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* Copyright 2004 The WebRTC Project Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <map>
#include <set>
#include "rtc_base/async_udp_socket.h"
#include "rtc_base/nat_types.h"
#include "rtc_base/proxy_server.h"
#include "rtc_base/socket_address_pair.h"
#include "rtc_base/socket_factory.h"
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/thread.h"
namespace rtc {
// Change how routes (socketaddress pairs) are compared based on the type of
// NAT. The NAT server maintains a hashtable of the routes that it knows
// about. So these affect which routes are treated the same.
struct RouteCmp {
explicit RouteCmp(NAT* nat);
size_t operator()(const SocketAddressPair& r) const;
bool operator()(const SocketAddressPair& r1,
const SocketAddressPair& r2) const;
bool symmetric;
// Changes how addresses are compared based on the filtering rules of the NAT.
struct AddrCmp {
explicit AddrCmp(NAT* nat);
size_t operator()(const SocketAddress& r) const;
bool operator()(const SocketAddress& r1, const SocketAddress& r2) const;
bool use_ip;
bool use_port;
// Implements the NAT device. It listens for packets on the internal network,
// translates them, and sends them out over the external network.
// TCP connections initiated from the internal side of the NAT server are
// also supported, by making a connection to the NAT server's TCP address and
// then sending the remote address in quasi-STUN format. The connection status
// will be indicated back to the client as a 1 byte status code, where '0'
// indicates success.
const int NAT_SERVER_UDP_PORT = 4237;
const int NAT_SERVER_TCP_PORT = 4238;
class NATServer : public sigslot::has_slots<> {
NATServer(NATType type,
SocketFactory* internal,
const SocketAddress& internal_udp_addr,
const SocketAddress& internal_tcp_addr,
SocketFactory* external,
const SocketAddress& external_ip);
~NATServer() override;
NATServer(const NATServer&) = delete;
NATServer& operator=(const NATServer&) = delete;
SocketAddress internal_udp_address() const {
return udp_server_socket_->GetLocalAddress();
SocketAddress internal_tcp_address() const {
return tcp_proxy_server_->GetServerAddress();
// Packets received on one of the networks.
void OnInternalUDPPacket(AsyncPacketSocket* socket,
const char* buf,
size_t size,
const SocketAddress& addr,
const int64_t& packet_time_us);
void OnExternalUDPPacket(AsyncPacketSocket* socket,
const char* buf,
size_t size,
const SocketAddress& remote_addr,
const int64_t& packet_time_us);
typedef std::set<SocketAddress, AddrCmp> AddressSet;
/* Records a translation and the associated external socket. */
struct TransEntry {
TransEntry(const SocketAddressPair& r, AsyncUDPSocket* s, NAT* nat);
void AllowlistInsert(const SocketAddress& addr);
bool AllowlistContains(const SocketAddress& ext_addr);
SocketAddressPair route;
AsyncUDPSocket* socket;
AddressSet* allowlist;
webrtc::Mutex mutex_;
typedef std::map<SocketAddressPair, TransEntry*, RouteCmp> InternalMap;
typedef std::map<SocketAddress, TransEntry*> ExternalMap;
/* Creates a new entry that translates the given route. */
void Translate(const SocketAddressPair& route);
/* Determines whether the NAT would filter out a packet from this address. */
bool ShouldFilterOut(TransEntry* entry, const SocketAddress& ext_addr);
NAT* nat_;
SocketFactory* external_;
SocketAddress external_ip_;
AsyncUDPSocket* udp_server_socket_;
ProxyServer* tcp_proxy_server_;
InternalMap* int_map_;
ExternalMap* ext_map_;
} // namespace rtc