[routing-manager] set extra options to append to emitted RAs (#9945)

This commit introduces new API for setting vendor-specific extra
options to append to emitted Router Advertisement messages. Support
for this is also added in CLI under `br raoptions` command.

8 files changed, 139 insertions, 4 deletions

diff --git a/include/openthread/border_routing.h b/include/openthread/border_routing.h
index afd2d7e5f..1e5ff6144 100644
--- a/include/openthread/border_routing.h
+++ b/include/openthread/border_routing.h
@@ -240,6 +240,22 @@ void otBorderRoutingSetRouteInfoOptionPreference(otInstance *aInstance, otRouteP
 void otBorderRoutingClearRouteInfoOptionPreference(otInstance *aInstance);
 
 /**
+ * Sets additional options to append at the end of emitted Router Advertisement (RA) messages.
+ *
+ * The content of @p aOptions is copied internally, so it can be a temporary buffer (e.g., a stack allocated array).
+ *
+ * Subsequent calls to this function overwrite the previously set value.
+ *
+ * @param[in] aOptions   A pointer to the encoded options. Can be `NULL` to clear.
+ * @param[in] aLength    Number of bytes in @p aOptions.
+ *
+ * @retval OT_ERROR_NONE     Successfully set the extra option bytes.
+ * @retval OT_ERROR_NO_BUFS  Could not allocate buffer to save the buffer.
+ *
+ */
+otError otBorderRoutingSetExtraRouterAdvertOptions(otInstance *aInstance, const uint8_t *aOptions, uint16_t aLength);
+
+/**
  * Gets the current preference used for published routes in Network Data.
  *
  * The preference is determined as follows:
diff --git a/include/openthread/instance.h b/include/openthread/instance.h
index 84641d422..1ce766c02 100644
--- a/include/openthread/instance.h
+++ b/include/openthread/instance.h
@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (401)
+#define OPENTHREAD_API_VERSION (402)
 
