Please provide the following information

qBittorrent version and Operating System

QB 4.3.1 4.3.2. and 4.3.3 on Win 10 x64

What is the problem

having some problems with QB 4.3.2 that I cannot pinpoint to anything

4.3.1 works flawless
upgrade to 4.3.2 -> some trackers "not working" but others do.

Those trackers that don't work have 4.3.2 whitelisted, but just to verify, I tried them on my laptop, and they work fine with 4.3.2, so the problem must be something on my desktop PC with 3.2 that 3.1 doesn't have

to make it work, I tried

1- Deleting everything and a fresh install of 4.3.2, then download a new torrent from those trackers on the new QB with default settings -> still not work on desktop, but it does on the laptop.
2- disabling the AV -> not work
3- disabling the firewall -> not work

What is the expected behavior

to work and connect

Want to back this issue? Post a bounty on it! We accept bounties via Bountysource .

it was disabled, but I tried checked in, force recheck torrent, force re-announce -> not working

uncheck it again, -> force recheck torrent, force re-announce -> still not working

can you share screenshot which tracker work and which not?

I doubt that would accomplish anything.

Does the tracker status column say anything under the Trackers tab?
Does the execution log provide any information?

Please try this build which has logging support for tracker error alerts.

It includes this commit 35d393d

link to github actions CI workflow

https://github.com/qbittorrent/qBittorrent/actions/runs/500610450#artifacts

Direct link for windows x64 build.

https://github.com/qbittorrent/qBittorrent/suites/1870692438/artifacts/36439917

Does the execution log provide any information?
Nothing useful I think, everything seems fine.

(N) 2021-01-21T18:46:15 - qBittorrent v4.3.3 started
(N) 2021-01-21T18:46:15 - Using config directory: C:/Users/xxxxxxxx/AppData/Roaming/qBittorrent/
(I) 2021-01-21T18:46:15 - Trying to listen on: 0.0.0.0:43315,[::]:43315
(N) 2021-01-21T18:46:15 - Peer ID: -qB4330-
(N) 2021-01-21T18:46:15 - HTTP User-Agent is 'qBittorrent/4.3.3'
(I) 2021-01-21T18:46:15 - DHT support [ON]
(I) 2021-01-21T18:46:15 - Local Peer Discovery support [ON]
(I) 2021-01-21T18:46:15 - PeX support [ON]
(I) 2021-01-21T18:46:15 - Anonymous mode [OFF]
(I) 2021-01-21T18:46:15 - Encryption support [ON]
(I) 2021-01-21T18:46:15 - UPnP / NAT-PMP support [ON]
(I) 2021-01-21T18:46:15 - IP geolocation database loaded. Type: DBIP-Country-Lite. Build time: Fri Jan 1 02:03:39 2021.
(N) 2021-01-21T18:46:15 - Options were saved successfully.
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 192.168.1.121, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 192.168.1.121, port: UDP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 192.168.166.1, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 192.168.166.1, port: UDP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 192.168.159.1, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 192.168.159.1, port: UDP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 127.0.0.1, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: 127.0.0.1, port: UDP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: fe55::xxxxxxxxxxxxxxxxx, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: fe55::xxxxxxxxxxxxxxxxx, port: UDP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: fe55::xxxxxxxxxxxxxxxxx, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: fe55::xxxxxxxxxxxxxxxxx, port: UDP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: fe55::xxxxxxxxxxxxxxxxx, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: fe55::xxxxxxxxxxxxxxxxx, port: UDP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: ::1, port: TCP/43315
(I) 2021-01-21T18:46:16 - Successfully listening on IP: ::1, port: UDP/43315
(N) 2021-01-21T18:46:16 - 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' restored.
(I) 2021-01-21T18:46:16 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: TCP/43315
(I) 2021-01-21T18:46:16 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: TCP/43315
(I) 2021-01-21T18:46:17 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/43315
(I) 2021-01-21T18:46:17 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/43315`

Please try this build which has logging support for tracker error alerts.

