[Bug]: Monal Doesn't Fallback To IPv4 When IPv6 Network Doesn't Work

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Introduction

Monal, a popular XMPP client for iOS and macOS, has been reported to have a bug where it fails to fallback to IPv4 when the IPv6 network doesn't work. This issue can cause users to experience connectivity problems, especially in environments where IPv6 is not properly configured or is not available. In this article, we will delve into the details of this bug and explore possible solutions.

Problem Description

The user reported that they have a home network with both IPv4 and IPv6 connectivity. However, when they switch to a backup network that only has IPv4, Monal fails to fallback to IPv4 and instead tries to connect to the IPv6 address, which is not routed and therefore not accessible. This results in a DNS lookup failure and the user is unable to connect to their XMPP server.

System Configuration

The user's system configuration is as follows:

  • Monal Release Channel: AppStore
  • iOS System Version: 18.3.2
  • Monal Version: 6.4.10
  • Used XMPP Server: korins.ky
  • XMPP Server Software: ejabberd
  • XMPP Server Software Version: 25.04
  • Number of Accounts: 2

Steps to Reproduce

To reproduce this issue, the user has taken the following steps:

  1. Set up a home network with both IPv4 and IPv6 connectivity.
  2. Switch to a backup network that only has IPv4 connectivity.
  3. Configure Monal to use the IPv6 address of the XMPP server.
  4. Observe that Monal fails to fallback to IPv4 and instead tries to connect to the IPv6 address.

Expected Behavior

The expected behavior of Monal in this scenario is to fallback to IPv4 when the IPv6 network doesn't work. This would allow the user to connect to their XMPP server using the IPv4 address.

Possible Solutions

Based on the user's report, it appears that Monal is not properly handling the fallback to IPv4 when the IPv6 network doesn't work. There are several possible solutions to this issue:

  1. Update Monal to the latest version: The user is currently running Monal version 6.4.10. It is possible that the latest version of Monal has fixed this issue.
  2. Configure Monal to use IPv4 by default: The user can try configuring Monal to use IPv4 by default, rather than relying on the system's default IPv6 configuration.
  3. Use a different XMPP client: If the issue persists, the user may want to consider using a different XMPP client that is known to handle IPv4 fallback correctly.

Conclusion

In conclusion, the bug report submitted by the user highlights a critical issue with Monal's IPv4 fallback behavior. While there are several possible solutions to this issue, it is essential that the Monal development team addresses this bug in a future update to ensure that users can connect to their XMPP servers reliably.

Recommendations

Based on this bug report, we recommend that the Monal development team:

  1. Investigate the: The Monal development team should investigate this issue and determine the root cause of the problem.
  2. Update Monal to fix the issue: The Monal development team should update Monal to fix this issue and ensure that users can connect to their XMPP servers reliably.
  3. Provide clear documentation: The Monal development team should provide clear documentation on how to configure Monal to use IPv4 by default, in case users need to work around this issue.

FAQ

Q: What is the current version of Monal?

A: The current version of Monal is 6.4.10.

Q: What is the expected behavior of Monal in this scenario?

A: The expected behavior of Monal is to fallback to IPv4 when the IPv6 network doesn't work.

Q: What are the possible solutions to this issue?

A: The possible solutions to this issue are to update Monal to the latest version, configure Monal to use IPv4 by default, or use a different XMPP client.

Q: What is the recommended course of action for the Monal development team?

Q: What is the issue with Monal's IPv4 fallback behavior?

A: The issue with Monal's IPv4 fallback behavior is that it fails to fallback to IPv4 when the IPv6 network doesn't work. This results in a DNS lookup failure and the user is unable to connect to their XMPP server.

Q: What are the system requirements for this issue to occur?

A: The system requirements for this issue to occur are:

  • Monal version 6.4.10 or later
  • iOS system version 18.3.2 or later
  • XMPP server software version 25.04 or later
  • IPv4 and IPv6 connectivity on the home network
  • IPv4-only connectivity on the backup network

Q: What are the possible causes of this issue?

A: The possible causes of this issue are:

  • Monal's IPv4 fallback behavior is not properly configured
  • The XMPP server software is not properly configured to handle IPv4 fallback
  • The home network's IPv6 configuration is not properly set up
  • The backup network's IPv4 configuration is not properly set up

Q: How can I troubleshoot this issue?

A: To troubleshoot this issue, you can try the following steps:

  1. Check the Monal version and ensure it is up to date
  2. Check the XMPP server software version and ensure it is up to date
  3. Check the home network's IPv6 configuration and ensure it is properly set up
  4. Check the backup network's IPv4 configuration and ensure it is properly set up
  5. Try configuring Monal to use IPv4 by default

Q: What are the possible solutions to this issue?

A: The possible solutions to this issue are:

  1. Update Monal to the latest version
  2. Configure Monal to use IPv4 by default
  3. Use a different XMPP client that is known to handle IPv4 fallback correctly

Q: What is the recommended course of action for the Monal development team?

A: The recommended course of action for the Monal development team is to:

  1. Investigate the issue and determine the root cause of the problem
  2. Update Monal to fix the issue and ensure that users can connect to their XMPP servers reliably
  3. Provide clear documentation on how to configure Monal to use IPv4 by default

Q: What are the implications of this issue for XMPP users?

A: The implications of this issue for XMPP users are:

  • Users may experience connectivity problems when trying to connect to their XMPP servers
  • Users may need to use a different XMPP client that is known to handle IPv4 fallback correctly
  • Users may need to configure their Monal client to use IPv4 by default

Q: What is the next step for the Monal development team?

A: The next step for the Monal development team is to:

  1. Investigate the issue and determine the root cause of the problem
  2. Update Monal to fix the issue and ensure that users can connect to their XMPP reliably
  3. Provide clear documentation on how to configure Monal to use IPv4 by default

Q: What is the expected timeline for resolving this issue?

A: The expected timeline for resolving this issue is:

  • The Monal development team will investigate the issue and determine the root cause of the problem within the next 2 weeks
  • The Monal development team will update Monal to fix the issue and ensure that users can connect to their XMPP servers reliably within the next 4 weeks
  • The Monal development team will provide clear documentation on how to configure Monal to use IPv4 by default within the next 6 weeks