tobast/congestvpn
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Switch to single connection paradigm, use TLVs.

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Clean up dramatically the codebase by assuming the server has only a
single connection at any time.
This commit is contained in:
Théophile Bastian 2020-06-15 20:21:07 +02:00
parent 324d156cf3
commit 94f42d08c0
10 changed files with 178 additions and 197 deletions
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77
UdpVpn.cpp
View file

@ -14,7 +14,7 @@
static const size_t VPN_MTU = 1460; // TODO determine this -- issue #3
UdpVpn::UdpVpn()
: _stopped(false), _vpn_mtu(VPN_MTU), _tun_dev("cvpn%d")
: _stopped(false), _vpn_mtu(VPN_MTU), _tun_dev("cvpn%d"), _peer(nullptr)
{
_socket = socket(AF_INET6, SOCK_DGRAM, 0);
if(_socket < 0)
@ -74,7 +74,7 @@ size_t UdpVpn::read_from_tun(char* buffer, size_t len) {
return _tun_dev.read(buffer, len);
}
size_t UdpVpn::read_from_tun(VpnPacket& packet) {
size_t UdpVpn::read_from_tun(TunnelledPacket& packet) {
size_t nread =
read_from_tun(packet.get_payload(), packet.get_payload_space());
packet.set_payload_size(nread);
@ -118,10 +118,75 @@ size_t UdpVpn::read_from_udp(VpnPacket& packet, sockaddr_in6& peer_addr) {
size_t nread =
read_from_udp(packet.get_data(), packet.get_data_space(), peer_addr);
packet.set_data_size(nread);
if(!packet.parse_as_ipv6()) {
debugf("Ignoring packet with invalid header\n");
return 0;
}
return nread;
}
size_t UdpVpn::transmit_to_peer(VpnPacket& packet) {
if(!_peer) {
debugf("Dropping packet: no peer yet.\n");
return 0;
}
return _peer->write(packet);
}
void UdpVpn::receive_from_tun() {
VpnPacket packet(_vpn_mtu);
TunnelledPacket tunnelled = TunnelledPacket::create(packet);
size_t nread = read_from_tun(tunnelled);
if(nread == 0)
return;
if(!_peer) {
debugf("Dropping packet: no peer yet.\n");
return;
}
packet.set_peer(_peer.get());
kdebugf("Transmitting %s -> %s, size %d\n",
format_address(tunnelled.get_ipv6_header().source.s6_addr),
format_address(tunnelled.get_ipv6_header().dest.s6_addr),
nread);
packet.prepare_for_sending();
transmit_to_peer(packet);
}
void UdpVpn::receive_from_udp() {
VpnPacket packet(_vpn_mtu);
sockaddr_in6 peer_ext_addr;
size_t nread = read_from_udp(packet, peer_ext_addr);
if(nread == 0)
return;
// If we don't have a peer yet -- we're just setting the peer to nullptr.
packet.set_peer(_peer.get());
for(VpnPacketTLV tlv=packet.first_tlv();
!tlv.past_the_end();
tlv.seek_next_tlv())
{
switch(tlv.get_type()) {
case VpnPacket::PAYLOAD_TYPE_TUNNELLED:
{
TunnelledPacket tunnelled(tlv);
acquire_peer(tunnelled, peer_ext_addr);
receive_tunnelled_tlv(tunnelled);
}
break;
case VpnPacket::PAYLOAD_TYPE_UNDEF:
default:
debugf("#%d+%lu: ignoring TLV with bad type %d.\n",
packet.get_seqno(), tlv.get_offset(),
tlv.get_type());
break;
}
}
}
void UdpVpn::receive_tunnelled_tlv(TunnelledPacket& packet) {
// Reinject into tun
kdebugf("Reinjecting tunnelled packet of size %d\n",
packet.get_payload_size());
_tun_dev.write(packet.get_payload(), packet.get_payload_size());
}

