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use std::net::IpAddr;
use async_recursion::async_recursion;
use packet::{PacketType, Packet, Result, PacketQuestion, PacketBuffer, ResultCode};
use tokio::net::UdpSocket;
use crate::config::Config;
async fn lookup(qname: &str, qtype: PacketType, server: (IpAddr, u16)) -> Result<Packet> {
let socket = UdpSocket::bind("0.0.0.0:43210").await?;
let mut packet = Packet::new();
packet.header.id = 6666;
packet.header.questions = 1;
packet.header.recursion_desired = true;
packet
.questions
.push(PacketQuestion::new(qname.to_string(), qtype));
let mut req_buffer = PacketBuffer::new();
packet.write(&mut req_buffer)?;
socket.send_to(&req_buffer.buf[0..req_buffer.pos], server).await?;
let mut res_buffer = PacketBuffer::new();
socket.recv_from(&mut res_buffer.buf).await?;
Packet::from_buffer(&mut res_buffer)
}
#[async_recursion]
async fn recursive_lookup(qname: &str, qtype: PacketType, config: &Config) -> Result<Packet> {
let mut ns = config.get_fallback_ns().clone();
loop {
println!("attempting lookup of {:?} {} with ns {}", qtype, qname, ns);
let ns_copy = ns;
let server = (ns_copy, 53);
let response = lookup(qname, qtype, server).await?;
if !response.answers.is_empty() && response.header.rescode == ResultCode::NOERROR {
return Ok(response);
}
if response.header.rescode == ResultCode::NXDOMAIN {
return Ok(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 => return Ok(response),
};
let recursive_response = recursive_lookup(&new_ns_name, PacketType::A, config).await?;
if let Some(new_ns) = recursive_response.get_random_a() {
ns = new_ns;
} else {
return Ok(response);
}
}
}
pub async fn handle_query(socket: &UdpSocket, config: &Config) -> Result<()> {
let mut req_buffer = PacketBuffer::new();
let (_, src) = socket.recv_from(&mut req_buffer.buf).await?;
let mut request = Packet::from_buffer(&mut req_buffer)?;
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() {
println!("Received query: {:?}", question);
if let Ok(result) = recursive_lookup(&question.name, question.qtype, config).await {
packet.questions.push(question.clone());
packet.header.rescode = result.header.rescode;
for rec in result.answers {
println!("Answer: {:?}", rec);
packet.answers.push(rec);
}
for rec in result.authorities {
println!("Authority: {:?}", rec);
packet.authorities.push(rec);
}
for rec in result.resources {
println!("Resource: {:?}", rec);
packet.resources.push(rec);
}
} else {
packet.header.rescode = ResultCode::SERVFAIL;
}
} else {
packet.header.rescode = ResultCode::FORMERR;
}
let mut res_buffer = PacketBuffer::new();
packet.write(&mut res_buffer)?;
let len = res_buffer.pos();
let data = res_buffer.get_range(0, len)?;
socket.send_to(data, src).await?;
Ok(())
}
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