Source: ../../bgp/next_hop_resolver.hh
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// -*- c-basic-offset: 4; tab-width: 8; indent-tabs-mode: t -*-
// Copyright (c) 2001-2009 XORP, Inc.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, Version 2, June
// 1991 as published by the Free Software Foundation. Redistribution
// and/or modification of this program under the terms of any other
// version of the GNU General Public License is not permitted.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. For more details,
// see the GNU General Public License, Version 2, a copy of which can be
// found in the XORP LICENSE.gpl file.
//
// XORP Inc, 2953 Bunker Hill Lane, Suite 204, Santa Clara, CA 95054, USA;
// http://xorp.net
// $XORP: xorp/bgp/next_hop_resolver.hh,v 1.37 2009/01/05 18:30:43 jtc Exp $
#ifndef __BGP_NEXT_HOP_RESOLVER_HH__
#define __BGP_NEXT_HOP_RESOLVER_HH__
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <list>
#include "libxorp/ipv4.hh"
#include "libxorp/ipv6.hh"
#include "libxorp/ipnet.hh"
#include "libxorp/ref_trie.hh"
#include "libxipc/xrl_std_router.hh"
template<class A> class NhLookupTable;
template<class A> class NextHopCache;
template<class A> class NextHopResolver;
template<class A> class NextHopRibRequest;
template<class A> class DecisionTable;
template<class A> class NHRequest;
/**
* Next hop resolvability and IGP distances are accessed through this class.
*
* Next hop resolvability and IGP distances are retrieved from the RIB
* and cached here in BGP. This retrieval process implicitly registers
* interest with the RIB regarding these next hops. Thus any changes in
* these next hops is signalled by the RIB to BGP via callbacks.
*
* If the state of a next hop changes (resolvable/unresolvable), or an
* IGP distance changes, then it is possible that a new route may now
* win the decision process. The decision process must therefore be
* re-run for all routes that are affected by a next hop change. This
* re-run of the decision process is achieved calling
* "igp_nexthop_changed" on the decision process.
*
* What questions can be asked about next hops? Is a next hop
* resolvable and if it is, what is the IGP distance.
*
* To answer questions about next hops three interfaces are supported:
* 1) An asynchronous interface that registers a callback which will be
* called when a response becomes available. For use by the (next
* hop) route table before decision. By the time a route gets to
* decision it *must* be known if the route is resolvable.
* 2) A synchronous interface for use by decision. It is a fatal error
* if this interface is called and the next hop is not in the
* cache. As by the time decision is called the cache should have been
* populated by use of the asynchronous interface.
* 3) A synchronous debugging interface.
*
* Cache maintainance:
* Every stored SubnetRoute in every rib in has a next hop. Every
* unique next hop has an entry in the cache. If a next hop lookup
* through the asynchronous interface causes a cache miss then an entry
* is created with a reference count of 1. Subsequent lookups through
* the next hop interface will cause the reference count to be
* incremented by 1. An interface to increase the reference count by
* more than one also exists. All route deletions should explicitly
* call a routine in here to decrement the reference count.
*/
class BGPMain;
template<class A>
class NextHopResolver {
public:
NextHopResolver(XrlStdRouter *xrl_router, EventLoop& eventloop,
BGPMain& bgp);
virtual ~NextHopResolver();
/**
* Add decision.
*
* Pass a pointer to the decision table into the next hop
* resolver. This pointer is used to notify the decision table
* when a next hop metric changes.
*
* @param decision Pointer to the decision table.
*/
void add_decision(DecisionTable<A> *decision);
/**
* Set the rib's name, allows for having a dummy rib or not having
* a RIB at all.
*/
bool register_ribname(const string& r);
/**
* Register interest in this nexthop.
*
* @param nexthop Nexthop.
* @param net_from_route The net that is associated with this
* nexthop in the NextHopLookupTable. Treated as an opaque id.
* @param requester Once the registration with the RIB suceeds the
* requester is called back.
* @return True if the registration succeed.
*/
virtual bool register_nexthop(A nexthop, IPNet<A> net_from_route,
NhLookupTable<A> *requester);
/**
* De-Register interest in this nexthop.
*
* @param nexthop Nexthop.
* @param net_from_route The net that is associated with this
* nexthop in the NextHopLookupTable. Treated as an opaque id.
* @param requester Original requester, not used.
* @return True if the registration succeed.
*/
virtual void deregister_nexthop(A nexthop, IPNet<A> net_from_route,
NhLookupTable<A> *requester);
/**
* Lookup next hop.
