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/*
* Copyright 2019 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "p2p/base/basic_ice_controller.h"
namespace {
// The minimum improvement in RTT that justifies a switch.
const int kMinImprovement = 10;
bool IsRelayRelay(const cricket::Connection* conn) {
return conn->local_candidate().is_relay() &&
conn->remote_candidate().is_relay();
}
bool IsUdp(const cricket::Connection* conn) {
return conn->local_candidate().relay_protocol() == cricket::UDP_PROTOCOL_NAME;
}
// TODO(qingsi) Use an enum to replace the following constants for all
// comparision results.
static constexpr int a_is_better = 1;
static constexpr int b_is_better = -1;
static constexpr int a_and_b_equal = 0;
bool LocalCandidateUsesPreferredNetwork(
const cricket::Connection* conn,
std::optional<rtc::AdapterType> network_preference) {
rtc::AdapterType network_type = conn->network()->type();
return network_preference.has_value() && (network_type == network_preference);
}
int CompareCandidatePairsByNetworkPreference(
const cricket::Connection* a,
const cricket::Connection* b,
std::optional<rtc::AdapterType> network_preference) {
bool a_uses_preferred_network =
LocalCandidateUsesPreferredNetwork(a, network_preference);
bool b_uses_preferred_network =
LocalCandidateUsesPreferredNetwork(b, network_preference);
if (a_uses_preferred_network && !b_uses_preferred_network) {
return a_is_better;
} else if (!a_uses_preferred_network && b_uses_preferred_network) {
return b_is_better;
}
return a_and_b_equal;
}
} // namespace
namespace cricket {
BasicIceController::BasicIceController(const IceControllerFactoryArgs& args)
: ice_transport_state_func_(args.ice_transport_state_func),
ice_role_func_(args.ice_role_func),
is_connection_pruned_func_(args.is_connection_pruned_func),
field_trials_(args.ice_field_trials) {}
BasicIceController::~BasicIceController() {}
void BasicIceController::SetIceConfig(const IceConfig& config) {
config_ = config;
}
void BasicIceController::SetSelectedConnection(
const Connection* selected_connection) {
selected_connection_ = selected_connection;
}
void BasicIceController::AddConnection(const Connection* connection) {
connections_.push_back(connection);
unpinged_connections_.insert(connection);
}
void BasicIceController::OnConnectionDestroyed(const Connection* connection) {
pinged_connections_.erase(connection);
unpinged_connections_.erase(connection);
connections_.erase(absl::c_find(connections_, connection));
if (selected_connection_ == connection)
selected_connection_ = nullptr;
}
bool BasicIceController::HasPingableConnection() const {
int64_t now = rtc::TimeMillis();
return absl::c_any_of(connections_, [this, now](const Connection* c) {
return IsPingable(c, now);
});
}
IceControllerInterface::PingResult BasicIceController::SelectConnectionToPing(
int64_t last_ping_sent_ms) {
// When the selected connection is not receiving or not writable, or any
// active connection has not been pinged enough times, use the weak ping
// interval.
bool need_more_pings_at_weak_interval =
absl::c_any_of(connections_, [](const Connection* conn) {
return conn->active() &&
conn->num_pings_sent() < MIN_PINGS_AT_WEAK_PING_INTERVAL;
});
int ping_interval = (weak() || need_more_pings_at_weak_interval)
? weak_ping_interval()
: strong_ping_interval();
const Connection* conn = nullptr;
if (rtc::TimeMillis() >= last_ping_sent_ms + ping_interval) {
conn = FindNextPingableConnection();
}
PingResult res(conn, std::min(ping_interval, check_receiving_interval()));
return res;
}
void BasicIceController::MarkConnectionPinged(const Connection* conn) {
if (conn && pinged_connections_.insert(conn).second) {
unpinged_connections_.erase(conn);
}
}
// Returns the next pingable connection to ping.
const Connection* BasicIceController::FindNextPingableConnection() {
int64_t now = rtc::TimeMillis();
// Rule 1: Selected connection takes priority over non-selected ones.
if (selected_connection_ && selected_connection_->connected() &&
selected_connection_->writable() &&
WritableConnectionPastPingInterval(selected_connection_, now)) {
return selected_connection_;
}
// Rule 2: If the channel is weak, we need to find a new writable and
// receiving connection, probably on a different network. If there are lots of
// connections, it may take several seconds between two pings for every
// non-selected connection. This will cause the receiving state of those
// connections to be false, and thus they won't be selected. This is
// problematic for network fail-over. We want to make sure at least one
// connection per network is pinged frequently enough in order for it to be
// selectable. So we prioritize one connection per network.
