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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 "rtc_base/nat_server.h"
#include <cstddef>
#include <cstdint>
#include <memory>
#include "api/array_view.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/nat_socket_factory.h"
#include "rtc_base/network/received_packet.h"
#include "rtc_base/socket_adapters.h"
#include "rtc_base/socket_address.h"
namespace rtc {
RouteCmp::RouteCmp(NAT* nat) : symmetric(nat->IsSymmetric()) {}
size_t RouteCmp::operator()(const SocketAddressPair& r) const {
size_t h = r.source().Hash();
if (symmetric)
h ^= r.destination().Hash();
return h;
}
bool RouteCmp::operator()(const SocketAddressPair& r1,
const SocketAddressPair& r2) const {
if (r1.source() < r2.source())
return true;
if (r2.source() < r1.source())
return false;
if (symmetric && (r1.destination() < r2.destination()))
return true;
if (symmetric && (r2.destination() < r1.destination()))
return false;
return false;
}
AddrCmp::AddrCmp(NAT* nat)
: use_ip(nat->FiltersIP()), use_port(nat->FiltersPort()) {}
size_t AddrCmp::operator()(const SocketAddress& a) const {
size_t h = 0;
if (use_ip)
h ^= HashIP(a.ipaddr());
if (use_port)
h ^= a.port() | (a.port() << 16);
return h;
}
bool AddrCmp::operator()(const SocketAddress& a1,
const SocketAddress& a2) const {
if (use_ip && (a1.ipaddr() < a2.ipaddr()))
return true;
if (use_ip && (a2.ipaddr() < a1.ipaddr()))
return false;
if (use_port && (a1.port() < a2.port()))
return true;
if (use_port && (a2.port() < a1.port()))
return false;
return false;
}
// Proxy socket that will capture the external destination address intended for
// a TCP connection to the NAT server.
class NATProxyServerSocket : public AsyncProxyServerSocket {
public:
NATProxyServerSocket(Socket* socket)
: AsyncProxyServerSocket(socket, kNATEncodedIPv6AddressSize) {
BufferInput(true);
}
void SendConnectResult(int err, const SocketAddress& addr) override {
char code = err ? 1 : 0;
BufferedReadAdapter::DirectSend(&code, sizeof(char));
}
protected:
void ProcessInput(char* data, size_t* len) override {
if (*len < 2) {
return;
}
int family = data[1];
RTC_DCHECK(family == AF_INET || family == AF_INET6);
if ((family == AF_INET && *len < kNATEncodedIPv4AddressSize) ||
(family == AF_INET6 && *len < kNATEncodedIPv6AddressSize)) {
return;
}
SocketAddress dest_addr;
size_t address_length = UnpackAddressFromNAT(
MakeArrayView(reinterpret_cast<const uint8_t*>(data), *len),
&dest_addr);
*len -= address_length;
if (*len > 0) {
memmove(data, data + address_length, *len);
}
bool remainder = (*len > 0);
BufferInput(false);
SignalConnectRequest(this, dest_addr);
if (remainder) {
SignalReadEvent(this);
}
}
};
class NATProxyServer : public ProxyServer {
public:
NATProxyServer(SocketFactory* int_factory,
const SocketAddress& int_addr,
SocketFactory* ext_factory,
const SocketAddress& ext_ip)
: ProxyServer(int_factory, int_addr, ext_factory, ext_ip) {}
protected:
AsyncProxyServerSocket* WrapSocket(Socket* socket) override {
return new NATProxyServerSocket(socket);
}
};
NATServer::NATServer(NATType type,
rtc::Thread& internal_socket_thread,
SocketFactory* internal,
const SocketAddress& internal_udp_addr,
const SocketAddress& internal_tcp_addr,
rtc::Thread& external_socket_thread,
SocketFactory* external,
const SocketAddress& external_ip)
: internal_socket_thread_(internal_socket_thread),
external_socket_thread_(external_socket_thread),
external_(external),
external_ip_(external_ip.ipaddr(), 0) {
nat_ = NAT::Create(type);
internal_socket_thread_.BlockingCall([&] {
udp_server_socket_ = AsyncUDPSocket::Create(internal, internal_udp_addr);
udp_server_socket_->RegisterReceivedPacketCallback(
[&](rtc::AsyncPacketSocket* socket, const rtc::ReceivedPacket& packet) {
OnInternalUDPPacket(socket, packet);
});
});
tcp_proxy_server_ =
new NATProxyServer(internal, internal_tcp_addr, external, external_ip);
int_map_ = new InternalMap(RouteCmp(nat_));
ext_map_ = new ExternalMap();
}
NATServer::~NATServer() {
for (InternalMap::iterator iter = int_map_->begin(); iter != int_map_->end();
iter++)
delete iter->second;
delete nat_;
delete udp_server_socket_;
delete tcp_proxy_server_;
delete int_map_;
delete ext_map_;
}
void NATServer::OnInternalUDPPacket(AsyncPacketSocket* socket,
const rtc::ReceivedPacket& packet) {
RTC_DCHECK(internal_socket_thread_.IsCurrent());
// Read the intended destination from the wire.
