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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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138
chapter2.md
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@@ -21,7 +21,7 @@ impl BytePacketBuffer {
fn write(&mut self, val: u8) -> Result<()> {
if self.pos >= 512 {
return Err(Error::new(ErrorKind::InvalidInput, "End of buffer"));
return Err("End of buffer".into());
}
self.buf[self.pos] = val;
self.pos += 1;
@@ -29,23 +29,23 @@ impl BytePacketBuffer {
}
fn write_u8(&mut self, val: u8) -> Result<()> {
try!(self.write(val));
self.write(val)?;
Ok(())
}
fn write_u16(&mut self, val: u16) -> Result<()> {
try!(self.write((val >> 8) as u8));
try!(self.write((val & 0xFF) as u8));
self.write((val >> 8) as u8)?;
self.write((val & 0xFF) as u8)?;
Ok(())
}
fn write_u32(&mut self, val: u32) -> Result<()> {
try!(self.write(((val >> 24) & 0xFF) as u8));
try!(self.write(((val >> 16) & 0xFF) as u8));
try!(self.write(((val >> 8) & 0xFF) as u8));
try!(self.write(((val >> 0) & 0xFF) as u8));
self.write(((val >> 24) & 0xFF) as u8)?;
self.write(((val >> 16) & 0xFF) as u8)?;
self.write(((val >> 8) & 0xFF) as u8)?;
self.write(((val >> 0) & 0xFF) as u8)?;
Ok(())
}
@@ -55,22 +55,19 @@ We'll also need a function for writing query names in labeled form:
```rust
fn write_qname(&mut self, qname: &str) -> Result<()> {
let split_str = qname.split('.').collect::<Vec<&str>>();
for label in split_str {
for label in qname.split('.') {
let len = label.len();
if len > 0x34 {
return Err(Error::new(ErrorKind::InvalidInput, "Single label exceeds 63 characters of length"));
return Err("Single label exceeds 63 characters of length".into());
}
try!(self.write_u8(len as u8));
self.write_u8(len as u8)?;
for b in label.as_bytes() {
try!(self.write_u8(*b));
self.write_u8(*b)?;
}
}
try!(self.write_u8(0));
self.write_u8(0)?;
Ok(())
}
@@ -89,24 +86,28 @@ impl DnsHeader {
- snip -
pub fn write(&self, buffer: &mut BytePacketBuffer) -> Result<()> {
try!(buffer.write_u16(self.id));
buffer.write_u16(self.id)?;
try!(buffer.write_u8( ((self.recursion_desired as u8)) |
((self.truncated_message as u8) << 1) |
((self.authoritative_answer as u8) << 2) |
(self.opcode << 3) |
((self.response as u8) << 7) as u8) );
buffer.write_u8(
(self.recursion_desired as u8)
| ((self.truncated_message as u8) << 1)
| ((self.authoritative_answer as u8) << 2)
| (self.opcode << 3)
| ((self.response as u8) << 7) as u8,
)?;
try!(buffer.write_u8( (self.rescode.clone() as u8) |
((self.checking_disabled as u8) << 4) |
((self.authed_data as u8) << 5) |
((self.z as u8) << 6) |
((self.recursion_available as u8) << 7) ));
buffer.write_u8(
(self.rescode.clone() as u8)
| ((self.checking_disabled as u8) << 4)
| ((self.authed_data as u8) << 5)
| ((self.z as u8) << 6)
| ((self.recursion_available as u8) << 7),
)?;
try!(buffer.write_u16(self.questions));
try!(buffer.write_u16(self.answers));
try!(buffer.write_u16(self.authoritative_entries));
try!(buffer.write_u16(self.resource_entries));
buffer.write_u16(self.questions)?;
buffer.write_u16(self.answers)?;
buffer.write_u16(self.authoritative_entries)?;
buffer.write_u16(self.resource_entries)?;
Ok(())
}
@@ -124,12 +125,11 @@ impl DnsQuestion {
- snip -
pub fn write(&self, buffer: &mut BytePacketBuffer) -> Result<()> {
try!(buffer.write_qname(&self.name));
buffer.write_qname(&self.name)?;
let typenum = self.qtype.to_num();
try!(buffer.write_u16(typenum));
try!(buffer.write_u16(1));
buffer.write_u16(typenum)?;
buffer.write_u16(1)?;
Ok(())
}
@@ -148,23 +148,26 @@ impl DnsRecord {
- snip -
pub fn write(&self, buffer: &mut BytePacketBuffer) -> Result<usize> {
