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Matter-over-Wi-Fi "no response" - net/driver layer capture (follow-up)
Matter Light Bulb, NCS v3.3.4, nrf54lm20dk/nrf54lm20a/cpuapp + nrf7002eb2
Snippet: nrf70-driver-debug.  Captured: 2026-10-15
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CONCLUSION (agrees with your assessment)
----------------------------------------
This is NOT an nRF70 Wi-Fi TX stall. While the device is "No Response" in Apple
Home, ICMPv6 ping to LAN peers succeeds in both directions. Wi-Fi TX is working.
The failure is above the nRF70 shim (Matter operational discovery / mDNS / IPv6
session), not Wi-Fi TX completion.

HOW THE DATA WAS TAKEN
----------------------
Device commissioned to SSID "Netanel" (5 GHz, WIFI 6, RSSI -44, link COMPLETED),
then driven from Apple Home until it stopped responding. With the device in the
failed state (serial opened without DTR/RTS so the capture cannot reset it; no
reboot occurred during the window), the following were captured.

1) net stats  (5 snapshots over the stuck window)
   IPv6 recv : 502 -> 595   (+93, RX advancing)
   IPv6 sent : 206 -> 214   (+8,  TX offered-load nearly flat)
   IPv6 drop : 3   -> 3      (no IP drops)
   UDP  recv : 375 -> 431   (+56)
   UDP  sent : 163 -> 169   (+6)
   Send Drops: 0            (Wi-Fi is NOT dropping TX)
   => The stack has largely stopped OFFERING packets to send; Wi-Fi is not
      refusing or dropping them.

2) wifi statistics
   Bytes sent : 49465 -> 49465 -> 49465  (frozen across the whole window)
   Bytes recv : 134409 -> 155943         (advancing)
   Unicast sent 170 vs Unicast received 260
   => Outbound data has dried up at the host, not at the Wi-Fi TX path.

3) nrf70 util tx_stats 0  (all snapshots)
   Every AC: Outstanding tokens 0, pending_q_len 0  (no driver backlog)

4) ICMPv6 ping WHILE STUCK  (the decisive test)
   net ping fe80::1296:93ff:feac:cd5a       -> 3/3 replies, ~50-87 ms
   net ping -c 3 fe80::82b9:7aff:fea3:7512  -> 3/3 replies, ~50-68 ms
   net ping fe80::fe3f:a6ff:feff:fdb2 (router) -> timeout (peer did not answer
       link-local ICMP; the two host peers above confirm TX+RX both work)
   => The nRF70 transmits unicast to air and receives replies while "stuck".
      Raw IPv6 TX is healthy.

MATTER / UPPER-LAYER SYMPTOMS DURING THE STALL
----------------------------------------------
   [DIS] Timeout waiting for mDNS resolution
   [DIS] OperationalSessionSetup[...]: operational discovery failed: 32
   [DMG] Failed to establish CASE for subscription-resumption with error '32'
   [IN]  IPV6_PKTINFO failed: 109            (seen at init)
   Earlier (healthy boot) also showed: "Failed to allocate net_pkt".
   Device is IPv6-only in this build: "net ipv4 -> IPv4 support: disabled".

NOTES / LIMITATIONS (so nothing is overstated)
----------------------------------------------
 - net mem could not quantify pool usage: the build reports
   "Set CONFIG_NET_BUF_POOL_USAGE to enable net_buf allocation support."
   To investigate the earlier net_pkt alloc failure properly, a rebuild with
   CONFIG_NET_BUF_POOL_USAGE=y (and CONFIG_NET_STATISTICS_* already on) is needed.
 - First ping attempt in the log used a "%1" scope suffix which this shell
   rejects as "Invalid IP address"; the PING RETRY section (bare address) is the
   valid one and is what the result above refers to.

ATTACHED
--------
   net_stall_capture.log       - primary: 5x net iface/stats/mem/wifi statistics/
                                 tx_stats while stuck, plus the PING RETRY section.
   net_baseline_healthy.log    - same commands captured while working (baseline).
   (Prior nRF70 TX-stall logs tx_stall_capture*.log available on request.)

SUGGESTED NEXT STEP
-------------------
Given ping proves Wi-Fi TX is fine, focus on the Matter operational / mDNS / IPv6
path (CASE error 32, mDNS resolution timeout, IPV6_PKTINFO 109). Happy to rebuild
with CONFIG_NET_BUF_POOL_USAGE=y to confirm/deny net_buf exhaustion if useful.
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