[4294] Unit tests and MySql now support IPv6 lease stat recounting

src/lib/dhcpsrv/cfg_subnets6.cc
    - CfgSubnets6::removeStatistics() - added removal of declined stats
    - CfgSubnets6::updateStatistics() - added call to recountAddressStats6()

src/lib/dhcpsrv/mysql_lease_mgr.h
src/lib/dhcpsrv/mysql_lease_mgr.cc
    - Added TaggedStatement RECOUNT_LEASE6_STATS
    - MySqlAddressStatsQuery6 - new MySql derivation of AddressStatsQuery6
    - MySqlLeaseMgr::startAddressStatsQuery6() - new virtual method which
    creates and starts a MySqlAddressStatsQuery6

src/lib/dhcpsrv/tests/generic_lease_mgr_unittest.h
src/lib/dhcpsrv/tests/generic_lease_mgr_unittest.cc
    - GenericLeaseMgrTest::checkAddressStats4 renamed to checkAddressStats as
    it applies to either v4 or v6
    - GenericLeaseMgrTest::makeLease6() - new method which creates a minimal
    IPv6 lease and adds it to lease storage
    - GenericLeaseMgrTest::testRecountAddressStats6() - new method which
    checks IPv6 lease stats recounting

src/lib/dhcpsrv/tests/mysql_lease_mgr_unittest.cc
    - TEST_F(MySqlLeaseMgrTest, recountAddressStats6) - new test

src/lib/dhcpsrv/mysql_lease_mgr.cc

@@ -1,4 +1,4 @@
-// Copyright (C) 2012-2015 Internet Systems Consortium, Inc. ("ISC")
+// Copyright (C) 2012-2016 Internet Systems Consortium, Inc. ("ISC")
 //
 // This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -206,8 +206,14 @@ TaggedStatement tagged_statements[] = {
                         "state = ? "
                             "WHERE address = ?"},
     {MySqlLeaseMgr::RECOUNT_LEASE4_STATS,
-                    "SELECT subnet_id, state, count(state) as state_count "
-                        "FROM lease4 GROUP BY subnet_id, state ORDER BY subnet_id"},
+     "SELECT subnet_id, state, count(state) as state_count "
+     "  FROM lease4 GROUP BY subnet_id, state ORDER BY subnet_id"},
+
+    {MySqlLeaseMgr::RECOUNT_LEASE6_STATS,
+     "SELECT subnet_id, lease_type, state, count(state) as state_count"
+     "  FROM lease6 GROUP BY subnet_id, lease_type, state "
+     "  ORDER BY subnet_id" },
+
     // End of list sentinel
     {MySqlLeaseMgr::NUM_STATEMENTS, NULL}
 };
@@ -1353,9 +1359,154 @@ MySqlLeaseMgr::startAddressStatsQuery4() {
     return(query);
 }
 
+/// @brief MySql derivation of the IPv6 statistical lease data query
+///
+/// This class is used to recalculate IPv6 lease statistics for MySQL
+/// lease storage.  It does so by executing a query which returns a result
+/// containining contain one row per monitored state per subnet, ordered
+/// by subnet id in ascending order.
+///
+class MySqlAddressStatsQuery6 : public AddressStatsQuery6 {
+public:
+    /// @brief Constructor
+    ///
+    /// @param conn A open connection to the database housing the lease data
+    MySqlAddressStatsQuery6(MySqlConnection& conn);
 
+    /// @brief Destructor
+    virtual ~MySqlAddressStatsQuery6();
 
+    /// @brief Creates the IPv6 lease statistical data result set
+    ///
+    /// The result set is populated by executing an SQL query against the
+    /// lease4 table which sums the leases per lease state per subnet id.
+    /// The query used is the prepared statement identified by
+    /// MySqlLeaseMgr::RECOUNT_LEASE6_STATS.  This method creates the binds
+    /// the statement to the output bind array  and then executes the
+    /// statement.
+    void start();
 
