From 0f8b13dc6d58c4e04a5e06c05b97a03281601ba1 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Sat, 12 Jul 2014 01:24:01 +1000
Subject: [PATCH] dht: Reply to get_peers and find_node queries

---
 dht/dht.go | 107 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 88 insertions(+), 19 deletions(-)

diff --git a/dht/dht.go b/dht/dht.go
index 372f7848..16e4a20b 100644
--- a/dht/dht.go
+++ b/dht/dht.go
@@ -22,7 +22,7 @@ type Server struct {
 	Socket           *net.UDPConn
 	transactions     []*transaction
 	transactionIDInt uint64
-	nodes            map[string]*Node
+	nodes            map[string]*Node // Keyed by *net.UDPAddr.String().
 	mu               sync.Mutex
 	closed           chan struct{}
 }
@@ -38,6 +38,14 @@ type Node struct {
 	lastSentTo    time.Time
 }
 
+func (n *Node) NodeInfo() (ret NodeInfo) {
+	ret.Addr = n.addr
+	if n := copy(ret.ID[:], n.id); n != 20 {
+		panic(n)
+	}
+	return
+}
+
 func (n *Node) Good() bool {
 	if len(n.id) != 20 {
 		return false
@@ -134,7 +142,7 @@ func (s *Server) Serve() error {
 		}
 		t := s.findResponseTransaction(d["t"].(string), addr)
 		if t == nil {
-			log.Printf("unexpected message: %#v", d)
+			//log.Printf("unexpected message: %#v", d)
 			s.mu.Unlock()
 			continue
 		}
@@ -159,22 +167,76 @@ func (s *Server) AddNode(ni NodeInfo) {
 	}
 }
 
+func (s *Server) nodeByID(id string) *Node {
+	for _, node := range s.nodes {
+		if node.id == id {
+			return node
+		}
+	}
+	return nil
+}
+
 func (s *Server) handleQuery(source *net.UDPAddr, m Msg) {
-	if m["q"] != "ping" {
+	args := m["a"].(map[string]interface{})
+	s.heardFromNode(source, args["id"].(string))
+	switch m["q"] {
+	case "ping":
+		s.reply(source, m["t"].(string), nil)
+	case "get_peers":
+		targetID := args["info_hash"].(string)
+		var rNodes []NodeInfo
+		// TODO: Reply with "values" list if we have peers instead.
+		for _, node := range s.closestGoodNodes(8, targetID) {
+			rNodes = append(rNodes, node.NodeInfo())
+		}
+		nodesBytes := make([]byte, CompactNodeInfoLen*len(rNodes))
+		for i, ni := range rNodes {
+			err := ni.PutCompact(nodesBytes[i*CompactNodeInfoLen : (i+1)*CompactNodeInfoLen])
+			if err != nil {
+				panic(err)
+			}
+		}
+		s.reply(source, m["t"].(string), map[string]interface{}{
+			"nodes": string(nodesBytes),
+			"token": "hi",
+		})
+	case "find_node":
+		targetID := args["target"].(string)
+		var rNodes []NodeInfo
+		if node := s.nodeByID(targetID); node != nil {
+			rNodes = append(rNodes, node.NodeInfo())
+		} else {
+			for _, node := range s.closestGoodNodes(8, targetID) {
+				rNodes = append(rNodes, node.NodeInfo())
+			}
+		}
+		nodesBytes := make([]byte, CompactNodeInfoLen*len(rNodes))
+		for i, ni := range rNodes {
+			err := ni.PutCompact(nodesBytes[i*CompactNodeInfoLen : (i+1)*CompactNodeInfoLen])
+			if err != nil {
+				panic(err)
+			}
+		}
+		s.reply(source, m["t"].(string), map[string]interface{}{
+			"nodes": string(nodesBytes),
+		})
+	case "announce_peer":
+		log.Print(m)
+	default:
 		log.Printf("%s: not handling received query: q=%s", s, m["q"])
 		return
 	}
-	s.heardFromNode(source, m["a"].(map[string]interface{})["id"].(string))
-	s.reply(source, m["t"].(string))
 }
 
-func (s *Server) reply(addr *net.UDPAddr, t string) {
+func (s *Server) reply(addr *net.UDPAddr, t string, r map[string]interface{}) {
+	if r == nil {
+		r = make(map[string]interface{}, 1)
+	}
+	r["id"] = s.IDString()
 	m := map[string]interface{}{
 		"t": t,
 		"y": "r",
-		"r": map[string]string{
-			"id": s.IDString(),
-		},
+		"r": r,
 	}
 	b, err := bencode.Marshal(m)
 	if err != nil {
@@ -661,13 +723,20 @@ func idDistance(a, b string) (ret int) {
 	return
 }
 
-// func (s *Server) closestNodes(k int) (ret *closestNodes) {
-// 	heap.Init(ret)
-// 	for _, node := range s.nodes {
-// 		heap.Push(ret, node)
-// 		if ret.Len() > k {
-// 			heap.Pop(ret)
-// 		}
-// 	}
-// 	return
-// }
+func (s *Server) closestGoodNodes(k int, targetID string) []*Node {
+	sel := newKClosestNodesSelector(k, targetID)
+	idNodes := make(map[string]*Node, len(s.nodes))
+	for _, node := range s.nodes {
+		if !node.Good() {
+			continue
+		}
+		sel.Push(node.id)
+		idNodes[node.id] = node
+	}
+	ids := sel.IDs()
+	ret := make([]*Node, 0, len(ids))
+	for _, id := range ids {
+		ret = append(ret, idNodes[id])
+	}
+	return ret
+}