congestvpn/VpnPacket.cpp

#include "VpnPacket.hpp"
#include "VpnPeer.hpp"

#include <cstring>

const size_t VpnPacket::VPN_HEADER_BYTES = 8;
const size_t VpnControlPacket::TLV_HEADER_BYTES = 3;

static const size_t OUTER_HEADERS_BYTES =
    40 /* IPv6 header */ + 8 /* UDP header */;
    // We use a TUN device, hence we don't have a layer 2 header.

static const int
    DATA_SEQNO_POS = 0,
    DATA_CTRLBIT_POS = 4,
    DATA_TIMESTAMP_POS = 4;

VpnPacket::VpnPacket(size_t mtu, bool inbound)
    : _peer(nullptr), _inbound(inbound), _data_space(mtu-OUTER_HEADERS_BYTES),
      _data_size(VPN_HEADER_BYTES), _reception_timestamp(0)
{
    _data = std::unique_ptr<char[]>(new char[mtu - OUTER_HEADERS_BYTES]);
}

VpnPacket::~VpnPacket() {}

VpnPacket::VpnPacket(VpnPacket&& move_from) :
    _peer(move_from._peer),
    _inbound(move_from._inbound),
    _data(std::move(move_from._data)),
    _data_space(move_from._data_space),
    _data_size(move_from._data_size),
    _reception_timestamp(move_from._reception_timestamp)
{}

size_t VpnPacket::get_tunnelled_mtu(size_t udp_mtu) {
    return udp_mtu - OUTER_HEADERS_BYTES - VPN_HEADER_BYTES;
}

void VpnPacket::set_peer(VpnPeer* peer) {
    _peer = peer;
    if(_peer && _inbound)
        _peer->got_inbound_packet(*this);
}

uint32_t VpnPacket::get_seqno() const {
    return ntohl(*(uint32_t*)(_data.get() + DATA_SEQNO_POS));
}

uint32_t VpnPacket::get_sending_timestamp() const {
    return ntohl(
            *(uint32_t*)(_data.get() + DATA_TIMESTAMP_POS) & 0x7fffffffUL
            );
}

bool VpnPacket::is_control() const {
    return *(unsigned char*)(_data.get() + DATA_CTRLBIT_POS) & 0x80;
}

void VpnPacket::set_control(bool is_control) {
    unsigned char* ctrl_field =
        (unsigned char*) (_data.get() + DATA_CTRLBIT_POS);
    *ctrl_field &= 0x7f;
    if(is_control)
        *ctrl_field |= 0x80;
}

void VpnPacket::prepare_for_sending() {
    uint32_t* ts_field = (uint32_t*) (_data.get() + DATA_TIMESTAMP_POS);
    *ts_field &= htonl(0x80000000UL);
    *(uint32_t*)(_data.get() + DATA_SEQNO_POS) = htonl(next_seqno());
    *ts_field |= htonl(to_us_timestamp(current_us_timestamp()));
}

void VpnPacket::upon_reception() {
    _reception_timestamp = to_us_timestamp(current_us_timestamp());
}

uint32_t VpnPacket::next_seqno() {
    if(!_peer)
        throw PeerNotSet();
    return _peer->next_seqno();
}

VpnControlPacket::VpnControlPacket(size_t mtu, bool inbound)
    : VpnPacket(mtu, inbound)
{
    set_control(true);
}

VpnControlPacket::VpnControlPacket(VpnPacket&& move_from)
    : VpnPacket(std::move(move_from))
{}

VpnPacketTLV VpnControlPacket::first_tlv() {
    return VpnPacketTLV(*this, 0);
}

VpnDataPacket::VpnDataPacket(size_t mtu, bool inbound)
    : VpnPacket(mtu, inbound), _ipv6_parsed(false)
{
    set_control(false);
}

VpnDataPacket::VpnDataPacket(VpnPacket&& move_from)
    : VpnPacket(std::move(move_from)), _ipv6_parsed(false)
{}

bool VpnDataPacket::parse_as_ipv6(bool reparse) {
    if(_ipv6_parsed && !reparse)
        return true;

    _ipv6_parsed =
        parse_ipv6_header(get_payload(), get_payload_size(), _ipv6_header);
    return _ipv6_parsed;
}

VpnPacketTLV::VpnPacketTLV(VpnControlPacket& 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(
        VpnControlPacket& packet, VpnPacketTLV::PayloadType type)
{
    VpnPacketTLV tlv = VpnPacketTLV(packet, packet.get_payload_size());
    packet.increase_payload_size(VpnControlPacket::TLV_HEADER_BYTES);

    char* data = tlv.get_data();
    data[0] = type;
    *(uint16_t*)(data+1) = 0; // Set len to 0

