gecko-dev/netwerk/dns/nsHostResolver.h

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/* vim:set ts=4 sw=4 sts=4 et cin: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef nsHostResolver_h__
#define nsHostResolver_h__
#include "nscore.h"
#include "prclist.h"
#include "prnetdb.h"
#include "pldhash.h"
#include "mozilla/CondVar.h"
#include "mozilla/Mutex.h"
#include "nsISupportsImpl.h"
#include "nsIDNSListener.h"
#include "nsString.h"
#include "nsTArray.h"
#include "GetAddrInfo.h"
#include "mozilla/net/DNS.h"
#include "mozilla/net/DashboardTypes.h"
#include "mozilla/TimeStamp.h"
class nsHostResolver;
class nsHostRecord;
class nsResolveHostCallback;
#define MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY 3
#define MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY 5
#define MAX_NON_PRIORITY_REQUESTS 150
#define MAX_RESOLVER_THREADS (MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY + \
MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY)
struct nsHostKey
{
const char *host;
uint16_t flags;
uint16_t af;
};
/**
* nsHostRecord - ref counted object type stored in host resolver cache.
*/
class nsHostRecord : public PRCList, public nsHostKey
{
typedef mozilla::Mutex Mutex;
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(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|.
*/
Mutex addr_info_lock;
int addr_info_gencnt; /* generation count of |addr_info| */
mozilla::net::AddrInfo *addr_info;
mozilla::net::NetAddr *addr;
bool 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. */
enum ExpirationStatus {
EXP_VALID,
EXP_GRACE,
EXP_EXPIRED,
};
ExpirationStatus CheckExpiration(const mozilla::TimeStamp& now) const;
// When the record began being valid. Used mainly for bookkeeping.
mozilla::TimeStamp mValidStart;
// When the record is no longer valid (it's time of expiration)
mozilla::TimeStamp mValidEnd;
// When the record enters its grace period. This must be before mValidEnd.
// If a record is in its grace period (and not expired), it will be used
// but a request to refresh it will be made.
mozilla::TimeStamp mGraceStart;
// Convenience function for setting the timestamps above (mValidStart,
// mValidEnd, and mGraceStart). valid and grace are durations in seconds.
void SetExpiration(const mozilla::TimeStamp& now, unsigned int valid,
unsigned int grace);
// Checks if the record is usable (not expired and has a value)
bool HasUsableResult(const mozilla::TimeStamp& now, uint16_t queryFlags = 0) const;
// hold addr_info_lock when calling the blacklist functions
bool Blacklisted(mozilla::net::NetAddr *query);
void ResetBlacklist();
void ReportUnusable(mozilla::net::NetAddr *addr);
size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
enum DnsPriority {
DNS_PRIORITY_LOW,
DNS_PRIORITY_MEDIUM,
DNS_PRIORITY_HIGH,
};
static DnsPriority GetPriority(uint16_t aFlags);
bool RemoveOrRefresh(); // Mark records currently being resolved as needed
// to resolve again.
private:
friend class nsHostResolver;
PRCList callbacks; /* list of callbacks */
bool 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. */
bool onQueue; /* true if pending and on the queue (not yet given to getaddrinfo())*/
bool usingAnyThread; /* true if off queue and contributing to mActiveAnyThreadCount */
bool mDoomed; /* explicitly expired */
#if TTL_AVAILABLE
bool mGetTtl;
#endif
// The number of times ReportUnusable() has been called in the record's
// lifetime.
uint32_t mBlacklistedCount;
// when the results from this resolve is returned, it is not to be
// trusted, but instead a new resolve must be made!
bool mResolveAgain;
// a list of addresses associated with this record that have been reported
// as unusable. the list is kept as a set of strings to make it independent
// of gencnt.
nsTArray<nsCString> mBlacklistedItems;
explicit nsHostRecord(const nsHostKey *key); /* use Create() instead */
~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;
/**
* EqualsAsyncListener
*
* Determines if the listener argument matches the listener member var.
* For subclasses not implementing a member listener, should return false.