*
* If a "register_nexthop" request has been made and callback has
* taken place via the "requester" pointer, then the lookup is
* guaranteed to work.
*
* @param nexthop Next hop.
* @param resolvable Is this route resolvable.
* @param metric If this route is resolvable the metric of this
* route.
* @return True if this next hop is found.
*/
virtual bool lookup(const A nexthop, bool& resolvable,
uint32_t& metric) const;
/**
* Call from the RIB to notify us that a metric has changed.
*/
bool rib_client_route_info_changed(const A& addr,
const uint32_t& prefix_len,
const A& nexthop,
const uint32_t& metric);
/**
* Call from the RIB to notify us that any registrations with this
* address and prefix_len are now invalid.
*/
bool rib_client_route_info_invalid(const A& addr,
const uint32_t& prefix_len);
/**
* Next hop changed.
*
* Whenever a next hop changes this method should be called and
* the change will be rippled up to the decision process.
*
* @param nexthop The next hop that has changed.
*/
void next_hop_changed(A nexthop);
/**
* Next hop changed.
*
* Whenever a next hop changes this method should be called and
* the change will be rippled up to the decision process. However
* if a change occurs but the metrics don't change don't bother to
* ripple up the change there is no point.
*
* @param nexthop The next hop that has changed.
* @param old_resolves The old resolve value.
* @param old_metric The old metric value.
*/
void next_hop_changed(A nexthop, bool old_resolves, uint32_t old_metric);
/**
* Get NextHopRibRequest pointer.
*
* Used for testing.
*/
NextHopRibRequest<A> *get_next_hop_rib_request()
{
return &_next_hop_rib_request;
}
/**
* Get a reference to the main timer list
*/
EventLoop& eventloop() {return _eventloop;}
protected:
list<DecisionTable<A> *> _decision;
private:
string _ribname; // RIB name to use in XRL calls
XrlStdRouter *_xrl_router;
EventLoop& _eventloop;
BGPMain& _bgp;
NextHopCache<A> _next_hop_cache;
NextHopRibRequest<A> _next_hop_rib_request;
};
/**
* A cache of next hop information.
*
* BGP requires information regarding resolvabilty and metrics for
* next hops. This information is known by the RIB. Questions are
* asked of the RIB and the results are cached here. The RIB notes
* that questions have been asked and if the state of a next hop
* changes then this is reported back to BGP. In order to save space the
* RIB does not record information about each next hop but returns an
* address/prefix_len range for which the answer is valid.
*
* Not only can the RIB report changes but can also report that a
* previous entry is totally invalid. In the case that an entry is
* invalid all the next hops need to be re-requested.
*
*/
template<class A>
class NextHopCache {
public:
~NextHopCache();
/**
* Add an entry to our next hop table.
*
* @param addr Base address.
* @param nexthop Next hop that is being added to the trie.
* @param prefix_len The prefix_len that is masked with the nexhop.
* @param real_prefix_len The actual prefix_len that this next hop
* resolves too. This is only used to match with upcalls from the
* RIB.
* @param resolvable Is this route resolvable.
* @param metric If this route is resolvable its metric.
*/
void add_entry(A addr, A nexthop, int prefix_len, int real_prefix_len,
bool resolvable, uint32_t metric = 0);
/**
* Validate an entry.
*
* add_entry creates an entry with no nexthop references. The
* assumption is that a register_nexthop will follow shortly after
* initial creation. It is possible due to a deregister_nexthop
* coming in while we are waiting for a response from the RIB that
* the register_nexthop never happens. This method checks that the
* specified entry is referenced and if it isn't it is deleted.
*
* @param addr Base address.
* @param nexthop Next hop that is being added to the trie.
* @param prefix_len The prefix_len that is masked with the nexhop.
* @param real_prefix_len The actual prefix_len that this next hop
* @return true if the entry is in use.
*/
bool validate_entry(A addr, A nexthop, int prefix_len, int real_prefix_len);
/**
* Change an entry in the next hop table.
*
* @param addr The base address.
* @param prefix_len The prefix_len that this next hop
* resolves too. This is only used to match with upcalls from the
* RIB.
* @param metric If this route is resolvable its metric.
* @return The map of next hops with reference counts that were
* covered by this entry.
*
*/
map <A, int> change_entry(A addr, int prefix_len, uint32_t metric);
/**
* Delete an entry from the nexthop table.
*
* It is a fatal error to attempt to delete an entry that doesn't
* exist.
*
* @param addr Base address that is being removed from the trie.
* @param prefix_len The prefix_len.
* @return The map of next hops with reference counts that were
* covered by this entry.
