[3747] Modification to how server identifies the client for Release.

This change comes along with the new tests for DHCPRELEASE in the
separate file, and having a separate test fixture.

src/bin/dhcp4/dhcp4_messages.mes

@@ -349,20 +349,6 @@ removed from the database during RELEASE message processing.
 This warning message is printed when client attempts to release a lease,
 but no such lease is known to the server.
 
-% DHCP4_RELEASE_FAIL_WRONG_CLIENT_ID client (client-id %2) tried to release address %1, but it belongs to client (client-id %3)
-This warning message indicates that client tried to release an address
-that belongs to a different client. This should not happen in normal
-circumstances and may indicate a misconfiguration of the client.  However,
-since the client releasing the address will stop using it anyway, there
-is a good chance that the situation will correct itself.
-
-% DHCP4_RELEASE_FAIL_WRONG_HWADDR client (client-id %2) tried to release address %1, but sent from a wrong hardware address (%3)
-This warning message indicates that client tried to release an address
-that does belong to it, but the lease information was associated with
-a different hardware address. One possible reason for using different
-hardware address is that a cloned virtual machine was not updated and
-both clones use the same client-id.
-
 % DHCP4_REQUEST_CLASS_PROCESSING_FAILED client class specific processing failed for DHCPREQUEST
 This debug message means that the server processing that is unique for each
 client class has reported a failure. The response packet will not be sent.

src/bin/dhcp4/dhcp4_srv.cc

@@ -1579,26 +1579,9 @@ Dhcpv4Srv::processRelease(Pkt4Ptr& release) {
             return;
         }
 
-        // Does the hardware address match? We don't want one client releasing
-        // second client's leases. Note that we're comparing the hardware
-        // addresses only, not hardware types or sources of the hardware
-        // addresses. Thus we don't use HWAddr::equals().
-        if (lease->hwaddr_->hwaddr_ != release->getHWAddr()->hwaddr_) {
-            /// @todo: Print hwaddr from lease as part of ticket #2589
-            LOG_DEBUG(dhcp4_logger, DBG_DHCP4_DETAIL, DHCP4_RELEASE_FAIL_WRONG_HWADDR)
-                .arg(release->getCiaddr().toText())
-                .arg(client_id ? client_id->toText() : "(no client-id)")
-                .arg(release->getHWAddr()->toText());
-            return;
-        }
-
-        // Does the lease have client-id info? If it has, then check it with what
-        // the client sent us.
-        if (lease->client_id_ && client_id && *lease->client_id_ != *client_id) {
-            LOG_DEBUG(dhcp4_logger, DBG_DHCP4_DETAIL, DHCP4_RELEASE_FAIL_WRONG_CLIENT_ID)
-                .arg(release->getCiaddr().toText())
-                .arg(client_id->toText())
-                .arg(lease->client_id_->toText());
+        if (!lease->belongsToClient(release->getHWAddr(), client_id)) {
+            /// @todo add debug message here when we merge the code with the
+            /// changes from #3806.
             return;
         }
 

src/bin/dhcp4/dhcp4_srv.h

@@ -397,7 +397,7 @@ protected:
     /// @return ACK or NAK message
     Pkt4Ptr processRequest(Pkt4Ptr& request);
 
-    /// @brief Stub function that will handle incoming RELEASE messages.
+    /// @brief Processes incoming DHCPRELEASE messages.
     ///
     /// In DHCPv4, server does not respond to RELEASE messages, therefore
     /// this function does not return anything.
@@ -410,9 +410,11 @@ protected:
     /// @param decline message received from client
     void processDecline(Pkt4Ptr& decline);
 
-    /// @brief Stub function that will handle incoming INFORM messages.
+    /// @brief Processes incoming DHCPINFORM messages.
     ///
     /// @param inform message received from client
+    ///
+    /// @return DHCPACK to be sent to the client.
     Pkt4Ptr processInform(Pkt4Ptr& inform);
 
     /// @brief Appends options requested by client.

