feat(dhcps): Support for multiple DNS servers

Author: KonssnoK

components/esp_netif/lwip/esp_netif_lwip.c

@@ -1984,11 +1984,14 @@ static esp_err_t esp_netif_set_dns_info_api(esp_netif_api_msg_t *msg)
     if (esp_netif && esp_netif->flags & ESP_NETIF_DHCP_SERVER) {
 #if ESP_DHCPS
         // if DHCP server configured to set DNS in dhcps API
-        if (type != ESP_NETIF_DNS_MAIN) {
+        if (type >= ESP_NETIF_DNS_FALLBACK)
+        {
             ESP_LOGD(TAG, "set dns invalid type");
             return ESP_ERR_ESP_NETIF_INVALID_PARAMS;
-        } else {
-            dhcps_dns_setserver(esp_netif->dhcps, &lwip_ip);
+        }
+        else
+        {
+            dhcps_dns_setserver(esp_netif->dhcps, &lwip_ip, (dns_type_t)type);
         }
 #else
         LOG_NETIF_DISABLED_AND_DO("DHCP Server", return ESP_ERR_NOT_SUPPORTED);
@@ -2047,7 +2050,7 @@ static esp_err_t esp_netif_get_dns_info_api(esp_netif_api_msg_t *msg)
     if (esp_netif && esp_netif->flags & ESP_NETIF_DHCP_SERVER) {
 #if ESP_DHCPS
         ip4_addr_t dns_ip;
-        dhcps_dns_getserver(esp_netif->dhcps, &dns_ip);
+        dhcps_dns_getserver(esp_netif->dhcps, &dns_ip, (dns_type_t)type);
         memcpy(&dns->ip.u_addr.ip4, &dns_ip, sizeof(ip4_addr_t));
         dns->ip.type = ESP_IPADDR_TYPE_V4;
 #else

components/lwip/apps/dhcpserver/dhcpserver.c

@@ -126,7 +126,7 @@ struct dhcps_t {
     struct netif *dhcps_netif;
     ip4_addr_t broadcast_dhcps;
     ip4_addr_t server_address;
-    ip4_addr_t dns_server;
+    ip4_addr_t dns_server[DNS_TYPE_MAX];
     ip4_addr_t client_address;
     ip4_addr_t client_address_plus;
     ip4_addr_t dhcps_mask;
@@ -155,7 +155,11 @@ dhcps_t *dhcps_new(void)
         return NULL;
     }
     dhcps->dhcps_netif = NULL;
-    dhcps->dns_server.addr = 0;
+
+    for (int i = 0; i < DNS_TYPE_MAX; i++)
+    {
+        dhcps->dns_server[i].addr = 0;
+    }
 #ifdef USE_CLASS_B_NET
     dhcps->dhcps_mask.addr = PP_HTONL(LWIP_MAKEU32(255, 240, 0, 0));
 #else
@@ -454,16 +458,31 @@ static u8_t *add_offer_options(dhcps_t *dhcps, u8_t *optptr)
         }
     }
 
