diff --git a/examples/esp_netif/multiple_netifs/README.md b/examples/esp_netif/multiple_netifs/README.md
index 09ba1a1b9e..e0506d6315 100644
--- a/examples/esp_netif/multiple_netifs/README.md
+++ b/examples/esp_netif/multiple_netifs/README.md
@@ -19,6 +19,14 @@ This example demonstrates working with multiple different interfaces with differ
* It tries to reconfigure DNS server if host name resolution fails
* It tries to manually change the default interface if connection fails
+### Handling DNS server across interfaces
+
+This example also demonstrates how DNS servers could be handled on network interface level, as lwIP used global DNS server information.
+
+All network interfaces store their DNS info upon acquiring an IP in the internal structure (in the application code) and the DNS servers are restored if host name resolution fails.
+
+This functionality is handled in IDF (supported from v5.3) automatically if `CONFIG_ESP_NETIF_SET_DNS_PER_DEFAULT_NETIF` is enabled, the DNS server info keeps updating per network interface in IDF layers. This examples uses the IDF functionality if `CONFIG_ESP_NETIF_SET_DNS_PER_DEFAULT_NETIF=1`.
+
### Hardware Required
To run this example, it's recommended that you have an official ESP32 Ethernet development board - [ESP32-Ethernet-Kit](https://docs.espressif.com/projects/esp-idf/en/latest/hw-reference/get-started-ethernet-kit.html).
diff --git a/examples/esp_netif/multiple_netifs/main/Kconfig.projbuild b/examples/esp_netif/multiple_netifs/main/Kconfig.projbuild
index c038535a69..3929fa20ea 100644
--- a/examples/esp_netif/multiple_netifs/main/Kconfig.projbuild
+++ b/examples/esp_netif/multiple_netifs/main/Kconfig.projbuild
@@ -54,4 +54,14 @@ menu "Example Configuration"
bool "Using simple UART-PPP driver"
endchoice
+ config EXAMPLE_DEMONSTRATE_DNS_CLEAR_CACHE
+ bool "Run DNS clear cache"
+ default n
+ help
+ This example will cleanup the DNS cache
+ every iteration of the demo network operation.
+ This forces the TCP/IP stack to always resolve DNS names,
+ thus exercising potentially invalid DNS configuration.
+ Set this to "y" for testing, but keep as "n" for production.
+
endmenu
diff --git a/examples/esp_netif/multiple_netifs/main/ethernet_connect.c b/examples/esp_netif/multiple_netifs/main/ethernet_connect.c
index 53ec398f56..dc2537e08b 100644
--- a/examples/esp_netif/multiple_netifs/main/ethernet_connect.c
+++ b/examples/esp_netif/multiple_netifs/main/ethernet_connect.c
@@ -95,7 +95,7 @@ static void eth_destroy(iface_info_t *info)
free(eth_info);
}
-iface_info_t *eth_init(int prio)
+iface_info_t *example_eth_init(int prio)
{
struct eth_info_t *eth_info = malloc(sizeof(struct eth_info_t));
assert(eth_info);
@@ -124,7 +124,7 @@ iface_info_t *eth_init(int prio)
eth_info->parent.netif = esp_netif_new(&cfg);
eth_info->glue = esp_eth_new_netif_glue(eth_info->eth_handle);
// Attach Ethernet driver to TCP/IP stack
- ESP_ERROR_CHECK(esp_netif_attach(eth_info->parent.netif, eth_info->glue ));
+ ESP_ERROR_CHECK(esp_netif_attach(eth_info->parent.netif, eth_info->glue));
// Register user defined event handers
ESP_ERROR_CHECK(esp_event_handler_register(ETH_EVENT, ESP_EVENT_ANY_ID, ð_event_handler, eth_info));
diff --git a/examples/esp_netif/multiple_netifs/main/multi_netif_main.c b/examples/esp_netif/multiple_netifs/main/multi_netif_main.c
index 26f8dab443..415e9707c6 100644
--- a/examples/esp_netif/multiple_netifs/main/multi_netif_main.c
+++ b/examples/esp_netif/multiple_netifs/main/multi_netif_main.c
@@ -1,5 +1,5 @@
/*
- * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2023-2024 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Unlicense OR CC0-1.0
*/
@@ -23,9 +23,9 @@
#include "nvs_flash.h"
#include "iface_info.h"
-iface_info_t *eth_init(int prio);
-iface_info_t *wifi_init(int prio);
-iface_info_t *ppp_init(int prio);
+iface_info_t *example_eth_init(int prio);