src/bin/dhcp4/tests/Makefile.am

@@ -87,6 +87,7 @@ dhcp4_unittests_SOURCES += marker_file.cc
 dhcp4_unittests_SOURCES += dhcp4_client.cc dhcp4_client.h
 dhcp4_unittests_SOURCES += inform_unittest.cc
 dhcp4_unittests_SOURCES += dora_unittest.cc
+dhcp4_unittests_SOURCES += release_unittest.cc
 
 if CONFIG_BACKEND_BUNDY
 # For Bundy backend, we only need to run the usual tests. There are no

src/bin/dhcp4/tests/dhcp4_client.cc

@@ -254,6 +254,25 @@ Dhcp4Client::doInform(const bool set_ciaddr) {
 }
 
 void
+Dhcp4Client::doRelease() {
+    if (config_.lease_.addr_ == IOAddress::IPV4_ZERO_ADDRESS()) {
+        isc_throw(Dhcp4ClientError, "failed to send the release"
+                  " message because client doesn't have a lease");
+    }
+    context_.query_ = createMsg(DHCPRELEASE);
+    // Set ciaddr to the address which we want to release.
+    context_.query_->setCiaddr(config_.lease_.addr_);
+    // Include client identifier.
+    appendClientId();
+
+    // Remove configuration.
+    config_.reset();
+
+    // Send the message to the server.
+    sendMsg(context_.query_);
+}
+
+void
 Dhcp4Client::doRequest() {
     context_.query_ = createMsg(DHCPREQUEST);
 

src/bin/dhcp4/tests/dhcp4_client.h

@@ -166,6 +166,12 @@ public:
     /// an error occurs.
     void doInform(const bool set_ciaddr = true);
 
+    /// @brief Sends DHCPRELEASE Message to the server.
+    ///
+    /// This method simulates sending the DHCPRELEASE message to the server.
+    /// The released lease is removed from the client's configuration.
+    void doRelease();
+
     /// @brief Sends DHCPREQUEST Message to the server and receives a response.
     ///
     /// This method simulates sending the DHCPREQUEST message to the server and

src/bin/dhcp4/tests/dhcp4_srv_unittest.cc

@@ -943,169 +943,6 @@ TEST_F(Dhcpv4SrvTest, sanityCheck) {
                  RFCViolation);
 }
 