SocketAddress dest_addr;
size_t length = UnpackAddressFromNAT(packet.payload(), &dest_addr);
// Find the translation for these addresses (allocating one if necessary).
SocketAddressPair route(packet.source_address(), dest_addr);
InternalMap::iterator iter = int_map_->find(route);
if (iter == int_map_->end()) {
Translate(route);
iter = int_map_->find(route);
}
RTC_DCHECK(iter != int_map_->end());
// Allow the destination to send packets back to the source.
iter->second->AllowlistInsert(dest_addr);
// Send the packet to its intended destination.
rtc::PacketOptions options;
const char* buf = reinterpret_cast<const char*>(packet.payload().data());
size_t size = packet.payload().size();
iter->second->socket->SendTo(buf + length, size - length, dest_addr, options);
}
void NATServer::OnExternalUDPPacket(AsyncPacketSocket* socket,
const rtc::ReceivedPacket& packet) {
RTC_DCHECK(external_socket_thread_.IsCurrent());
SocketAddress local_addr = socket->GetLocalAddress();
// Find the translation for this addresses.
ExternalMap::iterator iter = ext_map_->find(local_addr);
RTC_DCHECK(iter != ext_map_->end());
// Allow the NAT to reject this packet.
if (ShouldFilterOut(iter->second, packet.source_address())) {
RTC_LOG(LS_INFO) << "Packet from "
<< packet.source_address().ToSensitiveString()
<< " was filtered out by the NAT.";
return;
}
// Forward this packet to the internal address.
// First prepend the address in a quasi-STUN format.
std::unique_ptr<char[]> real_buf(
new char[packet.payload().size() + kNATEncodedIPv6AddressSize]);
size_t addrlength = PackAddressForNAT(
real_buf.get(), packet.payload().size() + kNATEncodedIPv6AddressSize,
packet.source_address());
// Copy the data part after the address.
rtc::PacketOptions options;
memcpy(real_buf.get() + addrlength, packet.payload().data(),
packet.payload().size());
udp_server_socket_->SendTo(real_buf.get(),
packet.payload().size() + addrlength,
iter->second->route.source(), options);
}
void NATServer::Translate(const SocketAddressPair& route) {
external_socket_thread_.BlockingCall([&] {
AsyncUDPSocket* socket = AsyncUDPSocket::Create(external_, external_ip_);
if (!socket) {
RTC_LOG(LS_ERROR) << "Couldn't find a free port!";
return;
}
TransEntry* entry = new TransEntry(route, socket, nat_);
(*int_map_)[route] = entry;
(*ext_map_)[socket->GetLocalAddress()] = entry;
socket->RegisterReceivedPacketCallback(
[&](rtc::AsyncPacketSocket* socket, const rtc::ReceivedPacket& packet) {
OnExternalUDPPacket(socket, packet);
});
});
}
bool NATServer::ShouldFilterOut(TransEntry* entry,
const SocketAddress& ext_addr) {
return entry->AllowlistContains(ext_addr);
}
NATServer::TransEntry::TransEntry(const SocketAddressPair& r,
AsyncUDPSocket* s,
NAT* nat)
: route(r), socket(s) {
allowlist = new AddressSet(AddrCmp(nat));
}
NATServer::TransEntry::~TransEntry() {
delete allowlist;
delete socket;
}
void NATServer::TransEntry::AllowlistInsert(const SocketAddress& addr) {
webrtc::MutexLock lock(&mutex_);
allowlist->insert(addr);
}
bool NATServer::TransEntry::AllowlistContains(const SocketAddress& ext_addr) {
webrtc::MutexLock lock(&mutex_);
return allowlist->find(ext_addr) == allowlist->end();
}
} // namespace rtc