package yggdrasil import ( "fmt" "sort" "time" ) const dht_lookup_size = 16 // dhtInfo represents everything we know about a node in the DHT. // This includes its key, a cache of it's NodeID, coords, and timing/ping related info for deciding who/when to ping nodes for maintenance. type dhtInfo struct { nodeID_hidden *NodeID key boxPubKey coords []byte send time.Time // When we last sent a message recv time.Time // When we last received a message //pings int // Decide when to drop //throttle time.Duration // Time to wait before pinging a node to bootstrap buckets, increases exponentially from 1 second to 1 minute //bootstrapSend time.Time // The time checked/updated as part of throttle checks } // Returns the *NodeID associated with dhtInfo.key, calculating it on the fly the first time or from a cache all subsequent times. func (info *dhtInfo) getNodeID() *NodeID { if info.nodeID_hidden == nil { info.nodeID_hidden = getNodeID(&info.key) } return info.nodeID_hidden } // Request for a node to do a lookup. // Includes our key and coords so they can send a response back, and the destination NodeID we want to ask about. type dhtReq struct { Key boxPubKey // Key of whoever asked Coords []byte // Coords of whoever asked Dest NodeID // NodeID they're asking about } // Response to a DHT lookup. // Includes the key and coords of the node that's responding, and the destination they were asked about. // The main part is Infos []*dhtInfo, the lookup response. type dhtRes struct { Key boxPubKey // key of the sender Coords []byte // coords of the sender Dest NodeID Infos []*dhtInfo // response } // The main DHT struct. type dht struct { core *Core nodeID NodeID table map[NodeID]*dhtInfo peers chan *dhtInfo // other goroutines put incoming dht updates here reqs map[boxPubKey]map[NodeID]time.Time //rumorMill []dht_rumor } func (t *dht) init(c *Core) { // TODO t.core = c t.nodeID = *t.core.GetNodeID() t.peers = make(chan *dhtInfo, 1024) t.reset() } func (t *dht) reset() { t.reqs = make(map[boxPubKey]map[NodeID]time.Time) t.table = make(map[NodeID]*dhtInfo) } func (t *dht) lookup(nodeID *NodeID, allowWorse bool) []*dhtInfo { var results []*dhtInfo var successor *dhtInfo sTarget := t.nodeID.next() for infoID, info := range t.table { if allowWorse || dht_ordered(&t.nodeID, &infoID, nodeID) { results = append(results, info) } else { if successor == nil || dht_ordered(&sTarget, &infoID, successor.getNodeID()) { successor = info } } } sort.SliceStable(results, func(i, j int) bool { return dht_ordered(results[j].getNodeID(), results[i].getNodeID(), nodeID) }) if successor != nil { results = append([]*dhtInfo{successor}, results...) } if len(results) > dht_lookup_size { results = results[:dht_lookup_size] } return results } // Insert into table, preserving the time we last sent a packet if the node was already in the table, otherwise setting that time to now func (t *dht) insert(info *dhtInfo) { if *info.getNodeID() == t.nodeID { // This shouldn't happen, but don't crash or add it in case it does return panic("FIXME") } info.recv = time.Now() if oldInfo, isIn := t.table[*info.getNodeID()]; isIn { info.send = oldInfo.send } else { info.send = info.recv } t.table[*info.getNodeID()] = info } // Return true if first/second/third are (partially) ordered correctly // FIXME? maybe total ordering makes more sense func dht_ordered(first, second, third *NodeID) bool { var ordered bool for idx := 0; idx < NodeIDLen; idx++ { f, s, t := first[idx], second[idx], third[idx] switch { case f == s && s == t: continue case f <= s && s <= t: ordered = true // nothing wrapped around 0 case t <= f && f <= s: ordered = true // 0 is between second and third case s <= t && t <= f: ordered = true // 0 is between first and second } break } return ordered } // Reads a request, performs a lookup, and responds. // Update info about the node that sent the request. func (t *dht) handleReq(req *dhtReq) { // Send them what they asked for loc := t.core.switchTable.getLocator() coords := loc.getCoords() res := dhtRes{ Key: t.core.boxPub, Coords: coords, Dest: req.Dest, Infos: t.lookup(&req.Dest, false), } t.sendRes(&res, req) // Also add them to our DHT