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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef NET_DNS_NSSWITCH_READER_H_
#define NET_DNS_NSSWITCH_READER_H_
#include <string>
#include <tuple>
#include <vector>
#include "base/functional/callback.h"
#include "net/base/net_export.h"
namespace net {
// Reader to read and parse Posix nsswitch.conf files, particularly the "hosts:"
// database entry.
class NET_EXPORT_PRIVATE NsswitchReader {
public:
// These values are emitted in metrics. Entries should not be renumbered and
// numeric values should never be reused. (See NsswitchService in
// tools/metrics/histograms/enums.xml.)
enum class Service {
kUnknown = 0,
kFiles = 1,
kDns = 2,
kMdns = 3,
kMdns4 = 4,
kMdns6 = 5,
kMdnsMinimal = 6,
kMdns4Minimal = 7,
kMdns6Minimal = 8,
kMyHostname = 9,
kResolve = 10,
kNis = 11,
kMaxValue = kNis
};
enum class Status {
kUnknown,
kSuccess,
kNotFound,
kUnavailable,
kTryAgain,
};
enum class Action {
kUnknown,
kReturn,
kContinue,
kMerge,
};
struct ServiceAction {
bool operator==(const ServiceAction& other) const {
return std::tie(negated, status, action) ==
std::tie(other.negated, other.status, other.action);
}
bool negated;
Status status;
Action action;
};
struct NET_EXPORT_PRIVATE ServiceSpecification {
explicit ServiceSpecification(Service service,
std::vector<ServiceAction> actions = {});
~ServiceSpecification();
ServiceSpecification(const ServiceSpecification&);
ServiceSpecification& operator=(const ServiceSpecification&);
ServiceSpecification(ServiceSpecification&&);
ServiceSpecification& operator=(ServiceSpecification&&);
bool operator==(const ServiceSpecification& other) const {
return std::tie(service, actions) ==
std::tie(other.service, other.actions);
}
Service service;
std::vector<ServiceAction> actions;
};
// Test-replacable call for the actual file read. Default implementation does
// a fresh read of the nsswitch.conf file every time it is called. Returns
// empty string on error reading the file.
using FileReadCall = base::RepeatingCallback<std::string()>;
NsswitchReader();
virtual ~NsswitchReader();
NsswitchReader(const NsswitchReader&) = delete;
NsswitchReader& operator=(const NsswitchReader&) = delete;
// Reads nsswitch.conf and parses the "hosts:" database. In case of multiple
// matching databases, only parses the first. Assumes a basic default
// configuration if the file cannot be read or a "hosts:" database cannot be
// found.
virtual std::vector<ServiceSpecification> ReadAndParseHosts();
void set_file_read_call_for_testing(FileReadCall file_read_call) {
file_read_call_ = std::move(file_read_call);
}
private:
FileReadCall file_read_call_;
};
} // namespace net
#endif // NET_DNS_NSSWITCH_READER_H_
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