esp-firewall/ESPTest/include/myhook.c

#include "lwip/netif.h"
#include "lwip/pbuf.h"
#include "esp_log.h"

int lwip_hook_ip4_input(struct pbuf *pbuf, struct netif *input_netif)
{
    ESP_LOGI("HOOK", "Testing...");
    return 0; // we don't consume the packet
}