OpenHarmony NetDev 原创精华

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发布于 2022-4-9 09:37

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NetDev

WIFI 芯片属于网络设备，自然也要归OpenHarmony的网络框架管理，本文用于了解网络数据如何在协议栈和网络驱动之间传输。

网络设备的使用需要配合网络协议栈，OpenHarmony的网络协议栈有两种，一种是liteos-a内核使用的lwip协议栈，一种是标准系统linux内核网络协议栈。

本文以lwip协议栈为例来了解。

一、前提

网络数据的通路：（这里的网口驱动是具体wifi芯片的驱动程序，由厂商实现。）

发送数据：应用程序->lwip->网口驱动

接受数据：网口驱动->lwip->应用程序

二、NetDevice

openharmony使用NetDevice结构体来描述所有的网络设备（网口）

typedef struct NetDevice {
    NetIfCategory netifCateg;                 //内核类型
    char name[IFNAMSIZ];                      //设备名称
    NetLinkType LinkLayerType;                //链路层类型：以太网或wifi
    IfType funType;                           //网络端口类型 including AP, STA, and P2P
    uint8_t macAddr[MAC_ADDR_SIZE];           //mac地址
    ....
    struct NetDeviceInterFace *netDeviceIf;   //提供给驱动厂商的接口
    struct NetDevice *owner;                  /**< Network device */
    struct NetDevStats stats;                 /**< Network statistics */
} NetDevice;
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其中 NetDeviceInterFace 对象的作用是初始化、打开、关闭一个网络设备等以下功能，必须由驱动开发厂商根据具体的wifi芯片编写的驱动来实现其中的函数：

struct NetDeviceInterFace {
    int32_t (*init)(struct NetDevice *netDev);  //初始化网络设备
    void (*deInit)(struct NetDevice *netDev);   
    int32_t (*open)(struct NetDevice *netDev);  //打开数据链路层
    int32_t (*stop)(struct NetDevice *netDev);  
    NetDevTxResult (*xmit)(struct NetDevice *netDev, NetBuf *netBuff);        //发送数据
    int32_t (*ioctl)(struct NetDevice *netDev, IfReq *req, int32_t cmd);      /**< Used for the control command word. */
    int32_t (*setMacAddr)(struct NetDevice *netDev, void *addr);              //设置mac地址
    struct NetDevStats *(*getStats)(struct NetDevice *netDev);                //获取设备状态
    void (*setNetIfStatus)(struct NetDevice *netDev, NetIfStatus status);     //设置状态
    uint16_t (*selectQueue)(struct NetDevice *netDev, NetBuf *netBuff);       //选择一个队列
    uint32_t (*netifNotify)(struct NetDevice *netDev, NetDevNotify *notify);  /**< Notifies the network port status. */
    int32_t (*changeMtu)(struct NetDevice *netDev, int32_t newMtu);           //改变mtu
    void (*linkStatusChanged)(struct NetDevice *netDev);   	//检查以太网连接状态
    ProcessingResult (*specialEtherTypeProcess)(const struct NetDevice *netDev, NetBuf *buff);
                                                                              /**< Performs private processing without
                                                                               * involving network-layer data.
                                                                               */
};
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根据HdfWlanDevice 创建NetDevice：

struct NetDevice *AllocPlatformNetDevice(struct HdfWlanDevice *device)
{
    struct NetDevice *result = NULL;
    char ifName[IFNAMSIZ] = {0};
    struct HdfWifiNetDeviceData *data = NULL;
    data = (struct HdfWifiNetDeviceData *)OsalMemCalloc(sizeof(struct HdfWifiNetDeviceData));
    do {
        //分配网卡编号
        for (i = 0; i < MAX_IF_COUNT; i++) {
            if (((g_allocatedIfMap >> i) & 0x1) != 0x1) {
                id = i;
                break;
            }
        }
		//生成网卡名称：wlan0
        ret = GetPlatformIfName(id, ifName, IFNAMSIZ);
#ifdef _PRE_HDF_LINUX
        result = NetDeviceInit(ifName, strlen(ifName), WIFI_LINK, FULL_OS);
#else
        //获取netdev
        result = NetDeviceInit(ifName, strlen(ifName), WIFI_LINK, LITE_OS);
#endif
    } while (false);
    result->classDriverName = HDF_WIFI_PLATFORM_DRIVER_NAME;
    result->classDriverPriv = data;
    data->netInterfaceId = id;
    SET_BIT(device->netIfMap, id);
    SET_BIT(g_allocatedIfMap, id);
    return result;
}
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三、NetBuf