// Rule 2.1: Among such connections, pick the one with the earliest
// last-ping-sent time.
if (weak()) {
std::vector<const Connection*> pingable_selectable_connections;
absl::c_copy_if(GetBestWritableConnectionPerNetwork(),
std::back_inserter(pingable_selectable_connections),
[this, now](const Connection* conn) {
return WritableConnectionPastPingInterval(conn, now);
});
auto iter = absl::c_min_element(
pingable_selectable_connections,
[](const Connection* conn1, const Connection* conn2) {
return conn1->last_ping_sent() < conn2->last_ping_sent();
});
if (iter != pingable_selectable_connections.end()) {
return *iter;
}
}
// Rule 3: Triggered checks have priority over non-triggered connections.
// Rule 3.1: Among triggered checks, oldest takes precedence.
const Connection* oldest_triggered_check =
FindOldestConnectionNeedingTriggeredCheck(now);
if (oldest_triggered_check) {
return oldest_triggered_check;
}
// Rule 4: Unpinged connections have priority over pinged ones.
RTC_CHECK(connections_.size() ==
pinged_connections_.size() + unpinged_connections_.size());
// If there are unpinged and pingable connections, only ping those.
// Otherwise, treat everything as unpinged.
// TODO(honghaiz): Instead of adding two separate vectors, we can add a state
// "pinged" to filter out unpinged connections.
if (absl::c_none_of(unpinged_connections_,
[this, now](const Connection* conn) {
return this->IsPingable(conn, now);
})) {
unpinged_connections_.insert(pinged_connections_.begin(),
pinged_connections_.end());
pinged_connections_.clear();
}
// Among un-pinged pingable connections, "more pingable" takes precedence.
std::vector<const Connection*> pingable_connections;
absl::c_copy_if(
unpinged_connections_, std::back_inserter(pingable_connections),
[this, now](const Connection* conn) { return IsPingable(conn, now); });
auto iter = absl::c_max_element(
pingable_connections,
[this](const Connection* conn1, const Connection* conn2) {
// Some implementations of max_element
// compare an element with itself.
if (conn1 == conn2) {
return false;
}
return MorePingable(conn1, conn2) == conn2;
});
if (iter != pingable_connections.end()) {
return *iter;
}
return nullptr;
}
// Find "triggered checks". We ping first those connections that have
// received a ping but have not sent a ping since receiving it
// (last_ping_received > last_ping_sent). But we shouldn't do
// triggered checks if the connection is already writable.
const Connection* BasicIceController::FindOldestConnectionNeedingTriggeredCheck(
int64_t now) {
const Connection* oldest_needing_triggered_check = nullptr;
for (auto* conn : connections_) {
if (!IsPingable(conn, now)) {
continue;
}
bool needs_triggered_check =
(!conn->writable() &&
conn->last_ping_received() > conn->last_ping_sent());
if (needs_triggered_check &&
(!oldest_needing_triggered_check ||
(conn->last_ping_received() <
oldest_needing_triggered_check->last_ping_received()))) {
oldest_needing_triggered_check = conn;
}
}
if (oldest_needing_triggered_check) {
RTC_LOG(LS_INFO) << "Selecting connection for triggered check: "
<< oldest_needing_triggered_check->ToString();
}
return oldest_needing_triggered_check;
}
bool BasicIceController::WritableConnectionPastPingInterval(
const Connection* conn,
int64_t now) const {
int interval = CalculateActiveWritablePingInterval(conn, now);
return conn->last_ping_sent() + interval <= now;
}
int BasicIceController::CalculateActiveWritablePingInterval(
const Connection* conn,
int64_t now) const {
// Ping each connection at a higher rate at least
// MIN_PINGS_AT_WEAK_PING_INTERVAL times.
if (conn->num_pings_sent() < MIN_PINGS_AT_WEAK_PING_INTERVAL) {
return weak_ping_interval();
}
int stable_interval =
config_.stable_writable_connection_ping_interval_or_default();
int weak_or_stablizing_interval = std::min(
stable_interval, WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL);
// If the channel is weak or the connection is not stable yet, use the
// weak_or_stablizing_interval.
return (!weak() && conn->stable(now)) ? stable_interval
: weak_or_stablizing_interval;
}
// Is the connection in a state for us to even consider pinging the other side?