let start_pos = buffer.pos();
match *self {
DnsRecord::A { ref domain, ref addr, ttl } => {
try!(buffer.write_qname(domain));
try!(buffer.write_u16(QueryType::A.to_num()));
try!(buffer.write_u16(1));
try!(buffer.write_u32(ttl));
try!(buffer.write_u16(4));
DnsRecord::A {
ref domain,
ref addr,
ttl,
} => {
buffer.write_qname(domain)?;
buffer.write_u16(QueryType::A.to_num())?;
buffer.write_u16(1)?;
buffer.write_u32(ttl)?;
buffer.write_u16(4)?;
let octets = addr.octets();
try!(buffer.write_u8(octets[0]));
try!(buffer.write_u8(octets[1]));
try!(buffer.write_u8(octets[2]));
try!(buffer.write_u8(octets[3]));
},
buffer.write_u8(octets[0])?;
buffer.write_u8(octets[1])?;
buffer.write_u8(octets[2])?;
buffer.write_u8(octets[3])?;
}
DnsRecord::UNKNOWN { .. } => {
println!("Skipping record: {:?}", self);
}
@@ -185,26 +188,25 @@ impl DnsPacket {
- snip -
pub fn write(&mut self, buffer: &mut BytePacketBuffer) -> Result<()>
{
pub fn write(&mut self, buffer: &mut BytePacketBuffer) -> Result<()> {
self.header.questions = self.questions.len() as u16;
self.header.answers = self.answers.len() as u16;
self.header.authoritative_entries = self.authorities.len() as u16;
self.header.resource_entries = self.resources.len() as u16;
try!(self.header.write(buffer));
self.header.write(buffer)?;
for question in &self.questions {
try!(question.write(buffer));
question.write(buffer)?;
}
for rec in &self.answers {
try!(rec.write(buffer));
rec.write(buffer)?;
}
for rec in &self.authorities {
try!(rec.write(buffer));
rec.write(buffer)?;
}
for rec in &self.resources {
try!(rec.write(buffer));
rec.write(buffer)?;
}
Ok(())
@@ -219,7 +221,7 @@ We're ready to implement our stub resolver. Rust includes a convenient
`UDPSocket` which does most of the work.
```rust
fn main() {
fn main() -> Result<()> {
// Perform an A query for google.com
let qname = "google.com";
let qtype = QueryType::A;
@@ -228,7 +230,7 @@ fn main() {
let server = ("8.8.8.8", 53);
// Bind a UDP socket to an arbitrary port
let socket = UdpSocket::bind(("0.0.0.0", 43210)).unwrap();
let socket = UdpSocket::bind(("0.0.0.0", 43210))?;
// Build our query packet. It's important that we remember to set the
// `recursion_desired` flag. As noted earlier, the packet id is arbitrary.
@@ -237,37 +239,41 @@ fn main() {
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));
// Use our new write method to write the packet to a buffer...
let mut req_buffer = BytePacketBuffer::new();
packet.write(&mut req_buffer).unwrap();
packet.write(&mut req_buffer)?;
// ...and send it off to the server using our socket:
socket.send_to(&req_buffer.buf[0..req_buffer.pos], server).unwrap();
socket.send_to(&req_buffer.buf[0..req_buffer.pos], server)?;
// To prepare for receiving the response, we'll create a new `BytePacketBuffer`,
// and ask the socket to write the response directly into our buffer.
let mut res_buffer = BytePacketBuffer::new();
socket.recv_from(&mut res_buffer.buf).unwrap();
socket.recv_from(&mut res_buffer.buf)?;
// As per the previous section, `DnsPacket::from_buffer()` is then used to
// actually parse the packet after which we can print the response.
let res_packet = DnsPacket::from_buffer(&mut res_buffer).unwrap();
println!("{:?}", res_packet.header);
let res_packet = DnsPacket::from_buffer(&mut res_buffer)?;
println!("{:#?}", res_packet.header);
for q in res_packet.questions {
println!("{:?}", q);
println!("{:#?}", q);
}
for rec in res_packet.answers {
println!("{:?}", rec);
println!("{:#?}", rec);
}
for rec in res_packet.authorities {
println!("{:?}", rec);
println!("{:#?}", rec);
}
for rec in res_packet.resources {
println!("{:?}", rec);
println!("{:#?}", rec);
}
Ok(())
}
```