+#include "CongestionControl.hpp"
#include "Connection.hpp"
#include "ConnectionHandler.hpp"
#include "io.hpp"
constexpr size_t Packet::Message::MAX_LEN;
constexpr size_t Packet::Message::MAX_MESSAGE_LEN;
+
+CongestionControl::CongestionControl()
+// I know, I know, it's an estimate (about 20 for IPv4, 48 for IPv6)
+: packet_overhead(20)
+// only sample every eighth packet for measuring RTT
+, sample_skip(8)
+, packets_lost(0)
+, packets_received(0)
+, packet_loss(0.0f)
+, stamp_cursor(15)
+, stamp_last(0)
+, rtt(64.0f)
+, next_sample(1000)
+, tx_bytes(0)
+, rx_bytes(0)
+, tx_kbps(0.0f)
+, rx_kbps(0.0f)
+, mode(GOOD)
+// rtt > 100ms or packet loss > 5% is BAD
+, bad_rtt(100.0f)
+, bad_loss(0.05f)
+// rtt > 250ms or packet loss > 15% is UGLY
+, ugly_rtt(250.0f)
+, ugly_loss(0.15f)
+, mode_keep_time(1000) {
+ Uint32 now = SDL_GetTicks();
+ for (Uint32 &s : stamps) {
+ s = now;
+ }
+ next_sample += now;
+ mode_entered = now;
+ mode_reset = now;
+ mode_step = now;
+}
+
+void CongestionControl::PacketSent(uint16_t seq) noexcept {
+ if (!SamplePacket(seq)) {
+ return;
+ }
+ stamp_cursor = (stamp_cursor + 1) % 16;
+ stamps[stamp_cursor] = SDL_GetTicks();
+ stamp_last = seq;
+}
+
+void CongestionControl::PacketLost(uint16_t seq) noexcept {
+ ++packets_lost;
+ UpdatePacketLoss();
+ UpdateRTT(seq);
+}
+
+void CongestionControl::PacketReceived(uint16_t seq) noexcept {
+ ++packets_received;
+ UpdatePacketLoss();
+ UpdateRTT(seq);
+}
+
+void CongestionControl::UpdatePacketLoss() noexcept {
+ unsigned int packets_total = packets_lost + packets_received;
+ if (packets_total >= 256) {
+ packet_loss = float(packets_lost) / float(packets_total);
+ packets_lost = 0;
+ packets_received = 0;
+ }
+}
+
+void CongestionControl::UpdateRTT(std::uint16_t seq) noexcept {
+ if (!SamplePacket(seq)) return;
+ int16_t diff = int16_t(seq) - int16_t(stamp_last);
+ diff /= sample_skip;
+ if (diff > 0 || diff < -15) {
+ // packet outside observed time frame
+ return;
+ }
+ int cur_rtt = SDL_GetTicks() - stamps[(stamp_cursor + diff + 16) % 16];
+ rtt += (cur_rtt - rtt) * 0.1f;
+}
+
+bool CongestionControl::SamplePacket(std::uint16_t seq) const noexcept {
+ return seq % sample_skip == 0;
+}
+
+void CongestionControl::PacketIn(const UDPpacket &pack) noexcept {
+ rx_bytes += pack.len + packet_overhead;
+ UpdateStats();
+}
+
+void CongestionControl::PacketOut(const UDPpacket &pack) noexcept {
+ tx_bytes += pack.len + packet_overhead;
+ UpdateStats();
+}
+
+void CongestionControl::UpdateStats() noexcept {
+ Uint32 now = SDL_GetTicks();
+ if (now < next_sample) {
+ // not yet
+ return;
+ }
+ tx_kbps = float(tx_bytes) * (1.0f / 1024.0f);
+ rx_kbps = float(rx_bytes) * (1.0f / 1024.0f);
+ tx_bytes = 0;
+ rx_bytes = 0;
+ next_sample += 1000;
+ UpdateMode();
+}
+
+void CongestionControl::UpdateMode() noexcept {
+ Mode now_mode = Conditions();
+ if (now_mode > mode) {
+ ChangeMode(now_mode);
+ } else if (now_mode < mode) {
+ CheckUpgrade(now_mode);
+ } else {
+ KeepMode();
+ }
+}
+
+void CongestionControl::CheckUpgrade(Mode m) noexcept {
+ Uint32 now = SDL_GetTicks();
+ Uint32 time_in_mode = now - mode_entered;
+ if (time_in_mode < mode_keep_time) {
+ return;
+ }
+ ChangeMode(m);
+}
+
+void CongestionControl::ChangeMode(Mode m) noexcept {
+ Uint32 now = SDL_GetTicks();
+ if (m > mode) {
+ // changed to worse mode
+ // if we spent less than 10 seconds in better mode
+ // double keep time till up to 64 seconds
+ if (now - mode_entered < 10000) {
+ if (mode_keep_time < 64000) {
+ mode_keep_time *= 2;
+ }
+ }
+ }
+ mode = m;
+ mode_entered = now;
+ mode_reset = mode_entered;
+}
+
+void CongestionControl::KeepMode() noexcept {
+ mode_reset = SDL_GetTicks();
+ // if in good mode for 10 seconds, halve keep time till down to one second
+ if (mode == GOOD && mode_keep_time > 1000 && mode_step - mode_reset > 10000) {
+ mode_keep_time /= 2;
+ mode_step = mode_reset;
+ }
+}
+
+CongestionControl::Mode CongestionControl::Conditions() const noexcept {
+ if (rtt > ugly_rtt || packet_loss > ugly_loss) {
+ return UGLY;
+ } else if (rtt > bad_rtt || packet_loss > bad_loss) {
+ return BAD;
+ } else {
+ return GOOD;
+ }
+}
+
+
Connection::Connection(const IPaddress &addr)
: handler(nullptr)
, addr(addr)
throw NetError("SDLNet_UDP_Send");
}
+ if (HasHandler()) {
+ Handler().PacketOut(udp_pack);
+ Handler().PacketSent(seq);
+ }
+
FlagSend();
return seq;
}
}
Packet::TControl ctrl_new = pack.header.ctrl;
+ Handler().PacketIn(udp_pack);
Handler().Handle(udp_pack);
if (diff > 0) {
ConnectionHandler::ConnectionHandler()
-: packets_lost(0)
-, packets_received(0)
-, packet_loss(0.0f) {
+: cc() {
}
+void ConnectionHandler::PacketSent(uint16_t seq) noexcept {
+ cc.PacketSent(seq);
+}
+
void ConnectionHandler::PacketLost(uint16_t seq) {
OnPacketLost(seq);
- ++packets_lost;
- UpdatePacketLoss();
+ cc.PacketLost(seq);
}
void ConnectionHandler::PacketReceived(uint16_t seq) {
OnPacketReceived(seq);
- ++packets_received;
- UpdatePacketLoss();
+ cc.PacketReceived(seq);
}
-void ConnectionHandler::UpdatePacketLoss() noexcept {
- unsigned int packets_total = packets_lost + packets_received;
- if (packets_total >= 256) {
- packet_loss = float(packets_lost) / float(packets_total);
- packets_lost = 0;
- packets_received = 0;
- }
+void ConnectionHandler::PacketIn(const UDPpacket &pack) noexcept {
+ cc.PacketIn(pack);
+}
+
+void ConnectionHandler::PacketOut(const UDPpacket &pack) noexcept {
+ cc.PacketOut(pack);
}
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