// We consider a connection pingable even if it's not connected because that's
// how a TCP connection is kicked into reconnecting on the active side.
bool BasicIceController::IsPingable(const Connection* conn, int64_t now) const {
const Candidate& remote = conn->remote_candidate();
// We should never get this far with an empty remote ufrag.
RTC_DCHECK(!remote.username().empty());
if (remote.username().empty() || remote.password().empty()) {
// If we don't have an ICE ufrag and pwd, there's no way we can ping.
return false;
}
// A failed connection will not be pinged.
if (conn->state() == IceCandidatePairState::FAILED) {
return false;
}
// An never connected connection cannot be written to at all, so pinging is
// out of the question. However, if it has become WRITABLE, it is in the
// reconnecting state so ping is needed.
if (!conn->connected() && !conn->writable()) {
return false;
}
// If we sent a number of pings wo/ reply, skip sending more
// until we get one.
if (conn->TooManyOutstandingPings(field_trials_->max_outstanding_pings)) {
return false;
}
// If the channel is weakly connected, ping all connections.
if (weak()) {
return true;
}
// Always ping active connections regardless whether the channel is completed
// or not, but backup connections are pinged at a slower rate.
if (IsBackupConnection(conn)) {
return conn->rtt_samples() == 0 ||
(now >= conn->last_ping_response_received() +
config_.backup_connection_ping_interval_or_default());
}
// Don't ping inactive non-backup connections.
if (!conn->active()) {
return false;
}
// Do ping unwritable, active connections.
if (!conn->writable()) {
return true;
}
// Ping writable, active connections if it's been long enough since the last
// ping.
return WritableConnectionPastPingInterval(conn, now);
}
// A connection is considered a backup connection if the channel state
// is completed, the connection is not the selected connection and it is active.
bool BasicIceController::IsBackupConnection(const Connection* conn) const {
return ice_transport_state_func_() == IceTransportState::STATE_COMPLETED &&
conn != selected_connection_ && conn->active();
}
const Connection* BasicIceController::MorePingable(const Connection* conn1,
const Connection* conn2) {
RTC_DCHECK(conn1 != conn2);
if (config_.prioritize_most_likely_candidate_pairs) {
const Connection* most_likely_to_work_conn = MostLikelyToWork(conn1, conn2);
if (most_likely_to_work_conn) {
return most_likely_to_work_conn;
}
}
const Connection* least_recently_pinged_conn =
LeastRecentlyPinged(conn1, conn2);
if (least_recently_pinged_conn) {
return least_recently_pinged_conn;
}
// During the initial state when nothing has been pinged yet, return the first
// one in the ordered `connections_`.
auto connections = connections_;
return *(std::find_if(connections.begin(), connections.end(),
[conn1, conn2](const Connection* conn) {
return conn == conn1 || conn == conn2;
}));
}
const Connection* BasicIceController::MostLikelyToWork(
const Connection* conn1,
const Connection* conn2) {
bool rr1 = IsRelayRelay(conn1);
bool rr2 = IsRelayRelay(conn2);
if (rr1 && !rr2) {
return conn1;
} else if (rr2 && !rr1) {
return conn2;
} else if (rr1 && rr2) {
bool udp1 = IsUdp(conn1);
bool udp2 = IsUdp(conn2);
if (udp1 && !udp2) {
return conn1;
} else if (udp2 && udp1) {
return conn2;
}
}
return nullptr;
}
const Connection* BasicIceController::LeastRecentlyPinged(
const Connection* conn1,
const Connection* conn2) {
if (conn1->last_ping_sent() < conn2->last_ping_sent()) {
return conn1;
}
if (conn1->last_ping_sent() > conn2->last_ping_sent()) {
return conn2;
}
return nullptr;
}
std::map<const rtc::Network*, const Connection*>
BasicIceController::GetBestConnectionByNetwork() const {
// `connections_` has been sorted, so the first one in the list on a given
// network is the best connection on the network, except that the selected
// connection is always the best connection on the network.
