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gecko-dev/netwerk/dns/nsHostResolver.cpp
Ehsan Akhgari 8cc30b88b2 Bug 792502 - Kill the FunctionTimer code; r=vlad
2012-09-19 16:59:38 -04:00

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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/. */
#if defined(MOZ_LOGGING)
#define FORCE_PR_LOG
#endif
#if defined(HAVE_RES_NINIT)
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <resolv.h>
#define RES_RETRY_ON_FAILURE
#endif
#include <stdlib.h>
#include "nsHostResolver.h"
#include "nsError.h"
#include "nsISupportsBase.h"
#include "nsISupportsUtils.h"
#include "nsAutoPtr.h"
#include "pratom.h"
#include "prthread.h"
#include "prerror.h"
#include "prtime.h"
#include "prlong.h"
#include "prlog.h"
#include "pldhash.h"
#include "plstr.h"
#include "nsURLHelper.h"
#include "nsThreadUtils.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/Telemetry.h"
using namespace mozilla;
//----------------------------------------------------------------------------
// Use a persistent thread pool in order to avoid spinning up new threads all the time.
// In particular, thread creation results in a res_init() call from libc which is
// quite expensive.
//
// The pool dynamically grows between 0 and MAX_RESOLVER_THREADS in size. New requests
// go first to an idle thread. If that cannot be found and there are fewer than MAX_RESOLVER_THREADS
// currently in the pool a new thread is created for high priority requests. If
// the new request is at a lower priority a new thread will only be created if
// there are fewer than HighThreadThreshold currently outstanding. If a thread cannot be
// created or an idle thread located for the request it is queued.
//
// When the pool is greater than HighThreadThreshold in size a thread will be destroyed after
// ShortIdleTimeoutSeconds of idle time. Smaller pools use LongIdleTimeoutSeconds for a
// timeout period.
#define HighThreadThreshold MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY
#define LongIdleTimeoutSeconds 300 // for threads 1 -> HighThreadThreshold
#define ShortIdleTimeoutSeconds 60 // for threads HighThreadThreshold+1 -> MAX_RESOLVER_THREADS
PR_STATIC_ASSERT (HighThreadThreshold <= MAX_RESOLVER_THREADS);
//----------------------------------------------------------------------------
#if defined(PR_LOGGING)
static PRLogModuleInfo *gHostResolverLog = nullptr;
#define LOG(args) PR_LOG(gHostResolverLog, PR_LOG_DEBUG, args)
#else
#define LOG(args)
#endif
//----------------------------------------------------------------------------
static inline void
MoveCList(PRCList &from, PRCList &to)
{
if (!PR_CLIST_IS_EMPTY(&from)) {
to.next = from.next;
to.prev = from.prev;
to.next->prev = &to;
to.prev->next = &to;
PR_INIT_CLIST(&from);
}
}
static uint32_t
NowInMinutes()
{
PRTime now = PR_Now(), minutes, factor;
LL_I2L(factor, 60 * PR_USEC_PER_SEC);
LL_DIV(minutes, now, factor);
uint32_t result;
LL_L2UI(result, minutes);
return result;
}
//----------------------------------------------------------------------------
#if defined(RES_RETRY_ON_FAILURE)
// this class represents the resolver state for a given thread. if we
// encounter a lookup failure, then we can invoke the Reset method on an
// instance of this class to reset the resolver (in case /etc/resolv.conf
// for example changed). this is mainly an issue on GNU systems since glibc
// only reads in /etc/resolv.conf once per thread. it may be an issue on
// other systems as well.
class nsResState
{
public:
nsResState()
// initialize mLastReset to the time when this object
// is created. this means that a reset will not occur
// if a thread is too young. the alternative would be
// to initialize this to the beginning of time, so that
// the first failure would cause a reset, but since the
// thread would have just started up, it likely would
// already have current /etc/resolv.conf info.
