Add 'config vlan <id> name <value>' CLI command

Adds a new `config vlan <id> name <value>` command to configure
the name attribute of a VLAN. The implementation follows the
`CmdConfigInterface` pattern: a single handler (`CmdConfigVlanConfig`)
dispatches on attribute name, so adding future attributes (e.g.
`routable`) requires only a new subcommand entry in `CmdListConfig.cpp`
and a new `else if` branch in `queryClient` — no new handler class.

If the specified VLAN does not already exist, the command auto-creates
it (via `VlanManager::getOrCreateVlan`) and prints "Created VLAN <id>"
before configuring the attribute — consistent with all other
`config vlan` subcommands.

The auto-create test uses VLAN 3100 (not 3998/3999) because
`getTableIdForNpu` maps IDs in [3000, 3152] to Linux routing table IDs
in [101, 253]. Values above 3152 overflow the 253-table limit and crash
`TunManager` with `Check failed: tableId <= 253`.

```
Note: Google Test filter = *VlanConfig*
[==========] Running 9 tests from 1 test suite.
[----------] 9 tests from CmdConfigVlanConfigTestFixture
[ RUN      ] CmdConfigVlanConfigTestFixture.setNameOnExistingVlan
[       OK ] CmdConfigVlanConfigTestFixture.setNameOnExistingVlan (171 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.setNameUpdatesSwConfig
[       OK ] CmdConfigVlanConfigTestFixture.setNameUpdatesSwConfig (308 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.setNameOnSecondVlan
[       OK ] CmdConfigVlanConfigTestFixture.setNameOnSecondVlan (195 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.setNameOnNonExistentVlanAutoCreates
[       OK ] CmdConfigVlanConfigTestFixture.setNameOnNonExistentVlanAutoCreates (105 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.setNameDoesNotAffectOtherVlans
[       OK ] CmdConfigVlanConfigTestFixture.setNameDoesNotAffectOtherVlans (99 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.vlanNameArgGetAttrName
[       OK ] CmdConfigVlanConfigTestFixture.vlanNameArgGetAttrName (29 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.vlanNameArgGetValue
[       OK ] CmdConfigVlanConfigTestFixture.vlanNameArgGetValue (39 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.vlanNameArgRejectsMissingValue
[       OK ] CmdConfigVlanConfigTestFixture.vlanNameArgRejectsMissingValue (33 ms)
[ RUN      ] CmdConfigVlanConfigTestFixture.vlanNameArgRejectsTooManyArgs
[       OK ] CmdConfigVlanConfigTestFixture.vlanNameArgRejectsTooManyArgs (36 ms)
[----------] 9 tests from CmdConfigVlanConfigTestFixture (1020 ms total)
[==========] 9 tests from 1 test suite ran. (1020 ms total)
[  PASSED  ] 9 tests.
```

```
Note: Google Test filter = ConfigVlanName*
[==========] Running 2 tests from 1 test suite.
[----------] 2 tests from ConfigVlanNameTest
[ RUN      ] ConfigVlanNameTest.SetNameOnExistingVlan
I0325 14:00:25 [Step 1] Finding an eth interface...
I0325 14:00:25   Using interface eth1/1/1 (VLAN 2122)
I0325 14:00:25 [Step 2] Reading current VLAN 2122 name...
I0325 14:00:25   Current name: vlan2122
I0325 14:00:25 [Step 3] Setting VLAN 2122 name to "TestVlanName"...
I0325 14:00:25   Output: {"localhost":"Successfully configured VLAN 2122: name=\"TestVlanName\""}
I0325 14:00:25 [Step 4] Committing...
I0325 14:00:25   Committed.
I0325 14:00:25 [Step 5] Restoring original name "vlan2122"...
I0325 14:00:25   Restored. TEST PASSED
[       OK ] ConfigVlanNameTest.SetNameOnExistingVlan (375 ms)
[ RUN      ] ConfigVlanNameTest.AutoCreateVlanAndSetName
I0325 14:00:25 [Step 0] Ensuring VLAN 3100 is absent from running config...
I0325 14:00:25 [Cleanup]   VLAN 3100 not present — no cleanup needed.
I0325 14:00:25 [Step 1] Setting name on non-existent VLAN 3100...
I0325 14:00:25   Output: Created VLAN 3100
I0325 14:00:25           {"localhost":"Successfully configured VLAN 3100: name=\"TestAutoCreateVlan\""}
I0325 14:00:25 [Step 2] Committing session...
I0325 14:00:25   Config committed.
I0325 14:00:25 [Step 3] Cleaning up VLAN 3100...
I0325 14:00:25   Cleanup complete. TEST PASSED
[       OK ] ConfigVlanNameTest.AutoCreateVlanAndSetName (262 ms)
[----------] 2 tests from ConfigVlanNameTest (637 ms total)
[==========] 2 tests from 1 test suite ran. (638 ms total)
[  PASSED  ] 2 tests.
```

```
fboss2-dev config vlan 2122 name myvlan
fboss2-dev config session commit

fboss2-dev config vlan 3100 name newvlan
fboss2-dev config session commit
```

