Fix for interface link-state going out-of-sync between agent and host-os

The VifListener module tracks the link-state for a tap interface by
listening to Netlink messages from host-os. When it identifies
transition of link-state, it enqueues RESYNC operation on interface to
re-evaluate the ACTIVE state of interface.

Bug:
There is a corner case where Interface object may not have right state.

1. Tap interface gets created in down state
2. Agent adds interface to oper-db in down state
3. Agent adds the interface-object in notify queue
4. When interface is in notify-queue,
   - VifListener gets notification of link going to UP state
   - VifListener ignore the link transition since it is not notified of
     the interface yet
5. VifListener module gets interface notification

In (5), VifListener should enqueue RESYNC operation on interface. But,
its not doing it currently.

Fix:
- Modify case (5) above to enqueue RESYNC operation on interface
- Modify VifListener to notify all Netlink messages to interface
  independent of whether state is transitioned or not

Change-Id: I4472d9396387d75c53a0c3cd53f30d87de565799
Closes-Bug: #1466935

src/vnsw/agent/vrouter/ksync/linux/vnswif_listener.cc

@@ -297,7 +297,7 @@ VnswInterfaceListenerLinux::HandleNetlinkIntfMsg(struct nlmsghdr *nlh) {
     assert(port_name != NULL);
     LOG(DEBUG, "Handle netlink interface message "
         << NetlinkTypeToString(nlh->nlmsg_type)
-        << " for interface " << port_name);
+        << " for interface " << port_name << " flags " << ifi->ifi_flags);
 
     Event::Type type;
     if (nlh->nlmsg_type == RTM_DELLINK) {

src/vnsw/agent/vrouter/ksync/vnswif_listener_base.cc

@@ -191,26 +191,20 @@ void VnswInterfaceListenerBase::SetSeen(const std::string &name, bool oper) {
         host_interface_table_.insert(make_pair(name, entry));
     }
 
-    bool old_active = IsInterfaceActive(entry);
     if (oper) {
         entry->oper_seen_ = true;
     } else {
         entry->host_seen_ = true;
     }
 
-    if (old_active == IsInterfaceActive(entry))
-        return;
-
-    if (old_active == false)
-        Activate(name, entry->oper_id_);
+    Activate(name, entry->oper_id_);
 }
 
 void VnswInterfaceListenerBase::ResetSeen(const std::string &name, bool oper) {
     HostInterfaceEntry *entry = GetHostInterfaceEntry(name);
     if (entry == NULL)
         return;
 
-    bool old_active = IsInterfaceActive(entry);
     if (oper) {
         entry->oper_seen_ = false;
     } else {
@@ -224,11 +218,7 @@ void VnswInterfaceListenerBase::ResetSeen(const std::string &name, bool oper) {
         return;
     }
 
-    if (old_active == IsInterfaceActive(entry))
-        return;
-
-    if (old_active)
-        DeActivate(name, entry->oper_id_);
+    DeActivate(name, entry->oper_id_);
 }
 
 void VnswInterfaceListenerBase::SetLinkState(const std::string &name, bool link_up){
@@ -239,9 +229,6 @@ void VnswInterfaceListenerBase::SetLinkState(const std::string &name, bool link_
     bool old_active = IsInterfaceActive(entry);
     entry->link_up_ = link_up;
 
-    if (old_active == IsInterfaceActive(entry))
-        return;
-
     if (old_active)
         DeActivate(name, entry->oper_id_);
     else