fix: handle dead VMM and scan all urunc TAP devices during cleanup

Treat ESRCH from killProcess as success since the process is already
gone, allowing network cleanup to proceed instead of failing silently.

Refactored network.Cleanup to scan for all tap.*_urunc interfaces
rather than relying on a hardcoded name. Continue processing remaining
devices on per-device errors and return a joined error at the end.

Fixes #408
Integrates #407

PR: #476
Signed-off-by: goyalpalak18 <goyalpalak1806@gmail.com>
Reviewed-by: Charalampos Mainas <cmainas@nubificus.co.uk>
Approved-by: Charalampos Mainas <cmainas@nubificus.co.uk>

Author: goyalpalak18

.github/linters/urunc-dict.txt

@@ -403,3 +403,4 @@ gocyclo
 gomega
 Logr
 onsi
+ESRCH

pkg/network/network.go

@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"regexp"
 	"strings"
 
 	"github.com/jackpal/gateway"
@@ -262,35 +263,53 @@ func networkSetup(tapName string, ipAddress string, redirectLink netlink.Link, a
 	return newTapDevice, nil
 }
 
-func Cleanup(tapDevice string) error {
+func CleanupAllUruncTaps() error {
 	netlog.Debug("net cleanup called")
-	ifaces, err := net.Interfaces()
-	if err != nil {
-		return err
-	}
-	for _, iface := range ifaces {
-		netlog.Debugf("Discovered device %s", iface.Name)
-	}
-	tapLink, err := netlink.LinkByName(tapDevice)
-	if err != nil {
-		netlog.Errorf("Failed to get link %s by name: %v", tapDevice, err)
-		return nil
-	}
-	err = deleteAllTCFilters(tapLink)
+
+	handle, err := netlink.NewHandle()
 	if err != nil {
-		netlog.Errorf("Failed to delete all TC filters: %v", err)
-		return err
+		return fmt.Errorf("failed to get netlink handle: %w", err)
 	}
-	err = deleteAllQDiscs(tapLink)
+	defer handle.Close()
+
+	links, err := handle.LinkList()
 	if err != nil {
-		netlog.Errorf("Failed to delete all qdiscs: %v", err)
-		return err
+		return fmt.Errorf("failed to list links: %w", err)
 	}
-	err = deleteTapDevice(tapLink)
-	if err != nil {
-		netlog.Errorf("Failed to delete link %s: %v", tapDevice, err)
+
+	var retErr error
+	tapRe := regexp.MustCompile(`^tap_\d+_urunc$`)
+	for _, link := range links {
+		attrs := link.Attrs()
+		if attrs == nil {
+			continue
+		}
+		name := attrs.Name
+		if !tapRe.MatchString(name) {
+			continue
+		}
+
+		netlog.Debugf("cleaning up tap device %s", name)
+		var devErr error
+		if err := deleteAllTCFilters(link); err != nil {
+			netlog.Errorf("failed to delete TC filters for %s: %v", name, err)
+			devErr = errors.Join(devErr, err)
+		}
+		if err := deleteAllQDiscs(link); err != nil {
+			netlog.Errorf("failed to delete qdiscs for %s: %v", name, err)
+			devErr = errors.Join(devErr, err)
+		}
+		if err := deleteTapDevice(link); err != nil {
+			netlog.Errorf("failed to delete tap %s: %v", name, err)
+			devErr = errors.Join(devErr, err)
+		}
+		if devErr == nil {
+			netlog.Debugf("deleted tap device %s", name)
+		}
+		retErr = errors.Join(retErr, devErr)
 	}
-	return nil
+
+	return retErr
 }
 
 func deleteIngressQdisc(link netlink.Link) error {

pkg/unikontainers/hypervisors/utils.go

@@ -71,6 +71,10 @@ func killProcess(pid int) error {
 	const timeout = 2 * time.Second
 	err := syscall.Kill(pid, unix.SIGKILL)
 	if err != nil {
+		if errors.Is(err, syscall.ESRCH) {
+			// Process already dead, nothing to do
+			return nil
+		}
 		return err
 	}
 	deadline := time.Now().Add(timeout)

pkg/unikontainers/unikontainers.go

@@ -585,10 +585,9 @@ func (u *Unikontainer) Kill() error {
 		return err
 	}
 
-	// TODO: tap0_urunc should not be hardcoded
-	err = network.Cleanup("tap0_urunc")
+	err = network.CleanupAllUruncTaps()
 	if err != nil {
-		uniklog.Errorf("failed to delete tap0_urunc: %v", err)
+		uniklog.Errorf("failed to cleanup tap devices: %v", err)
 	}
 
 	return nil