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/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//! Provides a backing task to implement a network
use crate::boot_time::{timeout, BootTime, Duration};
use crate::config::Config;
use crate::connection::Connection;
use crate::dispatcher::{QueryError, Response};
use crate::encoding;
use anyhow::{anyhow, Result};
use std::sync::Arc;
use tokio::sync::{mpsc, watch};
use tokio::task;
use super::{Query, ServerInfo, SocketTagger, ValidationReporter};
pub struct Driver {
info: ServerInfo,
config: Config,
connection: Connection,
command_rx: mpsc::Receiver<Command>,
status_tx: watch::Sender<Status>,
validation: ValidationReporter,
tag_socket: SocketTagger,
}
#[derive(Debug)]
/// Requests the network can handle
pub enum Command {
/// Send a DNS query to the network
Query(Query),
/// Run a probe to check the health of the network. Argument is timeout.
Probe(Duration),
}
#[derive(Clone, Debug)]
/// Current Network Status
///
/// (Unprobed or Failed) can go to (Live or Failed) via Probe.
/// Currently, there is no way to go from Live to Failed - probing a live network will short-circuit to returning valid, and query failures do not declare the network failed.
pub enum Status {
/// Network has not been probed, it may or may not work
Unprobed,
/// Network is believed to be working
Live,
/// Network is broken, reason as argument
Failed(Arc<anyhow::Error>),
}
impl Status {
pub fn is_live(&self) -> bool {
matches!(self, Self::Live)
}
pub fn is_failed(&self) -> bool {
matches!(self, Self::Failed(_))
}
}
async fn build_connection(
info: &ServerInfo,
tag_socket: &SocketTagger,
config: &mut Config,
) -> Result<Connection> {
use std::ops::DerefMut;
Ok(Connection::new(
info.domain.as_deref(),
info.peer_addr,
info.sk_mark,
tag_socket,
config.take().await.deref_mut(),
)
.await?)
}
impl Driver {
const MAX_BUFFERED_COMMANDS: usize = 10;
pub async fn new(
info: ServerInfo,
mut config: Config,
validation: ValidationReporter,
tag_socket: SocketTagger,
) -> Result<(Self, mpsc::Sender<Command>, watch::Receiver<Status>)> {
let (command_tx, command_rx) = mpsc::channel(Self::MAX_BUFFERED_COMMANDS);
let (status_tx, status_rx) = watch::channel(Status::Unprobed);
let connection = build_connection(&info, &tag_socket, &mut config).await?;
Ok((
Self { info, config, connection, status_tx, command_rx, validation, tag_socket },
command_tx,
status_rx,
))
}
pub async fn drive(mut self) -> Result<()> {
while let Some(cmd) = self.command_rx.recv().await {
if let Err(e) = match cmd {
Command::Probe(duration) => self.probe(duration).await,
Command::Query(query) => self.send_query(query).await,
} {
self.status_tx.send(Status::Failed(Arc::new(e)))?
};
}
Ok(())
}
async fn probe(&mut self, probe_timeout: Duration) -> Result<()> {
if self.status_tx.borrow().is_failed() {
// If our network is currently failed, it may be due to issues with the connection.
// Re-establish before re-probing
self.connection =
build_connection(&self.info, &self.tag_socket, &mut self.config).await?;
self.status_tx.send(Status::Unprobed)?;
}
if self.status_tx.borrow().is_live() {
// If we're already validated, short circuit
(self.validation)(&self.info, true).await;
return Ok(());
}
self.force_probe(probe_timeout).await
}
async fn force_probe(&mut self, probe_timeout: Duration) -> Result<()> {
let probe = encoding::probe_query()?;
let dns_request = encoding::dns_request(&probe, &self.info.url)?;
let expiry = BootTime::now().checked_add(probe_timeout);
let request = async {
match self.connection.query(dns_request, expiry).await {
Err(e) => self.status_tx.send(Status::Failed(Arc::new(anyhow!(e)))),
Ok(rsp) => {
if let Some(_stream) = rsp.await {
// TODO verify stream contents
self.status_tx.send(Status::Live)
} else {
self.status_tx.send(Status::Failed(Arc::new(anyhow!("Empty response"))))
}
}
}
};
match timeout(probe_timeout, request).await {
// Timed out
Err(time) => self.status_tx.send(Status::Failed(Arc::new(anyhow!(
"Probe timed out after {:?} (timeout={:?})",
time,
probe_timeout
)))),
// Query completed
Ok(r) => r,
}?;
let valid = self.status_tx.borrow().is_live();
(self.validation)(&self.info, valid).await;
Ok(())
}
async fn send_query(&mut self, query: Query) -> Result<()> {
let request = encoding::dns_request(&query.query, &self.info.url)?;
let stream_fut = self.connection.query(request, Some(query.expiry)).await?;
task::spawn(async move {
let stream = match stream_fut.await {
Some(stream) => stream,
None => {
// We don't care if the response is gone
let _ =
query.response.send(Response::Error { error: QueryError::ConnectionError });
return;
}
};
// We don't care if the response is gone.
let _ = if let Some(err) = stream.error {
query.response.send(Response::Error { error: QueryError::Reset(err) })
} else {
query.response.send(Response::Success { answer: stream.data })
};
});
Ok(())
}
}
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