Docker in Docker on Mac requires to use host.docker.internal

I want to use a mongodb testcontainer within docker (to run in CI). When I use the testcontainer on the host, all works fine. However, when I use it inside docker, I need to access the testcontainer via the host (host.docker.internal). Is there some way for get_connection_url() to always return the "right" connection url?

I tried to put together an MWE:

docker run -v "/var/run/docker.sock":"/var/run/docker.sock"  --privileged=true -it --entrypoint /bin/bash python:3.7.6
>> pip install testcontainers pymongo -q
>> python

import pymongo
from testcontainers.mongodb import MongoDbContainer

mongo = MongoDbContainer()
mongo.start()
print(mongo.get_connection_url())
# > 'mongodb://test:test@172.17.0.1:53859'

testcontainer_client = mongo.get_connection_client()
for db in testcontainer_client.list_databases(): print(db)
# > results in pymongo.errors.ServerSelectionTimeoutError

mongo_client = pymongo.MongoClient( 'mongodb://test:test@host.docker.internal:53859')
for db in mongo_client.list_databases(): print(db)
# > {'name': 'admin', 'sizeOnDisk': 102400, 'empty': False}

首先跟踪 MongoDbContainer.get_connection_url() 和 get_connection_client()，然后检查在所示的主机和 Docker-in-Docker 场景中如何确定 Docker 主机地址。复现 issue 中的 MongoDB 示例，并验证返回的 URL 和客户端在主机上以及 Docker 内部都能正常工作。