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// Copyright (c) 2012 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/dns/host_resolver.h"
#include "base/logging.h"
#include "base/metrics/field_trial.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_split.h"
#include "net/dns/dns_client.h"
#include "net/dns/dns_config_service.h"
#include "net/dns/host_cache.h"
#include "net/dns/host_resolver_impl.h"
namespace net {
namespace {
// Maximum of 6 concurrent resolver threads (excluding retries).
// Some routers (or resolvers) appear to start to provide host-not-found if
// too many simultaneous resolutions are pending. This number needs to be
// further optimized, but 8 is what FF currently does. We found some routers
// that limit this to 6, so we're temporarily holding it at that level.
const size_t kDefaultMaxProcTasks = 6u;
// When configuring from field trial, do not allow
const size_t kSaneMaxProcTasks = 20u;
PrioritizedDispatcher::Limits GetDispatcherLimits(
const HostResolver::Options& options) {
PrioritizedDispatcher::Limits limits(NUM_PRIORITIES,
options.max_concurrent_resolves);
// If not using default, do not use the field trial.
if (limits.total_jobs != HostResolver::kDefaultParallelism)
return limits;
// Default, without trial is no reserved slots.
limits.total_jobs = kDefaultMaxProcTasks;
// Parallelism is determined by the field trial.
std::string group = base::FieldTrialList::FindFullName(
"HostResolverDispatch");
if (group.empty())
return limits;
// The format of the group name is a list of non-negative integers separated
// by ':'. Each of the elements in the list corresponds to an element in
// |reserved_slots|, except the last one which is the |total_jobs|.
std::vector<std::string> group_parts;
base::SplitString(group, ':', &group_parts);
if (group_parts.size() != NUM_PRIORITIES + 1) {
NOTREACHED();
return limits;
}
std::vector<size_t> parsed(group_parts.size());
size_t total_reserved_slots = 0;
for (size_t i = 0; i < group_parts.size(); ++i) {
if (!base::StringToSizeT(group_parts[i], &parsed[i])) {
NOTREACHED();
return limits;
}
}
size_t total_jobs = parsed.back();
parsed.pop_back();
for (size_t i = 0; i < parsed.size(); ++i) {
total_reserved_slots += parsed[i];
}
// There must be some unreserved slots available for the all priorities.
if (total_reserved_slots > total_jobs ||
(total_reserved_slots == total_jobs && parsed[MINIMUM_PRIORITY] == 0)) {
NOTREACHED();
return limits;
}
limits.total_jobs = total_jobs;
limits.reserved_slots = parsed;
return limits;
}
} // namespace
HostResolver::Options::Options()
: max_concurrent_resolves(kDefaultParallelism),
max_retry_attempts(kDefaultRetryAttempts),
enable_caching(true) {
}
HostResolver::RequestInfo::RequestInfo(const HostPortPair& host_port_pair)
: host_port_pair_(host_port_pair),
address_family_(ADDRESS_FAMILY_UNSPECIFIED),
host_resolver_flags_(0),
allow_cached_response_(true),
is_speculative_(false) {}
HostResolver::~HostResolver() {
}
AddressFamily HostResolver::GetDefaultAddressFamily() const {
return ADDRESS_FAMILY_UNSPECIFIED;
}
void HostResolver::SetDnsClientEnabled(bool enabled) {
}
HostCache* HostResolver::GetHostCache() {
return NULL;
}
base::Value* HostResolver::GetDnsConfigAsValue() const {
return NULL;
}
// static
scoped_ptr<HostResolver>
HostResolver::CreateSystemResolver(const Options& options, NetLog* net_log) {
scoped_ptr<HostCache> cache;
if (options.enable_caching)
cache = HostCache::CreateDefaultCache();
return scoped_ptr<HostResolver>(new HostResolverImpl(
cache.Pass(),
GetDispatcherLimits(options),
HostResolverImpl::ProcTaskParams(NULL, options.max_retry_attempts),
net_log));
}
// static
scoped_ptr<HostResolver>
HostResolver::CreateDefaultResolver(NetLog* net_log) {
return CreateSystemResolver(Options(), net_log);
}
HostResolver::HostResolver() {
}
} // namespace net
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