    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 + VpnControlPacket::TLV_HEADER_BYTES + get_payload_size();
}

uint16_t VpnPacketTLV::get_payload_size() const {
    return *(uint16_t*)(get_data() + 1);
}
void VpnPacketTLV::set_payload_size(uint16_t size) {
    uint16_t* data_size_ptr = (uint16_t*)(get_data() + 1);
    uint16_t old_size = *data_size_ptr;
    *data_size_ptr = size;
    _packet.increase_payload_size(size - old_size);
}

uint16_t VpnPacketTLV::get_payload_space() const {
    return _packet.get_payload_space()
        - _packet.get_payload_size()
        + get_payload_size();
}

VpnPacketTLV::PayloadType VpnPacketTLV::get_type() const {
    return (PayloadType)(*(uint8_t*)(get_data()));
}
void VpnPacketTLV::set_type(VpnPacketTLV::PayloadType type) {
    *(uint8_t*)(get_data()) = (uint8_t) type;
}

/* ========== VpnTlvLossReport ========== */
const uint32_t VpnTlvLossReport::REP_SEQNO_POS = 0,
      VpnTlvLossReport::REP_LOSS_POS = 4;

VpnTlvLossReport::VpnTlvLossReport(
        VpnControlPacket& packet, size_t payload_offset)
    : VpnPacketTLV(packet, payload_offset) {}
VpnTlvLossReport::VpnTlvLossReport(const VpnPacketTLV& other)
    : VpnPacketTLV(other) {}

VpnTlvLossReport VpnTlvLossReport::create(VpnControlPacket& packet) {
    VpnTlvLossReport tlv =
        VpnPacketTLV::create(packet, VpnPacketTLV::PAYLOAD_TYPE_LOSS_REPORT);
    tlv.set_payload_size(8);
    memset(tlv.get_payload(), 0, 8);
    return tlv;
}

uint32_t VpnTlvLossReport::get_report_seqno() const {
    return ntohl(*(uint32_t*)(get_payload() + REP_SEQNO_POS));
}
void VpnTlvLossReport::set_report_seqno(uint32_t seqno) {
    *(uint32_t*)(get_payload() + REP_SEQNO_POS) = htonl(seqno);
}
uint32_t VpnTlvLossReport::get_losses() const {
    return ntohl(*(uint32_t*)(get_payload() + REP_LOSS_POS));
}
void VpnTlvLossReport::set_losses(uint32_t losses) {
    *(uint32_t*)(get_payload() + REP_LOSS_POS) = htonl(losses);
}

/* ========== VpnTlvRTTQ ========== */
VpnTlvRTTQ::VpnTlvRTTQ(VpnControlPacket& packet, size_t payload_offset)
    : VpnPacketTLV(packet, payload_offset) {}
VpnTlvRTTQ::VpnTlvRTTQ(const VpnPacketTLV& other)
    : VpnPacketTLV(other) {}

VpnTlvRTTQ VpnTlvRTTQ::create(VpnControlPacket& packet) {
    return VpnPacketTLV::create(packet, VpnPacketTLV::PAYLOAD_TYPE_RTTQ);
}

/* ========== VpnTlvRTTA ========== */
const uint32_t VpnTlvRTTA::EXP_TS_POS = 0, VpnTlvRTTA::RECV_TS_POS = 4;

VpnTlvRTTA::VpnTlvRTTA(VpnControlPacket& packet, size_t payload_offset)
    : VpnPacketTLV(packet, payload_offset) {}
VpnTlvRTTA::VpnTlvRTTA(const VpnPacketTLV& other)
    : VpnPacketTLV(other) {}

VpnTlvRTTA VpnTlvRTTA::create(VpnControlPacket& packet) {
    VpnTlvRTTA tlv =
        VpnPacketTLV::create(packet, VpnPacketTLV::PAYLOAD_TYPE_RTTA);
    tlv.set_payload_size(8);
    memset(tlv.get_payload(), 0, 8);
    return tlv;
}

uint32_t VpnTlvRTTA::get_exp_ts() const {
    return ntohl(*(uint32_t*)(get_payload() + EXP_TS_POS));
}
void VpnTlvRTTA::set_exp_ts(uint32_t ts) {
    *(uint32_t*)(get_payload() + EXP_TS_POS) = htonl(ts);
}

uint32_t VpnTlvRTTA::get_recv_ts() const {
    return ntohl(*(uint32_t*)(get_payload() + RECV_TS_POS));
}
void VpnTlvRTTA::set_recv_ts(uint32_t ts) {
    *(uint32_t*)(get_payload() + RECV_TS_POS) = htonl(ts);
}