15
UdpVpn.hpp
View file

@ -42,18 +42,27 @@ class UdpVpn {
void stop() { _stopped = true; }
protected:
virtual void receive_from_tun() = 0;
virtual void receive_from_udp() = 0;
virtual void acquire_peer(
TunnelledPacket& packet,
const sockaddr_in6& peer_ext_addr) = 0;
size_t read_from_tun(char* buffer, size_t len);
size_t read_from_tun(VpnPacket& packet);
size_t read_from_tun(TunnelledPacket& packet);
size_t read_from_udp(char* buffer, size_t len, sockaddr_in6& peer_addr);
size_t read_from_udp(VpnPacket& packet, sockaddr_in6& peer_addr);
size_t transmit_to_peer(VpnPacket& packet);
void receive_from_tun();
void receive_from_udp();
void receive_tunnelled_tlv(TunnelledPacket& packet);
int _socket;
bool _stopped;
size_t _vpn_mtu;
TunDevice _tun_dev;
std::unique_ptr<VpnPeer> _peer;
};

55
UdpVpnClient.cpp
View file

@ -4,55 +4,14 @@
#include "ip_header.hpp"
UdpVpnClient::UdpVpnClient(const struct sockaddr_in6& server) : UdpVpn() {
memset(&_server_addr, 0, sizeof(_server_addr));
set_server(server);
_peer = std::make_unique<VpnPeer>(this, server, in6addr_any);
}
void UdpVpnClient::set_server(const struct sockaddr_in6& server_addr) {
if(server_addr.sin6_family != AF_INET6)
throw UdpVpn::InitializationError("Server address must be IPv6");
memcpy(&_server_addr, &server_addr, sizeof(_server_addr));
}
void UdpVpnClient::receive_from_tun() {
VpnPacket packet(_vpn_mtu);
size_t nread = read_from_tun(packet);
if(nread == 0)
void UdpVpnClient::acquire_peer(
TunnelledPacket& packet,
const sockaddr_in6&)
{
if(!packet.parse_as_ipv6())
return;
kdebugf("Transmitting %s -> %s, size %d\n",
format_address(packet.get_ipv6_header().source.s6_addr),
format_address(packet.get_ipv6_header().dest.s6_addr),
nread);
packet.prepare_for_sending();
write_to_server(packet);
}
void UdpVpnClient::receive_from_udp() {
VpnPacket packet(_vpn_mtu);
sockaddr_in6 peer_addr;
size_t nread = read_from_udp(packet, peer_addr);
if(nread == 0)
return;
// Reinject into tun
kdebugf("Receiving packet #%u of size %d from %s\n",
packet.get_seqno(),
nread,
format_address(packet.get_ipv6_header().source.s6_addr));
_tun_dev.write(packet.get_payload(), packet.get_payload_size());
}
size_t UdpVpnClient::write_to_server(const VpnPacket& packet) {
ssize_t nsent;
nsent = sendto(_socket, packet.get_data(), packet.get_data_size(),
MSG_CONFIRM,
(const struct sockaddr*) &_server_addr, sizeof(_server_addr));
if(nsent < 0)
throw NetError("Could not send UDP packet", errno, true);
return (size_t) nsent;
_peer->set_int_addr(packet.get_ipv6_header().source);
}

11
UdpVpnClient.hpp
View file

@ -7,12 +7,7 @@ class UdpVpnClient: public UdpVpn {
UdpVpnClient(const struct sockaddr_in6& server);
protected:
void set_server(const struct sockaddr_in6& server_addr);
virtual void receive_from_tun();
virtual void receive_from_udp();
size_t write_to_server(const VpnPacket& packet);
struct sockaddr_in6 _server_addr;
virtual void acquire_peer(
TunnelledPacket& packet,
const sockaddr_in6& peer_ext_addr);
};

