Network manager PPTP VPN connection very unstable, connection breaks (lost packets)

[Kristof S.]

The PPTP-VPN connection over WiFi of my Ubuntu Xenial installation is extremely unstable, repeated loss of connection (100% packet loss), easily reproducible using network manager. The wlan module is r8712u (Realtek Semiconductor Corp. RTL8191SU 802.11n WLAN Adapter). (System: Linux Mint 18.3 Sylvia, xenial, linux 4.13.0-38-generic #43~16.04.1-Ubuntu SMP, x86_64)

Wlan connection seems quite stable basically but as soon as I start using vpn it quickly is broken after a very short time. Example pptp vpn is ca.hide.me but I tested other connections as well with the same result.

Network manager does not show a no-more-working connection visually (regarding the symbols all looks good) but it is quickly noticeable that no more internet sites are reacting as soon as the bug situation occurs (which is very often, normally only after a few seconds!).

The vpn sites are working good with other clients, also the wlan (WPA2) and wlan router itself at my home are working fine, several other client system (Windows, Mobile, another Linux) are working without any issue, thus it is definitely this specific network manager wlan/pptp-vpn client with the r8712u module causing the trouble.

### here I try to demonstrate a typical situation, first stable later the error

I start with resetting wlan module r8712u first, letting network manager establish a new connection to my wireless lan at 20:50-20:51h. Connection is working fine so far. (Module output: insmod /lib/modules/4.13.0-38-generic/kernel/drivers/staging/rtl8712/r8712u.ko)

Making a lot of traffic, parallel download etc. stress test, everything is stable so it does not seem that the wireless lan has issues but only the vpn client on top of it...

After disconnecting the broken vpn, the normal wlan traffic (internet sites etc.) are working again.

But to show the case here I demonstrate first the working base scenario and then the occuring bug situation.

First working situation before the bug occurs (starting with wlan reset first):
$ dmesg |tail -n20
[ 4869.764646] usbcore: deregistering interface driver r8712u
[ 4870.152409] usb 3-2: reset high-speed USB device number 2 using ehci-pci
[ 4871.333150] r8712u: module is from the staging directory, the quality is unknown, you have been warned.
[ 4871.334319] r8712u: register rtl8712_netdev_ops to netdev_ops
[ 4871.334324] usb 3-2: r8712u: USB_SPEED_HIGH with 4 endpoints
[ 4871.334830] usb 3-2: r8712u: Boot from EFUSE: Autoload OK
[ 4871.873153] usb 3-2: r8712u: CustomerID = 0x0000
[ 4871.873158] usb 3-2: r8712u: MAC Address from efuse = 00:0d:81:af:00:fb
[ 4871.873161] usb 3-2: r8712u: Loading firmware from "rtlwifi/rtl8712u.bin"
[ 4871.873713] usbcore: registered new interface driver r8712u
[ 4871.877915] r8712u 3-2:1.0 wlx000d81af00fb: renamed from wlan0
[ 4871.907478] IPv6: ADDRCONF(NETDEV_UP): wlx000d81af00fb: link is not ready
[ 4872.652953] r8712u 3-2:1.0 wlx000d81af00fb: 1 RCR=0x153f00e
[ 4872.653709] r8712u 3-2:1.0 wlx000d81af00fb: 2 RCR=0x553f00e
[ 4874.164838] IPv6: ADDRCONF(NETDEV_UP): wlx000d81af00fb: link is not ready
[ 4874.206830] IPv6: ADDRCONF(NETDEV_UP): wlx000d81af00fb: link is not ready
[ 4887.083087] IPv6: ADDRCONF(NETDEV_UP): enp3s0: link is not ready
[ 4887.088383] IPv6: ADDRCONF(NETDEV_UP): wlx000d81af00fb: link is not ready
[ 4887.121475] IPv6: ADDRCONF(NETDEV_UP): wlx000d81af00fb: link is not ready
[ 4895.089398] IPv6: ADDRCONF(NETDEV_CHANGE): wlx000d81af00fb: link becomes ready

$ nmcli d
DEVICE TYPE STATE CONNECTION
wlx000d81af00fb wifi connected Automatisch BM12E3
enp3s0 ethernet unavailable --
lo loopback unmanaged --

$ nmcli c
NAME UUID TYPE DEVICE
Automatisch BM12E3 e49fbaa5-14d9-400e-8c04-14602717479c 802-11-wireless wlx000d81af00fb
Wired connection 1 c235039e-b313-3c6b-9701-e4ad24cac272 802-3-ethernet --
ca.hide.me b0c7374c-e6ba-4752-bd67-8751dc389126 vpn --

# debug mode has been set now for better logging
$ sudo nmcli general logging level debug

### Then 21:13h now after making test connection to ca.hide.me and making some traffic, after a short time the bug situation occurs... vpn still seems to be connected but is completely broken.