I've tried it, but unfortunately that version is identified as QB 4.4.X and the trackers have not it whitelisted so I get that generic error and not the reason of why 4.3.2. and 4.3.3 refuses to connect

https://i.imgur.com/r8ei2bw.png

The execution log shows
external port: UDP/43315
(N) 2021-01-21T18:57:06 - 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' restored.
(W) 2021-01-21T18:57:06 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-21T18:57:06 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-21T18:57:06 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-21T18:57:06 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(I) 2021-01-21T18:57:06 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/43315
(W) 2021-01-21T18:57:06 - Tracker error: A socket operation was attempted to an unreachable network | failure reason:
(W) 2021-01-21T18:57:06 - Tracker error: A socket operation was attempted to an unreachable network | failure reason:
(W) 2021-01-21T18:57:06 - Tracker error: A socket operation was attempted to an unreachable network | failure reason:
(W) 2021-01-21T18:57:06 - Tracker error: tracker sent a failure message | failure reason: Your client is not on the whitelist

I'm also seeing this, let me know if there's anything I can get from the device that would be useful.
I'm on QT4.3.3 on Windows 10.

The actions CI is using an older version of libtorrent (1.2.11) and won't give the equivalent result of 4.3.3.
@xavier2k6 can you please provide a test build with this patch 35d393d over 4.3.x branch and latest libtorrent RC_1_2?

Try this test build. It is v4.3.3 with the patch provided by @an0n666 for logging tracker errors. The rest of the libraries are the same as the ones I used for the official 4.3.3
Link: archive / pgp signature

@pacopepepipo
can you try enabling the Options->Advanced->Support internationalized domain name(IDN) option?

yes, still not working

Try this test build. It is v4.3.3 with the patch provided by @an0n666 for logging tracker errors. The rest of the libraries are the same as the ones I used for the official 4.3.3
Link: archive / pgp signature

Log with desktop who doesn't work

(N) 2021-01-22T18:53:04 - qBittorrent v4.3.3 started
(N) 2021-01-22T18:53:04 - Using config directory: C:/Users/xxxxxxxxxxx/AppData/Roaming/qBittorrent/
(I) 2021-01-22T18:53:06 - Trying to listen on: 0.0.0.0:24281,[::]:24281
(N) 2021-01-22T18:53:06 - Peer ID: -qB4330-
(N) 2021-01-22T18:53:06 - HTTP User-Agent is 'qBittorrent/4.3.3'
(I) 2021-01-22T18:53:06 - DHT support [ON]
(I) 2021-01-22T18:53:06 - Local Peer Discovery support [ON]
(I) 2021-01-22T18:53:06 - PeX support [ON]
(I) 2021-01-22T18:53:06 - Anonymous mode [OFF]
(I) 2021-01-22T18:53:06 - Encryption support [ON]
(I) 2021-01-22T18:53:06 - UPnP / NAT-PMP support [ON]
(W) 2021-01-22T18:53:06 - Couldn't load IP geolocation database. Reason: The system cannot find the path specified.
(N) 2021-01-22T18:53:07 - Options were saved successfully.
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 192.168.1.121, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 192.168.1.121, port: UDP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 192.168.166.1, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 192.168.166.1, port: UDP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 192.168.159.1, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 192.168.159.1, port: UDP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 127.0.0.1, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: 127.0.0.1, port: UDP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxxxxxxxx, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxxxxxxxx, port: UDP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxxxxxxxx, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxxxxxxxx, port: UDP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxxxxxxxx, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxxxxxxxx, port: UDP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: ::1, port: TCP/24281
(I) 2021-01-22T18:53:07 - Successfully listening on IP: ::1, port: UDP/24281
(I) 2021-01-22T18:53:07 - IP geolocation database loaded. Type: DBIP-Country-Lite. Build time: Fri Jan 1 02:03:39 2021.
(I) 2021-01-22T18:53:07 - Successfully updated IP geolocation database.
(I) 2021-01-22T18:53:09 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: TCP/24281
(I) 2021-01-22T18:53:09 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/24281
(I) 2021-01-22T18:53:09 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: TCP/24281
(I) 2021-01-22T18:53:09 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/24281
(N) 2021-01-22T18:54:04 - 'xxxxxxxxxxxxxxxxxxxxxx' added to download list.
(W) 2021-01-22T18:54:05 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-22T18:54:05 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-22T18:54:05 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-22T18:54:05 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-22T18:54:05 - Tracker error: banned by IP filter | failure reason:
(W) 2021-01-22T18:54:05 - Tracker error: banned by IP filter | failure reason:
(W) 2021-01-22T18:54:05 - Tracker error: banned by IP filter | failure reason:
(W) 2021-01-22T18:54:05 - Tracker error: banned by IP filter | failure reason:
(W) 2021-01-22T18:54:22 - Tracker error: banned by IP filter | failure reason:
(W) 2021-01-22T18:54:22 - Tracker error: banned by IP filter | failure reason:
(W) 2021-01-22T18:54:22 - Tracker error: banned by IP filter | failure reason:
(W) 2021-01-22T18:54:22 - Tracker error: banned by IP filter | failure reason:
(I) 2021-01-22T18:54:42 - UPnP / NAT-PMP support [OFF]

