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/*
* 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 "KURL.h"
#include "Timer.h"
#include <wtf/HashSet.h>
#include <wtf/RetainPtr.h>
#include <wtf/StdLibExtras.h>
#include <wtf/text/StringHash.h>
#if PLATFORM(WIN)
#include "LoaderRunLoopCF.h"
#endif
#if defined(BUILDING_ON_LEOPARD)
#include <SystemConfiguration/SystemConfiguration.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;
static bool proxyIsEnabledInSystemPreferences()
{
// Don't do DNS prefetch if proxies are involved. For many proxy types, the user agent is never exposed
// to the IP address during normal operation. Querying an internal DNS server may not help performance,
// as it doesn't necessarily look up the actual external IP. Also, if DNS returns a fake internal address,
// local caches may keep it even after re-connecting to another network.
#if !defined(BUILDING_ON_LEOPARD)
RetainPtr<CFDictionaryRef> proxySettings(AdoptCF, CFNetworkCopySystemProxySettings());
#else
RetainPtr<CFDictionaryRef> proxySettings(AdoptCF, SCDynamicStoreCopyProxies(0));
#endif
if (!proxySettings)
return false;
static CFURLRef httpCFURL = KURL(ParsedURLString, "http://example.com/").createCFURL();
static CFURLRef httpsCFURL = KURL(ParsedURLString, "https://example.com/").createCFURL();
RetainPtr<CFArrayRef> httpProxyArray(AdoptCF, CFNetworkCopyProxiesForURL(httpCFURL, proxySettings.get()));
RetainPtr<CFArrayRef> httpsProxyArray(AdoptCF, CFNetworkCopyProxiesForURL(httpsCFURL, proxySettings.get()));
CFIndex httpProxyCount = CFArrayGetCount(httpProxyArray.get());
CFIndex httpsProxyCount = CFArrayGetCount(httpsProxyArray.get());
if (httpProxyCount == 1 && CFEqual(CFDictionaryGetValue(static_cast<CFDictionaryRef>(CFArrayGetValueAtIndex(httpProxyArray.get(), 0)), kCFProxyTypeKey), kCFProxyTypeNone))
httpProxyCount = 0;
if (httpsProxyCount == 1 && CFEqual(CFDictionaryGetValue(static_cast<CFDictionaryRef>(CFArrayGetValueAtIndex(httpsProxyArray.get(), 0)), kCFProxyTypeKey), kCFProxyTypeNone))
httpsProxyCount = 0;
return httpProxyCount || httpsProxyCount;
}
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 (proxyIsEnabledInSystemPreferences())
return;
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()
{
if (proxyIsEnabledInSystemPreferences()) {
m_names.clear();
return;
}
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());
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());
if (hostname.isEmpty())
return;
DNSResolveQueue::shared().add(hostname);
}
}
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