Parse the body of (docker load) response to correctly handle errors

Signed-off-by: Miloslav Trmač <[email protected]>

docker/daemon/daemon_dest.go

@@ -2,6 +2,7 @@ package daemon
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -85,12 +86,40 @@ func imageLoadGoroutine(ctx context.Context, c *client.Client, reader *io.PipeRe
 		}
 	}()
 
+	err = imageLoad(ctx, c, reader)
+}
+
+// imageLoad accepts tar stream on reader and sends it to c
+func imageLoad(ctx context.Context, c *client.Client, reader *io.PipeReader) error {
 	resp, err := c.ImageLoad(ctx, reader, true)
 	if err != nil {
-		err = fmt.Errorf("saving image to docker engine: %w", err)
-		return
+		return fmt.Errorf("starting a load operation in docker engine: %w", err)
 	}
 	defer resp.Body.Close()
+
+	// jsonError and jsonMessage are small subsets of docker/docker/pkg/jsonmessage.JSONError and JSONMessage,
+	// copied here to minimize dependencies.
+	type jsonError struct {
+		Message string `json:"message,omitempty"`
+	}
+	type jsonMessage struct {
+		Error *jsonError `json:"errorDetail,omitempty"`
+	}
+
+	dec := json.NewDecoder(resp.Body)
+	for {
+		var msg jsonMessage
+		if err := dec.Decode(&msg); err != nil {
+			if err == io.EOF {
+				break
+			}
+			return fmt.Errorf("parsing docker load progress: %w", err)
+		}
+		if msg.Error != nil {
+			return fmt.Errorf("docker engine reported: %s", msg.Error.Message)
+		}
+	}
+	return nil // No error reported = success
 }
 
 // DesiredLayerCompression indicates if layers must be compressed, decompressed or preserved