* For subclasses having a member listener, the function should check if
* they are the same. Used for cases where a pointer to an object
* implementing nsResolveHostCallback is unknown, but a pointer to
* the original listener is known.
*
* @param aListener
* nsIDNSListener object associated with the original request
*/
virtual bool EqualsAsyncListener(nsIDNSListener *aListener) = 0;
virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf) const = 0;
};
/**
* nsHostResolver - an asynchronous host name resolver.
*/
class nsHostResolver
{
typedef mozilla::CondVar CondVar;
typedef mozilla::Mutex Mutex;
public:
/**
* host resolver instances are reference counted.
*/
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(nsHostResolver)
/**
* creates an addref'd instance of a nsHostResolver object.
*/
static nsresult Create(uint32_t maxCacheEntries, // zero disables cache
uint32_t defaultCacheEntryLifetime, // seconds
uint32_t defaultGracePeriod, // seconds
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,
uint16_t flags,
uint16_t 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,
uint16_t flags,
uint16_t af,
nsResolveHostCallback *callback,
nsresult status);
/**
* Cancels an async request associated with the hostname, flags,
* address family and listener. Cancels first callback found which matches
* these criteria. These parameters should correspond to the parameters
* passed to ResolveHost. If this is the last callback associated with the
* host record, it is removed from any request queues it might be on.
*/
void CancelAsyncRequest(const char *host,
uint16_t flags,
uint16_t af,
nsIDNSListener *aListener,
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,
//RES_DISABLE_IPV6 = 1 << 5, // Not used
RES_OFFLINE = 1 << 6
};
size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
/**
* Flush the DNS cache.
*/
void FlushCache();
private:
explicit nsHostResolver(uint32_t maxCacheEntries,
uint32_t defaultCacheEntryLifetime,
uint32_t defaultGracePeriod);
~nsHostResolver();
nsresult Init();
nsresult IssueLookup(nsHostRecord *);
bool GetHostToLookup(nsHostRecord **m);
enum LookupStatus {
LOOKUP_OK,
LOOKUP_RESOLVEAGAIN,
};
LookupStatus OnLookupComplete(nsHostRecord *, nsresult, mozilla::net::AddrInfo *);
void DeQueue(PRCList &aQ, nsHostRecord **aResult);
void ClearPendingQueue(PRCList *aPendingQueue);
nsresult ConditionallyCreateThread(nsHostRecord *rec);
/**
* Starts a new lookup in the background for entries that are in the grace
* period with a failed connect or all cached entries are negative.
*/
nsresult ConditionallyRefreshRecord(nsHostRecord *rec, const char *host);
static void MoveQueue(nsHostRecord *aRec, PRCList &aDestQ);
static void ThreadFunc(void *);
enum {
METHOD_HIT = 1,
METHOD_RENEWAL = 2,
METHOD_NEGATIVE_HIT = 3,
METHOD_LITERAL = 4,
METHOD_OVERFLOW = 5,
METHOD_NETWORK_FIRST = 6,
METHOD_NETWORK_SHARED = 7
};
uint32_t mMaxCacheEntries;
uint32_t mDefaultCacheLifetime; // granularity seconds
uint32_t mDefaultGracePeriod; // granularity seconds
mutable Mutex mLock; // mutable so SizeOfIncludingThis can be const
CondVar mIdleThreadCV;
uint32_t mNumIdleThreads;
uint32_t mThreadCount;
uint32_t mActiveAnyThreadCount;
PLDHashTable mDB;
PRCList mHighQ;
PRCList mMediumQ;
PRCList mLowQ;
PRCList mEvictionQ;
uint32_t mEvictionQSize;
uint32_t mPendingCount;
PRTime mCreationTime;
bool mShutdown;
PRIntervalTime mLongIdleTimeout;
PRIntervalTime mShortIdleTimeout;
// Set the expiration time stamps appropriately.
void PrepareRecordExpiration(nsHostRecord* rec) const;
public:
/*
* Called by the networking dashboard via the DnsService2
*/
void GetDNSCacheEntries(nsTArray<mozilla::net::DNSCacheEntries> *);
};
#endif // nsHostResolver_h__