Sarthak-Pandey commented on PR #20702:
URL: https://github.com/apache/nuttx/pull/20702#issuecomment-6557581465
Hi @casaroli and @acassis,
Thank you for the detailed feedback. I have resolved both the TCP thread
safety point at `net/inet/inet_sockif.c:1882` and added the active CAN
multi-iov frame transmission & truncation run on `sim:can`.
### 1. Summary of Changes
1. **TCP Thread Safety (`net/inet/inet_sockif.c:1882`)**:
- Reverted the per-iov `inet_send()` loop. We now preserve the universal
gather path in `inet_sendmsg()` across all configurations (including with write
buffers). This submits all vector chunks atomically in a single `inet_send()`
call under connection lock, completely eliminating the possibility of
concurrent thread data interleaving between `iov` slices.
2. **PR Description Corrections**:
- Documented that `msg_iovlen == 0` returns `-EMSGSIZE` (matching the
codebase and POSIX standard).
- Updated the TCP section to describe the atomic gather path.
3. **Active CAN Frame & Truncation Run on `sim:can`**:
- Ran active CAN socket verification on `sim:can` with `can0` interface:
- Multi-iov Gather Send: 3 `iovec`s (`can_id` 4B, `can_dlc` 1B, payload
11B -> 16B CAN frame) transmitted cleanly.
- Multi-iov Scatter Recv: 2 `iovec`s (8B + 8B -> 16B CAN frame)
received and verified (`can_id == 0x123`, `can_dlc == 8`, payload matched).
- Truncation Test: shorter `iovec` buffer (8B) received partial
datagram with `MSG_TRUNC` set in `msg_flags`.
### 2. Comprehensive Test Matrix
| Scope / Target | Platform | Result | Verification Notes |
|---|---|---|---|
| **Active CAN Frame Gather/Scatter** | `sim:can`
(`CONFIG_SIM_CANDEV_SOCK=y`) | **PASS** | 3 iovs gathered -> frame sent; 2 iovs
scattered <- frame verified (`can_id=0x123`, `dlc=8`). |
| **Active CAN Truncation** | `sim:can` (`CONFIG_SIM_CANDEV_SOCK=y`) |
**PASS** | Shorter iov buffer returns 8B and asserts `MSG_TRUNC` in
`msg_flags`. |
| **UNIX / Local Sockets** | Flat (`sim:tcploop`) & Kernel (`rv-virt:knsh`)
| **PASS** | 3 iovs send -> 4 iovs recv with `MSG_WAITALL`. 100% data match. |
| **UDP Datagram Sockets** | Flat (`sim:tcploop`) & Kernel (`rv-virt:knsh`)
| **PASS** | Multi-iov send/recv + shorter iov truncation verification. |
| **TCP Stream Sockets** | Flat (`sim:tcploop`) & Kernel (`rv-virt:knsh`) |
**PASS** | Multi-iov atomic send across stream boundaries. |
| **IOB Unit & Stress Testing** | Flat (`sim:tcploop`) | **PASS** | 10k
throttled + 10k unthrottled iterations without leaks. |
| **Existing Application (`tcpblaster`)** | Flat (`sim:tcploop`) | **PASS**
| Streamed >5MB over TCP loopback with write buffers enabled. |
### 3. Execution Logs
<details>
<summary><b>sim:can Active CAN Frame & Truncation Run Log</b></summary>
```text
nsh> ifconfig
can0 Link encap:UNSPEC at UP mtu 72
inet addr:0.0.0.0 mask:0.0.0.0
nsh> net_iov_test
============================================================
Apache NuttX Scatter-Gather (msg_iov) Verification Suite
============================================================
[TEST 1/4] UNIX Domain Stream Sockets (AF_LOCAL): [SKIP] (unconfigured)
[TEST 2/4] UDP Datagram Sockets (AF_INET, SOCK_DGRAM): [SKIP] (unconfigured)
[TEST 3/4] TCP Stream Sockets (AF_INET, SOCK_STREAM): [SKIP] (unconfigured)
------------------------------------------------------------
[TEST 4/4] CAN RAW Sockets (AF_CAN, SOCK_RAW)
------------------------------------------------------------
[PASS] can sendmsg(msg_iovlen = 0) returns -EMSGSIZE
[PASS] can recvmsg(msg_iovlen = 0) returns -EMSGSIZE
[PASS] can sendmsg(len != CAN_MTU) returns -EINVAL
[PASS] can sendmsg gather (3 iovs -> 16 bytes frame)
[PASS] can recvmsg scatter (2 iovs <- 16 bytes, verified ID=0x123 DLC=8)
[PASS] can recvmsg truncation (shorter iov: ret=8, MSG_TRUNC set)
============================================================
>>> ALL SCATTER-GATHER (IOV) TESTS PASSED! <<<
============================================================
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