Teleport File Transfer Issues: Troubleshooting & Solutions

Are you facing difficulties uploading or downloading files to your SSH servers through the Teleport web browser? You're not alone. Many users encounter this frustrating issue, often seeing the error message: "client source and destination addresses should be valid same TCP version non-nil IP addresses." This comprehensive guide delves into the problem, providing troubleshooting steps, potential causes, and solutions to get your file transfers back on track. We'll explore the specifics of the issue, examine the debug logs, and offer practical advice to resolve the problem effectively.

Understanding the Core Issue

The central problem lies within Teleport's inability to facilitate file transfers via its web interface. When you attempt to upload or download files using the built-in buttons, the system fails, resulting in the error message mentioned earlier. This typically indicates a network configuration problem, an incompatibility, or a bug within the Teleport software itself. This guide will help you understand the most common causes and ways to resolve them. Let's start with a deeper look at the "client source and destination addresses should be valid same TCP version non-nil IP addresses" error message. This error often surfaces because the Teleport proxy cannot correctly establish a connection for file transfer. This could be due to issues with how your network is configured, the versions of TCP being used, or problems with the IP addresses involved in the connection. Furthermore, the inability to connect could also be related to how Teleport handles the SSH sessions, including how it connects to the SSH server.

The Error Message Explained

The error message, "client source and destination addresses should be valid same TCP version non-nil IP addresses," is a key indicator of the problem. It highlights that Teleport is having trouble establishing a valid network connection for file transfer. Let's break down this message:

• Client Source and Destination Addresses: These refer to the IP addresses of your computer (the client) and the SSH server (the destination). Teleport needs to know these addresses to route the file transfer.
• Valid IP Addresses: The addresses must be correctly formatted and recognized by the network.
• Same TCP Version: The client and server must be using the same version of the TCP protocol (e.g., IPv4 or IPv6).
• Non-Nil IP Addresses: The IP addresses cannot be empty or invalid.

This error suggests that there is a misconfiguration of the network settings, or Teleport is struggling to correctly determine the necessary IP addresses for the file transfer process. Debugging the network configuration and verifying that both your client machine and the SSH server are correctly configured with appropriate IP addresses is often the first step in troubleshooting the problem. Additionally, confirming that there are no firewalls or network policies that might be blocking communication can also be vital.

Troubleshooting Steps

To troubleshoot the file transfer issue, follow these steps. By systematically investigating each area, you can identify the root cause and apply the appropriate fix. Start with the basics and gradually move to more advanced troubleshooting. Remember to test after each step to see if the issue is resolved.

Verify Network Connectivity

Ensure that your client machine, the Teleport server, and the SSH server can communicate with each other. This is the foundation for any network-based service. Check basic connectivity before attempting anything else.

1. Ping Test: From your client machine, try pinging both the Teleport server and the SSH server using their IP addresses. If you don't receive replies, there's a basic network problem.
2. Traceroute: Use the traceroute command to check the network path between your client and the SSH server. This can help identify where the connection is failing.
3. Firewall Rules: Ensure that firewalls on your client, Teleport server, and SSH server are not blocking traffic on the necessary ports (typically port 3022 for SSH and any ports Teleport uses for its proxy). Examine the rules to determine if they are configured to allow traffic between the involved entities.

Examine Teleport Configuration

Check your Teleport configuration for potential issues. The way Teleport is set up can impact the file transfer process.

1. teleport.yaml Configuration: Review your Teleport configuration file (/etc/teleport.yaml or wherever it's located) for any misconfigurations related to SSH proxying or network settings. Pay close attention to the proxy_service and ssh_service sections.
2. Proxy Settings: Verify that the proxy settings in the Teleport configuration are correct, especially if you're using a proxy server. Incorrect proxy settings can cause connectivity problems.
3. Authentication and Authorization: Ensure that the user attempting the file transfer has the necessary permissions. Teleport's role-based access control (RBAC) should be checked to make sure users have proper access.

Check SSH Server Configuration

The SSH server itself might be the source of the problem. Misconfigured SSH settings can prevent file transfers.

1. SSH Version and Configuration: Ensure that your SSH server is up-to-date and configured correctly. Review the SSH server configuration file (sshd_config) for any settings that might be interfering with file transfer, such as the AllowTcpForwarding or other security parameters.
2. Port Forwarding: If you are using port forwarding, make sure that it's correctly configured on both the Teleport server and the SSH server. Check your firewall rules as well.
3. SFTP Subsystem: Ensure the SFTP subsystem is enabled on the SSH server. SFTP (SSH File Transfer Protocol) is what Teleport uses for file transfers. It needs to be active.

Analyzing Debug Logs

The debug logs provide valuable insights into what's happening behind the scenes. Review the logs to get clues about the root cause of the file transfer issues.

Interpreting Teleport Server Logs

Analyze the Teleport server logs to understand the errors the Teleport server is encountering. These logs are stored in various places depending on the deployment; a common location is usually the system logs. You've provided an example debug log; let's break it down:

Oct 29 01:20:30 teleport teleport[421231]: 2025-10-29T01:20:30.399Z DEBU [CLIENT]    Skipping connection to the local ssh-agent. client/keyagent.go:145
Oct 29 01:20:30 teleport teleport[421231]: 2025-10-29T01:20:30.400Z DEBU [PROXY:SER] Initiating dial request cluster:main dial_params:from: "<user-ip>:49686" to: "<ssh-server-ip>:3022" reversetunnel/localsite.go:314
Oct 29 01:20:30 teleport teleport[421231]: 2025-10-29T01:20:30.401Z DEBU [HTTP:PROX] No proxy set in environment, returning direct dialer proxy/proxy.go:184
Oct 29 01:20:30 teleport teleport[421231]: 2025-10-29T01:20:30.401Z DEBU [PROXY:SER] Succeeded dialing cluster:main dial_params:from: "<user-ip>:49686" to: "<ssh-server-ip>:3022" reversetunnel/localsite.go:320

• Skipping connection to the local ssh-agent: This line indicates that Teleport is not using your local SSH agent, which is normal for web-based access.
• Initiating dial request...: This shows Teleport attempting to establish a connection to your SSH server.
• No proxy set in environment...: This means Teleport is not using a proxy to connect to the SSH server. This is often the expected behavior.
• Succeeded dialing...: This indicates that the initial connection was successful.

Other Relevant Log Files

• Teleport Proxy Logs: These logs can provide insights into connection attempts and errors related to the proxy service.
• SSH Server Logs: The SSH server's logs (usually in /var/log/auth.log or similar) can show SSH connection attempts, authentication failures, and any errors on the server side.
• Web Browser Developer Tools: Inspect the web browser's developer tools (Network tab) for any errors during file transfer attempts. This can show if the browser is experiencing any specific problems.

Potential Causes and Solutions

Many factors could be responsible for the