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// Copyright 2012 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_HOST_RESOLVER_PROC_H_
#define NET_DNS_HOST_RESOLVER_PROC_H_
#include <string>
#include "base/memory/ref_counted.h"
#include "net/base/address_family.h"
#include "net/base/net_export.h"
#include "net/base/network_handle.h"
namespace net {
class AddressList;
// Interface for a getaddrinfo()-like procedure. This is used by tests
// to control the underlying resolutions in HostResolverManager.
// HostResolverProcs can be chained together; they fallback to the next
// procedure in the chain by calling ResolveUsingPrevious(). Unless
// `allow_fallback_to_system_or_default` is set to false, `default_proc_`
// (set via SetDefault()) is added to the end of the chain and the actual system
// resolver acts as the final fallback after the default proc.
//
// Note that implementations of HostResolverProc *MUST BE THREADSAFE*, since
// the HostResolver implementation using them can be multi-threaded.
class NET_EXPORT HostResolverProc
: public base::RefCountedThreadSafe<HostResolverProc> {
public:
explicit HostResolverProc(scoped_refptr<HostResolverProc> previous,
bool allow_fallback_to_system_or_default = true);
HostResolverProc(const HostResolverProc&) = delete;
HostResolverProc& operator=(const HostResolverProc&) = delete;
// Resolves |host| to an address list, restricting the results to addresses
// in |address_family|. If successful returns OK and fills |addrlist| with
// a list of socket addresses. Otherwise returns a network error code, and
// fills |os_error| with a more specific error if it was non-NULL.
virtual int Resolve(const std::string& host,
AddressFamily address_family,
HostResolverFlags host_resolver_flags,
AddressList* addrlist,
int* os_error) = 0;
// Same as above but requires an additional `network` parameter. Differently
// from above the lookup will be performed specifically for `network`.
virtual int Resolve(const std::string& host,
AddressFamily address_family,
HostResolverFlags host_resolver_flags,
AddressList* addrlist,
int* os_error,
handles::NetworkHandle network);
protected:
friend class base::RefCountedThreadSafe<HostResolverProc>;
virtual ~HostResolverProc();
// Asks the fallback procedure (if set) to do the resolve.
int ResolveUsingPrevious(const std::string& host,
AddressFamily address_family,
HostResolverFlags host_resolver_flags,
AddressList* addrlist,
int* os_error);
private:
friend class HostResolverManager;
friend class HostResolverSystemTask;
friend class MockHostResolverBase;
friend class ScopedDefaultHostResolverProc;
// Sets the previous procedure in the chain. Aborts if this would result in a
// cycle.
void SetPreviousProc(scoped_refptr<HostResolverProc> proc);
// Sets the last procedure in the chain, i.e. appends |proc| to the end of the
// current chain. Aborts if this would result in a cycle.
void SetLastProc(scoped_refptr<HostResolverProc> proc);
// Returns the last procedure in the chain starting at |proc|. Will return
// NULL iff |proc| is NULL.
static HostResolverProc* GetLastProc(HostResolverProc* proc);
// Sets the default host resolver procedure that is used by
// HostResolverManager. This can be used through ScopedDefaultHostResolverProc
// to set a catch-all DNS block in unit-tests (individual tests should use
// MockHostResolver to prevent hitting the network).
static HostResolverProc* SetDefault(HostResolverProc* proc);
static HostResolverProc* GetDefault();
bool allow_fallback_to_system_;
scoped_refptr<HostResolverProc> previous_proc_;
static HostResolverProc* default_proc_;
};
} // namespace net
#endif // NET_DNS_HOST_RESOLVER_PROC_H_
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