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@@ -1,32 +1,117 @@
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/**
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- * @page dhcpv4 DHCPv4 Component
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+ * @page dhcpv4 DHCPv4 Server Component
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*
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- * BIND10 offers DHCPv4 server implementation. It is implemented as b10-dhcp4 component.
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- * It's primary code is located in isc::dhcp::Dhcpv4Srv class. It uses \ref libdhcp extensively,
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- * especially isc::dhcp::Pkt4, isc::dhcp::Option and isc::dhcp::IfaceMgr classes.
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+ * BIND10 offers DHCPv4 server implementation. It is implemented as
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+ * b10-dhcp4 component. Its primary code is located in
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+ * isc::dhcp::Dhcpv4Srv class. It uses \ref libdhcp extensively,
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+ * especially isc::dhcp::Pkt4, isc::dhcp::Option and
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+ * isc::dhcp::IfaceMgr classes. Currently this code offers skeleton
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+ * functionality, i.e. it is able to receive and process incoming
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+ * requests and trasmit responses. However, it does not have database
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+ * management, so it returns only one, hardcoded lease to whoever asks
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+ * for it.
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*
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- * @todo Describe DHCPv4 component properly.
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- *
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- * @page dhcpv6 DHCPv6 Component
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+ * DHCPv4 server component does not support direct traffic (relayed
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+ * only), as support for transmission to hosts without IPv4 address
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+ * assigned is not implemented in IfaceMgr yet.
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+ *
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+ * DHCPv4 server component does not listen to BIND10 message queue.
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+ *
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+ * DHCPv4 server component does not use BIND10 logging yet.
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+ *
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+ * DHCPv4 server component is not integrated with boss yet.
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+ *
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+ * @page dhcpv6 DHCPv6 Server Component
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+ *
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+ * BIND10 offers DHCPv6 server implementation. It is implemented as
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+ * b10-dhcp6 component. Its primary code is located in
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+ * isc::dhcp::Dhcpv6Srv class. It uses \ref libdhcp extensively,
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+ * especially lib::dhcp::Pkt6, isc::dhcp::Option and
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+ * isc::dhcp::IfaceMgr classes. Currently this code offers skeleton
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+ * functionality, i.e. it is able to receive and process incoming
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+ * requests and trasmit responses. However, it does not have database
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+ * management, so it returns only one, hardcoded lease to whoever asks
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+ * for it.
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+ *
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+ * DHCPv6 server component does not support relayed traffic yet, as
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+ * support for relay decapsulation is not implemented yet.
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+ *
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+ * DHCPv6 server component does not listen to BIND10 message queue.
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+ *
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+ * DHCPv6 server component does not use BIND10 logging yet.
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+ *
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+ * DHCPv6 server component is not integrated with boss yet.
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*
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- * @todo DHCPv6 component will be described here.
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- *
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* @page libdhcp libdhcp++ library
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*
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* @section libdhcpIntro Libdhcp++ Introduction
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*
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- * libdhcp++ is an all-purpose DHCP-manipulation library, written in C++. It offers packet
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- * parsing and assembly, DHCPv4 and DHCPv6 options parsing and assembly, interface detection
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- * (currently on Linux systems only) and socket operations. Following classes are implemented:
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+ * libdhcp++ is an all-purpose DHCP-manipulation library, written in
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+ * C++. It offers packet parsing and assembly, DHCPv4 and DHCPv6
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+ * options parsing and ssembly, interface detection (currently on
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+ * Linux systems only) and socket operations. Following classes are
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+ * implemented:
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*
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* - isc::dhcp::Pkt4 - represents DHCPv4 packet.
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* - isc::dhcp::Pkt6 - represents DHCPv6 packet.
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*
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+ * There are two pointer types defined: Pkt4Ptr and Pkt6Ptr. They are
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+ * smart pointer and are using boost::shared_ptr. There are not const
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+ * versions defined, as we assume that hooks can modify any aspect of
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+ * the packet at almost any stage of processing.
