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//! This module keeps track of the last known good API IP address and reads and stores it on disk.
use crate::{ApiEndpoint, DnsResolver};
use async_trait::async_trait;
use std::{fmt::Debug, io, net::SocketAddr, path::Path, sync::Arc};
use tokio::{
fs,
io::{AsyncReadExt, AsyncWriteExt},
sync::Mutex,
};
#[derive(thiserror::Error, Debug)]
pub enum Error {
#[error("Attempt to read without a path specified")]
NoPath,
#[error("Failed to open the address cache file")]
Open(#[source] io::Error),
#[error("Failed to read the address cache file")]
Read(#[source] io::Error),
#[error("Failed to parse the address cache file")]
Parse,
#[error("Failed to update the address cache file")]
Write(#[source] io::Error),
}
/// a backing store for an AddressCache.
#[async_trait]
pub trait AddressCacheBacking: 'static + Sync + Send {
async fn read(&self) -> Result<Vec<u8>, Error>;
async fn write(&self, data: &[u8]) -> Result<(), Error>;
}
#[derive(Clone, Debug)]
pub struct FileAddressCacheBacking {
read_path: Option<Arc<Path>>,
write_path: Option<Arc<Path>>,
}
#[async_trait]
impl AddressCacheBacking for FileAddressCacheBacking {
async fn read(&self) -> Result<Vec<u8>, Error> {
let Some(read_path) = self.read_path.as_ref() else {
return Err(Error::NoPath);
};
let mut file = fs::File::open(read_path).await.map_err(Error::Open)?;
let mut result = vec![];
file.read(&mut result).await.map_err(Error::Read)?;
Ok(result)
}
async fn write(&self, data: &[u8]) -> Result<(), Error> {
let Some(write_path) = self.write_path.as_ref() else {
return Err(Error::NoPath);
};
let mut file = mullvad_fs::AtomicFile::new(&**write_path)
.await
.map_err(Error::Open)?;
file.write_all(data).await.map_err(Error::Write)?;
file.finalize().await.map_err(Error::Write)
}
}
/// A DNS resolver which resolves using `AddressCache`.
#[async_trait]
impl<T: AddressCacheBacking> DnsResolver for AddressCache<T> {
async fn resolve(&self, host: String) -> Result<Vec<SocketAddr>, io::Error> {
self.resolve_hostname(&host)
.await
.map(|addr| vec![addr])
.ok_or(io::Error::other("host does not match API host"))
}
}
#[derive(Clone, Debug)]
pub struct AddressCache<T> {
hostname: String,
inner: Arc<Mutex<AddressCacheInner>>,
backing: Arc<T>,
}
impl AddressCache<FileAddressCacheBacking> {
/// Initialize cache using `read_path`, and write changes to `write_path`.
pub async fn from_file(
read_path: &Path,
write_path: Option<Box<Path>>,
hostname: String,
) -> Result<AddressCache<FileAddressCacheBacking>, Error> {
log::debug!("Loading API addresses from {}", read_path.display());
let backing = FileAddressCacheBacking {
read_path: Some(Arc::from(read_path)),
write_path: write_path.map(Arc::from),
};
AddressCache::from_backing(hostname, Arc::new(backing)).await
}
/// Initialize cache using the hardcoded address, and write changes to `write_path`.
pub fn new(
endpoint: &ApiEndpoint,
write_path: Option<Box<Path>>,
) -> AddressCache<FileAddressCacheBacking> {
let backing = FileAddressCacheBacking {
read_path: None,
write_path: write_path.map(Arc::from),
};
AddressCache::new_with_address(endpoint, Arc::new(backing))
}
}
impl<T: AddressCacheBacking> AddressCache<T> {
/// Initialise cache using a hardcoded address and a Backing for writing to
pub fn new_with_address(endpoint: &ApiEndpoint, backing: Arc<T>) -> Self {
Self::new_inner(endpoint.address(), endpoint.host().to_owned(), backing)
}
pub async fn from_backing(hostname: String, backing: Arc<T>) -> Result<Self, Error> {
let address = read_address_backing(backing.as_ref()).await?;
Ok(Self::new_inner(address, hostname, backing))
}
pub async fn from_backing_or(
hostname: String,
backing: Arc<T>,
endpoint: &ApiEndpoint,
) -> Self {
Self::from_backing(hostname.clone(), Arc::clone(&backing))
.await
.unwrap_or(Self::new_inner(endpoint.address(), hostname, backing))
}
fn new_inner(address: SocketAddr, hostname: String, backing: Arc<T>) -> Self {
let cache = AddressCacheInner::from_address(address);
log::debug!("Using API address: {}", cache.address);
Self {
inner: Arc::new(Mutex::new(cache)),
hostname,
backing,
}
}
/// Returns the address if the hostname equals `API.host`. Otherwise, returns `None`.
async fn resolve_hostname(&self, hostname: &str) -> Option<SocketAddr> {
if hostname.eq_ignore_ascii_case(&self.hostname) {
Some(self.get_address().await)
} else {
None
}
}
/// Returns the currently selected address.
pub async fn get_address(&self) -> SocketAddr {
self.inner.lock().await.address
}
pub async fn set_address(&self, address: SocketAddr) -> Result<(), Error> {
let mut inner = self.inner.lock().await;
if address != inner.address {
match self.save_to_backing(&address).await {
Ok(()) | Err(Error::NoPath) => (),
Err(err) => return Err(err),
};
inner.address = address;
}
Ok(())
}
async fn save_to_backing(&self, address: &SocketAddr) -> Result<(), Error> {
let mut contents = address.to_string();
contents += "\n";
self.backing.write(contents.as_bytes()).await
}
}
#[derive(Clone, PartialEq, Eq, Debug)]
struct AddressCacheInner {
address: SocketAddr,
}
impl AddressCacheInner {
fn from_address(address: SocketAddr) -> Self {
Self { address }
}
}
async fn read_address_backing(backing: &impl AddressCacheBacking) -> Result<SocketAddr, Error> {
backing
.read()
.await
.and_then(|bytes| String::from_utf8(bytes).map_err(|_| Error::Parse))
.and_then(|a| a.trim().parse().map_err(|_| Error::Parse))
}
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