/* * Copyright (C) 2008 Collin Jackson <collinj@webkit.org> * Copyright (C) 2009 Apple Inc. All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "config.h" #include "DNS.h" #include "StringHash.h" #include "Timer.h" #include <wtf/HashSet.h> #include <wtf/RetainPtr.h> #include <wtf/StdLibExtras.h> #include <CFNetwork/CFNetwork.h> #if PLATFORM(WIN) #include "LoaderRunLoopCF.h" #endif #ifdef BUILDING_ON_TIGER // This function is available on Tiger, but not declared in the CFRunLoop.h header on Tiger. extern "C" CFRunLoopRef CFRunLoopGetMain(); #endif namespace WebCore { // When resolve queue is empty, we fire async resolution requests immediately (which is important if the prefetch is triggered by hovering). // But during page parsing, we should coalesce identical requests to avoid stressing out CFHost. const int namesToResolveImmediately = 4; // Coalesce prefetch requests for this long before sending them out. const double coalesceDelayInSeconds = 1.0; // Sending many DNS requests at once can overwhelm some gateways. CFHost doesn't currently throttle for us, see <rdar://8105550>. const int maxSimultaneousRequests = 8; // For a page has links to many outside sites, it is likely that the system DNS resolver won't be able to cache them all anyway, and we don't want // to negatively affect other applications' performance by pushing their cached entries out. // If we end up with lots of names to prefetch, some will be dropped. const int maxRequestsToQueue = 64; // If there were queued names that couldn't be sent simultaneously, check the state of resolvers after this delay. const double retryResolvingInSeconds = 0.1; class DNSResolveQueue : public TimerBase { public: static DNSResolveQueue& shared(); void add(const String&); void decrementRequestCount(); private: DNSResolveQueue(); void resolve(const String&); virtual void fired(); HashSet<String> m_names; int m_requestsInFlight; }; DNSResolveQueue::DNSResolveQueue() : m_requestsInFlight(0) { } DNSResolveQueue& DNSResolveQueue::shared() { DEFINE_STATIC_LOCAL(DNSResolveQueue, names, ()); return names; } void DNSResolveQueue::add(const String& name) { // If there are no names queued, and few enough are in flight, resolve immediately (the mouse may be over a link). if (!m_names.size()) { if (atomicIncrement(&m_requestsInFlight) <= namesToResolveImmediately) { resolve(name); return; } atomicDecrement(&m_requestsInFlight); } // It's better to not prefetch some names than to clog the queue. // Dropping the newest names, because on a single page, these are likely to be below oldest ones. if (m_names.size() < maxRequestsToQueue) { m_names.add(name); if (!isActive()) startOneShot(coalesceDelayInSeconds); } } void DNSResolveQueue::decrementRequestCount() { atomicDecrement(&m_requestsInFlight); } void DNSResolveQueue::fired() { int requestsAllowed = maxSimultaneousRequests - m_requestsInFlight; for (; !m_names.isEmpty() && requestsAllowed > 0; --requestsAllowed) { atomicIncrement(&m_requestsInFlight); HashSet<String>::iterator currentName = m_names.begin(); resolve(*currentName); m_names.remove(currentName); } if (!m_names.isEmpty()) startOneShot(retryResolvingInSeconds); } static void clientCallback(CFHostRef theHost, CFHostInfoType, const CFStreamError*, void*) { DNSResolveQueue::shared().decrementRequestCount(); // It's ok to call shared() from a secondary thread, the static variable has already been initialized by now. CFRelease(theHost); } void DNSResolveQueue::resolve(const String& hostname) { ASSERT(isMainThread() || pthread_main_np()); RetainPtr<CFStringRef> hostnameCF(AdoptCF, hostname.createCFString()); RetainPtr<CFHostRef> host(AdoptCF, CFHostCreateWithName(0, hostnameCF.get())); if (!host) { atomicDecrement(&m_requestsInFlight); return; } CFHostClientContext context = { 0, 0, 0, 0, 0 }; Boolean result = CFHostSetClient(host.get(), clientCallback, &context); ASSERT_UNUSED(result, result); #if !PLATFORM(WIN) CFHostScheduleWithRunLoop(host.get(), CFRunLoopGetMain(), kCFRunLoopCommonModes); #else // On Windows, we run a separate thread with CFRunLoop, which is where clientCallback will be called. CFHostScheduleWithRunLoop(host.get(), loaderRunLoop(), kCFRunLoopDefaultMode); #endif CFHostStartInfoResolution(host.get(), kCFHostAddresses, 0); host.releaseRef(); // The host will be released from clientCallback(). } void prefetchDNS(const String& hostname) { ASSERT(isMainThread() || pthread_main_np()); if (hostname.isEmpty()) return; DNSResolveQueue::shared().add(hostname); } }