1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "quiche/quic/test_tools/simulator/link.h"
6
7 #include "absl/strings/str_cat.h"
8 #include "absl/strings/str_format.h"
9 #include "quiche/quic/test_tools/simulator/simulator.h"
10
11 namespace quic {
12 namespace simulator {
13
14 // Parameters for random noise delay.
15 const uint64_t kMaxRandomDelayUs = 10;
16
OneWayLink(Simulator * simulator,std::string name,UnconstrainedPortInterface * sink,QuicBandwidth bandwidth,QuicTime::Delta propagation_delay)17 OneWayLink::OneWayLink(Simulator* simulator, std::string name,
18 UnconstrainedPortInterface* sink,
19 QuicBandwidth bandwidth,
20 QuicTime::Delta propagation_delay)
21 : Actor(simulator, name),
22 sink_(sink),
23 bandwidth_(bandwidth),
24 propagation_delay_(propagation_delay),
25 next_write_at_(QuicTime::Zero()) {}
26
~OneWayLink()27 OneWayLink::~OneWayLink() {}
28
QueuedPacket(std::unique_ptr<Packet> packet,QuicTime dequeue_time)29 OneWayLink::QueuedPacket::QueuedPacket(std::unique_ptr<Packet> packet,
30 QuicTime dequeue_time)
31 : packet(std::move(packet)), dequeue_time(dequeue_time) {}
32
33 OneWayLink::QueuedPacket::QueuedPacket(QueuedPacket&& other) = default;
34
~QueuedPacket()35 OneWayLink::QueuedPacket::~QueuedPacket() {}
36
AcceptPacket(std::unique_ptr<Packet> packet)37 void OneWayLink::AcceptPacket(std::unique_ptr<Packet> packet) {
38 QUICHE_DCHECK(TimeUntilAvailable().IsZero());
39 QuicTime::Delta transfer_time = bandwidth_.TransferTime(packet->size);
40 next_write_at_ = clock_->Now() + transfer_time;
41
42 packets_in_transit_.emplace_back(
43 std::move(packet),
44 // Ensure that packets are delivered in order.
45 std::max(
46 next_write_at_ + propagation_delay_ + GetRandomDelay(transfer_time),
47 packets_in_transit_.empty()
48 ? QuicTime::Zero()
49 : packets_in_transit_.back().dequeue_time));
50 ScheduleNextPacketDeparture();
51 }
52
TimeUntilAvailable()53 QuicTime::Delta OneWayLink::TimeUntilAvailable() {
54 const QuicTime now = clock_->Now();
55 if (next_write_at_ <= now) {
56 return QuicTime::Delta::Zero();
57 }
58
59 return next_write_at_ - now;
60 }
61
Act()62 void OneWayLink::Act() {
63 QUICHE_DCHECK(!packets_in_transit_.empty());
64 QUICHE_DCHECK(packets_in_transit_.front().dequeue_time >= clock_->Now());
65
66 sink_->AcceptPacket(std::move(packets_in_transit_.front().packet));
67 packets_in_transit_.pop_front();
68
69 ScheduleNextPacketDeparture();
70 }
71
ScheduleNextPacketDeparture()72 void OneWayLink::ScheduleNextPacketDeparture() {
73 if (packets_in_transit_.empty()) {
74 return;
75 }
76
77 Schedule(packets_in_transit_.front().dequeue_time);
78 }
79
GetRandomDelay(QuicTime::Delta transfer_time)80 QuicTime::Delta OneWayLink::GetRandomDelay(QuicTime::Delta transfer_time) {
81 if (!simulator_->enable_random_delays()) {
82 return QuicTime::Delta::Zero();
83 }
84
85 QuicTime::Delta delta = QuicTime::Delta::FromMicroseconds(
86 simulator_->GetRandomGenerator()->RandUint64() % (kMaxRandomDelayUs + 1));
87 // Have an upper bound on the delay to ensure packets do not go out of order.
88 delta = std::min(delta, transfer_time * 0.5);
89 return delta;
90 }
91
SymmetricLink(Simulator * simulator,std::string name,UnconstrainedPortInterface * sink_a,UnconstrainedPortInterface * sink_b,QuicBandwidth bandwidth,QuicTime::Delta propagation_delay)92 SymmetricLink::SymmetricLink(Simulator* simulator, std::string name,
93 UnconstrainedPortInterface* sink_a,
94 UnconstrainedPortInterface* sink_b,
95 QuicBandwidth bandwidth,
96 QuicTime::Delta propagation_delay)
97 : a_to_b_link_(simulator, absl::StrCat(name, " (A-to-B)"), sink_b,
98 bandwidth, propagation_delay),
99 b_to_a_link_(simulator, absl::StrCat(name, " (B-to-A)"), sink_a,
100 bandwidth, propagation_delay) {}
101
SymmetricLink(Endpoint * endpoint_a,Endpoint * endpoint_b,QuicBandwidth bandwidth,QuicTime::Delta propagation_delay)102 SymmetricLink::SymmetricLink(Endpoint* endpoint_a, Endpoint* endpoint_b,
103 QuicBandwidth bandwidth,
104 QuicTime::Delta propagation_delay)
105 : SymmetricLink(endpoint_a->simulator(),
106 absl::StrFormat("Link [%s]<->[%s]", endpoint_a->name(),
107 endpoint_b->name()),
108 endpoint_a->GetRxPort(), endpoint_b->GetRxPort(), bandwidth,
109 propagation_delay) {
110 endpoint_a->SetTxPort(&a_to_b_link_);
111 endpoint_b->SetTxPort(&b_to_a_link_);
112 }
113
114 } // namespace simulator
115 } // namespace quic
116