Disallow adding mesh local prefix as on-mesh prefix (#1699)

* disallow adding mesh local prefix

* update prefix match

src/core/net/ip6_address.cpp

@@ -180,14 +180,19 @@ uint8_t Address::GetScope(void) const
     return kGlobalScope;
 }
 
-uint8_t Address::PrefixMatch(const Address &aOther) const
+uint8_t Address::PrefixMatch(const uint8_t *aPrefixA, const uint8_t *aPrefixB, uint8_t aMaxLength)
 {
     uint8_t rval = 0;
     uint8_t diff;
 
-    for (uint8_t i = 0; i < sizeof(Address); i++)
+    if (aMaxLength > sizeof(Address))
     {
-        diff = mFields.m8[i] ^ aOther.mFields.m8[i];
+        aMaxLength = sizeof(Address);
+    }
+
+    for (uint8_t i = 0; i < aMaxLength; i++)
+    {
+        diff = aPrefixA[i] ^ aPrefixB[i];
 
         if (diff == 0)
         {
@@ -208,6 +213,11 @@ uint8_t Address::PrefixMatch(const Address &aOther) const
     return rval;
 }
 
+uint8_t Address::PrefixMatch(const Address &aOther) const
+{
+    return PrefixMatch(mFields.m8, aOther.mFields.m8, sizeof(Address));
+}
+
 bool Address::operator==(const Address &aOther) const
 {
     return memcmp(mFields.m8, aOther.mFields.m8, sizeof(mFields.m8)) == 0;

src/core/net/ip6_address.hpp

@@ -74,6 +74,7 @@ public:
     {
         kInterfaceIdentifierSize   = 8,  ///< Interface Identifier size in bytes.
         kIp6AddressStringSize      = 40, ///< Max buffer size in bytes to store an IPv6 address in string format.
+        kMeshLocalPrefixLength     = 64, ///< Length of Thread mesh local prefix.
     };
 
     /**
@@ -338,6 +339,18 @@ public:
      */
     const char *ToString(char *aBuf, uint16_t aSize) const;
 
+    /**
+     * This method returns the number of IPv6 prefix bits that match.
+     *
+     * @param[in]  aPrefixA     A pointer to the prefix to match.
+     * @param[in]  aPrefixB     A pointer to the prefix to match against.
+     * @param[in]  aMaxLength   Number of bytes of the two prefixes.
+     *
+     * @returns The number of prefix bits that match.
+     *
+     */
+    static uint8_t PrefixMatch(const uint8_t *aPrefixA, const uint8_t *aPrefixB, uint8_t aMaxLength);
+
 private:
     enum
     {

src/core/thread/network_data_local.cpp

@@ -58,9 +58,14 @@ Local::Local(ThreadNetif &aThreadNetif):
 ThreadError Local::AddOnMeshPrefix(const uint8_t *aPrefix, uint8_t aPrefixLength, int8_t aPrf,
                                    uint8_t aFlags, bool aStable)
 {
+    ThreadError error = kThreadError_None;
     PrefixTlv *prefixTlv;
     BorderRouterTlv *brTlv;
 
+    VerifyOrExit(Ip6::Address::PrefixMatch(aPrefix, mNetif.GetMle().GetMeshLocalPrefix(),
+                                           (aPrefixLength + 7) / 8) < Ip6::Address::kMeshLocalPrefixLength,
+                 error = kThreadError_InvalidArgs);
+
     RemoveOnMeshPrefix(aPrefix, aPrefixLength);
 
     prefixTlv = reinterpret_cast<PrefixTlv *>(mTlvs + mLength);
@@ -85,7 +90,9 @@ ThreadError Local::AddOnMeshPrefix(const uint8_t *aPrefix, uint8_t aPrefixLength
     ClearResubmitDelayTimer();
 
     otDumpDebgNetData(GetInstance(), "add prefix done", mTlvs, mLength);
-    return kThreadError_None;
+
+exit:
+    return error;
 }
 
 ThreadError Local::RemoveOnMeshPrefix(const uint8_t *aPrefix, uint8_t aPrefixLength)

src/core/thread/network_data_local_ftd.hpp

@@ -75,8 +75,9 @@ public:
      * @param[in]  aFlags         The Border Router Flags value.
      * @param[in]  aStable        The Stable value.
      *
-     * @retval kThreadError_None    Successfully added the Border Router entry.
-     * @retval kThreadError_NoBufs  Insufficient space to add the Border Router entry.
+     * @retval kThreadError_None        Successfully added the Border Router entry.
+     * @retval kThreadError_NoBufs      Insufficient space to add the Border Router entry.
+     * @retval kThreadError_InvalidArgs The prefix is mesh local prefix.
      *
      */
     ThreadError AddOnMeshPrefix(const uint8_t *aPrefix, uint8_t aPrefixLength, int8_t aPrf, uint8_t aFlags,