: mLastReset(PR_IntervalNow())
{
}
bool Reset()
{
// reset no more than once per second
if (PR_IntervalToSeconds(PR_IntervalNow() - mLastReset) < 1)
return false;
LOG(("Calling 'res_ninit'.\n"));
mLastReset = PR_IntervalNow();
return (res_ninit(&_res) == 0);
}
private:
PRIntervalTime mLastReset;
};
#endif // RES_RETRY_ON_FAILURE
//----------------------------------------------------------------------------
// this macro filters out any flags that are not used when constructing the
// host key. the significant flags are those that would affect the resulting
// host record (i.e., the flags that are passed down to PR_GetAddrInfoByName).
#define RES_KEY_FLAGS(_f) ((_f) & nsHostResolver::RES_CANON_NAME)
nsHostRecord::nsHostRecord(const nsHostKey *key)
: addr_info_lock("nsHostRecord.addr_info_lock")
, addr_info_gencnt(0)
, addr_info(nullptr)
, addr(nullptr)
, negative(false)
, resolving(false)
, onQueue(false)
, usingAnyThread(false)
{
host = ((char *) this) + sizeof(nsHostRecord);
memcpy((char *) host, key->host, strlen(key->host) + 1);
flags = key->flags;
af = key->af;
expiration = NowInMinutes();
PR_INIT_CLIST(this);
PR_INIT_CLIST(&callbacks);
}
nsresult
nsHostRecord::Create(const nsHostKey *key, nsHostRecord **result)
{
size_t hostLen = strlen(key->host) + 1;
size_t size = hostLen + sizeof(nsHostRecord);
// Use placement new to create the object with room for the hostname
// allocated after it.
void *place = ::operator new(size);
*result = new(place) nsHostRecord(key);
NS_ADDREF(*result);
return NS_OK;
}
nsHostRecord::~nsHostRecord()
{
if (addr)
free(addr);
}
bool
nsHostRecord::Blacklisted(PRNetAddr *aQuery)
{
// must call locked
LOG(("Checking blacklist for host [%s], host record [%p].\n", host, this));
// skip the string conversion for the common case of no blacklist
if (!mBlacklistedItems.Length()) {
return false;
}
char buf[64];
if (PR_NetAddrToString(aQuery, buf, sizeof(buf)) != PR_SUCCESS) {
return false;
}
nsDependentCString strQuery(buf);
for (uint32_t i = 0; i < mBlacklistedItems.Length(); i++) {
if (mBlacklistedItems.ElementAt(i).Equals(strQuery)) {
LOG(("Address [%s] is blacklisted for host [%s].\n", buf, host));
return true;
}
}
return false;
}
void
nsHostRecord::ReportUnusable(PRNetAddr *aAddress)
{
// must call locked
LOG(("Adding address to blacklist for host [%s], host record [%p].\n", host, this));
char buf[64];
if (PR_NetAddrToString(aAddress, buf, sizeof(buf)) == PR_SUCCESS) {
LOG(("Successfully adding address [%s] to blacklist for host [%s].\n", buf, host));
mBlacklistedItems.AppendElement(nsCString(buf));
}
}
void
nsHostRecord::ResetBlacklist()
{
// must call locked
LOG(("Resetting blacklist for host [%s], host record [%p].\n", host, this));
mBlacklistedItems.Clear();
}
//----------------------------------------------------------------------------
struct nsHostDBEnt : PLDHashEntryHdr
{
nsHostRecord *rec;
};
static PLDHashNumber
HostDB_HashKey(PLDHashTable *table, const void *key)
{
const nsHostKey *hk = static_cast<const nsHostKey *>(key);
return AddToHash(HashString(hk->host), RES_KEY_FLAGS(hk->flags), hk->af);
}
static bool
HostDB_MatchEntry(PLDHashTable *table,
const PLDHashEntryHdr *entry,
const void *key)
{
const nsHostDBEnt *he = static_cast<const nsHostDBEnt *>(entry);
