Function query_meta

src/dns.rs:602–646

(packet: &mut Vec<u8>)

}

pub fn query_meta(packet: &mut Vec<u8>) -> Result<Option<String>, Error> {
    let packet_len = packet.len();
    ensure!(packet_len > DNS_OFFSET_QUESTION, "Short packet");
    ensure!(packet_len <= DNS_MAX_PACKET_SIZE, "Large packet");
    ensure!(qdcount(packet) == 1, "No question");
    let mut offset = skip_name(packet, DNS_OFFSET_QUESTION)?;
    assert!(offset > DNS_OFFSET_QUESTION);
    ensure!(packet_len - offset >= 4, "Short packet");
    offset += 4;
    let (ancount, nscount, arcount) = (ancount(packet), nscount(packet), arcount(packet));
    offset = traverse_rrs(
        packet,
        offset,
        ancount as usize + nscount as usize,
        |_offset| Ok(()),
    )?;
    let mut token = None;
    traverse_rrs(packet, offset, arcount as _, |mut offset| {
        let qtype = BigEndian::read_u16(&packet[offset..]);
        let qclass = BigEndian::read_u16(&packet[offset + 2..]);
        if qtype != DNS_TYPE_TXT || qclass != DNS_CLASS_INET {
            return Ok(());
        }
        let len = BigEndian::read_u16(&packet[offset + 8..]) as usize;
        offset += 10;
        ensure!(packet_len - offset >= len, "Short packet");
        let rrdata = &packet[offset..offset + len];
        parse_txt_rrdata(rrdata, |txt| {
            if txt.len() < 7 || !txt.starts_with("token:") {
                return Ok(());
            }
            ensure!(token.is_none(), "Duplicate token");
            let found_token = &txt[6..];
            let found_token = found_token.to_owned();
            token = Some(found_token);
            Ok(())
        })?;
        Ok(())
    })?;
    if token.is_some() {
        arcount_clear(packet)?;
        packet.truncate(offset);
    }
    Ok(token)
}

pub fn serve_nxdomain_response(client_packet: Vec<u8>) -> Result<Vec<u8>, Error> {
    ensure!(client_packet.len() >= DNS_HEADER_SIZE, "Short packet");