Linux port: Initial implementation of linux port and mock layers

esp_modem/src/esp_modem_netif_linux.cpp

@@ -12,7 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <thread>
 #include "cxx_include/esp_modem_netif.hpp"
+#include "cxx_include/esp_modem_dte.hpp"
 
 namespace esp_modem {
 
@@ -20,29 +22,39 @@ void Netif::on_ppp_changed(void *arg, esp_event_base_t event_base,
                            int32_t event_id, void *event_data) {
 }
 
-esp_err_t Netif::esp_modem_dte_transmit(void *h, void *buffer, size_t len) {
-    return ESP_OK;
+esp_err_t Netif::esp_modem_dte_transmit(void *h, void *buffer, size_t len)
+{
+    auto *this_netif = static_cast<Netif *>(h);
+    this_netif->ppp_dte->write((uint8_t *) buffer, len);
+    return len;
 }
 
 esp_err_t Netif::esp_modem_post_attach(esp_netif_t *esp_netif, void *args) {
     return ESP_OK;
 }
 
-void Netif::receive(uint8_t *data, size_t len) {
+void Netif::receive(uint8_t *data, size_t len)
+{
+    esp_netif_receive(netif, data, len);
 }
 
 Netif::Netif(std::shared_ptr<DTE> e, esp_netif_t *ppp_netif) :
-        ppp_dte(std::move(e)), netif(ppp_netif) {
+        ppp_dte(std::move(e)), netif(ppp_netif) {}
+
+void Netif::start()
+{
+    ppp_dte->set_read_cb([this](uint8_t *data, size_t len) -> bool {
+        receive(data, len);
+        return false;
+    });
+    netif->transmit = esp_modem_dte_transmit;
+    netif->ctx = (void*)this;
+    signal.set(PPP_STARTED);
 }
 
-void Netif::start() {
-}
+void Netif::stop() {}
 
-void Netif::stop() {
-}
-
-Netif::~Netif() {
-}
+Netif::~Netif() = default;
 
 void Netif::wait_until_ppp_exits() {