const nsHostKey *hk = static_cast<const nsHostKey *>(key);
return !strcmp(he->rec->host, hk->host) &&
RES_KEY_FLAGS (he->rec->flags) == RES_KEY_FLAGS(hk->flags) &&
he->rec->af == hk->af;
}
static void
HostDB_MoveEntry(PLDHashTable *table,
const PLDHashEntryHdr *from,
PLDHashEntryHdr *to)
{
static_cast<nsHostDBEnt *>(to)->rec =
static_cast<const nsHostDBEnt *>(from)->rec;
}
static void
HostDB_ClearEntry(PLDHashTable *table,
PLDHashEntryHdr *entry)
{
nsHostDBEnt *he = static_cast<nsHostDBEnt *>(entry);
LOG(("Clearing cache db entry for host [%s].\n", he->rec->host));
#if defined(DEBUG) && defined(PR_LOGGING)
if (!he->rec->addr_info) {
LOG(("No address info for host [%s].\n", he->rec->host));
} else {
int32_t now = (int32_t) NowInMinutes();
int32_t diff = (int32_t) he->rec->expiration - now;
LOG(("Record for [%s] expires in %d minute(s).\n", he->rec->host, diff));
void *iter = nullptr;
PRNetAddr addr;
char buf[64];
for (;;) {
iter = PR_EnumerateAddrInfo(iter, he->rec->addr_info, 0, &addr);
if (!iter)
break;
PR_NetAddrToString(&addr, buf, sizeof(buf));
LOG((" [%s]\n", buf));
}
}
#endif
NS_RELEASE(he->rec);
}
static bool
HostDB_InitEntry(PLDHashTable *table,
PLDHashEntryHdr *entry,
const void *key)
{
nsHostDBEnt *he = static_cast<nsHostDBEnt *>(entry);
nsHostRecord::Create(static_cast<const nsHostKey *>(key), &he->rec);
return true;
}
static PLDHashTableOps gHostDB_ops =
{
PL_DHashAllocTable,
PL_DHashFreeTable,
HostDB_HashKey,
HostDB_MatchEntry,
HostDB_MoveEntry,
HostDB_ClearEntry,
PL_DHashFinalizeStub,
HostDB_InitEntry,
};
static PLDHashOperator
HostDB_RemoveEntry(PLDHashTable *table,
PLDHashEntryHdr *hdr,
uint32_t number,
void *arg)
{
return PL_DHASH_REMOVE;
}
//----------------------------------------------------------------------------
nsHostResolver::nsHostResolver(uint32_t maxCacheEntries,
uint32_t maxCacheLifetime,
uint32_t lifetimeGracePeriod)
: mMaxCacheEntries(maxCacheEntries)
, mMaxCacheLifetime(maxCacheLifetime)
, mGracePeriod(lifetimeGracePeriod)
, mLock("nsHostResolver.mLock")
, mIdleThreadCV(mLock, "nsHostResolver.mIdleThreadCV")
, mNumIdleThreads(0)
, mThreadCount(0)
, mActiveAnyThreadCount(0)
, mEvictionQSize(0)
, mPendingCount(0)
, mShutdown(true)
{
mCreationTime = PR_Now();
PR_INIT_CLIST(&mHighQ);
PR_INIT_CLIST(&mMediumQ);
PR_INIT_CLIST(&mLowQ);
PR_INIT_CLIST(&mEvictionQ);
mLongIdleTimeout = PR_SecondsToInterval(LongIdleTimeoutSeconds);
mShortIdleTimeout = PR_SecondsToInterval(ShortIdleTimeoutSeconds);
}
nsHostResolver::~nsHostResolver()
{
PL_DHashTableFinish(&mDB);
}
nsresult
nsHostResolver::Init()
{
PL_DHashTableInit(&mDB, &gHostDB_ops, nullptr, sizeof(nsHostDBEnt), 0);
mShutdown = false;
#if defined(HAVE_RES_NINIT)
// We want to make sure the system is using the correct resolver settings,
// so we force it to reload those settings whenever we startup a subsequent
// nsHostResolver instance. We assume that there is no reason to do this
// for the first nsHostResolver instance since that is usually created
// during application startup.
static int initCount = 0;
if (initCount++ > 0) {
LOG(("Calling 'res_ninit'.\n"));
res_ninit(&_res);
}
#endif
return NS_OK;
}
void
nsHostResolver::ClearPendingQueue(PRCList *aPendingQ)
{
// loop through pending queue, erroring out pending lookups.
