rate network conditions

diff --git a/src/net/CongestionControl.hpp b/src/net/CongestionControl.hpp
index 73d1d859ec0aaed8cafdcd8ba448786a7b047e0f..ea71c55abe7c8625a42c31edf48f0fe8e01b2e45 100644 (file)
--- a/src/net/CongestionControl.hpp
+++ b/src/net/CongestionControl.hpp
@@ -9,9 +9,19 @@ namespace blank {
 
 class CongestionControl {
 
+public:
+       enum Mode {
+               GOOD,
+               BAD,
+               UGLY,
+       };
+
 public:
        CongestionControl();
 
+       /// get recommended mode of operation
+       Mode GetMode() const noexcept { return mode; }
+
        /// packet loss as factor
        float PacketLoss() const noexcept { return packet_loss; }
        /// smooth average round trip time in milliseconds
@@ -30,11 +40,19 @@ public:
 
 private:
        void UpdatePacketLoss() noexcept;
+
        void UpdateRTT(std::uint16_t) noexcept;
        bool SamplePacket(std::uint16_t) const noexcept;
-       int HeadDiff(std::uint16_t) const noexcept;
+
        void UpdateStats() noexcept;
 
+       void UpdateMode() noexcept;
+       void CheckUpgrade(Mode) noexcept;
+       void ChangeMode(Mode) noexcept;
+       void KeepMode() noexcept;
+
+       Mode Conditions() const noexcept;
+
 private:
        const unsigned int packet_overhead;
        const unsigned int sample_skip;
@@ -54,6 +72,16 @@ private:
        float tx_kbps;
        float rx_kbps;
 
+       Mode mode;
+       float bad_rtt;
+       float bad_loss;
+       float ugly_rtt;
+       float ugly_loss;
+       Uint32 mode_entered;
+       Uint32 mode_reset;
+       Uint32 mode_keep_time;
+       Uint32 mode_step;
+
 };
 
 }

diff --git a/src/net/net.cpp b/src/net/net.cpp
index 4de800e2429eb4c1c65e4a87ef0ec17567692058..1f4e0a951edd655d08547ad1b4dfad7f696a7503 100644 (file)
--- a/src/net/net.cpp
+++ b/src/net/net.cpp
@@ -47,12 +47,23 @@ CongestionControl::CongestionControl()
 , tx_bytes(0)
 , rx_bytes(0)
 , tx_kbps(0.0f)
-, rx_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 {
@@ -87,7 +98,8 @@ void CongestionControl::UpdatePacketLoss() noexcept {
 
 void CongestionControl::UpdateRTT(std::uint16_t seq) noexcept {
        if (!SamplePacket(seq)) return;
-       int diff = HeadDiff(seq);
+       int16_t diff = int16_t(seq) - int16_t(stamp_last);
+       diff /= sample_skip;
        if (diff > 0 || diff < -15) {
                // packet outside observed time frame
                return;
@@ -100,11 +112,6 @@ bool CongestionControl::SamplePacket(std::uint16_t seq) const noexcept {
        return seq % sample_skip == 0;
 }
 
-int CongestionControl::HeadDiff(std::uint16_t seq) const noexcept {
-       int16_t diff = int16_t(seq) - int16_t(stamp_last);
-       return diff / sample_skip;
-}
-
 void CongestionControl::PacketIn(const UDPpacket &pack) noexcept {
        rx_bytes += pack.len + packet_overhead;
        UpdateStats();
@@ -117,12 +124,71 @@ void CongestionControl::PacketOut(const UDPpacket &pack) noexcept {
 
 void CongestionControl::UpdateStats() noexcept {
        Uint32 now = SDL_GetTicks();
-       if (now >= next_sample) {
-               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;
+       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;
        }
 }