qBittorrent-nox v4.2.5 does not detect bad torrent files or advise user torrent file is invalid.

[sunrisepi]

Please provide the following information

qBittorrent version and Operating System

qBittorrent-nox v4.2.5, raspbian (buster)

If on linux, libtorrent-rasterbar and Qt version

• libtorrent-1_2_6
• Qt believed to be version 5.11.3 (per qtdiag). Ran at prompt:
  /usr/lib/qt5/bin/qmake -v
  QMake version 3.1
  Using Qt version 5.11.3 in /usr/lib/arm-linux-gnueabihf

What is the problem

Noticing an issue with qBittorrent-nox v4.2.5 in raspbian (buster build).
It does not detect invalid/corrupt torrent files. Please advise?

What is the expected behavior

qBittorrent-nox v4.2.5 should detect bad torrent file and advise user

Steps to reproduce

• Compiled/installed qBittorrent-nox v4.2.5 using this guide: https://github.com/qbittorrent/qBittorrent/wiki/Compiling-qBittorrent-nox-4.x-on-DietPi-or-Raspbian-(Debian-9.0)-for-ARM-devices
• Run qBittorent-nox &
• Login to WebUI on port 8080, using login/password
• Install search engines (click Search Tab on right of UI, click "Search plugins.." at bottom right, click "Check for Updates" then close). This activates the default search plugins (like 1337x.to, limetor.com, etc.)
• Searched for "windsor castle" using built-in search and found a torrent to download. Right-click, download. Download dialog box pops up, URL provided: "https://limetor.com/BBC-The-Queens-Palaces-2of3-Windsor-Castle-x264-AAC-HDTV--torrent-866639.html". Click Download. Dialog box goes away.
• Saw the following logged to ~/local/share/data/qBittorrent/logs/qbittorrent.log:
  "(N) 2020-04-25T14:38:49 - Downloading 'https://limetor.com/BBC-The-Queens-Palaces-2of3-Windsor-Castle-x264-AAC-HDTV--torrent-866639.html', please wait..."
• Check Transfers tab.. do not see the torrent downloading. It was apparently not added to download list.
• No error or other explanation is provided by qBittorrent-nox. At this point, no idea why torrent is not showing up in download list.

After some more research, it seems qBittorrent-nox does not report that the torrent file is invalid. I figured this out after comparing to 2 other bittorrent clients.

Now if I try qBittorrent v4.2.2 in Windows, it detects the bad torrent file:

• Try adding link (File->Add Torrent Link, paste in https://limetor.com/BBC-The-Queens-Palaces-2of3-Windsor-Castle-x264-AAC-HDTV--torrent-866639.html and click Download)
• Error message pops up, "Invalid torrent. Failed to load from URL:https://limetor.com/BBC-The-Queens-Palaces-2of3-Windsor-Castle-x264-AAC-HDTV-torrent-866639.html. Error: expected value (list, dict, int or string) in bencoded string"

Now checking transmission v2.9.2 (14714) in raspbian (buster/Linux), it also detects the bad torrent file:

• Try adding link (click folder icon, paste in https://limetor.com/BBC-The-Queens-Palaces-2of3-Windsor-Castle-x264-AAC-HDTV--torrent-866639.html and click "Upload" a torrent file to add torrent for downloading)
• Error message pops up, "Error adding 'https://limetor.com/BBC-The-Queens-Palaces-2of3-Windsor-Castle-x264-AAC-HDTV--torrent-866639.html': invalid or corrupt torrent file"

Extra info(if any)

It's a bit disappointing to see qBittorrent-nox not working as expected, after all the effort to compile and install it. Is this a known issue with not detecting bad torrent files? How do we fix this? Thanks.

[FranciscoPombal]

I managed to reproduce this on 4.2.5.
Looks like a bug both in the plugin and in qBittorrent.

On the plugin side, the Download link and description page URLs both point to the description page. This is wrong, at least for this plugin.

On the qBittorrent side, when using the GUI, qBittorrent manages to get the magnet link correctly (somehow), while it silently fails to do so with the WebUI.

Even after the plugin is fixed, this silent failure should also be fixed.

@Piccirello @glassez

[Piccirello]

The web UI/API's silent failure bubbles back up to #10960. We just don't have good, standardized error handling for our API endpoints.

[sunrisepi]

Thanks for the info. When a version update/bugfix is released, I'll see if that fixes the issue. In the meantime, I'll be more watchful of the torrents I add, since qBittorrent itself cannot advise me if the torrent is invalid.

[FranciscoPombal]

I'll be more watchful of the torrents I add, since qBittorrent itself cannot advise me if the torrent is invalid.

It can, except on the WebUI/API where there is some kind of bug.

[sunrisepi]

Thanks. Unfortunately I am using qBittorrent via WebUI on my raspberry pi (which is running headless), so I'm not sure how to avoid the issue until the bug is fixed. ☺️

[Piccirello]

On the qBittorrent side, when using the GUI, qBittorrent manages to get the magnet link correctly (somehow), while it silently fails to do so with the WebUI.

@FranciscoPombal I've been trying to look into this issue. Did the GUI in fact get the correct magnet link, or did it just throw an error because the link was invalid? The GUI and Web UI now seem to use identical logic (AFAICT) for downloading links.

[FranciscoPombal]

@Piccirello The GUI somehow gets the correct magnet. Could it be that the GUI and WebAPI use different parts of the plugin API for this action?

[FranciscoPombal]

@Piccirello #12532 (comment)

[Anteus]

This is how the WebUI /torrent/add work:

qBittorrent/src/webui/api/torrentscontroller.cpp

Line 668 in fda6def

partialSuccess |= BitTorrent::Session::instance()->addTorrent(url, addTorrentParams);

And this is how it works in the normal UI:

qBittorrent/src/gui/search/searchjobwidget.cpp

Line 286 in fda6def

SearchDownloadHandler *downloadHandler = m_searchHandler->manager()->downloadTorrent(siteUrl, torrentUrl);

Could maybe add something like this to the TorrentsController::addAction?

        SearchDownloadHandler *downloadHandler = m_searchHandler->manager()->downloadTorrent(siteUrl, torrentUrl);
        connect(downloadHandler, &SearchDownloadHandler::downloadFinished, this, &SearchJobWidget::addTorrentToSession);
        connect(downloadHandler, &SearchDownloadHandler::downloadFinished, downloadHandler, &SearchDownloadHandler::deleteLater);

In the UI you also just get the description page link if you right click on a search result and copy download link.

Some linked issues
#11150
qbittorrent/search-plugins#160