*/
map <A, int> delete_entry(A addr, int prefix_len);
/**
* Lookup by base address
*
* @param addr Base address.
* @param prefix_len The prefix length.
* @param resolvable Is this route resolvable.
* @param metric If this route is resolvable the metric of this route.
* @return True if this next hop is found.
*
*/
bool lookup_by_addr(A addr, int prefix_len, bool& resolvable,
uint32_t& metric) const;
/**
* Lookup next hop.
*
* @param nexthop Next hop.
* @param resolvable Is this route resolvable.
* @param metric If this route is resolvable the metric of this
* route.
* @return True if this next hop is found.
*
*/
bool lookup_by_nexthop(A nexthop, bool& resolvable, uint32_t& metric)
const;
/**
* Lookup next hop without entry
*
* This lookup does not require that next hop is already
* known. That is the next hop is not in _nexthop_references.
*
* @param nexthop Next hop.
* @param resolvable Is this route resolvable.
* @param metric If this route is resolvable the metric of this
* route.
* @return True if this next hop is found.
*
*/
bool lookup_by_nexthop_without_entry(A nexthop, bool& resolvable,
uint32_t& metric) const;
/*
* Try and register this next hop.
*
* If this next hop is known or covered then this next hop is
* added to map of next hops that is associated with the
* NextHopEntry.
*
* @param nexthop Next hop.
* @param ref_cnt_incr How much to increase the reference count by.
* @return True if this next hop is known or its in a covered
* range.
*/
bool register_nexthop(A nexthop, int ref_cnt_incr = 1);
/*
* Deregister this next hop.
*
* The NextHopEntry has a map of next hops with reference
* counts. A deregister causes this next hop to be removed from
* its associated NextHopEntry. If the map becomes empty then the
* entry can be removed. If the map becomes empty then this fact
* is signalled in the return value and this next hop can be
* deregistered from the RIB.
*
* @param nexthop Next hop.
* @param last True if this is the last next hop and the entry
* has been freed.
* @param addr If this was the last entry the base address.
* @param prefix_len If this was the last entry the associated prefix_len.
* @return True if an entry was found.
*/
bool deregister_nexthop(A nexthop, bool& last, A& addr, uint32_t& prefix_len);
private:
struct NextHopEntry {
A _address; // Base address as returned by the RIB
#ifdef USE_NEXTHOP
A _nexthop; // The initial next hop. Used to find entry by
// prefix_len
#endif
map <A, int> _nexthop_references;
int _prefix_len;
int _real_prefix_len;
bool _resolvable;
int _metric;
};
typedef set<NextHopEntry *> RealPrefixEntry;
typedef RefTriePostOrderIterator<A, RealPrefixEntry> RealPrefixIterator;
typedef NextHopEntry PrefixEntry;
typedef RefTriePostOrderIterator<A, PrefixEntry *> PrefixIterator;
/**
* The NextHopEntry is indexed in two ways either by prefix_len or by
* real_prefix_len.
*
* Both of these data structures need to be kept in sync.
*/
RefTrie<A, PrefixEntry *> _next_hop_by_prefix;
RefTrie<A, RealPrefixEntry> _next_hop_by_real_prefix;
/**
* Given a real prefix_len entry return a prefix_len entry.
*
* @param pe A real prefix_len entry.
* @param addr Address.
* @param real_prefix_len The real prefix_len.
* @return A prefix_len entry if found 0 otherwise.
*/
PrefixEntry *rpe_to_pe(const RealPrefixEntry& pe, A addr,
int real_prefix_len) const;
/**
* Given a real prefix_len entry return a prefix_len entry.
*
* @param pe A real prefix_len entry.
* @param addr Address.
* @param real_prefix_len The real prefix_len.
* @return A prefix_len entry if found 0 otherwise.
*/
PrefixEntry *rpe_to_pe_delete(RealPrefixEntry& pe, A addr,
int real_prefix_len);
};
/**
* The queue of outstanding requests to the RIB. Requests can have
* arrived in this queue in two ways. A simple call down from the next
* hop table or due to the previous result being marked invalid by
* an upcall from the RIB. The class variables "_register" and
* "_reregister" denote how the entry was created. It is possible
* that an upcall from the RIB has caused a queue entry, followed
* by a downcall from the next hop table in which case both
* "_register" and "_reregister" will be true.
