[master] Merge branch 'trac3234' (DHCP subnet-id increase fix)

Conflicts:
	ChangeLog

ChangeLog

@@ -1,3 +1,9 @@
+730.	[bug]		tomek
+	b10-dhcp4, b10-dhcp6: Both servers used to unnecessarily increase
+	subnet-id values after reconfiguration. The subnet-ids are now reset
+	to 1 every time a server is reconfigured.
+	(Trac #3234, git 31e416087685a6dadc3047fdbb0927bbf60095aa)
+
 729.	[bug]		marcin
 	b10-dhcp4 discards DHCPv4 messages carrying server identifiers
 	which don't match server identifiers used by the server.

doc/guide/bind10-guide.xml

@@ -4471,6 +4471,21 @@ Dhcp4/subnet4	[]	list	(default)
       development and should be treated as <quote>not implemented
       yet</quote>, rather than actual limitations.</para>
       <itemizedlist>
+          <listitem> <!-- see tickets #3234, #3281 -->
+            <para>
+              On-line configuration has some limitations. Adding new subnets or
+              modifying existing ones work, as is removing the last subnet from
+              the list. However, removing non-last (e.g. removing subnet 1,2 or 3 if
+              there are 4 subnets configured) will cause issues. The problem is
+              caused by simplistic subnet-id assignment. The subnets are always
+              numbered, starting from 1. That subnet-id is then used in leases
+              that are stored in the lease database. Removing non-last subnet will
+              cause the configuration information to mismatch data in the lease
+              database. It is possible to manually update subnet-id fields in
+              MySQL database, but it is awkward and error prone process. A better
+              reconfiguration support is planned.
+            </para>
+          </listitem>
           <listitem>
           <para>
             On startup, the DHCPv4 server does not get the full configuration from
@@ -5384,6 +5399,22 @@ should include options from the isc option space:
       yet</quote>, rather than actual limitations.</para>
       <itemizedlist>
 
+          <listitem> <!-- see tickets #3234, #3281 -->
+            <para>
+              On-line configuration has some limitations. Adding new subnets or
+              modifying existing ones work, as is removing the last subnet from
+              the list. However, removing non-last (e.g. removing subnet 1,2 or 3 if
+              there are 4 subnets configured) will cause issues. The problem is
+              caused by simplistic subnet-id assignment. The subnets are always
+              numbered, starting from 1. That subnet-id is then used in leases
+              that are stored in the lease database. Removing non-last subnet will
+              cause the configuration information to mismatch data in the lease
+              database. It is possible to manually update subnet-id fields in
+              MySQL database, but it is awkward and error prone process. A better
+              reconfiguration support is planned.
+            </para>
+          </listitem>
+
         <listitem>
           <para>
             On startup, the DHCPv6 server does not get the full configuration from

src/bin/dhcp4/config_parser.cc

@@ -433,6 +433,10 @@ configureDhcp4Server(Dhcpv4Srv&, isc::data::ConstElementPtr config_set) {
     LOG_DEBUG(dhcp4_logger, DBG_DHCP4_COMMAND,
               DHCP4_CONFIG_START).arg(config_set->str());
 
+    // Before starting any subnet operations, let's reset the subnet-id counter,
+    // so newly recreated configuration starts with first subnet-id equal 1.
+    Subnet::resetSubnetID();
+
     // Some of the values specified in the configuration depend on
     // other values. Typically, the values in the subnet4 structure
     // depend on the global values. Also, option values configuration

src/bin/dhcp4/tests/config_parser_unittest.cc

@@ -410,8 +410,195 @@ TEST_F(Dhcp4ParserTest, subnetGlobalDefaults) {
     EXPECT_EQ(1000, subnet->getT1());
     EXPECT_EQ(2000, subnet->getT2());
     EXPECT_EQ(4000, subnet->getValid());
+
+    // Check that subnet-id is 1
+    EXPECT_EQ(1, subnet->getID());
 }
 
