Squash some more debug messages, fix some other error handling

client.go

@@ -353,7 +353,7 @@ func (me *Client) runConnection(sock net.Conn, torrent *torrent, discovery peerS
 		return
 	}
 	if string(b[:20]) != pp.Protocol {
-		err = fmt.Errorf("wrong protocol: %#v", string(b[:20]))
+		// err = fmt.Errorf("wrong protocol: %#v", string(b[:20]))
 		return
 	}
 	if 8 != copy(conn.PeerExtensions[:], b[20:]) {
@@ -951,7 +951,7 @@ func (cl *Client) announceTorrentDHT(t *torrent) {
 					log.Printf("error adding peers from dht for torrent %q: %s", t, err)
 					break getPeers
 				}
-				log.Printf("got %d peers from dht for torrent %q", len(cps), t)
+				// log.Printf("got %d peers from dht for torrent %q", len(cps), t)
 			}
 		}
 		ps.Close()

dht/dht.go

@@ -3,7 +3,6 @@ package dht
 import (
 	"bitbucket.org/anacrolix/go.torrent/tracker"
 	"bitbucket.org/anacrolix/go.torrent/util"
-	"bytes"
 	"crypto"
 	_ "crypto/sha1"
 	"encoding/binary"
@@ -141,8 +140,7 @@ func (s *Server) Serve() error {
 		var d Msg
 		err = bencode.Unmarshal(b[:n], &d)
 		if err != nil {
-			// TODO: What are these messages?
-			if !bytes.HasPrefix(b[:], []byte("A\x00")) {
+			if se, ok := err.(*bencode.SyntaxError); !ok || se.Offset != 0 {
 				log.Printf("%s: received bad krpc message: %s: %q", s, err, b[:n])
 			}
 			continue
@@ -284,6 +282,7 @@ func (s *Server) getNode(addr *net.UDPAddr) (n *Node) {
 func (s *Server) writeToNode(b []byte, node *net.UDPAddr) (err error) {
 	n, err := s.Socket.WriteTo(b, node)
 	if err != nil {
+		err = fmt.Errorf("error writing %d bytes to %s: %s", len(b), node, err)
 		return
 	}
 	if n != len(b) {

peer_protocol/protocol.go

@@ -127,18 +127,18 @@ func (d *Decoder) Decode(msg *Message) (err error) {
 	_, err = io.ReadFull(d.R, b)
 	if err == io.EOF {
 		err = io.ErrUnexpectedEOF
-		return
 	}
 	if err != nil {
 		return
 	}
 	r := bytes.NewReader(b)
+	// Check that all of r was utilized.
 	defer func() {
-		written, _ := io.Copy(ioutil.Discard, r)
-		if written != 0 && err == nil {
-			err = fmt.Errorf("short read on message type %d, left %d bytes", msg.Type, written)
-		} else if err == io.EOF {
-			err = io.ErrUnexpectedEOF
+		if err != nil {
+			return
+		}
+		if r.Len() != 0 {
+			err = fmt.Errorf("%d bytes unused in message type %d", r.Len(), msg.Type)
 		}
 	}()
 	msg.Keepalive = false