[master] Merge branch 'trac3554' (mac-sources parameter added)

doc/Makefile.am

@@ -9,6 +9,7 @@ nobase_dist_doc_DATA += examples/kea4/reservations.json
 nobase_dist_doc_DATA += examples/kea6/simple.json
 nobase_dist_doc_DATA += examples/kea6/several-subnets.json
 nobase_dist_doc_DATA += examples/kea6/multiple-options.json
+nobase_dist_doc_DATA += examples/kea6/advanced.json
 nobase_dist_doc_DATA += examples/ddns/sample1.json
 nobase_dist_doc_DATA += examples/ddns/template.json
 

doc/examples/kea4/multiple-options.json

@@ -4,8 +4,8 @@
 { "Dhcp4":
 
 {
-# Kea is told to listen on eth0 interface only.
-  "interfaces": [ "eth0" ],
+# Kea is told to listen on ethX interface only.
+  "interfaces": [ "ethX" ],
 
 # We need to specify lease type. As of May 2014, three backends are supported:
 # memfile, mysql and pgsql. We'll just use memfile, because it doesn't require
@@ -36,7 +36,7 @@
     {
        "pools": [ { "pool":  "192.0.2.10 - 192.0.2.200" } ],
        "subnet": "192.0.2.0/24",
-       "interface": "eth0",
+       "interface": "ethX",
        "option-data": [
          {
              "name": "domain-name-servers",

doc/examples/kea4/several-subnets.json

@@ -5,8 +5,8 @@
 { "Dhcp4":
 
 {
-# Kea is told to listen on eth0 interface only.
-  "interfaces": [ "eth0" ],
+# Kea is told to listen on ethX interface only.
+  "interfaces": [ "ethX" ],
 
 # We need to specify lease type. As of May 2014, three backends are supported:
 # memfile, mysql and pgsql. We'll just use memfile, because it doesn't require

doc/examples/kea4/single-subnet.json

@@ -5,8 +5,8 @@
 { "Dhcp4":
 
 {
-# Kea is told to listen on eth0 interface only.
-  "interfaces": [ "eth0" ],
+# Kea is told to listen on ethX interface only.
+  "interfaces": [ "ethX" ],
 
 # We need to specify lease type. As of May 2014, three backends are supported:
 # memfile, mysql and pgsql. We'll just use memfile, because it doesn't require
@@ -35,8 +35,8 @@
     {
        "pools": [ { "pool":  "192.0.2.1 - 192.0.2.200" } ],
        "subnet": "192.0.2.0/24",
-       "interface": "eth0"
-    } 
+       "interface": "ethX"
+    }
   ]
 },
 

doc/examples/kea6/advanced.json

+# This is an example configuration file for DHCPv6 server in Kea.
+# It attempts to showcase some of the more advanced features.
+# Topology wise, it's a basic scenario with one IPv6 subnet configured.
+# It is assumed that one subnet (2001:db8:1::/64) is available directly
+# over ethX interface.
+#
+# The following features are currently showcased here:
+# 1. Configuration of MAC/hardware address sources in DHCPv6
+
+{ "Dhcp6":
+
+{
+# Kea is told to listen on ethX network interface only.
+  "interfaces": [ "ethX" ],
+
+# We need to specify lease type. As of May 2014, three backends are supported:
+# memfile, mysql and pgsql. We'll just use memfile, because it doesn't require
+# any prior set up.
+  "lease-database": {
+    "type": "memfile"
+  },
+
+# Kea 0.9.1 introduced MAC/hardware addresses support in DHCPv6. There is
+# no single reliable method of getting MAC address information in DHCPv6.
+# Kea supports several methods. Depending on your network set up, some
+# methods may be more preferable than others, hence the configuration
+# parameter. 'mac-sources' is a list of methods. Allowed parameters are:
+# any, raw, duid, ipv6-link-local, client-link-addr-option, rfc6939 (which
+# is an alias for client-link-addr-option), remote-id, rfc4649 (which is an
+# alias for remote-id, subscriber-id, rfc4580 (which is an alias for
+# subscriber-id) and docsis.
+#
+# Note that the order matters. Methods are attempted one by one in the order
+# specified until hardware address is obtained. If you don't care which method
+# is used, using 'any' is marginally faster than enumerating them all.
+#
+# If mac-sources are not specified, a default value of 'any' is used.
+  "mac-sources": [ "client-link-addr-option", "duid", "ipv6-link-local" ],
+
+# Addresses will be assigned with preferred and valid lifetimes
+# being 3000 and 4000, respectively. Client is told to start
+# renewing after 1000 seconds. If the server does not repond
+# after 2000 seconds since the lease was granted, client is supposed
+# to start REBIND procedure (emergency renewal that allows switching
+# to a different server).
+  "preferred-lifetime": 3000,
+  "valid-lifetime": 4000,
+  "renew-timer": 1000,
+  "rebind-timer": 2000,
+
+# The following list defines subnets. Each subnet consists of at
+# least subnet and pool entries.
+  "subnet6": [
+    {
+      "pools": [ { "pool": "2001:db8:1::/80" } ],
+      "subnet": "2001:db8:1::/64",
+      "interface": "ethX"
+    }
+  ]
+},
+
+# The following configures logging. Kea will log all debug messages
+# to /var/log/kea-debug.log file.
+"Logging": {
+    "loggers": [
+        {
+            "name": "kea-dhcp6",
+            "output_options": [
+                {
+                    "output": "/var/log/kea-debug.log"
+                }
+            ],
+            "debuglevel": 99,
+            "severity": "DEBUG"
+        }
+    ]
+}
+
+}