+// Goal of this test is to verify that multiple subnets get unique
+// subnet-ids. Also, test checks that it's possible to do reconfiguration
+// multiple times.
+TEST_F(Dhcp4ParserTest, multipleSubnets) {
+    ConstElementPtr x;
+    string config = "{ \"interfaces\": [ \"*\" ],"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet4\": [ { "
+        "    \"pool\": [ \"192.0.2.1 - 192.0.2.100\" ],"
+        "    \"subnet\": \"192.0.2.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.3.101 - 192.0.3.150\" ],"
+        "    \"subnet\": \"192.0.3.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.4.101 - 192.0.4.150\" ],"
+        "    \"subnet\": \"192.0.4.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.5.101 - 192.0.5.150\" ],"
+        "    \"subnet\": \"192.0.5.0/24\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    ElementPtr json = Element::fromJSON(config);
+
+    EXPECT_NO_THROW(x = configureDhcp4Server(*srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    int cnt = 0; // Number of reconfigurations
+
+    do {
+        ElementPtr json = Element::fromJSON(config);
+
+        EXPECT_NO_THROW(x = configureDhcp4Server(*srv_, json));
+        ASSERT_TRUE(x);
+        comment_ = parseAnswer(rcode_, x);
+        ASSERT_EQ(0, rcode_);
+
+        const Subnet4Collection* subnets = CfgMgr::instance().getSubnets4();
+        ASSERT_TRUE(subnets);
+        ASSERT_EQ(4, subnets->size()); // We expect 4 subnets
+
+        // Check subnet-ids of each subnet (it should be monotonously increasing)
+        EXPECT_EQ(1, subnets->at(0)->getID());
+        EXPECT_EQ(2, subnets->at(1)->getID());
+        EXPECT_EQ(3, subnets->at(2)->getID());
+        EXPECT_EQ(4, subnets->at(3)->getID());
+
+        // Repeat reconfiguration process 10 times and check that the subnet-id
+        // is set to the same value. Technically, just two iterations would be
+        // sufficient, but it's nice to have a test that exercises reconfiguration
+        // a bit.
+    } while (++cnt < 10);
+}
+
+// Goal of this test is to verify that a previously configured subnet can be
+// deleted in subsequent reconfiguration.
+TEST_F(Dhcp4ParserTest, reconfigureRemoveSubnet) {
+    ConstElementPtr x;
+
+    // All four subnets
+    string config4 = "{ \"interfaces\": [ \"*\" ],"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet4\": [ { "
+        "    \"pool\": [ \"192.0.2.1 - 192.0.2.100\" ],"
+        "    \"subnet\": \"192.0.2.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.3.101 - 192.0.3.150\" ],"
+        "    \"subnet\": \"192.0.3.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.4.101 - 192.0.4.150\" ],"
+        "    \"subnet\": \"192.0.4.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.5.101 - 192.0.5.150\" ],"
+        "    \"subnet\": \"192.0.5.0/24\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    // Three subnets (the last one removed)
+    string config_first3 = "{ \"interfaces\": [ \"*\" ],"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet4\": [ { "
+        "    \"pool\": [ \"192.0.2.1 - 192.0.2.100\" ],"
+        "    \"subnet\": \"192.0.2.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.3.101 - 192.0.3.150\" ],"
+        "    \"subnet\": \"192.0.3.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.4.101 - 192.0.4.150\" ],"
+        "    \"subnet\": \"192.0.4.0/24\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    // Second subnet removed
+    string config_second_removed = "{ \"interfaces\": [ \"*\" ],"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet4\": [ { "
+        "    \"pool\": [ \"192.0.2.1 - 192.0.2.100\" ],"
+        "    \"subnet\": \"192.0.2.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.4.101 - 192.0.4.150\" ],"
+        "    \"subnet\": \"192.0.4.0/24\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"192.0.5.101 - 192.0.5.150\" ],"
+        "    \"subnet\": \"192.0.5.0/24\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    // CASE 1: Configure 4 subnets, then reconfigure and remove the
+    // last one.
+
+    ElementPtr json = Element::fromJSON(config4);
+    EXPECT_NO_THROW(x = configureDhcp4Server(*srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    const Subnet4Collection* subnets = CfgMgr::instance().getSubnets4();
+    ASSERT_TRUE(subnets);
+    ASSERT_EQ(4, subnets->size()); // We expect 4 subnets
+
+    // Do the reconfiguration (the last subnet is removed)
+    json = Element::fromJSON(config_first3);
+    EXPECT_NO_THROW(x = configureDhcp4Server(*srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    subnets = CfgMgr::instance().getSubnets4();
+    ASSERT_TRUE(subnets);
+    ASSERT_EQ(3, subnets->size()); // We expect 3 subnets now (4th is removed)
+
+    // Check subnet-ids of each subnet (it should be monotonously increasing)
+    EXPECT_EQ(1, subnets->at(0)->getID());
+    EXPECT_EQ(2, subnets->at(1)->getID());
+    EXPECT_EQ(3, subnets->at(2)->getID());
+
+    /// CASE 2: Configure 4 subnets, then reconfigure and remove one
+    /// from in between (not first, not last)
+
+#if 0
+    /// @todo: Uncomment subnet removal test as part of #3281.
+    json = Element::fromJSON(config4);
+    EXPECT_NO_THROW(x = configureDhcp4Server(*srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    // Do reconfiguration
+    json = Element::fromJSON(config_second_removed);
+    EXPECT_NO_THROW(x = configureDhcp4Server(*srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    subnets = CfgMgr::instance().getSubnets4();
+    ASSERT_TRUE(subnets);
+    ASSERT_EQ(3, subnets->size()); // We expect 4 subnets
+
+    EXPECT_EQ(1, subnets->at(0)->getID());
+    // The second subnet (with subnet-id = 2) is no longer there
+    EXPECT_EQ(3, subnets->at(1)->getID());
+    EXPECT_EQ(4, subnets->at(2)->getID());
+#endif
+
+}
+
+/// @todo: implement subnet removal test as part of #3281.
+
 // Checks if the next-server defined as global parameter is taken into
 // consideration.
 TEST_F(Dhcp4ParserTest, nextServerGlobal) {