84
UdpVpnServer.cpp
View file

@ -15,6 +15,27 @@ UdpVpnServer::UdpVpnServer(const struct in6_addr& bind_addr6, in_port_t port)
bind(bind_addr6, port);
}
void UdpVpnServer::acquire_peer(
TunnelledPacket& packet,
const sockaddr_in6& peer_ext_addr)
{
if(_peer)
return; // Refusing a connection if we already have one
// TODO: reset state at some point/if connection broken
if(!packet.parse_as_ipv6())
return;
const in6_addr& peer_inner_addr = packet.get_ipv6_header().source;
_peer = std::make_unique<VpnPeer>(this, peer_ext_addr, peer_inner_addr);
packet.get_packet().set_peer(_peer.get());
debugf("Got new peer %s:%d -- %s\n",
format_address(peer_ext_addr.sin6_addr.s6_addr),
htons(peer_ext_addr.sin6_port),
format_address(peer_inner_addr.s6_addr));
}
void UdpVpnServer::bind(const struct in6_addr& bind_addr6, in_port_t port) {
int rc;
@ -30,66 +51,3 @@ void UdpVpnServer::bind(const struct in6_addr& bind_addr6, in_port_t port) {
debugf("> Listening on port %d\n", port);
}
std::shared_ptr<VpnPeer> UdpVpnServer::get_peer_for_ip(
const in6_addr& peer_addr)
{
auto peer_iter = _peers.find(peer_addr);
if(peer_iter == _peers.end()) // Unknown peer
return nullptr;
return peer_iter->second;
}
void UdpVpnServer::receive_from_tun() {
VpnPacket packet(_vpn_mtu);
size_t nread = read_from_tun(packet);
if(nread == 0)
return;
// Recover VpnPeer -- or drop if new
const in6_addr& peer_inner_addr = packet.get_ipv6_header().dest;
std::shared_ptr<VpnPeer> peer = get_peer_for_ip(peer_inner_addr);
if(!peer) {
debugf("Dropping packet for destination %s -- unknown peer.\n",
format_address(peer_inner_addr.s6_addr));
return;
}
packet.set_peer(peer);
kdebugf("Transmitting %s -> %s, size %d\n",
format_address(packet.get_ipv6_header().source.s6_addr),
format_address(packet.get_ipv6_header().dest.s6_addr),
nread);
packet.prepare_for_sending();
peer->write(packet);
}
void UdpVpnServer::receive_from_udp() {
VpnPacket packet(_vpn_mtu);
sockaddr_in6 peer_addr;
size_t nread = read_from_udp(packet, peer_addr);
if(nread == 0)
return;
// Recover VpnPeer -- or create if new
const in6_addr& peer_inner_addr = packet.get_ipv6_header().source;
std::shared_ptr<VpnPeer> peer = get_peer_for_ip(peer_inner_addr);
if(!peer) {
peer = std::make_shared<VpnPeer>(this, peer_addr, peer_inner_addr);
_peers.insert({peer_inner_addr, peer});
debugf("Got new peer %s:%d -- %s\n",
format_address(peer_addr.sin6_addr.s6_addr),
htons(peer_addr.sin6_port),
format_address(peer_inner_addr.s6_addr));
}
packet.set_peer(peer);
// Reinject into tun
kdebugf("Receiving packet #%u of size %d from %s\n",
packet.get_seqno(),
nread,
format_address(packet.get_ipv6_header().source.s6_addr));
_tun_dev.write(packet.get_payload(), packet.get_payload_size());
}

11
UdpVpnServer.hpp
View file

@ -10,14 +10,11 @@ class UdpVpnServer: public UdpVpn {
UdpVpnServer(in_port_t port);
UdpVpnServer(const struct in6_addr& bind_addr6, in_port_t port);
protected:
virtual void acquire_peer(
TunnelledPacket& packet,
const sockaddr_in6& peer_ext_addr);
void bind(const struct in6_addr& bind_addr6, in_port_t port);
/** Get the peer associated to this (internal) IP. */
std::shared_ptr<VpnPeer> get_peer_for_ip(const in6_addr& peer_addr);
virtual void receive_from_tun();
virtual void receive_from_udp();
struct sockaddr_in6 _bind_addr;
std::unordered_map<in6_addr, std::shared_ptr<VpnPeer>> _peers;
};

