8000 dhcpd: send boot request · Andy-Python-Programmer/dhcpd@d888f9d · GitHub
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dhcpd: send boot request
Signed-off-by: Andy-Python-Programmer <andypythonappdeveloper@gmail.com>
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‎.gitignore

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/target

‎.vscode/settings.json

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{
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"editor.formatOnSave": true
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}

‎Cargo.lock

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‎Cargo.toml

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[package]
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name = "dhcpd"
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version = "0.1.0"
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edition = "2021"
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authors = ["Anhad Singh <andypython@protonmail.com>"]
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[dependencies]
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simple_endian = "*"
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byteorder = { version = "*", default-features = false }

‎src/main.rs

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// Dynamic Host Configuration Protocol
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use std::{error::Error, net::UdpSocket};
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use byteorder::{ByteOrder, NetworkEndian};
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use simple_endian::BigEndian;
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/// Size of IPv4 adderess in octets.
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///
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/// [RFC 8200 § 2]: https://www.rfc-editor.org/rfc/rfc791#section-3.2
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pub const ADDR_SIZE: usize = 4;
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#[derive(Debug, Hash, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default)]
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pub struct Ipv4Addr(pub [u8; ADDR_SIZE]);
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impl Ipv4Addr {
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const EMPTY: Self = Self([0; ADDR_SIZE]);
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}
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// FIXME: The MAC address is usually obtained by using getifaddrs() which currently
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// is unimplemented in mlibc.
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const MAC_ADDRESS: &[u8] = &[52, 54, 0, 12, 34, 56];
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const DHCP_XID: u32 = 0x43424140;
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#[repr(u8)]
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enum DhcpType {
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BootRequest = 1u8.swap_bytes(),
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// BootReply = 2u8.swap_bytes(),
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}
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#[repr(u8)]
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enum HType {
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Ethernet = 1u8.swap_bytes(),
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}
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#[repr(C, packed)]
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struct Header {
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op: DhcpType,
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htype: HType,
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hlen: BigEndian<u8>,
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hops: BigEndian<u8>,
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xid: BigEndian<u32>,
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seconds: BigEndian<u16>,
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flags: BigEndian<u16>,
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client_ip: Ipv4Addr,
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your_ip: Ipv4Addr,
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server_ip: Ipv4Addr,
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gateway_ip: Ipv4Addr,
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client_hw_addr: [u8; 16],
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server_name: [u8; 64],
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file: [u8; 128],
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options: [u8; 64],
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}
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impl Header {
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fn options_mut(&mut self) -> OptionsWriter<'_> {
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OptionsWriter::new(&mut self.options)
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}
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}
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#[repr(u8)]
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enum MessageType {
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Discover = 1u8.swap_bytes(),
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}
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#[repr(u8)]
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enum DhcpOption {
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HostName = 12,
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MessageType = 53,
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ParameterRequestList = 55,
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ClientIdentifier = 61,
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End = 255,
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}
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struct OptionsWriter<'a>(&'a mut [u8]);
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impl<'a> OptionsWriter<'a> {
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fn new(options: &'a mut [u8]) -> Self {
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options.fill(0);
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Self(options).set_magic_cookie()
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}
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fn insert(&mut self, kind: DhcpOption, data: &'_ [u8]) {
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let total_len = 2 + data.len();
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assert!(data.len() < u8::MAX as _);
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assert!(self.0.len() > total_len);
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let (buf, rest) = core::mem::take(&mut self.0).split_at_mut(total_len);
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self.0 = rest;
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buf[0] = kind as u8;
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buf[1] = data.len() as _;
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buf[2..].copy_from_slice(data);
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}
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fn insert_padding(&mut self, size: usize) {
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let (buf, rest) = core::mem::take(&mut self.0).split_at_mut(size);
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self.0 = rest;
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buf.fill(0);
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}
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fn set_magic_cookie(mut self) -> Self {
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let (buf, rest) = core::mem::take(&mut self.0).split_at_mut(core::mem::size_of::<u32>());
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// The first four octets of the 'options' field of the DHCP message
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// contain the (decimal) values 99, 130, 83 and 99, respectively.
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//
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// CC: (https://www.rfc-editor.org/rfc/rfc2131#section-3)
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NetworkEndian::write_u32(buf, 0x63825363);
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self.0 = rest;
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self
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}
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fn set_message_type(mut self, typ: MessageType) -> Self {
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self.insert(DhcpOption::MessageType, &[typ as u8]);
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self
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}
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fn set_parameter_request_list(mut self) -> Self {
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// TODO: Take all of the request flags as an argument.
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self.insert(
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DhcpOption::ParameterRequestList,
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&[
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1, // Subnet Mask
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3, // Router
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15, // Domain Name
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6, // Domain Server
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],
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);
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self
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}
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fn set_client_identifier(mut self) -> Self {
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let mut data = [0; 7];
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data[0] = HType::Ethernet as u8;
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data[1..].copy_from_slice(MAC_ADDRESS);
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self.insert(DhcpOption::ClientIdentifier, data.as_slice());
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self
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}
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fn set_host_name(mut self, name: &str) -> Self {
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self.insert(DhcpOption::HostName, name.as_bytes());
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self.insert_padding(1); // null-terminator
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self
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}
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}
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impl<'a> Drop for OptionsWriter<'a> {
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fn drop(&mut self) {
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self.insert(DhcpOption::End, &[]);
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}
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}
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pub fn main() -> Result<(), Box<dyn Error>> {
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let socket = UdpSocket::bind(("0.0.0.0", 68))?;
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socket.connect(("255.255.255.255", 67))?;
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let mut client_hw_addr = [0; 16];
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client_hw_addr[0..6].copy_from_slice(MAC_ADDRESS);
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let mut header = Header {
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htype: HType::Ethernet,
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hlen: BigEndian::<u8>::from(6),
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hops: BigEndian::<u8>::from(0),
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xid: BigEndian::<u32>::from(DHCP_XID),
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seconds: BigEndian::<u16>::from(0),
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client_hw_addr,
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server_name: [0; 64],
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file: [0; 128],
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options: [0; 64],
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// request info:
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op: DhcpType::BootRequest,
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flags: BigEndian::from(0x8000), // broadcast
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client_ip: Ipv4Addr::EMPTY,
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your_ip: Ipv4Addr::EMPTY,
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server_ip: Ipv4Addr::EMPTY,
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gateway_ip: Ipv4Addr::EMPTY,
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};
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let _ = header
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.options_mut()
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.set_message_type(MessageType::Discover)
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.set_client_identifier()
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.set_host_name("Aero")
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.set_parameter_request_list();
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let header_bytes = unsafe {
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core::slice::from_raw_parts(
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(&header as *const Header) as *const u8,
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std::mem::size_of::<Header>(),
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)
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};
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socket.send(&header_bytes)?;
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Ok(())
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}

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