-// This test verifies that incoming (positive) RELEASE can be handled properly.
-// As there is no REPLY in DHCPv4, the only thing to verify here is that
-// the lease is indeed removed from the database.
-TEST_F(Dhcpv4SrvTest, ReleaseBasic) {
-    boost::scoped_ptr<NakedDhcpv4Srv> srv;
-    ASSERT_NO_THROW(srv.reset(new NakedDhcpv4Srv(0)));
-
-    const IOAddress addr("192.0.2.106");
-    const uint32_t temp_t1 = 50;
-    const uint32_t temp_t2 = 75;
-    const uint32_t temp_valid = 100;
-    const time_t temp_timestamp = time(NULL) - 10;
-
-    // Generate client-id also duid_
-    OptionPtr clientid = generateClientId();
-
-    // Check that the address we are about to use is indeed in pool
-    ASSERT_TRUE(subnet_->inPool(Lease::TYPE_V4, addr));
-
-    // Let's create a lease and put it in the LeaseMgr
-    uint8_t hwaddr_data[] = { 0, 0xfe, 0xfe, 0xfe, 0xfe, 0xfe};
-    HWAddrPtr hwaddr(new HWAddr(hwaddr_data, sizeof(hwaddr_data), HTYPE_ETHER));
-    Lease4Ptr used(new Lease4(addr, hwaddr,
-                              &client_id_->getDuid()[0], client_id_->getDuid().size(),
-                              temp_valid, temp_t1, temp_t2, temp_timestamp,
-                              subnet_->getID()));
-    ASSERT_TRUE(LeaseMgrFactory::instance().addLease(used));
-
-    // Check that the lease is really in the database
-    Lease4Ptr l = LeaseMgrFactory::instance().getLease4(addr);
-    ASSERT_TRUE(l);
-
-    // Let's create a RELEASE
-    // Generate client-id also duid_
-    Pkt4Ptr rel = Pkt4Ptr(new Pkt4(DHCPRELEASE, 1234));
-    rel->setRemoteAddr(addr);
-    rel->setCiaddr(addr);
-    rel->addOption(clientid);
-    rel->addOption(srv->getServerID());
-    rel->setHWAddr(hwaddr);
-    rel->setIface("eth0");
-
-    // Pass it to the server and hope for a REPLY
-    // Note: this is no response to RELEASE in DHCPv4
-    EXPECT_NO_THROW(srv->processRelease(rel));
-
-    // The lease should be gone from LeaseMgr
-    l = LeaseMgrFactory::instance().getLease4(addr);
-    EXPECT_FALSE(l);
-
-    // Try to get the lease by hardware address
-    Lease4Collection leases = LeaseMgrFactory::instance().getLease4(*hwaddr);
-    EXPECT_EQ(leases.size(), 0);
-
-    // Try to get it by hw/subnet_id combination
-    l = LeaseMgrFactory::instance().getLease4(*hwaddr, subnet_->getID());
-    EXPECT_FALSE(l);
-
-    // Try by client-id
-    leases = LeaseMgrFactory::instance().getLease4(*client_id_);
-    EXPECT_EQ(leases.size(), 0);
-
-    // Try by client-id/subnet-id
-    l = LeaseMgrFactory::instance().getLease4(*client_id_, subnet_->getID());
-    EXPECT_FALSE(l);
-
-    // Ok, the lease is *really* not there.
-}
-
-// This test verifies that incoming (invalid) RELEASE can be handled properly.
-//
-// This test checks 3 scenarios:
-// 1. there is no such lease at all
-// 2. there is such a lease, but it is assigned to a different IAID
-// 3. there is such a lease, but it belongs to a different client
-TEST_F(Dhcpv4SrvTest, ReleaseReject) {
-    boost::scoped_ptr<NakedDhcpv4Srv> srv;
-    ASSERT_NO_THROW(srv.reset(new NakedDhcpv4Srv(0)));
-
-    const IOAddress addr("192.0.2.106");
-    const uint32_t t1 = 50;
-    const uint32_t t2 = 75;
-    const uint32_t valid = 100;
-    const time_t timestamp = time(NULL) - 10;
-
