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use super::binding::Connection;
use super::packet::{query::QueryType, question::DnsQuestion, result::ResultCode, Packet};
use crate::Result;
use crate::{config::Config, database::Database, get_time};
use async_recursion::async_recursion;
use moka::future::Cache;
use std::{net::IpAddr, sync::Arc, time::Duration};
use tracing::{error, trace};
pub struct Resolver {
request_id: u16,
connection: Connection,
config: Arc<Config>,
database: Arc<Database>,
cache: Cache<DnsQuestion, (Packet, u64)>,
}
impl Resolver {
pub fn new(
request_id: u16,
connection: Connection,
config: Arc<Config>,
database: Arc<Database>,
cache: Cache<DnsQuestion, (Packet, u64)>,
) -> Self {
Self {
request_id,
connection,
config,
database,
cache,
}
}
async fn lookup_database(&self, question: &DnsQuestion) -> Option<Packet> {
let records = match self
.database
.get_records(&question.name, question.qtype)
.await
{
Ok(record) => record,
Err(err) => {
error!("{err}");
return None;
}
};
if records.is_empty() {
return None;
}
let mut packet = Packet::new();
packet.header.id = self.request_id;
packet.header.questions = 1;
packet.header.answers = records.len() as u16;
packet.header.recursion_desired = true;
packet
.questions
.push(DnsQuestion::new(question.name.to_string(), question.qtype));
for record in records {
packet.answers.push(record);
}
trace!(
"Found stored value for {:?} {}",
question.qtype,
question.name
);
Some(packet)
}
async fn lookup_cache(&self, question: &DnsQuestion) -> Option<Packet> {
let Some((packet, date)) = self.cache.get(&question) else {
return None
};
let now = get_time();
let diff = Duration::from_millis(now - date).as_secs() as u32;
for answer in &packet.answers {
let ttl = answer.get_ttl();
if diff > ttl {
self.cache.invalidate(&question).await;
return None;
}
}
trace!(
"Found cached value for {:?} {}",
question.qtype,
question.name
);
Some(packet)
}
async fn lookup_fallback(&self, question: &DnsQuestion, server: (IpAddr, u16)) -> Packet {
let mut packet = Packet::new();
packet.header.id = self.request_id;
packet.header.questions = 1;
packet.header.recursion_desired = true;
packet
.questions
.push(DnsQuestion::new(question.name.to_string(), question.qtype));
let packet = match self.connection.request_packet(packet, server).await {
Ok(packet) => packet,
Err(e) => {
error!("Failed to complete nameserver request: {e}");
let mut packet = Packet::new();
packet.header.rescode = ResultCode::SERVFAIL;
packet
}
};
packet
}
async fn lookup(&self, question: &DnsQuestion, server: (IpAddr, u16)) -> Packet {
if let Some(packet) = self.lookup_cache(question).await {
return packet;
};
if let Some(packet) = self.lookup_database(question).await {
return packet;
};
trace!(
"Attempting lookup of {:?} {} with ns {}",
question.qtype,
question.name,
server.0
);
self.lookup_fallback(question, server).await
}
#[async_recursion]
async fn recursive_lookup(&mut self, qname: &str, qtype: QueryType) -> Packet {
let question = DnsQuestion::new(qname.to_string(), qtype);
let mut ns = self.config.dns_fallback.clone();
loop {
let ns_copy = ns;
let server = (ns_copy, 53);
let response = self.lookup(&question, server).await;
if !response.answers.is_empty() && response.header.rescode == ResultCode::NOERROR {
self.cache
.insert(question, (response.clone(), get_time()))
.await;
return response;
}
if response.header.rescode == ResultCode::NXDOMAIN {
self.cache
.insert(question, (response.clone(), get_time()))
.await;
return response;
}
if let Some(new_ns) = response.get_resolved_ns(qname) {
ns = new_ns;
continue;
}
let new_ns_name = match response.get_unresolved_ns(qname) {
Some(x) => x,
None => {
self.cache
.insert(question, (response.clone(), get_time()))
.await;
return response;
}
};
let recursive_response = self.recursive_lookup(new_ns_name, QueryType::A).await;
if let Some(new_ns) = recursive_response.get_random_a() {
ns = new_ns;
} else {
self.cache
.insert(question, (response.clone(), get_time()))
.await;
return response;
}
}
}
pub async fn handle_query(mut self) -> Result<()> {
let mut request = self.connection.read_packet().await?;
let mut packet = Packet::new();
packet.header.id = request.header.id;
packet.header.recursion_desired = true;
packet.header.recursion_available = true;
packet.header.response = true;
if let Some(question) = request.questions.pop() {
trace!("Received query: {question:?}");
let result = self.recursive_lookup(&question.name, question.qtype).await;
packet.questions.push(question.clone());
packet.header.rescode = result.header.rescode;
for rec in result.answers {
trace!("Answer: {rec:?}");
packet.answers.push(rec);
}
for rec in result.authorities {
trace!("Authority: {rec:?}");
packet.authorities.push(rec);
}
for rec in result.resources {
trace!("Resource: {rec:?}");
packet.resources.push(rec);
}
} else {
packet.header.rescode = ResultCode::FORMERR;
}
self.connection.write_packet(packet).await?;
Ok(())
}
}
|
