tracker: Allow resolving announce URL host in advance, and passing the desired Host field for HTTP requests

Also did some clean-up of the announce code, the concept of a client is going away.

tracker/http.go

@@ -10,26 +10,12 @@ import (
 	"net/url"
 	"strconv"
 
+	"github.com/anacrolix/missinggo/httptoo"
+
 	"github.com/anacrolix/torrent/bencode"
 	"github.com/anacrolix/torrent/util"
 )
 
-func init() {
-	registerClientScheme("http", newHTTPClient)
-}
-
-type httpClient struct {
-	url url.URL
-}
-
-func (httpClient) Close() error { return nil }
-
-func newHTTPClient(url *url.URL) client {
-	return &httpClient{
-		url: *url,
-	}
-}
-
 type httpResponse struct {
 	FailureReason string      `bencode:"failure reason"`
 	Interval      int32       `bencode:"interval"`
@@ -56,9 +42,8 @@ func (r *httpResponse) UnmarshalPeers() (ret []Peer, err error) {
 	return
 }
 
-func (c *httpClient) Announce(ar *AnnounceRequest) (ret AnnounceResponse, err error) {
-	// retain query parameters from announce URL
-	q := c.url.Query()
+func setAnnounceParams(_url *url.URL, ar *AnnounceRequest) {
+	q := _url.Query()
 
 	q.Set("info_hash", string(ar.InfoHash[:]))
 	q.Set("peer_id", string(ar.PeerId[:]))
@@ -73,14 +58,21 @@ func (c *httpClient) Announce(ar *AnnounceRequest) (ret AnnounceResponse, err er
 	q.Set("compact", "1")
 	// According to https://wiki.vuze.com/w/Message_Stream_Encryption.
 	q.Set("supportcrypto", "1")
-	var reqURL url.URL = c.url
-	reqURL.RawQuery = q.Encode()
-	resp, err := http.Get(reqURL.String())
+
+	_url.RawQuery = q.Encode()
+}
+
+func announceHTTP(ar *AnnounceRequest, _url *url.URL, host string) (ret AnnounceResponse, err error) {
+	_url = httptoo.CopyURL(_url)
+	setAnnounceParams(_url, ar)
+	req, err := http.NewRequest("GET", _url.String(), nil)
+	req.Host = host
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return
 	}
 	defer resp.Body.Close()
-	buf := bytes.Buffer{}
+	var buf bytes.Buffer
 	io.Copy(&buf, resp.Body)
 	if resp.StatusCode != 200 {
 		err = fmt.Errorf("response from tracker: %s: %s", resp.Status, buf.String())

tracker/tracker.go

@@ -46,42 +46,26 @@ const (
 	Stopped                 // The local peer is leaving the swarm.
 )
 
-type client interface {
-	Announce(*AnnounceRequest) (AnnounceResponse, error)
-	Close() error
-}
-
 var (
 	ErrBadScheme = errors.New("unknown scheme")
-
-	schemes = make(map[string]func(*url.URL) client)
 )
 
-func registerClientScheme(scheme string, newFunc func(*url.URL) client) {
-	schemes[scheme] = newFunc
+func Announce(urlStr string, req *AnnounceRequest) (res AnnounceResponse, err error) {
+	return AnnounceHost(urlStr, req, "")
 }
 
-// Returns ErrBadScheme if the tracker scheme isn't recognised.
-func newClient(rawurl string) (cl client, err error) {
-	url_s, err := url.Parse(rawurl)
+func AnnounceHost(urlStr string, req *AnnounceRequest, host string) (res AnnounceResponse, err error) {
+	_url, err := url.Parse(urlStr)
 	if err != nil {
 		return
 	}
-	newFunc, ok := schemes[url_s.Scheme]
-	if !ok {
+	switch _url.Scheme {
+	case "http", "https":
+		return announceHTTP(req, _url, host)
+	case "udp":
+		return announceUDP(req, _url)
+	default:
 		err = ErrBadScheme
 		return
 	}
-	cl = newFunc(url_s)
-	return
-}
-
-func Announce(urlStr string, req *AnnounceRequest) (res AnnounceResponse, err error) {
-	cl, err := newClient(urlStr)
-	if err != nil {
-		return
-	}
-	defer cl.Close()
-	return cl.Announce(req)
-
 }

tracker/udp.go

@@ -60,16 +60,6 @@ type AnnounceResponseHeader struct {
 	Seeders  int32
 }
 
-func init() {
-	registerClientScheme("udp", newUDPClient)
-}
-
-func newUDPClient(url *url.URL) client {
-	return &udpClient{
-		url: *url,
-	}
-}
-
 func newTransactionId() int32 {
 	return int32(rand.Uint32())
 }
@@ -85,7 +75,7 @@ func timeout(contiguousTimeouts int) (d time.Duration) {
 	return
 }
 
-type udpClient struct {
+type udpAnnounce struct {
 	contiguousTimeouts   int
 	connectionIdReceived time.Time
 	connectionId         int64
@@ -93,14 +83,14 @@ type udpClient struct {
 	url                  url.URL
 }
 
-func (c *udpClient) Close() error {
+func (c *udpAnnounce) Close() error {
 	if c.socket != nil {
 		return c.socket.Close()
 	}
 	return nil
 }
 
-func (c *udpClient) Announce(req *AnnounceRequest) (res AnnounceResponse, err error) {
+func (c *udpAnnounce) Do(req *AnnounceRequest) (res AnnounceResponse, err error) {
 	err = c.connect()
 	if err != nil {
 		return
@@ -140,7 +130,7 @@ func (c *udpClient) Announce(req *AnnounceRequest) (res AnnounceResponse, err er
 
 // body is the binary serializable request body. trailer is optional data
 // following it, such as for BEP 41.
-func (c *udpClient) write(h *RequestHeader, body interface{}, trailer []byte) (err error) {
+func (c *udpAnnounce) write(h *RequestHeader, body interface{}, trailer []byte) (err error) {
 	var buf bytes.Buffer
 	err = binary.Write(&buf, binary.BigEndian, h)
 	if err != nil {
@@ -176,7 +166,7 @@ func write(w io.Writer, data interface{}) error {
 
 // args is the binary serializable request body. trailer is optional data
 // following it, such as for BEP 41.
-func (c *udpClient) request(action Action, args interface{}, options []byte) (responseBody *bytes.Buffer, err error) {
+func (c *udpAnnounce) request(action Action, args interface{}, options []byte) (responseBody *bytes.Buffer, err error) {
 	tid := newTransactionId()
 	err = c.write(&RequestHeader{
 		ConnectionId:  c.connectionId,
@@ -232,11 +222,11 @@ func readBody(r io.Reader, data ...interface{}) (err error) {
 	return
 }
 
-func (c *udpClient) connected() bool {
+func (c *udpAnnounce) connected() bool {
 	return !c.connectionIdReceived.IsZero() && time.Now().Before(c.connectionIdReceived.Add(time.Minute))
 }
 
-func (c *udpClient) connect() (err error) {
+func (c *udpAnnounce) connect() (err error) {
 	if c.connected() {
 		return nil
 	}
@@ -266,3 +256,11 @@ func (c *udpClient) connect() (err error) {
 	c.connectionIdReceived = time.Now()
 	return
 }
+
+func announceUDP(ar *AnnounceRequest, _url *url.URL) (AnnounceResponse, error) {
+	ua := udpAnnounce{
+		url: *_url,
+	}
+	defer ua.Close()
+	return ua.Do(ar)
+}