Improve DNS server selection logic

Add `.dns` to the ip_info struct

Update DNS server according to highest priority active connection: Ethernet, WiFi, PPP.

Signed-off-by: Deomid "rojer" Ryabkov <[email protected]>

Author: rojer

include/mgos_net.h

@@ -23,8 +23,7 @@
  * is lost, established, etc.
  */
 
-#ifndef CS_FW_INCLUDE_MGOS_NET_H_
-#define CS_FW_INCLUDE_MGOS_NET_H_
+#pragma once
 
 #include <stdbool.h>
 
@@ -35,7 +34,7 @@
 
 #ifdef __cplusplus
 extern "C" {
-#endif /* __cplusplus */
+#endif
 
 /*
  * Event group which should be given to `mgos_event_add_group_handler()`
@@ -85,6 +84,7 @@ struct mgos_net_ip_info {
   struct sockaddr_in ip;
   struct sockaddr_in netmask;
   struct sockaddr_in gw;
+  struct sockaddr_in dns;
 };
 
 struct mgos_net_event_data {
@@ -118,14 +118,6 @@ bool mgos_net_str_to_ip(const char *ips, struct sockaddr_in *sin);
  */
 bool mgos_net_str_to_ip_n(const struct mg_str ips, struct sockaddr_in *sin);
 
-/*
- * Returns nameserver address. The caller should `free()` it. Returns NULL
- * in case of no DNS.
- */
-char *mgos_get_nameserver(void);
-
 #ifdef __cplusplus
 }
-#endif /* __cplusplus */
-
-#endif /* CS_FW_INCLUDE_MGOS_NET_H_ */
+#endif

platforms/esp32/sdk.version

@@ -1 +1 @@
-docker.io/mgos/esp32-build:4.2-r1
+docker.io/mgos/esp32-build:4.2-r2

src/mgos_net.c

@@ -38,6 +38,8 @@ struct net_ev_info {
   enum mgos_net_event ev;
 };
 
+static void mgos_update_nameserver(void);
+
 static const char *get_if_name(enum mgos_net_if_type if_type, int if_instance) {
   const char *name = "";
   switch (if_type) {
@@ -80,6 +82,7 @@ static void mgos_net_on_change_cb(void *arg) {
   switch (ei->ev) {
     case MGOS_NET_EV_DISCONNECTED: {
       LOG(LL_INFO, ("%s: disconnected", if_name));
+      mgos_update_nameserver();
       break;
     }
     case MGOS_NET_EV_CONNECTING: {
@@ -92,17 +95,13 @@ static void mgos_net_on_change_cb(void *arg) {
     }
     case MGOS_NET_EV_IP_ACQUIRED: {
       if (mgos_net_get_ip_info(ei->if_type, ei->if_instance, &evd.ip_info)) {
-        char ip[16], gw[16];
-        char *nameserver = mgos_get_nameserver();
-        memset(ip, 0, sizeof(ip));
-        memset(gw, 0, sizeof(gw));
+        char ip[16], gw[16], dns[16];
         mgos_net_ip_to_str(&evd.ip_info.ip, ip);
         mgos_net_ip_to_str(&evd.ip_info.gw, gw);
-        LOG(LL_INFO, ("%s: ready, IP %s, GW %s, DNS %s", if_name, ip, gw,
-                      nameserver ? nameserver : "default"));
-        mg_set_nameserver(mgos_get_mgr(), nameserver);
-        free(nameserver);
+        mgos_net_ip_to_str(&evd.ip_info.dns, dns);
+        LOG(LL_INFO, ("%s: ready, IP %s, GW %s, DNS %s", if_name, ip, gw, dns));
       }
+      mgos_update_nameserver();
       break;
     }
   }
@@ -179,18 +178,32 @@ bool mgos_net_str_to_ip_n(struct mg_str ips, struct sockaddr_in *sin) {
   return res;
 }
 
-char *mgos_get_nameserver() {
-#ifdef MGOS_HAVE_WIFI
-  char *dns = NULL;
-  if (mgos_sys_config_get_wifi_sta_nameserver() != NULL) {
-    dns = strdup(mgos_sys_config_get_wifi_sta_nameserver());
-  } else {
-    dns = mgos_wifi_get_sta_default_dns();
+static void mgos_update_nameserver(void) {
+  char nameserver[16];
+  struct mgos_net_ip_info ip_info;
+  memset(&ip_info, 0, sizeof(ip_info));
+  if (mgos_net_get_ip_info(MGOS_NET_IF_TYPE_ETHERNET, 0, &ip_info) &&
+      ip_info.ip.sin_addr.s_addr != 0 && ip_info.dns.sin_addr.s_addr != 0) {
+    goto out;
   }
-  return dns;
-#else
-  return NULL;
-#endif
+  memset(&ip_info, 0, sizeof(ip_info));
+  if (mgos_net_get_ip_info(MGOS_NET_IF_TYPE_WIFI, 0, &ip_info) &&
+      ip_info.ip.sin_addr.s_addr != 0 && ip_info.dns.sin_addr.s_addr != 0) {
+    goto out;
+  }
+  memset(&ip_info, 0, sizeof(ip_info));
+  if (mgos_net_get_ip_info(MGOS_NET_IF_TYPE_PPP, 0, &ip_info) &&
+      ip_info.ip.sin_addr.s_addr != 0 && ip_info.dns.sin_addr.s_addr != 0) {
+    goto out;
+  }
+  mgos_net_str_to_ip(MGOS_DEFAULT_NAMESERVER, &ip_info.dns);
+out:
+  mgos_net_ip_to_str(&ip_info.dns, nameserver);
+  struct mg_mgr *mgr = mgos_get_mgr();
+  if (mgr->nameserver != NULL && strcmp(mgr->nameserver, nameserver) == 0)
+    return;
+  LOG(LL_DEBUG, ("Setting DNS server to %s", nameserver));
+  mg_set_nameserver(mgr, nameserver);
 }
 