*/
template <class A>
class RibRequestQueueEntry {
public:
typedef enum {REGISTER, DEREGISTER} RegisterMode;
RibRequestQueueEntry(RegisterMode mode) : _register_mode(mode) {}
virtual ~RibRequestQueueEntry() {}
protected:
RegisterMode _register_mode;
};
template <class A>
class RibRegisterQueueEntry : public RibRequestQueueEntry<A> {
public:
typedef RibRequestQueueEntry<A> QE;
RibRegisterQueueEntry(A nexthop, IPNet<A> net_from_route,
NhLookupTable<A> *requester)
: RibRequestQueueEntry<A>(QE::REGISTER),
_nexthop(nexthop), _new_register(true),
_requests(net_from_route, requester),
_reregister(false), _ref_cnt(0)
{}
RibRegisterQueueEntry(A nexthop, uint32_t ref_cnt, bool resolvable,
uint32_t metric)
: RibRequestQueueEntry<A>(QE::REGISTER),
_nexthop(nexthop), _new_register(false), _reregister(true),
_ref_cnt(ref_cnt), _resolvable(resolvable), _metric(metric)
{}
void register_nexthop(IPNet<A> net_from_route,
NhLookupTable<A> *requester) {
XLOG_ASSERT(true == _reregister || true == _new_register);
XLOG_ASSERT(QE::_register_mode == QE::REGISTER);
_new_register = true;
_requests.add_request(net_from_route, requester);
}
bool deregister_nexthop(IPNet<A> net_from_route,
NhLookupTable<A> *requester) {
XLOG_ASSERT(true == _reregister || true == _new_register);
XLOG_ASSERT(QE::_register_mode == QE::REGISTER);
if (_new_register && _requests.remove_request(net_from_route,
requester)) {
return true;
}
if (_reregister) {
XLOG_ASSERT(_ref_cnt > 0);
_ref_cnt--;
return true;
}
return false;
}
void reregister_nexthop(uint32_t ref_cnt, bool resolvable,
uint32_t metric) {
XLOG_ASSERT(false == _reregister);
XLOG_ASSERT(0 == _ref_cnt);
XLOG_ASSERT(QE::_register_mode == QE::REGISTER);
_reregister = true;
_ref_cnt = ref_cnt;
_resolvable = resolvable;
_metric = metric;
}
bool resolvable() const {
assert(QE::_register_mode == QE::REGISTER);
return _resolvable;
}
bool reregister() const {
assert(QE::_register_mode == QE::REGISTER);
return _reregister;
}
bool new_register() const {
assert(QE::_register_mode == QE::REGISTER);
return _new_register;
}
bool metric() const {
assert(QE::_register_mode == QE::REGISTER);
return _metric;
}
const A& nexthop() const {
return _nexthop;
}
uint32_t ref_cnt() const {
return _ref_cnt;
}
NHRequest<A>& requests() {
return _requests;
}
private:
/*
** Register info.
*/
A _nexthop;
bool _new_register;
NHRequest<A> _requests;
/*
** Reregister info.
*/
bool _reregister;
uint32_t _ref_cnt;
/**
* The old answer if we are in the process of reregistering so
* that lookups will be satisfied with this old answer.
*/
bool _resolvable;
uint32_t _metric;
};
template <class A>
class RibDeregisterQueueEntry : public RibRequestQueueEntry<A> {
public:
typedef RibRequestQueueEntry<A> QE;
RibDeregisterQueueEntry(A base_addr, uint32_t prefix_len)
: RibRequestQueueEntry<A>(QE::DEREGISTER),
_base_addr(base_addr), _prefix_len(prefix_len)
{}
const A& base_addr() const { return _base_addr;}
uint32_t prefix_len() const { return _prefix_len;}
private:
/*
** Deregister info.
*/
A _base_addr;
uint32_t _prefix_len;
};
/**
* Make requests of the RIB and get responses.
*
* At any time there is only ever one outstanding request to the
* RIB. Firstly we don't want to overrun the RIB with
* requests. Secondly it is possible that different next hops in the
* queue of requests may resolve to the same address/prefix_len answer
* (see below).
*/
template<class A>
class NextHopRibRequest {
public:
NextHopRibRequest(XrlStdRouter *,
NextHopResolver<A>& next_hop_resolver,
NextHopCache<A>& next_hop_cache,
BGPMain& bgp);
~NextHopRibRequest();
bool register_ribname(const string& r) { _ribname = r; return true; }
/**
* Register interest with the RIB about this next hop.
*
* @param nexthop The next hop that we are attempting to resolve.
* @param net The subnet that this next hop is associated with.
* @param requester The lookup table that wants to be notified
* when the response comes back.
*/
void register_nexthop(A nexthop, IPNet<A> net,
NhLookupTable<A> *requester);
/**
* Send the next queued request
*/
void send_next_request();
/**
* Actually register interest with the RIB.
