DNS-over-TCP seems to not be supported, bricks HTTP(s) monitors

[skedastically]

📑 I have found these related issues/pull requests

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🛡️ Security Policy

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Description

When configuring DNS over TCP using the options use-vc option, Uptime Kuma fails to resolve any domains and red out on all HTTP(s) monitors. This seems to be caused by DNS over TCP not being supported by Uptime Kuma.

👟 Reproduction steps

1. Configure /etc/resolv.conf on host as follows:

options use-vc
nameserver 9.9.9.9

2. Start Uptime Kuma

Container's /etc/resolv.conf:

$ podman exec uptime-kuma cat /etc/resolv.conf
search dns.podman
nameserver 192.168.80.1
nameserver fdfc:3c2c:255c:c286::1
options use-vc

👀 Expected behavior

DNS will resolve normally and Uptime Kuma works as before.

😓 Actual Behavior

The following was logged. Same errors also shown on web UI.

<datetime> [MONITOR] WARN: Monitor #27 'Test': Failing: getaddrinfo EAI_AGAIN example.org | Interval: 60 seconds | Type: http | Down Count: 0 | Resend Interval: 0

The following commands inside the container also fails:

$ podman exec -it uptime-kuma bash
node@uptime-kuma:/app$ curl example.org
curl: (6) Could not resolve host: example.org

Peculiarly, curl works when IPv4 or IPv6 is specified:

node@uptime-kuma:/app$ curl -4 example.org
<website stuff>
node@uptime-kuma:/app$ curl -6 example.org
<website stuff>

🐻 Uptime-Kuma Version

1.23.15

💻 Operating System and Arch

Linux aarch64

🌐 Browser

Firefox

🖥️ Deployment Environment

• Runtime: Podman
• Database: sqlite
• Filesystem used to store the database on:
• number of monitors:

📝 Relevant log output

No response

[skedastically]

Workaround

Use a different --dns-option in the container to disable forcing TCP queries. For me an empty comment (#) to be inserted into options would works fine.

podman-compose.yml:

services:
 uptime-kuma:
    ...
    dns_opt: ["#"]

$ podman exec uptime-kuma cat /etc/resolv.conf
search dns.podman
nameserver 192.168.80.1
nameserver fdfc:3c2c:255c:c286::1
options #

[louislam]

The following commands inside the container also fails:

If it is also failed inside the container, it is probably a Docker issue. Change it to the help tag.