doc/examples/kea6/multiple-options.json

@@ -4,8 +4,8 @@
 { "Dhcp6":
 
 {
-# Kea is told to listen on eth0 interface only.
-  "interfaces": [ "eth0" ],
+# Kea is told to listen on ethX interface only.
+  "interfaces": [ "ethX" ],
 
 # We need to specify lease type. As of May 2014, three backends are supported:
 # memfile, mysql and pgsql. We'll just use memfile, because it doesn't require
@@ -32,7 +32,7 @@
     {
       "pools": [ { "pool": "2001:db8:1::/80" } ],
       "subnet": "2001:db8:1::/64",
-      "interface": "eth0",
+      "interface": "ethX",
       "option-data": [
         {
             "name": "dns-servers",

doc/examples/kea6/several-subnets.json

@@ -5,8 +5,8 @@
 { "Dhcp6":
 
 {
-# Kea is told to listen on eth0 interface only.
-  "interfaces": [ "eth0" ],
+# Kea is told to listen on ethX interface only.
+  "interfaces": [ "ethX" ],
 
 # We need to specify lease type. As of May 2014, three backends are supported:
 # memfile, mysql and pgsql. We'll just use memfile, because it doesn't require

doc/examples/kea6/simple.json

 # This is an example configuration file for DHCPv6 server in Kea.
-# It's a basic scenario with four IPv6 subnets configured. It is
+# It's a basic scenario with one IPv6 subnet configured. It is
 # assumed that one subnet (2001:db8:1::/64 is available directly
-# over eth0 interface.
+# over ethX interface.
 
 { "Dhcp6":
 
 { 
-# Kea is told to listen on eth0 interface only.
-  "interfaces": [ "eth0" ],
+# Kea is told to listen on ethX interface only.
+  "interfaces": [ "ethX" ],
 
 # We need to specify lease type. As of May 2014, three backends are supported:
 # memfile, mysql and pgsql. We'll just use memfile, because it doesn't require
@@ -33,7 +33,7 @@
     {
       "pools": [ { "pool": "2001:db8:1::/80" } ],
       "subnet": "2001:db8:1::/64",
-      "interface": "eth0"
+      "interface": "ethX"
     }
   ]
 },

doc/guide/dhcp6-srv.xml

@@ -1838,6 +1838,117 @@ should include options from the isc option space:
       </para>
       </section>
 
