Experiencing intermittent problems with your proxy server, specifically a SOCKS4 proxy, can be incredibly frustrating, especially when troubleshooting efforts seem to be continuously undermined by the unpredictable nature of the issue. Like many, I initially thought I had found a solution, only to have the problem resurface, highlighting the complexities of network debugging.
The previously suggested solution, and one that initially appeared to resolve the issue, was not a permanent fix for me. For a while, it seemed effective, but the problems soon returned. Restarting my SSH session sometimes temporarily alleviated the issue, only for it to reappear, and at other times, restarting made no difference whatsoever.
Another suggestion involved specifying 127.0.0.1 instead of "localhost" in the browser’s proxy settings. This too, seemed promising initially and I even prematurely attributed it as the critical factor in restoring browser connections through the tunnel. However, this proved to be another false dawn as the intermittent connection problems when browsing websites via the tunnel persisted.
After extensive troubleshooting and continued experience with this issue, I’ve become reasonably convinced that the root cause lies in a short-timeout bug within OpenSSH itself. My conclusion is based on two key observations. Firstly, the problem is demonstrably browser-independent, having been verified across Firefox, Chromium, and w3m. Secondly, and more decisively, switching to an alternative SSH client has consistently resolved the problem for me.
To test this hypothesis, I downloaded, built, and installed PuTTY (available from this link). For those attempting this, note that you may need to install the gtkgl-dev virtual package to ensure PuTTY’s source code can locate the necessary header files. After configuring PuTTY similarly to my past setups on Windows, it has operated flawlessly for approximately two days, with zero connection failures.
This experience leads me to believe that using PuTTY is indeed the solution and strongly suggests the presence of a bug in the current OpenSSH version I was using:
OpenSSH_7.2p2 Ubuntu-4ubuntu1, OpenSSL 1.0.2g-fips 1 Mar 2016
While further investigation and formal bug reporting to the OpenSSH project are warranted, for anyone facing similar intermittent SOCKS4 proxy issues when using OpenSSH for tunneling, switching to PuTTY may offer a stable and immediate workaround. This has proven to be a reliable fix in my case, eliminating the frustrating inconsistencies I was previously encountering.