if (!PR_CLIST_IS_EMPTY(aPendingQ)) {
PRCList *node = aPendingQ->next;
while (node != aPendingQ) {
nsHostRecord *rec = static_cast<nsHostRecord *>(node);
node = node->next;
OnLookupComplete(rec, NS_ERROR_ABORT, nullptr);
}
}
}
void
nsHostResolver::Shutdown()
{
LOG(("Shutting down host resolver.\n"));
PRCList pendingQHigh, pendingQMed, pendingQLow, evictionQ;
PR_INIT_CLIST(&pendingQHigh);
PR_INIT_CLIST(&pendingQMed);
PR_INIT_CLIST(&pendingQLow);
PR_INIT_CLIST(&evictionQ);
{
MutexAutoLock lock(mLock);
mShutdown = true;
MoveCList(mHighQ, pendingQHigh);
MoveCList(mMediumQ, pendingQMed);
MoveCList(mLowQ, pendingQLow);
MoveCList(mEvictionQ, evictionQ);
mEvictionQSize = 0;
mPendingCount = 0;
if (mNumIdleThreads)
mIdleThreadCV.NotifyAll();
// empty host database
PL_DHashTableEnumerate(&mDB, HostDB_RemoveEntry, nullptr);
}
ClearPendingQueue(&pendingQHigh);
ClearPendingQueue(&pendingQMed);
ClearPendingQueue(&pendingQLow);
if (!PR_CLIST_IS_EMPTY(&evictionQ)) {
PRCList *node = evictionQ.next;
while (node != &evictionQ) {
nsHostRecord *rec = static_cast<nsHostRecord *>(node);
node = node->next;
NS_RELEASE(rec);
}
}
#ifdef NS_BUILD_REFCNT_LOGGING
// Logically join the outstanding worker threads with a timeout.
// Use this approach instead of PR_JoinThread() because that does
// not allow a timeout which may be necessary for a semi-responsive
// shutdown if the thread is blocked on a very slow DNS resolution.
// mThreadCount is read outside of mLock, but the worst case
// scenario for that race is one extra 25ms sleep.
PRIntervalTime delay = PR_MillisecondsToInterval(25);
PRIntervalTime stopTime = PR_IntervalNow() + PR_SecondsToInterval(20);
while (mThreadCount && PR_IntervalNow() < stopTime)
PR_Sleep(delay);
#endif
}
static inline bool
IsHighPriority(uint16_t flags)
{
return !(flags & (nsHostResolver::RES_PRIORITY_LOW | nsHostResolver::RES_PRIORITY_MEDIUM));
}
static inline bool
IsMediumPriority(uint16_t flags)
{
return flags & nsHostResolver::RES_PRIORITY_MEDIUM;
}
static inline bool
IsLowPriority(uint16_t flags)
{
return flags & nsHostResolver::RES_PRIORITY_LOW;
}
void
nsHostResolver::MoveQueue(nsHostRecord *aRec, PRCList &aDestQ)
{
NS_ASSERTION(aRec->onQueue, "Moving Host Record Not Currently Queued");
PR_REMOVE_LINK(aRec);
PR_APPEND_LINK(aRec, &aDestQ);
}
nsresult
nsHostResolver::ResolveHost(const char *host,
uint16_t flags,
uint16_t af,
nsResolveHostCallback *callback)
{
NS_ENSURE_TRUE(host && *host, NS_ERROR_UNEXPECTED);
LOG(("Resolving host [%s].\n", host));
// ensure that we are working with a valid hostname before proceeding. see
// bug 304904 for details.
if (!net_IsValidHostName(nsDependentCString(host)))
return NS_ERROR_UNKNOWN_HOST;
// if result is set inside the lock, then we need to issue the
// callback before returning.
nsRefPtr<nsHostRecord> result;
nsresult status = NS_OK, rv = NS_OK;
{
MutexAutoLock lock(mLock);
if (mShutdown)
rv = NS_ERROR_NOT_INITIALIZED;
else {
PRNetAddr tempAddr;
// unfortunately, PR_StringToNetAddr does not properly initialize
// the output buffer in the case of IPv6 input. see bug 223145.