Log with laptop who managed to download it and connect

(N) 2021-01-22T19:03:33 - qBittorrent v4.3.3 started
(N) 2021-01-22T19:03:33 - Using config directory: C:/Users/xxxxxxxxxxxx/AppData/Roaming/qBittorrent/
(I) 2021-01-22T19:03:34 - Trying to listen on: 0.0.0.0:13802,[::]:13802
(N) 2021-01-22T19:03:34 - Peer ID: -qB4330-
(N) 2021-01-22T19:03:34 - HTTP User-Agent is 'qBittorrent/4.3.3'
(I) 2021-01-22T19:03:34 - DHT support [ON]
(I) 2021-01-22T19:03:34 - Local Peer Discovery support [ON]
(I) 2021-01-22T19:03:34 - PeX support [ON]
(I) 2021-01-22T19:03:34 - Anonymous mode [OFF]
(I) 2021-01-22T19:03:34 - Encryption support [ON]
(I) 2021-01-22T19:03:34 - UPnP / NAT-PMP support [ON]
(W) 2021-01-22T19:03:34 - Couldn't load IP geolocation database. Reason: The system cannot find the path specified.
(N) 2021-01-22T19:03:34 - Options were saved successfully.
(I) 2021-01-22T19:03:34 - Successfully listening on IP: 192.168.1.77, port: TCP/13802
(I) 2021-01-22T19:03:34 - Successfully listening on IP: 192.168.1.77, port: UDP/13802
(I) 2021-01-22T19:03:34 - Successfully listening on IP: 127.0.0.1, port: TCP/13802
(I) 2021-01-22T19:03:34 - Successfully listening on IP: 127.0.0.1, port: UDP/13802
(I) 2021-01-22T19:03:34 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxx, port: TCP/13802
(I) 2021-01-22T19:03:34 - Successfully listening on IP: fe80::xxxxxxxxxxxxxxxx, port: UDP/13802
(I) 2021-01-22T19:03:34 - Successfully listening on IP: ::1, port: TCP/13802
(I) 2021-01-22T19:03:34 - Successfully listening on IP: ::1, port: UDP/13802
(I) 2021-01-22T19:03:34 - Detected external IP: 188.78.4.90
(I) 2021-01-22T19:03:35 - IP geolocation database loaded. Type: DBIP-Country-Lite. Build time: Fri Jan 1 02:03:39 2021.
(I) 2021-01-22T19:03:35 - Successfully updated IP geolocation database.
(I) 2021-01-22T19:03:35 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: TCP/13802
(I) 2021-01-22T19:03:35 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/13802
(I) 2021-01-22T19:03:35 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: TCP/13802
(I) 2021-01-22T19:03:36 - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/13802
(N) 2021-01-22T19:03:53 - 'xxxxxxxxxxxxxxxxxxxxxxxx' added to download list.
(W) 2021-01-22T19:03:55 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-22T19:03:55 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(W) 2021-01-22T19:03:55 - Tracker error: skipping tracker announce (unreachable) | failure reason:
(I) 2021-01-22T19:04:16 - UPnP / NAT-PMP support [OFF]

Do you have any IP addresses in the banned IP list/IP filter? The tracker alert suggests that the tracker’s IP is banned. So please check that list and see if removing everything/specific IP from that list works.

I don't, every log I pasted was made on fresh installs, there is no other configuration that it's not the default or the suggestions about IDN / https that I tried.

Even more, this is after a fresh windows 10 install with the firewall off and after a router reset (not reboot, complete reset of settings to factory)

I agree that it is weird to see the banned IP filter message, but why that message appears with 4.3.3/2 and everything works flawless on 4.3.1?

