packet_assembly.hh

RIP 协议实现

// -*- c-basic-offset: 4; tab-width: 8; indent-tabs-mode: t -*-

// Copyright (c) 2001-2008 XORP, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software")
// to deal in the Software without restriction, subject to the conditions
// listed in the XORP LICENSE file. These conditions include: you must
// preserve this copyright notice, and you cannot mention the copyright
// holders in advertising related to the Software without their permission.
// The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
// notice is a summary of the XORP LICENSE file; the license in that file is
// legally binding.

// $XORP: xorp/rip/packet_assembly.hh,v 1.15 2008/07/23 05:11:35 pavlin Exp $

#ifndef __RIP_PACKET_ASSEMBLY_HH__
#define __RIP_PACKET_ASSEMBLY_HH__

#include "rip_module.h"
#include "libxorp/xlog.h"

#include "auth.hh"
#include "packets.hh"
#include "port.hh"

/**
 * @short Internal specialized state for PacketAssembler classes.
 *
 * Completely specialized implementations exist for IPv4 and IPv6 template
 * arguments.
 */
template <typename A>
class PacketAssemblerSpecState
{};

/**
 * @short IPv4 specialized PacketAssembler state.
 *
 * This class just holder the authentication handler that IPv4 packet
 * assembly requires.
 */
template <>
class PacketAssemblerSpecState<IPv4>
{
private:
    AuthHandlerBase& _ah;
public:
    /**
     * IPv4 Specific Constructor.
     */
    PacketAssemblerSpecState(Port<IPv4>& port)
	: _ah(*(port.af_state().auth_handler()))
    {}

    /**
     * IPv4 Specific Constructor.
     */
    PacketAssemblerSpecState(AuthHandlerBase& auth_handler)
	: _ah(auth_handler)
    {}

    /**
     * IPv4 Specific authentication handler accessor.
     */
    AuthHandlerBase&	  ah()			{ return _ah; }

    /**
     * IPv4 Specific authentication handler accessor.
     */
    const AuthHandlerBase& ah() const		{ return _ah; }
};


/**
 * @short IPv6 specialized PacketAssembler state.
 *
 * This provides a means to query the RIP port and query the
 * configured maximum entries per packet. XXX At present it's a
 * placeholder and returns a fixed value.
 *
 * It also stores the last used nexthop value since nexthops are only
 * packed when they change.
 */
template <>
class PacketAssemblerSpecState<IPv6>
{
private:
    uint32_t _max_entries;
    IPv6     _lnh;

public:
    PacketAssemblerSpecState(Port<IPv6>& )
	: _max_entries(25), _lnh(IPv6::ALL_ONES())
    {}
    PacketAssemblerSpecState()
	: _max_entries(25), _lnh(IPv6::ALL_ONES())
    {}

    uint32_t	max_entries() const;
    void	reset_last_nexthop();
    void	set_last_nexthop(const IPv6& ip6);
    const IPv6&	last_nexthop() const;
};

inline uint32_t
PacketAssemblerSpecState<IPv6>::max_entries() const
{
    return _max_entries;
}

inline void
PacketAssemblerSpecState<IPv6>::reset_last_nexthop()
{
    _lnh = IPv6::ALL_ONES();
}

inline void
PacketAssemblerSpecState<IPv6>::set_last_nexthop(const IPv6& ip6)
{
    _lnh = ip6;
}

inline const IPv6&
PacketAssemblerSpecState<IPv6>::last_nexthop() const
{
    return _lnh;
}


/**
 * @short Class for RIP Response Packet Assemblers.
 *
 * Both RIPv2 and RIPng have some oddities in packing and this interface
 * provides a consistent interface for that packing.
 *
 * This class has specialized IPv4 and IPv6 implementations.
 */
template <typename A>
class ResponsePacketAssembler {
public:
    typedef A				Addr;
    typedef IPNet<A>			Net;
    typedef PacketAssemblerSpecState<A> SpState;

public:
    /**
     * Constructor.
     *
     * @param port Port to take configuration information from.
     */
    ResponsePacketAssembler(Port<A>& port);

    /**
     * Constructor.
     *
     * @param sp Specialized state.
     */
    ResponsePacketAssembler(SpState& sp);

    /**
     * Destructor.
     */
    ~ResponsePacketAssembler();

    /**
     * Start assembling RIP response packet.
     */
    void packet_start(RipPacket<A>* pkt);

