Send Partscount only when partnumber is specified (#9793)

Fixes #9789

cmd/api-headers.go

@@ -68,6 +68,13 @@ func encodeResponseJSON(response interface{}) []byte {
 	return bytesBuffer.Bytes()
 }
 
+// Write parts count
+func setPartsCountHeaders(w http.ResponseWriter, objInfo ObjectInfo) {
+	if strings.Contains(objInfo.ETag, "-") && len(objInfo.Parts) > 0 {
+		w.Header()[xhttp.AmzMpPartsCount] = []string{strconv.Itoa(len(objInfo.Parts))}
+	}
+}
+
 // Write object header
 func setObjectHeaders(w http.ResponseWriter, objInfo ObjectInfo, rs *HTTPRangeSpec) (err error) {
 	// set common headers
@@ -82,10 +89,6 @@ func setObjectHeaders(w http.ResponseWriter, objInfo ObjectInfo, rs *HTTPRangeSp
 		w.Header()[xhttp.ETag] = []string{"\"" + objInfo.ETag + "\""}
 	}
 
-	if strings.Contains(objInfo.ETag, "-") && len(objInfo.Parts) > 0 {
-		w.Header()[xhttp.AmzMpPartsCount] = []string{strconv.Itoa(len(objInfo.Parts))}
-	}
-
 	if objInfo.ContentType != "" {
 		w.Header().Set(xhttp.ContentType, objInfo.ContentType)
 	}

cmd/encryption-v1.go

@@ -903,7 +903,7 @@ func getOpts(ctx context.Context, r *http.Request, bucket, object string) (Objec
 		if err != nil {
 			return opts, err
 		}
-		if partNumber < 0 {
+		if partNumber <= 0 {
 			return opts, errInvalidArgument
 		}
 	}

cmd/object-handlers-common.go

@@ -173,9 +173,9 @@ func checkPreconditions(ctx context.Context, w http.ResponseWriter, r *http.Requ
 	}
 
 	// Check if the part number is correct.
-	if opts.PartNumber > 0 && len(objInfo.Parts) > 0 && opts.PartNumber != len(objInfo.Parts) {
+	if opts.PartNumber > 1 && opts.PartNumber > len(objInfo.Parts) {
 		writeHeaders()
-		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrPreconditionFailed), r.URL, guessIsBrowserReq(r))
+		w.WriteHeader(http.StatusRequestedRangeNotSatisfiable)
 		return true
 	}
 

cmd/object-handlers.go

@@ -426,6 +426,11 @@ func (api objectAPIHandlers) GetObjectHandler(w http.ResponseWriter, r *http.Req
 		return
 	}
 
+	// Set Parts Count Header
+	if opts.PartNumber > 0 && len(objInfo.Parts) > 0 {
+		setPartsCountHeaders(w, objInfo)
+	}
+
 	setHeadGetRespHeaders(w, r.URL.Query())
 	setAmzExpirationHeader(w, bucket, objInfo)
 
@@ -604,6 +609,11 @@ func (api objectAPIHandlers) HeadObjectHandler(w http.ResponseWriter, r *http.Re
 		return
 	}
 
+	// Set Parts Count Header
+	if opts.PartNumber > 0 && len(objInfo.Parts) > 0 {
+		setPartsCountHeaders(w, objInfo)
+	}
+
 	// Set any additional requested response headers.
 	setHeadGetRespHeaders(w, r.URL.Query())
 

cmd/web-handlers.go

@@ -1310,6 +1310,11 @@ func (web *webAPIHandlers) Download(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	// Set Parts Count Header
+	if opts.PartNumber > 0 && len(objInfo.Parts) > 0 {
+		setPartsCountHeaders(w, objInfo)
+	}
+
 	if err = setObjectHeaders(w, objInfo, nil); err != nil {
 		writeWebErrorResponse(w, err)
 		return