Author: benoit-nexthop

cmake/CliFboss2.cmake

@@ -977,6 +977,8 @@ add_library(fboss2_config_lib
   fboss/cli/fboss2/commands/config/session/CmdConfigSessionRebase.cpp
   fboss/cli/fboss2/commands/config/vlan/CmdConfigVlan.cpp
   fboss/cli/fboss2/commands/config/vlan/CmdConfigVlan.h
+  fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanConfig.cpp
+  fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanConfig.h
   fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanDefault.cpp
   fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanDefault.h
   fboss/cli/fboss2/commands/config/vlan/VlanManager.cpp

cmake/CliFboss2TestConfig.cmake

@@ -21,6 +21,7 @@ add_executable(fboss2_cmd_config_test
   fboss/cli/fboss2/test/config/CmdConfigSessionDiffTest.cpp
   fboss/cli/fboss2/test/config/CmdConfigSessionTest.cpp
   fboss/cli/fboss2/test/config/CmdConfigTestBase.cpp
+  fboss/cli/fboss2/test/config/CmdConfigVlanConfigTest.cpp
   fboss/cli/fboss2/test/config/CmdConfigVlanDefaultTest.cpp
   fboss/cli/fboss2/test/config/CmdConfigVlanManagerTest.cpp
   fboss/cli/fboss2/test/config/CmdConfigVlanPortTaggingModeTest.cpp

cmake/CliFboss2TestIntegrationTest.cmake

@@ -30,6 +30,7 @@ add_executable(fboss2_integration_test
   fboss/cli/fboss2/test/integration_test/ConfigSessionClearTest.cpp
   fboss/cli/fboss2/test/integration_test/ConfigVlanCreateTest.cpp
   fboss/cli/fboss2/test/integration_test/ConfigVlanDefaultTest.cpp
+  fboss/cli/fboss2/test/integration_test/ConfigVlanNameTest.cpp
   fboss/cli/fboss2/test/integration_test/ConfigVlanPortTaggingModeTest.cpp
   fboss/cli/fboss2/test/integration_test/ConfigVlanStaticMacTest.cpp
   fboss/cli/fboss2/test/integration_test/ConfigVlanSwitchportAccessTest.cpp

fboss/cli/fboss2/BUCK

@@ -1127,6 +1127,7 @@ cpp_library(
         "commands/config/session/CmdConfigSessionDiff.cpp",
         "commands/config/session/CmdConfigSessionRebase.cpp",
         "commands/config/vlan/CmdConfigVlan.cpp",
+        "commands/config/vlan/CmdConfigVlanConfig.cpp",
         "commands/config/vlan/CmdConfigVlanDefault.cpp",
         "commands/config/vlan/VlanManager.cpp",
         "commands/config/vlan/port/CmdConfigVlanPort.cpp",
@@ -1223,6 +1224,7 @@ cpp_library(
         "commands/config/session/CmdConfigSessionDiff.h",
         "commands/config/session/CmdConfigSessionRebase.h",
         "commands/config/vlan/CmdConfigVlan.h",
+        "commands/config/vlan/CmdConfigVlanConfig.h",
         "commands/config/vlan/CmdConfigVlanDefault.h",
         "commands/config/vlan/VlanManager.h",
         "commands/config/vlan/port/CmdConfigVlanPort.h",

