syncpipe: read from parent before reporting error

Docker-DCO-1.1-Signed-off-by: Bernerd Schaefer <bj.schaefer@gmail.com> (github: bernerdschaefer)

syncpipe/sync_pipe.go

@@ -77,6 +77,10 @@ func (s *SyncPipe) ReadFromParent(v interface{}) error {
 }
 
 func (s *SyncPipe) ReportChildError(err error) {
+	// ensure that any data sent from the parent is consumed so it doesn't
+	// receive ECONNRESET when the child writes to the pipe.
+	ioutil.ReadAll(s.child)
+
 	s.child.Write([]byte(err.Error()))
 	s.CloseChild()
 }

syncpipe/sync_pipe_test.go

@@ -2,6 +2,7 @@ package syncpipe
 
 import (
 	"fmt"
+	"syscall"
 	"testing"
 )
 
@@ -20,9 +21,17 @@ func TestSendErrorFromChild(t *testing.T) {
 		}
 	}()
 
-	expected := "something bad happened"
+	childfd, err := syscall.Dup(int(pipe.Child().Fd()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	childPipe, _ := NewSyncPipeFromFd(0, uintptr(childfd))
 
-	pipe.ReportChildError(fmt.Errorf(expected))
+	pipe.CloseChild()
+	pipe.SendToChild(nil)
+
+	expected := "something bad happened"
+	childPipe.ReportChildError(fmt.Errorf(expected))
 
 	childError := pipe.ReadFromChild()
 	if childError == nil {