add pre-conditions support for PUT calls during replication (#15674)

PUT shall only proceed if pre-conditions are met, the new
code uses

- x-minio-source-mtime
- x-minio-source-etag

to verify if the object indeed needs to be replicated
or not, allowing us to avoid StatObject() call.

cmd/object-handlers-common.go

@@ -130,6 +130,54 @@ func checkCopyObjectPreconditions(ctx context.Context, w http.ResponseWriter, r
 	return false
 }
 
+// Validates the preconditions. Returns true if PUT operation should not proceed.
+// Preconditions supported are:
+//
+//	x-minio-source-mtime
+//	x-minio-source-etag
+func checkPreconditionsPUT(ctx context.Context, w http.ResponseWriter, r *http.Request, objInfo ObjectInfo, opts ObjectOptions) bool {
+	// Return false for methods other than PUT.
+	if r.Method != http.MethodPut {
+		return false
+	}
+	// If the object doesn't have a modtime (IsZero), or the modtime
+	// is obviously garbage (Unix time == 0), then ignore modtimes
+	// and don't process the If-Modified-Since header.
+	if objInfo.ModTime.IsZero() || objInfo.ModTime.Equal(time.Unix(0, 0)) {
+		return false
+	}
+
+	// If top level is a delete marker proceed to upload.
+	if objInfo.DeleteMarker {
+		return false
+	}
+
+	// Headers to be set of object content is not going to be written to the client.
+	writeHeaders := func() {
+		// set common headers
+		setCommonHeaders(w)
+
+		// set object-related metadata headers
+		w.Header().Set(xhttp.LastModified, objInfo.ModTime.UTC().Format(http.TimeFormat))
+
+		if objInfo.ETag != "" {
+			w.Header()[xhttp.ETag] = []string{"\"" + objInfo.ETag + "\""}
+		}
+	}
+
+	etagMatch := opts.PreserveETag != "" && isETagEqual(objInfo.ETag, opts.PreserveETag)
+	vidMatch := opts.VersionID != "" && opts.VersionID == objInfo.VersionID
+	mtimeMatch := !opts.MTime.IsZero() && objInfo.ModTime.Unix() >= opts.MTime.Unix()
+	if etagMatch && vidMatch && mtimeMatch {
+		writeHeaders()
+		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrPreconditionFailed), r.URL)
+		return true
+	}
+
+	// Object content should be persisted.
+	return false
+}
+
 // Validates the preconditions. Returns true if GET/HEAD operation should not proceed.
 // Preconditions supported are:
 //