+    <section id="mac-in-dhcpv6">
+      <title>MAC/Hardware addresses in DHCPv6</title>
+      <para>MAC/hardware addesses are available in DHCPv4 messages
+      from the clients and administrators
+      frequently use that information to perform certain tasks, like per host
+      configuration, address reserveration for specific MAC addresses and other.
+      Unfortunately, DHCPv6 protocol does not provide any completely reliable way
+      to retrieve that information. To mitigate that issue a number of mechanisms
+      have been implemented in Kea that attempt to gather that information. Each
+      of those mechanisms works in certain cases, but may fail in other cases.
+      Whether the mechanism works or not in the particular deployment is
+      somewhat dependent on the network topology and the technologies used.</para>
+
+      <para>Kea allows for configuration which of the supported methods should be
+      used and in which order. This configuration may be considered a fine tuning
+      of the DHCP deployment. In a typical deployment the default
+      value of <command>"any"</command> is sufficient and there is no
+      need to select specific methods. Changing the value of this parameter
+      is the most useful in cases when an administrator wants to disable
+      certain method, e.g. if the administrator trusts the network infrastructure
+      more than the information provided by the clients themselves, the
+      administrator may prefer information provided by the relays over that
+      provided by the clients. The format of this parameter is as follows:
+        <screen>
+"Dhcp6": {
+    <userinput>"mac-sources": [ "method1", "method2", "method3", ... ]</userinput>,
+
+    "subnet6": [ ... ],
+
+    ...
+}
+</screen>
+
+    When not specified, a special value of <emphasis>any</emphasis> is used, which
+    instructs the server to attempt to use all the methods in sequence and use
+    value returned by the first one that succeeds.</para>
+
+    <para>Supported methods are:
+    <itemizedlist>
+      <listitem>
+        <simpara><command>any</command> - not an actual method, just a keyword that
+        instructs Kea to try all other methods and use the first one that succeeds.
+        This is the default operation if no <command>mac-sources</command> are defined.
+        </simpara>
+      </listitem>
+      <listitem>
+        <simpara><command>raw</command> In principle, a DHCPv6 server could use raw
+        sockets to receive incoming traffic and extract MAC/hardware address
+        information. This is currently not implemented and this value has no effect.
+        </simpara>
+      </listitem>
+      <listitem>
+        <simpara><command>duid</command> - DHCPv6 uses DUID identifiers instead of
+        MAC addresses. There are currently four DUID types defined, with two of them
+        (DUID-LLT, which is the default one and DUID-LL) convey MAC address information.
+        Although RFC3315 forbids it, it is possible to parse those DUIDs and extract
+        necessary information from them. This method is not completely reliable, as
+        clients may use other DUID types, namely DUID-EN or DUID-UUID.
+        </simpara>
+      </listitem>
+      <listitem>
+        <simpara><command>ipv6-link-local</command> - Another possible aquisition
+        method comes from the source IPv6 address. In typical usage, clients are
+        sending their packets from IPv6 link-local addresses. There's a good chance
+        that those addresses are based on EUI-64, which contains MAC address. This
+        method is not completely reliable, as clients may use other link-local address
+        types. In particular, privacy extensions, defined in RFC4941, do not use
+        MAC addresses.
+        </simpara>
+      </listitem>
+      <listitem>
+        <simpara><command>client-link-addr-option</command> - One extension defined
+        to alleviate missing MAC issues is client link-layer address option, defined
+        in <ulink url="http://tools.ietf.org/html/rfc6939">RFC 6939</ulink>. This is
+        an option that is inserted by a relay and contains information about client's
+        MAC address. This method requires a relay agent that supports the option and
+        is configured to insert it. This method is useless for directly connected
+        clients. This parameter can also be specified as <command>rfc6939</command>,
+        which is an alias for <command>client-link-addr-option</command>.
+        </simpara>
+      </listitem>
+      <listitem>
+        <simpara><command>remote-id</command> <ulink
+        url="http://tools.ietf.org/html/rfc4649">RFC 4649</ulink>
+        defines remote-id option that is inserted by a relay agent. Depending
+        on the relay agent configuration, the inserted option may convey client's
+        MAC address information. This parameter can also be specified as
+        <command>rfc4649</command>, which is an alias for <command>remote-id</command>.
+        </simpara>
+      </listitem>
+      <listitem>
+        <simpara><command>subscriber-id</command> - Another option
+        that is somewhat similar to the previous one is subscriber-id,
+        defined in <ulink url="http://tools.ietf.org/html/rfc4580">RFC
+        4580</ulink>. It is, too, inserted by a relay agent that is
+        configured to insert it. This parameter can also be specified
+        as <command>rfc4580</command>, which is an alias for
+        <command>subscriber-id</command>. This method is currently not
+        implemented.
+        </simpara>
+      </listitem>
+      <listitem>
+        <simpara><command>docsis</command> - Yet another possible source of MAC
+        address information are DOCSIS options inserted by a CMTS that acts
+        as a DHCPv6 relay agent in cable networks. This method is
+        currently not implemented.
+        </simpara>
+      </listitem>
+    </itemizedlist>
+    </para>
+    </section>
 
