Implement an event-based simulator for QuicConnection

net/quic/core/congestion_control/simulation/switch.cc

+#include <cinttypes>
+
+#include "base/port.h"
+#include "base/stringprintf.h"
+#include "net/quic/core/congestion_control/simulation/switch.h"
+#include "util/gtl/ptr_util.h"
+
+namespace net {
+namespace simulation {
+
+Switch::Switch(Simulator* simulator,
+               std::string name,
+               SwitchPortNumber port_count,
+               QuicByteCount queue_capacity) {
+  for (size_t port_number = 1; port_number <= port_count; port_number++) {
+    ports_.emplace_back(simulator, StringPrintf("%s (port %" PRIuS ")",
+                                                name.c_str(), port_number),
+                        this, port_number, queue_capacity);
+  }
+}
+
+Switch::Port::Port(Simulator* simulator,
+                   std::string name,
+                   Switch* parent,
+                   SwitchPortNumber port_number,
+                   QuicByteCount queue_capacity)
+    : Endpoint(simulator, name),
+      parent_(parent),
+      port_number_(port_number),
+      connected_(false),
+      queue_(simulator,
+             StringPrintf("%s (queue)", name.c_str()),
+             queue_capacity) {}
+
+void Switch::Port::AcceptPacket(std::unique_ptr<Packet> packet) {
+  parent_->DispatchPacket(port_number_, std::move(packet));
+}
+
+void Switch::Port::EnqueuePacket(std::unique_ptr<Packet> packet) {
+  queue_.AcceptPacket(std::move(packet));
+}
+
+UnconstrainedPortInterface* Switch::Port::GetRxPort() {
+  return this;
+}
+
+void Switch::Port::SetTxPort(ConstrainedPortInterface* port) {
+  queue_.set_tx_port(port);
+  connected_ = true;
+}
+
+void Switch::Port::Act() {}
+
+void Switch::DispatchPacket(SwitchPortNumber port_number,
+                            std::unique_ptr<Packet> packet) {
+  Port* source_port = &ports_[port_number - 1];
+  const auto source_mapping_it = switching_table_.find(packet->source);
+  if (source_mapping_it == switching_table_.end()) {
+    switching_table_.emplace(packet->source, source_port);
+  }
+
+  const auto destination_mapping_it =
+      switching_table_.find(packet->destination);
+  if (destination_mapping_it != switching_table_.end()) {
+    destination_mapping_it->second->EnqueuePacket(std::move(packet));
+    return;
+  }
+
+  // If no mapping is available yet, broadcast the packet to all ports
+  // different from the source.
+  for (Port& egress_port : ports_) {
+    if (!egress_port.connected()) {
+      continue;
+    }
+    egress_port.EnqueuePacket(gtl::MakeUnique<Packet>(*packet));
+  }
+}
+
+}  // namespace simulation
+}  // namespace net