WireGuard DNS Issues After Openresolv Update

The Problem: Empty resolv.conf with WireGuard

Have you ever experienced that frustrating moment when your WireGuard VPN connection suddenly stops working after a system update? You try to connect, and then bam! DNS lookups fail, leaving you unable to access anything online. This is exactly what happened to me on the Manjaro testing branch after updating openresolv from version 3.17.0-1 to 3.17.2-1. Suddenly, my automatic WireGuard VPN connection was rendered useless, with error messages indicating that DNS couldn't resolve entries on localhost. The culprit? A completely empty /etc/resolv.conf file. Normally, my system relies on my router's IP address for DNS resolution when the VPN is inactive, and this information is readily available in resolv.conf. However, with the VPN active and the openresolv update, this crucial file was stripped bare. It's a peculiar issue, especially since the VPN should ideally be pushing its own DNS servers to ensure seamless connectivity. The fact that disabling the VPN instantly restored the router's DNS entry in resolv.conf pointed strongly towards a conflict or a bug introduced in the openresolv package itself. This situation highlights the delicate balance of network configurations and how a single package update can have cascading effects, particularly for services that rely on dynamic DNS resolution.

Troubleshooting the DNS Mishap

When faced with this empty resolv.conf scenario, my first instinct was to try and force an update while the WireGuard VPN was still active. I ran the command sudo resolvconf -u, hoping to coax the system into writing the necessary DNS information. However, this only revealed a more specific error message: /usr/bin/resolvconf: line 999: fd7d:76ee:e68f:a993::1: command not found. This error was particularly interesting because fd7d:76ee:e68f:a993::1 is the Unique Local Address (ULA) for the internal DNS server provided by my VPN. The fact that resolvconf was trying to execute this IP address as a command clearly indicated a parsing or handling error within the resolvconf script itself, likely introduced in the newer version. It wasn't just failing to write the DNS servers; it was actively misinterpreting them. This gave me a strong lead: the issue wasn't with WireGuard itself, but with how the updated openresolv package was processing the DNS information being provided by the VPN. The previous version, 3.17.0, had no such issues, making the diagnosis even clearer. It's a good reminder that sometimes, the simplest explanation – a bug in a recently updated component – is the correct one, especially when a downgrade immediately resolves the problem. This systematic approach to troubleshooting, from observing the symptoms to identifying specific error messages, is crucial for pinpointing the root cause of network configuration problems.

The Solution: A Simple Downgrade

Given the clear evidence that the openresolv update was the source of the problem, the most straightforward solution was to revert to the previous, working version. I downgraded openresolv from 3.17.2-1 back to 3.17.0. The moment this was done, my WireGuard VPN started connecting flawlessly again. Upon checking /etc/resolv.conf, I was relieved to see it populated with the correct DNS server information: nameserver 10.128.0.1 and nameserver fd7d:76ee:e68f:a993::1. This confirmed that the issue was indeed with the newer openresolv package and its inability to correctly handle the DNS configuration pushed by WireGuard. It's a stark reminder that even minor version bumps in system components can introduce significant regressions, especially in complex network setups involving VPNs. While downgrading is a practical fix, it's not a long-term solution, as it means I'll be missing out on potential bug fixes and improvements in future openresolv releases. However, for immediate functionality, it was the necessary step. This experience underscores the importance of keeping a close eye on system updates, especially on testing or rolling-release distributions like Manjaro. Sometimes, waiting for a patch or further investigation before applying an update can save a lot of troubleshooting headaches. For now, I'll be holding off on updating openresolv until I see confirmation that this specific DNS handling bug has been addressed.

Understanding resolv.conf and Network Configuration

To truly appreciate the impact of openresolv on resolv.conf, it's helpful to understand what these components do. /etc/resolv.conf is a critical file in Linux and other Unix-like systems. It tells the system which DNS (Domain Name System) servers to query to translate human-readable domain names (like www.google.com) into machine-readable IP addresses (like 172.217.160.142). Traditionally, this file was manually edited or updated by network management tools like NetworkManager or dhcpcd. However, openresolv (and its predecessor resolvconf) provides a more sophisticated framework for managing DNS resolution configurations. It acts as an intermediary, receiving DNS information from various sources (like DHCP clients, VPN clients, or network managers) and consolidating it into a coherent configuration for the system. When a WireGuard VPN connects, it often pushes specific DNS server addresses to be used while the tunnel is active. This ensures that your DNS queries are routed through the VPN, enhancing privacy and security. The openresolv service is supposed to receive this information from the WireGuard client and then update /etc/resolv.conf accordingly. In my case, the update to openresolv 3.17.2-1 failed to correctly process the DNS information from WireGuard, leaving resolv.conf empty. This meant that even though the VPN was technically connected, the system had no idea where to send DNS requests, effectively breaking internet connectivity. The error message about executing an IP address as a command highlighted a flaw in openresolv's parsing logic, preventing it from correctly writing the nameserver entries. Understanding this interaction between WireGuard, openresolv, and resolv.conf is key to diagnosing and resolving such network configuration issues. The configuration file /etc/netctl/dhcp mentioned in the context, which defines a basic DHCP Ethernet connection with IPv6 stateless autoconfiguration, also plays a role in the initial network setup, but the specific issue arose from how the dynamic DNS updates were handled once the VPN was established.

Future Considerations and Workarounds

While downgrading openresolv resolved my immediate WireGuard DNS problem, it's not a sustainable solution. As users of a rolling-release distribution like Manjaro, we generally want to stay updated to benefit from the latest security patches and features. Therefore, the next steps involve monitoring the situation and exploring potential workarounds or permanent fixes. Firstly, it's crucial to report this bug to the Manjaro developers and the openresolv maintainers. Providing detailed information, including the error messages and the steps to reproduce the issue, is vital for them to identify and fix the bug. I've already done this, and hopefully, a patched version will be released soon. In the meantime, I can consider adding WireGuard's DNS servers directly to my system's static DNS configuration if possible, although this would bypass openresolv entirely and might not be ideal. Another approach could be to investigate alternative DNS management tools or scripts that might be more resilient to such issues, though this would add complexity. For users who don't want to rely on downgrading, a temporary workaround might involve manually editing /etc/resolv.conf after each VPN connection, but this is highly impractical and prone to errors. It’s also worth checking the WireGuard configuration itself. Sometimes, specific DNS settings within the wg0.conf (or similar) file might need adjustment, although in this case, the issue seemed external to the WireGuard configuration itself. The key is to balance immediate functionality with long-term system health and security. Staying informed about bug reports and package updates related to openresolv and network management in general is essential for proactive system administration. For further insights into DNS resolution and management on Linux systems, you can refer to the resolv.conf man page or explore the WireGuard documentation for network setup best practices.