Do not close processors during save, but instead close during restore.

Before this change, the processors were closed in beforeSave which caused the
packet processing for established connections to stop even in the case of
save/resume. Do not close in beforeSave, instead close these processors in
afterLoad for restore.

PiperOrigin-RevId: 821714849

Author: nybidari

pkg/sentry/kernel/kernel.go

@@ -80,7 +80,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/state"
 	"gvisor.dev/gvisor/pkg/sync"
-	"gvisor.dev/gvisor/pkg/tcpip/stack"
 
 	uspb "gvisor.dev/gvisor/pkg/sentry/unimpl/unimplemented_syscall_go_proto"
 )
@@ -694,9 +693,7 @@ func (k *Kernel) SaveTo(ctx context.Context, stateFile, pagesMetadata io.WriteCl
 	if rootNS := k.rootNetworkNamespace; rootNS != nil && rootNS.Stack() != nil {
 		// Pause the network stack.
 		netstackPauseStart := time.Now()
-		if resume {
-			ctx = context.WithValue(ctx, stack.CtxResumeStack, resume)
-		} else {
+		if !resume {
 			k.rootNetworkNamespace.Stack().SetRemoveNICs()
 		}
 		log.Infof("Pausing root network namespace")

pkg/tcpip/link/fdbased/processors.go

@@ -128,14 +128,9 @@ func (m *processorManager) start() {
 
 // afterLoad is invoked by stateify.
 func (m *processorManager) afterLoad(ctx context.Context) {
-	// Do not start the processors for save/restore. New NICs and
-	// processors will be created during restore.
-	resume := stack.ResumeStackFromContext(ctx)
-	if !resume {
-		return
-	}
-	m.wg.Add(len(m.processors))
-	m.start()
+	// Close all the old/saved processors. There are new NICs and
+	// processors created during restore.
+	m.close()
 }
 
 func (m *processorManager) connectionHash(cid *connectionID) uint32 {
@@ -281,9 +276,3 @@ func (m *processorManager) wakeReady() {
 		m.ready[i] = false
 	}
 }
-
-// beforeSave is invoked by stateify.
-func (m *processorManager) beforeSave() {
-	m.close()
-	m.wg.Wait()
-}

pkg/tcpip/stack/stack.go

@@ -2521,9 +2521,6 @@ type contextID int
 const (
 	// CtxRestoreStack is a Context.Value key for the stack to be used in restore.
 	CtxRestoreStack contextID = iota
-
-	// CtxResumeStack is a Context.Value key for the stack to be used in resume.
-	CtxResumeStack contextID = iota
 )
 
 // RestoreStackFromContext returns the stack to be used during restore.
@@ -2534,16 +2531,6 @@ func RestoreStackFromContext(ctx context.Context) *Stack {
 	return nil
 }
 
-// ResumeStackFromContext returns the stack to be used during restore.
-func ResumeStackFromContext(ctx context.Context) bool {
-	// If we are resuming, the context should have a value set to true. If
-	// restoring it will be false or not exist.
-	if resume := ctx.Value(CtxResumeStack); resume != nil {
-		return resume.(bool)
-	}
-	return false
-}
-
 // SetRemoveNICs sets the removeNICs in stack to true during save/restore.
 func (s *Stack) SetRemoveNICs() {
 	s.mu.Lock()