[mle] fix connectivity parse if default sed capacity is not included (#3061)

src/core/openthread-core-default-config.h

@@ -1807,4 +1807,27 @@
 #define OPENTHREAD_CONFIG_RETX_POLL_PERIOD 1000
 #endif
 
+/**
+ * @def OPENTHREAD_CONFIG_DEFAULT_SED_BUFFER_SIZE
+ *
+ * This setting configures the default buffer size for IPv6 datagram destined for an attached SED.
+ * A Thread Router MUST be able to buffer at least one 1280-octet IPv6 datagram for an attached SED according to
+ * the Thread Conformance Specification.
+ *
+ */
+#ifndef OPENTHREAD_CONFIG_DEFAULT_SED_BUFFER_SIZE
+#define OPENTHREAD_CONFIG_DEFAULT_SED_BUFFER_SIZE 1280
+#endif
+
+/**
+ * @def OPENTHREAD_CONFIG_DEFAULT_SED_DATAGRAM_COUNT
+ *
+ * This setting configures the default datagram count of 106-octet IPv6 datagram per attached SED.
+ * A Thread Router MUST be able to buffer at least one 106-octet IPv6 datagram per attached SED according to
+ * the Thread Conformance Specification.
+ *
+ */
+#ifndef OPENTHREAD_CONFIG_DEFAULT_SED_DATAGRAM_COUNT
+#define OPENTHREAD_CONFIG_DEFAULT_SED_DATAGRAM_COUNT 1
+#endif
 #endif // OPENTHREAD_CORE_DEFAULT_CONFIG_H_

src/core/thread/mle_router.cpp

@@ -4292,8 +4292,8 @@ void MleRouter::FillConnectivityTlv(ConnectivityTlv &aTlv)
 
     aTlv.SetLeaderCost((cost < kMaxRouteCost) ? cost : static_cast<uint8_t>(kMaxRouteCost));
     aTlv.SetIdSequence(mRouterTable.GetRouterIdSequence());
-    aTlv.SetSedBufferSize(1280);
-    aTlv.SetSedDatagramCount(1);
+    aTlv.SetSedBufferSize(OPENTHREAD_CONFIG_DEFAULT_SED_BUFFER_SIZE);
+    aTlv.SetSedDatagramCount(OPENTHREAD_CONFIG_DEFAULT_SED_DATAGRAM_COUNT);
 }
 
 otError MleRouter::AppendConnectivity(Message &aMessage)

src/core/thread/mle_tlvs.hpp

@@ -1294,10 +1294,19 @@ public:
      */
     bool IsValid(void) const
     {
-        return (GetLength() == sizeof(*this) - sizeof(Tlv) ||
-                GetLength() == sizeof(*this) - sizeof(Tlv) - sizeof(mSedBufferSize) - sizeof(mSedDatagramCount));
+        return IsSedBufferingIncluded() ||
+               (GetLength() == sizeof(*this) - sizeof(Tlv) - sizeof(mSedBufferSize) - sizeof(mSedDatagramCount));
     }
 
+    /**
+     * This method indicates whether or not the sed buffer size and datagram count are included.
+     *
+     * @retval TRUE   If the sed buffer size and datagram count are included.
+     * @retval FALSE  If the sed buffer size and datagram count are not included.
+     *
+     */
+    bool IsSedBufferingIncluded(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
+
     /**
      * This method returns the Parent Priority value.
      *
@@ -1422,7 +1431,16 @@ public:
      * @returns The SED Buffer Size value.
      *
      */
-    uint16_t GetSedBufferSize(void) const { return HostSwap16(mSedBufferSize); }
+    uint16_t GetSedBufferSize(void) const
+    {
+        uint16_t buffersize = OPENTHREAD_CONFIG_DEFAULT_SED_BUFFER_SIZE;
+
+        if (IsSedBufferingIncluded())
+        {
+            buffersize = HostSwap16(mSedBufferSize);
+        }
+        return buffersize;
+    }
 
     /**
      * This method sets the SED Buffer Size value.
@@ -1438,7 +1456,16 @@ public:
      * @returns The SED Datagram Count value.
      *
      */
-    uint8_t GetSedDatagramCount(void) const { return mSedDatagramCount; }
+    uint8_t GetSedDatagramCount(void) const
+    {
+        uint8_t count = OPENTHREAD_CONFIG_DEFAULT_SED_DATAGRAM_COUNT;
+
+        if (IsSedBufferingIncluded())
+        {
+            count = mSedDatagramCount;
+        }
+        return count;
+    }
 
     /**
      * This method sets the SED Datagram Count value.