-    // Let's create a lease and put it in the LeaseMgr
-    uint8_t bogus_mac_addr[] = { 0, 0xfe, 0xfe, 0xfe, 0xfe, 0xfe};
-    HWAddrPtr bogus_hw(new HWAddr(bogus_mac_addr, sizeof(bogus_mac_addr), HTYPE_ETHER));
-    OptionPtr bogus_clientid = generateClientId(7); // different length
-
-    // Generate client-id also duid_
-    OptionPtr clientid = generateClientId();
-
-    // Check that the address we are about to use is indeed in pool
-    ASSERT_TRUE(subnet_->inPool(Lease::TYPE_V4, addr));
-
-    // Let's create a RELEASE
-    // Generate client-id also duid_
-    Pkt4Ptr rel = Pkt4Ptr(new Pkt4(DHCPRELEASE, 1234));
-    rel->setRemoteAddr(addr);
-    rel->setCiaddr(addr);
-    rel->addOption(clientid);
-    rel->addOption(srv->getServerID());
-    rel->setHWAddr(bogus_hw);
-    rel->setIface("eth0");
-
-    // Case 1: No lease known to server
-    SCOPED_TRACE("CASE 1: Lease is not known to the server");
-
-    // There is nothing to check here. The lease is not there and server does
-    // not send anything back. This case is enumerated here just for keeping
-    // parity with similar test in DHCPv6.
-    EXPECT_NO_THROW(srv->processRelease(rel));
-
-    // CASE 2: Lease is known and belongs to this client, but to a different hardware
-    SCOPED_TRACE("CASE 2: Lease is known and belongs to this client, but uses different HW addr");
-
-    // Let's create a lease and put it in the LeaseMgr
-    uint8_t mac_addr[] = { 0, 0x1, 0x2, 0x3, 0x4, 0x5};
-    HWAddrPtr hw(new HWAddr(mac_addr, sizeof(mac_addr), HTYPE_ETHER));
-    Lease4Ptr used(new Lease4(addr, hw,
-                              &client_id_->getDuid()[0], client_id_->getDuid().size(),
-                              valid, t1, t2, timestamp, subnet_->getID()));
-    ASSERT_TRUE(LeaseMgrFactory::instance().addLease(used));
-    // Check that the lease is really in the database
-    Lease4Ptr l = LeaseMgrFactory::instance().getLease4(addr);
-    ASSERT_TRUE(l);
-
-    rel->setHWAddr(bogus_hw);
-
-    EXPECT_NO_THROW(srv->processRelease(rel));
-
-    // Check that the lease was not removed (due to hardware address mis-match)
-    l = LeaseMgrFactory::instance().getLease4(addr);
-    ASSERT_TRUE(l);
-
-    // CASE 3: Lease belongs to a client with different client-id
-    SCOPED_TRACE("CASE 3: Lease belongs to a client with different client-id");
-
-    rel->setHWAddr(hw); // proper HW address this time
-    rel->delOption(DHO_DHCP_CLIENT_IDENTIFIER);
-    rel->addOption(bogus_clientid); // but invalid client-id
-
-    OptionPtr x = rel->getOption(DHO_DHCP_CLIENT_IDENTIFIER);
-
-    EXPECT_NO_THROW(srv->processRelease(rel));
-
-    // Check that the lease is still there
-    l = LeaseMgrFactory::instance().getLease4(addr);
-    ASSERT_TRUE(l);
-
-    // Final sanity check. Verify that with valid hw and client-id release is successful
-    rel->delOption(DHO_DHCP_CLIENT_IDENTIFIER);
-    rel->addOption(clientid);
-
-    // It should work this time
-    EXPECT_NO_THROW(srv->processRelease(rel));
-
-    // Check that the lease is not there
-    l = LeaseMgrFactory::instance().getLease4(addr);
-    EXPECT_FALSE(l);
-}
-
 // Checks if received relay agent info option is echoed back to the client
 TEST_F(Dhcpv4SrvTest, relayAgentInfoEcho) {
     IfaceMgrTestConfig test_config(true);

