Need to restart PC in order for NetworkManager to connect to LTE

[Yury Kamnev <yury kamnev alberblanc com>]

I am experiencing quite a strange behavior when trying to set up LTE connection via network manager and mc7455 usb modem.

On first boot it just hangs:

    > nmcli
    cdc-wdm0: connecting (prepare) to lte
        "cdc-wdm0"
        modem (qmi_wwan), hw

Setting connection down and up does not help. Setting interface up/down also has no effects. **The only thing that helps is `sudo reboot` after which nm is able to connect.** Here is modem manager info:


      > mmcli -m 0
      -------------------------
      Hardware |   manufacturer: 'Sierra Wireless, Incorporated'
               |          model: 'MC7455'
               |       revision: 'SWI9X30C_02.24.05.06 r7040 CARMD-EV-FRMWR2 2017/05/19 06:23:09'
               |      supported: 'gsm-umts
               |                  lte
               |                  gsm-umts, lte'
               |        current: 'lte'
               |   equipment id: '359072065668879'
      -------------------------
      System   |         device: '/sys/devices/70090000.xusb/usb1/1-2/1-2.2'
               |        drivers: 'qmi_wwan'
               |         plugin: 'Sierra'
               |   primary port: 'cdc-wdm0'
               |          ports: 'cdc-wdm0 (qmi), wwan0 (net), wwan1 (net), cdc-wdm1 (qmi)'
      -------------------------
      Numbers  |           own : '79215547030'
      -------------------------
      Status   |           lock: 'sim-pin2'
               | unlock retries: 'sim-pin (3), sim-pin2 (3), sim-puk (10), sim-puk2 (10)'
               |          state: 'enabled'
               |    power state: 'on'
               |    access tech: 'unknown'
               | signal quality: '0' (cached)
      -------------------------
      Modes    |      supported: 'allowed: 4g; preferred: none'
               |        current: 'allowed: 4g; preferred: none'
      -------------------------
      Bands    |      supported: 'u2100, u1800, u1900, u17iv, u850, u900, eutran-i, eutran-ii, eutran-iii, eutran-iv, eutran-v, eutran-vii, eutran-viii, eutran-xii, eutran-xiii, eutran-xx, eutran-xxv, eutran-xli'
               |        current: 'u2100, u1800, u1900, u17iv, u850, u900, eutran-i, eutran-ii, eutran-iii, eutran-iv, eutran-v, eutran-vii, eutran-viii, eutran-xii, eutran-xiii, eutran-xx, eutran-xxv, eutran-xli'
      -------------------------
      IP       |      supported: 'ipv4, ipv6, ipv4v6'
      -------------------------
      3GPP     |           imei: '359072065668879'
               |  enabled locks: 'none'
               |    operator id: 'unknown'
               |  operator name: 'unknown'
               |   subscription: 'unknown'
               |   registration: 'unknown'
      -------------------------
      SIM      |           path: '/org/freedesktop/ModemManager1/SIM/0'
   
      -------------------------
      Bearers  |          paths: 'none'


Related systemctl logs:

    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.3910] modem["cdc-wdm0"]: modem state changed, 'disabled' --> 'enabling' (reason: user preference)
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.3949] manager: (cdc-wdm0): new Broadband device (/org/freedesktop/NetworkManager/Devices/4)
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.3954] device (cdc-wdm0): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.3958] device (cdc-wdm0): modem state 'enabling'
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.3968] device (cdc-wdm0): state change: unavailable -> disconnected (reason 'none', sys-iface-state: 'managed')
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.3976] policy: auto-activating connection 'lte'
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.4000] device (cdc-wdm0): Activation: starting connection 'lte' (13d2ea02-ff40-4d56-848e-5d61f064db7b)
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.4005] device (cdc-wdm0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
    Jun 29 14:33:09 localhost.localdomain NetworkManager[3380]: <info>  [1593441189.4011] manager: NetworkManager state is now CONNECTING
    Jun 29 14:33:12 localhost.localdomain NetworkManager[3380]: <info>  [1593441192.1162] modem["cdc-wdm0"]: modem state changed, 'enabling' --> 'enabled' (reason: user-requested)


    Jun 29 14:33:09 localhost.localdomain ModemManager[3383]: <info>  Simple connect state (4/8): Wait to get fully enabled
    Jun 29 14:33:12 localhost.localdomain ModemManager[3383]: <info>  Modem /org/freedesktop/ModemManager1/Modem/0: state changed (enabling -> enabled)
    Jun 29 14:33:12 localhost.localdomain ModemManager[3383]: <info>  Simple connect state (5/8): Register
    Jun 29 14:34:12 localhost.localdomain ModemManager[3383]: <info>  Simple connect started...
    Jun 29 14:34:12 localhost.localdomain ModemManager[3383]: <info>  Simple connect state (4/8): Wait to get fully enabled
    Jun 29 14:34:12 localhost.localdomain ModemManager[3383]: <info>  Simple connect state (5/8): Register
    Jun 29 14:35:15 localhost.localdomain ModemManager[3383]: <info>  Simple connect started...
    Jun 29 14:35:15 localhost.localdomain ModemManager[3383]: <info>  Simple connect state (4/8): Wait to get fully enabled
    Jun 29 14:35:15 localhost.localdomain ModemManager[3383]: <info>  Simple connect state (5/8): Register

My connection file:

    sudo cat /etc/NetworkManager/system-connections/lte
    [connection]
    id=lte
    uuid=13d2ea02-ff40-4d56-848e-5d61f064db7b
    type=gsm
    interface-name=cdc-wdm0
    permissions=
   
    [gsm]
    apn=internet
   
    [ipv4]
    dns-search=
    method=auto
   
    [ipv6]
    addr-gen-mode=stable-privacy
    dns-search=
    method=auto

Versions:

    Ubuntu 18.04
    > NetworkManager --version
    1.10.6
    > ModemManager --version
    ModemManager 1.6.8

Hope for your help.

Thanks!

--

Sincerely yours, Kamnev Yuriy