routes.go
func (r *routes) Broadcast(name PeerName) []PeerName {
	return r.lookupOrCalculate(name, &r.broadcast, true)
}
func (r *routes) Broadcast(name PeerName) []PeerName {
	return r.lookupOrCalculate(name, &r.broadcast, true)
}
// Broadcast returns the set of peer names that should be notified
// when we receive a broadcast message originating from the named peer
// based on established and symmetric connections.