I am at a loss here, I can provide as many info as you want, because I don't have the slightest clue of where the error could come from

Hello

I've managed to pinpoint why it doesn't work, but I don't know if there is something that can be made to solve it (besides the manual option)

I use proxycap , a program which I use to redirect the traffic from 2 specific apps, firefox and brave through 2 different SSH tunnels to 2 VPS on other countries to bypass some regional restrictions of services I use. I use proxycap because it let me open those tunnels for individual .exes instead of the whole system and pretty easily and seamless. I don't use QB with tunnels nor anything related with that program at all

With 4.3.1 everything works fine, but with 4.3.2 or more, It won't work or connect to those trackers (and even weirder because it is some trackers not everyone as some of them connect) unless I deactivate proxycap before launch.

so it ends like this
4.3.1 = everything fine

4.3.2 or more
proxycap on:
launch QB won't connect to trackers and will not do it either if you deactivate proxycap after launching and try to add some new torrents or refresh others.

proxycap off:
launch QB and everything will work.

Why both programs fight between themselves and what changed from 4.3.1 to 4.3.2 to do it, I don't know but at least now I have a temporal solution.

@pacopepepipo can you go to advnaced settings and choose a specific network interface (aka your regular one since you don't use vpn/proxy/tunnels with qbittorrent). Does that work now?

I just tried, I picked up the only one that connects through internet (proxycap doesn't create new network interfaces but I have extra from VMware), and still refuses to connect.

Then I tried every other combination, disabling every virtual network interface and having the only physical one connected, selected and didn't work, after I've tried optional ip address binding and the previous suggestions with IDN

no matter what I do, 4.3.2 and 4.3.3 just don't connect if I don't disable proxycap before opening QB, and 4.3.1 connects with any combination and without disabling pcap

edit: If I close every app that was using some tunneling through pcap, 4.3.2 and 4.3.3 boot and connect to the trackers without disabling it first. I suppose that as no tunnel is open, at the end it is the same as disabling pcap as nothing on the background is running.

So the question would be, what could have changed since 4.3.1 that fights with pcap under windows while using ssh tunneling. And then, why only some trackers are affected. This is just bonkers.

The following build uses the same libtorrent version as in v4.3.1
Link: archive / pgp signature

r what I do, 3.2 and 3.3 just don't co

Please refer to the versions with their full name, because it creates ambiguities with older qbt versions when read.

The following build uses the same libtorrent version as in v4.3.1
Link: archive / pgp signature

That version works flawless as 4.3.1

Should I move to libtorrent github then and open the issue there? If that's the case, what version of libtorrent use 4.3.1 and 4.3.2/3 to give them as much info as I can?

Please refer to the versions with their full name, because it creates ambiguities with older qbt versions when read.

Done, I've edited all my post

Test build v5
Link: archive / pgp signature

PS: I probably won't be able to do a new test build for a few hours

Seems like there will be no need, this build worked!

I don't think that'll be needed. When SSRF mitigation blocks a tracker it generates the same IP filter message.
https://github.com/arvidn/libtorrent/pull/5346/files
This mitigation was added recently.
@arvidn any idea what's going on here?

@pacopepepipo you say it doesn't connect to "trackers", as if it affects all trackers. Is that true? ot does it affect some trackers?

can you describe these properties of the tracker that's failing?

I don't really know any details about proxycap specifically (and it doesn't seem to be open source). But it's possible to installer a layered service provider (LSP) on windows that can basically do anything. They even run in the same process that's accessing the network (at least they used to, back in the windows vista era).

(as an anecdote, back in 2008 one third of all uTorrent crashes were caused by a bug in nVidia's software firewall, which was an LSP ending up executing inside the uTorrent process corrupting the stack sometimes)

@arvidn OK, I understand

@sledgehammer999 would it make sense to loosen the requirement to accept trackers that both start with and end with "/announce"?

I have no comment for this. I don't have experience or insight on networking security so I will leave it to you on how to deal with it.

I have no comment for this. I don't have experience or insight on networking security so I will leave it to you on how to deal with it.

Having said that, please consider adding a specific error when a tracker is dropped due to ssrf mitigation. It will help diagnosing future problems.

Having said that, please consider adding a specific error when a tracker is dropped due to ssrf mitigation. It will help diagnosing future problems.

arvidn/libtorrent#5903 😉

@sledgehammer999
Even if specific messages are added,
qBt won’t display the error codes from tracker alerts. It only displays the error messages sent from tracker.
PRs like these would’ve made it easier to diagnose tracker issues as you get to see error codes and messages per endpoint.
#13266

@arvidn
There are many private trackers which include the passkey after / and end with /announce.

looking a bit, every cabal tracker have that kind of announce url, don't know the reason though

it really comes down to; when someone deliberately runs a tracker on loopback, what are reasonable to require that tracker do or look like to ensure it actually is a bittorrent tracker. private trackers on the interent shouldn't be running on loopback, so I don't actually think that's a useful metric. What the default configurations are for trackers that are likely to be run in tests probably is.

i am having the same problem.

all private tracker shown Not Contacted Yet, i had tried setting announce to all tier, IDN, network interface, clean install...
back to previous version with same config working well.

my last known working build was 2 weeks ago, having these commit:

qbittorrent commit
d1aba56

libtorrent commit
arvidn/libtorrent@ c13ae5d

these two was the last know working commit, since i compile it once a week, i am not sure which commit start causing this problem.