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+ *
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+ * Both packets use collection of Option objects to represent DHCPv4
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+ * and DHCPv6 options. The base class -- Option -- can be used to
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+ * represent generic option that contains collection of
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+ * bytes. Depending on if the option is instantiated as v4 or v6
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+ * option, it will adjust its header (DHCPv4 options use 1 octet for
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+ * type and 1 octet for length, while DHCPv6 options use 2 bytes for
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+ * each).
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+ *
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+ * There are many specialized classes that are intended to handle options with
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+ * specific content:
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+ * - isc::dhcp::Option4AddrLst -- DHCPv4 option, contains one or more IPv4 addresses;
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+ * - isc::dhcp::Option6AddrLst -- DHCPv6 option, contains one or more IPv6 addresses;
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+ * - isc::dhcp::Option6IAAddr -- DHCPv6 option, represents IAADDR_OPTION (an option that
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+ * contains IPv6 address with extra parameters);
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+ * - isc::dhcp::Option6IA -- DHCPv6 option used to store IA_NA and its suboptions.
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+ *
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+ * All options can store sub-options (i.e. options that are stored within option
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+ * rather than in a message directly). This functionality is commonly used in
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+ * DHCPv6, but is rarely used in DHCPv4. isc::dhcp::Option::addOption(),
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+ * isc::dhcp::Option::delOption(), isc::dhcp::Option::getOption() can be used
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+ * for that purpose.
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+ *
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* @section lidhcpIfaceMgr Interface Manager
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*
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- * Interface Manager (or IfaceMgr) is an abstraction layer about low-level network operations.
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- * In particlar, it provides information about existing network interfaces See isc::dhcp::IfaceMgr::Iface
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- * class and isc::dhcp::IfaceMgr::detectIfaces() and isc::dhcp::IfaceMgr::getIface().
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- * Another useful methods are dedicated to transmission (isc::dhcp::IfaceMgr::send(), 2 overloads)
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- * and reception (isc::dhcp::IfaceMgr::receive4() and isc::dhcp::IfaceMgr::receive6()).
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+ * Interface Manager (or IfaceMgr) is an abstraction layer about low-level
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+ * network operations. In particlar, it provides information about existing
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+ * network interfaces See isc::dhcp::IfaceMgr::Iface class and
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+ * isc::dhcp::IfaceMgr::detectIfaces() and isc::dhcp::IfaceMgr::getIface().
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+ *
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+ * Currently there is interface detection is implemented in Linux only. There
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+ * are plans to implement such support for other OSes, but they remain low
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+ * priority for now.
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+ *
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+ * Generic parts of the code are isc::dhcp::IfaceMgr class in
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+ * src/lib/dhcp/iface_mgr.cc file. OS-specific code is located in separate
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+ * files, e.g. iface_mgr_linux.cc. Such separation should be maintained when
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+ * additional code will be developed.
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+ *
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+ * For systems that interface detection is not supported on, there is a stub
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+ * mechanism implemented. It assumes that interface name is read from a text
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+ * file. This is a temporary solution and will be removed as soon as proper
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+ * interface detection is implemented. It is not going to be developed further.
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+ * To use this feature, store interfaces.txt file. It uses a simple syntax.
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+ * Each line represents an interface name, followed by IPv4 or IPv6 address
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+ * that follows it. This is usually link-local IPv6 address that the server
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+ * should bind to. In theory this mechanism also supports IPv4, but it was
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+ * never tested. The code currently supports only a single interface defined
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+ * that way.
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+ *
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+ * Another useful methods are dedicated to transmission
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+ * (isc::dhcp::IfaceMgr::send(), 2 overloads) and reception
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+ * (isc::dhcp::IfaceMgr::receive4() and isc::dhcp::IfaceMgr::receive6()).
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+ * Note that receive4() and receive6() methods may return NULL, e.g.
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+ * when timeout is reached or if dhcp daemon receives a signal.
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*/
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Tomek Mrugalski
