feat: add use of command line args

Signed-off-by: nabil salah <[email protected]>

Cargo.toml

@@ -4,6 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+clap = { version = "4.5.23", features = ["derive"] }
 
 [profile.release]
-target = "x86_64-unknown-linux-musl"
+target = "x86_64-unknown-linux-musl"

README.md

@@ -35,6 +35,19 @@ A simple and efficient DNS server implemented in Rust, designed to handle DNS qu
    cargo build
    ```
 
+### Command Line Options
+This is the result of running hermes -h
+```bash
+A simple DNS server application
+
+Usage: dnsserver-nabil [OPTIONS]
+
+Options:
+  -p, --port <PORT>              Port to bind the UDP socket [default: 2053]
+  -f, --forward-ip <FORWARD_IP>  forward replies to specified dns server
+  -h, --help                     Print help
+  -V, --version                  Print version
+```
 ### Running the Server
 
 To run the DNS server, use the following command:

src/lib.rs

@@ -13,9 +13,18 @@ use {
     dns_question::DnsQuestion, query_types::QueryType,
 };
 
-fn recursive_lookup(qname: &str, qtype: QueryType) -> Result<DnsPacket, io::Error> {
-    // For now we're always starting with *a.root-servers.net*.
-    let mut ns = "198.41.0.4".parse::<Ipv4Addr>().unwrap();
+fn recursive_lookup(
+    qname: &str,
+    qtype: QueryType,
+    root_ip: &Option<String>,
+) -> Result<DnsPacket, io::Error> {
+    // For now we're always starting with *a.root-servers.net* if no forwarding ip specified.
+    let mut ns = match root_ip {
+        Some(ip) => ip,
+        None => "198.41.0.4",
+    }
+    .parse::<Ipv4Addr>()
+    .unwrap();
 
     loop {
         println!("attempting lookup of {:?} {} with ns {}", qtype, qname, ns);
@@ -44,7 +53,7 @@ fn recursive_lookup(qname: &str, qtype: QueryType) -> Result<DnsPacket, io::Erro
             None => return Ok(response),
         };
 
-        let recursive_response = recursive_lookup(&new_ns_name, QueryType::A)?;
+        let recursive_response = recursive_lookup(&new_ns_name, QueryType::A, root_ip)?;
 
         if let Some(new_ns) = recursive_response.get_random_a() {
             ns = new_ns;
@@ -80,7 +89,7 @@ fn lookup(qname: &str, qtype: QueryType, server: (Ipv4Addr, u16)) -> Result<DnsP
 /// function handles an incoming DNS query from a UDP socket
 /// and formulates an appropriate DNS response,
 /// either answering directly or using recursive resolution to obtain the necessary data
-pub fn handle_query(socket: &UdpSocket) -> Result<(), io::Error> {
+pub fn handle_query(socket: &UdpSocket, root_ip: &Option<String>) -> Result<(), io::Error> {
     let mut req_buffer = BytePacketBuffer::new();
 
     let (_, src) = socket.recv_from(&mut req_buffer.buf)?;
@@ -95,7 +104,7 @@ pub fn handle_query(socket: &UdpSocket) -> Result<(), io::Error> {
 
     if let Some(question) = request.questions.pop() {
         println!("Received query: {:?}", question);
-        if let Ok(result) = recursive_lookup(&question.name, question.qtype) {
+        if let Ok(result) = recursive_lookup(&question.name, question.qtype, root_ip) {
             packet.questions.push(question.clone());
             packet.header.rescode = result.header.rescode;
 

src/main.rs

@@ -1,13 +1,28 @@
+use clap::Parser;
 use std::{io, net::UdpSocket};
 
+#[derive(Parser)]
+#[command(name = "DnsServerApp")]
+#[command(version = "1.0")]
+#[command(about = "A simple DNS server application", long_about = None)]
+struct Args {
+    /// Port to bind the UDP socket
+    #[arg(short, long, default_value_t = 2053)]
+    port: u16,
+    /// forward replies to specified dns server
+    #[arg(short, long, default_value = None)]
+    forward_ip: Option<String>,
+}
+
 fn main() -> Result<(), io::Error> {
-    // Bind an UDP socket on port 2053
-    let socket = UdpSocket::bind(("0.0.0.0", 2053))?;
+    let args = Args::parse();
+    // Bind an UDP socket on port
+    let socket = UdpSocket::bind(("0.0.0.0", args.port))?;
 
     // For now, queries are handled sequentially, so an infinite loop for servicing
     // requests is initiated.
     loop {
-        match dnsserver_nabil::handle_query(&socket) {
+        match dnsserver_nabil::handle_query(&socket, &args.forward_ip) {
             Ok(_) => {}
             Err(e) => eprintln!("An error occurred: {}", e),
         }