remote exec: write conmon error on hijacked connection

Make sure to write error from conmon on the hijacked http connection.
This fixes issues where errors were not reported on the client side,
for instance, when specified command was not found on the container.

To future generations: I am sorry.  The code is complex, and there are
many interdependencies among the concurrent goroutines.  I added more
complexity on top but I don't have a good idea of how to reduce
complexity in the available time.

Fixes: #8281
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

1 files changed, 10 insertions, 7 deletions

diff --git a/libpod/util.go b/libpod/util.go
index bf9bf2542..391208fb9 100644
--- a/libpod/util.go
+++ b/libpod/util.go
@@ -235,20 +235,16 @@ func checkDependencyContainer(depCtr, ctr *Container) error {
 	return nil
 }
 
-// hijackWriteErrorAndClose writes an error to a hijacked HTTP session and
-// closes it. Intended to HTTPAttach function.
-// If error is nil, it will not be written; we'll only close the connection.
-func hijackWriteErrorAndClose(toWrite error, cid string, terminal bool, httpCon io.Closer, httpBuf *bufio.ReadWriter) {
+// hijackWriteError writes an error to a hijacked HTTP session.
+func hijackWriteError(toWrite error, cid string, terminal bool, httpBuf *bufio.ReadWriter) {
 	if toWrite != nil {
-		errString := []byte(fmt.Sprintf("%v\n", toWrite))
+		errString := []byte(fmt.Sprintf("Error: %v\n", toWrite))
 		if !terminal {
 			// We need a header.
 			header := makeHTTPAttachHeader(2, uint32(len(errString)))
 			if _, err := httpBuf.Write(header); err != nil {
 				logrus.Errorf("Error writing header for container %s attach connection error: %v", cid, err)
 			}
-			// TODO: May want to return immediately here to avoid
-			// writing garbage to the socket?
 		}
 		if _, err := httpBuf.Write(errString); err != nil {
 			logrus.Errorf("Error writing error to container %s HTTP attach connection: %v", cid, err)
@@ -257,6 +253,13 @@ func hijackWriteErrorAndClose(toWrite error, cid string, terminal bool, httpCon
 			logrus.Errorf("Error flushing HTTP buffer for container %s HTTP attach connection: %v", cid, err)
 		}
 	}
+}
+
+// hijackWriteErrorAndClose writes an error to a hijacked HTTP session and
+// closes it. Intended to HTTPAttach function.
+// If error is nil, it will not be written; we'll only close the connection.
+func hijackWriteErrorAndClose(toWrite error, cid string, terminal bool, httpCon io.Closer, httpBuf *bufio.ReadWriter) {
+	hijackWriteError(toWrite, cid, terminal, httpBuf)
 
 	if err := httpCon.Close(); err != nil {
 		logrus.Errorf("Error closing container %s HTTP attach connection: %v", cid, err)