mailru: fix range requests after june changes on server

backend/mailru/mailru.go

@@ -37,6 +37,7 @@ import (
 	"github.com/rclone/rclone/lib/encoder"
 	"github.com/rclone/rclone/lib/oauthutil"
 	"github.com/rclone/rclone/lib/pacer"
+	"github.com/rclone/rclone/lib/readers"
 	"github.com/rclone/rclone/lib/rest"
 
 	"github.com/pkg/errors"
@@ -2116,7 +2117,18 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (in io.Read
 		return nil, err
 	}
 
-	start, end, partial := getTransferRange(o.size, options...)
+	start, end, partialRequest := getTransferRange(o.size, options...)
+
+	headers := map[string]string{
+		"Accept":       "*/*",
+		"Content-Type": "application/octet-stream",
+	}
+	if partialRequest {
+		rangeStr := fmt.Sprintf("bytes=%d-%d", start, end-1)
+		headers["Range"] = rangeStr
+		// headers["Content-Range"] = rangeStr
+		headers["Accept-Ranges"] = "bytes"
+	}
 
 	// TODO: set custom timeouts
 	opts := rest.Opts{
@@ -2127,10 +2139,7 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (in io.Read
 			"client_id": {api.OAuthClientID},
 			"token":     {token},
 		},
-		ExtraHeaders: map[string]string{
+		ExtraHeaders: headers,
-			"Accept": "*/*",
-			"Range":  fmt.Sprintf("bytes=%d-%d", start, end-1),
-		},
 	}
 
 	var res *http.Response
@@ -2151,18 +2160,36 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (in io.Read
 		return nil, err
 	}
 
-	var hasher gohash.Hash
+	// Server should respond with Status 206 and Content-Range header to a range
-	if !partial {
+	// request. Status 200 (and no Content-Range) means a full-content response.
+	partialResponse := res.StatusCode == 206
+
+	var (
+		hasher     gohash.Hash
+		wrapStream io.ReadCloser
+	)
+	if !partialResponse {
 		// Cannot check hash of partial download
 		hasher = mrhash.New()
 	}
-	wrapStream := &endHandler{
+	wrapStream = &endHandler{
 		ctx:    ctx,
 		stream: res.Body,
 		hasher: hasher,
 		o:      o,
 		server: server,
 	}
+	if partialRequest && !partialResponse {
+		fs.Debugf(o, "Server returned full content instead of range")
+		if start > 0 {
+			// Discard the beginning of the data
+			_, err = io.CopyN(ioutil.Discard, wrapStream, start)
+			if err != nil {
+				return nil, err
+			}
+		}
+		wrapStream = readers.NewLimitedReadCloser(wrapStream, end-start)
+	}
 	return wrapStream, nil
 }