Remove all instances of named return "err" from Libpod

This was inspired by https://github.com/cri-o/cri-o/pull/3934 and
much of the logic for it is contained there. However, in brief,
a named return called "err" can cause lots of code confusion and
encourages using the wrong err variable in defer statements,
which can make them work incorrectly. Using a separate name which
is not used elsewhere makes it very clear what the defer should
be doing.

As part of this, remove a large number of named returns that were
not used anywhere. Most of them were once needed, but are no
longer necessary after previous refactors (but were accidentally
retained).

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 9 insertions, 9 deletions

diff --git a/libpod/networking_linux.go b/libpod/networking_linux.go
index 7985e17e1..5a8faa7a4 100644
--- a/libpod/networking_linux.go
+++ b/libpod/networking_linux.go
@@ -141,18 +141,18 @@ func (r *Runtime) configureNetNS(ctr *Container, ctrNS ns.NetNS) ([]*cnitypes.Re
 }
 
 // Create and configure a new network namespace for a container
-func (r *Runtime) createNetNS(ctr *Container) (n ns.NetNS, q []*cnitypes.Result, err error) {
+func (r *Runtime) createNetNS(ctr *Container) (n ns.NetNS, q []*cnitypes.Result, retErr error) {
 	ctrNS, err := netns.NewNS()
 	if err != nil {
 		return nil, nil, errors.Wrapf(err, "error creating network namespace for container %s", ctr.ID())
 	}
 	defer func() {
-		if err != nil {
-			if err2 := netns.UnmountNS(ctrNS); err2 != nil {
-				logrus.Errorf("Error unmounting partially created network namespace for container %s: %v", ctr.ID(), err2)
+		if retErr != nil {
+			if err := netns.UnmountNS(ctrNS); err != nil {
+				logrus.Errorf("Error unmounting partially created network namespace for container %s: %v", ctr.ID(), err)
 			}
-			if err2 := ctrNS.Close(); err2 != nil {
-				logrus.Errorf("Error closing partially created network namespace for container %s: %v", ctr.ID(), err2)
+			if err := ctrNS.Close(); err != nil {
+				logrus.Errorf("Error closing partially created network namespace for container %s: %v", ctr.ID(), err)
 			}
 		}
 	}()
@@ -188,7 +188,7 @@ func checkSlirpFlags(path string) (*slirpFeatures, error) {
 }
 
 // Configure the network namespace for a rootless container
-func (r *Runtime) setupRootlessNetNS(ctr *Container) (err error) {
+func (r *Runtime) setupRootlessNetNS(ctr *Container) error {
 	path := r.config.Engine.NetworkCmdPath
 
 	if path == "" {
@@ -342,7 +342,7 @@ func waitForSync(syncR *os.File, cmd *exec.Cmd, logFile io.ReadSeeker, timeout t
 	return nil
 }
 
-func (r *Runtime) setupRootlessPortMapping(ctr *Container, netnsPath string) (err error) {
+func (r *Runtime) setupRootlessPortMapping(ctr *Container, netnsPath string) error {
 	syncR, syncW, err := os.Pipe()
 	if err != nil {
 		return errors.Wrapf(err, "failed to open pipe")
@@ -420,7 +420,7 @@ func (r *Runtime) setupRootlessPortMapping(ctr *Container, netnsPath string) (er
 }
 
 // Configure the network namespace using the container process
-func (r *Runtime) setupNetNS(ctr *Container) (err error) {
+func (r *Runtime) setupNetNS(ctr *Container) error {
 	nsProcess := fmt.Sprintf("/proc/%d/ns/net", ctr.state.PID)
 
 	b := make([]byte, 16)