    /**
     * Add a route to RIP response packet.
     *
     * @return true if route was added, false if packet is full and would
     * have indicated this if only @ref packet_full was called.
     */
    bool packet_add_route(const Net&	net,
			  const Addr&	nexthop,
			  uint16_t	cost,
			  uint16_t	tag);

    /**
     * Ready-to-go accessor.
     *
     * @return true if packet has no more space for route entries.
     */
    bool packet_full() const;

    /**
     * Finish packet.  Some packet types require final stage processing
     * and this method gives that processing a chance to happen.  Common
     * usage is RIPv2 authentication.
     *
     * @param auth_packets a return-by-reference list with the
     * authenticated RIP packets (one copy for each valid authentication key).
     * @return true on success, false if a failure is detected.
     */
    bool packet_finish(list<RipPacket<A>* >& auth_packets);

private:
    /**
     * Copy Constructor (Disabled).
     */
    ResponsePacketAssembler(const ResponsePacketAssembler&);

    /**
     * Assignment Operator (Disabled).
     */
    ResponsePacketAssembler& operator=(const ResponsePacketAssembler&);

protected:
    RipPacket<A>* _pkt;
    uint32_t	  _pos;
    SpState	  _sp_state;
};


/**
 * @short Class to configure a RIP packet to be a table request.
 *
 * This class has specialized IPv4 and IPv6 implementations to cater for
 * address family differences.
 */
template <typename A>
class RequestTablePacketAssembler {
public:
    typedef A				Addr;
    typedef IPNet<A>			Net;
    typedef PacketAssemblerSpecState<A> SpState;

public:
    RequestTablePacketAssembler(Port<A>& port) : _sp_state(port) {}

    /**
     * Take RipPacket packet and make it into a table request packet.
     *
     * @param auth_packets a return-by-reference list with the
     * authenticated RIP packets (one copy for each valid authentication key).
     * @return true on success, false if an error is encountered.  Should
     * an error be encountered the reason is written to the xlog facility.
     */
    bool prepare(RipPacket<A>*		pkt,
		 list<RipPacket<A>* >&	auth_packets);

protected:
    SpState _sp_state;
};


// ----------------------------------------------------------------------------
// ResponsePacketAssembler<IPv4> implementation

template <>
inline
ResponsePacketAssembler<IPv4>::ResponsePacketAssembler(Port<IPv4>& port)
    : _pkt(0), _pos(0), _sp_state(port)
{
}

template <>
inline
ResponsePacketAssembler<IPv4>::ResponsePacketAssembler(SpState& sp)
    : _pkt(0), _pos(0), _sp_state(sp)
{
}

template <>
inline
ResponsePacketAssembler<IPv4>::~ResponsePacketAssembler()
{
}

template <>
inline void
ResponsePacketAssembler<IPv4>::packet_start(RipPacket<IPv4>* pkt)
{
    _pkt = pkt;

    const AuthHandlerBase& ah = _sp_state.ah();
    _pos = ah.head_entries();
    _pkt->set_max_entries(ah.head_entries() + ah.max_routing_entries());

    RipPacketHeaderWriter rph(_pkt->header_ptr());
    rph.initialize(RipPacketHeader::RESPONSE, RipPacketHeader::IPv4_VERSION);
}

template <>
inline bool
ResponsePacketAssembler<IPv4>::packet_full() const
{
    const AuthHandlerBase& ah = _sp_state.ah();
    return _pos == ah.max_routing_entries();
}

template <>
inline bool
ResponsePacketAssembler<IPv4>::packet_add_route(const Net&	net,
						const Addr&	nexthop,
						uint16_t	cost,
						uint16_t	tag)
{
    if (packet_full()) {
	return false;
    }
    uint8_t* pre_ptr = _pkt->route_entry_ptr(_pos);
    PacketRouteEntryWriter<IPv4> pre(pre_ptr);
    pre.initialize(tag, net, nexthop, cost);
    _pos++;
    return true;
}

template <>
inline bool
ResponsePacketAssembler<IPv4>::packet_finish(
    list<RipPacket<IPv4>* >&	auth_packets)
{
    AuthHandlerBase& ah = _sp_state.ah();

    _pkt->set_max_entries(_pos);
    size_t n_routes = 0;
    if ((ah.authenticate_outbound(*_pkt, auth_packets, n_routes) != true)
	|| (n_routes == 0)) {
	XLOG_ERROR("Outbound authentication error: %s\n", ah.error().c_str());
	return false;
    }
    return true;
}

