dns: Support for fallback DNS server

2.1.3-esp: 771421c8 dns: Support for fallback DNS server

contrib/examples/example_app/lwipopts.h

@@ -325,5 +325,8 @@ void lwip_example_app_platform_assert(const char *msg, int line, const char *fil
 
 /* ESP options */
 #define ESP_LWIP LWIP_NETCONN_FULLDUPLEX
+#define ESP_LWIP_IGMP_TIMERS_ONDEMAND ESP_LWIP
+#define ESP_LWIP_MLD6_TIMERS_ONDEMAND ESP_LWIP
+#define ESP_DNS ESP_LWIP
 
 #endif /* LWIP_LWIPOPTS_H */

src/core/dns.c

@@ -96,6 +96,9 @@
 #include "lwip/prot/dns.h"
 
 #include <string.h>
+#if ESP_DNS
+#include <stdbool.h>
+#endif
 
 /** Random generator function to create random TXIDs and source ports for queries */
 #ifndef DNS_RAND_TXID
@@ -314,12 +317,25 @@ const ip_addr_t dns_mquery_v6group = DNS_MQUERY_IPV6_GROUP_INIT;
 void
 dns_init(void)
 {
+#if ESP_DNS
+#ifdef FALLBACK_DNS_SERVER_ADDRESS
+  /* initialize fallback dns DNS server address */
+  ip_addr_t dnsserver;
+  FALLBACK_DNS_SERVER_ADDRESS(&dnsserver);
+  dnsserver.type = IPADDR_TYPE_V4;
+  dns_setserver(DNS_FALLBACK_SERVER_INDEX, &dnsserver);
+#endif /* FALLBACK_DNS_SERVER_ADDRESS */
+
+#else
+
+
 #ifdef DNS_SERVER_ADDRESS
   /* initialize default DNS server address */
   ip_addr_t dnsserver;
   DNS_SERVER_ADDRESS(&dnsserver);
   dns_setserver(0, &dnsserver);
 #endif /* DNS_SERVER_ADDRESS */
+#endif
 
   LWIP_ASSERT("sanity check SIZEOF_DNS_QUERY",
               sizeof(struct dns_query) == SIZEOF_DNS_QUERY);
@@ -1078,7 +1094,11 @@ dns_check_entry(u8_t i)
       entry->server_idx = 0;
       entry->tmr = 1;
       entry->retries = 0;
-
+#if ESP_DNS
+      while((entry->server_idx < DNS_MAX_SERVERS) && ip_addr_isany_val(dns_servers[entry->server_idx])) {
+        entry->server_idx++;
+      }
+#endif
       /* send DNS packet for this entry */
       err = dns_send(i);
       if (err != ERR_OK) {
@@ -1089,6 +1109,12 @@ dns_check_entry(u8_t i)
     case DNS_STATE_ASKING:
       if (--entry->tmr == 0) {
         if (++entry->retries == DNS_MAX_RETRIES) {
+#if ESP_DNS
+          /* skip DNS servers with zero address */
+        while ((entry->server_idx + 1 < DNS_MAX_SERVERS) && ip_addr_isany_val(dns_servers[entry->server_idx + 1])) {
+            entry->server_idx++;
+          }
+#endif
           if (dns_backupserver_available(entry)
 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
               && !entry->is_mdns
@@ -1552,6 +1578,19 @@ dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback foun
   return dns_gethostbyname_addrtype(hostname, addr, found, callback_arg, LWIP_DNS_ADDRTYPE_DEFAULT);
 }
 
+#if ESP_DNS
+static bool dns_server_is_set (void)
+{
+  int i = 0;
+  for (i = 0;i < DNS_MAX_SERVERS; i++) {
+    if (!ip_addr_isany_val(dns_servers[i])) {
+      return true;
+    }
+  }
+  return false;
+}
+#endif
+
 /**
  * @ingroup dns
  * Like dns_gethostbyname, but returned address type can be controlled:
@@ -1644,7 +1683,11 @@ dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr, dns_found_call
 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
   {
     /* prevent calling found callback if no server is set, return error instead */
+#if ESP_DNS
+    if (dns_server_is_set() == false) {
+#else
     if (ip_addr_isany_val(dns_servers[0])) {
+#endif
       return ERR_VAL;
     }
   }

src/core/ipv4/dhcp.c

@@ -744,6 +744,11 @@ dhcp_handle_ack(struct netif *netif, struct dhcp_msg *msg_in)
   /* DNS servers */
   for (n = 0; (n < LWIP_DHCP_PROVIDE_DNS_SERVERS) && dhcp_option_given(dhcp, DHCP_OPTION_IDX_DNS_SERVER + n); n++) {
     ip_addr_t dns_addr;
+#if ESP_DNS
+    if (n == DNS_FALLBACK_SERVER_INDEX) {
+        continue;
+    }
+#endif
     ip_addr_set_ip4_u32_val(dns_addr, lwip_htonl(dhcp_get_option_value(dhcp, DHCP_OPTION_IDX_DNS_SERVER + n)));
     dns_setserver(n, &dns_addr);
   }

src/include/lwip/dns.h

@@ -111,7 +111,9 @@ err_t            dns_gethostbyname(const char *hostname, ip_addr_t *addr,
 err_t            dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr,
                                    dns_found_callback found, void *callback_arg,
                                    u8_t dns_addrtype);
-
+#if ESP_DNS
+void             dns_clear_servers(bool keep_fallback);
+#endif
 
 #if DNS_LOCAL_HOSTLIST
 size_t         dns_local_iterate(dns_found_callback iterator_fn, void *iterator_arg);

test/unit/lwipopts.h

@@ -93,6 +93,7 @@
 
 /* Enable Espressif specific options */
 #ifdef ESP_LWIP
+#define ESP_DNS                          1
 #define LWIP_DHCP_ENABLE_VENDOR_SPEC_IDS 1
 #define LWIP_DHCP_ENABLE_CLIENT_ID 1
 #define LWIP_DHCP_ENABLE_MTU_UPDATE 1
@@ -161,9 +162,11 @@ u32_t esp_random(void);
 #endif /* ESP_TEST_DEBUG */
 #define ESP_LWIP_IGMP_TIMERS_ONDEMAND           1
 #define ESP_LWIP_MLD6_TIMERS_ONDEMAND           1
+#define DNS_FALLBACK_SERVER_INDEX       (DNS_MAX_SERVERS - 1)
 
 #else
 #define ESP_LWIP                                0
+#define ESP_DNS                                 0
 #define ESP_LWIP_IGMP_TIMERS_ONDEMAND           0
 #define ESP_LWIP_MLD6_TIMERS_ONDEMAND           0