blob: 373239344fd71bd60215297b756d977fd2ee7a01 [file] [log] [blame]
// Copyright (c) 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "quiche/quic/core/quic_mtu_discovery.h"
#include "quiche/quic/platform/api/quic_flag_utils.h"
#include "quiche/quic/platform/api/quic_stack_trace.h"
namespace quic {
QuicConnectionMtuDiscoverer::QuicConnectionMtuDiscoverer(
QuicPacketCount packets_between_probes_base, QuicPacketNumber next_probe_at)
: packets_between_probes_(packets_between_probes_base),
next_probe_at_(next_probe_at) {}
void QuicConnectionMtuDiscoverer::Enable(
QuicByteCount max_packet_length, QuicByteCount target_max_packet_length) {
QUICHE_DCHECK(!IsEnabled());
if (target_max_packet_length <= max_packet_length) {
QUIC_DVLOG(1) << "MtuDiscoverer not enabled. target_max_packet_length:"
<< target_max_packet_length
<< " <= max_packet_length:" << max_packet_length;
return;
}
min_probe_length_ = max_packet_length;
max_probe_length_ = target_max_packet_length;
QUICHE_DCHECK(IsEnabled());
QUIC_DVLOG(1) << "MtuDiscoverer enabled. min:" << min_probe_length_
<< ", max:" << max_probe_length_
<< ", next:" << next_probe_packet_length();
}
void QuicConnectionMtuDiscoverer::Disable() {
*this = QuicConnectionMtuDiscoverer(packets_between_probes_, next_probe_at_);
}
bool QuicConnectionMtuDiscoverer::IsEnabled() const {
return min_probe_length_ < max_probe_length_;
}
bool QuicConnectionMtuDiscoverer::ShouldProbeMtu(
QuicPacketNumber largest_sent_packet) const {
if (!IsEnabled()) {
return false;
}
if (remaining_probe_count_ == 0) {
QUIC_DVLOG(1)
<< "ShouldProbeMtu returns false because max probe count reached";
return false;
}
if (largest_sent_packet < next_probe_at_) {
QUIC_DVLOG(1) << "ShouldProbeMtu returns false because not enough packets "
"sent since last probe. largest_sent_packet:"
<< largest_sent_packet
<< ", next_probe_at_:" << next_probe_at_;
return false;
}
QUIC_DVLOG(1) << "ShouldProbeMtu returns true. largest_sent_packet:"
<< largest_sent_packet;
return true;
}
QuicPacketLength QuicConnectionMtuDiscoverer::GetUpdatedMtuProbeSize(
QuicPacketNumber largest_sent_packet) {
QUICHE_DCHECK(ShouldProbeMtu(largest_sent_packet));
QuicPacketLength probe_packet_length = next_probe_packet_length();
if (probe_packet_length == last_probe_length_) {
// The next probe packet is as big as the previous one. Assuming the
// previous one exceeded MTU, we need to decrease the probe packet length.
max_probe_length_ = probe_packet_length;
} else {
QUICHE_DCHECK_GT(probe_packet_length, last_probe_length_);
}
last_probe_length_ = next_probe_packet_length();
packets_between_probes_ *= 2;
next_probe_at_ = largest_sent_packet + packets_between_probes_ + 1;
if (remaining_probe_count_ > 0) {
--remaining_probe_count_;
}
QUIC_DVLOG(1) << "GetUpdatedMtuProbeSize: probe_packet_length:"
<< last_probe_length_
<< ", New packets_between_probes_:" << packets_between_probes_
<< ", next_probe_at_:" << next_probe_at_
<< ", remaining_probe_count_:" << remaining_probe_count_;
QUICHE_DCHECK(!ShouldProbeMtu(largest_sent_packet));
return last_probe_length_;
}
QuicPacketLength QuicConnectionMtuDiscoverer::next_probe_packet_length() const {
QUICHE_DCHECK_NE(min_probe_length_, 0);
QUICHE_DCHECK_NE(max_probe_length_, 0);
QUICHE_DCHECK_GE(max_probe_length_, min_probe_length_);
const QuicPacketLength normal_next_probe_length =
(min_probe_length_ + max_probe_length_ + 1) / 2;
if (remaining_probe_count_ == 1 &&
normal_next_probe_length > last_probe_length_) {
// If the previous probe succeeded, and there is only one last probe to
// send, use |max_probe_length_| for the last probe.
return max_probe_length_;
}
return normal_next_probe_length;
}
void QuicConnectionMtuDiscoverer::OnMaxPacketLengthUpdated(
QuicByteCount old_value, QuicByteCount new_value) {
if (!IsEnabled() || new_value <= old_value) {
return;
}
QUICHE_DCHECK_EQ(old_value, min_probe_length_);
min_probe_length_ = new_value;
}
std::ostream& operator<<(std::ostream& os,
const QuicConnectionMtuDiscoverer& d) {
os << "{ min_probe_length_:" << d.min_probe_length_
<< " max_probe_length_:" << d.max_probe_length_
<< " last_probe_length_:" << d.last_probe_length_
<< " remaining_probe_count_:" << d.remaining_probe_count_
<< " packets_between_probes_:" << d.packets_between_probes_
<< " next_probe_at_:" << d.next_probe_at_ << " }";
return os;
}
} // namespace quic