knot-dns-users July 2025

knot-dns-users@lists.nic.cz

5 participants
4 discussions

Re: Catalog zones when secondary to other servers

by Chris Wopat

I am definitely interested in examples! Reading up on groups, is it that 'group A' may represent 'customer A' and have a specific set of Primary/Master nameservers, Group B == Customer B, different Primary, and so on? (also fixed to be plain text - hope this is more legible in the archives) --Chris

5 months, 3 weeks

Catalog zones when secondary to other servers

by Chris Wopat

Hello DNS people, I am exploring migrating from PowerDNS where we have a hidden primary (ns0) and two public resolvers (ns1/ns2) using SQL replication, to instead use Knot DNS for ns1/ns2 and Catalog zones to update them. ns0 would remain Powerdns (frontend, zone edits for customers, etc). We are looking at changing due to performance issues - "dns water torture" or "random subdomain attacks" or whatever we're calling this these days. Our test environment is more or less setup as listed here: * https://nick.bouwhuis.net/posts/2024-12-31-catalog-zones-powerdns-knot/ This is similar to the architectured listed here: * https://indico.dns-oarc.net/event/47/contributions/1008/attachments/963/185… (Klaus from nic.at) For some zones, we're secondary to a customer's zone. In this case the Primariy IPs are listed in PowerDNS metadata. I am trying to wrap my head around how this could work seamlessly, where we keep the same workflow - add the zone to PowerDNS, then it gets replicated with catalog zone to ns1/ns2 (knot). Does anyone have this working? Secondary is mentioned in the PDF above but no details about that are listed. The issues appear to be at least these two things: 1) How to tell ns1/ns2 (knot) which IP's are its primaries in these zones? The only thing I can think of is a separate script to generate a knot config file with this info - effectively the same as "back in the day" with BIND. This completely negates the function of catalog zones that are secondaries. rfc9432 does address this: "Catalog zones on secondary name servers would have to be set up manually, perhaps as static configuration, similar to how ordinary DNS zones are configured when catalog zones or another automatic configuration mechanism are not in place. " That RFC then says you still have to keep it in the catalog anyhow - it's not immediately clear to me how/why - and how it could be configured per the lasts sentence (manually in knot conf) as well as in the catalog - wouldn't this be two declarations of the same zone? "Additionally, the secondary needs to be configured as a catalog consumer for the catalog zone to enable processing of the member zones in the catalog, such as automatic synchronization of the member zones for secondary service" 2) How would NOTIFY work? our hidden ns0 (powerdns) runs a copy of the zones, but ns1/ns2 would be notified from the actual primary, and our ns0 would become out of date. Does knot have something like also-notify to always notify that server? This may or may not be a problem, but the zone data would completely become stale without this. Some customers log into our web portal to view records of their secondaries and expect them to match. If anyone has operational experience with this or just a big cluebat to hit me with - let me know. Cheers, Chris