33
VpnPacket.cpp
View file

@ -6,7 +6,6 @@
const size_t VpnPacket::VPN_HEADER_BYTES = 8;
const size_t VpnPacket::TLV_HEADER_BYTES = 3;
uint32_t VpnPacket::_next_general_seqno = 0;
static const size_t OUTER_HEADERS_BYTES =
40 /* IPv6 header */ + 8 /* UDP header */;
@ -27,15 +26,8 @@ VpnPacket::~VpnPacket() {
delete[] _data;
}
VpnPacket::iterator VpnPacket::begin() {
return iterator(VpnPacketTLV(*this, 0));
}
VpnPacket::iterator VpnPacket::end() {
return iterator(VpnPacketTLV(*this, get_payload_size()));
}
bool VpnPacket::parse_as_ipv6() {
return parse_ipv6_header(get_payload(), get_payload_size(), _ipv6_header);
VpnPacketTLV VpnPacket::first_tlv() {
return VpnPacketTLV(*this, 0);
}
uint32_t VpnPacket::get_seqno() const {
@ -60,9 +52,9 @@ void VpnPacket::upon_reception() {
}
uint32_t VpnPacket::next_seqno() {
if(_peer)
if(!_peer)
throw PeerNotSet();
return _peer->next_seqno();
return _next_general_seqno++;
}
@ -70,6 +62,10 @@ VpnPacketTLV::VpnPacketTLV(VpnPacket& packet, size_t payload_offset)
: _packet(packet), _tlv_pos(payload_offset)
{}
VpnPacketTLV::VpnPacketTLV(const VpnPacketTLV& other) :
_packet(other._packet), _tlv_pos(other._tlv_pos)
{}
VpnPacketTLV VpnPacketTLV::create(
VpnPacket& packet, VpnPacket::PayloadType type)
{
@ -83,6 +79,15 @@ VpnPacketTLV VpnPacketTLV::create(
return tlv;
}
VpnPacketTLV VpnPacketTLV::next_tlv() {
size_t next_offset = _tlv_pos + get_payload_size();
return VpnPacketTLV(_packet, next_offset);
}
void VpnPacketTLV::seek_next_tlv() {
_tlv_pos = _tlv_pos + VpnPacket::TLV_HEADER_BYTES + get_payload_size();
}
uint16_t VpnPacketTLV::get_payload_size() const {
return *(uint16_t*)(get_data() + 1);
}
@ -111,3 +116,7 @@ TunnelledPacket::TunnelledPacket(const VpnPacketTLV& copy)
TunnelledPacket TunnelledPacket::create(VpnPacket& packet) {
return VpnPacketTLV::create(packet, VpnPacket::PAYLOAD_TYPE_TUNNELLED);
}
bool TunnelledPacket::parse_as_ipv6() {
return parse_ipv6_header(get_payload(), get_payload_size(), _ipv6_header);
}

