Syncthing Killing Phone Connection/Calls - Android 10

Here you go.

logcat2.txt (1.3 MB)

Running a 3XL tried the launch 10 build and the October security updates, works as expected. Definitely something relating to your phone.

@youngheart80 I’ve sat ~ 15 minutes over the log, but I’m clueless what caused the disconnect on your mobile adapter. Generally I’ve found:

  • The log is full of Errors and Debug lines (E/D)
  • It mentions “waste RAM, bad performance” on multiple lines - not sure if that is critical or just a “NOTE” as stated on that lines.
  • AppOps denies some permissions and affects Synchting’s BootReceiver. Anyways, technically the apps should still work okay when autostart is denied.
  • I’ve noticed a lot of apps present on your phone (tools, games, etc.) - can’t say if it is too much as your phone model looks pretty much like a flagship having enough system resources.

Eh, it was a longshot anyway. Thanks for looking. I know what I’ll be doing for at least part of this weekend.

Thanks again.

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All, didn’t realize there was a split-off communication I was having with @Catfriend1 regarding troubleshooting this issue where we talked about this, but wanted to post the results of my factory reset last weekend.

It did not fix the issue, unfortunately. Even on a fresh factory reset, the same signal drop was present.

As my SO has the same phone model and the same service with Visible Wireless, I thought I’d check to see if her’s would have the same result. Turns out, it does - same signal drop, same pattern as before.

So, this seems to be either some weird mix of Syncthing, Pixel 3, and Visible; or something that Visible is causing on their side of things that Syncthing somehow triggers.

As of now, my only way to really deal with it is to only run Syncthing when I have some specific reason and then kill the app after I’m done.

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@youngheart80 Can you try disabling Local Discovery in Settings - Syncthing Options? I also experience cell disconnects with the same carrier and similar phone (Pixel 3 XL):

Presumably the local announcement packet triggers the cell disconnect, either by the phone (OS or kernel bug?) or the carrier (Visible/Verizon). However, I was not able to trigger a disconnect when sending IPv4 broadcast and IPv6 multicast from Termux:

echo -n hello | socat - udp-datagram:<cellular link broadcast address>:21027,broadcast
echo -n hello | socat - udp-datagram:,broadcast
echo -n hello | socat - udp-datagram:[ff12::8384]:21027

@firecat4153 when Syncthing is active (satisfies run conditions) and local discovery is enabled, does your phone briefly downgrade from LTE to CDMA every minute or so? If so, Verizon has the same issue, but Visible only operates on LTE, so the phone won’t seamlessly downgrade to CDMA.


I’ll need to do a bit more playing once I get home to Wi-fi and have my other devices up, but yes, disabling Local Discovery does seem to solve the drop issue. I want to say I tried that setting on a previous build, but it caused the app to crash immediately. I’ll also admit I had given up hope of anything getting done and so have migrated away from using Syncthing, but if this gives a direction that might help fix things, I’ll be back in a heartbeat - Syncthing did exactly what I needed right up to the point where Android wasn’t working.

Let me do a bit more testing in a couple of hours once I’m away from work.

@dara, many thanks.

I have been working with it for the last hour, re-setting up my folder shares. Everything works perfectly. No signal drops, no issues. Disabling Local Discovery does seem to have addressed the situation.

It would be interesting to see if @firecat4153 or another Pixel 3/3XL user on Verizon can chime in to see about the drop from LTE to CDMA.

I’m not aware of any drops to CDMA from LTE (Verizon). I have Syncthing set to run always on Wifi. I’ll usually turn on a wireguard VPN when on an outside Wifi source, but not when I’m home. I believe my Pixel 3 is setup for Wifi calling, so I’m not sure if that changes anything. I did switch Syncthing today to run also when on mobile data and didn’t notice any service drops. I have local and global discovery enabled, but relaying disabled.

In all fairness, I’m only measuring service drops by looking at the notification bar display. If there’s a different/better way to check that, I’m happy to try.

@firecat4153 @dara

Could you please post which Android versions you are on, is it also 10 like @youngheart80 reported?

I’ve had a chat with him and we we are trying to narrow the issue down to a specific hardware and/or software constellation.

Android 10, stock Pixel 3, 5 Dec 2019 security patch.

Yes, Android 10 (QQ1A.191205.008, Dec 2019) on Pixel 3 XL both on stock OS and AOSP built from source

Is the only difference between your phones pixel 3 and pixel 3 xl?

@Catfriend1, yes I believe that’s the only difference. I am also on the same Android build (Q01A.191205.008).

Random musings: it’s not your cell ISP seeing “that weird IPv6 stuff” and disconnecting you as some sort of stupid “precaution”? Could you try with another SIM that’s on a different cell ISP to see if it still happens? v6 local disco shouldn’t be going outside of your local network and when on WiFi, there shouldn’t be any cell data, but this seems such a bizarre problem that it’s worth a try.

So my wild guess is the “Pixel 3 XL” got a poor driver or modem firmware with Google’s Android 10 update.

@dara @youngheart80 Could you please grab that info for me and post it?

adb shell
getprop | grep ro.product 

It would be a first step into the direction to workaround the issue.

I got a 3 XL but I am not on that network, and I see no issues.

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Oh that’s good news, thanks for testing it :-).