gecko/netwerk/dns/nsHostResolver.h
2011-03-28 15:58:49 -04:00

269 lines
10 KiB
C++

/* vim:set ts=4 sw=4 sts=4 et cin: */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla.
*
* The Initial Developer of the Original Code is IBM Corporation.
* Portions created by IBM Corporation are Copyright (C) 2003
* IBM Corporation. All Rights Reserved.
*
* Contributor(s):
* IBM Corp.
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef nsHostResolver_h__
#define nsHostResolver_h__
#include "nscore.h"
#include "nsAtomicRefcnt.h"
#include "prcvar.h"
#include "prclist.h"
#include "prnetdb.h"
#include "pldhash.h"
#include "nsISupportsImpl.h"
class nsHostResolver;
class nsHostRecord;
class nsResolveHostCallback;
/* XXX move this someplace more generic */
#define NS_DECL_REFCOUNTED_THREADSAFE(classname) \
private: \
nsAutoRefCnt _refc; \
public: \
PRInt32 AddRef() { \
PRInt32 n = NS_AtomicIncrementRefcnt(_refc); \
NS_LOG_ADDREF(this, n, #classname, sizeof(classname)); \
return n; \
} \
PRInt32 Release() { \
PRInt32 n = NS_AtomicDecrementRefcnt(_refc); \
NS_LOG_RELEASE(this, n, #classname); \
if (n == 0) \
delete this; \
return n; \
}
#define MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY 3
#define MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY 5
#define MAX_RESOLVER_THREADS (MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY + \
MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY)
struct nsHostKey
{
const char *host;
PRUint16 flags;
PRUint16 af;
};
/**
* nsHostRecord - ref counted object type stored in host resolver cache.
*/
class nsHostRecord : public PRCList, public nsHostKey
{
public:
NS_DECL_REFCOUNTED_THREADSAFE(nsHostRecord)
/* instantiates a new host record */
static nsresult Create(const nsHostKey *key, nsHostRecord **record);
/* a fully resolved host record has either a non-null |addr_info| or |addr|
* field. if |addr_info| is null, it implies that the |host| is an IP
* address literal. in which case, |addr| contains the parsed address.
* otherwise, if |addr_info| is non-null, then it contains one or many
* IP addresses corresponding to the given host name. if both |addr_info|
* and |addr| are null, then the given host has not yet been fully resolved.
* |af| is the address family of the record we are querying for.
*/
/* the lock protects |addr_info| and |addr_info_gencnt| because they
* are mutable and accessed by the resolver worker thread and the
* nsDNSService2 class. |addr| doesn't change after it has been
* assigned a value. only the resolver worker thread modifies
* nsHostRecord (and only in nsHostResolver::OnLookupComplete);
* the other threads just read it. therefore the resolver worker
* thread doesn't need to lock when reading |addr_info|.
*/
PRLock *addr_info_lock;
int addr_info_gencnt; /* generation count of |addr_info| */
PRAddrInfo *addr_info;
PRNetAddr *addr;
PRBool negative; /* True if this record is a cache of a failed lookup.
Negative cache entries are valid just like any other
(though never for more than 60 seconds), but a use
of that negative entry forces an asynchronous refresh. */
PRUint32 expiration; /* measured in minutes since epoch */
PRBool HasResult() const { return addr_info || addr || negative; }
private:
friend class nsHostResolver;
PRCList callbacks; /* list of callbacks */
PRBool resolving; /* true if this record is being resolved, which means
* that it is either on the pending queue or owned by
* one of the worker threads. */
PRBool onQueue; /* true if pending and on the queue (not yet given to getaddrinfo())*/
PRBool usingAnyThread; /* true if off queue and contributing to mActiveAnyThreadCount */
~nsHostRecord();
};
/**
* ResolveHost callback object. It's PRCList members are used by
* the nsHostResolver and should not be used by anything else.
