From f5cd9095e4c10296fe8f5d1f491e15479ae38d8a Mon Sep 17 00:00:00 2001 From: CarlosFelipeOR Date: Fri, 21 Aug 2026 16:46:45 -0300 Subject: [PATCH] Set explicit DNS for docker containers to avoid IPv6 nameserver timeouts Containers inherit the runner's uplink resolvers, and the first two are IPv6 (2a01:4ff:ff00::add:1/2). Container IPv6 uses an unroutable prefix, so glibc waits out the timeout on each before falling through to IPv4. Measured on a runner, `getent hosts base.invalid`: default (4 nameservers, IPv6 first) ~14s --dns=185.12.64.1 ~2.9s --dns=185.12.64.2 0.00s --dns=1.1.1.1 0.01s This blocks 04070_url_base_setting, which does 25 lookups of .invalid hostnames in series and takes ~950s instead of ~8s. See #2250. Cloudflare rather than the Hetzner resolvers so the setting also holds on Scaleway and AWS runners. --- .github/actions/docker_setup/action.yml | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/.github/actions/docker_setup/action.yml b/.github/actions/docker_setup/action.yml index 56f713fa59d1..6b105f813cef 100644 --- a/.github/actions/docker_setup/action.yml +++ b/.github/actions/docker_setup/action.yml @@ -20,7 +20,8 @@ runs: sudo cat < /etc/docker/daemon.json { "ipv6": true, - "fixed-cidr-v6": "${{ env.ipv6_subnet }}" + "fixed-cidr-v6": "${{ env.ipv6_subnet }}", + "dns": ["1.1.1.1", "1.0.0.1"] } EOT sudo chown root:root /etc/docker/daemon.json