New scheme of programming reachability group

Summary:
As discussed with Brcm:

	For reachability groups with parallel links, use index 1-128.
 Else use index for single link groups in range 129-256

Reviewed By: jasmeetbagga

Differential Revision:
D65923986

Privacy Context Container: L1125642

fbshipit-source-id: a4dc4429aaa329ae6538a85213a6f9b56fb012f6

fboss/agent/ApplyThriftConfig.cpp

@@ -1271,6 +1271,12 @@ void ThriftConfigApplier::processReachabilityGroup(
     auto newPortMap = new_->getPorts()->modify(&new_);
     for (const auto& fabricSwitchId : localFabricSwitchIds) {
       std::unordered_map<int, int> destinationId2ReachabilityGroup;
+
+      // For reachability groups with parallel links, use index 1-128.
+      // Else use index for single link groups in range 129-256
+      int nextParallelLinkGroup = 1;
+      int nextSingleLinkGroup = 129;
+
       for (const auto& portCfg : *cfg_->ports()) {
         if (scopeResolver_.scope(portCfg).has(SwitchID(fabricSwitchId)) &&
             portCfg.expectedNeighborReachability()->size() > 0) {
@@ -1280,26 +1286,24 @@ void ThriftConfigApplier::processReachabilityGroup(
               new_->getDsfNodes()->getNode(neighborRemoteSwitchId);
 
           int destinationId;
-          // For parallel VOQ links, assign links reaching the same VOQ
-          // switch.
-          if (parallelVoqLinks &&
-              neighborDsfNode->getType() == cfg::DsfNodeType::INTERFACE_NODE) {
+          if (neighborDsfNode->getType() == cfg::DsfNodeType::INTERFACE_NODE) {
             destinationId = neighborRemoteSwitchId;
-          } else if (neighborDsfNode->getClusterId() == std::nullopt) {
-            // Assign links based on cluster ID. Note that in dual stage,
-            // FE2 has no cluster ID: use -1 for grouping purpose.
-            CHECK_EQ(
-                static_cast<int>(cfg::DsfNodeType::FABRIC_NODE),
-                static_cast<int>(neighborDsfNode->getType()));
-            destinationId = -1;
           } else {
-            destinationId = neighborDsfNode->getClusterId().value();
+            // Fabric node links: assign links based on cluster ID. Note that in
+            // dual stage, FE2 has no cluster ID: use -1 for grouping purpose.
+            destinationId = neighborDsfNode->getClusterId().value_or(-1);
           }
+          bool singleLinkGroup =
+              neighborDsfNode->getType() == cfg::DsfNodeType::INTERFACE_NODE &&
+              !parallelVoqLinks;
+          int& nextGroupId =
+              singleLinkGroup ? nextSingleLinkGroup : nextParallelLinkGroup;
 
           auto [it, inserted] = destinationId2ReachabilityGroup.insert(
-              {destinationId, destinationId2ReachabilityGroup.size() + 1});
+              {destinationId, nextGroupId});
           auto reachabilityGroupId = it->second;
           if (inserted) {
+            nextGroupId++;
             XLOG(DBG2) << "Create new reachability group "
                        << reachabilityGroupId << " towards node "
                        << neighborDsfNode->getName() << " with switchId "

fboss/agent/test/ReachabilityGroupTests.cpp

@@ -161,8 +161,11 @@ TEST_F(ReachabilityGroupSingleStageFdswNoParallelIntfLinkTest, test) {
 TEST_F(ReachabilityGroupDualStageFdswNoParallelIntfLinkTest, test) {
   // Dual stage FDSW with no parallel links to interface node.
   // One group for uplinks to SDSW (1) and one group for downlink to RDSW (2).
-  verifyReachabilityGroupListSize(2);
+  // However, SDK requires one group per RDSW downlink, hence we have 1 group
+  // for uplinks to SDSW and 18 groups to RDSW.
+  verifyReachabilityGroupListSize(19);
 
+  int expectedInterfaceNodeReachabilityGroup = 129;
   for (const auto& [_, portMap] : std::as_const(*sw_->getState()->getPorts())) {
     for (const auto& [_, port] : std::as_const(*portMap)) {
       auto neighborDsfNodeType =
@@ -171,7 +174,9 @@ TEST_F(ReachabilityGroupDualStageFdswNoParallelIntfLinkTest, test) {
       EXPECT_TRUE(port->getReachabilityGroupId().has_value());
       EXPECT_EQ(
           port->getReachabilityGroupId().value(),
-          neighborDsfNodeType == cfg::DsfNodeType::FABRIC_NODE ? 1 : 2);
+          neighborDsfNodeType == cfg::DsfNodeType::FABRIC_NODE
+              ? 1
+              : expectedInterfaceNodeReachabilityGroup++);
     }
   }
 }
@@ -229,7 +234,9 @@ TEST_F(
     configUpdateToParallelIntfLinks) {
   // Dual stage FDSW with no parallel links to interface node.
   // One group for uplinks to SDSW (1) and one group for downlink to RDSW (2).
-  verifyReachabilityGroupListSize(2);
+  // However, SDK requires one group per RDSW downlink, hence we have 1 group
+  // for uplinks to SDSW and 18 groups to RDSW.
+  verifyReachabilityGroupListSize(19);
 
   const auto newConfig = testConfigFabricSwitch(
       true /* dualStage*/,