[posix] add posix support for sending RA messages to routing manager

include/openthread/icmp6.h

@@ -80,7 +80,8 @@ typedef enum otIcmp6Code
     OT_ICMP6_CODE_FRAGM_REAS_TIME_EX   = 1, ///< Fragment Reassembly Time Exceeded
 } otIcmp6Code;
 
-#define OT_ICMP6_HEADER_DATA_SIZE 4 ///< Size of an message specific data of ICMPv6 Header.
+#define OT_ICMP6_HEADER_DATA_SIZE 4        ///< Size of ICMPv6 Header.
+#define OT_ICMP6_ROUTER_ADVERT_MIN_SIZE 16 ///< Size of a Router Advertisement message without any options.
 
 /**
  * @struct otIcmp6Header

include/openthread/instance.h

@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (332)
+#define OPENTHREAD_API_VERSION (333)
 
 /**
  * @addtogroup api-instance

include/openthread/ip6.h

@@ -56,6 +56,8 @@ extern "C" {
 #define OT_IP6_PREFIX_BITSIZE (OT_IP6_PREFIX_SIZE * 8) ///< Size of an IPv6 prefix (bits)
 #define OT_IP6_IID_SIZE 8                              ///< Size of an IPv6 Interface Identifier (bytes)
 #define OT_IP6_ADDRESS_SIZE 16                         ///< Size of an IPv6 address (bytes)
+#define OT_IP6_HEADER_SIZE 40                          ///< Size of an IPv6 header (bytes)
+#define OT_IP6_HEADER_PROTO_OFFSET 6                   ///< Offset of the proto field in the IPv6 header (bytes)
 
 /**
  * @struct otIp6InterfaceIdentifier

src/posix/platform/netif.cpp

@@ -146,6 +146,7 @@ extern int
 #include <openthread/message.h>
 #include <openthread/nat64.h>
 #include <openthread/netdata.h>
+#include <openthread/platform/border_routing.h>
 #include <openthread/platform/misc.h>
 
 #include "common/code_utils.hpp"
@@ -1021,6 +1022,71 @@ static void processReceive(otMessage *aMessage, void *aContext)
     }
 }
 
+#if OPENTHREAD_CONFIG_NAT64_TRANSLATOR_ENABLE || OPENTHREAD_CONFIG_BORDER_ROUTING_DHCP6_PD_ENABLE
+static constexpr uint8_t kIpVersion4 = 4;
+static constexpr uint8_t kIpVersion6 = 6;
+
+static uint8_t getIpVersion(const uint8_t *data)
+{
+    assert(data != nullptr);
+
+    // Mute compiler warnings.
+    OT_UNUSED_VARIABLE(kIpVersion4);
+    OT_UNUSED_VARIABLE(kIpVersion6);
+
+    return (static_cast<uint8_t>(data[0]) >> 4) & 0x0F;
+}
+#endif
+
+#if OPENTHREAD_CONFIG_BORDER_ROUTING_DHCP6_PD_ENABLE
+
+/**
+ * Returns nullptr if data does not point to a valid ICMPv6 RA message.
+ *
+ */
+static const uint8_t *getIcmp6RaMessage(const uint8_t *data, ssize_t length)
+{
+    const uint8_t *ret = nullptr;
+    otIcmp6Header  icmpHeader;
+
+    VerifyOrExit(length >= OT_IP6_HEADER_SIZE + OT_ICMP6_ROUTER_ADVERT_MIN_SIZE);
+    VerifyOrExit(getIpVersion(data) == kIpVersion6);
+    VerifyOrExit(data[OT_IP6_HEADER_PROTO_OFFSET] == OT_IP6_PROTO_ICMP6);
+
+    ret = data + OT_IP6_HEADER_SIZE;
+    memcpy(&icmpHeader, ret, sizeof(icmpHeader));
+    VerifyOrExit(icmpHeader.mType == OT_ICMP6_TYPE_ROUTER_ADVERT, ret = nullptr);
+    VerifyOrExit(icmpHeader.mCode == 0, ret = nullptr);
+
+exit:
+    return ret;
+}
+
+/**
+ * Returns false if the message is not an ICMPv6 RA message.
+ *
+ */
+static otError tryProcessIcmp6RaMessage(otInstance *aInstance, const uint8_t *data, ssize_t length)
+{
+    otError        error = OT_ERROR_NONE;
+    const uint8_t *ra    = getIcmp6RaMessage(data, length);
+    ssize_t        raLength;
+
+    VerifyOrExit(ra != nullptr, error = OT_ERROR_INVALID_ARGS);
+
+#if OPENTHREAD_POSIX_LOG_TUN_PACKETS
+    otLogInfoPlat("[netif] RA to BorderRouting (%hu bytes)", static_cast<uint16_t>(length));
+    otDumpInfoPlat("", data, static_cast<size_t>(length));
+#endif
+
+    raLength = length + (ra - data);
+    otPlatBorderRoutingProcessIcmp6Ra(aInstance, ra, raLength);
+
+exit:
+    return error;
+}
+#endif // OPENTHREAD_CONFIG_BORDER_ROUTING_DHCP6_PD_ENABLE
+
 static void processTransmit(otInstance *aInstance)
 {
     otMessage *message = nullptr;
@@ -1046,13 +1112,20 @@ static void processTransmit(otInstance *aInstance)
     }
 #endif
 
+#if OPENTHREAD_CONFIG_BORDER_ROUTING_DHCP6_PD_ENABLE
+    if (tryProcessIcmp6RaMessage(aInstance, reinterpret_cast<uint8_t *>(&packet[offset]), rval) == OT_ERROR_NONE)
+    {
+        ExitNow();
+    }
+#endif
+
     {
         otMessageSettings settings;
 
         settings.mLinkSecurityEnabled = (otThreadGetDeviceRole(aInstance) != OT_DEVICE_ROLE_DISABLED);
         settings.mPriority            = OT_MESSAGE_PRIORITY_LOW;
 #if OPENTHREAD_CONFIG_NAT64_TRANSLATOR_ENABLE
-        isIp4   = (packet[offset] & 0xf0) == 0x40;
+        isIp4   = (getIpVersion(reinterpret_cast<uint8_t *>(&packet[offset])) == kIpVersion4);
         message = isIp4 ? otIp4NewMessage(aInstance, &settings) : otIp6NewMessage(aInstance, &settings);
 #else
         message = otIp6NewMessage(aInstance, &settings);