use crate::cache::*;
use crate::dns::{self, *};
use crate::errors::*;
use crate::globals::*;
use byteorder::{BigEndian, ByteOrder};
use rand::prelude::*;
use siphasher::sip128::Hasher128;
use std::hash::Hasher;
use std::net::SocketAddr;
use tokio::net::{TcpStream, UdpSocket};
use tokio::prelude::*;
use tokio_net::driver::Handle;
pub async fn resolve(globals: &Globals, mut packet: &mut Vec<u8>) -> Result<Vec<u8>, Error> {
let original_tid = dns::tid(&packet);
dns::set_tid(&mut packet, 0);
let mut hasher = globals.hasher;
hasher.write(&packet);
let packet_hash = hasher.finish128().as_u128();
let cached_response = {
match globals.cache.lock().get(&packet_hash) {
None => None,
Some(response) => {
let cached_response = (*response).clone();
Some(cached_response)
}
}
};
let cached_response = match cached_response {
None => None,
Some(mut cached_response) => {
cached_response.set_tid(original_tid);
if !cached_response.has_expired() {
debug!("Cached");
return Ok(cached_response.into_response());
}
debug!("Expired");
Some(cached_response)
}
};
let tid = random();
dns::set_tid(&mut packet, tid);
let mut ext_socket = UdpSocket::bind(&globals.external_addr).await?;
ext_socket.connect(&globals.upstream_addr).await?;
dns::set_edns_max_payload_size(&mut packet, DNS_MAX_PACKET_SIZE as u16)?;
let mut response;
let timeout_if_cached = globals.udp_timeout / 2;
loop {
ext_socket.send(&packet).await?;
response = vec![0u8; DNS_MAX_PACKET_SIZE];
dns::set_rcode_servfail(&mut response);
let fut = ext_socket
.recv_from(&mut response[..])
.timeout(timeout_if_cached);
match fut.await {
Ok(Ok((response_len, response_addr))) => {
response.truncate(response_len);
if response_addr == globals.upstream_addr
&& response_len >= DNS_HEADER_SIZE
&& dns::tid(&response) == tid
&& dns::qname(&packet)? == dns::qname(&response)?
{
break;
}
}
_ => {
if cached_response.is_some() {
debug!("Timeout, but cached response is present");
break;
}
debug!("Timeout, no cached response");
}
}
}
if dns::is_truncated(&response) {
let std_socket = match globals.external_addr {
SocketAddr::V4(_) => net2::TcpBuilder::new_v4(),
SocketAddr::V6(_) => net2::TcpBuilder::new_v6(),
}?
.bind(&globals.external_addr)?
.to_tcp_stream()?;
let mut ext_socket =
TcpStream::connect_std(std_socket, &globals.upstream_addr, &Handle::default()).await?;
ext_socket.set_nodelay(true)?;
let mut binlen = [0u8, 0];
BigEndian::write_u16(&mut binlen[..], packet.len() as u16);
ext_socket.write_all(&binlen).await?;
ext_socket.write_all(&packet).await?;
ext_socket.flush();
ext_socket.read_exact(&mut binlen).await?;
let response_len = BigEndian::read_u16(&binlen) as usize;
ensure!(
(DNS_HEADER_SIZE..=DNS_MAX_PACKET_SIZE).contains(&response_len),
"Unexpected response size"
);
response = vec![0u8; response_len];
ext_socket.read_exact(&mut response).await?;
ensure!(dns::tid(&response) == tid, "Unexpected transaction ID");
ensure!(
dns::qname(&packet)? == dns::qname(&response)?,
"Unexpected query name in the response"
);
}
if dns::rcode_servfail(&response) {
debug!("SERVFAIL");
if let Some(cached_response) = cached_response {
debug!("Serving stale");
return Ok(cached_response.into_response());
}
} else {
debug!("Adding to cache");
let cached_response = CachedResponse::new(&globals.cache, response.clone());
globals.cache.lock().insert(packet_hash, cached_response);
}
dns::set_tid(&mut response, original_tid);
Ok(response)
}