criu swrk: return child error to caller

In the podman CI we are seeing a weird flake during criu version
detection[1]. The write to the socket just fails with broken pipe.
The logical thing to assume here is that the child exited. However the
current code never reports back the child error from wait. The cleanup
error is now added to the returned error so the caller sees both.

The output is not captured as this causes hangs when the fds are passed
into child processes.

As errors.Join is used from the std lib bump the minimum go version to
1.20.

[1] containers/podman#18856

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

main.go

@@ -61,13 +61,19 @@ func (c *Criu) Prepare() error {
 }
 
 // Cleanup cleans up
-func (c *Criu) Cleanup() {
+func (c *Criu) Cleanup() error {
+	var errs []error
 	if c.swrkCmd != nil {
-		c.swrkSk.Close()
+		if err := c.swrkSk.Close(); err != nil {
+			errs = append(errs, err)
+		}
 		c.swrkSk = nil
-		_ = c.swrkCmd.Wait()
+		if err := c.swrkCmd.Wait(); err != nil {
+			errs = append(errs, fmt.Errorf("criu swrk failed: %w", err))
+		}
 		c.swrkCmd = nil
 	}
+	return errors.Join(errs...)
 }
 
 func (c *Criu) sendAndRecv(reqB []byte) ([]byte, int, error) {
@@ -99,9 +105,7 @@ func (c *Criu) doSwrk(reqType rpc.CriuReqType, opts *rpc.CriuOpts, nfy Notify) e
 	return nil
 }
 
-func (c *Criu) doSwrkWithResp(reqType rpc.CriuReqType, opts *rpc.CriuOpts, nfy Notify, features *rpc.CriuFeatures) (*rpc.CriuResp, error) {
-	var resp *rpc.CriuResp
-
+func (c *Criu) doSwrkWithResp(reqType rpc.CriuReqType, opts *rpc.CriuOpts, nfy Notify, features *rpc.CriuFeatures) (resp *rpc.CriuResp, retErr error) {
 	req := rpc.CriuReq{
 		Type: &reqType,
 		Opts: opts,
@@ -121,7 +125,13 @@ func (c *Criu) doSwrkWithResp(reqType rpc.CriuReqType, opts *rpc.CriuOpts, nfy N
 			return nil, err
 		}
 
-		defer c.Cleanup()
+		defer func() {
+			// append any cleanup errors to the returned error
+			err := c.Cleanup()
+			if err != nil {
+				retErr = errors.Join(retErr, err)
+			}
+		}()
 	}
 
 	for {

phaul/client.go

@@ -1,6 +1,7 @@
 package phaul
 
 import (
+	"errors"
 	"fmt"
 
 	"github.com/checkpoint-restore/go-criu/v7"
@@ -55,7 +56,7 @@ func isLastIter(iter int, stats *stats.DumpStatsEntry, prevStats *stats.DumpStat
 }
 
 // Migrate function
-func (pc *Client) Migrate() error {
+func (pc *Client) Migrate() (retErr error) {
 	criu := criu.MakeCriu()
 	psi := rpc.CriuPageServerInfo{
 		Fd: proto.Int32(int32(pc.cfg.Memfd)),
@@ -72,7 +73,13 @@ func (pc *Client) Migrate() error {
 		return err
 	}
 
-	defer criu.Cleanup()
+	defer func() {
+		// append any cleanup errors to the returned error
+		err := criu.Cleanup()
+		if err != nil {
+			retErr = errors.Join(retErr, err)
+		}
+	}()
 
 	imgs, err := preparePhaulImages(pc.cfg.Wdir)
 	if err != nil {