Add initial packet logic

src/config.rs

@@ -1,8 +1,7 @@
 use std::error::Error;
-use std::net::{AddrParseError, Ipv4Addr};
-use std::num::ParseIntError;
+use std::net::Ipv4Addr;
 use std::path::{Path, PathBuf};
-use std::{env, fmt, process};
+use std::{env, process};
 
 pub struct Config {
     pub ip_address: Ipv4Addr,
@@ -11,7 +10,7 @@ pub struct Config {
 }
 
 impl Config {
-    pub fn new<T>(mut args: T) -> Result<Config, ConfigError>
+    pub fn new<T>(mut args: T) -> Result<Config, Box<dyn Error>>
     where
         T: Iterator<Item = String>,
     {
@@ -69,53 +68,6 @@ impl Config {
     }
 }
 
-#[derive(Debug)]
-pub struct ConfigError {
-    description: String,
-}
-
-impl Error for ConfigError {
-    fn description(&self) -> &str {
-        self.description.as_str()
-    }
-}
-
-impl fmt::Display for ConfigError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.description)
-    }
-}
-
-impl From<AddrParseError> for ConfigError {
-    fn from(value: AddrParseError) -> Self {
-        ConfigError {
-            description: value.to_string(),
-        }
-    }
-}
-
-impl From<ParseIntError> for ConfigError {
-    fn from(value: ParseIntError) -> Self {
-        ConfigError {
-            description: value.to_string(),
-        }
-    }
-}
-
-impl From<String> for ConfigError {
-    fn from(value: String) -> Self {
-        ConfigError { description: value }
-    }
-}
-
-impl From<&str> for ConfigError {
-    fn from(value: &str) -> Self {
-        ConfigError {
-            description: value.to_string(),
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use std::str::FromStr;

src/convert.rs

@@ -0,0 +1,22 @@
+use std::error::Error;
+
+pub struct Convert;
+
+impl Convert {
+    pub fn to_u16(buf: &[u8]) -> Result<u16, &'static str> {
+        if buf.len() < 2 {
+            Err("error when converting to u16")
+        } else {
+            Ok(((buf[0] as u16) << 8) + buf[1] as u16)
+        }
+    }
+
+    pub fn to_string(buf: &[u8]) -> Result<(String, usize), Box<dyn Error>> {
+        let zero_index = match buf[2..].iter().position(|&b| b == 0x00) {
+            Some(index) => index,
+            None => return Err("invalid string".into()),
+        };
+
+        Ok((String::from_utf8(buf[2..zero_index].to_vec())?, zero_index))
+    }
+}

src/lib.rs

@@ -1,2 +1,8 @@
-pub mod config;
+mod config;
+mod convert;
+mod packet;
+mod server;
+
 pub use config::Config;
+pub use convert::Convert;
+pub use server::Server;

src/main.rs

@@ -1,5 +1,5 @@
 use std::{env, process};
-use tftpd::Config;
+use tftpd::{Config, Server};
 
 fn main() {
     let config = Config::new(env::args()).unwrap_or_else(|err| {
@@ -7,8 +7,18 @@ fn main() {
         process::exit(1)
     });
 
+    let server = Server::new(&config).unwrap_or_else(|err| {
+        eprintln!(
+            "Problem creating server on {}:{}: {}",
+            config.ip_address, config.port, err
+        );
+        process::exit(1)
+    });
+
     println!(
         "Running TFTP Server on {}:{}",
         config.ip_address, config.port
     );
+
+    server.listen();
 }

