Non-image media does not load and times out under certain conditions

[composite9239]

Description

When using Element X iOS, there is a set of specific conditions under which media will not load and will time out after 30 seconds. I was informed that it was indicated via the following Element X logs that it does not appear to be an issue with the app:

matrix_sdk::http_client: Error while sending request: Reqwest(reqwest::Error { kind: Body, source: TimedOut }) | crates/matrix-sdk/src/http_client/mod.rs:234 | spans: send{server_versions=[V1_0, V1_1, V1_2, V1_3, V1_4, V1_5, V1_6, V1_7, V1_8, V1_9, V1_10, V1_11] config=RequestConfig { timeout: 30s, retry_limit: 0 } request_id="REQ-40" method=GET uri="https://homeserver.address/_matrix/client/v1/media/thumbnail/homeserver.address/smfWrihLzCeGAyhtHkGKTTKD"} 2024-12-07T08:29:13.455924Z ERROR elementx: Failed retrieving image with error: Generic(msg: "request or response body error") | MediaProvider.swift:64 | spans: root

Steps to reproduce

The steps are somewhat complicated. However, I asked another Element X iOS user to reproduce it for me and they encountered the same issue, so a tester from the dev team probably could as well. It requires a Mullvad VPN account.

• On Mullvad VPN iOS, go to VPN settings and 1) enable multi-hop, 2) set wireguard obfuscation to UDP-over-TCP, and 3) set quantum-resistant tunnel to on
• set the entry server to a certain Houston US server, us-hou-wg-001 (the specific server apparently matters, at least for the exit, but might as well choose the same one we did for the entry as well)
• set the exit server specifically to this Netherlands server: nl-ams-wg-001 (the issue also happens for 002, 003, and 004)
• send yourself a new audio or video file in a private channel (happens in both encrypted or unencrypted) (must be a new file not previously loaded and cached)
• will get loading icon for 30 seconds and then timeout

Images appear to load normally.

Homeserver

Another homeserver

Synapse Version

1.120.2

Installation Method

Other (please mention below)

Database

PostgreSQL

Workers

Multiple workers

Platform

Ubuntu 22.04, no VM

Configuration

Standard specialized-workers preset for matrix-docker-ansible-deploy

Relevant log output

Unsure of relevant portion

Anything else that would be useful to know?

• Authenticated media enabled
• Native sliding sync
• On such VPN servers, the connection is generally fast and all other server functionality works normally, including loading images. This specifically happens for files like mp3 or webm
• The files attempting to be loaded are small (as little as under 1MB)
• I have not confirmed that such complex VPN configuration is necessary to reproduce the bug, so it might happen for a broader scope of users than the criteria would indicate; I have unintentionally replicated the bug multiple times in the past on different Mullvad servers but did not report it those times
• Can download all media properly with such VPN configuration on Element iOS; does Element X have some specific interaction with the server? If not, would this question be better-suited for Element X devs after all?