Hello

sorry to crash this as I don't know if this issue still open, but I had the same problem. I've updated from 4.0 to 4.3.3 this week and went crazy looking why the trackers didn't work, finally found this after some obscure google indexing bring me here.

After reading the thread, it's exactly my problem when I try to redirect some programs from windows. For example trying to play an mmo on another region locked server but redirecting that only game and not the whole system and the new qbitt/libtorrent just refuses to work.

What I don't see on this thread is if @arvidn is going to add the mitigation that you were talking about few weeks ago, or if this is going to be a thing forever. All the top tier trackers, like ptp, redacted, etc, use the /announce style url so not a single one of them works with the new version, just the crappy ones or public, but not a single cabal. And I am using different software than the OP, so it seems like it's a more common problem than just changing one from another, seems like all of them use the same kind of networking under windows to do this things.

any new info?

@LuigiPlumber If you run HTTP tracker traffic via proxy on your local host (over loopback) you should disable the SSRF mitigation. This is such a new option that it's possible qBT has not exposed it in the UI yet. (maybe someone could contribute a uTorrent-style advanced option that exposes every setting as a list).

You don't mention running a proxy though, but I think that's what this thread is about.

yes, I'm saying using a program to redirect other programs through a proxy or ssh, like proxycap, proxyfier, supersocks5cap, etc that made qbt to not working with some /announce trackers because how windows manages to do it, exactly like the problem from OP, but with other different software to do it than proxycap involved

So, if I understand it, you added an option to disable it on the actual libtorrent and when or if QBT add that option in the ui, will work everything again like the old versions?

If that's correct, great to hear, thanks a lot for your work

So, if I understand it, you added an option to disable it on the actual libtorrent and when or if QBT add that option in the ui, will work everything again like the old versions?

That's correct. I'm guilty of adding the feature and defaulting it to on (and I think it made sense to do so)

just read the mail notifications, that's so great, hope we can configure it on QBT in the near future.

thanks @arvidn

Ok so I just tested to expose the option in the GUI and it works as expected

Note : I haven't implemented any translations.

Ok so I just tested to expose the option in the GUI and it works as expected

Note : I haven't implemented any translations.

This sounds like a bug since SSRF mitigation would only trigger for trackers that resolve to loopback?

I didn't specify it, but I use an HTTP proxy and it works as expected.

Regarding my PR, I don't know if it really solves THIS problem (mine was similar).
But at least one can choose to enable or disable mitigation now.

This sounds like a bug since SSRF mitigation would only trigger for trackers that resolve to loopback?

Tracker URLs that have any query string arguments are rejected when SSRF mitigation is enabled. Otherwise the restrictions of the path being /announce only applies if the IP resolves to a loopback address.

so, does the tracker hostname resolve to a loopback IP? Does it have a ? in it?

This sounds like a bug since SSRF mitigation would only trigger for trackers that resolve to loopback?

Tracker URLs that have any query string arguments are rejected when SSRF mitigation is enabled. Otherwise the restrictions of the path being /announce only applies if the IP resolves to a loopback address.

so, does the tracker hostname resolve to a loopback IP? Does it have a ? in it?

Yes, the tracker hostname was resolved on localhost.
Everything worked as expected, but it was a problem for me, that's why I exposed the ssrf_mitigation option in qBittorrent.
(The PR has been merged yesterday #15247 )

Similarly, enabling network sharing from one interface to another can also trigger this problem. All trackers say 'skipping tracker announce (unreachable)'. When it is disabled, trackers go back to normal.
qB v4.4.1 on Windows 10

In case anyone is having any trouble I got this solved although I've gone through the whole comments without any success.

I just opened hosts file and deleted lines of codes which was pertained to the torrent site I was dealing with.

C:\Windows\System32\drivers\etc there you'll find hosts file, just make sure you run notepad as admin and open the file, if it get back those lines just make the host file read only.