ℹ️ Info: This script can not be used on its own but requires the base installation. See main README for details.
This script reads server state from netwatch and manages used DNS and DoH (DNS over HTTPS) servers.
Just install the script:
$ScriptInstallUpdate netwatch-dns;
Then add a scheduler to run it periodically:
/system/scheduler/add interval=1m name=netwatch-dns on-event="/system/script/run netwatch-dns;" start-time=startup;
The DNS and DoH servers to be checked have to be added to netwatch with specific comment:
/tool/netwatch/add comment="doh" host=1.1.1.1;
/tool/netwatch/add comment="dns" host=8.8.8.8;
/tool/netwatch/add comment="doh, dns" host=9.9.9.9;
This will configure cloudflare-dns for DoH (https://1.1.1.1/dnsquery), and
google-dns and quad-nine for regular DNS (8.8.8.8,9.9.9.9) if up.
If cloudflare-dns is down the script will fall back to quad-nine for DoH.
Giving a specific query url for DoH is possible:
/tool/netwatch/add comment="doh, doh-url=https://dns.nextdns.io/dns-query" host=199.247.16.158;
Note that using a name in DoH url may introduce a chicken-and-egg issue!
Adding a static DNS record has the same result for the url, but always resolves to the same address.
/ip/dns/static/add name="dns.nextdns.io" address=199.247.16.158;
/tool/netwatch/add comment="doh" host=199.247.16.158;
Be aware that you have to keep the ip address in sync with real world manually!
Importing a certificate automatically is possible. You may want to find the certificate name from browser.
/tool/netwatch/add comment="doh, doh-cert=DigiCert Global Root G2" host=1.1.1.1;
/tool/netwatch/add comment="doh, doh-cert=DigiCert Global Root G3" host=9.9.9.9;
/tool/netwatch/add comment="doh, doh-cert=GTS Root R1" host=8.8.8.8;
Sometimes using just one specific (possibly internal) DNS server may be desired, with fallback in case it fails. This is possible as well:
/tool/netwatch/add comment="dns" host=10.0.0.10;
/tool/netwatch/add comment="dns-fallback" host=1.1.1.1;
Netwatch entries can be created to work with both - this script and netwatch-notify. Just give options for both:
/tool/netwatch/add comment="doh, notify, name=cloudflare-dns" host=1.1.1.1;
Also this allows to update host address, see option resolve.