+iface_info_t *example_wifi_init(int prio);
+iface_info_t *example_ppp_init(int prio);
esp_err_t check_connectivity(const char *host);
#define HOST "www.espressif.com"
@@ -69,14 +69,18 @@ void app_main(void)
// all interfaces
iface_info_t *ifaces[] = {
- eth_init(ETH_PRIO),
- wifi_init(WIFI_PRIO),
- ppp_init(PPP_PRIO),
+ example_eth_init(ETH_PRIO),
+ example_wifi_init(WIFI_PRIO),
+ example_ppp_init(PPP_PRIO),
};
size_t num_of_ifaces = sizeof(ifaces) / sizeof(ifaces[0]);
while (true) {
+#ifdef CONFIG_EXAMPLE_DEMONSTRATE_DNS_CLEAR_CACHE
+ // For demonstration purposes we clear DNS table every iteration to exercise
+ // a condition of DNS servers being misconfigured
dns_clear_cache();
+#endif
vTaskDelay(pdMS_TO_TICKS(2000));
ssize_t i = get_default(ifaces, num_of_ifaces);
if (i == -1) { // default netif is NULL, probably all interfaces are down -> retry
@@ -91,7 +95,9 @@ void app_main(void)
continue;
}
if (connect_status == ESP_ERR_NOT_FOUND) {
+#ifndef CONFIG_ESP_NETIF_SET_DNS_PER_DEFAULT_NETIF
// set the default DNS info to global DNS server list
+ // manually if DNS_PER_DEFAULT_NETIF if OFF or not-supported
for (int j = 0; j < 2; ++j) {
esp_netif_dns_info_t dns_info;
esp_netif_get_dns_info(ifaces[i]->netif, j, &dns_info);
@@ -102,6 +108,12 @@ void app_main(void)
ESP_LOGI(TAG, "Reconfigured DNS%i=" IPSTR, j, IP2STR(&ifaces[i]->dns[j].ip.u_addr.ip4));
}
}
+#else
+ // simulate that the (default) netif is brought UP
+ // this is only needed, since we explicitly clear DNS servers every iteration using dns_clear_cache()
+ // (for demonstration purpose only, won't be needed in your project, unless you delete DNS info for some reasons)
+ esp_netif_action_connected(ifaces[i]->netif, NULL, 0, NULL);
+#endif
}
if (connect_status == ESP_FAIL) {
ESP_LOGE(TAG, "No connection via the default netif!");
diff --git a/examples/esp_netif/multiple_netifs/main/ppp_connect.c b/examples/esp_netif/multiple_netifs/main/ppp_connect.c
index b1f2dcf05d..d7740510ad 100644
--- a/examples/esp_netif/multiple_netifs/main/ppp_connect.c
+++ b/examples/esp_netif/multiple_netifs/main/ppp_connect.c
@@ -85,7 +85,7 @@ static void ppp_destroy(iface_info_t *info)
free(info);
}
-iface_info_t *init_ppp(int prio)
+iface_info_t *example_ppp_init(int prio)
{
struct ppp_info_t *ppp_info = calloc(1, sizeof(struct ppp_info_t));
assert(ppp_info);
diff --git a/examples/esp_netif/multiple_netifs/main/wifi_connect.c b/examples/esp_netif/multiple_netifs/main/wifi_connect.c
index 523c773568..5723051301 100644
--- a/examples/esp_netif/multiple_netifs/main/wifi_connect.c
+++ b/examples/esp_netif/multiple_netifs/main/wifi_connect.c
@@ -75,7 +75,7 @@ static void wifi_destroy(iface_info_t *info)
free(info);
}
-iface_info_t *wifi_init(int prio)
+iface_info_t *example_wifi_init(int prio)
{
struct iface_info_t *wifi_info = malloc(sizeof(iface_info_t));
assert(wifi_info);
@@ -100,9 +100,9 @@ iface_info_t *wifi_init(int prio)
.password = CONFIG_ESP_WIFI_PASSWORD,
},
};
- ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA) );
- ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config) );
- ESP_ERROR_CHECK(esp_wifi_start() );
+ ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
+ ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config));
+ ESP_ERROR_CHECK(esp_wifi_start());
ESP_LOGI(TAG, "wifi_init_sta finished.");
diff --git a/examples/esp_netif/multiple_netifs/sdkconfig.defaults b/examples/esp_netif/multiple_netifs/sdkconfig.defaults
index 3c08a9a30d..84966ec347 100644
--- a/examples/esp_netif/multiple_netifs/sdkconfig.defaults
+++ b/examples/esp_netif/multiple_netifs/sdkconfig.defaults
@@ -1,2 +1,5 @@
+# You can use CONFIG_ESP_NETIF_SET_DNS_PER_DEFAULT_NETIF
+# to perform DNS server updates automatically in esp_netif layers
+# instead of manually as it is demonstrated in this example
CONFIG_LWIP_PPP_SUPPORT=y
CONFIG_LWIP_PPP_NOTIFY_PHASE_SUPPORT=y