sync with trunk

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/trac423@3856 e5f2f494-b856-4b98-b285-d166d9295462

ChangeLog

+  128.  [build]     vorner
+	Test for query name = '.', type = DS to authoritative nameserver for root
+	zone was added.
+	(Trac #85, svn r3836)
+
+  127.  [bug]       stephen
+	During normal operation process termination and resurrection messages
+	are now output regardless of the state of the verbose flag.
+	(Trac #229, svn r3828)
+
+  126.  [func]      stephen, vorner, ocean
+	The Nameserver Address Store (NSAS) component has been added. It takes
+	care of choosing an IP address of a nameserver when a zone needs to be
+	contacted.
+	(Trac #356, Trac #408, svn r3823)
+
 bind10-devel-20101201 released on December 01, 2010
 
   125.  [func]		jelte

configure.ac

@@ -318,7 +318,7 @@ if test "${boost_include_path}" ; then
 	BOOST_INCLUDES="-I${boost_include_path}"
 	CPPFLAGS="$CPPFLAGS $BOOST_INCLUDES"
 fi
-AC_CHECK_HEADERS([boost/shared_ptr.hpp boost/foreach.hpp],,
+AC_CHECK_HEADERS([boost/shared_ptr.hpp boost/foreach.hpp boost/interprocess/sync/interprocess_upgradable_mutex.hpp],,
   AC_MSG_ERROR([Missing required header files.]))
 CPPFLAGS="$CPPFLAGS_SAVES"
 AC_SUBST(BOOST_INCLUDES)
@@ -518,6 +518,8 @@ AC_CONFIG_FILES([Makefile
                  src/lib/datasrc/Makefile
                  src/lib/datasrc/tests/Makefile
                  src/lib/xfr/Makefile
+                 src/lib/nsas/Makefile
+                 src/lib/nsas/tests/Makefile
                ])
 AC_OUTPUT([src/bin/cfgmgr/b10-cfgmgr.py
            src/bin/cfgmgr/tests/b10-cfgmgr_test.py

doc/Doxyfile

@@ -568,7 +568,7 @@ WARN_LOGFILE           =
 # directories like "/usr/src/myproject". Separate the files or directories
 # with spaces.
 
-INPUT                  = ../src/lib/cc ../src/lib/config ../src/lib/dns ../src/lib/exceptions ../src/lib/datasrc ../src/bin/auth ../src/lib/bench
+INPUT                  = ../src/lib/cc ../src/lib/config ../src/lib/dns ../src/lib/exceptions ../src/lib/datasrc ../src/bin/auth ../src/lib/bench ../src/lib/nsas
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is

doc/guide/bind10-guide.html

@@ -128,7 +128,7 @@
             libraries, to build BIND 10 from source code.
           </p></div><p>
           Building from source code requires the Boost
-          build-time headers. At least Boost version 1.34 is required.
+          build-time headers. At least Boost version 1.35 is required.
   
   
         </p><p>

doc/guide/bind10-guide.xml

@@ -274,7 +274,7 @@ var/
 
         <para>
           Building from source code requires the Boost
-          build-time headers. At least Boost version 1.34 is required.
+          build-time headers. At least Boost version 1.35 is required.
   <!-- TODO: we don't check for this version -->
   <!-- NOTE: jreed has tested with 1.34, 1.38, and 1.41. -->
         </para>

src/bin/bind10/bind10.py.in

@@ -612,27 +612,44 @@ class BoB:
                 raise
             if pid == 0: break
             if pid in self.processes:
+
+                # One of the processes we know about.  Get information on it.
                 proc_info = self.processes.pop(pid)
                 proc_info.restart_schedule.set_run_stop_time()
                 self.dead_processes[proc_info.pid] = proc_info
-                if self.verbose:
-                    sys.stdout.write("[bind10] Process %s (PID %d) died.\n" % 
-                                     (proc_info.name, proc_info.pid))
-                if proc_info.name == "b10-msgq":
-                    if self.verbose and self.runnable:
+
+                # Write out message, but only if in the running state:
+                # During startup and shutdown, these messages are handled
+                # elsewhere.
+                if self.runnable:
+                    if exit_status is None:
+                        sys.stdout.write(
+                            "[bind10] Process %s (PID %d) died: exit status not available" % 
+                            (proc_info.name, proc_info.pid))
+                    else:
+                        sys.stdout.write(
+                            "[bind10] Process %s (PID %d) terminated, exit status = %d\n" % 
+                            (proc_info.name, proc_info.pid, exit_status))
+
+                    # Was it a special process?
+                    if proc_info.name == "b10-msgq":
                         sys.stdout.write(
                                  "[bind10] The b10-msgq process died, shutting down.\n")
-                    self.runnable = False
+                        self.runnable = False
             else:
                 sys.stdout.write("[bind10] Unknown child pid %d exited.\n" % pid)
 