std::map<const rtc::Network*, const Connection*> best_connection_by_network;
if (selected_connection_) {
best_connection_by_network[selected_connection_->network()] =
selected_connection_;
}
// TODO(honghaiz): Need to update this if `connections_` are not sorted.
for (const Connection* conn : connections_) {
const rtc::Network* network = conn->network();
// This only inserts when the network does not exist in the map.
best_connection_by_network.insert(std::make_pair(network, conn));
}
return best_connection_by_network;
}
std::vector<const Connection*>
BasicIceController::GetBestWritableConnectionPerNetwork() const {
std::vector<const Connection*> connections;
for (auto kv : GetBestConnectionByNetwork()) {
const Connection* conn = kv.second;
if (conn->writable() && conn->connected()) {
connections.push_back(conn);
}
}
return connections;
}
IceControllerInterface::SwitchResult
BasicIceController::HandleInitialSelectDampening(
IceSwitchReason reason,
const Connection* new_connection) {
if (!field_trials_->initial_select_dampening.has_value() &&
!field_trials_->initial_select_dampening_ping_received.has_value()) {
// experiment not enabled => select connection.
return {new_connection, std::nullopt};
}
int64_t now = rtc::TimeMillis();
int64_t max_delay = 0;
if (new_connection->last_ping_received() > 0 &&
field_trials_->initial_select_dampening_ping_received.has_value()) {
max_delay = *field_trials_->initial_select_dampening_ping_received;
} else if (field_trials_->initial_select_dampening.has_value()) {
max_delay = *field_trials_->initial_select_dampening;
}
int64_t start_wait =
initial_select_timestamp_ms_ == 0 ? now : initial_select_timestamp_ms_;
int64_t max_wait_until = start_wait + max_delay;
if (now >= max_wait_until) {
RTC_LOG(LS_INFO) << "reset initial_select_timestamp_ = "
<< initial_select_timestamp_ms_
<< " selection delayed by: " << (now - start_wait) << "ms";
initial_select_timestamp_ms_ = 0;
return {new_connection, std::nullopt};
}
// We are not yet ready to select first connection...
if (initial_select_timestamp_ms_ == 0) {
// Set timestamp on first time...
// but run the delayed invokation everytime to
// avoid possibility that we miss it.
initial_select_timestamp_ms_ = now;
RTC_LOG(LS_INFO) << "set initial_select_timestamp_ms_ = "
<< initial_select_timestamp_ms_;
}
int min_delay = max_delay;
if (field_trials_->initial_select_dampening.has_value()) {
min_delay = std::min(min_delay, *field_trials_->initial_select_dampening);
}
if (field_trials_->initial_select_dampening_ping_received.has_value()) {
min_delay = std::min(
min_delay, *field_trials_->initial_select_dampening_ping_received);
}
RTC_LOG(LS_INFO) << "delay initial selection up to " << min_delay << "ms";
return {.connection = std::nullopt,
.recheck_event = IceRecheckEvent(
IceSwitchReason::ICE_CONTROLLER_RECHECK, min_delay)};
}
IceControllerInterface::SwitchResult BasicIceController::ShouldSwitchConnection(
IceSwitchReason reason,
const Connection* new_connection) {
if (!ReadyToSend(new_connection) || selected_connection_ == new_connection) {
return {std::nullopt, std::nullopt};
}
if (selected_connection_ == nullptr) {
return HandleInitialSelectDampening(reason, new_connection);
}
// Do not switch to a connection that is not receiving if it is not on a
// preferred network or it has higher cost because it may be just spuriously
// better.
