Function serve_ip_response

src/dns.rs:694–726

(client_packet: Vec<u8>, ip: IpAddr, ttl: u32)

}

pub fn serve_ip_response(client_packet: Vec<u8>, ip: IpAddr, ttl: u32) -> Result<Vec<u8>, Error> {
    ensure!(client_packet.len() >= DNS_HEADER_SIZE, "Short packet");
    ensure!(qdcount(&client_packet) == 1, "No question");
    ensure!(
        !is_response(&client_packet),
        "Question expected, but got a response instead"
    );
    let offset = skip_name(&client_packet, DNS_HEADER_SIZE)?;
    let mut packet = client_packet;
    ensure!(packet.len() - offset >= 4, "Short packet");
    packet.truncate(offset + 4);
    an_ns_ar_count_clear(&mut packet);
    authoritative_response(&mut packet);
    ancount_inc(&mut packet)?;
    packet.write_u16::<BigEndian>(0xc000 + DNS_HEADER_SIZE as u16)?;
    match ip {
        IpAddr::V4(ip) => {
            packet.write_u16::<BigEndian>(DNS_TYPE_A)?;
            packet.write_u16::<BigEndian>(DNS_CLASS_INET)?;
            packet.write_u32::<BigEndian>(ttl)?;
            packet.write_u16::<BigEndian>(4)?;
            packet.extend_from_slice(&ip.octets());
        }
        IpAddr::V6(ip) => {
            packet.write_u16::<BigEndian>(DNS_TYPE_AAAA)?;
            packet.write_u16::<BigEndian>(DNS_CLASS_INET)?;
            packet.write_u32::<BigEndian>(ttl)?;
            packet.write_u16::<BigEndian>(16)?;
            packet.extend_from_slice(&ip.octets());
        }
    };
    Ok(packet)
}

#[cfg(test)]
mod tests {