[routing-manager] add SetIfIndex in RoutingManager (#9305)

This commit adds `SetIfIndex` method to `RoutingManager` class. This
method allows the infrastructure interface to be changed. The user may
initialize multiple interfaces and choose one interface as
infrastructure interface. During run time, there might be some
networking congestion or other network issue. The user can change the
infrastructure interface via this function.

This commit also adds docs for the `init` command.

include/openthread/border_routing.h

@@ -133,6 +133,8 @@ typedef enum
  * Initializes the Border Routing Manager on given infrastructure interface.
  *
  * @note  This method MUST be called before any other otBorderRouting* APIs.
+ * @note  This method can be re-called to change the infrastructure interface, but the Border Routing Manager should be
+ *        disabled first, and re-enabled after.
  *
  * @param[in]  aInstance          A pointer to an OpenThread instance.
  * @param[in]  aInfraIfIndex      The infrastructure interface index.
@@ -140,11 +142,12 @@ typedef enum
  *                                interface is running.
  *
  * @retval  OT_ERROR_NONE           Successfully started the Border Routing Manager on given infrastructure.
- * @retval  OT_ERROR_INVALID_STATE  The Border Routing Manager has already been initialized.
+ * @retval  OT_ERROR_INVALID_STATE  The Border Routing Manager is in a state other than disabled or uninitialized.
  * @retval  OT_ERROR_INVALID_ARGS   The index of the infrastructure interface is not valid.
  * @retval  OT_ERROR_FAILED         Internal failure. Usually due to failure in generating random prefixes.
  *
  * @sa otPlatInfraIfStateChanged.
+ * @sa otBorderRoutingSetEnabled.
  *
  */
 otError otBorderRoutingInit(otInstance *aInstance, uint32_t aInfraIfIndex, bool aInfraIfIsRunning);

include/openthread/instance.h

@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (347)
+#define OPENTHREAD_API_VERSION (348)
 
 /**
  * @addtogroup api-instance

src/cli/README_BR.md

@@ -8,6 +8,7 @@ Usage : `br [command] ...`
 - [disable](#disable)
 - [enable](#enable)
 - [help](#help)
+- [init](#init)
 - [nat64prefix](#nat64prefix)
 - [omrprefix](#omrprefix)
 - [onlinkprefix](#onlinkprefix)
@@ -38,6 +39,17 @@ state
 Done
 ```
 
+### init
+
+Usage: `br init <interface> <enabled>`
+
+Initializes the Border Routing Manager on given infrastructure interface.
+
+```bash
+> br init 2 1
+Done
+```
+
 ### enable
 
 Usage: `br enable`

src/core/border_router/infra_if.hpp

@@ -114,6 +114,14 @@ public:
      */
     uint32_t GetIfIndex(void) const { return mIfIndex; }
 
+    /**
+     * Sets the infrastructure interface index.
+     *
+     * @param[in]  aIfIndex        The infrastructure interface index.
+     *
+     */
+    void SetIfIndex(uint32_t aIfIndex) { mIfIndex = aIfIndex; }
+
     /**
      * Indicates whether or not the infra interface has the given IPv6 address assigned.
      *

src/core/border_router/routing_manager.cpp

@@ -94,16 +94,24 @@ Error RoutingManager::Init(uint32_t aInfraIfIndex, bool aInfraIfIsRunning)
 {
     Error error;
 
-    LogInfo("Initializing - InfraIfIndex:%lu", ToUlong(aInfraIfIndex));
+    VerifyOrExit(GetState() == kStateUninitialized || GetState() == kStateDisabled, error = kErrorInvalidState);
 
-    SuccessOrExit(error = mInfraIf.Init(aInfraIfIndex));
-
-    SuccessOrExit(error = LoadOrGenerateRandomBrUlaPrefix());
-    mOmrPrefixManager.Init(mBrUlaPrefix);
+    if (!mInfraIf.IsInitialized())
+    {
+        LogInfo("Initializing - InfraIfIndex:%lu", ToUlong(aInfraIfIndex));
+        SuccessOrExit(error = mInfraIf.Init(aInfraIfIndex));
+        SuccessOrExit(error = LoadOrGenerateRandomBrUlaPrefix());
+        mOmrPrefixManager.Init(mBrUlaPrefix);
 #if OPENTHREAD_CONFIG_NAT64_BORDER_ROUTING_ENABLE
-    mNat64PrefixManager.GenerateLocalPrefix(mBrUlaPrefix);
+        mNat64PrefixManager.GenerateLocalPrefix(mBrUlaPrefix);
 #endif
-    mOnLinkPrefixManager.Init();
+        mOnLinkPrefixManager.Init();
+    }
+    else if (aInfraIfIndex != mInfraIf.GetIfIndex())
+    {
+        LogInfo("Reinitializing - InfraIfIndex:%lu -> %lu", ToUlong(mInfraIf.GetIfIndex()), ToUlong(aInfraIfIndex));
+        mInfraIf.SetIfIndex(aInfraIfIndex);
+    }
 
     error = mInfraIf.HandleStateChanged(mInfraIf.GetIfIndex(), aInfraIfIsRunning);