77 lines
2.1 KiB
Rust
77 lines
2.1 KiB
Rust
extern crate dns_parser;
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use std::env;
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use std::error::Error;
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use std::io::{Read, Write};
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use std::net::TcpStream;
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use std::process;
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use dns_parser::{Builder, Packet, RData, ResponseCode};
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use dns_parser::rdata::a::Record;
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use dns_parser::{QueryType, QueryClass};
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fn main() {
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let mut code = 0;
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for name in env::args().skip(1) {
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match resolve(&name) {
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Ok(()) => {},
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Err(e) => {
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eprintln!("Error resolving {:?}: {}", name, e);
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code = 1;
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}
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}
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}
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process::exit(code);
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}
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fn resolve(name: &str) -> Result<(), Box<Error>> {
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let mut conn = TcpStream::connect("127.0.0.1:53")?;
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let mut builder = Builder::new_query(1, true);
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builder.add_question(name, false, QueryType::A, QueryClass::IN);
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let packet = builder.build().map_err(|_| "truncated packet")?;
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let psize = [((packet.len() >> 8) & 0xFF) as u8,
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(packet.len() & 0xFF) as u8];
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conn.write_all(&psize[..])?;
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conn.write_all(&packet)?;
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let mut buf = vec![0u8; 4096];
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let mut off = 0;
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let pkt = loop {
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if buf.len() - off < 4096 {
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buf.extend(&[0u8; 4096][..]);
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}
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match conn.read(&mut buf[off..]) {
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Ok(num) => {
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off += num;
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if off < 2 { continue; }
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let bytes = ((buf[0] as usize) << 8) | buf[1] as usize;
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if off < bytes + 2 {
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continue;
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}
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if num == 0 {
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return Err("Partial packet received".into());
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}
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break Packet::parse(&buf[2..off])?;
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}
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Err(e) => {
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return Err(Box::new(e));
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}
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}
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};
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if pkt.header.response_code != ResponseCode::NoError {
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return Err(pkt.header.response_code.into());
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}
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if pkt.answers.len() == 0 {
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return Err("No records received".into());
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}
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for ans in pkt.answers {
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match ans.data {
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RData::A(Record(ip)) => {
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println!("{}", ip);
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}
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_ => {} // ignore
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}
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}
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Ok(())
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}
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