int compare_a_b_by_networks = CompareCandidatePairNetworks(
new_connection, selected_connection_, config_.network_preference);
if (compare_a_b_by_networks == b_is_better && !new_connection->receiving()) {
return {std::nullopt, std::nullopt};
}
bool missed_receiving_unchanged_threshold = false;
std::optional<int64_t> receiving_unchanged_threshold(
rtc::TimeMillis() - config_.receiving_switching_delay_or_default());
int cmp = CompareConnections(selected_connection_, new_connection,
receiving_unchanged_threshold,
&missed_receiving_unchanged_threshold);
std::optional<IceRecheckEvent> recheck_event;
if (missed_receiving_unchanged_threshold &&
config_.receiving_switching_delay_or_default()) {
// If we do not switch to the connection because it missed the receiving
// threshold, the new connection is in a better receiving state than the
// currently selected connection. So we need to re-check whether it needs
// to be switched at a later time.
recheck_event.emplace(reason,
config_.receiving_switching_delay_or_default());
}
if (cmp < 0) {
return {new_connection, std::nullopt};
} else if (cmp > 0) {
return {std::nullopt, recheck_event};
}
// If everything else is the same, switch only if rtt has improved by
// a margin.
if (new_connection->rtt() <= selected_connection_->rtt() - kMinImprovement) {
return {new_connection, std::nullopt};
}
return {std::nullopt, recheck_event};
}
IceControllerInterface::SwitchResult
BasicIceController::SortAndSwitchConnection(IceSwitchReason reason) {
// Find the best alternative connection by sorting. It is important to note
// that amongst equal preference, writable connections, this will choose the
// one whose estimated latency is lowest. So it is the only one that we
// need to consider switching to.
// TODO(honghaiz): Don't sort; Just use std::max_element in the right places.
absl::c_stable_sort(
connections_, [this](const Connection* a, const Connection* b) {
int cmp = CompareConnections(a, b, std::nullopt, nullptr);
if (cmp != 0) {
return cmp > 0;
}
// Otherwise, sort based on latency estimate.
return a->rtt() < b->rtt();
});
RTC_LOG(LS_VERBOSE) << "Sorting " << connections_.size()
<< " available connections due to: "
<< IceSwitchReasonToString(reason);
for (size_t i = 0; i < connections_.size(); ++i) {
RTC_LOG(LS_VERBOSE) << connections_[i]->ToString();
}
const Connection* top_connection =
(!connections_.empty()) ? connections_[0] : nullptr;
return ShouldSwitchConnection(reason, top_connection);
}
bool BasicIceController::ReadyToSend(const Connection* connection) const {
// Note that we allow sending on an unreliable connection, because it's
// possible that it became unreliable simply due to bad chance.
// So this shouldn't prevent attempting to send media.
return connection != nullptr &&
(connection->writable() ||
connection->write_state() == Connection::STATE_WRITE_UNRELIABLE ||
PresumedWritable(connection));
}
bool BasicIceController::PresumedWritable(const Connection* conn) const {
return (conn->write_state() == Connection::STATE_WRITE_INIT &&
config_.presume_writable_when_fully_relayed &&
conn->local_candidate().is_relay() &&
(conn->remote_candidate().is_relay() ||
conn->remote_candidate().is_prflx()));
}
// Compare two connections based on their writing, receiving, and connected
// states.
int BasicIceController::CompareConnectionStates(
const Connection* a,
const Connection* b,
std::optional<int64_t> receiving_unchanged_threshold,
bool* missed_receiving_unchanged_threshold) const {
// First, prefer a connection that's writable or presumed writable over
// one that's not writable.
bool a_writable = a->writable() || PresumedWritable(a);
bool b_writable = b->writable() || PresumedWritable(b);
if (a_writable && !b_writable) {
return a_is_better;
}
if (!a_writable && b_writable) {
return b_is_better;
}
// Sort based on write-state. Better states have lower values.
if (a->write_state() < b->write_state()) {
return a_is_better;
}
if (b->write_state() < a->write_state()) {
return b_is_better;
}
// We prefer a receiving connection to a non-receiving, higher-priority
// connection when sorting connections and choosing which connection to
// switch to.
if (a->receiving() && !b->receiving()) {
return a_is_better;
}
if (!a->receiving() && b->receiving()) {
if (!receiving_unchanged_threshold ||
(a->receiving_unchanged_since() <= *receiving_unchanged_threshold &&
b->receiving_unchanged_since() <= *receiving_unchanged_threshold)) {
return b_is_better;
}
*missed_receiving_unchanged_threshold = true;
}
// WARNING: Some complexity here about TCP reconnecting.
