Function set_ttl

src/dns.rs:385–405

(packet: &mut [u8], ttl: u32)

}

pub fn set_ttl(packet: &mut [u8], ttl: u32) -> Result<(), 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));
    let rrcount = ancount as usize + nscount as usize + arcount as usize;
    offset = traverse_rrs_mut(packet, offset, rrcount, |packet, offset| {
        let qtype = BigEndian::read_u16(&packet[offset..]);
        if qtype != DNS_TYPE_OPT {
            BigEndian::write_u32(&mut packet[offset + 4..], ttl)
        }
        Ok(())
    })?;
    ensure!(packet_len == offset, "Garbage after packet");
    Ok(())
}

fn add_edns_section(packet: &mut Vec<u8>, max_payload_size: u16) -> Result<(), Error> {
    let opt_rr: [u8; 11] = [