Unable to get IPv4 over LTE

[Vincent Bernat]

Hey!

I got an odd problem since some time.

Bus 002 Device 045: ID 1199:a001 Sierra Wireless, Inc.
ii  modemmanager      1.4.12-1      amd64         D-Bus service for managing modems
Linux zoro 4.3.0-1-amd64 #1 SMP Debian 4.3.3-5 (2016-01-04) x86_64 GNU/Linux

When I am connected over LTE for the first time since a few days, I
cannot get an IPv4. NM just starts a dhclient and the dhclient doesn't
get an IP.

NetworkManager[6880]: <info>  (cdc-wdm0): Activation: starting connection 'Sunrise' (fbce8984-7556-44e9-ad99-32d61e7fed7
NetworkManager[6880]: <info>  (cdc-wdm0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
NetworkManager[6880]: <info>  NetworkManager state is now CONNECTING
ModemManager[6866]: <info>  Simple connect started...
ModemManager[6866]: <info>  Simple connect state (4/8): Wait to get fully enabled
ModemManager[6866]: <info>  Simple connect state (5/8): Register
ModemManager[6866]: <info>  Simple connect state (6/8): Bearer
ModemManager[6866]: <info>  Simple connect state (7/8): Connect
ModemManager[6866]: <info>  Modem /org/freedesktop/ModemManager1/Modem/0: state changed (registered -> connecting)
NetworkManager[6880]: <info>  (cdc-wdm0): modem state changed, 'registered' --> 'connecting' (reason: user-requested)
ModemManager[6866]: <info>  Modem /org/freedesktop/ModemManager1/Modem/0: state changed (connecting -> connected)
ModemManager[6866]: <info>  Simple connect state (8/8): All done
NetworkManager[6880]: <info>  (cdc-wdm0): modem state changed, 'connecting' --> 'connected' (reason: user-requested)
NetworkManager[6880]: <info>  (cdc-wdm0): device state change: prepare -> config (reason 'none') [40 50 0]
NetworkManager[6880]: <info>  (cdc-wdm0): device state change: config -> ip-config (reason 'none') [50 70 0]
NetworkManager[6880]: <info>  Activation (wwan0) Beginning DHCPv4 transaction (timeout in 15 seconds)
NetworkManager[6880]: <info>  dhclient started with pid 7248
NetworkManager[6880]: <info>  (cdc-wdm0): IPv6 configuration disabled
dhclient[7248]: DHCPDISCOVER on wwan0 to 255.255.255.255 port 67 interval 5
dhclient[7248]: DHCPDISCOVER on wwan0 to 255.255.255.255 port 67 interval 10
dhclient[7248]: DHCPDISCOVER on wwan0 to 255.255.255.255 port 67 interval 15
NetworkManager[6880]: <warn>  (wwan0): DHCPv4 request timed out.
NetworkManager[6880]: <info>  (wwan0): DHCPv4 state changed unknown -> timeout
NetworkManager[6880]: <info>  (wwan0): canceled DHCP transaction, DHCP client pid 7248
NetworkManager[6880]: <info>  (wwan0): DHCPv4 state changed timeout -> done

When I am not over LTE, the steps are different:

ModemManager[8662]: <info>  Simple connect state (8/8): All done
NetworkManager[8676]: <info>  (cdc-wdm0): modem state changed, 'connecting' --> 'connected' (reason: user-requested)
NetworkManager[8676]: <info>  (cdc-wdm0): device state change: prepare -> config (reason 'none') [40 50 0]
NetworkManager[8676]: <info>  (cdc-wdm0): device state change: config -> ip-config (reason 'none') [50 70 0]
NetworkManager[8676]: <info>  (cdc-wdm0): IPv4 static configuration:
NetworkManager[8676]: <info>    address 10.129.4.193/24
NetworkManager[8676]: <info>    gateway 10.129.4.1
NetworkManager[8676]: <info>    DNS 10.200.102.243
NetworkManager[8676]: <info>    DNS 10.200.102.244
[...]

After that, it works just fine. If I happen to switch back to LTE during
the connection, the connection keeps working. If I disconnect and
reconnect over LTE, it connects immediately.

I don't remember exactly when things has changed, but it worked fine in
the past over LTE. I have tried with three different carriers with the
same symptoms. If I use the modem daily, I have no problem
connecting. If I don't connect for a week, I have to find a way to not
be over LTE to be able to connect the first time.
-- 
And do you think (fop that I am) that I could be the Scarlet
Pumpernickel?