar

func (s *Server) ExpVar() expvar.Var

ExpVar returns an expvar variable suitable for registering with expvar.Publish.

func (*Server) HasMeshKey

func (s *Server) HasMeshKey() bool

HasMeshKey reports whether the server is configured with a mesh key.

func (*Server) MeshKey

func (s *Server) MeshKey() string

MeshKey returns the configured mesh key, if any.

func (*Server) MetaCert

func (s *Server) MetaCert() []byte

MetaCert returns the server metadata cert that can be sent by the TLS server to let the client skip a round trip during start-up.

func (*Server) PrivateKey

func (s *Server) PrivateKey() key.Private

PrivateKey returns the server's private key.

func (*Server) PublicKey

func (s *Server) PublicKey() key.Public

PublicKey returns the server's public key.

func (*Server) RemovePacketForwarder

func (s *Server) RemovePacketForwarder(dst key.Public, fwd PacketForwarder)

RemovePacketForwarder removes fwd as a packet forwarder for dst. fwd must be comparable.

func (*Server) ServeDebugTraffic

func (s *Server) ServeDebugTraffic(w http.ResponseWriter, r *http.Request)

func (*Server) SetMeshKey

func (s *Server) SetMeshKey(v string)

SetMesh sets the pre-shared key that regional DERP servers used to mesh amongst themselves.

It must be called before serving begins.

func (*Server) SetVerifyClient

func (s *Server) SetVerifyClient(v bool)

SetVerifyClients sets whether this DERP server verifies clients through tailscaled.

It must be called before serving begins.

type ServerInfoMessage

type ServerInfoMessage struct {
	// TokenBucketBytesPerSecond is how many bytes per second the
	// server says it will accept, including all framing bytes.
	//
	// Zero means unspecified. There might be a limit, but the
	// client need not try to respect it.
	TokenBucketBytesPerSecond int

	// TokenBucketBytesBurst is how many bytes the server will
	// allow to burst, temporarily violating
	// TokenBucketBytesPerSecond.
	//
	// Zero means unspecified. There might be a limit, but the
	// client need not try to respect it.
	TokenBucketBytesBurst int
}

ServerInfoMessage is sent by the server upon first connect.

type ServerRestartingMessage

type ServerRestartingMessage struct {
	// ReconnectIn is an advisory duration that the client should wait
	// before attempting to reconnect. It might be zero.
	// It exists for the server to smear out the reconnects.
	ReconnectIn time.Duration

	// TryFor is an advisory duration for how long the client
	// should attempt to reconnect before giving up and proceeding
	// with its normal connection failure logic. The interval
	// between retries is undefined for now.
	// A server should not send a TryFor duration more than a few
	// seconds.
	TryFor time.Duration
}

ServerRestartingMessage is a one-way message from server to client, advertising that the server is restarting.