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use dhcp4d::lease::{Lease, LeaseDummyManager, LeaseManager};
use std::mem::MaybeUninit;
use std::net::{IpAddr, Ipv4Addr, SocketAddr, SocketAddrV4};
use std::sync::{Arc, Mutex};
use std::thread;
use anyhow::{anyhow, bail};
use dhcproto::v4::{DhcpOption, Flags, Message, MessageType, Opcode, OptionCode};
use dhcproto::{Decodable, Decoder, Encodable, Encoder};
use socket2::{Domain, Socket, Type};
fn main() -> anyhow::Result<()> {
let lease_mgr = Arc::new(Mutex::new(LeaseDummyManager::new(None)));
let mut threads = Vec::new();
for arg in std::env::args().skip(1) {
let cloned_mgr = Arc::clone(&lease_mgr);
threads.push(thread::spawn(|| run(arg, cloned_mgr)));
}
for handle in threads {
handle.join().unwrap()?;
}
Ok(())
}
fn run(link: String, lease_mgr: Arc<Mutex<LeaseDummyManager>>) -> anyhow::Result<()> {
let sock = Socket::new(Domain::IPV4, Type::DGRAM, None)?;
let addresses = linkaddrs::ipv4_addresses(link)?;
let address = addresses.first().expect("interface has no IPv4 addresses");
let address = SocketAddr::new(IpAddr::V4(address.addr()), 67);
sock.bind(&address.into())?;
sock.set_broadcast(true)?;
loop {
let mut buf = [MaybeUninit::new(0); 1024];
let (n, remote) = sock.recv_from(&mut buf)?;
let buf = &buf
.iter()
.take(n)
.map(|p| unsafe { p.assume_init() })
.collect::<Vec<u8>>();
let remote = remote.as_socket_ipv4().unwrap();
match handle_request(&sock, lease_mgr.clone(), buf, remote) {
Ok(_) => {}
Err(e) => eprintln!("erroneous request from {}: {}", remote, e),
}
}
}
fn handle_request(
sock: &Socket,
lease_mgr: Arc<Mutex<LeaseDummyManager>>,
buf: &[u8],
remote: SocketAddrV4,
) -> anyhow::Result<()> {
let msg = Message::decode(&mut Decoder::new(buf))?;
let op = msg.opcode();
match op {
Opcode::BootRequest => {
let xid = msg.xid();
let opts = msg.opts();
let msg_type = opts.msg_type().ok_or(anyhow!("no message type given"))?;
match msg_type {
MessageType::Discover => {
let client_id = match opts
.get(OptionCode::ClientIdentifier)
.ok_or(anyhow!("no client id"))?
{
DhcpOption::ClientIdentifier(id) => id,
_ => bail!("expected ClientIdentifier"),
};
let lease = obtain_lease(lease_mgr.clone(), client_id)
.ok_or(anyhow!("no free addresses available"))?;
let own_addr = own_address(sock);
let lease_mgr = lease_mgr.lock().unwrap();
let mut resp = Message::default();
let opts = resp
.set_flags(Flags::default().set_broadcast())
.set_opcode(Opcode::BootReply)
.set_xid(xid)
.set_yiaddr(lease.address)
.set_siaddr(own_addr)
.set_chaddr(msg.chaddr())
.opts_mut();
opts.insert(DhcpOption::MessageType(MessageType::Offer));
opts.insert(DhcpOption::SubnetMask(lease_mgr.netmask()));
opts.insert(DhcpOption::Router(vec![own_addr]));
opts.insert(DhcpOption::AddressLeaseTime(
lease.lease_time.as_secs() as u32
));
opts.insert(DhcpOption::ServerIdentifier(own_addr));
opts.insert(DhcpOption::DomainNameServer(vec![own_addr]));
let mut resp_buf = Vec::new();
resp.encode(&mut Encoder::new(&mut resp_buf))?;
let n = sock.send_to(&resp_buf, &remote.into())?;
if n != resp_buf.len() {
Err(anyhow!("partial response"))
} else {
let cid = client_id
.iter()
.map(|octet| format!("{:x}", octet))
.reduce(|acc, octet| acc + &octet)
.ok_or(anyhow!("zero-length client id"))?;
println!(
"offering {} to client ID {} for {:?}",
lease.address, cid, lease.lease_time
);
Ok(())
}
}
MessageType::Request => {
let mut lease_mgr = lease_mgr.lock().unwrap();
let requested_addr = match opts
.get(OptionCode::RequestedIpAddress)
.ok_or(anyhow!("no address requested"))?
{
DhcpOption::RequestedIpAddress(addr) => addr,
_ => bail!("expected RequestedIpAddress"),
};
if !lease_mgr.request(*requested_addr) {
// NAK
todo!();
} else {
let lease_time = lease_mgr.lease_time();
let own_addr = own_address(sock);
let mut resp = Message::default();
let opts = resp
.set_flags(Flags::default().set_broadcast())
.set_opcode(Opcode::BootReply)
.set_xid(xid)
.set_yiaddr(*requested_addr)
.set_siaddr(own_addr)
.set_chaddr(msg.chaddr())
.opts_mut();
opts.insert(DhcpOption::MessageType(MessageType::Ack));
opts.insert(DhcpOption::SubnetMask(lease_mgr.netmask()));
opts.insert(DhcpOption::Router(vec![own_addr]));
opts.insert(DhcpOption::AddressLeaseTime(lease_time.as_secs() as u32));
opts.insert(DhcpOption::ServerIdentifier(own_addr));
opts.insert(DhcpOption::DomainNameServer(vec![own_addr]));
let mut resp_buf = Vec::new();
resp.encode(&mut Encoder::new(&mut resp_buf))?;
let n = sock.send_to(&resp_buf, &remote.into())?;
if n != resp_buf.len() {
Err(anyhow!("partial response"))
} else {
println!("ackknowledging {} for {:?}", requested_addr, lease_time);
Ok(())
}
}
}
_ => Err(anyhow!("invalid message type {:?}", msg_type,)),
}
}
_ => Err(anyhow!("invalid opcode {:?}", op)),
}
}
fn obtain_lease<T: LeaseManager>(lease_mgr: Arc<Mutex<T>>, client_id: &[u8]) -> Option<Lease> {
lease_mgr.lock().unwrap().persistent_free_address(client_id)
}
fn own_address(sock: &Socket) -> Ipv4Addr {
let local_addr = sock.local_addr().unwrap().as_socket_ipv4().unwrap();
*local_addr.ip()
}
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