Refactored project a bit, added question parser

src/header.rs

@@ -0,0 +1,64 @@
+#[derive(Debug)]
+pub struct Header {
+    pub ident: u16,
+    pub query: bool,
+    pub opcode: u8, // TODO: enum
+    pub authoritative: bool,
+    pub truncated: bool,
+    pub recursion_desired: bool,
+    pub recursion_avail: bool,
+    pub reserved: u8,
+    pub rcode: u8, // TODO: enum
+    pub qd_count: u16,
+    pub an_count: u16,
+    pub authority_records: u16,
+    pub 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>) {
+        buf.reserve(12);
+
+        // 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());
+    }
+}

src/main.rs

@@ -1,3 +1,11 @@
+mod header;
+mod qname;
+use header::*;
+mod question;
+use question::*;
+mod rrecord;
+use rrecord::*;
+
 use std::net::UdpSocket;
 
 fn main() {
@@ -13,6 +21,8 @@ fn main() {
 
                 let mut recv_packet = Packet::parse(received_data).unwrap();
 
+                println!("{:?}", recv_packet);
+
                 recv_packet.header.query = true;
                 recv_packet.header.authoritative = false;
                 recv_packet.header.truncated = false;
@@ -24,19 +34,13 @@ fn main() {
                 recv_packet.header.authority_records = 0;
                 recv_packet.header.additional_records = 0;
 
-                recv_packet.questions = vec![Question {
-                    name: "codecrafters.io".into(),
-                    q_type: 1,
-                    class: 1,
-                }];
-
                 recv_packet.answers = vec![RRecord {
-                    name: "codecrafters.io".into(),
+                    name: recv_packet.questions[0].name.clone(),
                     class: 1,
                     r_type: 1,
                     ttl: 1337,
                     rdlength: 4,
-                    data: RData::A([0x8, 0x8, 0x8, 0x8]),
+                    rdata: RData::A([0x8, 0x8, 0x8, 0x8]),
                 }];
 
                 recv_packet.write_to(&mut response);
@@ -53,165 +57,36 @@ fn main() {
     }
 }
 
-struct Header {
-    ident: u16,
-    query: bool,
-    opcode: u8, // TODO: enum
-    authoritative: bool,
-    truncated: bool,
-    recursion_desired: bool,
-    recursion_avail: bool,
-    reserved: u8,
-    rcode: u8, // TODO: enum
-    qd_count: 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,
-    class: u16,
-}
-
-impl Question {
-    pub fn parse(data: &[u8]) -> Result<Self, &'static str> {
-        Err("invalid")
-    }
-
-    pub fn write_to(self, buf: &mut Vec<u8>) {
-        self.name.write_to(buf);
-        buf.extend(self.q_type.to_be_bytes());
-        buf.extend(self.class.to_be_bytes());
-    }
-}
-
-struct Qname(Vec<(u8, String)>);
-
-impl Qname {
-    pub fn write_to(&self, buf: &mut Vec<u8>) {
-        for (i, v) in &self.0 {
-            buf.push(*i);
-            buf.extend(v.bytes());
-        }
-
-        buf.push(0);
-    }
-}
-
-impl From<&str> for Qname {
-    fn from(value: &str) -> Self {
-        let mut output = vec![];
-
-        for label in value.split('.') {
-            output.push((label.len() as u8, label.to_string()));
-        }
-
-        Qname(output)
-    }
-}
-
-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 {
+#[derive(Debug)]
+struct Packet<'a> {
     header: Header,
-    questions: Vec<Question>,
-    answers: Vec<RRecord>,
+    questions: Vec<Question<'a>>,
+    answers: Vec<RRecord<'a>>,
 }
 
-impl Packet {
-    pub fn parse(data: &[u8]) -> Result<Self, &'static str> {
+impl<'a> Packet<'a> {
+    pub fn parse(mut data: &'a [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
+        data = &data[12..];
+
+        let mut questions = Vec::with_capacity(header.qd_count as usize);
+
+        for _ in 0..header.qd_count {
+            let rec = Question::parse(data)?;
+            data = &data[rec.length()..];
+            questions.push(rec);
+        }
+        let mut answers = Vec::with_capacity(header.an_count as usize);
+        for _ in 0..header.an_count {
+            let rec = RRecord::parse(data)?;
+            data = &data[rec.length()..];
+            answers.push(rec);
+        }
 