*
* A small method that will be specialized to differentiate
* between IPv4 and IPv6.
*
* @param nexthop The next hop that we are attempting to resolve.
*/
void register_interest(A nexthop);
/**
* XRL callback from register_interest.
*/
void register_interest_response(const XrlError& error,
const bool *resolves,
const A *addr,
const uint32_t *prefix_len,
const uint32_t *real_prefix_len,
const A *actual_nexthop,
const uint32_t *metric,
const A nexthop_interest,
const string comment);
/**
* An unmatched invalidate has been received.
*/
bool premature_invalid(const A& addr, const uint32_t& prefix_len);
/**
* An invalidate has been received after we deregistered interest.
*/
bool tardy_invalid(const A& addr, const uint32_t& prefix_len);
/**
* Deregister interest with the RIB about this next hop.
*
* @param nexthop The next hop that we are attempting to resolve.
* @param net The subnet that this next hop is associated with.
* @param requester The lookup table that wants to be notified
* when the response comes back.
* @return True if an entry was found to remove.
*/
bool deregister_nexthop(A nexthop, IPNet<A> net,
NhLookupTable<A> *requester);
/**
* Reregister interest with the RIB about this next hop.
*
* This method is used when the RIB tells us that all previous
* registrations have become invalid. This forces us to re-request
* information. We save the old state (resolvable, metric) just in
* case the following events occur:
* <PRE>
* 1) Register from next hop table.
* 2) route_info_invalid from RIB.
* 3) lookup from decision.
* </PRE>
* This ordering of events may not be possible just in case it is
* save the old result and return it in a lookup.
*
* @param nexthop The next hop that we are attempting to resolve.
* @param ref_cnt The number of subnets using this nexthop.
* @param resolvable Was the previous result resolvable.
* @param metric If the previous result was resolvable the metric.
*/
void reregister_nexthop(A nexthop, uint32_t ref_cnt, bool resolvable,
uint32_t metric);
/**
* lookup next hop.
*
* @param nexthop Next hop.
* @param resolvable Is this route resolvable.
* @param metric If this route is resolvable the metric of this
* route.
* @return True if this next hop is found.
*
*/
bool lookup(const A& nexthop, bool& resolvable, uint32_t& metric) const;
/*
* Deregister ourselves from the RIB for this next hop
*
* @param nexthop The next hop.
* @param prefix_len The prefix_len we registered with.
*/
void deregister_from_rib(const A& nexthop, uint32_t prefix_len);
/*
* Deregister ourselves from the RIB for this next hop
*
* @param nexthop The next hop.
* @param prefix_len The prefix_len we registered with.
*/
void deregister_interest(A nexthop, uint32_t prefix_len);
/**
* XRL response method.
*
* @param error Error returned by xrl call.
* @param comment Comment string used for diagnostic purposes.
*/
void deregister_interest_response(const XrlError& error,
A addr,
uint32_t prefix_len,
string comment);
private:
string _ribname;
XrlStdRouter *_xrl_router;
NextHopResolver<A>& _next_hop_resolver;
NextHopCache<A>& _next_hop_cache;
BGPMain& _bgp;
/**
* Are we currently waiting for a response from the RIB.
*/
bool _busy;
bool _invalid; // True if received an unmatched invalid call.
IPNet<A> _invalid_net; // Saved invalid subnet.
bool _tardy_invalid; // True if we are expecting an invalid
// from the RIB.
IPNet<A> _tardy_invalid_net;// Saved invalid subnet.
/**
* The queue of outstanding requests.
*/
list<RibRequestQueueEntry<A> *> _queue;
/**
* Used by the destructor to delete all the "RibRequestQueueEntry" objects
* that have been allocated.
*/
static void zapper(RibRequestQueueEntry<A> *req) { delete req; }
};
template<class A>
class NHRequest {
public:
NHRequest();
NHRequest(IPNet<A> net,
NhLookupTable<A> *requester);
void add_request(IPNet<A> net,
NhLookupTable<A> *requester);
bool remove_request(IPNet<A> net,
NhLookupTable<A> *requester);
const set <NhLookupTable<A>*>& requesters() const {
return _requesters;
}
const set <IPNet<A> >& request_nets(NhLookupTable<A>* requester) const;
int requests() const { return _request_total; }
private:
set <NhLookupTable<A> *> _requesters;
map <NhLookupTable<A> *, multiset<IPNet<A> > > _request_map;
mutable map <NhLookupTable<A> *, set<IPNet<A> > > _answer;
int _request_total;
};
#endif // __BGP_NEXT_HOP_RESOLVER_HH__
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