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Merge pull request !965 from Annie_wang/master

en/device-dev/porting/porting-chip-board-lwip.md

+# lwIP Module Adaptation<a name="EN-US_TOPIC_0000001172881086"></a>
+
+Lightweight IP (lwIP) is an open-source TCP/IP stack designed for embedded systems. LiteOS-M has adapted to lwIP and provides enhanced lwIP features. The lwIP code consists of the following:
+
+- lwIP source code in the **third_party/lwip** directory: Only a few intrusive modifications have been made for enhanced features.
+
+- Code for lwIP adaptation and enhancement in the **kernel/liteos_m/components/net/lwip-2.1** directory: The default lwIP configuration file is provided.
+
+If you want to use the lwIP module, perform the following steps to complete adaptation:
+
+1. Create a directory, for example, **lwip_adapter**, in the device directory to store its adaptation files.
+
+2. Create the **include** directory in the **lwip_adapter** directory to store the adaptation header files.
+
+3. Create the **lwip** directory in the **include** directory and then create the header file **lwipopts.h** in the **lwip** directory. The code is as follows. If the default configuration cannot meet service requirements, modify the configuration, for example, disable the DHCP function.
+
+    ```
+    #ifndef _LWIP_ADAPTER_LWIPOPTS_H_
+    #define _LWIP_ADAPTER_LWIPOPTS_H_
+
+    #include_next "lwip/lwipopts.h"
+
+    #undef LWIP_DHCP
+    #define LWIP_DHCP                       0 // Disable the DHCP function.
+
+    #endif /* _LWIP_ADAPTER_LWIPOPTS_H_ */
+    ```
+
+4. Copy **BUILD.gn** in the **kernel/liteos_m/components/net/lwip-2.1/porting** directory to the **lwip_adapter** directory and modify the file as follows:
+
+    ```
+    import("//kernel/liteos_m/liteos.gni")
+    import("$LITEOSTHIRDPARTY/lwip/lwip.gni")
+    import("$LITEOSTOPDIR/components/net/lwip-2.1/lwip_porting.gni")
+
+    module_switch = defined(LOSCFG_NET_LWIP_SACK)
+    module_name = "lwip"
+    kernel_module(module_name) {
+      sources = LWIP_PORTING_FILES + LWIPNOAPPSFILES - [ "$LWIPDIR/api/sockets.c" ]
+      include_dirs = [ "//utils/native/lite/include" ]
+    }
+
+    # Add include, the directory of the new adaptation header file.
+    config("public") {
+      include_dirs = [ "include" ] + LWIP_PORTING_INCLUDE_DIRS + LWIP_INCLUDE_DIRS
+    }
+    ```
+
+5. In the device configuration file (for example, **config.json**), set the lwIP build path to the path of **BUILD.gn** in step 4.
+
+    ```
+    {
+      "subsystem": "kernel",
+      "components": [
+        { "component": "liteos_m", "features":["ohos_kernel_liteos_m_lwip_path = \"//xxx/lwip_adapter\"" ] }
+      ]
+    },
+    ```
+
+6. In the kernel build configuration file of the device, for example, **kernel_config/debug.config**, enable lwIP build.
+
+    ```
+    LOSCFG_NET_LWIP=y
+    ```

en/device-dev/porting/porting-chip-board.md

-# Board-Level OS Porting<a name="EN-US_TOPIC_0000001199842515"></a>
+# Board-Level OS Porting<a name="EN-US_TOPIC_0000001062604739"></a>
 
 -   **[Overview](porting-chip-board-overview.md)**  
 
@@ -8,6 +8,8 @@
 
 -   **[System Modules](porting-chip-board-component.md)**  
 
+-   **[lwIP Module Adaptation](porting-chip-board-lwip.md)**  
+
 -   **[Third-party Module Adaptation](porting-chip-board-bundle.md)**  
 
 -   **[XTS](porting-chip-board-xts.md)**