src/bin/dhcp4/tests/release_unittest.cc

@@ -0,0 +1,334 @@
+// Copyright (C) 2015 Internet Systems Consortium, Inc. ("ISC")
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+#include <config.h>
+#include <asiolink/io_address.h>
+#include <cc/data.h>
+#include <dhcp/dhcp4.h>
+#include <dhcp/tests/iface_mgr_test_config.h>
+#include <dhcpsrv/cfgmgr.h>
+#include <dhcpsrv/subnet_id.h>
+#include <dhcp4/tests/dhcp4_test_utils.h>
+#include <dhcp4/tests/dhcp4_client.h>
+#include <boost/shared_ptr.hpp>
+
+using namespace isc;
+using namespace isc::asiolink;
+using namespace isc::data;
+using namespace isc::dhcp;
+using namespace isc::dhcp::test;
+
+namespace {
+
+/// @brief Set of JSON configurations used throughout the Release tests.
+///
+/// - Configuration 0:
+///   - Used for testing Release message processing
+///   - 1 subnet: 10.0.0.0/24
+///   - 1 pool: 10.0.0.10-10.0.0.100
+///   - Router option present: 10.0.0.200 and 10.0.0.201
+const char* RELEASE_CONFIGS[] = {
+// Configuration 0
+    "{ \"interfaces-config\": {"
+        "      \"interfaces\": [ \"*\" ]"
+        "},"
+        "\"valid-lifetime\": 600,"
+        "\"subnet4\": [ { "
+        "    \"subnet\": \"10.0.0.0/24\", "
+        "    \"id\": 1,"
+        "    \"pools\": [ { \"pool\": \"10.0.0.10-10.0.0.100\" } ],"
+        "    \"option-data\": [ {"
+        "        \"name\": \"routers\","
+        "        \"code\": 3,"
+        "        \"data\": \"10.0.0.200,10.0.0.201\","
+        "        \"csv-format\": true,"
+        "        \"space\": \"dhcp4\""
+        "    } ]"
+        " } ]"
+    "}",
+
+// Configuration 1
+    "{ \"interfaces-config\": {"
+        "      \"interfaces\": [ \"*\" ]"
+        "},"
+
+        "\"valid-lifetime\": 600,"
+        "\"subnet4\": [ { "
+        "    \"subnet\": \"192.0.2.0/24\", "
+        "    \"option-data\": [ {"
+        "        \"name\": \"routers\","
+        "        \"code\": 3,"
+        "        \"data\": \"192.0.2.200,192.0.2.201\","
+        "        \"csv-format\": true,"
+        "        \"space\": \"dhcp4\""
+        "    },"
+        "    {"
+        "        \"name\": \"domain-name-servers\","
+        "        \"code\": 6,"
+        "        \"data\": \"192.0.2.202,192.0.2.203\","
+        "        \"csv-format\": true,"
+        "        \"space\": \"dhcp4\""
+        "    },"
+        "    {"
+        "        \"name\": \"log-servers\","
+        "        \"code\": 7,"
+        "        \"data\": \"10.0.0.200,10.0.0.201\","
+        "        \"csv-format\": true,"
+        "        \"space\": \"dhcp4\""
+        "    },"
+        "    {"
+        "        \"name\": \"cookie-servers\","
+        "        \"code\": 8,"
+        "        \"data\": \"10.0.0.202,10.0.0.203\","
+        "        \"csv-format\": true,"
+        "        \"space\": \"dhcp4\""
+        "    } ]"
+        " } ]"
+    "}",
+
+// Configuration 2
+    "{ \"interfaces-config\": {"
+        "      \"interfaces\": [ \"*\" ]"
+        "},"
+        "\"valid-lifetime\": 600,"
+        "\"subnet4\": [ { "
+        "    \"subnet\": \"10.0.0.0/24\", "
+        "    \"pools\": [ { \"pool\": \"10.0.0.10-10.0.0.100\" } ],"
+        "    \"reservations\": [ "
+        "       {"
+        "         \"hw-address\": \"aa:bb:cc:dd:ee:ff\","
+        "         \"ip-address\": \"10.0.0.7\""
+        "       }"
+        "    ]"
+        "} ]"
+    "}"
+};
+
+/// @brief Test fixture class for testing 4-way (DORA) exchanges.
+///
+/// @todo Currently there is a limit number of test cases covered here.
+/// In the future it is planned that the tests from the
+/// dhcp4_srv_unittest.cc will be migrated here and will use the
+/// @c Dhcp4Client class.
+class ReleaseTest : public Dhcpv4SrvTest {
+public:
+
+    /// @brief Constructor.
+    ///
+    /// Sets up fake interfaces.
+    ReleaseTest()
+        : Dhcpv4SrvTest(),
+          iface_mgr_test_config_(true) {
+        IfaceMgr::instance().openSockets4();
+    }
+
+    /// @brief Performs 4-way exchange to obtain new lease.
+    ///
+    /// @param client Client to be used to obtain a lease.
+    void acquireLease(Dhcp4Client& client);
+
