Network.erl fix sta_rssi() crash when not started.

Calling network:sta_rssi() would crash if network was not started. And just if network_port was started but not connected yet.

Handle this and return error tuple, and added tests for both scenarios.

Signed-off-by: Peter M <petermm@gmail.com>

Author: petermm

libs/eavmlib/src/network.erl

@@ -295,13 +295,17 @@ stop() ->
 %%-----------------------------------------------------------------------------
 -spec sta_rssi() -> {ok, Rssi :: db()} | {error, Reason :: term()}.
 sta_rssi() ->
-    Port = get_port(),
-    Ref = make_ref(),
-    Port ! {self(), Ref, rssi},
-    receive
-        {Ref, {error, Reason}} -> {error, Reason};
-        {Ref, {rssi, Rssi}} -> {ok, Rssi};
-        Other -> {error, Other}
+    case whereis(network_port) of
+        undefined ->
+            {error, network_down};
+        Port ->
+            Ref = make_ref(),
+            Port ! {self(), Ref, rssi},
+            receive
+                {Ref, {error, Reason}} -> {error, Reason};
+                {Ref, {rssi, Rssi}} -> {ok, Rssi};
+                Other -> {error, Other}
+            end
     end.
 
 %%

src/platforms/esp32/components/avm_builtins/network_driver.c

@@ -79,6 +79,7 @@ static const char *const sta_connected_atom = ATOM_STR("\xD", "sta_connected");
 static const char *const sta_beacon_timeout_atom = ATOM_STR("\x12", "sta_beacon_timeout");
 static const char *const sta_disconnected_atom = ATOM_STR("\x10", "sta_disconnected");
 static const char *const sta_got_ip_atom = ATOM_STR("\xA", "sta_got_ip");
+static const char *const network_down_atom = ATOM_STR("\x0C", "network_down");
 
 ESP_EVENT_DECLARE_BASE(sntp_event_base);
 ESP_EVENT_DEFINE_BASE(sntp_event_base);
@@ -847,13 +848,24 @@ static void get_sta_rssi(Context *ctx, term pid, term ref)
     size_t tuple_reply_size = PORT_REPLY_SIZE + TUPLE_SIZE(2);
 
     int sta_rssi = 0;
-    esp_err_t err = esp_wifi_sta_get_rssi(&sta_rssi);
-    if (UNLIKELY(err != ESP_OK)) {
-        term error_term = term_from_int(err);
-        ESP_LOGE(TAG, "error obtaining RSSI: [%i] %u", err, error_term);
-        // Reply: {Ref, {error, Reason}}
+    wifi_ap_record_t ap_info;
+    esp_err_t status = esp_wifi_sta_get_ap_info(&ap_info);
+    if (status == ESP_OK) {
+        esp_err_t err = esp_wifi_sta_get_rssi(&sta_rssi);
+        if (UNLIKELY(err != ESP_OK)) {
+            term error_term = term_from_int(err);
+            ESP_LOGE(TAG, "error obtaining RSSI: [%i] %u", err, error_term);
+            // Reply: {Ref, {error, Reason}}
+            port_ensure_available(ctx, tuple_reply_size);
+            term error = port_create_error_tuple(ctx, error_term);
+            port_send_reply(ctx, pid, ref, error);
+            return;
+        }
+    } else {
+        ESP_LOGE(TAG, "Device is not connected to any AP.");
+        // Reply: {Ref, {error, network_down}}
         port_ensure_available(ctx, tuple_reply_size);
-        term error = port_create_error_tuple(ctx, error_term);
+        term error = port_create_error_tuple(ctx, make_atom(ctx->global, network_down_atom));
         port_send_reply(ctx, pid, ref, error);
         return;
     }

src/platforms/esp32/test/main/test_erl_sources/test_wifi_example.erl

@@ -25,6 +25,8 @@
 start() ->
     case verify_platform(atomvm:platform()) of
         ok ->
+            % test that sta_rssi() can be safely called, when network is not started
+            {error, network_down} = network:sta_rssi(),
             ok = start_network(),
             ok = network:stop(),
             start_network(),
@@ -59,7 +61,11 @@ start_network() ->
     ],
     case network:start(Config) of
         {ok, _Pid} ->
-            io:format("Network started.~n");
+            % test that sta_rssi() can be safely called
+            % when network is just started, but may not yet be connected.
+            network:sta_rssi(),
+            io:format("Network started.~n"),
+            ok;
         Error ->
             Error
     end.