ESP32 Forum

Posted: **Sun Sep 12, 2021 10:35 am**

Mainly based on https://github.com/espressif/esp-idf/issues/6261, I tried to implement my LWIP_HOOK_IP4_INPUT as follows:

CMakeLists.txt:

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FILE(GLOB_RECURSE app_sources ${CMAKE_SOURCE_DIR}/src/*)

idf_component_register(SRCS ${app_sources})
target_compile_definitions(${lwip} PRIVATE "-DESP_IDF_LWIP_HOOK_FILENAME=\"httpd/lwip_hooks.h\"")

(also tried "lwipcode" and "${COMPONENT_TARGET}" instead of "${lwip} – the latter does build but does not work as expected)

httpd/lwip_hooks.h:

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#pragma once

#define LWIP_HOOK_IP4_INPUT lwip_hook_ip4_input

httpd/myhook.h:

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#pragma once

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

#ifdef __cplusplus
extern "C" {
#endif

int IRAM_ATTR lwip_hook_ip4_input(struct pbuf *pbuf, struct netif *input_netif);

#ifdef __cplusplus
}
#endif

httpd/myhook.c:

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#include "driver/gpio.h"
#include "lwip/netif.h"
#include "lwip/pbuf.h"

int IRAM_ATTR lwip_hook_ip4_input(struct pbuf *pbuf, struct netif *input_netif) {
    gpio_set_level(GPIO_NUM_2, 1);
    return 0; // we don't consume the packet
}

What is the correct target to use in target_compile_definitions? Anything wrong with the rest of my incantation?

Running ESP-IDF 4.3.0 under platform.io.

Would be amazing to have an ESP-IDF example for using the hooks feature.

Sincerely,
Steffen

Posted: **Wed Sep 22, 2021 7:43 am**

Hi Steffen

The ${lwip} in your Makefiles is a CMake variable which refers to lwip as a static library, IDF's component.
This is how you can initialise it:

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idf_component_get_property(lwip lwip COMPONENT_LiB)

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