+    /// @brief Test successful release for different identifiers.
+    ///
+    /// @param hw_address_1 HW Address to be used to acquire the lease.
+    /// @param client_id_1 Client id to be used to acquire the lease.
+    /// @param hw_address_2 HW Address to be used to release the lease.
+    /// @param client_id_2 Client id to be used to release the lease.
+    void successfulRelease(const std::string& hw_address_1,
+                           const std::string& client_id_1,
+                           const std::string& hw_address_2,
+                           const std::string& client_id_2);
+
+    /// @brief Test unsuccessful release for different identifiers.
+    ///
+    /// @param hw_address_1 HW Address to be used to acquire the lease.
+    /// @param client_id_1 Client id to be used to acquire the lease.
+    /// @param hw_address_2 HW Address to be used to release the lease.
+    /// @param client_id_2 Client id to be used to release the lease.
+    void unsuccessfulRelease(const std::string& hw_address_1,
+                             const std::string& client_id_1,
+                             const std::string& hw_address_2,
+                             const std::string& client_id_2);
+
+    /// @brief Interface Manager's fake configuration control.
+    IfaceMgrTestConfig iface_mgr_test_config_;
+
+};
+
+void
+ReleaseTest::acquireLease(Dhcp4Client& client) {
+    // Perform 4-way exchange with the server but to not request any
+    // specific address in the DHCPDISCOVER message.
+    ASSERT_NO_THROW(client.doDORA());
+    // Make sure that the server responded.
+    ASSERT_TRUE(client.getContext().response_);
+    Pkt4Ptr resp = client.getContext().response_;
+    // Make sure that the server has responded with DHCPACK.
+    ASSERT_EQ(DHCPACK, static_cast<int>(resp->getType()));
+    // Response must not be relayed.
+    EXPECT_FALSE(resp->isRelayed());
+    // Make sure that the server id is present.
+    EXPECT_EQ("10.0.0.1", client.config_.serverid_.toText());
+    // Make sure that the client has got the lease with the requested address.
+    ASSERT_NE(client.config_.lease_.addr_.toText(), "0.0.0.0");
+    Lease4Ptr lease = LeaseMgrFactory::instance().getLease4(client.config_.lease_.addr_);
+    ASSERT_TRUE(lease);
+}
+
+void
+ReleaseTest::successfulRelease(const std::string& hw_address_1,
+                               const std::string& client_id_1,
+                               const std::string& hw_address_2,
+                               const std::string& client_id_2) {
+    Dhcp4Client client(Dhcp4Client::SELECTING);
+    // Configure DHCP server.
+    configure(RELEASE_CONFIGS[0], *client.getServer());
+    // Explicitly set the client id.
+    client.includeClientId(client_id_1);
+    // Explicitly set the HW address.
+    client.setHWAddress(hw_address_1);
+    // Perform 4-way exchange to obtain a new lease.
+    acquireLease(client);
+
+    // Remember the acquired address.
+    IOAddress leased_address = client.config_.lease_.addr_;
+
+    // Explicitly set the client id for DHCPRELEASE.
+    client.includeClientId(client_id_2);
+    // Explicitly set the HW address for DHCPRELEASE.
+    client.setHWAddress(hw_address_2);
+
+    // Send the release and make sure that the lease is removed from the
+    // server.
+    ASSERT_NO_THROW(client.doRelease());
+    Lease4Ptr lease = LeaseMgrFactory::instance().getLease4(leased_address);
+    ASSERT_FALSE(lease);
+}
+
+void
+ReleaseTest::unsuccessfulRelease(const std::string& hw_address_1,
+                                 const std::string& client_id_1,
+                                 const std::string& hw_address_2,
+                                 const std::string& client_id_2) {
+    Dhcp4Client client(Dhcp4Client::SELECTING);
+    // Configure DHCP server.
+    configure(RELEASE_CONFIGS[0], *client.getServer());
+    // Explicitly set the client id.
+    client.includeClientId(client_id_1);
+    // Explicitly set the HW address.
+    client.setHWAddress(hw_address_1);
+    // Perform 4-way exchange to obtain a new lease.
+    acquireLease(client);
+
+    // Remember the acquired address.
+    IOAddress leased_address = client.config_.lease_.addr_;
