fix: rate-limit CSI sends and add ENOMEM backoff to prevent crash

The CSI callback fires for every WiFi frame in promiscuous mode (100-500+ fps). Each call invoked sendto() synchronously, exhausting lwIP packet buffers (errno 12 = ENOMEM). The rapid-fire failures cascaded into a LoadProhibited guru meditation crash. Two fixes: 1. csi_collector.c: Rate-limit UDP sends to 50 Hz (20ms interval). CSI frames arriving between sends are dropped — the sensing pipeline only needs 20-50 Hz. 2. stream_sender.c: When sendto fails with ENOMEM, suppress further sends for 100ms to let lwIP reclaim buffers. Logs the backoff event and resumes automatically. Closes #127 Co-Authored-By: claude-flow <ruv@ruv.net>
docs: ADR-044 provisioning tool enhancements
2026-07-28 18:21:42 +00:00 · 2026-03-03 15:59:44 -05:00 · 2026-03-03 15:57:34 -05:00 · 2026-03-03 15:53:43 -05:00
3 changed files with 280 additions and 8 deletions
@@ -0,0 +1,214 @@
+# ADR-044: Provisioning Tool Enhancements
+
+**Status**: Proposed
+**Date**: 2026-03-03
+**Deciders**: @ruvnet
+**Supersedes**: None
+**Related**: ADR-029, ADR-032, ADR-039, ADR-040
+
+---
+
+## Context
+
+The ESP32-S3 CSI node provisioning script (`firmware/esp32-csi-node/provision.py`) is the primary tool for configuring pre-built firmware binaries without recompiling. It writes NVS key-value pairs that the firmware reads at boot.
+
+After #131 added TDM and edge intelligence flags, the script now covers the most-requested NVS keys. However, there remain gaps between what the firmware reads from NVS (`nvs_config.c`, 20 keys) and what the provisioning script can write (13 keys). Additionally, the script lacks usability features that would help field operators deploying multi-node meshes.
+
+### Gap 1: Missing NVS Keys (7 keys)
+
+The firmware reads these NVS keys at boot but the provisioning script has no corresponding CLI flags:
+
+| NVS Key | Type | Firmware Default | Purpose |
+|---------|------|-----------------|---------|
+| `hop_count` | u8 | 1 (no hop) | Number of channels to hop through |
+| `chan_list` | blob (u8[6]) | {1,6,11} | Channel numbers for hopping sequence |
+| `dwell_ms` | u32 | 100 | Time to dwell on each channel before hopping (ms) |
+| `power_duty` | u8 | 100 | Power duty cycle percentage (10-100%) for battery life |
+| `wasm_max` | u8 | 4 | Max concurrent WASM modules (ADR-040) |
+| `wasm_verify` | u8 | 0 | Require Ed25519 signature for WASM uploads (0/1) |
+| `wasm_pubkey` | blob (32B) | zeros | Ed25519 public key for WASM signature verification |
+
+### Gap 2: No Read-Back
+
+There is no way to read the current NVS configuration from a device. Field operators must remember what was provisioned or reflash everything. This is especially problematic for multi-node meshes where each node has different TDM slots.
+
+### Gap 3: No Verification
+
+After flashing, there is no automated check that the device booted successfully with the new configuration. Operators must manually run a serial monitor and inspect logs.
+
+### Gap 4: No Config File Support
+
+Provisioning a 6-node mesh requires running the script 6 times with largely overlapping flags (same SSID, password, target IP) and only TDM slot varying. There is no way to define a mesh configuration in a file.
+
+### Gap 5: No Presets
+
+Common deployment scenarios (single-node basic, 3-node mesh, 6-node mesh with vitals) require operators to know which flags to combine. Named presets would lower the barrier to entry.
