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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_BASE_HOST_RESOLVER_PROC_H_
      6 #define NET_BASE_HOST_RESOLVER_PROC_H_
      7 #pragma once
      8 
      9 #include <string>
     10 
     11 #include "base/memory/ref_counted.h"
     12 #include "net/base/address_family.h"
     13 
     14 namespace net {
     15 
     16 class AddressList;
     17 
     18 // Interface for a getaddrinfo()-like procedure. This is used by unit-tests
     19 // to control the underlying resolutions in HostResolverImpl. HostResolverProcs
     20 // can be chained together; they fallback to the next procedure in the chain
     21 // by calling ResolveUsingPrevious().
     22 //
     23 // Note that implementations of HostResolverProc *MUST BE THREADSAFE*, since
     24 // the HostResolver implementation using them can be multi-threaded.
     25 class HostResolverProc : public base::RefCountedThreadSafe<HostResolverProc> {
     26  public:
     27   explicit HostResolverProc(HostResolverProc* previous);
     28 
     29   // Resolves |host| to an address list, restricting the results to addresses
     30   // in |address_family|. If successful returns OK and fills |addrlist| with
     31   // a list of socket addresses. Otherwise returns a network error code, and
     32   // fills |os_error| with a more specific error if it was non-NULL.
     33   virtual int Resolve(const std::string& host,
     34                       AddressFamily address_family,
     35                       HostResolverFlags host_resolver_flags,
     36                       AddressList* addrlist,
     37                       int* os_error) = 0;
     38 
     39  protected:
     40   friend class base::RefCountedThreadSafe<HostResolverProc>;
     41 
     42   virtual ~HostResolverProc();
     43 
     44   // Asks the fallback procedure (if set) to do the resolve.
     45   int ResolveUsingPrevious(const std::string& host,
     46                            AddressFamily address_family,
     47                            HostResolverFlags host_resolver_flags,
     48                            AddressList* addrlist,
     49                            int* os_error);
     50 
     51  private:
     52   friend class HostResolverImpl;
     53   friend class MockHostResolverBase;
     54   friend class ScopedDefaultHostResolverProc;
     55 
     56   // Sets the previous procedure in the chain.  Aborts if this would result in a
     57   // cycle.
     58   void SetPreviousProc(HostResolverProc* proc);
     59 
     60   // Sets the last procedure in the chain, i.e. appends |proc| to the end of the
     61   // current chain.  Aborts if this would result in a cycle.
     62   void SetLastProc(HostResolverProc* proc);
     63 
     64   // Returns the last procedure in the chain starting at |proc|.  Will return
     65   // NULL iff |proc| is NULL.
     66   static HostResolverProc* GetLastProc(HostResolverProc* proc);
     67 
     68   // Sets the default host resolver procedure that is used by HostResolverImpl.
     69   // This can be used through ScopedDefaultHostResolverProc to set a catch-all
     70   // DNS block in unit-tests (individual tests should use MockHostResolver to
     71   // prevent hitting the network).
     72   static HostResolverProc* SetDefault(HostResolverProc* proc);
     73   static HostResolverProc* GetDefault();
     74 
     75   scoped_refptr<HostResolverProc> previous_proc_;
     76   static HostResolverProc* default_proc_;
     77 
     78   DISALLOW_COPY_AND_ASSIGN(HostResolverProc);
     79 };
     80 
     81 // Resolves |host| to an address list, using the system's default host resolver.
     82 // (i.e. this calls out to getaddrinfo()). If successful returns OK and fills
     83 // |addrlist| with a list of socket addresses. Otherwise returns a
     84 // network error code, and fills |os_error| with a more specific errir if it
     85 // was non-NULL.
     86 int SystemHostResolverProc(const std::string& host,
     87                            AddressFamily address_family,
     88                            HostResolverFlags host_resolver_flags,
     89                            AddressList* addrlist,
     90                            int* os_error);
     91 
     92 }  // namespace net
     93 
     94 #endif  // NET_BASE_HOST_RESOLVER_PROC_H_
     95