tcp: minor changes to window scaling

Author: alfreb

api/net/tcp/common.hpp

@@ -32,7 +32,7 @@ namespace net {
     // default size of TCP window - how much data can be "in flight" (unacknowledged)
     static constexpr uint16_t default_window_size {0xffff};
     // window scaling + window size
-    static constexpr uint8_t  default_window_scaling {5};
+    static constexpr uint8_t  default_window_scaling {7};
     static constexpr uint32_t default_ws_window_size {8192 << default_window_scaling};
     // use of timestamps option
     static constexpr bool     default_timestamps {true};

src/net/tcp/connection.cpp

@@ -323,10 +323,10 @@ Packet_view_ptr Connection::create_outgoing_packet()
   packet->set_source(local_);
   // Set Destination (remote)
   packet->set_destination(remote_);
+  uint32_t shifted = std::min<uint32_t>((cb.RCV.WND >> cb.RCV.wind_shift), default_window_size);
+  Ensures(shifted <= 0xffff);
 
-  const auto recv_wnd = recv_wnd_getter();
-  //printf("recv_wnd %u\n", recv_wnd);
-  packet->set_win(cb.RCV.WND >> cb.RCV.wind_shift);
+  packet->set_win(shifted);
 
   if(cb.SND.TS_OK)
     packet->add_tcp_option_aligned<Option::opt_ts_align>(host_.get_ts_value(), cb.get_ts_recent());
@@ -691,8 +691,9 @@ void Connection::recv_data(const Packet_view& in)
   // since it could be that we already preallocated that memory in our vector.
   // i also think we shouldn't reach this point due to State::check_seq checking
   // if we're inside the window. if packet is out of order tho we can change the RCV wnd (i think).
-  if(recv_wnd_getter() == 0)
+  if(recv_wnd_getter() == 0) {
     drop(in, Drop_reason::RCV_WND_ZERO);
+  }
 
 
   // Keep track if a packet is being sent during the async read callback

src/net/tcp/tcp.cpp

@@ -30,6 +30,8 @@
 #include <net/tcp/packet4_view.hpp>
 #include <net/tcp/packet6_view.hpp>
 #include <kernel/os.hpp>
+#include <util/bitops.hpp>
+#include <util/units.hpp>
 
 using namespace std;
 using namespace net;
@@ -375,11 +377,19 @@ void TCP::reset_pmtu(Socket dest, IP4::PMTU pmtu) {
 
 uint32_t TCP::global_recv_wnd()
 {
-  // 80% of free mem
-  // normalize to 0 to avoid negative value (???)
-  ssize_t avail = std::max<ssize_t>((static_cast<ssize_t>(OS::heap_avail()) * 80 / 100) / 2, 0);
-  //printf("heap: %zi avail: %zu\n", (ssize_t)OS::heap_avail(), avail);
-  return std::min<size_t>(avail, (1 << 30)); // max can only be 1GB
+  using namespace util;
+
+  auto max_use = OS::heap_max() / 4; // TODO: make proportion into variable
+  auto in_use  = OS::heap_usage();
+
+  if (in_use >= max_use) {
+    printf("global_recv_wnd: Receive window empty. Heap use: %zu \n", in_use);
+    return 0;
+  }
+
+  ssize_t buf_avail = max_use - in_use;
+
+  return std::min<size_t>(buf_avail, 4_MiB);
 }
 
 void TCP::transmit(tcp::Packet_view_ptr packet)
@@ -615,6 +625,3 @@ TCP::Listeners::const_iterator TCP::cfind_listener(const Socket& socket) const
 
   return it;
 }
-
-
-