+    /// @brief Fetches the next row in the result set
+    ///
+    /// Once the internal result set has been populated by invoking the
+    /// the start() method, this method is used to iterate over the
+    /// result set rows. Once the last row has been fetched, subsequent
+    /// calls will return false.
+    ///
+    /// @param row Storage for the fetched row
+    ///
+    /// @return True if the fetch succeeded, false if there are no more
+    /// rows to fetch.
+    bool getNextRow(AddressStatsRow6& row);
+
+private:
+
+    /// @brief Analyzes the given statement outcome status
+    ///
+    /// Wrapper method around the MySqlConnection:checkError() that is
+    /// used to generate the appropriate exception if the status indicates
+    /// an error.
+    ////
+    /// a DbOperation error
+    /// @param status The MySQL statement execution outcome status
+    /// @param what invocation context message which will be included in
+    /// any exception
+    void checkError(int status, const char* what) const;
+
+    /// @brief Database connection to use to execute the query
+    MySqlConnection& conn_;
+
+    /// @brief The query's prepared statement
+    MYSQL_STMT *statement_;
+
+    /// @brief Bind array used to store the query result set;
+    std::vector<MYSQL_BIND> bind_;
+
+    /// @brief Receives subnet ID when fetching a row
+    uint32_t subnet_id_;
+    /// @brief Receives the lease type when fetching a row
+    uint32_t lease_type_;
+    /// @brief Receives the lease state when fetching a row
+    uint32_t lease_state_;
+    /// @brief Receives the state count when fetching a row
+    uint32_t state_count_;
+};
+
+MySqlAddressStatsQuery6::MySqlAddressStatsQuery6(MySqlConnection& conn)
+    : conn_(conn), statement_(conn_.statements_[MySqlLeaseMgr
+                                                ::RECOUNT_LEASE6_STATS]),
+      bind_(4) {
+}
+
+MySqlAddressStatsQuery6::~MySqlAddressStatsQuery6() {
+    (void) mysql_stmt_free_result(statement_);
+}
+
+void
+MySqlAddressStatsQuery6::start() {
+    // subnet_id: unsigned int
+    bind_[0].buffer_type = MYSQL_TYPE_LONG;
+    bind_[0].buffer = reinterpret_cast<char*>(&subnet_id_);
+    bind_[0].is_unsigned = MLM_TRUE;
+
+    // lease type:  uint32_t
+    bind_[1].buffer_type = MYSQL_TYPE_LONG;
+    bind_[1].buffer = reinterpret_cast<char*>(&lease_type_);
+    bind_[1].is_unsigned = MLM_TRUE;
+
+    // state:  uint32_t
+    bind_[2].buffer_type = MYSQL_TYPE_LONG;
+    bind_[2].buffer = reinterpret_cast<char*>(&lease_state_);
+    bind_[2].is_unsigned = MLM_TRUE;
+
+    // state_count_: uint32_t
+    bind_[3].buffer_type = MYSQL_TYPE_LONG;
+    bind_[3].buffer = reinterpret_cast<char*>(&state_count_);
+    bind_[3].is_unsigned = MLM_TRUE;
+
+    // Set up the MYSQL_BIND array for the data being returned
+    // and bind it to the statement.
+    int status = mysql_stmt_bind_result(statement_, &bind_[0]);
+    checkError(status, "RECOUNT_LEASE6_STATS: outbound binding failed");
+
+    // Execute the statement
+    status = mysql_stmt_execute(statement_);
+    checkError(status, "RECOUNT_LEASE6_STATS: unable to execute");
+
+    // Ensure that all the lease information is retrieved in one go to avoid
+    // overhead of going back and forth between client and server.
+    status = mysql_stmt_store_result(statement_);
+    checkError(status, "RECOUNT_LEASE6_STATS: results storage setup failed");
+}
+
+bool
+MySqlAddressStatsQuery6::getNextRow(AddressStatsRow6& row) {
+    bool have_row = false;
+    int status = mysql_stmt_fetch(statement_);
+    if (status == MLM_MYSQL_FETCH_SUCCESS) {
+        row.subnet_id_ = static_cast<SubnetID>(subnet_id_);
+        row.lease_type_ = static_cast<Lease::Type>(lease_type_);
+        row.lease_state_ = static_cast<Lease::LeaseState>(lease_state_);
+        row.state_count_ = state_count_;
+        have_row = true;
+    } else if (status != MYSQL_NO_DATA) {
+        checkError(status, "RECOUNT_LEASE6_STATS: getNextRow failed");
+    }
+
+    return (have_row);
+}
+
+void
+MySqlAddressStatsQuery6::checkError(int status, const char* what) const {
+    conn_.checkError(status, MySqlLeaseMgr::RECOUNT_LEASE6_STATS, what);
+}
+
+AddressStatsQuery6Ptr
+MySqlLeaseMgr::startAddressStatsQuery6() {
+    AddressStatsQuery6Ptr query(new MySqlAddressStatsQuery6(conn_));
+    query->start();
+    return(query);
+}
 
 // MySqlLeaseMgr Constructor and Destructor