Dell DW5821e-eSIM & DW5829e-eSIM on Linux

Dell DW5829e-eSIM over QMI

USB 413c:81e4, Qualcomm Snapdragon X20. The eUICC sits on UIM slot 2.

1. USB configuration

The modem enumerates in configuration 2 (MBIM) by default. lpac’s QMI APDU driver and qmicli WDS sessions need configuration 1 (QMI), which exposes /dev/cdc-wdm0 through qmi_wwan and wwan0. udev/78-dell-dw5829e.rules pins it at enumeration time:

ACTION=="add", SUBSYSTEM=="usb", ATTR{idVendor}=="413c", ATTR{idProduct}=="81e4", ATTR{bConfigurationValue}=="2", ATTR{bConfigurationValue}="1"

Verify: cat /sys/bus/usb/devices/<bus-port>/bConfigurationValue → 1, and ls /dev/cdc-wdm* shows the control device.

2. ModemManager

Disable and mask it. With MM running, the QMI client IDs are taken and lpac fails to open an APDU channel with errors that look like eUICC faults.

3. lpac over QMI

Run lpac through qmi-proxy (ships with libqmi) so the control device can be shared with qmicli. The lpac-qmi wrapper we use does, in order: stop MM (belt and braces), USB unbind/rebind of the modem, start qmi-proxy, run lpac with the QMI APDU backend on /dev/cdc-wdm0 and UIM slot 2. See lpac.md for the backend/environment details and the RPATH note.

lpac-qmi profile list
lpac-qmi profile enable <AID>
lpac-qmi profile download -s <SM-DP+ host> -m <matching id>

4. Switching a profile — the full cycle

scripts/dw5829e-qmi/esim-switch-profile.sh <AID> <APN>:

  1. stop the WDS session (esim-bearer-down.sh);
  2. USB unbind/rebind so nothing holds the control device;
  3. lpac profile disable <current> / lpac profile enable <target>;
  4. DMS reset — qmicli -d /dev/cdc-wdm0 --dms-set-operating-mode=reset. The modem re-enumerates on USB; wait for it (≈30 s) instead of polling the device node that is about to disappear;
  5. USB rebind again, then start the data session (step 5 below);
  6. routing + network namespace.

A switch takes 40–60 s. Do not call lpac while a DMS reset is in flight.

5. Data session (WDS)

esim-bearer-up.sh <APN>:

echo Y > /sys/class/net/wwan0/qmi/raw_ip      # raw-IP mode, interface down first
qmicli -d /dev/cdc-wdm0 -p --wds-start-network="apn=<APN>,ip-type=4" --client-no-release-cid
qmicli -d /dev/cdc-wdm0 -p --wds-get-current-settings   # IP, gateway, DNS, MTU

Assign the address to wwan0, add the default route in a dedicated routing table (we use table 100) with an ip rule from <wwan ip> lookup 100, never in main: the box keeps its wired default. The session state (IP, prefix, gateway, table, APN, profile) is written to /run/esim-dw5829e.state so the other scripts and the namespace helper can find it.

esim-bearer-refresh.sh restarts the session for a carrier-side idle timeout (NAT/PDP expiry after minutes of silence). Caveat: our refresh script calls esim-bearer-up.sh, which does a full USB unbind/rebind — the modem disappears from /dev for 10–20 s. A watchdog that treats that window as “modem gone” will escalate on its own side effect; see pitfalls.md.

6. Network namespace

scripts/common/netns-esim-up.sh creates namespace esim with a veth pair (10.200.200.0/30), a default route through the host side, SNAT on the host to the modem address, and a resolv.conf for the namespace. Anything run with ip netns exec esim … uses the mobile uplink and nothing else — the clean way to measure “what does this operator pass” without touching the host’s routing.

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