memset(&tempAddr, 0, sizeof(PRNetAddr));
// check to see if there is already an entry for this |host|
// in the hash table. if so, then check to see if we can't
// just reuse the lookup result. otherwise, if there are
// any pending callbacks, then add to pending callbacks queue,
// and return. otherwise, add ourselves as first pending
// callback, and proceed to do the lookup.
nsHostKey key = { host, flags, af };
nsHostDBEnt *he = static_cast<nsHostDBEnt *>
(PL_DHashTableOperate(&mDB, &key, PL_DHASH_ADD));
// if the record is null, then HostDB_InitEntry failed.
if (!he || !he->rec)
rv = NS_ERROR_OUT_OF_MEMORY;
// do we have a cached result that we can reuse?
else if (!(flags & RES_BYPASS_CACHE) &&
he->rec->HasResult() &&
NowInMinutes() <= he->rec->expiration + mGracePeriod) {
LOG(("Using cached record for host [%s].\n", host));
// put reference to host record on stack...
result = he->rec;
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2, METHOD_HIT);
// For entries that are in the grace period, or all cached
// negative entries, use the cache but start a new lookup in
// the background
if (((NowInMinutes() > he->rec->expiration) ||
he->rec->negative) && !he->rec->resolving) {
LOG(("Using %s cache entry for host [%s] but starting async renewal.",
he->rec->negative ? "negative" :"positive", host));
IssueLookup(he->rec);
if (!he->rec->negative) {
// negative entries are constantly being refreshed, only
// track positive grace period induced renewals
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2,
METHOD_RENEWAL);
}
}
if (he->rec->negative) {
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2,
METHOD_NEGATIVE_HIT);
status = NS_ERROR_UNKNOWN_HOST;
}
}
// if the host name is an IP address literal and has been parsed,
// go ahead and use it.
else if (he->rec->addr) {
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2,
METHOD_LITERAL);
result = he->rec;
}
// try parsing the host name as an IP address literal to short
// circuit full host resolution. (this is necessary on some
// platforms like Win9x. see bug 219376 for more details.)
else if (PR_StringToNetAddr(host, &tempAddr) == PR_SUCCESS) {
// ok, just copy the result into the host record, and be done
// with it! ;-)
he->rec->addr = (PRNetAddr *) malloc(sizeof(PRNetAddr));
if (!he->rec->addr)
status = NS_ERROR_OUT_OF_MEMORY;
else
memcpy(he->rec->addr, &tempAddr, sizeof(PRNetAddr));
// put reference to host record on stack...
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2,
METHOD_LITERAL);
result = he->rec;
}
else if (mPendingCount >= MAX_NON_PRIORITY_REQUESTS &&
!IsHighPriority(flags) &&
!he->rec->resolving) {
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2,
METHOD_OVERFLOW);
// This is a lower priority request and we are swamped, so refuse it.
rv = NS_ERROR_DNS_LOOKUP_QUEUE_FULL;
}
else if (flags & RES_OFFLINE) {
rv = NS_ERROR_OFFLINE;
}
// otherwise, hit the resolver...
else {
// Add callback to the list of pending callbacks.
PR_APPEND_LINK(callback, &he->rec->callbacks);
if (!he->rec->resolving) {
he->rec->flags = flags;
rv = IssueLookup(he->rec);
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2,
METHOD_NETWORK_FIRST);
if (NS_FAILED(rv))
PR_REMOVE_AND_INIT_LINK(callback);
else
LOG(("DNS lookup for host [%s] blocking pending 'getaddrinfo' query.", host));
}
else if (he->rec->onQueue) {
Telemetry::Accumulate(Telemetry::DNS_LOOKUP_METHOD2,
METHOD_NETWORK_SHARED);
// Consider the case where we are on a pending queue of
// lower priority than the request is being made at.
// In that case we should upgrade to the higher queue.
if (IsHighPriority(flags) && !IsHighPriority(he->rec->flags)) {
// Move from (low|med) to high.
MoveQueue(he->rec, mHighQ);
he->rec->flags = flags;
ConditionallyCreateThread(he->rec);
} else if (IsMediumPriority(flags) && IsLowPriority(he->rec->flags)) {
// Move from low to med.