         Ok(Self {
             header,
-            questions: vec![],
-            answers: vec![],
+            questions,
+            answers,
         })
     }
 

src/qname.rs

@@ -0,0 +1,61 @@
+use std::{
+    borrow::Cow,
+    fmt::{Display, Formatter, Result as FmtResult},
+};
+
+#[derive(Debug, Clone)]
+pub struct Qname<'a> {
+    labels: Cow<'a, [u8]>,
+}
+
+impl<'a> Qname<'a> {
+    pub fn write_to(&self, buf: &mut Vec<u8>) {
+        buf.extend(self.labels.iter());
+    }
+
+    // Assume data _starts_ at the question section
+    pub fn parse(data: &'a [u8]) -> Self {
+        // Do a quick check to make sure every thing is valid
+        // and save the slice
+
+        let mut i = 0;
+        while data[i] != 0 {
+            let length = data[i] as usize;
+            i += length + 1;
+        }
+        // NULL byte
+        i += 1;
+
+        Self {
+            labels: Cow::Borrowed(&data[0..i]),
+        }
+    }
+
+    pub fn length(&self) -> usize {
+        self.labels.len()
+    }
+}
+
+impl<'a> From<&'a str> for Qname<'a> {
+    fn from(value: &'a str) -> Self {
+        let mut labels = vec![];
+
+        for label in value.split('.') {
+            labels.push(label.len() as u8);
+            labels.extend(label.bytes());
+        }
+
+        // for null byte
+        labels.push(0);
+
+        Qname {
+            labels: Cow::Owned(labels),
+        }
+    }
+}
+
+impl<'a> Display for Qname<'a> {
+    fn fmt(&self, f: &mut Formatter) -> FmtResult {
+        todo!()
+    }
+}

src/question.rs

@@ -0,0 +1,37 @@
+use crate::qname::Qname;
+
+#[derive(Debug)]
+pub struct Question<'a> {
+    pub name: Qname<'a>,
+    pub q_type: u16,
+    pub class: u16,
+}
+
+impl<'a> Question<'a> {
+    pub fn parse(mut data: &'a [u8]) -> Result<Self, &'static str> {
+        let qname = Qname::parse(data);
+        data = &data[qname.length()..];
+
+        debug_assert!(data.len() >= 4);
+        let q_type = u16::from_be_bytes([data[0], data[1]]);
+        let class = u16::from_be_bytes([data[2], data[3]]);
+
+        Ok(Self {
+            name: qname,
+            q_type,
+            class,
+        })
+    }
+
+    pub fn length(&self) -> usize {
+        self.name.length() + 2 + 2
+    }
+
+    pub fn write_to(self, buf: &mut Vec<u8>) {
+        buf.reserve(self.length());
+
+        self.name.write_to(buf);
+        buf.extend(self.q_type.to_be_bytes());
+        buf.extend(self.class.to_be_bytes());
+    }
+}

src/rrecord.rs

@@ -0,0 +1,76 @@
+use crate::qname::Qname;
+
+#[derive(Debug)]
+pub struct RRecord<'a> {
+    pub name: Qname<'a>,
+    pub r_type: u16,
+    pub class: u16,
+    pub ttl: u32,
+    pub rdlength: u16,
+    pub rdata: RData,
+}
+
+impl<'a> RRecord<'a> {
+    pub fn parse(mut data: &'a [u8]) -> Result<Self, &'static str> {
+        let qname = Qname::parse(data);
+        data = &data[qname.length()..];
+        debug_assert!(data.len() >= 10);
+
+        let r_type = u16::from_be_bytes([data[0], data[1]]);
+        let class = u16::from_be_bytes([data[2], data[3]]);
+        let ttl = u32::from_be_bytes([data[4], data[5], data[6], data[7]]);
+        let rdlength = u16::from_be_bytes([data[8], data[9]]);
+
+        data = &data[2 + 2 + 4 + 2..];
+
+        let rdata = Self::parse_rdata(r_type, data);
+
+        Ok(Self {
+            name: qname,
+            r_type,
+            class,
+            ttl,
+            rdlength,
+            rdata,
+        })
+    }
+
+    fn parse_rdata(r_type: u16, data: &[u8]) -> RData {
+        match r_type {
+            1 => RData::A([data[0], data[1], data[2], data[3]]),
+
+            _ => unimplemented!(),
+        }
+    }
+
+    pub fn write_to(self, buf: &mut Vec<u8>) {
+        buf.reserve(self.length());
+
+        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.rdata.write_to(buf);
+    }
+
+    pub fn length(&self) -> usize {
+        self.name.length() + 2 + 2 + 4 + 2 + self.rdlength as usize
+    }
+}
+
+#[derive(Debug)]
+pub 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),
+        }
+    }
+}