[ncp] add border routing InfraIf send ICMP6 ND (#10793)

src/lib/spinel/spinel.h

@@ -4763,6 +4763,16 @@ enum
      */
     SPINEL_PROP_INFRA_IF_RECV_ICMP6 = SPINEL_PROP_INFRA_IF__BEGIN + 2,
 
+    /// ICMP6 message sent by NCP and needs to be sent on the infrastructure interface.
+    /** Format: `L6d`
+     * Type: Unsolicited notifications only
+     *
+     * `L`: The infrastructure interface index.
+     * `6`: The IP6 destination address of the message to send.
+     * `d`: The data of the message to send.
+     */
+    SPINEL_PROP_INFRA_IF_SEND_ICMP6 = SPINEL_PROP_INFRA_IF__BEGIN + 3,
+
     SPINEL_PROP_INFRA_IF__END = 0x920,
 
     SPINEL_PROP_NEST__BEGIN = 0x3BC0,

src/ncp/ncp_base.hpp

@@ -224,6 +224,26 @@ public:
      */
     bool InfraIfHasAddress(uint32_t aInfraIfIndex, const otIp6Address *aAddress);
 
+    /**
+     * Send a ICMP6 ND message through the Infrastructure interface on the host.
+     *
+     * @param[in]  aInfraIfIndex  The index of the infrastructure interface this message is sent to.
+     * @param[in]  aDestAddress   The destination address this message is sent to.
+     * @param[in]  aBuffer        The ICMPv6 message buffer. The ICMPv6 checksum is left zero and the
+     *                            platform should do the checksum calculate.
+     * @param[in]  aBufferLength  The length of the message buffer.
+     *
+     * @note  Per RFC 4861, the implementation should send the message with IPv6 link-local source address
+     *        of interface @p aInfraIfIndex and IP Hop Limit 255.
+     *
+     * @retval OT_ERROR_NONE    Successfully sent the ICMPv6 message.
+     * @retval OT_ERROR_FAILED  Failed to send the ICMPv6 message.
+     */
+    otError InfraIfSendIcmp6Nd(uint32_t            aInfraIfIndex,
+                               const otIp6Address *aDestAddress,
+                               const uint8_t      *aBuffer,
+                               uint16_t            aBufferLength);
+
 protected:
     static constexpr uint8_t kBitsPerByte = 8; ///< Number of bits in a byte.
 

src/ncp/ncp_base_ftd.cpp

@@ -1488,6 +1488,24 @@ bool NcpBase::InfraIfHasAddress(uint32_t aInfraIfIndex, const otIp6Address *aAdd
     return aInfraIfIndex == mInfraIfIndex && InfraIfContainsAddress(*aAddress);
 }
 
+otError NcpBase::InfraIfSendIcmp6Nd(uint32_t            aInfraIfIndex,
+                                    const otIp6Address *aDestAddress,
+                                    const uint8_t      *aBuffer,
+                                    uint16_t            aBufferLength)
+{
+    otError error  = OT_ERROR_NONE;
+    uint8_t header = SPINEL_HEADER_FLAG | SPINEL_HEADER_IID_0;
+
+    SuccessOrExit(error = mEncoder.BeginFrame(header, SPINEL_CMD_PROP_VALUE_IS, SPINEL_PROP_INFRA_IF_SEND_ICMP6));
+    SuccessOrExit(error = mEncoder.WriteUint32(aInfraIfIndex));
+    SuccessOrExit(error = mEncoder.WriteIp6Address(*aDestAddress));
+    SuccessOrExit(error = mEncoder.WriteDataWithLen(aBuffer, aBufferLength));
+    SuccessOrExit(error = mEncoder.EndFrame());
+
+exit:
+    return error;
+}
+
 #endif // OPENTHREAD_CONFIG_NCP_INFRA_IF_ENABLE && OPENTHREAD_CONFIG_BORDER_ROUTING_ENABLE
 
 } // namespace Ncp

src/ncp/platform/infra_if.cpp

@@ -41,12 +41,9 @@ otError otPlatInfraIfSendIcmp6Nd(uint32_t            aInfraIfIndex,
                                  const uint8_t      *aBuffer,
                                  uint16_t            aBufferLength)
 {
-    OT_UNUSED_VARIABLE(aInfraIfIndex);
+    ot::Ncp::NcpBase *ncp = ot::Ncp::NcpBase::GetNcpInstance();
-    OT_UNUSED_VARIABLE(aDestAddress);
-    OT_UNUSED_VARIABLE(aBuffer);
-    OT_UNUSED_VARIABLE(aBufferLength);
 
-    return OT_ERROR_NOT_IMPLEMENTED;
+    return ncp->InfraIfSendIcmp6Nd(aInfraIfIndex, aDestAddress, aBuffer, aBufferLength);
 }
 
 otError otPlatInfraIfDiscoverNat64Prefix(uint32_t aInfraIfIndex)