+
+### Gap 6: No Auto-Detect
+
+The `--port` flag is required even though the script could auto-detect connected ESP32-S3 devices via `esptool.py`.
+
+---
+
+## Decision
+
+Enhance `provision.py` with the following capabilities, implemented incrementally.
+
+### Phase 1: Complete NVS Coverage
+
+Add flags for all remaining firmware NVS keys:
+
+```
+--hop-count N          Channel hop count (1=no hop, default: 1)
+--channels 1,6,11      Comma-separated channel list for hopping
+--dwell-ms N           Dwell time per channel in ms (default: 100)
+--power-duty N         Power duty cycle 10-100% (default: 100)
+--wasm-max N           Max concurrent WASM modules 1-8 (default: 4)
+--wasm-verify          Require Ed25519 signature for WASM uploads
+--wasm-pubkey FILE     Path to Ed25519 public key file (32 bytes raw or PEM)
+```
+
+Validation:
+- `--channels` length must match `--hop-count`
+- `--power-duty` clamped to 10-100
+- `--wasm-pubkey` implies `--wasm-verify`
+
+### Phase 2: Config File and Mesh Provisioning
+
+Add `--config FILE` to load settings from a JSON or TOML file:
+
+```json
+{
+  "common": {
+    "ssid": "SensorNet",
+    "password": "secret",
+    "target_ip": "192.168.1.20",
+    "target_port": 5005,
+    "edge_tier": 2
+  },
+  "nodes": [
+    { "port": "COM7", "node_id": 0, "tdm_slot": 0 },
+    { "port": "COM8", "node_id": 1, "tdm_slot": 1 },
+    { "port": "COM9", "node_id": 2, "tdm_slot": 2 }
+  ]
+}
+```
+
+`--config mesh.json` provisions all listed nodes in sequence, computing `tdm_total` automatically from the `nodes` array length.
+
+### Phase 3: Presets
+
+Add `--preset NAME` for common deployment profiles:
+
+| Preset | What It Sets |
+|--------|-------------|
+| `basic` | Single node, edge_tier=0, no TDM, no hopping |
+| `vitals` | Single node, edge_tier=2, vital_int=1000, subk_count=32 |
+| `mesh-3` | 3-node TDM, edge_tier=1, hop_count=3, channels=1,6,11 |
+| `mesh-6-vitals` | 6-node TDM, edge_tier=2, hop_count=3, channels=1,6,11, vital_int=500 |
+
+Presets set defaults that can be overridden by explicit flags.
+
+### Phase 4: Read-Back and Verify
+
+Add `--read` to dump the current NVS configuration from a connected device:
+
+```bash
+python provision.py --port COM7 --read
+# Output:
+#   ssid:         SensorNet
+#   target_ip:    192.168.1.20
+#   tdm_slot:     0
+#   tdm_nodes:    3
+#   edge_tier:    2
+#   ...
+```
+
+Implementation: use `esptool.py read_flash` to read the NVS partition, then parse the NVS binary format to extract key-value pairs.
+
+Add `--verify` to provision and then confirm the device booted:
+
+```bash
+python provision.py --port COM7 --ssid "Net" --password "pass" --target-ip 192.168.1.20 --verify
+# After flash, opens serial monitor for 5 seconds
+# Checks for "CSI streaming active" log line
+# Reports PASS or FAIL
+```
+
+### Phase 5: Auto-Detect Port
+
+When `--port` is omitted, scan for connected ESP32-S3 devices:
+
+```bash
+python provision.py --ssid "Net" --password "pass" --target-ip 192.168.1.20
+# Auto-detected ESP32-S3 on COM7 (Silicon Labs CP210x)
+# Proceed? [Y/n]
+```
+
+Implementation: use `esptool.py` or `serial.tools.list_ports` to enumerate ports.
+
+---
+
+## Rationale
+
+### Why incremental phases?
+
+Phase 1 is a small diff that closes the NVS coverage gap immediately. Phases 2-5 add progressively more UX polish. Each phase is independently useful and can be shipped separately.
