Lumpiasty
2d69cc6569
The embedded BroadMobi BM806C modem (Qualcomm MDM9225, firmware
M1.2.0_E1.0.1_A1.1.8) in the D-Link DWR-921 C1 has two independent
firmware bugs that together break the QMI data plane:
1. Modem accepts 802.3 framing but its 802.3 path is buggy — downlink
frames never reach the host kernel. raw-ip framing works.
2. qmish calls uqmi --start-network --apn <foo>, which triggers
FS#1363: the modem establishes a phantom bearer that gets IP
addresses but has no working data path. Using --start-network
--profile <N> (referencing a pre-configured NVRAM profile with
the same APN) works correctly.
Fixes applied:
- qmish patches (3x community.openwrt.lineinfile):
* Replace --set-data-format 802.3 with raw-ip
* Replace --wda-set-data-format 802.3 with raw-ip
* Bracket raw_ip sysfs write with ip link down/up (kernel rejects
write with -EBUSY when wwan0 is already up)
- Modem NVRAM: create/modify profile 2 (internetipv6, ipv6) for the
IPv6 APN — profile 1 is already managed by qmish's --modify-profile
- UCI wwan: add profile=1 and v6profile=2 so qmish uses --start-network
--profile instead of --apn on both the v4 and v6 legs
- Firewall: add wwan zone (input REJECT, output ACCEPT, forward REJECT)
and Allow-ICMPv6-wwan rule
- main.yml: reorder — packages (including usb-modeswitch) now run
before wwan setup, so the modem is out of EDL mode when wwan.yml
queries it for profile creation
See docs/wwan-bm806c-qmi-workaround.md for the full diagnosis
(what we ruled out, how we confirmed, manual setup steps, component
versions, future upstreaming).
106 lines
5.0 KiB
YAML
106 lines
5.0 KiB
YAML
---
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# Configures the embedded BroadMobi BM806C LTE modem for QMI use.
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#
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# Two workarounds are applied here for documented bugs in this modem's firmware
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# (M1.2.0_E1.0.1_A1.1.8, no public updates available):
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#
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# 1. raw-ip framing. The modem advertises 802.3 support but the 802.3 firmware
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# path is buggy — downlink frames don't reach the host. raw-ip works.
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# See bmork's kernel commit "net: qmi_wwan: support 'raw IP' mode":
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# 'newer generations of QMI hardware and firmware have moved towards
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# defaulting to raw IP mode instead, followed by an increasing number of
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# bugs in the already buggy 802.3 firmware implementation'.
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# qmi.sh hardcodes 802.3; we patch it in-place to use raw-ip.
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#
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# 2. --profile instead of --apn on --start-network. With --apn, the modem
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# establishes a phantom bearer that has no working downlink data path.
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# With --profile referencing a pre-configured NVRAM profile, data flows.
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# See https://forum.openwrt.org/t/problem-with-bm806u-e1-dwr-921-c3/130094
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# and https://github.com/openwrt/openwrt/issues/6295 (FS#1363).
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# qmi.sh already supports the 'profile' UCI option; we set it in the
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# wwan interface config (profile=1 for IPv4, v6profile=2 for IPv6).
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# qmi.sh's --modify-profile call writes profile 1; profile 2 is bootstrapped
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# here for the IPv6-specific APN.
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# Patch qmi.sh to request raw-ip framing instead of 802.3. Two distinct uqmi
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# calls in the upstream proto handler request the data format — both must be
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# patched for the readback to return raw-ip and trigger the kernel driver's
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# sysfs raw_ip=Y flip. Idempotent: lineinfile is a no-op once the patterns
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# no longer match.
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# Diff output is suppressed for these tasks: the full qmi.sh file (~13 KB) is
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# included in both before/after diff payloads, and ansible's SSH stdout parser
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# truncates the resulting JSON, causing 'Module result deserialization failed:
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# No end of json char found'. The change is self-evident from the task name.
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- name: Patch qmi.sh — set-data-format to raw-ip
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community.openwrt.lineinfile:
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path: /lib/netifd/proto/qmi.sh
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regex: '^(\s*uqmi .* --set-data-format) 802\.3(.*)$'
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line: '\1 raw-ip\2'
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backrefs: true
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diff: false
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- name: Patch qmi.sh — wda-set-data-format to raw-ip
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community.openwrt.lineinfile:
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path: /lib/netifd/proto/qmi.sh
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regex: '^(\s*uqmi .* --wda-set-data-format) 802\.3(.*)$'
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line: '\1 raw-ip\2'
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backrefs: true
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diff: false
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# The kernel rejects writes to /sys/class/net/wwan0/qmi/raw_ip while the netdev
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# is up: 'Cannot change a running device' (-EBUSY). qmi.sh tries to flip it
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# while the interface is up — this works in 802.3 mode (no-op when already N),
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# but with our raw-ip patch above, the flip is mandatory and must succeed.
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# We bracket the sysfs write with ip link down/up.
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- name: Patch qmi.sh — bracket raw_ip sysfs write with ip link down/up
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community.openwrt.lineinfile:
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path: /lib/netifd/proto/qmi.sh
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regex: '^(\s*)echo "Y" > /sys/class/net/\$ifname/qmi/raw_ip$'
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line: '\1ip link set $ifname down; echo "Y" > /sys/class/net/$ifname/qmi/raw_ip; ip link set $ifname up'
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backrefs: true
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diff: false
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# Profile 2 in modem NVRAM holds the IPv6 APN. qmi.sh only manages profile 1
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# (the v4 APN via --modify-profile, line 314); profile 2 is our responsibility.
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# These steps are skipped if the modem isn't enumerated yet (fresh boot before
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# usb-modeswitch completes, or modem in a fault state).
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- name: Check if QMI device is available
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community.openwrt.stat:
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path: /dev/cdc-wdm0
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register: wwan_cdc_wdm
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- name: Query QMI profile list
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community.openwrt.command:
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cmd: uqmi -t 3000 -d /dev/cdc-wdm0 --get-profile-list 3gpp
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register: wwan_profile_list
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changed_when: false
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failed_when: false
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when: wwan_cdc_wdm.stat.exists | default(false)
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- name: Configure IPv6 APN profile 2
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when:
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- wwan_cdc_wdm.stat.exists | default(false)
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- wwan_profile_list.rc | default(1) == 0
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- wwan_profile_list.stdout | default('') | trim | length > 0
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- wwan_profile_list.stdout | default('') | trim is match('^\\{')
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block:
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- name: Parse profile indexes
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ansible.builtin.set_fact:
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wwan_profile_indexes: >-
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{{ (wwan_profile_list.stdout | from_json).profiles
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| default([]) | map(attribute='index') | list }}
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- name: Create profile 2 for IPv6 APN if missing
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community.openwrt.command:
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cmd: uqmi -t 3000 -d /dev/cdc-wdm0 --create-profile 3gpp --apn internetipv6 --pdp-type ipv6
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when: 2 not in wwan_profile_indexes
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# --modify-profile is idempotent at the modem level. We can't detect
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# whether values changed (uqmi doesn't return diff info), so we always
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# report 'ok' (changed_when: false) to keep play output clean. The cost
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# of always calling this is one QMI roundtrip.
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- name: Ensure profile 2 settings are current
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community.openwrt.command:
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cmd: uqmi -t 3000 -d /dev/cdc-wdm0 --modify-profile 3gpp,2 --apn internetipv6 --pdp-type ipv6
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changed_when: false
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