NetBuf用于描述网络数据，以在网络协议栈和网络驱动之间传输数据。

//记录一段网络数据的偏移和长度
struct BufField {
    uint32_t offset;      /**< Offset of the buffer segment */
    uint32_t len;         /**< Length of the buffer segment */
};

typedef struct NetBuf {
    struct DListHead dlist;             //双链表
    struct BufField bufs[MAX_BUF_NUM];  
    uint8_t     *mem;                   //内存地址
    uint32_t    len;                    //内存长度
    uint32_t    dataLen;                //真实数据长度
    void        *dev;                   //接受到该数据的netdev
    uint32_t    qmap;                   /**< Queue mappings of the network data buffer */
    uint8_t     rsv[MAX_NETBUF_RESEVER_SIZE]; /**< Reserved field. For details, see {@link MAX_NETBUF_RESEVER_SIZE}. */
} NetBuf;
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四、适配器 NetDeviceImpl

这里有一个问题，就是openharmony使用NetDev来描述网口，用NetBuf来描述网口数据，但是在lwip协议栈中，有他自己的一套机制来描述网口和网络数据。

这里就存在一个适配（adapt）的问题，需要一个适配器（adapter）来适配这两套机制，使得数据能在这两者之间顺利传递。

NetDev ------> netif
NetBuf ------> pbuf
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NetDeviceImpl结构体应运而生，该部分的代码在bearpi_micro/drivers/adapter/khdf/liteos/network/src/net_device_adapter.c，net_device_adapter顾名思义就是把net_device适配到lwip的netif。同理netbuf_adapter.c实现的就是把netbuf适配到lwip的pbuf。

struct NetDeviceImpl {
    struct NetDevice *netDevice;	//可通过netDevice->NetDeviceInterFace 调用芯片驱动程序
    struct NetDeviceImplOp *interFace;	//调用lwip的接口
    void *osPrivate;	//指向 lwip的netif对象
};
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所以NetDeviceImpl 就是芯片驱动程序和 lwip协议栈沟通的中介，其成员的作用很明显：

NetDevice：可通过netDevice->NetDeviceInterFace 调用芯片驱动程序
NetDeviceImplOp：提供给开发者的接口
osPrivate：指向 lwip的netif对象

NetDeviceImplOp

NetDeviceImplOp结构体就是提供给开发者的接口，使得网口驱动程序能与lwip协议栈交互。在net_device_adapter.c中的g_liteNdImplOps就是NetDeviceImplOp。我们将通过这个结构体，看lwip协议栈如何收发数据。

struct NetDeviceImplOp {
   	//初始化netdev
    int32_t (*init)(struct NetDeviceImpl *netDevice);
    int32_t (*deInit)(struct NetDeviceImpl *netDevice);
    int32_t (*add)(struct NetDeviceImpl *netDevice);
    int32_t (*delete)(struct NetDeviceImpl *netDevice);
    int32_t (*setStatus)(struct NetDeviceImpl *netDevice, NetIfStatus status);
    int32_t (*setLinkStatus)(struct NetDeviceImpl *netDevice, NetIfLinkStatus status);
    int32_t (*getLinkStatus)(struct NetDeviceImpl *netDevice, NetIfLinkStatus *status);
    int32_t (*receive)(struct NetDeviceImpl *netDevice, NetBuf *buff, ReceiveFlag flag);
    int32_t (*setIpAddr)(struct NetDeviceImpl *netDevice, const IpV4Addr *ipAddr, const IpV4Addr *netMask,
        const IpV4Addr *gw);
    int32_t (*dhcpsStart)(struct NetDeviceImpl *netDevice, char *ip, uint16_t ipNum);
    int32_t (*dhcpsStop)(struct NetDeviceImpl *netDevice);
    int32_t (*dhcpStart)(struct NetDeviceImpl *netDevice);
    int32_t (*dhcpStop)(struct NetDeviceImpl *netDevice);
    int32_t (*dhcpIsBound)(struct NetDeviceImpl *netDevice);
    int32_t (*changeMacAddr)(struct NetDeviceImpl *netDevice);
};

static struct NetDeviceImplOp g_liteNdImplOps = {
    .init = LiteNetDevInit,		//创建netif
    .deInit = LiteNetDevDeInit,
    .add = LiteNetDevAdd,	//创建netif并添加到协议栈
    .delete = LiteNetDevDelete,
    .setStatus = LiteNetDevSetStatus,
    .setLinkStatus = LiteNetDevSetLinkStatus,
    .getLinkStatus = LiteNetDevGetLinkStatus,
    .receive = LiteNetDevReceive,	//将数据上传到协议栈
    .setIpAddr = LiteNetSetIpAddr,	//设置ip
    .dhcpsStart = LiteNetDhcpsStart,	//开始dhcp
    .dhcpsStop = LiteNetDhcpsStop,
    .dhcpStart = LiteNetDhcpStart,
    .dhcpStop = LiteNetDhcpStop,
    .dhcpIsBound = LiteNetDhcpIsBound,
    .changeMacAddr = LiteNetChangeMacAddr,
};
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五、netif