     def restart_processes(self):
-        """Restart any dead processes.
-        Returns the time when the next process is ready to be restarted. 
-          If the server is shutting down, returns 0.
-          If there are no processes, returns None.
-        The values returned can be safely passed into select() as the 
-        timeout value."""
+        """
+            Restart any dead processes:
+
+            * Returns the time when the next process is ready to be restarted. 
+            * If the server is shutting down, returns 0.
+            * If there are no processes, returns None.
+
+            The values returned can be safely passed into select() as the 
+            timeout value.
+        """
         next_restart = None
         # if we're shutting down, then don't restart
         if not self.runnable:
@@ -649,13 +666,12 @@ class BoB:
             else:
                 if self.verbose:
                     sys.stdout.write("[bind10] Resurrecting dead %s process...\n" % 
-                                     proc_info.name)
+                        proc_info.name)
                 try:
                     proc_info.respawn()
                     self.processes[proc_info.pid] = proc_info
-                    if self.verbose:
-                        sys.stdout.write("[bind10] Resurrected %s (PID %d)\n" %
-                                         (proc_info.name, proc_info.pid))
+                    sys.stdout.write("[bind10] Resurrected %s (PID %d)\n" %
+                                     (proc_info.name, proc_info.pid))
                 except:
                     still_dead[proc_info.pid] = proc_info
         # remember any processes that refuse to be resurrected

src/lib/Makefile.am

-SUBDIRS = exceptions dns cc config datasrc python xfr bench
+SUBDIRS = exceptions dns cc config datasrc python xfr bench nsas

src/lib/datasrc/tests/datasrc_unittest.cc

@@ -877,12 +877,32 @@ TEST_F(DataSrcTest, NSECZonecutOfNonsecureZone) {
     EXPECT_TRUE(it->isLast());
 }
 
-TEST_F(DataSrcTest, RootDSQuery) {
+// Test sending a DS query to root (nonsense, but it should survive)
+TEST_F(DataSrcTest, RootDSQuery1) {
     EXPECT_NO_THROW(createAndProcessQuery(Name("."), RRClass::IN(),
                                           RRType::DS()));
     headerCheck(msg, Rcode::REFUSED(), true, false, true, 0, 0, 0);
 }
 
+// The same, but when we have the root zone
+// (which triggers rfc4035 section 3.1.4.1)
+TEST_F(DataSrcTest, RootDSQuery2) {
+    // The message
+    msg.makeResponse();
+    msg.setOpcode(Opcode::QUERY());
+    msg.addQuestion(Question(Name("."), RRClass::IN(), RRType::DS()));
+    msg.setHeaderFlag(Message::HEADERFLAG_RD);
+    // Prepare the source
+    DataSrcPtr sql3_source = DataSrcPtr(new Sqlite3DataSrc);
+    ConstElementPtr sqlite_root = Element::fromJSON(
+        "{ \"database_file\": \"" TEST_DATA_DIR "/test-root.sqlite3\"}");
+    EXPECT_NO_THROW(sql3_source->init(sqlite_root));
+    // Make the query
+    EXPECT_NO_THROW(performQuery(*sql3_source, cache, msg));
+
+    headerCheck(msg, Rcode::NOERROR(), true, true, true, 0, 1, 0);
+}
+
 TEST_F(DataSrcTest, DSQueryFromCache) {
     // explicitly enable hot spot cache
     cache.setEnabled(true);

src/lib/dns/tests/testdata/edns_toWire4.spec

 #
-# Same as edns_toWire1 but setting the DO bit
+# Same as edns_toWire1 but setting the DO bit, and using an unusual
+# UDP payload size
 #
 [edns]
 do: 1

