1 files changed, 121 insertions, 0 deletions
diff --git a/resolver/src/server.rs b/resolver/src/server.rs
new file mode 100644
index 0000000..b9c5fee
--- /dev/null
+++ b/resolver/src/server.rs
@@ -0,0 +1,121 @@
+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(())
+}
+\ No newline at end of file