1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
|
/*
* 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/RetainPtr.h>
#include <wtf/StdLibExtras.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 coalesceDelay = 1.0;
// 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 appications' performance, by pushing their cached entries out, too.
// If we end up with lots of names to prefetch, some will be dropped.
const int maxRequestsToSend = 64;
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);
}
m_names.add(name);
if (!isActive())
startOneShot(coalesceDelay);
}
void DNSResolveQueue::decrementRequestCount()
{
atomicDecrement(&m_requestsInFlight);
}
void DNSResolveQueue::fired()
{
int requestsAllowed = maxRequestsToSend - m_requestsInFlight;
for (HashSet<String>::iterator iter = m_names.begin(); iter != m_names.end() && requestsAllowed > 0; ++iter, --requestsAllowed) {
atomicIncrement(&m_requestsInFlight);
resolve(*iter);
}
// It's better to skip some names than to clog the queue.
m_names.clear();
}
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);
}
}
|
