esp_netif: Introduction of esp-netif component as a replacement of tcpip_adpter

- provides object oriented access to network intefaces
- not limited to default netifs
- more generic abstraction to network input output functions
- event handler registration removed from component responsibility
- backward compatibility layer for legacy tcpip_apapter APIs

Closes IDF-39

components/esp_netif/esp_netif_objects.c

@@ -0,0 +1,102 @@
+// Copyright 2015-2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "esp_netif.h"
+#include "sys/queue.h"
+#include "esp_log.h"
+
+//
+// Purpose of this module is to provide list of esp-netif structures
+//  - this module has no dependency on a specific network stack (lwip)
+//
+
+static const char *TAG = "esp_netif_objects";
+
+//#define ESP_NETIF_TYPE_DEFINE(id) const esp_netif_type_t id = #id
+
+typedef struct slist_netifs_s slist_netifs_t;
+struct slist_netifs_s {
+    esp_netif_t *netif;
+    SLIST_ENTRY(slist_netifs_s) next;
+};
+
+SLIST_HEAD(slisthead, slist_netifs_s) s_head = { .slh_first = NULL, };
+
+static size_t s_esp_netif_counter = 0;
+
+ESP_EVENT_DEFINE_BASE(IP_EVENT);
+
+//ESP_NETIF_TYPE_DEFINE(ESP_NETIF_TYPE_STA);
+//ESP_NETIF_TYPE_DEFINE(ESP_NETIF_TYPE_AP);
+//ESP_NETIF_TYPE_DEFINE(ESP_NETIF_TYPE_ETH);
+
+
+//
+// List manipulation functions
+//
+esp_err_t esp_netif_add_to_list(esp_netif_t *netif)
+{
+    struct slist_netifs_s *item = calloc(1, sizeof(struct slist_netifs_s));
+    ESP_LOGD(TAG, "%s %p", __func__, netif);
+    if (item == NULL) {
+        return ESP_ERR_NO_MEM;
+    }
+    item->netif = netif;
+
+    SLIST_INSERT_HEAD(&s_head, item, next);
+    ++s_esp_netif_counter;
+    ESP_LOGD(TAG, "%s netif added successfully (total netifs: %d)", __func__, s_esp_netif_counter);
+    return ESP_OK;
+}
+
+
+esp_err_t esp_netif_remove_from_list(esp_netif_t *netif)
+{
+    struct slist_netifs_s *item;
+    ESP_LOGV(TAG, "%s %p", __func__, netif);
+    SLIST_FOREACH(item, &s_head, next) {
+        if (item->netif == netif) {
+            SLIST_REMOVE(&s_head, item, slist_netifs_s, next);
+            assert(s_esp_netif_counter > 0);
+            --s_esp_netif_counter;
+            ESP_LOGD(TAG, "%s netif successfully removed (total netifs: %d)", __func__, s_esp_netif_counter);
+            free(item);
+            return ESP_OK;
+        }
+    }
+    return ESP_ERR_NOT_FOUND;
+}
+
+size_t esp_netif_get_nr_of_ifs(void)
+{
+    return s_esp_netif_counter;
+}
+
+esp_netif_t* esp_netif_next(esp_netif_t* netif)
+{
+    ESP_LOGV(TAG, "%s %p", __func__, netif);
+    struct slist_netifs_s *item;
+    if (netif == NULL) {
+        item = SLIST_FIRST(&s_head);
+        return (item == NULL) ? NULL : item->netif;
+    } else {
+        SLIST_FOREACH(item, &s_head, next) {
+            if (item->netif == netif) {
+                item = SLIST_NEXT(item, next);
+                return (item == NULL) ? NULL : item->netif;
+            }
+        }
+    }
+    return NULL;
+}