+
+### Why JSON config over YAML/TOML?
+
+JSON requires no additional Python dependencies (stdlib `json` module). TOML requires `tomllib` (Python 3.11+) or `tomli`. JSON is sufficient for this use case.
+
+### Why not a GUI?
+
+The target users are embedded developers and field operators who are already running `esptool` from the command line. A TUI/GUI would add dependencies and complexity for minimal benefit.
+
+---
+
+## Consequences
+
+### Positive
+
+- **Complete NVS coverage**: Every firmware-readable key can be set from the provisioning tool
+- **Mesh provisioning in one command**: `--config mesh.json` replaces 6 separate invocations
+- **Lower barrier to entry**: Presets eliminate the need to know which flags to combine
+- **Auditability**: `--read` lets operators inspect and verify deployed configurations
+- **Fewer mis-provisions**: `--verify` catches flashing failures before the operator walks away
+
+### Negative
+
+- **NVS binary parsing** (Phase 4) requires understanding the ESP-IDF NVS binary format, which is not officially documented as a stable API
+- **Auto-detect** (Phase 5) may produce false positives if other ESP32 variants are connected
+
+### Risks
+
+| Risk | Likelihood | Impact | Mitigation |
+|------|-----------|--------|------------|
+| NVS binary format changes in ESP-IDF v6 | Low | Medium | Pin to known ESP-IDF NVS page format; add format version check |
+| `--verify` serial parsing is fragile | Medium | Low | Match on stable log tag `[CSI_MAIN]`; timeout after 10s |
+| Config file credentials in plaintext | Medium | Medium | Document that config files should not be committed; add `.gitignore` pattern |
+
+---
+
+## Implementation Priority
+
+| Phase | Effort | Impact | Priority |
+|-------|--------|--------|----------|
+| Phase 1: Complete NVS coverage | Small (1 file, ~50 lines) | High — closes feature gap | P0 |
+| Phase 2: Config file + mesh | Medium (~100 lines) | High — biggest UX win | P1 |
+| Phase 3: Presets | Small (~40 lines) | Medium — convenience | P2 |
+| Phase 4: Read-back + verify | Medium (~150 lines) | Medium — debugging aid | P2 |
+| Phase 5: Auto-detect | Small (~30 lines) | Low — minor convenience | P3 |
+
+---
+
+## References
+
+- `firmware/esp32-csi-node/main/nvs_config.h` — NVS config struct (20 fields)
+- `firmware/esp32-csi-node/main/nvs_config.c` — NVS read logic (20 keys)
+- `firmware/esp32-csi-node/provision.py` — Current provisioning script (13 of 20 keys)
+- ADR-029: RuvSense multistatic sensing mode (TDM, channel hopping)
+- ADR-032: Multistatic mesh security hardening (mesh keys)
+- ADR-039: ESP32-S3 edge intelligence (edge tiers, vitals)
+- ADR-040: WASM programmable sensing (WASM modules, signature verification)
+- Issue #130: Provisioning script doesn't support TDM
@@ -27,6 +27,16 @@ static uint32_t s_sequence = 0;
 static uint32_t s_cb_count = 0;
 static uint32_t s_send_ok = 0;
 static uint32_t s_send_fail = 0;
+static uint32_t s_rate_skip = 0;
+
+/**
+ * Minimum interval between UDP sends in microseconds.
+ * CSI callbacks can fire hundreds of times per second in promiscuous mode.
+ * We cap the send rate to avoid exhausting lwIP packet buffers (ENOMEM).
+ * Default: 20 ms = 50 Hz max send rate.
+ */
+#define CSI_MIN_SEND_INTERVAL_US  (20 * 1000)
+static int64_t s_last_send_us = 0;