+    // In order of preference
+    *optptr++ = DHCP_OPTION_DNS_SERVER;
     if (dhcps_dns_enabled(dhcps->dhcps_dns)) {
-        *optptr++ = DHCP_OPTION_DNS_SERVER;
-        *optptr++ = 4;
-        *optptr++ = ip4_addr1(&dhcps->dns_server);
-        *optptr++ = ip4_addr2(&dhcps->dns_server);
-        *optptr++ = ip4_addr3(&dhcps->dns_server);
-        *optptr++ = ip4_addr4(&dhcps->dns_server);
+        uint8_t size = 4;
+
+        if (dhcps->dns_server[DNS_TYPE_BACKUP].addr)
+        {
+            size += 4;
+        }
+        *optptr++ = size;
+
+        *optptr++ = ip4_addr1(&dhcps->dns_server[DNS_TYPE_MAIN]);
+        *optptr++ = ip4_addr2(&dhcps->dns_server[DNS_TYPE_MAIN]);
+        *optptr++ = ip4_addr3(&dhcps->dns_server[DNS_TYPE_MAIN]);
+        *optptr++ = ip4_addr4(&dhcps->dns_server[DNS_TYPE_MAIN]);
+
+        if (dhcps->dns_server[DNS_TYPE_BACKUP].addr)
+        {
+            *optptr++ = ip4_addr1(&dhcps->dns_server[DNS_TYPE_BACKUP]);
+            *optptr++ = ip4_addr2(&dhcps->dns_server[DNS_TYPE_BACKUP]);
+            *optptr++ = ip4_addr3(&dhcps->dns_server[DNS_TYPE_BACKUP]);
+            *optptr++ = ip4_addr4(&dhcps->dns_server[DNS_TYPE_BACKUP]);
+        }
 #ifdef CONFIG_LWIP_DHCPS_ADD_DNS
     }else {
-        *optptr++ = DHCP_OPTION_DNS_SERVER;
         *optptr++ = 4;
         *optptr++ = ip4_addr1(&ipadd);
         *optptr++ = ip4_addr2(&ipadd);
@@ -1535,31 +1554,33 @@ bool dhcp_search_ip_on_mac(dhcps_t *dhcps, u8_t *mac, ip4_addr_t *ip)
  * FunctionName : dhcps_dns_setserver
  * Description  : set DNS server address for dhcpserver
  * Parameters   : dnsserver -- The DNS server address
+ *                type      -- The DNS type
  * Returns      : ERR_ARG if invalid handle, ERR_OK on success
 *******************************************************************************/
-err_t dhcps_dns_setserver(dhcps_t *dhcps, const ip_addr_t *dnsserver)
+err_t dhcps_dns_setserver(dhcps_t *dhcps, const ip_addr_t *dnsserver, dns_type_t type)
 {
     if (dhcps == NULL) {
         return ERR_ARG;
     }
     if (dnsserver != NULL) {
-        dhcps->dns_server = *(ip_2_ip4(dnsserver));
+        dhcps->dns_server[type] = *(ip_2_ip4(dnsserver));
     } else {
-        dhcps->dns_server = *(ip_2_ip4(IP_ADDR_ANY));
+        dhcps->dns_server[type] = *(ip_2_ip4(IP_ADDR_ANY));
     }
     return ERR_OK;
 }
 
 /******************************************************************************
  * FunctionName : dhcps_dns_getserver
  * Description  : get DNS server address for dhcpserver
- * Parameters   : none
- * Returns      : ip4_addr_t
+ * Parameters   : dnsserver -- The DNS server address
+ *                type      -- The DNS type
+ * Returns      : ERR_ARG if invalid handle, ERR_OK on success
 *******************************************************************************/
-err_t dhcps_dns_getserver(dhcps_t *dhcps, ip4_addr_t *dnsserver)
+err_t dhcps_dns_getserver(dhcps_t *dhcps, ip4_addr_t *dnsserver, dns_type_t type)
 {
     if (dhcps) {
-        *dnsserver = dhcps->dns_server;
+        *dnsserver = dhcps->dns_server[type];
         return ERR_OK;
     }
     return ERR_ARG;

components/lwip/include/apps/dhcpserver/dhcpserver.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -47,6 +47,13 @@ enum dhcps_offer_option{
 	OFFER_END
 };
 
+typedef enum
+{
+    DNS_TYPE_MAIN = 0, /**< DNS main server address*/
+    DNS_TYPE_BACKUP,   /**< DNS backup server address (Wi-Fi STA and Ethernet only) */
+    DNS_TYPE_MAX
+} dns_type_t;
+
 /** @brief DHCP server's description of compile time configuration values in dhcpserver.c
  *
  * - DHCPS_DEBUG: Prints very detailed debug messages if set to 1, hardcoded to 0
@@ -164,17 +171,19 @@ bool dhcp_search_ip_on_mac(dhcps_t *dhcps, u8_t *mac, ip4_addr_t *ip);
  * @brief Sets DNS server address for the DHCP server
  * @param dhcps Pointer to the DHCP handle
  * @param dnsserver Address of the DNS server
+ * @param type Type of the DNS server
  * @return ERR_ARG if invalid handle, ERR_OK on success
  */
-err_t dhcps_dns_setserver(dhcps_t *dhcps, const ip_addr_t *dnsserver);
+err_t dhcps_dns_setserver(dhcps_t *dhcps, const ip_addr_t *dnsserver, dns_type_t type);
 
 /**
  * @brief Gets DNS server associated with this DHCP server
  * @param dhcps Pointer to the DHCP handle
  * @param dnsserver Address of the DNS server
+ * @param type Type of the DNS server
  * @return ERR_ARG if invalid handle, ERR_OK on success
  */
-err_t dhcps_dns_getserver(dhcps_t *dhcps, ip4_addr_t *dnsserver);
+err_t dhcps_dns_getserver(dhcps_t *dhcps, ip4_addr_t *dnsserver, dns_type_t type);
 
 /**
  * @brief Sets callback on assigning an IP to the connected client