info := dhtInfo{ key: req.Key, coords: req.Coords, } // For bootstrapping to work, we need to add these nodes to the table t.insert(&info) } // Sends a lookup response to the specified node. func (t *dht) sendRes(res *dhtRes, req *dhtReq) { // Send a reply for a dhtReq bs := res.encode() shared := t.core.sessions.getSharedKey(&t.core.boxPriv, &req.Key) payload, nonce := boxSeal(shared, bs, nil) p := wire_protoTrafficPacket{ Coords: req.Coords, ToKey: req.Key, FromKey: t.core.boxPub, Nonce: *nonce, Payload: payload, } packet := p.encode() t.core.router.out(packet) } // Returns nodeID + 1 func (nodeID NodeID) next() NodeID { for idx := len(nodeID) - 1; idx >= 0; idx-- { nodeID[idx] += 1 if nodeID[idx] != 0 { break } } return nodeID } // Returns nodeID - 1 func (nodeID NodeID) prev() NodeID { for idx := len(nodeID) - 1; idx >= 0; idx-- { nodeID[idx] -= 1 if nodeID[idx] != 0xff { break } } return nodeID } // Reads a lookup response, checks that we had sent a matching request, and processes the response info. // This mainly consists of updating the node we asked in our DHT (they responded, so we know they're still alive), and deciding if we want to do anything with their responses func (t *dht) handleRes(res *dhtRes) { t.core.searches.handleDHTRes(res) reqs, isIn := t.reqs[res.Key] if !isIn { return } _, isIn = reqs[res.Dest] if !isIn { return } delete(reqs, res.Dest) rinfo := dhtInfo{ key: res.Key, coords: res.Coords, } t.insert(&rinfo) // Or at the end, after checking successor/predecessor? var successor *dhtInfo var predecessor *dhtInfo for infoID, info := range t.table { // Get current successor and predecessor if successor == nil || dht_ordered(&t.nodeID, &infoID, successor.getNodeID()) { successor = info } if predecessor == nil || dht_ordered(predecessor.getNodeID(), &infoID, &t.nodeID) { predecessor = info } } for _, info := range res.Infos { if *info.getNodeID() == t.nodeID { continue } // Skip self if _, isIn := t.table[*info.getNodeID()]; isIn { // TODO? don't skip if coords are different? continue } // Send a request to all better successors or predecessors // We could try sending to only the best, but then packet loss matters more if successor == nil || dht_ordered(&t.nodeID, info.getNodeID(), successor.getNodeID()) { t.ping(info, &t.nodeID) fmt.Println("pinging new successor", t.nodeID[:4], info.getNodeID()[:4], successor) } if predecessor == nil || dht_ordered(predecessor.getNodeID(), info.getNodeID(), &t.nodeID) { t.ping(info, &t.nodeID) fmt.Println("pinging new predecessor", t.nodeID[:4], info.getNodeID()[:4], predecessor) } } // TODO add everyting else to a rumor mill for later use? (when/how?) } // Sends a lookup request to the specified node. func (t *dht) sendReq(req *dhtReq, dest *dhtInfo) { // Send a dhtReq to the node in dhtInfo bs := req.encode() shared := t.core.sessions.getSharedKey(&t.core.boxPriv, &dest.key) payload, nonce := boxSeal(shared, bs, nil) p := wire_protoTrafficPacket{ Coords: dest.coords, ToKey: dest.key, FromKey: t.core.boxPub, Nonce: *nonce, Payload: payload, } packet := p.encode() t.core.router.out(packet) reqsToDest, isIn := t.reqs[dest.key] if !isIn { t.reqs[dest.key] = make(map[NodeID]time.Time) reqsToDest, isIn = t.reqs[dest.key] if !isIn { panic("This should never happen") } } reqsToDest[req.Dest] = time.Now() } func (t *dht) ping(info *dhtInfo, target *NodeID) { // Creates a req for the node at dhtInfo, asking them about the target (if one is given) or themself (if no target is given) if target == nil { target = info.getNodeID() } loc := t.core.switchTable.getLocator() coords := loc.getCoords() req := dhtReq{ Key: t.core.boxPub, Coords: coords, Dest: *target, } info.send = time.Now() t.sendReq(&req, info) } func (t *dht) doMaintenance() { // Ping successor, asking for their predecessor, and clean up old/expired info var successor *dhtInfo now := time.Now() for infoID, info := range t.table { if now.Sub(info.recv) > time.Minute { delete(t.table, infoID) } else if successor == nil || dht_ordered(&t.nodeID, &infoID, successor.getNodeID()) { successor = info } } if successor != nil && now.Sub(successor.send) > 6*time.Second { t.ping(successor, nil) } }