ishan/dns-server-rust
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write answer

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This commit is contained in:
Ishan Jain 2023-12-10 01:31:01 +05:30
parent bf23409ffe
commit da9144327e
Signed by: ishan
GPG Key ID: 0506DB2A1CC75C27
1 changed files with 108 additions and 52 deletions
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162
src/main.rs
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@ -23,7 +23,7 @@ fn main() {
reserved: 0,
rcode: 0,
qd_count: 1,
answer_records: 0,
an_count: 1,
authority_records: 0,
additional_records: 0,
},
@ -32,6 +32,14 @@ fn main() {
q_type: 1,
class: 1,
}],
answers: vec![RRecord {
name: "codecrafters.io".into(),
class: 1,
r_type: 1,
ttl: 1337,
rdlength: 4,
data: RData::A([0x8, 0x8, 0x8, 0x8]),
}],
};
packet.write_to(&mut response);
@ -48,11 +56,6 @@ fn main() {
}
}
struct Packet {
header: Header,
questions: Vec<Question>,
}
struct Header {
ident: u16,
query: bool,
@ -64,11 +67,56 @@ struct Header {
reserved: u8,
rcode: u8, // TODO: enum
qd_count: u16,
answer_records: u16,
an_count: u16,
authority_records: u16,
additional_records: u16,
}
impl Header {
pub fn parse(data: &[u8]) -> Result<Self, &'static str> {
if data.len() != 12 {
return Err("input bytes len is not equal to 12");
}
Ok(Self {
ident: u16::from_be_bytes([data[0], data[1]]),
query: ((data[2] >> 7) & 1) == 1,
opcode: (data[2] >> 3),
authoritative: ((data[2] >> 2) & 1) == 1,
truncated: ((data[2] >> 1) & 1) == 1,
recursion_desired: (data[2] & 1) == 1,
recursion_avail: ((data[3] >> 7) & 1) == 1,
reserved: ((data[3] >> 4) & 0b111),
rcode: (data[3] & 0b1111),
qd_count: u16::from_be_bytes([data[4], data[5]]),
an_count: u16::from_be_bytes([data[6], data[7]]),
authority_records: u16::from_be_bytes([data[8], data[9]]),
additional_records: u16::from_be_bytes([data[10], data[11]]),
})
}
pub fn write_to(self, buf: &mut Vec<u8>) {
// write ident
buf.extend(self.ident.to_be_bytes());
// Write flags
let flag0_byte = (self.query as u8) << 7
| self.opcode << 3
| (self.authoritative as u8) << 2
| (self.truncated as u8) << 1
| self.recursion_desired as u8;
let flag1_byte = (self.recursion_avail as u8) << 7 | self.reserved << 4 | self.rcode;
buf.push(flag0_byte);
buf.push(flag1_byte);
// Write counts
buf.extend(self.qd_count.to_be_bytes());
buf.extend(self.an_count.to_be_bytes());
buf.extend(self.authority_records.to_be_bytes());
buf.extend(self.additional_records.to_be_bytes());
}
}
struct Question {
name: Qname,
q_type: u16,
@ -112,12 +160,62 @@ impl From<&str> for Qname {
}
}
struct RRecord {
name: Qname,
r_type: u16,
class: u16,
ttl: u32,
rdlength: u16,
data: RData,
}
impl RRecord {
pub fn parse(data: &[u8]) -> Result<Self, &'static str> {
todo!()
}
pub fn write_to(self, buf: &mut Vec<u8>) {
self.name.write_to(buf);
buf.extend(self.r_type.to_be_bytes());
buf.extend(self.class.to_be_bytes());
buf.extend(self.ttl.to_be_bytes());
buf.extend(self.rdlength.to_be_bytes());
self.data.write_to(buf);
}
}
enum RData {
A([u8; 4]),
Aaaa([u8; 16]),
}
impl RData {
pub fn write_to(self, buf: &mut Vec<u8>) {
match self {
RData::A(addr) => buf.extend(addr),
RData::Aaaa(addr) => buf.extend(addr),
}
}
}
struct Packet {
header: Header,
questions: Vec<Question>,
answers: Vec<RRecord>,
}
impl Packet {
pub fn parse(data: &[u8]) -> Result<Self, &'static str> {
let header = Header::parse(&data[..12])?;
let questions = vec![Question::parse(&data[12..])?]; // TODO: need some thing better here
let answers = vec![RRecord::parse(&data[12..])?]; // TODO: need some thing better here
Ok(Self { header, questions })
Ok(Self {
header,
questions,
answers,
})
}
pub fn write_to(self, buf: &mut Vec<u8>) {
@ -126,51 +224,9 @@ impl Packet {
for question in self.questions {
question.write_to(buf);
}
for answer in self.answers {
answer.write_to(buf);
}
}
impl Header {
pub fn parse(data: &[u8]) -> Result<Self, &'static str> {
if data.len() != 12 {
return Err("input bytes len is not equal to 12");
}
Ok(Self {
ident: u16::from_be_bytes([data[0], data[1]]),
query: ((data[2] >> 7) & 1) == 1,
opcode: (data[2] >> 3),
authoritative: ((data[2] >> 2) & 1) == 1,
truncated: ((data[2] >> 1) & 1) == 1,
recursion_desired: (data[2] & 1) == 1,
recursion_avail: ((data[3] >> 7) & 1) == 1,
reserved: ((data[3] >> 4) & 0b111),
rcode: (data[3] & 0b1111),
qd_count: u16::from_be_bytes([data[4], data[5]]),
answer_records: u16::from_be_bytes([data[6], data[7]]),
authority_records: u16::from_be_bytes([data[8], data[9]]),
additional_records: u16::from_be_bytes([data[10], data[11]]),
})
}
pub fn write_to(self, buf: &mut Vec<u8>) {
// write ident
buf.extend(self.ident.to_be_bytes());
// Write flags
let flag0_byte = (self.query as u8) << 7
| self.opcode << 3
| (self.authoritative as u8) << 2
| (self.truncated as u8) << 1
| self.recursion_desired as u8;
let flag1_byte = (self.recursion_avail as u8) << 7 | self.reserved << 4 | self.rcode;
buf.push(flag0_byte);
buf.push(flag1_byte);
// Write counts
buf.extend(self.qd_count.to_be_bytes());
buf.extend(self.answer_records.to_be_bytes());
buf.extend(self.authority_records.to_be_bytes());
buf.extend(self.additional_records.to_be_bytes());
}
}