peerstore constructs peers

Now, all peers should be retrieved from the Peerstore, which will
construct the peers accordingly. This ensures there's only one peer
object per peer (opposite would be bad: things get out sync)

cc @whyrusleeping

dht.go

@@ -300,10 +300,9 @@ func (dht *IpfsDHT) addPeer(pb *Message_Peer) (*peer.Peer, error) {
 	}
 
 	// check if we already have this peer.
-	pr, _ := dht.peerstore.Get(peer.ID(pb.GetId()))
-	if pr == nil {
-		pr = &peer.Peer{ID: peer.ID(pb.GetId())}
-		dht.peerstore.Put(pr)
+	pr, err := dht.getPeer(peer.ID(pb.GetId()))
+	if err != nil {
+		return nil, err
 	}
 	pr.AddAddress(addr) // idempotent
 
@@ -481,6 +480,16 @@ func (dht *IpfsDHT) betterPeersToQuery(pmes *Message, count int) []*peer.Peer {
 	return filtered
 }
 
+func (dht *IpfsDHT) getPeer(id peer.ID) (*peer.Peer, error) {
+	p, err := dht.peerstore.Get(id)
+	if err != nil {
+		err = fmt.Errorf("Failed to get peer from peerstore: %s", err)
+		log.Error("%s", err)
+		return nil, err
+	}
+	return p, nil
+}
+
 func (dht *IpfsDHT) peerFromInfo(pbp *Message_Peer) (*peer.Peer, error) {
 
 	id := peer.ID(pbp.GetId())
@@ -490,26 +499,16 @@ func (dht *IpfsDHT) peerFromInfo(pbp *Message_Peer) (*peer.Peer, error) {
 		return nil, errors.New("found self")
 	}
 
-	p, _ := dht.peerstore.Get(id)
-	if p == nil {
-		p, _ = dht.FindLocal(id)
-		if p != nil {
-			panic("somehow peer not getting into peerstore")
-		}
+	p, err := dht.getPeer(id)
+	if err != nil {
+		return nil, err
 	}
 
-	if p == nil {
-		maddr, err := pbp.Address()
-		if err != nil {
-			return nil, err
-		}
-
-		// create new Peer
-		p = &peer.Peer{ID: id}
-		p.AddAddress(maddr)
-		dht.peerstore.Put(p)
-		log.Info("dht found new peer: %s %s", p, maddr)
+	maddr, err := pbp.Address()
+	if err != nil {
+		return nil, err
 	}
+	p.AddAddress(maddr)
 	return p, nil
 }
 
@@ -541,6 +540,7 @@ func (dht *IpfsDHT) loadProvidableKeys() error {
 	return nil
 }
 
+// PingRoutine periodically pings nearest neighbors.
 func (dht *IpfsDHT) PingRoutine(t time.Duration) {
 	tick := time.Tick(t)
 	for {