Initial tftpd implementation with RRQ support

3 files changed, 109 insertions, 3 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 14c3e2b..17bc89d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,3 +5,7 @@ authors = ["Reiner Herrmann <reiner@reiner-h.de>"]
 edition = "2018"
 
 [dependencies]
+
+[[bin]]
+name = "rtftpd"
+path = "src/tftpd.rs"
diff --git a/src/main.rs b/src/main.rs
deleted file mode 100644
index e7a11a9..0000000
--- a/src/main.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-fn main() {
-    println!("Hello, world!");
-}
diff --git a/src/tftpd.rs b/src/tftpd.rs
new file mode 100644
index 0000000..2237761
--- /dev/null
+++ b/src/tftpd.rs
@@ -0,0 +1,105 @@
+use std::net::{SocketAddr,UdpSocket};
+use std::fs::File;
+use std::io::prelude::*;
+
+fn handle_wrq(_cl: &SocketAddr, _buf: &[u8]) {
+}
+
+fn wait_for_ack(sock: &UdpSocket, expected_block: u16) {
+    let mut buf = [0; 4];
+    sock.recv(&mut buf).expect("recv");
+
+    let opcode = u16::from_be_bytes([buf[0], buf[1]]);
+    let block_nr = u16::from_be_bytes([buf[2], buf[3]]);
+
+    if opcode != 4 {
+        // error
+    }
+    if block_nr != expected_block {
+        // error
+    }
+}
+
+fn send_file(cl: &SocketAddr, filename: &str) {
+    let mut file = File::open(filename).expect("open");
+
+    let socket = UdpSocket::bind("0.0.0.0:0").expect("bind");
+    socket.connect(cl).expect("connect");
+    let mut block_nr: u16 = 1;
+
+    loop {
+        let mut filebuf = [0; 512];
+        let n = file.read(&mut filebuf).expect("read");
+
+        let mut sendbuf = vec![0x00, 0x03];  // opcode
+        sendbuf.extend(block_nr.to_be_bytes().iter());
+        sendbuf.extend(filebuf[0..n].iter());
+
+        socket.send(&sendbuf).expect("send");
+        wait_for_ack(&socket, block_nr);
+
+        if n < 512 {
+            /* this was the last block */
+            break;
+        }
+
+        /* increment with rollover on overflow */
+        block_nr = block_nr.wrapping_add(1);
+    }
+}
+
+fn handle_rrq(cl: &SocketAddr, buf: &[u8]) {
+    let mut iter = buf.iter();
+
+    let fname_len = iter.position(|&x| x == 0).expect("not found");
+    let fname_begin = 0;
+    let fname_end = fname_begin + fname_len;
+    let filename = String::from_utf8(buf[fname_begin .. fname_end].to_vec()).expect("str");
+
+    let mode_len = iter.position(|&x| x == 0).expect("not found");
+    let mode_begin = fname_end + 1;
+    let mode_end = mode_begin + mode_len;
+    let mode = String::from_utf8(buf[mode_begin .. mode_end].to_vec()).expect("str");
+    let mode = mode.to_lowercase();
+
+    match mode.as_ref() {
+        "octet" => println!("octet mode"),
+        _ => handle_error(cl, 0, "Unsupported mode"),
+    }
+
+    println!("Sending {} to {}", filename, cl);
+    send_file(&cl, &filename);
+}
+
+fn handle_error(cl: &SocketAddr, code: u16, msg: &str) {
+    let socket = UdpSocket::bind("0.0.0.0:0").expect("bind");
+    socket.connect(cl).expect("connect");
+
+    let mut buf = vec![0x00, 0x05];  // opcode
+    buf.extend(code.to_be_bytes().iter());
+    buf.extend(msg.as_bytes());
+
+    socket.send(&buf).expect("send");
+}
+
+fn handle_client(cl: &SocketAddr, buf: &[u8]) {
+    let opcode = u16::from_be_bytes([buf[0], buf[1]]);
+
+    match opcode {
+        1 /* RRQ */ => handle_rrq(&cl, &buf[2..]),
+        2 /* WRQ */ => handle_wrq(&cl, &buf[2..]),
+        5 /* ERROR */ => println!("Received ERROR from {}", cl),
+        _ => handle_error(cl, 4, "Unexpected opcode"),
+    }
+}
+
+fn main() {
+    let socket = UdpSocket::bind("127.0.0.1:12345").expect("bind");
+
+    loop {
+        let mut buf = [0; 2048];
+        let (n, src) = socket.recv_from(&mut buf).expect("recv");
+
+        handle_client(&src, &buf[0..n]);
+    }
+}