chromium/net/dns/dns_server_iterator.h

// Copyright 2020 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_DNS_SERVER_ITERATOR_H_
#define NET_DNS_DNS_SERVER_ITERATOR_H_

#include <stddef.h>
#include <vector>

#include "base/memory/raw_ptr.h"
#include "net/base/net_export.h"
#include "net/dns/public/secure_dns_mode.h"

namespace net {

class DnsSession;
class ResolveContext;

// Iterator used to get the next server to try for a DNS transaction.
// Each iterator should be scoped to a single query. A new query, therefore,
// requires a new iterator.
//
// Finds the first eligible server below the global failure limits
// (|max_failures|), or if no eligible servers are below failure limits, the
// eligible one with the oldest last failure. Global failures are tracked by
// ResolveContext.
//
// If |session| goes out of date, this iterator will report that no attempts are
// available and thus cease to return anything.
class NET_EXPORT_PRIVATE DnsServerIterator { … };

// Iterator used to get the next server to try for a DoH transaction.
// Each iterator should be scoped to a single query. A new query, therefore,
// requires a new iterator.
//
// Finds the first eligible server below the global failure limits
// (|max_failures|), or if no eligible servers are below failure limits, the
// eligible one with the oldest last failure. Global failures are tracked by
// ResolveContext.
//
// Once a server is returned |max_times_returned| times, it is ignored.
//
// If in AUTOMATIC mode, DoH servers are only eligible if "available".  See
// GetDohServerAvailability() for details.
class NET_EXPORT_PRIVATE DohDnsServerIterator : public DnsServerIterator { … };

// Iterator used to get the next server to try for a classic DNS transaction.
// Each iterator should be scoped to a single query. A new query, therefore,
// requires a new iterator.
//
// Finds the first eligible server below the global failure limits
// (|max_failures|), or if no eligible servers are below failure limits, the
// eligible one with the oldest last failure. Global failures are tracked by
// ResolveContext.

// Once a server is returned |max_times_returned| times, it is ignored.
class NET_EXPORT_PRIVATE ClassicDnsServerIterator : public DnsServerIterator { … };

}  // namespace net
#endif  // NET_DNS_DNS_SERVER_ITERATOR_H_