// When a TCP connection fails because of a TCP socket disconnecting, the
// active side of the connection will attempt to reconnect for 5 seconds while
// pretending to be writable (the connection is not set to the unwritable
// state). On the passive side, the connection also remains writable even
// though it is disconnected, and a new connection is created when the active
// side connects. At that point, there are two TCP connections on the passive
// side: 1. the old, disconnected one that is pretending to be writable, and
// 2. the new, connected one that is maybe not yet writable. For purposes of
// pruning, pinging, and selecting the selected connection, we want to treat
// the new connection as "better" than the old one. We could add a method
// called something like Connection::ImReallyBadEvenThoughImWritable, but that
// is equivalent to the existing Connection::connected(), which we already
// have. So, in code throughout this file, we'll check whether the connection
// is connected() or not, and if it is not, treat it as "worse" than a
// connected one, even though it's writable. In the code below, we're doing
// so to make sure we treat a new writable connection as better than an old
// disconnected connection.
// In the case where we reconnect TCP connections, the original best
// connection is disconnected without changing to WRITE_TIMEOUT. In this case,
// the new connection, when it becomes writable, should have higher priority.
if (a->write_state() == Connection::STATE_WRITABLE &&
b->write_state() == Connection::STATE_WRITABLE) {
if (a->connected() && !b->connected()) {
return a_is_better;
}
if (!a->connected() && b->connected()) {
return b_is_better;
}
}
return 0;
}
// Compares two connections based only on the candidate and network information.
// Returns positive if `a` is better than `b`.
int BasicIceController::CompareConnectionCandidates(const Connection* a,
const Connection* b) const {
int compare_a_b_by_networks =
CompareCandidatePairNetworks(a, b, config_.network_preference);
if (compare_a_b_by_networks != a_and_b_equal) {
return compare_a_b_by_networks;
}
// Compare connection priority. Lower values get sorted last.
if (a->priority() > b->priority()) {
return a_is_better;
}
if (a->priority() < b->priority()) {
return b_is_better;
}
// If we're still tied at this point, prefer a younger generation.
// (Younger generation means a larger generation number).
int cmp = (a->remote_candidate().generation() + a->generation()) -
(b->remote_candidate().generation() + b->generation());
if (cmp != 0) {
return cmp;
}
// A periodic regather (triggered by the regather_all_networks_interval_range)
// will produce candidates that appear the same but would use a new port. We
// want to use the new candidates and purge the old candidates as they come
// in, so use the fact that the old ports get pruned immediately to rank the
// candidates with an active port/remote candidate higher.
bool a_pruned = is_connection_pruned_func_(a);
bool b_pruned = is_connection_pruned_func_(b);
if (!a_pruned && b_pruned) {
return a_is_better;
}
if (a_pruned && !b_pruned) {
return b_is_better;
}
// Otherwise, must be equal
return 0;
}
int BasicIceController::CompareConnections(
const Connection* a,
const Connection* b,
std::optional<int64_t> receiving_unchanged_threshold,
bool* missed_receiving_unchanged_threshold) const {
RTC_CHECK(a != nullptr);
RTC_CHECK(b != nullptr);
// We prefer to switch to a writable and receiving connection over a
// non-writable or non-receiving connection, even if the latter has
// been nominated by the controlling side.
int state_cmp = CompareConnectionStates(a, b, receiving_unchanged_threshold,
missed_receiving_unchanged_threshold);
if (state_cmp != 0) {
return state_cmp;
}
if (ice_role_func_() == ICEROLE_CONTROLLED) {
// Compare the connections based on the nomination states and the last data
// received time if this is on the controlled side.
if (a->remote_nomination() > b->remote_nomination()) {
return a_is_better;
}
if (a->remote_nomination() < b->remote_nomination()) {
return b_is_better;
}
if (a->last_data_received() > b->last_data_received()) {
return a_is_better;
}
if (a->last_data_received() < b->last_data_received()) {
return b_is_better;
}
}
// Compare the network cost and priority.
return CompareConnectionCandidates(a, b);
}
int BasicIceController::CompareCandidatePairNetworks(
const Connection* a,
const Connection* b,
std::optional<rtc::AdapterType> network_preference) const {
int compare_a_b_by_network_preference =
CompareCandidatePairsByNetworkPreference(a, b,
config_.network_preference);
// The network preference has a higher precedence than the network cost.
