bug: Using IPv6 addresses in GATEWAY_LISTEN causes error

[dietrich-iti]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Using IPv6 address(es) in the GATEWAY_LISTEN environment variable causes the LocalStack CLI to crash. This appears to be due to the way HostAndPort.parse() is implemented -- it assumes that the only meaning of a colon in its input would be to separate a host and a port. Naturally this leads to trouble if I give it something like '::1'.

Expected Behavior

The CLI accepts IPv6 addresses in GATEWAY_LISTEN, handling them the same way it does IPv4.

How are you starting LocalStack?

With the localstack script

Steps To Reproduce

How are you starting localstack (e.g., bin/localstack command, arguments, or docker-compose.yml)

GATEWAY_LISTEN=127.0.0.1,::1 localstack start -d

Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

N/A

Environment

- OS: macOS Sonoma 14.4.1
- LocalStack:
  LocalStack version: 3.4.1.dev
  LocalStack Docker image sha: 53cb4b3e335239cc8542eb0fbd9a24be03c1bafecb7d003643209b39c58b9751
  LocalStack build date: 2024-04-25
  LocalStack build git hash: 9287822

Anything else?

I encountered this issue while trying to work around another issue:

I was setting up the LocalStack Github CI Action. I configured my code to use http://localhost:4566 as the AWS endpoint URL, so it would talk to the port being published by the LocalStack Docker container that the CI Action sets up. Unfortunately, in that environment localhost resolves to the IPv6 loopback address ::1, so the connection from my code to LocalStack was failing. I tried to mitigate this by using GATEWAY_LISTEN to effectively add [::1]:4566 to the ports published by the container, which is where I discovered the problem.

Ultimately I was able to find two workarounds. One was just using the IPv4 loopback address 127.0.0.1 directly, instead of localhost. The other, more satisfying one was setting DOCKER_FLAGS="-p [::1]:4566:4566". That manages to make it to the place where the container is created, so it lets me use localhost without any trouble.

If it would be appropriate, I can file a separate bug for the issue of "Docker container doesn't publish its ports to IPv6" too.

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[MarcelStranak]

Hi @dietrich-iti,
We provide network troubleshooting guides and also GitHub Actions guide.

LocalStack only binds to IPv4 addresses (e.g. 127.0.0.1).