send Content-Length and Accept-Ranges headers

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

pkg/rhttp/datatx/utils/download/download.go

@@ -24,6 +24,7 @@ import (
 	"io"
 	"mime/multipart"
 	"net/http"
+	"strconv"
 
 	provider "github.com/cs3org/go-cs3apis/cs3/storage/provider/v1beta1"
 	"github.com/cs3org/reva/pkg/appctx"
@@ -91,67 +92,78 @@ func GetOrHeadFile(w http.ResponseWriter, r *http.Request, fs storage.FS) {
 
 	sendSize := int64(md.Size)
 	var sendContent io.Reader = content
-	var s io.Seeker
-	if len(ranges) > 0 {
-		sublog.Debug().Int64("start", ranges[0].Start).Int64("length", ranges[0].Length).Msg("range request")
-		if s, ok = content.(io.Seeker); !ok {
-			sublog.Error().Int64("start", ranges[0].Start).Int64("length", ranges[0].Length).Msg("ReadCloser is not seekable")
-			w.WriteHeader(http.StatusRequestedRangeNotSatisfiable)
-			return
+	if md.Size >= 0 { // we only need to check the range if we have bytes to transfer
+		var s io.Seeker
+		if s, ok = content.(io.Seeker); ok {
+			// tell clients they can send range requests
+			w.Header().Set("Accept-Ranges", "bytes")
 		}
-		switch {
-		case len(ranges) == 1:
-			// RFC 7233, Section 4.1:
-			// "If a single part is being transferred, the server
-			// generating the 206 response MUST generate a
-			// Content-Range header field, describing what range
-			// of the selected representation is enclosed, and a
-			// payload consisting of the range.
-			// ...
-			// A server MUST NOT generate a multipart response to
-			// a request for a single range, since a client that
-			// does not request multiple parts might not support
-			// multipart responses."
-			ra := ranges[0]
-			if _, err := s.Seek(ra.Start, io.SeekStart); err != nil {
-				sublog.Error().Err(err).Int64("start", ra.Start).Int64("length", ra.Length).Msg("content is not seekable")
+		if len(ranges) > 0 {
+			sublog.Debug().Int64("start", ranges[0].Start).Int64("length", ranges[0].Length).Msg("range request")
+			if s == nil {
+				sublog.Error().Int64("start", ranges[0].Start).Int64("length", ranges[0].Length).Msg("ReadCloser is not seekable")
 				w.WriteHeader(http.StatusRequestedRangeNotSatisfiable)
 				return
 			}
-			sendSize = ra.Length
-			code = http.StatusPartialContent
-			w.Header().Set("Content-Range", ra.ContentRange(int64(md.Size)))
-		case len(ranges) > 1:
-			sendSize = RangesMIMESize(ranges, md.MimeType, int64(md.Size))
-			code = http.StatusPartialContent
-
-			pr, pw := io.Pipe()
-			mw := multipart.NewWriter(pw)
-			w.Header().Set("Content-Type", "multipart/byteranges; boundary="+mw.Boundary())
-			sendContent = pr
-			defer pr.Close() // cause writing goroutine to fail and exit if CopyN doesn't finish.
-			go func() {
-				for _, ra := range ranges {
-					part, err := mw.CreatePart(ra.MimeHeader(md.MimeType, int64(md.Size)))
-					if err != nil {
-						_ = pw.CloseWithError(err) // CloseWithError always returns nil
-						return
-					}
-					if _, err := s.Seek(ra.Start, io.SeekStart); err != nil {
-						_ = pw.CloseWithError(err) // CloseWithError always returns nil
-						return
-					}
-					if _, err := io.CopyN(part, content, ra.Length); err != nil {
-						_ = pw.CloseWithError(err) // CloseWithError always returns nil
-						return
-					}
-				}
-				mw.Close()
-				pw.Close()
-			}()
 
+			switch {
+			case len(ranges) == 1:
+				// RFC 7233, Section 4.1:
+				// "If a single part is being transferred, the server
+				// generating the 206 response MUST generate a
+				// Content-Range header field, describing what range
+				// of the selected representation is enclosed, and a
+				// payload consisting of the range.
+				// ...
+				// A server MUST NOT generate a multipart response to
+				// a request for a single range, since a client that
+				// does not request multiple parts might not support
+				// multipart responses."
+				ra := ranges[0]
+				if _, err := s.Seek(ra.Start, io.SeekStart); err != nil {
+					sublog.Error().Err(err).Int64("start", ra.Start).Int64("length", ra.Length).Msg("content is not seekable")
+					w.WriteHeader(http.StatusRequestedRangeNotSatisfiable)
+					return
+				}
+				sendSize = ra.Length
+				code = http.StatusPartialContent
+				w.Header().Set("Content-Range", ra.ContentRange(int64(md.Size)))
+			case len(ranges) > 1:
+				sendSize = RangesMIMESize(ranges, md.MimeType, int64(md.Size))
+				code = http.StatusPartialContent
+
+				pr, pw := io.Pipe()
+				mw := multipart.NewWriter(pw)
+				w.Header().Set("Content-Type", "multipart/byteranges; boundary="+mw.Boundary())
+				sendContent = pr
+				defer pr.Close() // cause writing goroutine to fail and exit if CopyN doesn't finish.
+				go func() {
+					for _, ra := range ranges {
+						part, err := mw.CreatePart(ra.MimeHeader(md.MimeType, int64(md.Size)))
+						if err != nil {
+							_ = pw.CloseWithError(err) // CloseWithError always returns nil
+							return
+						}
+						if _, err := s.Seek(ra.Start, io.SeekStart); err != nil {
+							_ = pw.CloseWithError(err) // CloseWithError always returns nil
+							return
+						}
+						if _, err := io.CopyN(part, content, ra.Length); err != nil {
+							_ = pw.CloseWithError(err) // CloseWithError always returns nil
+							return
+						}
+					}
+					mw.Close()
+					pw.Close()
+				}()
+			}
 		}
 	}
+
+	if w.Header().Get("Content-Encoding") == "" {
+		w.Header().Set("Content-Length", strconv.FormatInt(sendSize, 10))
+	}
+
 	w.WriteHeader(code)
 
 	if r.Method != "HEAD" {