fboss/cli/fboss2/CmdListConfig.cpp

@@ -103,6 +103,7 @@
 #include "fboss/cli/fboss2/commands/config/session/CmdConfigSessionDiff.h"
 #include "fboss/cli/fboss2/commands/config/session/CmdConfigSessionRebase.h"
 #include "fboss/cli/fboss2/commands/config/vlan/CmdConfigVlan.h"
+#include "fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanConfig.h"
 #include "fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanDefault.h"
 #include "fboss/cli/fboss2/commands/config/vlan/port/CmdConfigVlanPort.h"
 #include "fboss/cli/fboss2/commands/config/vlan/port/tagging_mode/CmdConfigVlanPortTaggingMode.h"
@@ -833,6 +834,12 @@ const CommandTree& kConfigCommandTree() {
           commandHandler<CmdConfigVlan>,
           argRegistrar<CmdConfigVlanTraits>,
           {{
+               "name",
+               "Configure the name of a VLAN",
+               commandHandler<CmdConfigVlanConfig>,
+               argRegistrar<CmdConfigVlanConfigTraits>,
+           },
+           {
                "port",
                "Configure VLAN port settings",
                commandHandler<CmdConfigVlanPort>,

fboss/cli/fboss2/CmdSubcommands.cpp

@@ -261,6 +261,7 @@ CLI::App* CmdSubcommands::addCommand(
         case utils::ObjectArgTypeId::OBJECT_ARG_TYPE_ID_NONE:
         case utils::ObjectArgTypeId::OBJECT_ARG_TYPE_ID_REVISION_LIST:
         case utils::ObjectArgTypeId::OBJECT_ARG_TYPE_VLAN_ID:
+        default:
           break;
       }
     }

fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanConfig.cpp

@@ -0,0 +1,69 @@
+/*
+ *  Copyright (c) 2004-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+
+#include "fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanConfig.h"
+
+#include <fmt/format.h>
+#include <cstdint>
+#include <iostream>
+#include <ostream>
+#include <stdexcept>
+#include <string>
+#include "fboss/agent/gen-cpp2/switch_config_types.h"
+#include "fboss/agent/types.h"
+#include "fboss/cli/fboss2/CmdHandler.cpp"
+#include "fboss/cli/fboss2/commands/config/vlan/CmdConfigVlan.h"
+#include "fboss/cli/fboss2/commands/config/vlan/VlanManager.h"
+#include "fboss/cli/fboss2/session/ConfigSession.h"
+#include "fboss/cli/fboss2/utils/HostInfo.h"
+
+namespace facebook::fboss {
+
+CmdConfigVlanConfigTraits::RetType CmdConfigVlanConfig::queryClient(
+    const HostInfo& /* hostInfo */,
+    const VlanId& vlanIdArg,
+    const ObjectArgType& arg) {
+  auto& swConfig = *ConfigSession::getInstance().getAgentConfig().sw();
+  VlanID vlanId(vlanIdArg.getVlanId());
+
+  // Ensure VLAN exists, auto-creating it if needed
+  auto [created, vlan] = VlanManager::createVlan(swConfig, vlanId);
+  if (created) {
+    std::cout << fmt::format("Created VLAN {}", static_cast<uint16_t>(vlanId))
+              << std::endl;
+  }
+
+  const std::string& attr = arg.getAttrName();
+  const std::string& value = arg.getValue();
+
+  if (attr == "name") {
+    vlan->name() = value;
+  } else {
+    throw std::invalid_argument(
+        fmt::format("Unknown VLAN attribute '{}'. Supported: name", attr));
+  }
+
+  ConfigSession::getInstance().saveConfig();
+
+  return fmt::format(
+      "Successfully configured VLAN {}: {}=\"{}\"",
+      static_cast<uint16_t>(vlanId),
+      attr,
+      value);
+}
+
+void CmdConfigVlanConfig::printOutput(const RetType& logMsg) {
+  std::cout << logMsg << std::endl;
+}
+
+// Explicit template instantiation
+template void CmdHandler<CmdConfigVlanConfig, CmdConfigVlanConfigTraits>::run();
+
+} // namespace facebook::fboss

