netbox-ddns/netbox_ddns/background_tasks.py

import logging
from typing import List, Optional

import dns.query
import dns.rdatatype
import dns.resolver
from django.db import IntegrityError
from django.db.models.functions import Length
from django_rq import job
from dns import rcode
from netaddr import ip

from netbox_ddns.models import ACTION_CREATE, ACTION_DELETE, DNSStatus, ReverseZone, Zone
from netbox_ddns.utils import normalize_fqdn

logger = logging.getLogger('netbox_ddns')


def get_zone(dns_name: str) -> Optional[Zone]:
    # Generate all possible zones
    zones = []
    parts = dns_name.lower().split('.')
    for i in range(len(parts)):
        zones.append('.'.join(parts[-i - 1:]))

    # Find the zone, if any
    return Zone.objects.filter(name__in=zones).order_by(Length('name').desc()).first()


def get_soa(dns_name: str) -> str:
    parts = dns_name.rstrip('.').split('.')
    for i in range(len(parts)):
        zone_name = normalize_fqdn('.'.join(parts[i:]))

        try:
            dns.resolver.query(zone_name, dns.rdatatype.SOA)
            return zone_name
        except dns.resolver.NoAnswer:
            # The name exists, but has no SOA. Continue one level further up
            continue
        except dns.resolver.NXDOMAIN as e:
            # Look for a SOA record in the authority section
            for query, response in e.responses().items():
                for rrset in response.authority:
                    if rrset.rdtype == dns.rdatatype.SOA:
                        return rrset.name.to_text()


def get_reverse_zone(address: ip.IPAddress) -> Optional[ReverseZone]:
    # Find the zone, if any
    zones = list(ReverseZone.objects.filter(prefix__net_contains=address))
    if not zones:
        return None

    zones.sort(key=lambda zone: zone.prefix.prefixlen)
    return zones[-1]


def status_update(output: List[str], operation: str, response) -> None:
    code = response.rcode()

    if code == dns.rcode.NOERROR:
        message = f"{operation} successful"
        logger.info(message)
    else:
        message = f"{operation} failed: {dns.rcode.to_text(code)}"
        logger.error(message)

    output.append(message)


def create_forward(dns_name: str, address: ip.IPAddress, status: Optional[DNSStatus], output: List[str]):
    zone = get_zone(dns_name)
    if zone:
        logger.debug(f"Found zone {zone.name} for {dns_name}")
        if status:
            status.forward_action = ACTION_CREATE

        # Check the SOA, we don't want to write to a parent zone if it has delegated authority
        soa = get_soa(dns_name)
        if soa == zone.name:
            record_type = 'A' if address.version == 4 else 'AAAA'
            update = zone.server.create_update(zone.name)
            update.add(
                dns_name,
                zone.ttl,
                record_type,
                str(address)
            )
            response = dns.query.udp(update, zone.server.address)
            status_update(output, f'Adding {dns_name} {record_type} {address}', response)
            if status:
                status.forward_rcode = response.rcode()
        else:
            logger.warning(f"Can't update zone {zone.name} for {dns_name}, "
                           f"it has delegated authority for {soa}")
            if status:
                status.forward_rcode = rcode.NOTAUTH
    else:
        logger.debug(f"No zone found for {dns_name}")


def delete_forward(dns_name: str, address: ip.IPAddress, status: Optional[DNSStatus], output: List[str]):
    zone = get_zone(dns_name)
    if zone:
        logger.debug(f"Found zone {zone.name} for {dns_name}")
        if status:
            status.forward_action = ACTION_DELETE

        # Check the SOA, we don't want to write to a parent zone if it has delegated authority
        soa = get_soa(dns_name)
        if soa == zone.name:
            record_type = 'A' if address.version == 4 else 'AAAA'
            update = zone.server.create_update(zone.name)
            update.delete(
                dns_name,
                record_type,
                str(address)
            )
            response = dns.query.udp(update, zone.server.address)
            status_update(output, f'Deleting {dns_name} {record_type} {address}', response)
            if status:
                status.forward_rcode = response.rcode()
        else:
            logger.warning(f"Can't update zone {zone.name} {dns_name}, "
                           f"it has delegated authority for {soa}")
            if status:
                status.forward_rcode = rcode.NOTAUTH
    else:
        logger.debug(f"No zone found for {dns_name}")


def create_reverse(dns_name: str, address: ip.IPAddress, status: Optional[DNSStatus], output: List[str]):
    zone = get_reverse_zone(address)
    if zone and dns_name:
        record_name = zone.record_name(address)
        logger.debug(f"Found zone {zone.name} for {record_name}")
        if status:
            status.reverse_action = ACTION_CREATE

        # Check the SOA, we don't want to write to a parent zone if it has delegated authority
        soa = get_soa(record_name)
        if soa == zone.name:
            update = zone.server.create_update(zone.name)
            update.add(
                record_name,
                zone.ttl,
                'ptr',
                dns_name
            )
            response = dns.query.udp(update, zone.server.address)
            status_update(output, f'Adding {record_name} PTR {dns_name}', response)
            if status:
                status.reverse_rcode = response.rcode()
        else:
            logger.warning(f"Can't update zone {zone.name} for {record_name}, "
                           f"it has delegated authority for {soa}")
            if status:
                status.reverse_rcode = rcode.NOTAUTH
    else:
        logger.debug(f"No zone found for {address}")


def delete_reverse(dns_name: str, address: ip.IPAddress, status: Optional[DNSStatus], output: List[str]):
    zone = get_reverse_zone(address)
    if zone and dns_name:
        record_name = zone.record_name(address)
        logger.debug(f"Found zone {zone.name} for {record_name}")
        if status:
            status.reverse_action = ACTION_DELETE

        # Check the SOA, we don't want to write to a parent zone if it has delegated authority
        soa = get_soa(record_name)
        if soa == zone.name:
            update = zone.server.create_update(zone.name)
            update.delete(
                record_name,
                'ptr',
                dns_name
            )
            response = dns.query.udp(update, zone.server.address)
            status_update(output, f'Deleting {record_name} PTR {dns_name}', response)
            if status:
                status.reverse_rcode = response.rcode()
        else:
            logger.warning(f"Can't update zone {zone.name} for {record_name}, "
                           f"it has delegated authority for {soa}")
            if status:
                status.reverse_rcode = rcode.NOTAUTH
    else:
        logger.debug(f"No zone found for {address}")


@job
def dns_create(dns_name: str, address: ip.IPAddress, forward=True, reverse=True, status: DNSStatus = None):
    output = []

    if forward:
        create_forward(dns_name, address, status, output)
    if reverse:
        create_reverse(dns_name, address, status, output)

    if status:
        try:
            status.save()
        except IntegrityError:
            # Race condition when creating?
            status.save(force_update=True)

    return ', '.join(output)


@job
def dns_delete(dns_name: str, address: ip.IPAddress, forward=True, reverse=True, status: DNSStatus = None):
    output = []

    if forward:
        delete_forward(dns_name, address, status, output)
    if reverse:
        delete_reverse(dns_name, address, status, output)

    if status:
        try:
            status.save()
        except IntegrityError:
            # Race condition when creating?
            status.save(force_update=True)

    return ', '.join(output)