src/lib/nsas/Makefile.am

+SUBDIRS = . tests
+
+AM_CPPFLAGS = -I$(top_srcdir)/src/lib -I$(top_builddir)/src/lib
+AM_CPPFLAGS += $(BOOST_INCLUDES)
+AM_CPPFLAGS += -I$(top_srcdir)/src/lib/dns -I$(top_builddir)/src/lib/dns
+AM_CPPFLAGS += -I$(top_srcdir)/src/lib/nsas -I$(top_builddir)/src/lib/nsas
+AM_CPPFLAGS += $(SQLITE_CFLAGS)
+AM_CXXFLAGS = $(B10_CXXFLAGS)
+
+if USE_GXX
+# Some versions of GCC warn about some versions of Boost regarding
+# missing initializer for members in its posix_time.
+# https://svn.boost.org/trac/boost/ticket/3477
+AM_CXXFLAGS += -Wno-missing-field-initializers
+endif
+
+if USE_CLANGPP
+# clang++ complains about unused function parameters in some boost header
+# files.
+AM_CXXFLAGS += -Wno-unused-parameter
+endif
+
+lib_LTLIBRARIES = libnsas.la
+libnsas_la_SOURCES  = address_entry.h address_entry.cc
+libnsas_la_SOURCES += asiolink.h
+libnsas_la_SOURCES += hash.cc hash.h
+libnsas_la_SOURCES += hash_deleter.h
+libnsas_la_SOURCES += hash_key.cc hash_key.h
+libnsas_la_SOURCES += hash_table.h
+libnsas_la_SOURCES += lru_list.h
+libnsas_la_SOURCES += nameserver_address_store.cc nameserver_address_store.h
+libnsas_la_SOURCES += nameserver_address.h nameserver_address.cc
+libnsas_la_SOURCES += nameserver_entry.cc nameserver_entry.h
+libnsas_la_SOURCES += nsas_entry_compare.h
+libnsas_la_SOURCES += nsas_entry.h nsas_types.h
+libnsas_la_SOURCES += zone_entry.cc zone_entry.h
+libnsas_la_SOURCES += fetchable.h
+libnsas_la_SOURCES += address_request_callback.h
+libnsas_la_SOURCES += resolver_interface.h
+libnsas_la_SOURCES += random_number_generator.h
+
+CLEANFILES = *.gcno *.gcda

src/lib/nsas/README

+For an overview of the Nameserver Address Store, see the requirements and design
+documents at http://bind10.isc.org/wiki/Resolver.
+
+At the time of writing (19 October 2010), the file asiolink.h is present in this
+directory only for the purposes of development.  When the recursor's
+asynchronous I/O code has been finished, this will be removed and the NSAS will
+use the "real" code.

src/lib/nsas/TODO

+Long term:
+* Make a mechanism the cache (which does not exist at the time of writing this
+  note) will be able to notify the NSAS that something has changed (address,
+  new nameserver, etc). Because the cache will have access to the data and
+  knows when it changes (it updates its structures), it is the best place. It
+  will be caching even data like authority and additional sections. It will
+  notify us somehow (we will need to tell it when).
+
+  The changes we need to know about is when set of nameservers or set of
+  addresses for a nameserver change and when a NS record or nameserver's A or
+  AAAA record is explicitly removed from the cache.
+* Optimisation to pass max two outstanding queries on the network (but fetch
+  everything from cache right away). The first can be done by having number of
+  packets on the network, with max of 4 (each query are 2 of them, A and AAAA),
+  if it drops to 2, another one can be send.
+* Add the cache cookies/contexts.
+* Logging.
+* Remove LRU from the nameserver entries, drop them when they are not
+  referenced by any zone entry. This will remove duplicates, keep the RTTs
+  longer and will provide access to everything that exists. This is
+  tricky, though, because we need to be thread safe. There seems to be
+  solution to use weak_ptr inside the hash_table instead of shared_ptr and
+  catch the exception inside get() (and getOrAdd) and delete the dead pointer.
+* Better way to dispatch all calbacks in a list is needed. We take them out of
+  the list and dispatch them one by one.  This is wrong because when an
+  exception happens inside the callback, we lose the ones not dispatched yet.
+
+  What should be done in this situation anyway? Putting them back? Will anybody
+  still call them? Taking them one by one?
+
+  Or recommend that if the result is really needed, that destruction of it
+  should be considered failure if it wasn't called yet? Make it the default
+  (eg. signal failure by destruction or call that function from destructor)?
+* Make a zone entry hash table have multiple LRU lists, each one for part of the
+  slots. This will prevent locking contention while still keeping close to
+  the theoretical LRU behaviour (statistically, accesses to each of the part
+  should be as common as to others).
+
+  It might be a good idea to encapsulate the LRUs into the hash table directly
+  (or create a class holding both the hash table and the LRU lists).

