feat: init

src/main.rs

@@ -0,0 +1,77 @@
+mod config;
+mod dns;
+mod logging;
+
+use anyhow::Result;
+use dotenv::dotenv;
+use tokio::net::UdpSocket;
+
+use crate::dns::*;
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    dotenv().ok();
+    let config = config::load()?;
+    logging::setup();
+
+    tracing::info!("start server on port {}", config.port);
+    let sock = UdpSocket::bind(("0.0.0.0", config.port)).await?;
+
+    let mut buffer = [0u8; 512];
+
+    loop {
+        let size = sock.recv(&mut buffer).await?;
+        handle_datagram(buffer.clone(), size);
+    }
+}
+
+fn handle_datagram(buffer: [u8; 512], _buffer_size: usize) {
+    let datagram = DnsHeader {
+        transaction_id: [buffer[0], buffer[1]],
+        query_response: buffer[2] & (1 << 7) > 0,
+        op_code: (buffer[2] >> 3) & 0x0F,
+        authoritative_answer: buffer[2] & (1 << 2) > 0,
+        truncation: buffer[2] & (1 << 1) > 0,
+        recursion_desired: buffer[2] & (1 << 0) > 0,
+        recursion_available: buffer[3] & (1 << 7) > 0,
+        authentic_data: buffer[3] & (1 << 5) > 0,
+        checking_disabled: buffer[3] & (1 << 4) > 0,
+        response_code: buffer[3] & 0xF,
+        number_of_questions: ((buffer[4] as u16) << 8) | (buffer[5] as u16),
+        number_of_answers: ((buffer[6] as u16) << 8) | (buffer[7] as u16),
+        number_of_authority_resource_records: ((buffer[8] as u16) << 8) | (buffer[9] as u16),
+        number_of_additional_resource_records: ((buffer[10] as u16) << 8) | (buffer[11] as u16),
+    };
+
+    println!("Received:\n{}", datagram);
+
+    let mut pos = 12usize;
+    for _ in 0..(datagram.number_of_questions) {
+        let mut domain_parts: Vec<String> = vec![];
+
+        loop {
+            let len = buffer[pos] as usize;
+            if len == 0 {
+                pos += 1;
+                break;
+            }
+
+            let domain_part_bytes = &buffer[(pos + 1)..(pos + 1 + len)];
+            let domain_part = String::from_utf8_lossy(&domain_part_bytes);
+            domain_parts.push(domain_part.to_string());
+            pos += 1 + len;
+        }
+
+        let question_type = ((buffer[pos] as u16) << 8) | (buffer[pos + 1] as u16);
+        let question_class = ((buffer[pos + 2] as u16) << 8) | (buffer[pos + 3] as u16);
+
+        let question = DnsQuestion {
+            domain: domain_parts.join("."),
+            question_type,
+            question_class,
+        };
+        println!("Question: {}", question);
+
+        pos += 4;
+    }
+}