tcp: Updated RTTM to use float instead of double, edited clock gran

Author: AndreasAakesson

api/net/tcp/common.hpp

@@ -39,7 +39,7 @@ namespace net {
     // the maximum amount of half-open connections per port (listener)
     static constexpr size_t   default_max_syn_backlog {64};
     // clock granularity of the timestamp value clock
-    static constexpr double   clock_granularity {0.0001};
+    static constexpr float   clock_granularity {0.0001};
 
     static const std::chrono::seconds       default_msl {30};
     static const std::chrono::milliseconds  default_dack_timeout {40};

api/net/tcp/rttm.hpp

@@ -32,14 +32,14 @@ namespace tcp {
 // TODO: Appendix G.  RTO Calculation Modification https://tools.ietf.org/html/rfc7323#appendix-G
 struct RTTM {
   using milliseconds = std::chrono::milliseconds;
-  using seconds      = std::chrono::duration<double>; // seconds as double
+  using seconds      = std::chrono::duration<float>; // seconds as float
 
   // clock granularity
-  static constexpr double CLOCK_G {clock_granularity};
+  static constexpr float CLOCK_G {clock_granularity};
 
-  static constexpr double K = 4.0;
-  static constexpr double alpha = 1.0 / 8.0;
-  static constexpr double beta  = 1.0 / 4.0;
+  static constexpr float K = 4.0;
+  static constexpr float alpha = 1.0 / 8.0;
+  static constexpr float beta  = 1.0 / 4.0;
 
   seconds       SRTT;     // smoothed round-trip time
   seconds       RTTVAR;   // round-trip time variation
@@ -112,7 +112,7 @@ struct RTTM {
   // 1. A multiplier member could be added to be used for "backing off" the timer (return compute_rto() * multiplier).
   // 2. Dunno how to set RTO = 3s when timeout on ACK for SYN.
   seconds compute_rto() const
-  { return seconds{std::max(SRTT.count() + std::max(CLOCK_G, K * RTTVAR.count()), 1.0)}; }
+  { return seconds{std::max(SRTT.count() + std::max(CLOCK_G, K * RTTVAR.count()), 1.0f)}; }
 
   /**
    * @brief      Take a RTT (Round trip time) measurment

src/net/tcp/rttm.cpp

@@ -19,10 +19,10 @@
 
 using namespace net::tcp;
 
-constexpr double RTTM::CLOCK_G;
-constexpr double RTTM::K;
-constexpr double RTTM::alpha;
-constexpr double RTTM::beta;
+constexpr float RTTM::CLOCK_G;
+constexpr float RTTM::K;
+constexpr float RTTM::alpha;
+constexpr float RTTM::beta;
 
 /*
   When the first RTT measurement R is made, the host MUST set