Reproducible slow (30 seconds) DNS resolution on Ubuntu 24.04
I use Firefox 134.0.2 (64-bit) on Ubuntu 24.04.
Some (not all) web sites show up only after a delay of exactly 30 seconds. The attached screenshot shows that this delay is due to DNS resolution. This behavior is reproducible by simply closing Firefox, opening it again and entering the same web site once more. Once this initial delay of 30 seconds for DNS resolving has passed the web site can be browsed normally.
Using Google Chrome, Opera or even the Tor Browser on the same system works without any significant delay. Also a DNS lookup from the console returns data almost immediately.
As the delay is always exactly 30 seconds this looks like some DNS resolver timeout only showing up when using Firefox.
Neither starting Firefox in Troubleshoot Mode nor (as often suggested) disabling IPV6 for DNS by setting network.dns.disableIPv6 to true did help.
Any idea how to fix this 30 seconds delay?
Many thanks for any help, Felix
Wšykne wótegrona (8)
Thanks for the tip! I have attached a screenshot from the bisect result and this is the contents of the build info window:
app_name: firefox build_date: 2024-12-03 14:55:16.908000 build_file: /home/felix/.mozilla/mozregression/persist/fb9f6b58f4db-pgo--autoland--target.tar.xz build_type: integration build_url: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/LjYzS4xTTv-8LTCa4-fY8g/runs/0/artifacts/public%2Fbuild%2Ftarget.tar.xz changeset: fb9f6b58f4db1dd50bd71e1c8b65238efe6386b4 pushlog_url: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=5b8d2c7e3f1f707f7fd8cea7c7eabd86e0abd3f0&tochange=fb9f6b58f4db1dd50bd71e1c8b65238efe6386b4 repo_name: autoland repo_url: https://hg.mozilla.org/integration/autoland task_id: LjYzS4xTTv-8LTCa4-fY8g
If useful I can provide the entire bisecting log.
Thanks, this bug is secured, I don't really know what's going on there, it's something about mismatched NPN token.
As a test, try to go to about:config and switch security.ssl.enable_alpn to false + restart.
PS. I've reached to the Network team, I hope they will say something about it.
Wót TyDraniu změnjony
Sadly disabling ALPN did not help, thanks anyway. Just for testing, I also temporarily disabled the HTTPS record in the DNS server. This too did not help.
Let me know if there is anything else I can contribute to fix this problem.
Concerning the influence of the DNS HTTPS record being present or not, the statement in my previous post was wrong, sorry. As usual I had not enough patience when playing with DNS entries.
The 30 seconds delay with Firefox occurs only when the HTTPS record is present in the DNS. If the HTTPS record in the DNS is missing, Firefox is as fast as Google Chrome.
Just in case, the HTTPS record looks like this: www.ltec.ch. 3600 IN HTTPS 10 . alpn="h3,h2"
Ah, OK. Everything is clear now.
Musyśo se pla swójogo konta pśizjawiś, aby na pśinoski wótegronił. Pšosym stajśo pšašanje, jolic hyšći njamaśo wužywaŕske konto.