net/dns/dns_util.h

// 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.

#ifndef NET_DNS_DNS_UTIL_H_
#define NET_DNS_DNS_UTIL_H_

#include <string>

#include "base/strings/string_piece.h"
#include "base/time/time.h"
#include "net/base/net_export.h"
#include "net/base/network_change_notifier.h"

namespace net {

class AddressList;

// DNSDomainFromDot - convert a domain string to DNS format. From DJB's
// public domain DNS library.
//
//   dotted: a string in dotted form: "www.google.com"
//   out: a result in DNS form: "\x03www\x06google\x03com\x00"
NET_EXPORT bool DNSDomainFromDot(const base::StringPiece& dotted,
                                 std::string* out);

// Checks that a hostname is valid. Simple wrapper around DNSDomainFromDot.
NET_EXPORT_PRIVATE bool IsValidDNSDomain(const base::StringPiece& dotted);

// Returns true if the character is valid in a DNS hostname label, whether in
// the first position or later in the label.
//
// This function asserts a looser form of the restrictions in RFC 7719 (section
// 2; https://tools.ietf.org/html/rfc7719#section-2): hostnames can include
// characters a-z, A-Z, 0-9, -, and _, and any of those characters (except -)
// are legal in the first position. The looser rules are necessary to support
// service records (initial _), and non-compliant but attested hostnames that
// include _. These looser rules also allow Punycode and hence IDN.
//
// TODO(palmer): In the future, when we can remove support for invalid names,
// this can be a private implementation detail of |DNSDomainFromDot|, and need
// not be NET_EXPORT_PRIVATE.
NET_EXPORT_PRIVATE bool IsValidHostLabelCharacter(char c, bool is_first_char);

// DNSDomainToString converts a domain in DNS format to a dotted string.
// Excludes the dot at the end.
NET_EXPORT std::string DNSDomainToString(const base::StringPiece& domain);

// Return the expanded template when no variables have corresponding values.
NET_EXPORT_PRIVATE std::string GetURLFromTemplateWithoutParameters(
    const std::string& server_template);

// Returns true if the URI template is acceptable for sending requests via the
// given method. The template must be properly formatted, GET requests require
// the template to contain a "dns" variable, an expanded template must parse
// to a valid HTTPS URL, and the "dns" variable may not be part of the hostname.
NET_EXPORT_PRIVATE bool IsValidDoHTemplate(const std::string& server_template,
                                           const std::string& server_method);

#if !defined(OS_NACL)
NET_EXPORT_PRIVATE
base::TimeDelta GetTimeDeltaForConnectionTypeFromFieldTrialOrDefault(
    const char* field_trial_name,
    base::TimeDelta default_delta,
    NetworkChangeNotifier::ConnectionType connection_type);
#endif  // !defined(OS_NACL)

// How similar or different two AddressLists are (see values for details).
// Used in histograms; do not modify existing values.
enum AddressListDeltaType {
  // Both lists contain the same addresses in the same order.
  DELTA_IDENTICAL = 0,
  // Both lists contain the same addresses in a different order.
  DELTA_REORDERED = 1,
  // The two lists have at least one address in common, but not all of them.
  DELTA_OVERLAP = 2,
  // The two lists have no addresses in common.
  DELTA_DISJOINT = 3,
  MAX_DELTA_TYPE
};

// Compares two AddressLists to see how similar or different their addresses
// are. (See |AddressListDeltaType| for details of exactly what's checked.)
NET_EXPORT
AddressListDeltaType FindAddressListDeltaType(const AddressList& a,
                                              const AddressList& b);

// Creates a 2-byte string that represents the name pointer defined in Section
// 4.1.1 of RFC 1035 for the given offset. The first two bits in the first byte
// of the name pointer are ones, and the rest 14 bits are given to |offset|,
// which specifies an offset from the start of the message for the pointed name.
// Note that |offset| must be less than 2^14 - 1 by definition.
NET_EXPORT std::string CreateNamePointer(uint16_t offset);

}  // namespace net

#endif  // NET_DNS_DNS_UTIL_H_