MoveQueue(he->rec, mMediumQ);
he->rec->flags = flags;
mIdleThreadCV.Notify();
}
}
}
}
}
if (result)
callback->OnLookupComplete(this, result, status);
return rv;
}
void
nsHostResolver::DetachCallback(const char *host,
uint16_t flags,
uint16_t af,
nsResolveHostCallback *callback,
nsresult status)
{
nsRefPtr<nsHostRecord> rec;
{
MutexAutoLock lock(mLock);
nsHostKey key = { host, flags, af };
nsHostDBEnt *he = static_cast<nsHostDBEnt *>
(PL_DHashTableOperate(&mDB, &key, PL_DHASH_LOOKUP));
if (he && he->rec) {
// walk list looking for |callback|... we cannot assume
// that it will be there!
PRCList *node = he->rec->callbacks.next;
while (node != &he->rec->callbacks) {
if (static_cast<nsResolveHostCallback *>(node) == callback) {
PR_REMOVE_LINK(callback);
rec = he->rec;
break;
}
node = node->next;
}
}
}
// complete callback with the given status code; this would only be done if
// the record was in the process of being resolved.
if (rec)
callback->OnLookupComplete(this, rec, status);
}
nsresult
nsHostResolver::ConditionallyCreateThread(nsHostRecord *rec)
{
if (mNumIdleThreads) {
// wake up idle thread to process this lookup
mIdleThreadCV.Notify();
}
else if ((mThreadCount < HighThreadThreshold) ||
(IsHighPriority(rec->flags) && mThreadCount < MAX_RESOLVER_THREADS)) {
// dispatch new worker thread
NS_ADDREF_THIS(); // owning reference passed to thread
mThreadCount++;
PRThread *thr = PR_CreateThread(PR_SYSTEM_THREAD,
ThreadFunc,
this,
PR_PRIORITY_NORMAL,
PR_GLOBAL_THREAD,
PR_UNJOINABLE_THREAD,
0);
if (!thr) {
mThreadCount--;
NS_RELEASE_THIS();
return NS_ERROR_OUT_OF_MEMORY;
}
}
#if defined(PR_LOGGING)
else
LOG(("Unable to find a thread for looking up host [%s].\n", rec->host));
#endif
return NS_OK;
}
nsresult
nsHostResolver::IssueLookup(nsHostRecord *rec)
{
nsresult rv = NS_OK;
NS_ASSERTION(!rec->resolving, "record is already being resolved");
// Add rec to one of the pending queues, possibly removing it from mEvictionQ.
// If rec is on mEvictionQ, then we can just move the owning
// reference over to the new active queue.
if (rec->next == rec)
NS_ADDREF(rec);
else {
PR_REMOVE_LINK(rec);
mEvictionQSize--;
}
if (IsHighPriority(rec->flags))
PR_APPEND_LINK(rec, &mHighQ);
else if (IsMediumPriority(rec->flags))
PR_APPEND_LINK(rec, &mMediumQ);
else
PR_APPEND_LINK(rec, &mLowQ);
mPendingCount++;
rec->resolving = true;
rec->onQueue = true;
rv = ConditionallyCreateThread(rec);
LOG (("DNS thread counters: total=%d any-live=%d idle=%d pending=%d\n",
mThreadCount,
mActiveAnyThreadCount,
mNumIdleThreads,
mPendingCount));
return rv;
}
void
nsHostResolver::DeQueue(PRCList &aQ, nsHostRecord **aResult)
{
*aResult = static_cast<nsHostRecord *>(aQ.next);
PR_REMOVE_AND_INIT_LINK(*aResult);
mPendingCount--;
(*aResult)->onQueue = false;
}
bool
nsHostResolver::GetHostToLookup(nsHostRecord **result)
{
bool timedOut = false;
PRIntervalTime epoch, now, timeout;
MutexAutoLock lock(mLock);
timeout = (mNumIdleThreads >= HighThreadThreshold) ? mShortIdleTimeout : mLongIdleTimeout;
epoch = PR_IntervalNow();
while (!mShutdown) {
// remove next record from Q; hand over owning reference. Check high, then med, then low
if (!PR_CLIST_IS_EMPTY(&mHighQ)) {
DeQueue (mHighQ, result);
return true;
}
if (mActiveAnyThreadCount < HighThreadThreshold) {
if (!PR_CLIST_IS_EMPTY(&mMediumQ)) {
DeQueue (mMediumQ, result);
mActiveAnyThreadCount++;
(*result)->usingAnyThread = true;
return true;
}
if (!PR_CLIST_IS_EMPTY(&mLowQ)) {
DeQueue (mLowQ, result);
mActiveAnyThreadCount++;
(*result)->usingAnyThread = true;
return true;
}
}
// Determining timeout is racy, so allow one cycle through checking the queues
// before exiting.
