Retain sandbox only if network is not available

It is sufficient to check only if network is available
in store to make the decision of whether to retain the
stale sandbox. If the endpoints are not available then
there is no point in retaining the sandbox anyways. This
fixes some extreme corner cases, where daemon goes down
right in the middle of sandbox cleanup happening.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>

libnetwork/sandbox.go

@@ -177,13 +177,18 @@ func (sb *sandbox) Delete() error {
 			continue
 		}
 
-		if err := ep.Leave(sb); err != nil {
+		// Retain the sanbdox if we can't obtain the network from store.
+		if _, err := c.getNetworkFromStore(ep.getNetwork().ID()); err != nil {
 			retain = true
+			log.Warnf("Failed getting network for ep %s during sandbox %s delete: %v", ep.ID(), sb.ID(), err)
+			continue
+		}
+
+		if err := ep.Leave(sb); err != nil {
 			log.Warnf("Failed detaching sandbox %s from endpoint %s: %v\n", sb.ID(), ep.ID(), err)
 		}
 
 		if err := ep.Delete(); err != nil {
-			retain = true
 			log.Warnf("Failed deleting endpoint %s: %v\n", ep.ID(), err)
 		}
 	}
@@ -455,7 +460,7 @@ func (sb *sandbox) populateNetworkResources(ep *endpoint) error {
 	i := ep.iface
 	ep.Unlock()
 
-	if i.srcName != "" {
+	if i != nil && i.srcName != "" {
 		var ifaceOptions []osl.IfaceOption
 
 		ifaceOptions = append(ifaceOptions, sb.osSbox.InterfaceOptions().Address(i.addr), sb.osSbox.InterfaceOptions().Routes(i.routes))
@@ -951,6 +956,11 @@ func OptionGeneric(generic map[string]interface{}) SandboxOption {
 func (eh epHeap) Len() int { return len(eh) }
 
 func (eh epHeap) Less(i, j int) bool {
+	var (
+		cip, cjp int
+		ok       bool
+	)
+
 	ci, _ := eh[i].getSandbox()
 	cj, _ := eh[j].getSandbox()
 
@@ -965,14 +975,20 @@ func (eh epHeap) Less(i, j int) bool {
 		return true
 	}
 
-	cip, ok := ci.epPriority[eh[i].ID()]
-	if !ok {
-		cip = 0
+	if ci != nil {
+		cip, ok = ci.epPriority[eh[i].ID()]
+		if !ok {
+			cip = 0
+		}
 	}
-	cjp, ok := cj.epPriority[eh[j].ID()]
-	if !ok {
-		cjp = 0
+
+	if cj != nil {
+		cjp, ok = cj.epPriority[eh[j].ID()]
+		if !ok {
+			cjp = 0
+		}
 	}
+
 	if cip == cjp {
 		return eh[i].network.Name() < eh[j].network.Name()
 	}