src/bin/dhcp6/config_parser.cc

@@ -646,6 +646,10 @@ configureDhcp6Server(Dhcpv6Srv&, isc::data::ConstElementPtr config_set) {
     LOG_DEBUG(dhcp6_logger, DBG_DHCP6_COMMAND,
               DHCP6_CONFIG_START).arg(config_set->str());
 
+    // Before starting any subnet operations, let's reset the subnet-id counter,
+    // so newly recreated configuration starts with first subnet-id equal 1.
+    Subnet::resetSubnetID();
+
     // Some of the values specified in the configuration depend on
     // other values. Typically, the values in the subnet6 structure
     // depend on the global values. Also, option values configuration

src/bin/dhcp6/tests/config_parser_unittest.cc

@@ -436,8 +436,190 @@ TEST_F(Dhcp6ParserTest, subnetGlobalDefaults) {
     EXPECT_EQ(2000, subnet->getT2());
     EXPECT_EQ(3000, subnet->getPreferred());
     EXPECT_EQ(4000, subnet->getValid());
+
+    // Check that subnet-id is 1
+    EXPECT_EQ(1, subnet->getID());
+}
+
+// Goal of this test is to verify that multiple subnets get unique
+// subnet-ids. Also, test checks that it's possible to do reconfiguration
+// multiple times.
+TEST_F(Dhcp6ParserTest, multipleSubnets) {
+    ConstElementPtr x;
+    string config = "{ \"interfaces\": [ \"*\" ],"
+        "\"preferred-lifetime\": 3000,"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet6\": [ { "
+        "    \"pool\": [ \"2001:db8:1::/80\" ],"
+        "    \"subnet\": \"2001:db8:1::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:2::/80\" ],"
+        "    \"subnet\": \"2001:db8:2::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:3::/80\" ],"
+        "    \"subnet\": \"2001:db8:3::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:4::/80\" ],"
+        "    \"subnet\": \"2001:db8:4::/64\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    int cnt = 0; // Number of reconfigurations
+
+    do {
+        ElementPtr json = Element::fromJSON(config);
+
+        EXPECT_NO_THROW(x = configureDhcp6Server(srv_, json));
+        ASSERT_TRUE(x);
+        comment_ = parseAnswer(rcode_, x);
+        ASSERT_EQ(0, rcode_);
+
+        const Subnet6Collection* subnets = CfgMgr::instance().getSubnets6();
+        ASSERT_TRUE(subnets);
+        ASSERT_EQ(4, subnets->size()); // We expect 4 subnets
+
+        // Check subnet-ids of each subnet (it should be monotonously increasing)
+        EXPECT_EQ(1, subnets->at(0)->getID());
+        EXPECT_EQ(2, subnets->at(1)->getID());
+        EXPECT_EQ(3, subnets->at(2)->getID());
+        EXPECT_EQ(4, subnets->at(3)->getID());
+
+        // Repeat reconfiguration process 10 times and check that the subnet-id
+        // is set to the same value. Technically, just two iterations would be
+        // sufficient, but it's nice to have a test that exercises reconfiguration
+        // a bit.
+    } while (++cnt < 10);
+}
+
+// Goal of this test is to verify that a previously configured subnet can be
+// deleted in subsequent reconfiguration.
+TEST_F(Dhcp6ParserTest, reconfigureRemoveSubnet) {
+    ConstElementPtr x;
+
+    // All four subnets
+    string config4 = "{ \"interfaces\": [ \"*\" ],"
+        "\"preferred-lifetime\": 3000,"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet6\": [ { "
+        "    \"pool\": [ \"2001:db8:1::/80\" ],"
+        "    \"subnet\": \"2001:db8:1::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:2::/80\" ],"
