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fix: rate-limit CSI sends and add ENOMEM backoff to prevent crash (#132)

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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
This commit is contained in:
rUv
2026-03-03 16:00:40 -05:00
committed by GitHub
parent b544545cb0
commit ce171696b2
2 changed files with 66 additions and 8 deletions
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firmware/esp32-csi-node/main/csi_collector.c
+26 -7
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@@ -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++;
}
}