Gitlab-ci shared runner and docker : missing gateway in network

Hi, I have a question regarding gitlab-ci and how it handles the network layer.

When I run docker network inspect bridge in a gitlab runner, there is an important missing field (IPAM.Config.Gateway) and I really do not understand why. After a lot a googling, I found that the only way to hack this is to restart the docker service but it seems impossible to do that (it crashes the job).

Here is a repro :

stages:
  - build

variables:
  GITLAB_REGISTRY_TOKEN: $CI_REGISTRY_PASSWORD
  DOCKER_DRIVER: overlay2
  DOCKER_BUILDKIT: 1
  FF_NETWORK_PER_BUILD: "true"

image:
  name: docker:20.10.14-dind-alpine3.15

services:
  - docker:dind

docker-build:
  stage: build
  script:
    - docker -v
    - docker network inspect bridge

I already tried to create a network manually via docker network create --driver bridge testbridge but the result is the same.

I depend on the gateway because my docker services have to communicate between themselves during build time (a rest api has to feed a static generation service).

Thanks for reading me