Change Details

See T308271#8225621 for background as to why this is needed. The tl;dr is that buildkitd needs to know our host's `resolv.conf` configuration in order to pass it along to containers that it spawns, yet buildkitd is currently running within a Docker container that uses a custom Docker network which overwrites `resolv.conf` with an internal Docker DNS proxy. The custom Docker network is currently serving only one purpose which is to provide a way to consistently reference the buildkitd server (by name). To retain this consistency, we'll assign a fixed IP to the buildkitd container within the default Docker network and set a runner level environment variable for `BUILDKIT_HOST` that obviates hardcoding of the IP in CI jobs.

(renamed from: //Remove use custom network for GitLab runners and buildkitd in favor of a fixed IP//; see update below) See T308271#8225621 for background as to why this is needed. The tl;dr is that buildkitd needs to know our host's `resolv.conf` configuration in order to pass it along to containers that it spawns, yet buildkitd is currently running within a Docker container that uses a custom Docker network which overwrites `resolv.conf` with an internal Docker DNS proxy. The custom Docker network is currently serving only one purpose which is to provide a way to consistently reference the buildkitd server (by name). To retain this consistency, we'll assign a fixed IP to the buildkitd container within the default Docker network and set a runner level environment variable for `BUILDKIT_HOST` that obviates hardcoding of the IP in CI jobs. **update:** Unfortunately a fixed IP cannot be allocated to containers on the default network, so we can't abandon the custom network. However, there appears to be an [[ https://github.com/moby/buildkit/blob/v0.10.4/cmd/buildkitd/config/config.go#L26 | undocumented config field for buildkitd to configure DNS options. ]] This will allow us to pass along DNS options which buildkitd will use when spawning build containers. \o/

(renamed from: //Remove use custom network for GitLab runners and buildkitd in favor of a fixed IP//; see update below) See T308271#8225621 for background as to why this is needed. The tl;dr is that buildkitd needs to know our host's `resolv.conf` configuration in order to pass it along to containers that it spawns, yet buildkitd is currently running within a Docker container that uses a custom Docker network which overwrites `resolv.conf` with an internal Docker DNS proxy. The custom Docker network is currently serving only one purpose which is to provide a way to consistently reference the buildkitd server (by name). To retain this consistency, we'll assign a fixed IP to the buildkitd container within the default Docker network and set a runner level environment variable for `BUILDKIT_HOST` that obviates hardcoding of the IP in CI jobs. **update:** Unfortunately a fixed IP cannot be allocated to containers on the default network, so we can't abandon the custom network. However, there appears to be an [[ https://github.com/moby/buildkit/blob/v0.10.4/cmd/buildkitd/config/config.go#L26 | undocumented config field for buildkitd to configure DNS options. ]] This will allow us to pass along DNS options which buildkitd will use when spawning build containers. \o/