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package mesh
import (
"net"
)
// Overlay yields OverlayConnections.
type Overlay interface {
// Enhance a features map with overlay-related features.
AddFeaturesTo(map[string]string)
// Prepare on overlay connection. The connection should remain
// passive until it has been Confirm()ed.
PrepareConnection(OverlayConnectionParams) (OverlayConnection, error)
// Obtain diagnostic information specific to the overlay.
Diagnostics() interface{}
}
// OverlayConnectionParams are used to set up overlay connections.
type OverlayConnectionParams struct {
RemotePeer *Peer
// The local address of the corresponding TCP connection. Used to
// derive the local IP address for sending. May differ for
// different overlay connections.
LocalAddr *net.TCPAddr
// The remote address of the corresponding TCP connection. Used to
// determine the address to send to, but only if the TCP
// connection is outbound. Otherwise the Overlay needs to discover
// it (e.g. from incoming datagrams).
RemoteAddr *net.TCPAddr
// Is the corresponding TCP connection outbound?
Outbound bool
// Unique identifier for this connection
ConnUID uint64
// Session key, if connection is encrypted; nil otherwise.
//
// NB: overlay connections must take care not to use nonces which
// may collide with those of the main connection. These nonces are
// 192 bits, with the top most bit unspecified, the next bit set
// to 1, followed by 126 zero bits, and a message sequence number
// in the lowest 64 bits.
SessionKey *[32]byte
// Function to send a control message to the counterpart
// overlay connection.
SendControlMessage func(tag byte, msg []byte) error
// Features passed at connection initiation
Features map[string]string
}
// OverlayConnection describes all of the machinery to manage overlay
// connectivity to a particular peer.
type OverlayConnection interface {
// Confirm that the connection is really wanted, and so the
// Overlay should begin heartbeats etc. to verify the operation of
// the overlay connection.
Confirm()
// EstablishedChannel returns a channel that will be closed when the
// overlay connection is established, i.e. its operation has been
// confirmed.
EstablishedChannel() <-chan struct{}
// ErrorChannel returns a channel that forwards errors from the overlay
// connection. The overlay connection is not expected to be operational
// after the first error, so the channel only needs to buffer a single
// error.
ErrorChannel() <-chan error
// Stop terminates the connection.
Stop()
// ControlMessage handles a message from the remote peer. 'tag' exists for
// compatibility, and should always be ProtocolOverlayControlMessage for
// non-sleeve overlays.
ControlMessage(tag byte, msg []byte)
// DisplayName returns the user-facing overlay name.
DisplayName() string
}
// NullOverlay implements Overlay and OverlayConnection with no-ops.
type NullOverlay struct{}
// AddFeaturesTo implements Overlay.
func (NullOverlay) AddFeaturesTo(map[string]string) {}
// PrepareConnection implements Overlay.
func (NullOverlay) PrepareConnection(OverlayConnectionParams) (OverlayConnection, error) {
return NullOverlay{}, nil
}
// Diagnostics implements Overlay.
func (NullOverlay) Diagnostics() interface{} { return nil }
// Confirm implements OverlayConnection.
func (NullOverlay) Confirm() {}
// EstablishedChannel implements OverlayConnection.
func (NullOverlay) EstablishedChannel() <-chan struct{} { return nil }
// ErrorChannel implements OverlayConnection.
func (NullOverlay) ErrorChannel() <-chan error { return nil }
// Stop implements OverlayConnection.
func (NullOverlay) Stop() {}
// ControlMessage implements OverlayConnection.
func (NullOverlay) ControlMessage(byte, []byte) {}
// DisplayName implements OverlayConnection.
func (NullOverlay) DisplayName() string { return "null" }
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