// ----------------------------------------------------------------------------
// ResponsePacketAssembler<IPv6> implementation

template <>
inline
ResponsePacketAssembler<IPv6>::ResponsePacketAssembler(Port<IPv6>& port)
    : _pkt(0), _pos(0), _sp_state(port)
{
}

template <>
inline
ResponsePacketAssembler<IPv6>::ResponsePacketAssembler(SpState& sp)
    : _pkt(0), _pos(0), _sp_state(sp)
{
}

template <>
inline
ResponsePacketAssembler<IPv6>::~ResponsePacketAssembler()
{
}

template <>
inline void
ResponsePacketAssembler<IPv6>::packet_start(RipPacket<IPv6>* pkt)
{
    _pkt = pkt;
    _pos = 0;
    _sp_state.reset_last_nexthop();
    RipPacketHeaderWriter rph(_pkt->header_ptr());
    rph.initialize(RipPacketHeader::RESPONSE, RipPacketHeader::IPv6_VERSION);
}

template <>
inline bool
ResponsePacketAssembler<IPv6>::packet_full() const
{
    return (_sp_state.max_entries() - _pos) <= 2;
}

template <>
inline bool
ResponsePacketAssembler<IPv6>::packet_add_route(const Net&	net,
						const Addr&	nexthop,
						uint16_t	cost,
						uint16_t	tag)
{
    uint8_t* pre_ptr;

    if (packet_full()) {
	return false;
    }
    if (nexthop != _sp_state.last_nexthop()) {
	pre_ptr = _pkt->route_entry_ptr(_pos);
	PacketRouteEntryWriter<IPv6> pre(pre_ptr);
	pre.initialize_nexthop(nexthop);
	_pos++;
	_sp_state.set_last_nexthop(nexthop);
    }
    pre_ptr = _pkt->route_entry_ptr(_pos);
    PacketRouteEntryWriter<IPv6> pre(pre_ptr);
    pre.initialize_route(tag, net, cost);
    _pos++;
    return true;
}

template <>
inline bool
ResponsePacketAssembler<IPv6>::packet_finish(
    list<RipPacket<IPv6>* >&	auth_packets)
{
    _pkt->set_max_entries(_pos);

    RipPacket<IPv6>* packet = new RipPacket<IPv6>(*_pkt);
    auth_packets.push_back(packet);
    
    return true;
}


// ----------------------------------------------------------------------------
// RequestTablePacketAssembler<IPv4> implementation

template<>
inline bool
RequestTablePacketAssembler<IPv4>::prepare(RipPacket<IPv4>*	    pkt,
					   list<RipPacket<IPv4>* >& auth_packets)
{
    RipPacketHeaderWriter rph(pkt->header_ptr());
    rph.initialize(RipPacketHeader::REQUEST, RipPacketHeader::IPv4_VERSION);

    AuthHandlerBase& ah = _sp_state.ah();
    pkt->set_max_entries(1 + ah.head_entries());

    uint8_t* pre_ptr = pkt->route_entry_ptr(ah.head_entries());
    PacketRouteEntryWriter<IPv4> pre(pre_ptr);
    pre.initialize_table_request();

    size_t n_routes = 0;
    if ((ah.authenticate_outbound(*pkt, auth_packets, n_routes) != true)
	|| (n_routes == 0)) {
	XLOG_ERROR("Outbound authentication error: %s\n", ah.error().c_str());
	return false;
    }
    return true;
}


// ----------------------------------------------------------------------------
// RequestTablePacketAssembler<IPv6> implementation

template<>
inline bool
RequestTablePacketAssembler<IPv6>::prepare(RipPacket<IPv6>*	    pkt,
					   list<RipPacket<IPv6>* >& auth_packets)
{
    RipPacketHeaderWriter rph(pkt->header_ptr());
    rph.initialize(RipPacketHeader::REQUEST, RipPacketHeader::IPv6_VERSION);
    pkt->set_max_entries(1);

    uint8_t* pre_ptr = pkt->route_entry_ptr(0);
    PacketRouteEntryWriter<IPv6> pre(pre_ptr);
    pre.initialize_table_request();

    RipPacket<IPv6>* packet = new RipPacket<IPv6>(*pkt);
    auth_packets.push_back(packet);

    return true;
}

#endif // __RIP_PACKET_ASSEMBLY_HH__