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