Bad record MAC & record overflow

Hey there

I use Syncthing to share my media between 2 computers over wifi (local). The Folder is about 600GB and 120000 files.

It’s syncing but every minute oder two i got “connection closed: local error: bad record MAC”. The last days it was “local error: record overflow”.

After that it’s establishing a new connection and syncing works for 1 or 2 min.

Any help out there?

It seems you have some sort of network monitoring applications installed which modify/try to inject packets into the encrypted stream, causing it to break.

oh, i can’t even guess what this would be.

Do you have any examples?

I’m on a standard arch linux machine with xfce (both). I am not aware of running any network monitoring tools.

Edit: since i use Syncthing (2 weeks) i got 3 complete system freezes. Before never did anything freeze. Could this be related to the problem above?

I can’t say, it could be due to you upgrading some package in the OS or faulty hardware. An unprivileged piece of software should never be able to crash hardware or the OS.

Yeah. Memory corruption, perhaps.

something new happend:

While i was updateing google chrome, this error occured:

curl: (56) SSL read: error:1408F119:SSL routines:SSL3_GET_RECORD:decryption failed or bad record mac, errno 0

Is this still syncthing-related? any ideas? I shut down nearly all running services and processes but record overflow and bad record MAC still appears.

syncthing also gives me sometimes the info, that UPnP has some issues:

WARNING: Failed to set UPnP port mapping: external port 0 on device 'FRITZ!Box 6340 Cable (kbw)' (

No, its not related to syncthing, and not caused by syncthing. The fact that that is happening is the crux of the problem, as it also seems to be happening to other software on your machine. As I said, it’s either malware on your machine, or bad hardware.

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