if (compare_a_b_by_network_preference != a_and_b_equal) {
return compare_a_b_by_network_preference;
}
bool a_vpn = a->network()->IsVpn();
bool b_vpn = b->network()->IsVpn();
switch (config_.vpn_preference) {
case webrtc::VpnPreference::kDefault:
break;
case webrtc::VpnPreference::kOnlyUseVpn:
case webrtc::VpnPreference::kPreferVpn:
if (a_vpn && !b_vpn) {
return a_is_better;
} else if (!a_vpn && b_vpn) {
return b_is_better;
}
break;
case webrtc::VpnPreference::kNeverUseVpn:
case webrtc::VpnPreference::kAvoidVpn:
if (a_vpn && !b_vpn) {
return b_is_better;
} else if (!a_vpn && b_vpn) {
return a_is_better;
}
break;
default:
break;
}
uint32_t a_cost = a->ComputeNetworkCost();
uint32_t b_cost = b->ComputeNetworkCost();
// Prefer lower network cost.
if (a_cost < b_cost) {
return a_is_better;
}
if (a_cost > b_cost) {
return b_is_better;
}
return a_and_b_equal;
}
std::vector<const Connection*> BasicIceController::PruneConnections() {
// We can prune any connection for which there is a connected, writable
// connection on the same network with better or equal priority. We leave
// those with better priority just in case they become writable later (at
// which point, we would prune out the current selected connection). We leave
// connections on other networks because they may not be using the same
// resources and they may represent very distinct paths over which we can
// switch. If `best_conn_on_network` is not connected, we may be reconnecting
// a TCP connection and should not prune connections in this network.
// See the big comment in CompareConnectionStates.
//
// An exception is made for connections on an "any address" network, meaning
// not bound to any specific network interface. We don't want to keep one of
// these alive as a backup, since it could be using the same network
// interface as the higher-priority, selected candidate pair.
std::vector<const Connection*> connections_to_prune;
auto best_connection_by_network = GetBestConnectionByNetwork();
for (const Connection* conn : connections_) {
const Connection* best_conn = selected_connection_;
if (!rtc::IPIsAny(conn->network()->GetBestIP())) {
// If the connection is bound to a specific network interface (not an
// "any address" network), compare it against the best connection for
// that network interface rather than the best connection overall. This
// ensures that at least one connection per network will be left
// unpruned.
best_conn = best_connection_by_network[conn->network()];
}
// Do not prune connections if the connection being compared against is
// weak. Otherwise, it may delete connections prematurely.
if (best_conn && conn != best_conn && !best_conn->weak() &&
CompareConnectionCandidates(best_conn, conn) >= 0) {
connections_to_prune.push_back(conn);
}
}
return connections_to_prune;
}
bool BasicIceController::GetUseCandidateAttr(const Connection* conn,
NominationMode mode,
IceMode remote_ice_mode) const {
switch (mode) {
case NominationMode::REGULAR:
// TODO(honghaiz): Implement regular nomination.
return false;
case NominationMode::AGGRESSIVE:
if (remote_ice_mode == ICEMODE_LITE) {
return GetUseCandidateAttr(conn, NominationMode::REGULAR,
remote_ice_mode);
}
return true;
case NominationMode::SEMI_AGGRESSIVE: {
// Nominate if
// a) Remote is in FULL ICE AND
// a.1) `conn` is the selected connection OR
// a.2) there is no selected connection OR
// a.3) the selected connection is unwritable OR
// a.4) `conn` has higher priority than selected_connection.
// b) Remote is in LITE ICE AND
// b.1) `conn` is the selected_connection AND
// b.2) `conn` is writable.
bool selected = conn == selected_connection_;
if (remote_ice_mode == ICEMODE_LITE) {
return selected && conn->writable();
}
bool better_than_selected =
!selected_connection_ || !selected_connection_->writable() ||
CompareConnectionCandidates(selected_connection_, conn) < 0;
return selected || better_than_selected;
}
default:
RTC_DCHECK_NOTREACHED();
return false;
}
}
} // namespace cricket