daniel-p-carvalho opened a new pull request, #20172:
URL: https://github.com/apache/nuttx/pull/20172
## Summary
In `devif_poll_pkt_connections()`, `pkt_poll()` records the outgoing IOB in
`pkt_conn->pendiob` so that any synchronous TX tap or loopback executed during
the driver callback can skip delivering the packet back to the sending socket.
Previously, `pendiob` was never cleared upon TX completion and would linger
across transmissions as a dangling pointer. Because the IOB pool is small and
recycled quickly (LIFO), a subsequent incoming packet from the network
frequently reused the same IOB buffer address, causing `pkt_in()` to falsely
match `conn->pendiob == dev->d_iob` and drop legitimate RX packets as
self-echoes.
This PR drops the `pendiob` reference immediately after `callback(dev)`
returns in `devif_poll_pkt_connections()`, ensuring the pointer never outlives
the transmission cycle and cannot falsely suppress future incoming packets.
Also fixes a pre-existing `nxstyle` alignment issue in `devif_poll.c` IPv6
version-check block (unrelated `nerr()` call), ensuring zero checkpatch errors
on touched files.
Suggested-by: @zhhyu7
## Impact
- Bug fix in packet socket (`AF_PACKET` / `CONFIG_NET_PKT`) receive path.
- Prevents random / silent packet drops on high-throughput or low-memory
systems where IOB buffers are recycled rapidly.
- No ABI or user-visible API changes.
## Testing
1. Verified with `tools/checkpatch.sh -g HEAD`: 100% checks pass.
2. Verified on physical hardware (STM32H753, RMII Ethernet):
- Firmware running with `CONFIG_NET_PKT=y` and the updated `devif_poll.c`.
- Tested bidirectional ICMP ping traffic between Linux host and the board
continuously with 0% packet loss and clean IOB buffer recycling.
3. Verified on physical hardware (STM32F407, RMII Ethernet with PTP IEEE
1588):
- High-rate packet socket exchanges (`Pdelay_Req` / `Pdelay_Resp`) run
continuously without false self-echo drops.
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