if (timedOut)
break;
// wait for one or more of the following to occur:
// (1) the pending queue has a host record to process
// (2) the shutdown flag has been set
// (3) the thread has been idle for too long
mNumIdleThreads++;
mIdleThreadCV.Wait(timeout);
mNumIdleThreads--;
now = PR_IntervalNow();
if ((PRIntervalTime)(now - epoch) >= timeout)
timedOut = true;
else {
// It is possible that PR_WaitCondVar() was interrupted and returned early,
// in which case we will loop back and re-enter it. In that case we want to
// do so with the new timeout reduced to reflect time already spent waiting.
timeout -= (PRIntervalTime)(now - epoch);
epoch = now;
}
}
// tell thread to exit...
mThreadCount--;
return false;
}
void
nsHostResolver::OnLookupComplete(nsHostRecord *rec, nsresult status, PRAddrInfo *result)
{
// get the list of pending callbacks for this lookup, and notify
// them that the lookup is complete.
PRCList cbs;
PR_INIT_CLIST(&cbs);
{
MutexAutoLock lock(mLock);
// grab list of callbacks to notify
MoveCList(rec->callbacks, cbs);
// update record fields. We might have a rec->addr_info already if a
// previous lookup result expired and we're reresolving it..
PRAddrInfo *old_addr_info;
{
MutexAutoLock lock(rec->addr_info_lock);
old_addr_info = rec->addr_info;
rec->addr_info = result;
rec->addr_info_gencnt++;
}
if (old_addr_info)
PR_FreeAddrInfo(old_addr_info);
rec->expiration = NowInMinutes();
if (result) {
rec->expiration += mMaxCacheLifetime;
rec->negative = false;
}
else {
rec->expiration += 1; /* one minute for negative cache */
rec->negative = true;
}
rec->resolving = false;
if (rec->usingAnyThread) {
mActiveAnyThreadCount--;
rec->usingAnyThread = false;
}
if (rec->addr_info && !mShutdown) {
// add to mEvictionQ
PR_APPEND_LINK(rec, &mEvictionQ);
NS_ADDREF(rec);
if (mEvictionQSize < mMaxCacheEntries)
mEvictionQSize++;
else {
// remove first element on mEvictionQ
nsHostRecord *head =
static_cast<nsHostRecord *>(PR_LIST_HEAD(&mEvictionQ));
PR_REMOVE_AND_INIT_LINK(head);
PL_DHashTableOperate(&mDB, (nsHostKey *) head, PL_DHASH_REMOVE);
if (!head->negative) {
// record the age of the entry upon eviction.
uint32_t age =
NowInMinutes() - (head->expiration - mMaxCacheLifetime);
Telemetry::Accumulate(Telemetry::DNS_CLEANUP_AGE, age);
}
// release reference to rec owned by mEvictionQ
NS_RELEASE(head);
}
}
}
if (!PR_CLIST_IS_EMPTY(&cbs)) {
PRCList *node = cbs.next;
while (node != &cbs) {
nsResolveHostCallback *callback =
static_cast<nsResolveHostCallback *>(node);
node = node->next;
callback->OnLookupComplete(this, rec, status);
// NOTE: callback must not be dereferenced after this point!!