5 months, 3 weeks

Slow performance adding or deleting zones with large-ish (>480k) zones database

by robm＠fastmail.com

Hi We're noticing that as our list of zones gets larger (about 480k right now), adding a new zone or deleting an existing zone seems to continue to get slower. We are always doing our modifications as part of a transaction, and the time appears to occur in the commit phase. An example timing. # time /opt/knot/sbin/knotc ... conf-begin OK real 0m0.010s user 0m0.000s sys 0m0.010s # time /opt/knot/sbin/knotc ... conf-unset zone.domain example.com OK real 0m0.010s user 0m0.000s sys 0m0.010s # time /opt/knot/sbin/knotc ... conf-commit OK real 0m2.330s user 0m0.000s sys 0m0.009s # As you can see, it took > 2 seconds to commit the transaction that removes just the example.com zone. Similarly, it takes > 2 seconds to commit the transaction that adds the zone back. Given the time is real time and not sys/user, I presume knotc is waiting on knotd to complete the work. I used perf to record a CPU profile of knotd while the commit was running, but nothing hugely stuck out at me. 10.75% knotd libc.so.6 [.] __memcmp_avx2_movbe ◆ 6.03% knotd knotd [.] __popcountdi2 ▒ 5.89% knotd knotd [.] ns_first_leaf ▒ 5.25% knotd libc.so.6 [.] pthread_mutex_lock@@GLIBC_2.2.5 ▒ 3.85% knotd liblmdb.so.0.0.0 [.] 0x0000000000003706 ▒ 3.72% knotd knotd [.] ns_find_branch.part.0 ▒ 2.76% knotd knotd [.] trie_get_try ▒ 2.63% knotd liblmdb.so.0.0.0 [.] 0x00000000000069d2 ▒ 2.34% knotd libknot.so.14.0.0 [.] knot_dname_lf ▒ 1.92% knotd liblmdb.so.0.0.0 [.] mdb_cursor_get ▒ 1.72% knotd knotd [.] create_zonedb ▒ 1.68% knotd knotd [.] twigbit.isra.0 ▒ 1.68% knotd knotd [.] catalogs_generate ▒ 1.36% knotd knotd [.] twigoff.isra.0 ▒ 1.28% knotd knotd [.] hastwig.isra.0 ▒ 1.28% knotd knotd [.] db_code ▒ 1.27% knotd libknot.so.14.0.0 [.] find_item ▒ 1.11% knotd libknot.so.14.0.0 [.] knot_dname_size ▒ 1.04% knotd knotd [.] zonedb_reload ▒ 0.99% knotd libc.so.6 [.] _int_free ▒ 0.99% knotd liblmdb.so.0.0.0 [.] 0x0000000000003ce8 ▒ 0.96% knotd liblmdb.so.0.0.0 [.] memcmp@plt ▒ 0.95% knotd liblmdb.so.0.0.0 [.] mdb_cursor_open ▒ 0.88% knotd libc.so.6 [.] malloc ▒ 0.88% knotd knotd [.] conf_db_get ▒ 0.87% knotd knotd [.] ns_next_leaf ▒ 0.82% knotd libknot.so.14.0.0 [.] iter_set ▒ 0.75% knotd knotd [.] evsched_cancel ▒ 0.73% knotd libknot.so.14.0.0 [.] find ▒ ... Our config is pretty simple, conf-export looks like: server: rundir: "/local/knot_dns/run/" user: "nobody" pidfile: "/local/knot_dns/run/knot.pid" listen: [ ... ] log: - target: "syslog" any: "info" statistics: timer: "10" file: "/tmpfs/knot_dns_stats.yaml" database: storage: "/local/knot_dns/data" mod-stats: - id: "default" request-protocol: "on" server-operation: "on" request-bytes: "on" response-bytes: "on" edns-presence: "on" flag-presence: "on" response-code: "on" request-edns-option: "on" response-edns-option: "on" reply-nodata: "on" query-type: "on" query-size: "on" reply-size: "on" template: - id: "default" global-module: "mod-stats/default" storage: "/local/knot_dns/zones/" zone: - domain: "example.com." template: "default" ... 478,000 more domains all the same ... Current files on disk are: # ls -l /local/knot_dns/data/* /local/knot_dns/data/catalog: total 0 /local/knot_dns/data/journal: total 0 /local/knot_dns/data/keys: total 0 /local/knot_dns/data/timers: total 75880 -rw-rw---- 1 root root 77697024 Jun 24 09:26 data.mdb -rw-rw---- 1 root root 2432 Jul 17 01:05 lock.mdb /local/knot_dns/data/timing: total 0 This machine is not slow or constrained in any way. It's 24 core, 3.6Ghz, 64Gb, NVMe drives, etc. Load is very low (<1) with plenty of free resources. So what I'm wondering is: 1. Is this normal? It doesn't feel right that adding/removing a single domain takes > 2 seconds regardless of the size of the existing zone database 2. Is there any way to improve this? Doing multiple adds/deletes at once within a transaction works and we do that where we can, but there are cases where we can't do that and I'd really like to understand why this is as slow as it is. Thanks in advance Rob

5 months, 3 weeks

Knot DNS 3.4.8 release

by Daniel Salzman

Hello Knot DNS users, CZ.NIC has released Knot DNS 3.4.8! This is a maintenance version with some improvements. Changelog: https://gitlab.nic.cz/knot/knot-dns/-/releases/v3.4.8 Download: https://www.knot-dns.cz/download/ Documentation: https://www.knot-dns.cz/documentation/ Support: https://www.knot-dns.cz/support/ Regards, Daniel

5 months, 3 weeks

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knot-dns-users July 2025