src/packet.rs

@@ -0,0 +1,141 @@
+use crate::Convert;
+use std::error::Error;
+
+pub enum Packet<'a> {
+    Rrq {
+        filename: String,
+        mode: String,
+        options: Vec<Option>,
+    },
+    Wrq {
+        filename: String,
+        mode: String,
+        options: Vec<Option>,
+    },
+    Data {
+        block_num: u16,
+        data: &'a [u8],
+    },
+    Ack(u16),
+    Error {
+        code: ErrorCode,
+        msg: String,
+    },
+}
+
+impl<'a> Packet<'a> {
+    pub fn deserialize(buf: &'a [u8]) -> Result<Packet, Box<dyn Error>> {
+        let opcode = Opcode::from_u16(Convert::to_u16(&buf[0..1])?)?;
+
+        match opcode {
+            Opcode::Rrq | Opcode::Wrq => parse_rq(buf, opcode),
+            Opcode::Data => parse_data(buf),
+            Opcode::Ack => parse_ack(buf),
+            Opcode::Error => parse_error(buf),
+        }
+    }
+}
+
+pub enum Opcode {
+    Rrq = 0x0001,
+    Wrq = 0x0002,
+    Data = 0x0003,
+    Ack = 0x0004,
+    Error = 0x0005,
+}
+
+impl Opcode {
+    pub fn from_u16(val: u16) -> Result<Opcode, &'static str> {
+        match val {
+            0x0001 => Ok(Opcode::Rrq),
+            0x0002 => Ok(Opcode::Wrq),
+            0x0003 => Ok(Opcode::Data),
+            0x0004 => Ok(Opcode::Ack),
+            0x0005 => Ok(Opcode::Error),
+            _ => Err("invalid opcode"),
+        }
+    }
+}
+
+pub struct Option {
+    option: String,
+    value: String,
+}
+
+#[repr(u16)]
+#[derive(PartialEq)]
+pub enum ErrorCode {
+    NotDefined = 0,
+    FileNotFound = 1,
+    AccessViolation = 2,
+    DiskFull = 3,
+    IllegalOperation = 4,
+    UnknownId = 5,
+    FileExists = 6,
+    NoSuchUser = 7,
+}
+
+impl ErrorCode {
+    pub fn from_u16(code: u16) -> Result<ErrorCode, &'static str> {
+        match code {
+            0 => Ok(ErrorCode::NotDefined),
+            1 => Ok(ErrorCode::FileNotFound),
+            2 => Ok(ErrorCode::AccessViolation),
+            3 => Ok(ErrorCode::DiskFull),
+            4 => Ok(ErrorCode::IllegalOperation),
+            5 => Ok(ErrorCode::UnknownId),
+            6 => Ok(ErrorCode::FileExists),
+            7 => Ok(ErrorCode::NoSuchUser),
+            _ => Err("invalid error code"),
+        }
+    }
+}
+
+fn parse_rq(buf: &[u8], opcode: Opcode) -> Result<Packet, Box<dyn Error>> {
+    let mut options = vec![];
+    let filename: String;
+    let mode: String;
+    let mut zero_index: usize;
+
+    (filename, zero_index) = Convert::to_string(&buf[2..])?;
+    (mode, zero_index) = Convert::to_string(&buf[zero_index + 1..])?;
+
+    let mut value: String;
+    let mut option;
+    while zero_index < buf.len() - 1 {
+        (option, zero_index) = Convert::to_string(&buf[zero_index + 1..])?;
+        (value, zero_index) = Convert::to_string(&buf[zero_index + 1..])?;
+        options.push(Option { option, value });
+    }
+
+    match opcode {
+        Opcode::Rrq => Ok(Packet::Rrq {
+            filename,
+            mode,
+            options,
+        }),
+        Opcode::Wrq => Ok(Packet::Wrq {
+            filename,
+            mode,
+            options,
+        }),
+        _ => Err("non request opcode".into()),
+    }
+}
+
+fn parse_data(buf: &[u8]) -> Result<Packet, Box<dyn Error>> {
+    Ok(Packet::Data {
+        block_num: Convert::to_u16(&buf[2..])?,
+        data: &buf[2..],
+    })
+}
+
+fn parse_ack(buf: &[u8]) -> Result<Packet, Box<dyn Error>> {
+    Ok(Packet::Ack(Convert::to_u16(&buf[2..])?))
+}
+
+fn parse_error(buf: &[u8]) -> Result<Packet, Box<dyn Error>> {
+    let code = ErrorCode::from_u16(Convert::to_u16(&buf[2..])?)?;
+    let (msg, _) = Convert::to_string(&buf[4..])?;
+    Ok(Packet::Error { code, msg })
+}

src/server.rs

@@ -0,0 +1,54 @@
+use crate::packet::{ErrorCode, Opcode, Packet};
+use crate::Config;
+use std::error::Error;
+use std::net::{SocketAddr, UdpSocket};
+
+const MAX_REQUEST_PACKET_SIZE: usize = 512;
+
+pub struct Server {
+    socket: UdpSocket,
+}
+
+impl Server {
+    pub fn new(config: &Config) -> Result<Server, Box<dyn Error>> {
+        let socket = UdpSocket::bind(SocketAddr::from((config.ip_address, config.port)))?;
+
+        let server = Server { socket };
+
+        Ok(server)
+    }
+
+    pub fn listen(&self) {
+        loop {
+            let mut buf = [0; MAX_REQUEST_PACKET_SIZE];
+            if let Ok((number_of_bytes, from)) = self.socket.recv_from(&mut buf) {
+                if let Ok(packet) = Packet::deserialize(&buf[..number_of_bytes]) {
+                    match packet {
+                        Packet::Rrq {
+                            filename,
+                            mode,
+                            options,
+                        } => todo!(),
+                        Packet::Wrq {
+                            filename,
+                            mode,
+                            options,
+                        } => todo!(),
+                        _ => self.send_error_msg(from),
+                    }
+                };
+            }
+        }
+    }
+
+    fn send_error_msg(&self, to: SocketAddr) {
+        let buf = [
+            0x00,
+            Opcode::Error as u8,
+            0x00,
+            ErrorCode::IllegalOperation as u8,
+            0x00,
+        ];
+        self.socket.send_to(&buf, to);
+    }
+}