 enum mgos_init_result mgos_net_init(void) {

tools/docker/esp32/Dockerfile-esp32-build

@@ -41,6 +41,9 @@ RUN git clone -j 8 --branch $DOCKER_TAG --depth 1 --recursive --shallow-submodul
 RUN cd /opt/Espressif/esp-idf && git tag v$DOCKER_TAG
 ENV IDF_PATH=/opt/Espressif/esp-idf
 
+ADD lwip_dns.patch /opt/Espressif/esp-idf/components/lwip/lwip
+RUN cd /opt/Espressif/esp-idf/components/lwip/lwip && patch -p 1 < lwip_dns.patch
+
 # Pre-build configuration tools
 RUN cd $IDF_PATH/tools/kconfig && make conf-idf
 

tools/docker/esp32/lwip_dns.patch

@@ -0,0 +1,54 @@
+diff --git a/src/core/ipv4/dhcp.c b/src/core/ipv4/dhcp.c
+index b519ae909..96de64423 100644
+--- a/src/core/ipv4/dhcp.c
++++ b/src/core/ipv4/dhcp.c
+@@ -703,6 +703,10 @@ dhcp_handle_ack(struct netif *netif, struct dhcp_msg *msg_in)
+     dns_setserver(n, &dns_addr);
+   }
+ #endif /* LWIP_DHCP_PROVIDE_DNS_SERVERS */
++  ip4_addr_set_zero(&dhcp->offered_dns_addr);
++  if (dhcp_option_given(dhcp, DHCP_OPTION_IDX_DNS_SERVER)) {
++    ip4_addr_set_u32(&dhcp->offered_dns_addr, lwip_htonl(dhcp_get_option_value(dhcp, DHCP_OPTION_IDX_DNS_SERVER)));
++  }
+ }
+ 
+ /**
+diff --git a/src/include/lwip/dhcp.h b/src/include/lwip/dhcp.h
+index 962cc2ee2..752db1f67 100644
+--- a/src/include/lwip/dhcp.h
++++ b/src/include/lwip/dhcp.h
+@@ -103,6 +103,7 @@ struct dhcp
+   ip4_addr_t offered_ip_addr;
+   ip4_addr_t offered_sn_mask;
+   ip4_addr_t offered_gw_addr;
++  ip4_addr_t offered_dns_addr;
+ 
+   u32_t offered_t0_lease; /* lease period (in seconds) */
+   u32_t offered_t1_renew; /* recommended renew time (usually 50% of lease period) */
+diff --git a/src/include/netif/ppp/ppp.h b/src/include/netif/ppp/ppp.h
+index 3d73c3657..2f1e1e9e3 100644
+--- a/src/include/netif/ppp/ppp.h
++++ b/src/include/netif/ppp/ppp.h
+@@ -421,6 +421,8 @@ struct ppp_pcb_s {
+   ipv6cp_options ipv6cp_allowoptions; /* Options we allow peer to request */
+   ipv6cp_options ipv6cp_hisoptions;   /* Options that we ack'd */
+ #endif /* PPP_IPV6_SUPPORT */
++
++  u32_t dns_server;
+ };
+ 
+ /************************
+diff --git a/src/netif/ppp/ipcp.c b/src/netif/ppp/ipcp.c
+index b7c766eb0..2d33f97c2 100644
+--- a/src/netif/ppp/ipcp.c
++++ b/src/netif/ppp/ipcp.c
+@@ -1930,7 +1930,9 @@ static void ipcp_up(fsm *f) {
+     if (go->dnsaddr[1])
+ 	script_setenv("DNS2", ip_ntoa(go->dnsaddr[1]), 0);
+ #endif /* UNUSED */
++    pcb->dns_server = 0;
+     if (pcb->settings.usepeerdns && (go->dnsaddr[0] || go->dnsaddr[1])) {
++	pcb->dns_server = go->dnsaddr[0];
+ 	sdns(pcb, go->dnsaddr[0], go->dnsaddr[1]);
+ #if 0 /* UNUSED */
+ 	script_setenv("USEPEERDNS", "1", 0);