 /**
  * @addtogroup api-instance
diff --git a/src/cli/README_BR.md b/src/cli/README_BR.md
index 189de8a6f..8376290d6 100644
--- a/src/cli/README_BR.md
+++ b/src/cli/README_BR.md
@@ -36,6 +36,7 @@ omrprefix
 onlinkprefix
 pd
 prefixtable
+raoptions
 rioprf
 routeprf
 routers
@@ -235,6 +236,28 @@ prefix:1200:abba:baba:0::/64, on-link:yes, ms-since-rx:29527, lifetime:1800, pre
 Done
 ```
 
+### raoptions
+
+Usage: `br raoptions <options>`
+
+Sets additional options to append at the end of emitted Router Advertisement (RA) messages. `<options>` provided as hex bytes.
+
+```bash
+> br raoptions 0400ff00020001
+Done
+```
+
+### raoptions clear
+
+Usage: `br raoptions clear`
+
+Clear any previously set additional options to append at the end of emitted Router Advertisement (RA) messages.
+
+```bash
+> br raoptions clear
+Done
+```
+
 ### rioprf
 
 Usage: `br rioprf`
diff --git a/src/cli/cli_br.cpp b/src/cli/cli_br.cpp
index 85590b925..53f2b3274 100644
--- a/src/cli/cli_br.cpp
+++ b/src/cli/cli_br.cpp
@@ -538,6 +538,46 @@ void Br::OutputRouterInfo(const otBorderRoutingRouterEntry &aEntry)
                aEntry.mStubRouterFlag);
 }
 
+template <> otError Br::Process<Cmd("raoptions")>(Arg aArgs[])
+{
+    static constexpr uint16_t kMaxExtraOptions = 800;
+
+    otError  error = OT_ERROR_NONE;
+    uint8_t  options[kMaxExtraOptions];
+    uint16_t length;
+
+    /**
+     * @cli br raoptions (set,clear)
+     * @code
+     * br raoptions 0400ff00020001
+     * Done
+     * @endcode
+     * @code
+     * br raoptions clear
+     * Done
+     * @endcode
+     * @cparam br raoptions @ca{options|clear}
+     * `br raoptions clear` passes a `nullptr` to #otBorderRoutingSetExtraRouterAdvertOptions.
+     * Otherwise, you can pass the `options` byte as hex data.
+     * @par api_copy
+     * #otBorderRoutingSetExtraRouterAdvertOptions
+     */
+    if (aArgs[0] == "clear")
+    {
+        length = 0;
+    }
+    else
+    {
+        length = sizeof(options);
+        SuccessOrExit(error = aArgs[0].ParseAsHexString(length, options));
+    }
+
+    error = otBorderRoutingSetExtraRouterAdvertOptions(GetInstancePtr(), length > 0 ? options : nullptr, length);
+
+exit:
+    return error;
+}
+
 template <> otError Br::Process<Cmd("rioprf")>(Arg aArgs[])
 {
     otError error = OT_ERROR_NONE;
@@ -702,6 +742,7 @@ otError Br::Process(Arg aArgs[])
         CmdEntry("pd"),
 #endif
         CmdEntry("prefixtable"),
+        CmdEntry("raoptions"),
         CmdEntry("rioprf"),
         CmdEntry("routeprf"),
         CmdEntry("routers"),
diff --git a/src/core/api/border_routing_api.cpp b/src/core/api/border_routing_api.cpp
index b62ee7041..7c8002dea 100644
--- a/src/core/api/border_routing_api.cpp
+++ b/src/core/api/border_routing_api.cpp
@@ -75,6 +75,11 @@ void otBorderRoutingClearRouteInfoOptionPreference(otInstance *aInstance)
     AsCoreType(aInstance).Get<BorderRouter::RoutingManager>().ClearRouteInfoOptionPreference();
 }
 
+otError otBorderRoutingSetExtraRouterAdvertOptions(otInstance *aInstance, const uint8_t *aOptions, uint16_t aLength)
+{
+    return AsCoreType(aInstance).Get<BorderRouter::RoutingManager>().SetExtraRouterAdvertOptions(aOptions, aLength);
+}
+
 otRoutePreference otBorderRoutingGetRoutePreference(otInstance *aInstance)
 {
     return static_cast<otRoutePreference>(
diff --git a/src/core/border_router/routing_manager.cpp b/src/core/border_router/routing_manager.cpp
index b4c1b0ae5..bebd795c8 100644
--- a/src/core/border_router/routing_manager.cpp
+++ b/src/core/border_router/routing_manager.cpp
@@ -363,6 +363,22 @@ exit:
     return;
 }
 
+Error RoutingManager::SetExtraRouterAdvertOptions(const uint8_t *aOptions, uint16_t aLength)
+{
+    Error error = kErrorNone;
+
+    if (aOptions == nullptr)
+    {
+        mExtraRaOptions.Free();
+    }
+    else
+    {
+        error = mExtraRaOptions.SetFrom(aOptions, aLength);
+    }
+
+    return error;
+}
+
 #if OPENTHREAD_CONFIG_SRP_SERVER_ENABLE
 void RoutingManager::HandleSrpServerAutoEnableMode(void)
 {
@@ -607,6 +623,11 @@ void RoutingManager::SendRouterAdvertisement(RouterAdvTxMode aRaTxMode)
         SuccessOrExit(error = mRioAdvertiser.AppendRios(raMsg));
     }
 
+    if (mExtraRaOptions.GetLength() > 0)
+    {
+        SuccessOrExit(error = raMsg.AppendBytes(mExtraRaOptions.GetBytes(), mExtraRaOptions.GetLength()));
+    }
+
     VerifyOrExit(raMsg.ContainsAnyOptions());
 
     destAddress.SetToLinkLocalAllNodesMulticast();
diff --git a/src/core/border_router/routing_manager.hpp b/src/core/border_router/routing_manager.hpp
index bb376eedc..37de6eca3 100644
--- a/src/core/border_router/routing_manager.hpp
+++ b/src/core/border_router/routing_manager.hpp
@@ -55,6 +55,7 @@
 #include "common/error.hpp"
 #include "common/heap_allocatable.hpp"
 #include "common/heap_array.hpp"
+#include "common/heap_data.hpp"
 #include "common/linked_list.hpp"
 #include "common/locator.hpp"
 #include "common/message.hpp"
@@ -234,6 +235,22 @@ public:
     void ClearRouteInfoOptionPreference(void) { mRioAdvertiser.ClearPreference(); }
 
     /**
+     * Sets additional options to append at the end of emitted Router Advertisement (RA) messages.
+     *
+     * The content of @p aOptions is copied internally, so can be a temporary stack variable.
+     *
+     * Subsequent calls to this method will overwrite the previously set value.
+     *
+     * @param[in] aOptions   A pointer to the encoded options. Can be `nullptr` to clear.
+     * @param[in] aLength    Number of bytes in @p aOptions.
+     *
+     * @retval kErrorNone     Successfully set the extra option bytes.
+     * @retval kErrorNoBufs   Could not allocate buffer to save the buffer.
+     *
+     */
+    Error SetExtraRouterAdvertOptions(const uint8_t *aOptions, uint16_t aLength);
+
+    /**
      * Gets the current preference used for published routes in Network Data.
      *
      * The preference is determined as follows:
@@ -1360,8 +1377,9 @@ private:
     PdPrefixManager mPdPrefixManager;
 #endif
 
-    RaInfo   mRaInfo;
-    RsSender mRsSender;
+    RaInfo     mRaInfo;
+    RsSender   mRsSender;
+    Heap::Data mExtraRaOptions;
 
     DiscoveredPrefixStaleTimer mDiscoveredPrefixStaleTimer;
     RoutingPolicyTimer         mRoutingPolicyTimer;
diff --git a/src/core/net/nd6.hpp b/src/core/net/nd6.hpp
index 260606b30..4178f181f 100644
--- a/src/core/net/nd6.hpp
+++ b/src/core/net/nd6.hpp
@@ -809,6 +809,18 @@ public:
         Error AppendFlagsExtensionOption(bool aStubRouterFlag);
 
         /**
+         * Appends bytes from a given buffer to the RA message.
+         *
+         * @param[in] aBytes     A pointer to the buffer containing the bytes to append.
+         * @param[in] aLength    The buffer length.
+         *
+         * @retval kErrorNone    Bytes are appended successfully.
+         * @retval kErrorNoBufs  Insufficient available buffers to grow the message.
+         *
+         */
+        Error AppendBytes(const uint8_t *aBytes, uint16_t aLength);
+
+        /**
          * Indicates whether or not the received RA message contains any options.
          *
          * @retval TRUE   If the RA message contains at least one option.
@@ -820,7 +832,6 @@ public:
     private:
         static constexpr uint16_t kCapacityIncrement = 256;
 
-        Error   AppendBytes(const uint8_t *aBytes, uint16_t aLength);
         Option *AppendOption(uint16_t aOptionSize);
 
         Heap::Array<uint8_t, kCapacityIncrement> mArray;