+
+    // Explicitly set the client id for DHCPRELEASE.
+    client.includeClientId(client_id_2);
+    // Explicitly set the HW address for DHCPRELEASE.
+    client.setHWAddress(hw_address_2);
+
+    // Send DHCPRELEASE and make sure it was unsuccessful, i.e. the lease
+    // remains in the database.
+    ASSERT_NO_THROW(client.doRelease());
+    Lease4Ptr lease = LeaseMgrFactory::instance().getLease4(leased_address);
+    ASSERT_TRUE(lease);
+}
+
+
+// This test checks that the client can acquire and release the lease.
+TEST_F(ReleaseTest, releaseNoIdentifierChange) {
+    successfulRelease("01:02:03:04:05:06", "12:14",
+                      "01:02:03:04:05:06", "12:14");
+}
+
+// This test verifies the release correctness in the following case:
+// - Client acquires new lease using HW address only
+// - Client sends the DHCPRELEASE with valid HW address and without
+//   client identifier.
+// - The server successfully releases the lease.
+TEST_F(ReleaseTest, releaseHWAddressOnly) {
+    successfulRelease("01:02:03:04:05:06", "",
+                      "01:02:03:04:05:06", "");
+}
+
+// This test verifies the release correctness in the following case:
+// - Client acquires new lease using the client identifier and HW address
+// - Client sends the DHCPRELEASE with valid HW address but with no
+//   client identifier.
+// - The server successfully releases the lease.
+TEST_F(ReleaseTest, releaseNoClientId) {
+    successfulRelease("01:02:03:04:05:06", "12:14",
+                      "01:02:03:04:05:06", "");
+}
+
+// This test verifies the release correctness in the following case:
+// - Client acquires new lease using HW address
+// - Client sends the DHCPRELEASE with valid HW address and some
+//   client identifier.
+// - The server identifies the lease using HW address and releases
+//   this lease.
+TEST_F(ReleaseTest, releaseNoClientId2) {
+    successfulRelease("01:02:03:04:05:06", "",
+                      "01:02:03:04:05:06", "12:14");
+}
+
+// This test checks the server's behavior in the following case:
+// - Client acquires new lease using the client identifier and HW address
+// - Client sends the DHCPRELEASE with the valid HW address but with invalid
+//   client identifier.
+// - The server should not remove the lease.
+TEST_F(ReleaseTest, releaseNonMatchingClientId) {
+    unsuccessfulRelease("01:02:03:04:05:06", "12:14",
+                        "01:02:03:04:05:06", "12:15:16");
+}
+
+// This test checks the server's behavior in the following case:
+// - Client acquires new lease using client identifier and HW address
+// - Client sends the DHCPRELEASE with the same client identifier but
+//   different HW address.
+// - The server uses client identifier to find the client's lease and
+//   releases it.
+TEST_F(ReleaseTest, releaseNonMatchingHWAddress) {
+    successfulRelease("01:02:03:04:05:06", "12:14",
+                      "06:06:06:06:06:06", "12:14");
+}
+
+// This test checks the server's behavior in the following case:
+// - Client acquires new lease.
+// - Client sends DHCPRELEASE with the ciaddr set to a different
+//   address than it has acquired from the server.
+// - Server determines that the client is trying to release a
+//   wrong address and will refuse to release.
+TEST_F(ReleaseTest, releaseNonMatchingIPAddress) {
+    Dhcp4Client client(Dhcp4Client::SELECTING);
+    // Configure DHCP server.
+    configure(RELEASE_CONFIGS[0], *client.getServer());
+    // Perform 4-way exchange to obtain a new lease.
+    acquireLease(client);
+
+    // Remember the acquired address.
+    IOAddress leased_address = client.config_.lease_.addr_;
+
+    // Modify the client's address to force it to release a different address
+    // than it has obtained from the server.
+    client.config_.lease_.addr_ = IOAddress(static_cast<uint32_t>(leased_address) + 1);
+
+    // Send DHCPRELEASE and make sure it was unsuccessful, i.e. the lease
+    // remains in the database.
+    ASSERT_NO_THROW(client.doRelease());
+    Lease4Ptr lease = LeaseMgrFactory::instance().getLease4(leased_address);
+    ASSERT_TRUE(lease);
+}
+
+} // end of anonymous namespace