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// Copyright (c) 2010 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/base/host_resolver_proc.h"
#include "build/build_config.h"
#if defined(OS_POSIX) && !defined(OS_MACOSX)
#include <resolv.h>
#endif
#include "base/logging.h"
#include "net/base/address_list.h"
#include "net/base/dns_reload_timer.h"
#include "net/base/net_errors.h"
#include "net/base/sys_addrinfo.h"
namespace net {
HostResolverProc* HostResolverProc::default_proc_ = NULL;
HostResolverProc::HostResolverProc(HostResolverProc* previous) {
SetPreviousProc(previous);
// Implicitly fall-back to the global default procedure.
if (!previous)
SetPreviousProc(default_proc_);
}
void HostResolverProc::SetPreviousProc(HostResolverProc* proc) {
HostResolverProc* current_previous = previous_proc_;
previous_proc_ = NULL;
// Now that we've guaranteed |this| is the last proc in a chain, we can
// detect potential cycles using GetLastProc().
previous_proc_ = (GetLastProc(proc) == this) ? current_previous : proc;
}
void HostResolverProc::SetLastProc(HostResolverProc* proc) {
GetLastProc(this)->SetPreviousProc(proc);
}
// static
HostResolverProc* HostResolverProc::GetLastProc(HostResolverProc* proc) {
if (proc == NULL)
return NULL;
HostResolverProc* last_proc = proc;
while (last_proc->previous_proc_ != NULL)
last_proc = last_proc->previous_proc_;
return last_proc;
}
// static
HostResolverProc* HostResolverProc::SetDefault(HostResolverProc* proc) {
HostResolverProc* old = default_proc_;
default_proc_ = proc;
return old;
}
// static
HostResolverProc* HostResolverProc::GetDefault() {
return default_proc_;
}
int HostResolverProc::ResolveUsingPrevious(
const std::string& host,
AddressFamily address_family,
HostResolverFlags host_resolver_flags,
AddressList* addrlist,
int* os_error) {
if (previous_proc_) {
return previous_proc_->Resolve(host, address_family, host_resolver_flags,
addrlist, os_error);
}
// Final fallback is the system resolver.
return SystemHostResolverProc(host, address_family, host_resolver_flags,
addrlist, os_error);
}
int SystemHostResolverProc(const std::string& host,
AddressFamily address_family,
HostResolverFlags host_resolver_flags,
AddressList* addrlist,
int* os_error) {
static const size_t kMaxHostLength = 4096;
if (os_error)
*os_error = 0;
// The result of |getaddrinfo| for empty hosts is inconsistent across systems.
// On Windows it gives the default interface's address, whereas on Linux it
// gives an error. We will make it fail on all platforms for consistency.
if (host.empty())
return ERR_NAME_NOT_RESOLVED;
// Limit the size of hostnames that will be resolved to combat issues in some
// platform's resolvers.
if (host.size() > kMaxHostLength)
return ERR_NAME_NOT_RESOLVED;
struct addrinfo* ai = NULL;
struct addrinfo hints = {0};
switch (address_family) {
case ADDRESS_FAMILY_IPV4:
hints.ai_family = AF_INET;
break;
case ADDRESS_FAMILY_IPV6:
hints.ai_family = AF_INET6;
break;
case ADDRESS_FAMILY_UNSPECIFIED:
hints.ai_family = AF_UNSPEC;
break;
default:
NOTREACHED();
hints.ai_family = AF_UNSPEC;
}
#if defined(OS_WIN) || defined(OS_OPENBSD)
// DO NOT USE AI_ADDRCONFIG ON WINDOWS.
//
// The following comment in <winsock2.h> is the best documentation I found
// on AI_ADDRCONFIG for Windows:
// Flags used in "hints" argument to getaddrinfo()
// - AI_ADDRCONFIG is supported starting with Vista
// - default is AI_ADDRCONFIG ON whether the flag is set or not
// because the performance penalty in not having ADDRCONFIG in
// the multi-protocol stack environment is severe;
// this defaulting may be disabled by specifying the AI_ALL flag,
// in that case AI_ADDRCONFIG must be EXPLICITLY specified to
// enable ADDRCONFIG behavior
//
// Not only is AI_ADDRCONFIG unnecessary, but it can be harmful. If the
// computer is not connected to a network, AI_ADDRCONFIG causes getaddrinfo
// to fail with WSANO_DATA (11004) for "localhost", probably because of the
// following note on AI_ADDRCONFIG in the MSDN getaddrinfo page:
// The IPv4 or IPv6 loopback address is not considered a valid global
// address.
// See http://crbug.com/5234.
//
// OpenBSD does not support it, either.
hints.ai_flags = 0;
#else
hints.ai_flags = AI_ADDRCONFIG;
#endif
// On Linux AI_ADDRCONFIG doesn't consider loopback addreses, even if only
// loopback addresses are configured. So don't use it when there are only
// loopback addresses.
if (host_resolver_flags & HOST_RESOLVER_LOOPBACK_ONLY)
hints.ai_flags &= ~AI_ADDRCONFIG;
if (host_resolver_flags & HOST_RESOLVER_CANONNAME)
hints.ai_flags |= AI_CANONNAME;
// Restrict result set to only this socket type to avoid duplicates.
hints.ai_socktype = SOCK_STREAM;
int err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
#if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD)
// If we fail, re-initialise the resolver just in case there have been any
// changes to /etc/resolv.conf and retry. See http://crbug.com/11380 for info.
if (err && DnsReloadTimerHasExpired()) {
res_nclose(&_res);
if (!res_ninit(&_res))
err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
}
#endif
if (err) {
if (os_error) {
#if defined(OS_WIN)
*os_error = WSAGetLastError();
#else
*os_error = err;
#endif
}
return ERR_NAME_NOT_RESOLVED;
}
addrlist->Adopt(ai);
return OK;
}
} // namespace net
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