src/lib/dhcp/pkt.cc
    Pkt::getMAC(uint32_t hw_addr_src)
        sets HwAddr.source_ to HWADDR_SOURCE_RAW if appropriate

    Pkt::getMACFromIPv6(const isc::asiolink::IOAddress& addr)
        sets HwAddr.source_ to HWADDR_SOURCE_IPV6_LINK_LOCAL

src/lib/dhcp/pkt6.cc
    Pkt6::getMACFromDUID()
        sets HwAddr.source_ to HWADDR_SOURCE_DUID

    Pkt6::getMACFromIPv6RelayOpt()
        sets HwAddr.source_ to HWADDR_SOURCE_CLIENT_ADDR_RELAY_OPTION;

    Pkt6::getMACFromDocsisModem()         sets HwAddr.source_ to HWADDR_SOURCE_DOCSIS_MODEM;

    Pkt6::getMACFromDocsisCMTS()
        sets HwAddr.source_ to HWADDR_SOURCE_DOCSIS_CMTS;

    Pkt6::getMACFromRemoteIdRelayOption()
        sets HwAddr.source_ to HWADDR_SOURCE_REMOTE_ID;

src/lib/dhcp/tests/pkt6_unittest.cc
    Added checks for correct HWAddr::source_ values to the following tests:
    TEST_F(Pkt6Test, getMAC)
    TEST_F(Pkt6Test, getMAC)
    TEST_F(Pkt6Test, getMACFromIPv6LinkLocal_direct)
    TEST_F(Pkt6Test, getMACFromIPv6LinkLocal_singleRelay)
    TEST_F(Pkt6Test, getMACFromIPv6LinkLocal_multiRelay)
    TEST_F(Pkt6Test, getMACFromIPv6RelayOpt_singleRelay)
    TEST_F(Pkt6Test, getMACFromIPv6RelayOpt_multipleRelay)
    TEST_F(Pkt6Test, getMACFromDUID)
    TEST_F(Pkt6Test, getMACFromDUID)
    TEST_F(Pkt6Test, getMAC_DOCSIS_Modem)
    TEST_F(Pkt6Test, getMAC_DOCSIS_CMTS)
    TEST_F(Pkt6Test, getMACFromRemoteIdRelayOption)