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allow serving into subnet only #16

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allow serving into subnet only #16

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23 changes: 17 additions & 6 deletions src/server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ pub struct Server {
socket: UdpSocket,
src: SocketAddr,
server_ip: Ipv4Addr,
broadcast_ip: Ipv4Addr,
}

pub trait Handler {
Expand Down Expand Up @@ -52,14 +53,26 @@ impl Server {
pub fn serve<H: Handler>(
udp_soc: UdpSocket,
server_ip: Ipv4Addr,
handler: H,
) -> std::io::Error {
Self::serve_in_subnet(udp_soc, server_ip, Ipv4Addr::UNSPECIFIED, handler)
}

pub fn serve_in_subnet<H: Handler>(
udp_soc: UdpSocket,
server_ip: Ipv4Addr,
subnet_mask: Ipv4Addr,
mut handler: H,
) -> std::io::Error {
let mut in_buf: [u8; 1500] = [0; 1500];
let mut s = Server {
out_buf: Cell::new([0; 1500]),
socket: udp_soc,
server_ip,
src: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0)), 0),
broadcast_ip: ((u32::from(server_ip) & u32::from(subnet_mask))
| (u32::from(Ipv4Addr::BROADCAST) & !(u32::from(subnet_mask))))
.into(),
src: SocketAddr::new(IpAddr::V4(Ipv4Addr::UNSPECIFIED), 0),
};
loop {
match s.socket.recv_from(&mut in_buf) {
Expand Down Expand Up @@ -128,18 +141,16 @@ impl Server {
/// Checks the packet see if it was intended for this DHCP server (as opposed to some other also on the network).
pub fn for_this_server(&self, packet: &Packet) -> bool {
match packet.option(options::SERVER_IDENTIFIER) {
Some(DhcpOption::ServerIdentifier(x)) => {
x == &self.server_ip
},
Some(DhcpOption::ServerIdentifier(x)) => x == &self.server_ip,
_ => false,
}
}

/// Encodes and sends a DHCP packet back to the client.
pub fn send(&self, p: Packet) -> std::io::Result<usize> {
let mut addr = self.src;
if p.broadcast || addr.ip() == IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0)) {
addr.set_ip(IpAddr::V4(Ipv4Addr::new(255, 255, 255, 255)));
if p.broadcast || addr.ip().is_unspecified() {
addr.set_ip(IpAddr::V4(self.broadcast_ip));
}
self.socket.send_to(p.encode(&mut self.out_buf.get()), addr)
}
Expand Down