 /* ---- ADR-029: Channel-hop state ---- */

@@ -143,14 +153,23 @@ static void wifi_csi_callback(void *ctx, wifi_csi_info_t *info)
    size_t frame_len = csi_serialize_frame(info, frame_buf, sizeof(frame_buf));

    if (frame_len > 0) {
-        int ret = stream_sender_send(frame_buf, frame_len);
-        if (ret > 0) {
-            s_send_ok++;
-        } else {
-            s_send_fail++;
-            if (s_send_fail <= 5) {
-                ESP_LOGW(TAG, "sendto failed (fail #%lu)", (unsigned long)s_send_fail);
+        /* Rate-limit UDP sends to avoid ENOMEM from lwIP pbuf exhaustion.
+         * In promiscuous mode, CSI callbacks can fire 100-500+ times/sec.
+         * We only need 20-50 Hz for the sensing pipeline. */
+        int64_t now = esp_timer_get_time();
+        if ((now - s_last_send_us) >= CSI_MIN_SEND_INTERVAL_US) {
+            int ret = stream_sender_send(frame_buf, frame_len);
+            if (ret > 0) {
+                s_send_ok++;
+                s_last_send_us = now;
+            } else {
+                s_send_fail++;
+                if (s_send_fail <= 5) {
+                    ESP_LOGW(TAG, "sendto failed (fail #%lu)", (unsigned long)s_send_fail);
+                }
            }
+        } else {
+            s_rate_skip++;
        }
    }

@@ -9,6 +9,7 @@

 #include <string.h>
 #include "esp_log.h"
+#include "esp_timer.h"
 #include "lwip/sockets.h"
 #include "lwip/netdb.h"
 #include "sdkconfig.h"
@@ -18,6 +19,17 @@ static const char *TAG = "stream_sender";
 static int s_sock = -1;
 static struct sockaddr_in s_dest_addr;

+/**
+ * ENOMEM backoff state.
+ * When sendto fails with ENOMEM (errno 12), we suppress further sends for
+ * a cooldown period to let lwIP reclaim packet buffers.  Without this,
+ * rapid-fire CSI callbacks can exhaust the pbuf pool and crash the device.
+ */
+static int64_t s_backoff_until_us = 0;       /* esp_timer timestamp to resume */
+#define ENOMEM_COOLDOWN_MS  100              /* suppress sends for 100 ms */
+#define ENOMEM_LOG_INTERVAL 50               /* log every Nth suppressed send */
+static uint32_t s_enomem_suppressed = 0;
+
 static int sender_init_internal(const char *ip, uint16_t port)
 {
    s_sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
@@ -57,10 +69,37 @@ int stream_sender_send(const uint8_t *data, size_t len)
        return -1;
    }

+    /* ENOMEM backoff: if we recently exhausted lwIP buffers, skip sends
+     * until the cooldown expires.  This prevents the cascade of failed
+     * sendto calls that leads to a guru meditation crash. */
+    if (s_backoff_until_us > 0) {
+        int64_t now = esp_timer_get_time();
+        if (now < s_backoff_until_us) {
+            s_enomem_suppressed++;
+            if ((s_enomem_suppressed % ENOMEM_LOG_INTERVAL) == 1) {
+                ESP_LOGW(TAG, "sendto suppressed (ENOMEM backoff, %lu dropped)",
+                         (unsigned long)s_enomem_suppressed);
+            }
+            return -1;
+        }
+        /* Cooldown expired — resume sending */
+        ESP_LOGI(TAG, "ENOMEM backoff expired, resuming sends (%lu were suppressed)",
+                 (unsigned long)s_enomem_suppressed);
+        s_backoff_until_us = 0;
+        s_enomem_suppressed = 0;
+    }
+
    int sent = sendto(s_sock, data, len, 0,
                      (struct sockaddr *)&s_dest_addr, sizeof(s_dest_addr));
    if (sent < 0) {
-        ESP_LOGW(TAG, "sendto failed: errno %d", errno);
+        if (errno == ENOMEM) {
+            /* Start backoff to let lwIP reclaim buffers */
+            s_backoff_until_us = esp_timer_get_time() +
+                                 (int64_t)ENOMEM_COOLDOWN_MS * 1000;
+            ESP_LOGW(TAG, "sendto ENOMEM — backing off for %d ms", ENOMEM_COOLDOWN_MS);
+        } else {
+            ESP_LOGW(TAG, "sendto failed: errno %d", errno);
+        }
        return -1;
    }