     <section id="dhcp6-std">
       <title>Supported DHCPv6 Standards</title>

src/bin/dhcp6/dhcp6.spec

@@ -422,6 +422,21 @@
                 } ]
             }
       },
+
+      { "item_name": "mac-sources",
+        "item_type": "list",
+        "item_optional": true,
+        "item_default": [ "any" ],
+        "item_description": "Lists MAC/hardware address acquisition sources",
+        "list_item_spec":
+        {
+          "item_name": "source",
+          "item_type": "string",
+          "item_optional": true,
+          "item_default": "any"
+        }
+      } ,
+
       { "item_name": "dhcp-ddns",
         "item_type": "map",
         "item_optional": false,

src/bin/dhcp6/dhcp6_srv.cc

@@ -1184,6 +1184,21 @@ Dhcpv6Srv::createRemovalNameChangeRequest(const Lease6Ptr& lease) {
     CfgMgr::instance().getD2ClientMgr().sendRequest(ncr);
 }
 
+HWAddrPtr
+Dhcpv6Srv::getMAC(const Pkt6Ptr& pkt) {
+    CfgMACSources mac_sources = CfgMgr::instance().getCurrentCfg()->
+        getMACSources().get();
+    HWAddrPtr hwaddr;
+    for (CfgMACSources::const_iterator it = mac_sources.begin();
+         it != mac_sources.end(); ++it) {
+        hwaddr = pkt->getMAC(*it);
+        if (hwaddr) {
+            return (hwaddr);
+        }
+    }
+    return (hwaddr);
+}
+
 OptionPtr
 Dhcpv6Srv::assignIA_NA(const Subnet6Ptr& subnet, const DuidPtr& duid,
                        const Pkt6Ptr& query, const Pkt6Ptr& answer,
@@ -1253,10 +1268,9 @@ Dhcpv6Srv::assignIA_NA(const Subnet6Ptr& subnet, const DuidPtr& duid,
         hostname = fqdn->getDomainName();
     }
 
-    // Attempt to get MAC address using any of available mechanisms.
-    // It's ok if there response is NULL. Hardware address is optional in Lease6
-    /// @todo: Make this configurable after trac 3554 is done.
-    HWAddrPtr hwaddr = query->getMAC(Pkt::HWADDR_SOURCE_ANY);
+    // Attempt to get MAC address using configured mechanisms.
+    // It's ok if there response is NULL. Hardware address is optional in Lease6.
+    HWAddrPtr hwaddr = getMAC(query);
 
     // Use allocation engine to pick a lease for this client. Allocation engine
     // will try to honour the hint, but it is just a hint - some other address
@@ -1376,8 +1390,7 @@ Dhcpv6Srv::assignIA_PD(const Subnet6Ptr& subnet, const DuidPtr& duid,
 
     // Attempt to get MAC address using any of available mechanisms.
     // It's ok if there response is NULL. Hardware address is optional in Lease6
-    /// @todo: Make this configurable after trac 3554 is done.
-    HWAddrPtr hwaddr = query->getMAC(Pkt::HWADDR_SOURCE_ANY);
+    HWAddrPtr hwaddr = getMAC(query);
 
     LOG_DEBUG(dhcp6_logger, DBG_DHCP6_DETAIL, DHCP6_PROCESS_IA_PD_REQUEST)
         .arg(duid ? duid->toText() : "(no-duid)").arg(ia->getIAID())
@@ -1569,6 +1582,9 @@ Dhcpv6Srv::extendIA_NA(const Subnet6Ptr& subnet, const DuidPtr& duid,
         lease->fqdn_fwd_ = do_fwd;
         lease->fqdn_rev_ = do_rev;
 
+        /// @todo: check if hardware address has changed since last update.
+        /// And modify lease->hwaddr_ if it did.
+
         ia_rsp->setT1(subnet->getT1());
         ia_rsp->setT2(subnet->getT2());
 

src/bin/dhcp6/dhcp6_srv.h

@@ -596,6 +596,14 @@ protected:
     /// @param pkt packet to be classified
     void classifyPacket(const Pkt6Ptr& pkt);
 
+    /// @brief Attempts to get a MAC/hardware address using configred sources
+    ///
+    /// Tries to extract MAC/hardware address information from the packet
+    /// using MAC sources configured in 'mac-sources' configuration parameter.
+    ///
+    /// @param pkt will try to exact MAC address from this packet
+    /// @return HWaddr pointer (or NULL if configured methods fail)
+    static HWAddrPtr getMAC(const Pkt6Ptr& pkt);
 
