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Update examples with modernized code

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This commit is contained in:
Emil Hernvall
2020-06-18 01:47:09 +02:00
parent 31369696d9
commit f815075ae4
10 changed files with 708 additions and 627 deletions
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79
chapter4.md
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@@ -141,26 +141,27 @@ work, it's a rather quick effort!
We'll start out by doing some quick refactoring, moving our lookup code into
a separate function. This is for the most part the same code as we had in our
`main` function in the previous chapter, with the only change being that we
handle errors gracefully using `try!`.
`main` function in the previous chapter.
```rust
fn lookup(qname: &str, qtype: QueryType, server: (&str, u16)) -> Result<DnsPacket> {
let socket = try!(UdpSocket::bind(("0.0.0.0", 43210)));
let socket = UdpSocket::bind(("0.0.0.0", 43210))?;
let mut packet = DnsPacket::new();
packet.header.id = 6666;
packet.header.questions = 1;
packet.header.recursion_desired = true;
packet.questions.push(DnsQuestion::new(qname.to_string(), qtype));
packet
.questions
.push(DnsQuestion::new(qname.to_string(), qtype));
let mut req_buffer = BytePacketBuffer::new();
packet.write(&mut req_buffer).unwrap();
try!(socket.send_to(&req_buffer.buf[0..req_buffer.pos], server));
packet.write(&mut req_buffer)?;
socket.send_to(&req_buffer.buf[0..req_buffer.pos], server)?;
let mut res_buffer = BytePacketBuffer::new();
socket.recv_from(&mut res_buffer.buf).unwrap();
socket.recv_from(&mut res_buffer.buf)?;
DnsPacket::from_buffer(&mut res_buffer)
}
@@ -171,12 +172,12 @@ fn lookup(qname: &str, qtype: QueryType, server: (&str, u16)) -> Result<DnsPacke
Now we'll write our server code. First, we need get some things in order.
```rust
fn main() {
fn main() -> Result<()> {
// Forward queries to Google's public DNS
let server = ("8.8.8.8", 53);
// Bind an UDP socket on port 2053
let socket = UdpSocket::bind(("0.0.0.0", 2053)).unwrap();
let socket = UdpSocket::bind(("0.0.0.0", 2053))?;
// For now, queries are handled sequentially, so an infinite loop for servicing
// requests is initiated.
@@ -224,7 +225,6 @@ fn main() {
if request.questions.is_empty() {
packet.header.rescode = ResultCode::FORMERR;
}
// Usually a question will be present, though.
else {
let question = &request.questions[0];
@@ -254,37 +254,36 @@ fn main() {
} else {
packet.header.rescode = ResultCode::SERVFAIL;
}
// The only thing remaining is to encode our response and send it off!
let mut res_buffer = BytePacketBuffer::new();
match packet.write(&mut res_buffer) {
Ok(_) => {},
Err(e) => {
println!("Failed to encode UDP response packet: {:?}", e);
continue;
}
};
let len = res_buffer.pos();
let data = match res_buffer.get_range(0, len) {
Ok(x) => x,
Err(e) => {
println!("Failed to retrieve response buffer: {:?}", e);
continue;
}
};
match socket.send_to(data, src) {
Ok(_) => {},
Err(e) => {
println!("Failed to send response buffer: {:?}", e);
continue;
}
};
}
} // End of request loop
} // End of main
// The only thing remaining is to encode our response and send it off!
let mut res_buffer = BytePacketBuffer::new();
match packet.write(&mut res_buffer) {
Ok(_) => {}
Err(e) => {
println!("Failed to encode UDP response packet: {:?}", e);
continue;
}
};
let len = res_buffer.pos();
let data = match res_buffer.get_range(0, len) {
Ok(x) => x,
Err(e) => {
println!("Failed to retrieve response buffer: {:?}", e);
continue;
}
};
match socket.send_to(data, src) {
Ok(_) => {}
Err(e) => {
println!("Failed to send response buffer: {:?}", e);
continue;
}
};
}
}
```
The match idiom for error handling is used again and again here, since we want to avoid