OpenVPN generates flood of CTL MAC Pause packets

[myce]

On a router using OpenVPN 2.1-RC3 the following happens:
Some time (minutes to an hour) after the OpenVPN daemon is started, the network does no longer react and all that is seen on eth0 is MAC Pause packets:
(Captured with Wireshark:)

0000   01 80 c2 00 00 01 01 80 c2 00 00 01 88 08 00 01  ................
0010   ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0020   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
0030   00 00 00 00 00 00 00 00 00 00 00 00              ............

Ethernet II, Src: Spanning-tree-(for-bridges)_01 (01:80:c2:00:00:01), Dst: Spanning-tree-(for-bridges)_01 (01:80:c2:00:00:01)
    Destination: Spanning-tree-(for-bridges)_01 (01:80:c2:00:00:01)
        Address: Spanning-tree-(for-bridges)_01 (01:80:c2:00:00:01)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
    Source: Spanning-tree-(for-bridges)_01 (01:80:c2:00:00:01)
        Address: Spanning-tree-(for-bridges)_01 (01:80:c2:00:00:01)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
    Type: MAC Control (0x8808)
MAC Control
    Pause: 0x0001
    Quanta: 65535

These packets are generated in an endless loop which can only be stopped by killing the OpenVPN daemon.

Besides just waiting for it to happen, I can provoke this by sending many packets to the router in quick succession. Which makes me think that the daemon detects some kind of overrun and requests a slowdown. The sensible thing to do, I'd say. The only problem is that it doesn't break out of this loop.
Maybe I should mention that during the tests no OpenVPN connection was active, i.e. the daemon was basically idle.

[David Sommerseth]

I doubt you've been using 2.1-RC3 ... as we've not really released 2.2-RC officially. Except of having a few Windows versions with 2.2-RC-preview, to see if our new building system have worked or not.

However, can you provide more config information? It would be good if it is possible to figure out the minimal OpenVPN configuration which causes this to happen. Then it's easier to see which code paths to look at in the source.

Also try this on a OpenVPN 2.1 release. This is to identify if it is a regression or an older bug.

[Samuli Seppänen]

No comments from the reporter, closing the bug.

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