     /// @brief this is a prefix added to the contend of vendor-class option
     ///

src/bin/dhcp6/json_config_parser.cc

@@ -613,6 +613,9 @@ namespace dhcp {
         parser = new HooksLibrariesParser(config_id);
     } else if (config_id.compare("dhcp-ddns") == 0) {
         parser = new D2ClientConfigParser(config_id);
+    } else if (config_id.compare("mac-sources") == 0) {
+        parser = new MACSourcesListConfigParser(config_id,
+                                                globalContext());
     } else {
         isc_throw(DhcpConfigError,
                 "unsupported global configuration parameter: "

src/bin/dhcp6/json_config_parser.h

@@ -15,9 +15,6 @@
 #ifndef DHCP6_CONFIG_PARSER_H
 #define DHCP6_CONFIG_PARSER_H
 
-/// @todo: This header file and its .cc counterpart are very similar between
-/// DHCPv4 and DHCPv6. They should be merged. See ticket #2355.
-
 #include <cc/data.h>
 #include <dhcpsrv/parsers/dhcp_parsers.h>
 #include <exceptions/exceptions.h>

src/bin/dhcp6/tests/config_parser_unittest.cc

@@ -3627,4 +3627,79 @@ TEST_F(Dhcp6ParserTest, reservationBogus) {
 
 }
 
+/// The goal of this test is to verify that configuration can include
+/// MAC/Hardware sources. This test also checks if the aliases are
+/// handled properly (rfc6939 = client-addr-relay, rfc4649 = remote-id,
+/// rfc4580 = subscriber-id).
+TEST_F(Dhcp6ParserTest, macSources) {
+
+    ConstElementPtr status;
+
+    EXPECT_NO_THROW(status = configureDhcp6Server(srv_,
+        Element::fromJSON("{ \"interfaces\": [ \"*\" ],"
+                          "\"mac-sources\": [ \"rfc6939\", \"rfc4649\", \"rfc4580\","
+                          "\"client-link-addr-option\", \"remote-id\", \"subscriber-id\"],"
+                          "\"preferred-lifetime\": 3000,"
+                          "\"rebind-timer\": 2000, "
+                          "\"renew-timer\": 1000, "
+                          "\"subnet6\": [  ], "
+                          "\"valid-lifetime\": 4000 }")));
+
+    // returned value should be 0 (success)
+    checkResult(status, 0);
+
+    CfgMACSources mac_sources = CfgMgr::instance().getStagingCfg()->getMACSources().get();
+    ASSERT_EQ(6, mac_sources.size());
+    // Let's check the aliases. They should be recognized to their base methods.
+    EXPECT_EQ(HWAddr::HWADDR_SOURCE_CLIENT_ADDR_RELAY_OPTION, mac_sources[0]);
+    EXPECT_EQ(HWAddr::HWADDR_SOURCE_REMOTE_ID, mac_sources[1]);
+    EXPECT_EQ(HWAddr::HWADDR_SOURCE_SUBSCRIBER_ID, mac_sources[2]);
+
+    // Let's check if the actual methods are recognized properly.
+    EXPECT_EQ(HWAddr::HWADDR_SOURCE_CLIENT_ADDR_RELAY_OPTION, mac_sources[3]);
+    EXPECT_EQ(HWAddr::HWADDR_SOURCE_REMOTE_ID, mac_sources[4]);
+    EXPECT_EQ(HWAddr::HWADDR_SOURCE_SUBSCRIBER_ID, mac_sources[5]);
+}
+
+/// The goal of this test is to verify that MAC sources configuration can be
+/// empty.
+TEST_F(Dhcp6ParserTest, macSourcesEmpty) {
+
+    ConstElementPtr status;
+
+    EXPECT_NO_THROW(status = configureDhcp6Server(srv_,
+                    Element::fromJSON("{ \"interfaces\": [ \"*\" ],"
+                                      "\"mac-sources\": [ ],"
+                                      "\"preferred-lifetime\": 3000,"
+                                      "\"rebind-timer\": 2000, "
+                                      "\"renew-timer\": 1000, "
+                                      "\"subnet6\": [  ], "
+                                      "\"valid-lifetime\": 4000 }")));
+
+    // returned value should be 0 (success)
+    checkResult(status, 0);
+
+    CfgMACSources mac_sources = CfgMgr::instance().getStagingCfg()->getMACSources().get();
+    EXPECT_EQ(0, mac_sources.size());
+}
+
+/// The goal of this test is to verify that MAC sources configuration can
+/// only use valid parameters.
+TEST_F(Dhcp6ParserTest, macSourcesBogus) {
+
+    ConstElementPtr status;
+
+    EXPECT_NO_THROW(status = configureDhcp6Server(srv_,
+                    Element::fromJSON("{ \"interfaces\": [ \"*\" ],"
+                                      "\"mac-sources\": [ \"from-wire\" ],"
+                                      "\"preferred-lifetime\": 3000,"
+                                      "\"rebind-timer\": 2000, "
+                                      "\"renew-timer\": 1000, "
+                                      "\"subnet6\": [  ], "
+                                      "\"valid-lifetime\": 4000 }")));
+
+    // returned value should be 1 (failure)
+    checkResult(status, 1);
+}
+
 };

