Fix label allocation for multicast

During BFD scale tests a crash was observed when attempting to
free an MPLS label, It turns out the label for a local interface
was allocated a label in the multicast range.
The root cause - during the allocation of label blocks per
control node the last label in the block wasn't actually
reserved. This label was allocated to locally on the agent for a VMI.
When attempting to free the label the check for the multicast range
suceeds, at this point it attempts to look up the vrf name from the
label data (changes made in bug#1724114), the label data is not set
in this case and causes the crash.

Fix: Correct the label block allocation for multicast to reserve all
labels in the range.

Change-Id: I47feb2a23b721a616b879d5e542fb2f80348d4fa
Closes-Bug: 1798483

src/vnsw/agent/controller/controller_init.cc

@@ -85,7 +85,9 @@ VNController::~VNController() {
 void VNController::FillMcastLabelRange(uint32_t *start_idx,
                                        uint32_t *end_idx,
                                        uint8_t idx) const {
+    // Multicast labels required by both control nodes
     uint32_t max_mc_labels = 2 * (agent_->vrouter_max_vrfs());
+    // Multicast label count per control node
     uint32_t mc_label_count = 0;
     uint32_t vrouter_max_labels = agent_->vrouter_max_labels();
 
@@ -125,9 +127,9 @@ void VNController::SetAgentMcastLabelRange(uint8_t idx) {
     FillMcastLabelRange(&start, &end, idx);
     str << start << "-" << end;
 
-    agent_->mpls_table()->ReserveMulticastLabel(start, end + 1, idx);
+    agent_->mpls_table()->ReserveMulticastLabel(start, end, idx);
     fabric_multicast_label_range_[idx].start = start;
-    fabric_multicast_label_range_[idx].end = (end + 1);
+    fabric_multicast_label_range_[idx].end = end;
     fabric_multicast_label_range_[idx].fabric_multicast_label_range_str =
         str.str();
 }

src/vnsw/agent/oper/mpls.cc

@@ -282,9 +282,12 @@ bool MplsTable::OnChange(DBEntry *entry, const DBRequest *req) {
 }
 
 bool MplsTable::Delete(DBEntry *entry, const DBRequest *req) {
-    MplsLabelData *data = static_cast<MplsLabelData *>(req->data.get());
     MplsLabel *mpls = static_cast<MplsLabel *>(entry);
     if (IsFabricMulticastLabel(mpls->label())) {
+        MplsLabelData *data = static_cast<MplsLabelData *>(req->data.get());
+        // For multicast labels we not expect to be here
+        // via MplsTable::OnZeroRefcount where data is not set.
+        assert(data);
         mpls->fmg_nh_list().erase(data->vrf_name());
         if (mpls->fmg_nh_list().empty() == false) {
             if (mpls->ChangeNH(mpls->fmg_nh_list().begin()->second)) {
@@ -347,15 +350,15 @@ bool MplsTable::IsFabricMulticastLabel(uint32_t label) const {
 void MplsTable::ReserveLabel(uint32_t start, uint32_t end) {
     // We want to allocate labels from an offset
     // Pre-allocate entries
-    for (uint32_t i = start; i < end;  i++) {
+    for (uint32_t i = start; i <= end;  i++) {
         agent()->resource_manager()->ReserveIndex(Resource::MPLS_INDEX, i);
     }
 }
 
 void MplsTable::FreeReserveLabel(uint32_t start, uint32_t end) {
     // We want to allocate labels from an offset
     // Pre-allocate entries
-    for (uint32_t i = start; i < end;  i++) {
+    for (uint32_t i = start; i <= end;  i++) {
         agent()->resource_manager()->ReleaseIndex(Resource::MPLS_INDEX, i);
     }
 }

src/vnsw/agent/oper/operdb_init.cc

@@ -174,7 +174,7 @@ void OperDB::CreateDBTables(DB *db) {
     assert(mpls_table);
     agent_->set_mpls_table(mpls_table);
     mpls_table->set_agent(agent_);
-    mpls_table->ReserveLabel(0, MplsTable::kStartLabel);
+    mpls_table->ReserveLabel(0, MplsTable::kStartLabel - 1);
 
     AclTable *acl_table;
     acl_table = static_cast<AclTable *>(db->CreateTable("db.acl.0"));
@@ -341,7 +341,7 @@ OperDB::~OperDB() {
 }
 
 void OperDB::Shutdown() {
-    agent_->mpls_table()->FreeReserveLabel(0, MplsTable::kStartLabel);
+    agent_->mpls_table()->FreeReserveLabel(0, MplsTable::kStartLabel - 1);
     instance_manager_->Terminate();
     if (nexthop_manager_.get()) {
         nexthop_manager_->Terminate();