1 /*
2  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef RTC_BASE_NATSERVER_H_
12 #define RTC_BASE_NATSERVER_H_
13 
14 #include <map>
15 #include <set>
16 
17 #include "rtc_base/asyncudpsocket.h"
18 #include "rtc_base/constructormagic.h"
19 #include "rtc_base/nattypes.h"
20 #include "rtc_base/proxyserver.h"
21 #include "rtc_base/socketaddresspair.h"
22 #include "rtc_base/socketfactory.h"
23 #include "rtc_base/thread.h"
24 
25 namespace rtc {
26 
27 // Change how routes (socketaddress pairs) are compared based on the type of
28 // NAT.  The NAT server maintains a hashtable of the routes that it knows
29 // about.  So these affect which routes are treated the same.
30 struct RouteCmp {
31   explicit RouteCmp(NAT* nat);
32   size_t operator()(const SocketAddressPair& r) const;
33   bool operator()(
34       const SocketAddressPair& r1, const SocketAddressPair& r2) const;
35 
36   bool symmetric;
37 };
38 
39 // Changes how addresses are compared based on the filtering rules of the NAT.
40 struct AddrCmp {
41   explicit AddrCmp(NAT* nat);
42   size_t operator()(const SocketAddress& r) const;
43   bool operator()(const SocketAddress& r1, const SocketAddress& r2) const;
44 
45   bool use_ip;
46   bool use_port;
47 };
48 
49 // Implements the NAT device.  It listens for packets on the internal network,
50 // translates them, and sends them out over the external network.
51 //
52 // TCP connections initiated from the internal side of the NAT server are
53 // also supported, by making a connection to the NAT server's TCP address and
54 // then sending the remote address in quasi-STUN format. The connection status
55 // will be indicated back to the client as a 1 byte status code, where '0'
56 // indicates success.
57 
58 const int NAT_SERVER_UDP_PORT = 4237;
59 const int NAT_SERVER_TCP_PORT = 4238;
60 
61 class NATServer : public sigslot::has_slots<> {
62  public:
63   NATServer(
64       NATType type, SocketFactory* internal,
65       const SocketAddress& internal_udp_addr,
66       const SocketAddress& internal_tcp_addr,
67       SocketFactory* external, const SocketAddress& external_ip);
68   ~NATServer() override;
69 
internal_udp_address()70   SocketAddress internal_udp_address() const {
71     return udp_server_socket_->GetLocalAddress();
72   }
73 
internal_tcp_address()74   SocketAddress internal_tcp_address() const {
75     return tcp_proxy_server_->GetServerAddress();
76   }
77 
78   // Packets received on one of the networks.
79   void OnInternalUDPPacket(AsyncPacketSocket* socket, const char* buf,
80                            size_t size, const SocketAddress& addr,
81                            const PacketTime& packet_time);
82   void OnExternalUDPPacket(AsyncPacketSocket* socket, const char* buf,
83                            size_t size, const SocketAddress& remote_addr,
84                            const PacketTime& packet_time);
85 
86  private:
87   typedef std::set<SocketAddress, AddrCmp> AddressSet;
88 
89   /* Records a translation and the associated external socket. */
90   struct TransEntry {
91     TransEntry(const SocketAddressPair& r, AsyncUDPSocket* s, NAT* nat);
92     ~TransEntry();
93 
94     void WhitelistInsert(const SocketAddress& addr);
95     bool WhitelistContains(const SocketAddress& ext_addr);
96 
97     SocketAddressPair route;
98     AsyncUDPSocket* socket;
99     AddressSet* whitelist;
100     CriticalSection crit_;
101   };
102 
103   typedef std::map<SocketAddressPair, TransEntry*, RouteCmp> InternalMap;
104   typedef std::map<SocketAddress, TransEntry*> ExternalMap;
105 
106   /* Creates a new entry that translates the given route. */
107   void Translate(const SocketAddressPair& route);
108 
109   /* Determines whether the NAT would filter out a packet from this address. */
110   bool ShouldFilterOut(TransEntry* entry, const SocketAddress& ext_addr);
111 
112   NAT* nat_;
113   SocketFactory* external_;
114   SocketAddress external_ip_;
115   AsyncUDPSocket* udp_server_socket_;
116   ProxyServer* tcp_proxy_server_;
117   InternalMap* int_map_;
118   ExternalMap* ext_map_;
119   RTC_DISALLOW_COPY_AND_ASSIGN(NATServer);
120 };
121 
122 }  // namespace rtc
123 
124 #endif  // RTC_BASE_NATSERVER_H_
125