}
}
NS_RELEASE(rec);
}
void
nsHostResolver::CancelAsyncRequest(const char *host,
uint16_t flags,
uint16_t af,
nsIDNSListener *aListener,
nsresult status)
{
MutexAutoLock lock(mLock);
// Lookup the host record associated with host, flags & address family
nsHostKey key = { host, flags, af };
nsHostDBEnt *he = static_cast<nsHostDBEnt *>
(PL_DHashTableOperate(&mDB, &key, PL_DHASH_LOOKUP));
if (he && he->rec) {
nsHostRecord* recPtr = NULL;
PRCList *node = he->rec->callbacks.next;
// Remove the first nsDNSAsyncRequest callback which matches the
// supplied listener object
while (node != &he->rec->callbacks) {
nsResolveHostCallback *callback
= static_cast<nsResolveHostCallback *>(node);
if (callback && (callback->EqualsAsyncListener(aListener))) {
// Remove from the list of callbacks
PR_REMOVE_LINK(callback);
recPtr = he->rec;
callback->OnLookupComplete(this, recPtr, status);
break;
}
node = node->next;
}
// If there are no more callbacks, remove the hash table entry
if (recPtr && PR_CLIST_IS_EMPTY(&recPtr->callbacks)) {
PL_DHashTableOperate(&mDB, (nsHostKey *)recPtr, PL_DHASH_REMOVE);
// If record is on a Queue, remove it and then deref it
if (recPtr->next != recPtr) {
PR_REMOVE_LINK(recPtr);
NS_RELEASE(recPtr);
}
}
}
}
//----------------------------------------------------------------------------
void
nsHostResolver::ThreadFunc(void *arg)
{
LOG(("DNS lookup thread starting execution.\n"));
static nsThreadPoolNaming naming;
naming.SetThreadPoolName(NS_LITERAL_CSTRING("DNS Resolver"));
#if defined(RES_RETRY_ON_FAILURE)
nsResState rs;
#endif
nsHostResolver *resolver = (nsHostResolver *)arg;
nsHostRecord *rec;
PRAddrInfo *ai;
while (resolver->GetHostToLookup(&rec)) {
LOG(("Calling getaddrinfo for host [%s].\n", rec->host));
int flags = PR_AI_ADDRCONFIG;
if (!(rec->flags & RES_CANON_NAME))
flags |= PR_AI_NOCANONNAME;
TimeStamp startTime = TimeStamp::Now();
ai = PR_GetAddrInfoByName(rec->host, rec->af, flags);
#if defined(RES_RETRY_ON_FAILURE)
if (!ai && rs.Reset())
ai = PR_GetAddrInfoByName(rec->host, rec->af, flags);
#endif
TimeDuration elapsed = TimeStamp::Now() - startTime;
uint32_t millis = static_cast<uint32_t>(elapsed.ToMilliseconds());
// convert error code to nsresult.
nsresult status;
if (ai) {
status = NS_OK;
Telemetry::Accumulate(!rec->addr_info_gencnt ?
Telemetry::DNS_LOOKUP_TIME :
Telemetry::DNS_RENEWAL_TIME,
millis);
}
else {
status = NS_ERROR_UNKNOWN_HOST;
Telemetry::Accumulate(Telemetry::DNS_FAILED_LOOKUP_TIME, millis);
}
resolver->OnLookupComplete(rec, status, ai);
LOG(("Lookup completed for host [%s].\n", rec->host));
}
NS_RELEASE(resolver);
LOG(("DNS lookup thread ending execution.\n"));
}
//----------------------------------------------------------------------------
nsresult
nsHostResolver::Create(uint32_t maxCacheEntries,
uint32_t maxCacheLifetime,
uint32_t lifetimeGracePeriod,
nsHostResolver **result)
{
#if defined(PR_LOGGING)
if (!gHostResolverLog)
gHostResolverLog = PR_NewLogModule("nsHostResolver");
#endif
nsHostResolver *res = new nsHostResolver(maxCacheEntries,
maxCacheLifetime,
lifetimeGracePeriod);
if (!res)
return NS_ERROR_OUT_OF_MEMORY;
NS_ADDREF(res);
nsresult rv = res->Init();
if (NS_FAILED(rv))
NS_RELEASE(res);
*result = res;
return rv;
}
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