+        "    \"subnet\": \"2001:db8:2::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:3::/80\" ],"
+        "    \"subnet\": \"2001:db8:3::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:4::/80\" ],"
+        "    \"subnet\": \"2001:db8:4::/64\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    // Three subnets (the last one removed)
+    string config_first3 = "{ \"interfaces\": [ \"*\" ],"
+        "\"preferred-lifetime\": 3000,"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet6\": [ { "
+        "    \"pool\": [ \"2001:db8:1::/80\" ],"
+        "    \"subnet\": \"2001:db8:1::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:2::/80\" ],"
+        "    \"subnet\": \"2001:db8:2::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:3::/80\" ],"
+        "    \"subnet\": \"2001:db8:3::/64\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    // Second subnet removed
+    string config_second_removed = "{ \"interfaces\": [ \"*\" ],"
+        "\"preferred-lifetime\": 3000,"
+        "\"rebind-timer\": 2000, "
+        "\"renew-timer\": 1000, "
+        "\"subnet6\": [ { "
+        "    \"pool\": [ \"2001:db8:1::/80\" ],"
+        "    \"subnet\": \"2001:db8:1::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:3::/80\" ],"
+        "    \"subnet\": \"2001:db8:3::/64\" "
+        " },"
+        " {"
+        "    \"pool\": [ \"2001:db8:4::/80\" ],"
+        "    \"subnet\": \"2001:db8:4::/64\" "
+        " } ],"
+        "\"valid-lifetime\": 4000 }";
+
+    // CASE 1: Configure 4 subnets, then reconfigure and remove the
+    // last one.
+
+    ElementPtr json = Element::fromJSON(config4);
+    EXPECT_NO_THROW(x = configureDhcp6Server(srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    const Subnet6Collection* subnets = CfgMgr::instance().getSubnets6();
+    ASSERT_TRUE(subnets);
+    ASSERT_EQ(4, subnets->size()); // We expect 4 subnets
+
+    // Do the reconfiguration (the last subnet is removed)
+    json = Element::fromJSON(config_first3);
+    EXPECT_NO_THROW(x = configureDhcp6Server(srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    subnets = CfgMgr::instance().getSubnets6();
+    ASSERT_TRUE(subnets);
+    ASSERT_EQ(3, subnets->size()); // We expect 3 subnets now (4th is removed)
+
+    EXPECT_EQ(1, subnets->at(0)->getID());
+    EXPECT_EQ(2, subnets->at(1)->getID());
+    EXPECT_EQ(3, subnets->at(2)->getID());
+
+    /// CASE 2: Configure 4 subnets, then reconfigure and remove one
+    /// from in between (not first, not last)
+
+#if 0
+    /// @todo: Uncomment subnet removal test as part of #3281.
+    json = Element::fromJSON(config4);
+    EXPECT_NO_THROW(x = configureDhcp6Server(srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    // Do reconfiguration
+    json = Element::fromJSON(config_second_removed);
+    EXPECT_NO_THROW(x = configureDhcp6Server(srv_, json));
+    ASSERT_TRUE(x);
+    comment_ = parseAnswer(rcode_, x);
+    ASSERT_EQ(0, rcode_);
+
+    subnets = CfgMgr::instance().getSubnets6();
+    ASSERT_TRUE(subnets);
+    ASSERT_EQ(3, subnets->size()); // We expect 4 subnets
+
+    EXPECT_EQ(1, subnets->at(0)->getID());
+    // The second subnet (with subnet-id = 2) is no longer there
+    EXPECT_EQ(3, subnets->at(1)->getID());
+    EXPECT_EQ(4, subnets->at(2)->getID());
+#endif
 }
 
