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ModemManager: enable all available FCC-unlock scripts #3549

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merged 2 commits into from
Nov 1, 2023
Merged

ModemManager: enable all available FCC-unlock scripts #3549

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eb55196
ModemManager: enable all available FCC-unlock scripts
milan-zededa Oct 27, 2023
fb05a34
wwan: try to find more useful reason for failure than DeadlineExceeded
milan-zededa Oct 30, 2023
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29 changes: 29 additions & 0 deletions pkg/wwan/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -931,3 +931,32 @@ rtt min/avg/max/mdev = 44.159/66.162/122.881/32.853 ms

Now you have verified that your modem is compatible with EVE OS and you can try to configure
cellular connection properly from the controller.

## FCC lock

The [FCC](https://www.fcc.gov/) lock is a software lock integrated in WWAN modems shipped by several
different laptop and edge device vendors, such as Lenovo, Dell, or HP. This locks prevents the WWAN
modem from being put online until some specific unlock procedure (usually a magic command sent
to the modem) is executed. The purpose of this lock is to have a way to bind the WWAN modem
to a specific device, so that the whole bundle of device+modem can go through the FCC certification
process for radio-enabled devices in the USA. This lock has no other known purpose out of the US
regulation.

The FCC lock is part of a mutual authentication attempt between modem and device. On the device side,
BIOS is configured with an allow-list of modems that the device can be used with. On the modem side,
the FCC lock ensures that the modem is unlocked only by approved devices.

The main challenge faced from the perspective of EVE is that device vendors often provide FCC unlock
utilities exclusively for Windows or macOS, and their devices are not FCC-certified for use with
GNU/Linux distributions. Fortunately, the ModemManager developers have successfully reverse-engineered
FCC unlock procedures for some widely used Sierra Wireless and Quectel modems, providing scripts
for these operations. In some cases, collaboration between ModemManager developers, device vendors,
and modem manufacturers has resulted in FCC unlock scripts that have been verified by all parties.
However, in other instances, there may be a slight risk associated with running reverse-engineered
unlock procedures. Therefore, ModemManager will not use FCC unlock scripts unless explicitly enabled.

For more information on FCC lock and how ModemManager deals with this challenge, please refer to this
[article](https://modemmanager.org/docs/modemmanager/fcc-unlock/).

In the case of EVE, the decision has been made to enable all FCC unlock scripts that come with
ModemManager and then potentially disable only those for which issues are reported.
19 changes: 19 additions & 0 deletions pkg/wwan/mm-init.sh
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Expand Up @@ -4,6 +4,24 @@

set -e

# Enable all available FCC-unlock scripts.
# For more info, see: https://modemmanager.org/docs/modemmanager/fcc-unlock/
enable_fcc_unlock() {
SOURCE_DIR="/usr/share/ModemManager/fcc-unlock.available.d/"
TARGET_DIR="/etc/ModemManager/fcc-unlock.d/"

for SCRIPT in "${SOURCE_DIR}"*; do
if [ -f "$SCRIPT" ]; then
SCRIPT_NAME="$(basename "$SCRIPT")"
ln -sf "$SCRIPT" "${TARGET_DIR}${SCRIPT_NAME}"
fi
done

# "Quectel EM05G Smart Gateway" (2c7c:0311) is compatible with the same
# FCC unlock script as used for the regular "Quectel EM05G" (2c7c:030a).
ln -sf "${SOURCE_DIR}2c7c:030a" "${TARGET_DIR}2c7c:0311"
}

echo "Loading kernel modules used by ModemManager"
modprobe -a qcserial usb_wwan qmi_wwan cdc_wdm cdc_mbim cdc_acm
echo "Kernel modules are loaded"
Expand All @@ -21,6 +39,7 @@ udevadm trigger
echo "Udev daemon started"

echo "Starting Modem Manager"
enable_fcc_unlock
ModemManager --debug &

echo "Starting Modem Manager Agent"
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11 changes: 10 additions & 1 deletion pkg/wwan/mmagent/mmdbus/client.go
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Expand Up @@ -1243,7 +1243,16 @@ func (c *Client) runSimpleConnect(modemObj dbus.BusObject,
var bearerPath dbus.ObjectPath
modem := c.modems[string(modemObj.Path())]
err := c.callDBusMethod(modemObj, SimpleMethodConnect, &bearerPath, connProps)
if err != nil && strings.HasPrefix(err.Error(), "No such interface") && modem != nil {
var errIsUseless bool
if err != nil {
if strings.HasPrefix(err.Error(), "No such interface") {
errIsUseless = true
}
if errors.Is(err, context.DeadlineExceeded) {
errIsUseless = true
}
}
if errIsUseless && modem != nil {
// Try to determine more useful connection failure reason.
for _, simCard := range modem.Status.SimCards {
if !simCard.SlotActivated {
Expand Down
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