peer.go
func (peer *Peer) routes(stopAt *Peer, establishedAndSymmetric bool) (bool, map[PeerName]PeerName) {
	routes := make(unicastRoutes)
	routes[peer.Name] = UnknownPeerName
	nextWorklist := []*Peer{peer}
	for len(nextWorklist) > 0 {
		worklist := nextWorklist
		sort.Sort(listOfPeers(worklist))
		nextWorklist = []*Peer{}
		for _, curPeer := range worklist {
			if curPeer == stopAt {
				return true, routes
			}
			curPeer.forEachConnectedPeer(establishedAndSymmetric, routes,
				func(remotePeer *Peer) {
					nextWorklist = append(nextWorklist, remotePeer)
					remoteName := remotePeer.Name
					// We now know how to get to remoteName: the same
					// way we get to curPeer. Except, if curPeer is
					// the starting peer in which case we know we can
					// reach remoteName directly.
					if curPeer == peer {
						routes[remoteName] = remoteName
					} else {
						routes[remoteName] = routes[curPeer.Name]
					}
				})
		}
	}
	return false, routes
}
func (peer *Peer) routes(stopAt *Peer, establishedAndSymmetric bool) (bool, map[PeerName]PeerName) {
	routes := make(unicastRoutes)
	routes[peer.Name] = UnknownPeerName
	nextWorklist := []*Peer{peer}
	for len(nextWorklist) > 0 {
		worklist := nextWorklist
		sort.Sort(listOfPeers(worklist))
		nextWorklist = []*Peer{}
		for _, curPeer := range worklist {
			if curPeer == stopAt {
				return true, routes
			}
			curPeer.forEachConnectedPeer(establishedAndSymmetric, routes,
				func(remotePeer *Peer) {
					nextWorklist = append(nextWorklist, remotePeer)
					remoteName := remotePeer.Name
					// We now know how to get to remoteName: the same
					// way we get to curPeer. Except, if curPeer is
					// the starting peer in which case we know we can
					// reach remoteName directly.
					if curPeer == peer {
						routes[remoteName] = remoteName
					} else {
						routes[remoteName] = routes[curPeer.Name]
					}
				})
		}
	}
	return false, routes
}
// Routes calculates the routing table from this peer to all peers reachable
// from it, returning a "next hop" map of PeerNameX -> PeerNameY, which says
// "in order to send a message to X, the peer should send the message to its
// neighbour Y".
//
// Because currently we do not have weightings on the connections between
// peers, there is no need to use a minimum spanning tree algorithm. Instead
// we employ the simpler and cheaper breadth-first widening. The computation
// is deterministic, which ensures that when it is performed on the same data
// by different peers, they get the same result. This is important since
// otherwise we risk message loss or routing cycles.
//
// When the 'establishedAndSymmetric' flag is set, only connections that are
// marked as 'established' and are symmetric (i.e. where both sides indicate
// they have a connection to the other) are considered.
//
// When a non-nil stopAt peer is supplied, the widening stops when it reaches
// that peer. The boolean return indicates whether that has happened.
//
// NB: This function should generally be invoked while holding a read lock on
// Peers and LocalPeer.