src/lib/nsas/address_entry.cc

+// Copyright (C) 2010  Internet Systems Consortium, Inc. ("ISC")
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+// $Id$
+
+/// \file address_entry.cc
+///
+/// This file exists to define the single constant \c AddressEntry::UNREACHABLE,
+/// equal to the value \c UINT32_MAX.
+///
+/// Ideally we could use \c UINT32_MAX directly in the header file, but this
+/// constant is defined in \c stdint.h only if the macro \c __STDC_LIMIT_MACROS
+/// is defined first. (This apparently is the C89 standard.)  Defining the
+/// macro in \c address_entry.h before including \c stdint.h doesn't work as
+/// it is possible that in a source file, \c stdint.h will be included before
+/// \c address_entry.h.  In that case, the \c stdint.h include sentinel will
+/// prevent \c stdint.h being included a second time and the value won't be
+/// defined.
+///
+/// The easiest solution is the one presented here: declare the value as a
+/// static class constant, and define it in this source file.  As we can control
+/// the order of include files, this ensures that the value is defined.
+
+#define __STDC_LIMIT_MACROS
+#include <stdint.h>
+
+#include "address_entry.h"
+
+namespace isc {
+namespace nsas {
+const uint32_t AddressEntry::UNREACHABLE = UINT32_MAX;
+}
+}

src/lib/nsas/address_entry.h

+// Copyright (C) 2010  Internet Systems Consortium, Inc. ("ISC")
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+// $Id$
+
+#ifndef __ADDRESS_ENTRY_H
+#define __ADDRESS_ENTRY_H
+
+/// \brief Address Entry
+///
+/// Lightweight class that couples an address with a RTT and provides some
+/// convenience methods for accessing and updating the information.
+
+#include <stdint.h>
+#include "asiolink.h"
+
+namespace isc {
+namespace nsas {
+
+class AddressEntry {
+public:
+    /// Creates an address entry given IOAddress entry and RTT
+    /// This is the only constructor; the default copy constructor and
+    /// assignment operator are valid for this object.
+    ///
+    /// \param address Address object representing this address
+    /// \param rtt Initial round-trip time
+    AddressEntry(const asiolink::IOAddress& address, uint32_t rtt = 0) :
+        address_(address), rtt_(rtt), dead_until_(0)
+    {}
+
+    /// \return Address object
+    asiolink::IOAddress getAddress() const {
+        return address_;
+    }
+
+    /// \return Current round-trip time
+    uint32_t getRTT() {
+        if(dead_until_ != 0 && time(NULL) >= dead_until_){
+            dead_until_ = 0;
+            rtt_ = 1; //reset the rtt to a small value so it has an opportunity to be updated
+        }
+
+        return rtt_;
+    }
+
+    /// Set current RTT
+    ///
+    /// \param rtt New RTT to be associated with this address
+    void setRTT(uint32_t rtt) {
+        if(rtt == UNREACHABLE){
+            dead_until_ = time(NULL) + 5*60;//Cache the unreachable server for 5 minutes (RFC2308 sec7.2)
+        }
+
+        rtt_ = rtt;
+    }
+
+    /// Mark address as unreachable.
+    void setUnreachable() {
+        setRTT(UNREACHABLE);   // Largest long number is code for unreachable
+    }
+
+    /// Check if address is unreachable
+    ///
+    /// \return true if the address is unreachable, false if not
+    bool isUnreachable() {
+        return (getRTT() == UNREACHABLE); // The getRTT() will check the cache time for unreachable server
+    }
+
+    /// \return true if the object is a V4 address
+    bool isV4() const {
+        return (address_.getFamily() == AF_INET);
+    }
+
+    /// \return true if the object is a V6 address
+    bool isV6() const {
+        return (address_.getFamily() == AF_INET6);
+    }
+
+    // Next element is defined public for testing
+    static const uint32_t UNREACHABLE;  ///< RTT indicating unreachable address
+
+private:
+    asiolink::IOAddress address_;       ///< Address
+    uint32_t        rtt_;               ///< Round-trip time
+    time_t  dead_until_;                ///< Dead time for unreachable server
+};
+
+}   // namespace dns
+}   // namespace isc
+
+
+#endif // __ADDRESS_ENTRY_H