+
+
 // This test checks if it is possible to override global values
 // on a per subnet basis.
 TEST_F(Dhcp6ParserTest, subnetLocal) {

src/lib/dhcpsrv/subnet.cc

@@ -24,11 +24,14 @@ using namespace isc::asiolink;
 namespace isc {
 namespace dhcp {
 
+// This is an initial value of subnet-id. See comments in subnet.h for details.
+SubnetID Subnet::static_id_ = 1;
+
 Subnet::Subnet(const isc::asiolink::IOAddress& prefix, uint8_t len,
                const Triplet<uint32_t>& t1,
                const Triplet<uint32_t>& t2,
                const Triplet<uint32_t>& valid_lifetime)
-    :id_(getNextID()), prefix_(prefix), prefix_len_(len), t1_(t1),
+    :id_(generateNextID()), prefix_(prefix), prefix_len_(len), t1_(t1),
      t2_(t2), valid_(valid_lifetime),
      last_allocated_ia_(lastAddrInPrefix(prefix, len)),
      last_allocated_ta_(lastAddrInPrefix(prefix, len)),

src/lib/dhcpsrv/subnet.h

@@ -366,6 +366,15 @@ public:
     /// @return textual representation
     virtual std::string toText() const;
 
+    /// @brief Resets subnet-id counter to its initial value (1)
+    ///
+    /// This should be called during reconfiguration, before any new
+    /// subnet objects are created. It will ensure that the subnet_id will
+    /// be consistent between reconfigures.
+    static void resetSubnetID() {
+        static_id_ = 1;
+    }
+
 protected:
     /// @brief Returns all pools (non-const variant)
     ///
@@ -378,7 +387,12 @@ protected:
     /// @brief Protected constructor
     //
     /// By making the constructor protected, we make sure that noone will
-    /// ever instantiate that class. Pool4 and Pool6 should be used instead.
+    /// ever instantiate that class. Subnet4 and Subnet6 should be used instead.
+    ///
+    /// This constructor assigns a new subnet-id (see @ref generateNextID).
+    /// This subnet-id has unique value that is strictly monotonously increasing
+    /// for each subnet, until it is explicitly reset back to 1 during
+    /// reconfiguration process.
     Subnet(const isc::asiolink::IOAddress& prefix, uint8_t len,
            const Triplet<uint32_t>& t1,
            const Triplet<uint32_t>& t2,
@@ -390,12 +404,24 @@ protected:
     /// derive from this class.
     virtual ~Subnet() { };
 
+    /// @brief keeps the subnet-id value
+    ///
+    /// It is inreased every time a new Subnet object is created.
+    /// It is reset (@ref resetSubnetId) every time reconfiguration occurs.
+    ///
+    /// Static value initialized in subnet.cc.
+    static SubnetID static_id_;
+
     /// @brief returns the next unique Subnet-ID
     ///
+    /// This method generates and returns the next unique subnet-id.
+    /// It is a strictly monotonously increasing value (1,2,3,...) for
+    /// each new Subnet object created. It can be explicitly reset
+    /// back to 1 during reconfiguration (@ref resetSubnetID).
+    ///
     /// @return the next unique Subnet-ID
-    static SubnetID getNextID() {
-        static SubnetID id = 0;
-        return (id++);
+    static SubnetID generateNextID() {
+        return (static_id_++);
     }
 
     /// @brief Checks if used pool type is valid
@@ -495,6 +521,8 @@ public:
 
     /// @brief Constructor with all parameters
     ///
+    /// This constructor calls Subnet::Subnet, where subnet-id is generated.
+    ///
     /// @param prefix Subnet4 prefix
     /// @param length prefix length
     /// @param t1 renewal timer (in seconds)
@@ -559,6 +587,8 @@ public:
 
     /// @brief Constructor with all parameters
     ///
+    /// This constructor calls Subnet::Subnet, where subnet-id is generated.
+    ///
     /// @param prefix Subnet6 prefix
     /// @param length prefix length
     /// @param t1 renewal timer (in seconds)