src/bin/dhcp6/tests/dhcp6_client.cc

@@ -63,7 +63,7 @@ Dhcp6Client::applyRcvdConfiguration(const Pkt6Ptr& reply) {
     Opts opts = reply->options_;
 
     // Let's try to get a MAC
-    HWAddrPtr hwaddr = reply->getMAC(Pkt::HWADDR_SOURCE_ANY);
+    HWAddrPtr hwaddr = reply->getMAC(HWAddr::HWADDR_SOURCE_ANY);
 
     // Set the global status code to default: success and not received.
     config_.resetGlobalStatusCode();

src/lib/dhcp/hwaddr.cc

@@ -27,6 +27,16 @@
 namespace isc {
 namespace dhcp {
 
+const uint32_t HWAddr::HWADDR_SOURCE_ANY = 0xffffffff;
+const uint32_t HWAddr::HWADDR_SOURCE_UNKNOWN = 0x00000000;
+const uint32_t HWAddr::HWADDR_SOURCE_RAW = 0x00000001;
+const uint32_t HWAddr::HWADDR_SOURCE_DUID = 0x00000002;
+const uint32_t HWAddr::HWADDR_SOURCE_IPV6_LINK_LOCAL = 0x00000004;
+const uint32_t HWAddr::HWADDR_SOURCE_CLIENT_ADDR_RELAY_OPTION = 0x00000008;
+const uint32_t HWAddr::HWADDR_SOURCE_REMOTE_ID = 0x00000010;
+const uint32_t HWAddr::HWADDR_SOURCE_SUBSCRIBER_ID = 0x00000020;
+const uint32_t HWAddr::HWADDR_SOURCE_DOCSIS = 0x00000040;
+
 HWAddr::HWAddr()
     :htype_(HTYPE_ETHER), source_(0) {
 }

src/lib/dhcp/hwaddr.h

@@ -34,6 +34,53 @@ public:
     /// @brief Maximum size of a hardware address.
     static const size_t MAX_HWADDR_LEN = 20;
 
+    /// @defgroup hw_sources Specifies where a given MAC/hardware address was
+    ///                      obtained.
+    ///
+    /// @brief The list covers all possible MAC/hw address sources.
+    ///
+    /// @{
+
+    /// Not really a type, only used in getMAC() calls.
+    static const uint32_t HWADDR_SOURCE_ANY;
+
+    /// Used when actual origin is not known, e.g. when reading from a
+    /// lease database that didn't store that information.
+    static const uint32_t HWADDR_SOURCE_UNKNOWN;
+
+    /// Obtained first hand from raw socket (100% reliable).
+    static const uint32_t HWADDR_SOURCE_RAW;
+
+    /// Extracted from DUID-LL or DUID-LLT (not 100% reliable as the client
+    /// can send fake DUID).
+    static const uint32_t HWADDR_SOURCE_DUID;
+
+    /// Extracted from IPv6 link-local address. Not 100% reliable, as the
+    /// client can use different IID other than EUI-64, e.g. Windows supports
+    /// RFC4941 and uses random values instead of EUI-64.
+    static const uint32_t HWADDR_SOURCE_IPV6_LINK_LOCAL;
+
+    /// Get it from RFC6939 option. (A relay agent can insert client link layer
+    /// address option). Note that a skilled attacker can fake that by sending
+    /// his request relayed, so the legitimate relay will think it's a second
+    /// relay.
+    static const uint32_t HWADDR_SOURCE_CLIENT_ADDR_RELAY_OPTION;
+
+    /// A relay can insert remote-id. In some deployments it contains a MAC
+    /// address (RFC4649).
+    static const uint32_t HWADDR_SOURCE_REMOTE_ID;
+
+    /// A relay can insert a subscriber-id option. In some deployments it
+    /// contains a MAC address (RFC4580).
+    static const uint32_t HWADDR_SOURCE_SUBSCRIBER_ID;
+
+    /// A CMTS (acting as DHCP relay agent) that supports DOCSIS standard
+    /// can insert DOCSIS options that contain client's MAC address.