modemmanager: init_epsbearer=none behavior differs from documentation and breaks EM7430

Package Name

modemmanager

Maintainer

@nickberry17

OpenWrt Version

25.12.5

OpenWrt Target/Subtarget

ipq40xx/generic

Steps to Reproduce

Environment

OpenWrt: 25.12.5
Target/Subtarget: ipq40xx/generic
Modem: Sierra Wireless EM7430
Chipset: Qualcomm Snapdragon X7 LTE-A
Firmware: SWI9X30C_02.38.00.00
Carrier config: DOCOMO_001.058_000
Connection type: MBIM


Configure a ModemManager interface:

config interface 'wwan'
        option proto 'modemmanager'
        option device '/sys/devices/platform/soc/8af8800.usb/8a00000.usb/xhci-hcd.0.auto/usb1/1-1'
        option apn 'dm.jplat.net'
        option allowedauth 'pap'
        option username 'jci@jci'
        option password 'jci'
        option iptype 'ipv4'
        option force_connection '1'

Leave init_epsbearer unset.

Run:

ifup wwan

The interface setup fails.

Then explicitly set:

uci set network.wwan.init_epsbearer='none'
uci commit network
ifdown wwan
ifup wwan

With the literal value init_epsbearer='none', the same modem and connection settings succeed.

The successful configuration also reconnects automatically after reboot.

### Actual Behaviour


### Actual Behaviour

```markdown
When `init_epsbearer` is unset, the ModemManager netifd backend attempts to delete/modify the initial EPS bearer.

Relevant log output:

```text
netifd: Interface 'wwan' is setting up now
netifd: wwan: successfully enabled the modem
netifd: wwan: Deleting initial EPS bearer...
ModemManager: processing user request to set initial EPS bearer settings...
ModemManager: failed setting initial EPS bearer settings: LTE attach configuration is unsupported
netifd: error: couldn't set initial EPS bearer properties:
GDBus.Error:org.freedesktop.ModemManager1.Error.Core.Unsupported:
Unsupported: LTE attach configuration is unsupported

ifstatus wwan reports:

{
        "up": false,
        "errors": [
                {
                        "subsystem": "modemmanager",
                        "code": "MM_INIT_EPS_BEARER_SET_FAILED"
                }
        ]
}

The Sierra Wireless EM7430 does not support this ModemManager LTE attach configuration API, so the otherwise valid LTE connection is prevented from coming up.

If I explicitly configure:

option init_epsbearer 'none'

the initial EPS bearer operation is skipped and the modem connects successfully.

Relevant successful log output:

netifd: successfully registered the modem
netifd: starting connection with apn 'dm.jplat.net'...
netifd: successfully connected the modem
netifd: Interface 'wwan' is now up

After that, ifstatus wwan shows:

"up": true
"l3_device": "wwan0"
"proto": "modemmanager"

The modem receives a valid IPv4 address and default route.

This appears inconsistent with the documented meaning of init_epsbearer=none, which is to not set an initial EPS bearer.

Expected behavior would be for an unset/default init_epsbearer and the explicit value init_epsbearer='none' to have the same semantics: do not call the ModemManager initial EPS bearer configuration API.


### Confirmation Checklist

- [x] The package is maintained in this repository.
- [x] I understand that issues related to [the base OpenWrt repository](https://github.com/openwrt/openwrt/issues) or [LuCI repository](https://github.com/openwrt/luci/issues) will be closed.
- [x] I am reporting an issue for OpenWrt, not an unsupported fork.

Start by tracing the ModemManager netifd backend handling of the init_epsbearer option, using the provided UCI configuration and ifup logs. Verify that an unset option and init_epsbearer='none' both skip the initial EPS bearer API, then confirm the EM7430 reaches an up state with ifstatus.