fboss/cli/fboss2/commands/config/vlan/CmdConfigVlanConfig.h

@@ -0,0 +1,91 @@
+/*
+ *  Copyright (c) 2004-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+
+#pragma once
+
+#include <stdexcept>
+#include <string>
+#include <utility>
+#include <vector>
+#include "fboss/cli/fboss2/CmdHandler.h"
+#include "fboss/cli/fboss2/commands/config/vlan/CmdConfigVlan.h"
+#include "fboss/cli/fboss2/utils/CmdUtilsCommon.h"
+#include "fboss/cli/fboss2/utils/HostInfo.h"
+
+namespace facebook::fboss {
+
+/**
+ * Argument type for VLAN attribute configuration.
+ *
+ * Each concrete subclass encodes one attribute name (e.g. "name") so the
+ * handler can dispatch on it.  Adding a new attribute requires only:
+ *   1. A new subclass below with the appropriate getAttrName() value.
+ *   2. A new else-if branch in CmdConfigVlanConfig::queryClient().
+ *   3. A new subcommand entry in CmdListConfig.cpp pointing to the same
+ *      handler with the new arg class as ObjectArgType.
+ */
+class VlanConfigArg : public utils::BaseObjectArgType<std::string> {
+ public:
+  /* implicit */ VlanConfigArg( // NOLINT(google-explicit-constructor)
+      std::vector<std::string> v) {
+    if (v.size() != 1) {
+      throw std::invalid_argument(
+          "Expected <value>, got " + std::to_string(v.size()) + " argument(s)");
+    }
+    value_ = std::move(v[0]);
+  }
+
+  virtual std::string getAttrName() const = 0;
+
+  const std::string& getValue() const {
+    return value_;
+  }
+
+ private:
+  std::string value_;
+};
+
+/** Argument type for 'config vlan <id> name <value>'. */
+class VlanNameArg : public VlanConfigArg {
+ public:
+  /* implicit */ VlanNameArg( // NOLINT(google-explicit-constructor)
+      std::vector<std::string> v)
+      : VlanConfigArg(std::move(v)) {}
+
+  std::string getAttrName() const override {
+    return "name";
+  }
+};
+
+struct CmdConfigVlanConfigTraits : public WriteCommandTraits {
+  using ParentCmd = CmdConfigVlan;
+  static void addCliArg(CLI::App& cmd, std::vector<std::string>& args) {
+    cmd.add_option(
+        "vlan_config_value", args, "New value for the VLAN attribute");
+  }
+  using ObjectArgType = VlanNameArg;
+  using RetType = std::string;
+};
+
+class CmdConfigVlanConfig
+    : public CmdHandler<CmdConfigVlanConfig, CmdConfigVlanConfigTraits> {
+ public:
+  using ObjectArgType = CmdConfigVlanConfigTraits::ObjectArgType;
+  using RetType = CmdConfigVlanConfigTraits::RetType;
+
+  RetType queryClient(
+      const HostInfo& hostInfo,
+      const VlanId& vlanId,
+      const ObjectArgType& arg);
+
+  void printOutput(const RetType& logMsg);
+};
+
+} // namespace facebook::fboss

fboss/cli/fboss2/test/config/BUCK

@@ -24,6 +24,7 @@ cpp_unittest(
         "CmdConfigSessionDiffTest.cpp",
         "CmdConfigSessionTest.cpp",
         "CmdConfigTestBase.cpp",
+        "CmdConfigVlanConfigTest.cpp",
         "CmdConfigVlanDefaultTest.cpp",
         "CmdConfigVlanManagerTest.cpp",
         "CmdConfigVlanPortTaggingModeTest.cpp",