*/
class NS_NO_VTABLE nsResolveHostCallback : public PRCList
{
public:
/**
* OnLookupComplete
*
* this function is called to complete a host lookup initiated by
* nsHostResolver::ResolveHost. it may be invoked recursively from
* ResolveHost or on an unspecified background thread.
*
* NOTE: it is the responsibility of the implementor of this method
* to handle the callback in a thread safe manner.
*
* @param resolver
* nsHostResolver object associated with this result
* @param record
* the host record containing the results of the lookup
* @param status
* if successful, |record| contains non-null results
*/
virtual void OnLookupComplete(nsHostResolver *resolver,
nsHostRecord *record,
nsresult status) = 0;
};
/**
* nsHostResolver - an asynchronous host name resolver.
*/
class nsHostResolver
{
public:
/**
* host resolver instances are reference counted.
*/
NS_DECL_REFCOUNTED_THREADSAFE(nsHostResolver)
/**
* creates an addref'd instance of a nsHostResolver object.
*/
static nsresult Create(PRUint32 maxCacheEntries, // zero disables cache
PRUint32 maxCacheLifetime, // minutes
nsHostResolver **resolver);
/**
* puts the resolver in the shutdown state, which will cause any pending
* callbacks to be detached. any future calls to ResolveHost will fail.
*/
void Shutdown();
/**
* resolve the given hostname asynchronously. the caller can synthesize
* a synchronous host lookup using a lock and a cvar. as noted above
* the callback will occur re-entrantly from an unspecified thread. the
* host lookup cannot be canceled (cancelation can be layered above this
* by having the callback implementation return without doing anything).
*/
nsresult ResolveHost(const char *hostname,
PRUint16 flags,
PRUint16 af,
nsResolveHostCallback *callback);
/**
* removes the specified callback from the nsHostRecord for the given
* hostname, flags, and address family. these parameters should correspond
* to the parameters passed to ResolveHost. this function executes the
* callback if the callback is still pending with the given status.
*/
void DetachCallback(const char *hostname,
PRUint16 flags,
PRUint16 af,
nsResolveHostCallback *callback,
nsresult status);
/**
* values for the flags parameter passed to ResolveHost and DetachCallback
* that may be bitwise OR'd together.
*
* NOTE: in this implementation, these flags correspond exactly in value
* to the flags defined on nsIDNSService.
*/
enum {
RES_BYPASS_CACHE = 1 << 0,
RES_CANON_NAME = 1 << 1,
RES_PRIORITY_MEDIUM = 1 << 2,
RES_PRIORITY_LOW = 1 << 3,
RES_SPECULATE = 1 << 4
};
private:
nsHostResolver(PRUint32 maxCacheEntries=50, PRUint32 maxCacheLifetime=1);
~nsHostResolver();
nsresult Init();
nsresult IssueLookup(nsHostRecord *);
PRBool GetHostToLookup(nsHostRecord **m);
void OnLookupComplete(nsHostRecord *, nsresult, PRAddrInfo *);
void DeQueue(PRCList &aQ, nsHostRecord **aResult);
void ClearPendingQueue(PRCList *aPendingQueue);
nsresult ConditionallyCreateThread(nsHostRecord *rec);
static void MoveQueue(nsHostRecord *aRec, PRCList &aDestQ);
static void ThreadFunc(void *);
PRUint32 mMaxCacheEntries;
PRUint32 mMaxCacheLifetime;
PRLock *mLock;
PRCondVar *mIdleThreadCV; // non-null if idle thread
PRUint32 mNumIdleThreads;
PRUint32 mThreadCount;
PRUint32 mActiveAnyThreadCount;
PLDHashTable mDB;
PRCList mHighQ;
PRCList mMediumQ;
PRCList mLowQ;
PRCList mEvictionQ;
PRUint32 mEvictionQSize;
PRUint32 mPendingCount;
PRTime mCreationTime;
PRBool mShutdown;
PRIntervalTime mLongIdleTimeout;
PRIntervalTime mShortIdleTimeout;
};
#endif // nsHostResolver_h__