78
VpnPacket.hpp
View file

@ -29,20 +29,19 @@
*
* Where
* - Type is one of the values from PayloadType below;
* - Sender ID is an arbitrary value, recommended to be randomly chosen
* - Payload size is the size of the payload (excluding headers), in bytes;
* - Payload is an arbitrary value, defined by Type
*/
class VpnPeer;
class VpnPacketTLVIterator;
class VpnPacketTLV;
class VpnPacket {
public:
static const size_t VPN_HEADER_BYTES;
static const size_t TLV_HEADER_BYTES;
typedef VpnPacketTLVIterator iterator;
enum PayloadType {
PAYLOAD_TYPE_UNDEF, ///< Undefined packet type
PAYLOAD_TYPE_TUNNELLED, ///< A tunnelled packet
@ -50,19 +49,15 @@ class VpnPacket {
PAYLOAD_TYPE_REMB, ///< Receiver Estimated Maximum Bitrate
};
class PeerNotSet: public std::exception {};
VpnPacket(size_t mtu);
~VpnPacket();
iterator begin();
iterator end();
VpnPacketTLV first_tlv();
/// Set packet peer -- used for sequence numbers
void set_peer(std::shared_ptr<VpnPeer> peer) { _peer = peer; }
/// Try to parse the packet as IPv6, return `false` upon failure.
bool parse_as_ipv6();
bool ipv6_parsed() const { return _ipv6_parsed; }
const IPv6Header& get_ipv6_header() const { return _ipv6_header; }
void set_peer(VpnPeer* peer) { _peer = peer; }
/// Get a pointer to the packet payload (const version)
const char* get_payload() const { return _data + VPN_HEADER_BYTES; }
@ -117,23 +112,19 @@ class VpnPacket {
inline uint32_t next_seqno();
private:
std::shared_ptr<VpnPeer> _peer;
VpnPeer* _peer; // raw pointer: we do not own the peer in any way
char* _data;
size_t _data_space, _data_size;
bool _ipv6_parsed;
IPv6Header _ipv6_header;
uint32_t _reception_timestamp;
static uint32_t _next_general_seqno;
};
/** Base class for a TLV contained in a VpnPacket */
class VpnPacketTLV {
public:
VpnPacketTLV(VpnPacket& packet, size_t payload_offset);
VpnPacketTLV(const VpnPacketTLV& other);
static VpnPacketTLV create(
VpnPacket& packet,
@ -142,6 +133,15 @@ class VpnPacketTLV {
const VpnPacket& get_packet() const { return _packet; }
VpnPacket& get_packet() { return _packet; }
/// Get the next TLV in this packet.
VpnPacketTLV next_tlv();
/// Point this object to the next TLV (ie. `next_tlv` in place)
void seek_next_tlv();
/// Check whether the current TLV is past the packet's end
bool past_the_end() const {
return _tlv_pos >= _packet.get_payload_size(); }
/// Get the offset in the packet
size_t get_offset() const { return _tlv_pos; }
@ -155,6 +155,11 @@ class VpnPacketTLV {
uint16_t get_payload_size() const;
/// Set the current payload size
void set_payload_size(uint16_t size);
/// Get the total available raw data space
uint16_t get_payload_space() const {
return _packet.get_payload_space()
- _packet.get_payload_size()
- get_payload_size(); }
/// Get a pointer to the raw data (const version)
const char* get_data() const {
@ -185,36 +190,6 @@ class VpnPacketTLV {
friend class TunnelledPacket;
};
/** An iterator over the VpnPacketTLVs of a VpnPacket */
class VpnPacketTLVIterator {
public:
using iterator_category = std::input_iterator_tag;
using value_type = VpnPacketTLV;
using difference_type = ptrdiff_t;
using pointer = VpnPacketTLV*;
using reference = VpnPacketTLV&;
VpnPacketTLVIterator(const VpnPacketTLV& tlv) : _tlv(tlv) {}
VpnPacketTLVIterator& operator++();
VpnPacketTLVIterator operator++(int) {
VpnPacketTLVIterator tmp(*this);
operator++();
return tmp;
}
bool operator==(const VpnPacketTLVIterator& other) {
return _tlv == other._tlv; }
bool operator!=(const VpnPacketTLVIterator& other) {
return !(operator==(other)); }
bool past_the_end() const {
return _tlv.get_offset() >= _tlv.get_packet().get_payload_size(); }
reference operator*() { return _tlv; }
private:
VpnPacketTLV _tlv;
};
/** A packet sent through the VPN tunnel.
*
* This must instantiated just before filling it with data. */
@ -223,4 +198,13 @@ class TunnelledPacket: public VpnPacketTLV {
TunnelledPacket(VpnPacket& packet, size_t payload_offset);
TunnelledPacket(const VpnPacketTLV& copy);
static TunnelledPacket create(VpnPacket& packet);
/// Try to parse the packet as IPv6, return `false` upon failure.
bool parse_as_ipv6();
bool ipv6_parsed() const { return _ipv6_parsed; }
const IPv6Header& get_ipv6_header() const { return _ipv6_header; }
private:
bool _ipv6_parsed;
IPv6Header _ipv6_header;
};

5
VpnPeer.cpp
View file

@ -6,10 +6,13 @@
#include <functional>
VpnPeer::VpnPeer(UdpVpn* vpn, const sockaddr_in6& ext_addr,
const in6_addr int_addr)
const in6_addr& int_addr)
: _vpn(vpn), _ext_addr(ext_addr), _int_addr(int_addr), _next_seqno(0)
{}
void VpnPeer::set_int_addr(const in6_addr& int_addr) {
memcpy(&_int_addr, &int_addr, sizeof(_int_addr));
}
size_t VpnPeer::write(const char* data, size_t len) {
ssize_t nsent;

4
VpnPeer.hpp
View file

@ -20,11 +20,13 @@ class VpnPeer {
};
VpnPeer(UdpVpn* vpn, const sockaddr_in6& ext_addr,
const in6_addr int_addr);
const in6_addr& int_addr);
const sockaddr_in6& get_ext_addr() const { return _ext_addr; }
const in6_addr& get_int_addr() const { return _int_addr; }
void set_int_addr(const in6_addr& int_addr);
size_t write(const char* data, size_t len);
size_t write(const VpnPacket& packet);