# ok, no more internet sites responding and package loss at 100%

$ PING google.de (172.217.19.67) 56(84) bytes of data.

--- google.de ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2034ms

---

syslog continues error spam messages like that:

Apr 11 21:13:08 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:10 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:10 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:10 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:10 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:11 bluefx NetworkManager[8698]: <debug> [1523473991.4877] QL: qual 95/95/0x5F, level 100/100/0x64, noise 0/0/0x0, updated: 0x7 ** MAX: qual 100/100/0x64, level 100/100/0x64, noise 100/100/0x64, updated: 0x7
Apr 11 21:13:11 bluefx NetworkManager[8698]: <debug> [1523473991.4878] QL2: level_percent is 100. max_level 100, level 100.
Apr 11 21:13:11 bluefx NetworkManager[8698]: <debug> [1523473991.4878] QL: Final quality percent is 95 (95).
Apr 11 21:13:14 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:14 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:14 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:14 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:14 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:14 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:15 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:15 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:15 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:15 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:15 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:15 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:17 bluefx NetworkManager[8698]: <debug> [1523473997.4869] QL: qual 94/94/0x5E, level 100/100/0x64, noise 0/0/0x0, updated: 0x7 ** MAX: qual 100/100/0x64, level 100/100/0x64, noise 100/100/0x64, updated: 0x7
Apr 11 21:13:17 bluefx NetworkManager[8698]: <debug> [1523473997.4870] QL2: level_percent is 100. max_level 100, level 100.
Apr 11 21:13:17 bluefx NetworkManager[8698]: <debug> [1523473997.4870] QL: Final quality percent is 94 (94).
Apr 11 21:13:18 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:18 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:18 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:18 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:20 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:20 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:20 bluefx pppd[12334]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)
Apr 11 21:13:20 bluefx NetworkManager[8698]: Protocol-Reject for unsupported protocol 'Compressed Datagram' (0xfd)

---

(attached)
$ journalctl --no-pager > system-log_with_bugged_vpn

---

$ nmcli d
DEVICE TYPE STATE CONNECTION
wlx000d81af00fb wifi connected Automatisch BM12E3
enp3s0 ethernet unavailable --
lo loopback unmanaged --
ppp0 ppp unmanaged --

$ nmcli c
NAME UUID TYPE DEVICE
Automatisch BM12E3 e49fbaa5-14d9-400e-8c04-14602717479c 802-11-wireless wlx000d81af00fb
ca.hide.me b0c7374c-e6ba-4752-bd67-8751dc389126 vpn wlx000d81af00fb
Wired connection 1 c235039e-b313-3c6b-9701-e4ad24cac272 802-3-ethernet --

---

Network manager packages:

Network Manager: network-manager 1.2.6-0ubuntu0.16.04.2 amd64 network management framework (daemon and userspace tools)

network-manager-gnome 1.2.6-0ubuntu0.16.04.4 amd64 network management framework (GNOME frontend)

(PPTP plugin core)
ii network-manager-pptp-gnome 1.1.93-1ubuntu1 amd64 network management framework

[Kristof S. (ksa1)]

VPN config is as follows:

MSCHAPv2

Use Point-to-Point Encryption (MPPE)

Send PPP echo packets

The other options turned off, see screenshot also.

IPV4 and IPV6 are set to automatic.

As already noted, the basic vpn connection _works_, for a short time I can browse websites etc. successfully, but then suddenly everything is broken.

[Kristof S. (ksa1)]

Maybe it is the same situation as in https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1551823 ...

[Kristof S. (ksa1)]

To further proof the issue I now tested the same scenario with another wifi usb module in the same network/router setup, this time the driver module was rt2800usb.
Same result.

Before using a vpn (pppt) connection my network connection seemed very stable, I had no connection losses and performance was quite good.

Again establishing the vpn-ppt-connection with network manager (like above) works basically, I can open a few websites successfully for instance, but after a very short time the connection is completely faulty. This time the connection stayed functional about 30 seconds, then I got packet loss and no more network connections worked anymore.

Like before though, network manager showed the vpn connection is still "active" (established) albeit no more packets were transferred.

I attached the new error/debug log for this test.