src/lib/nsas/address_request_callback.h

+// Copyright (C) 2010  Internet Systems Consortium, Inc. ("ISC")
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+// $Id$
+
+#ifndef __ADDRESS_REQUEST_CALLBACK_H
+#define __ADDRESS_REQUEST_CALLBACK_H
+
+#include "asiolink.h"
+#include "nameserver_address.h"
+
+namespace isc {
+namespace nsas {
+
+/// \brief Callback When Address Obtained
+///
+/// This is the callback object used to return an address of a nameserver to a
+/// caller.  It (or a subclass of it) is passed to the NSAS when a request is
+/// made for the address of a nameserver.  When an address is available,
+/// methods on the passed objects are called.
+///
+/// Note that there is no guarantee as to when the methods are called; they
+/// could be called after the function call that made the address request has
+/// returned the caller.  Equally, the call could complete before that function
+/// call returns.  It is up to the caller to handle all cases.
+///
+/// In terms of use, a shared pointer to this object is passed to the NSAS.
+/// The NSAS will store the object via a shared pointer and after the callback
+/// will delete the pointer.  Whether this results in the deletion of the
+/// callback object is up to the caller - if the caller wants to retain it
+/// they should keep the shared pointer.
+
+class AddressRequestCallback {
+public:
+
+    /// Default constructor, copy contructor and assignment operator
+    /// are implicitly present and are OK.
+
+    /// \brief Virtual Destructor
+    virtual ~AddressRequestCallback()
+    {}
+
+    /// \brief Success Callback
+    ///
+    /// This method is used when an address has been retrieved for the request.
+    ///
+    /// \param address Address to be used to access the nameserver.
+    virtual void success(const NameserverAddress& address) = 0;
+
+    /// \brief Unreachable
+    ///
+    /// This method is called when a request is made for an address, but all
+    /// the addresses for the zone are marked as unreachable.  This may be
+    /// due to the NS records being unobtainable, or the A records for known
+    /// nameservers being unobtainable.
+    virtual void unreachable() = 0;
+
+};
+
+} // namespace nsas
+} // namespace isc
+
+#endif // __ADDRESS_REQUEST_CALLBACK_H

src/lib/nsas/asiolink.h

+// Copyright (C) 2010  Internet Systems Consortium, Inc. ("ISC")
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+// $Id$
+
+#ifndef __ASIOLINK_H
+#define __ASIOLINK_H
+
+#include <string>
+#include <sys/socket.h>
+
+namespace asiolink {
+
+/// \brief IO Address Dummy Class
+///
+/// As part of ther recursor, Evan has written the asiolink.h file, which
+/// encapsulates some of the boost::asio classes.  Until these are checked
+/// into trunk and merged with this branch, these dummy classes should fulfill
+/// their function.
+
+class IOAddress {
+public:
+    /// \param address_str String representing the address
+    IOAddress(const std::string& address_str) : address_(address_str)
+    {}
+
+    /// \param Just a virtual destructor
+    virtual ~ IOAddress() { }
+
+    /// \return Textual representation of the address
+    std::string toText() const
+    {return address_;}
+
+    /// \return Address family of the address
+    virtual short getFamily() const {
+        return ((address_.find(".") != std::string::npos) ? AF_INET : AF_INET6);
+    }
+
+    /// \return true if two addresses are equal
+    bool equal(const IOAddress& address)
+    {return (toText() == address.toText());}
+
+private:
+    std::string     address_;       ///< Address represented
+};
+
+}   // namespace asiolink
+
+#endif // __ASIOLINK_H

src/lib/nsas/fetchable.h

+// Copyright (C) 2010  CZ NIC
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+// $id$
+
+#ifndef __FETCHABLE_H
+#define __FETCHABLE_H
+
+/**
+ * \file fetchable.h
+ * \short Interface of information that can be fetched.
+ */
+
+namespace isc {
+namespace nsas {
+
+/**
+ * \short Interface of information that can be fetched.
+ *
+ * This just holds a state of information that can be fetched from somewhere.
+ * No locking is performed, if it is desirable, it should be locked manually.
+ */
+class Fetchable {
+    public:
+        /// \short States the Fetchable object can be in.
+        enum State {
+            /// \short No one yet asked for the information.
+            NOT_ASKED,
+            /// \short The information is too old and should not be used.
+            EXPIRED,
+            /// \short The information is asked for but it did not arrive.
+            IN_PROGRESS,
+            /// \short It is not possible to get the information.
+            UNREACHABLE,
+            /// \short The information is already present.
+            READY
+        };
+        /// \short Constructors
+        //@{
+        /// This creates the Fetchable object in the given state.
+        Fetchable(State state = NOT_ASKED) :
+            state_(state)
+        { }
+        //@}
+        /// \short Getter and setter of current state.
+        //@{
+        State getState() const { return state_; }
+        void setState(State state) { state_ = state; }
+        //@}