要使用lwip协议栈，就需要创建一个netif来描述所使用的wifi 网口。NetDeviceImplOp结构体提供给开发者创建netif的接口：

创建初始化lwip netif的接口：

g_liteNdImplOps.init()
g_liteNdImplOps.add()

struct NetDeviceAdapterLite {
    struct netif *lwipNetif;
};
//创建netif
static int32_t LiteNetDevInit(struct NetDeviceImpl *netDeviceImpl)
{
    struct NetDeviceAdapterLite *liteNdPri = NULL;

    liteNdPri = (struct NetDeviceAdapterLite *)OsalMemCalloc(sizeof(struct NetDeviceAdapterLite));
    (void)memset_s(liteNdPri, sizeof(struct NetDeviceAdapterLite), 0, sizeof(struct NetDeviceAdapterLite));
    netDeviceImpl->osPrivate = (void *)liteNdPri;
}
//创建netif并添加到协议栈
static int32_t LiteNetDevAdd(struct NetDeviceImpl *netDeviceImpl)
{
    struct NetDeviceAdapterLite *liteNdPri = (struct NetDeviceAdapterLite *)netDeviceImpl->osPrivate;
    struct NetDevice *lwipNd = netDeviceImpl->netDevice;
	//根据lwipNd创建netif
    lwipNf = CreateLwipNetIf(netDeviceImpl, lwipNd创建netif);
    if ((ret = netifapi_netif_add(lwipNf, &ipaddr, &netmask, &gw)) != ERR_OK) {
        return HDF_FAILURE;
    }
    //复制mac地址
    if (memcpy_s(lwipNf->hwaddr, NETIF_MAX_HWADDR_LEN, lwipNd->macAddr, MAC_ADDR_SIZE) != EOK) {
        return HDF_FAILURE;
    }

    liteNdPri->lwipNetif = lwipNf;
    IpV6SpecialProc(lwipNd, lwipNf);
    /* set netif default status */
    netifapi_netif_set_default(lwipNf);
    netif_set_link_callback(lwipNf, LiteNetifLinkChangeCallback);
    return HDF_SUCCESS;
}


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创建netif的同时实现了netif的一些函数如drv_send、drv_set_hwaddr，这些函数需要调用芯片驱动。

static struct netif *CreateLwipNetIf(const struct NetDeviceImpl *netDeviceImpl, const struct NetDevice *netDev)
{
    lwipNf = (struct netif *)OsalMemCalloc(sizeof(struct netif));
    (void)memset_s(lwipNf, sizeof(struct netif), 0, sizeof(struct netif));

    /* register netif to lwip */
    lwipNf->state = (void *)netDeviceImpl;
    lwipNf->drv_send = LwipSend;
    lwipNf->drv_set_hwaddr = LwipSetHwaddr;
    lwipNf->link_layer_type = netDev->LinkLayerType;
    lwipNf->hwaddr_len = MAC_ADDR_SIZE;
    lwipNf->drv_config = LwipDrvConfig;

    return lwipNf;
}
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网口发送数据到lwip

在网口的驱动程序收到数据后，需要传递给lwip协议栈，这时调用NetDeviceImplOp->reveive()函数来传递数据：

首先把netdev转换成netif，把netbuf转换成pbuf，再调用driverif_input()传递pbuf给lwip协议栈。

static int32_t LiteNetDevReceive(struct NetDeviceImpl *netDeviceImpl, struct NetBuf *buff, ReceiveFlag flag)
{
    //get lwip netif
    struct netif *lwipNf = GetNetIfFromDevImpl(netDeviceImpl);
    ProcessingResult ret = LiteNetDevDataFilter(netDeviceImpl, buff);
    if (ret == PROCESSING_CONTINUE) {
        //call LiteNetDevDataReceive to send pbuf
        return LiteNetDevDataReceive(netDeviceImpl, buff);
    } else if (ret == PROCESSING_COMPLETE) {
        return HDF_SUCCESS;
    } else {
        return HDF_FAILURE;
    }
}

static int32_t LiteNetDevDataReceive(struct NetDeviceImpl *netDeviceImpl, struct NetBuf *buff)
{
    struct netif *lwipNf = GetNetIfFromDevImpl(netDeviceImpl);
    //Conver NetBuf To PBuf
    struct pbuf *pBuff = ConverNetBufToPBuf(buff);
	//post pbuff to lwip
    driverif_input(lwipNf, pBuff);
    NetBufFree(buff);
    return HDF_SUCCESS;
}
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driverif_input()是由lwip提供的接口，定义如下：

/*
 * This function should be called by network driver to pass the input packet to LwIP.
 * Before calling this API, driver has to keep the packet in pbuf structure. Driver has to
 * call pbuf_alloc() with type as PBUF_RAM to create pbuf structure. Then driver
 * has to pass the pbuf structure to this API. This will add the pbuf into the TCPIP thread.
 * Once this packet is processed by TCPIP thread, pbuf will be freed. Driver is not required to
 * free the pbuf.
 *
 * @param netif the lwip network interface structure for this driverif
 * @param p packet in pbuf structure format
 */
void driverif_input(struct netif *netif, struct pbuf *p)
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网口从lwip接收数据

lwip协议栈的数据会传递到netif结构体，而我们在创建netif结构体时，设置了drv_send()等函数，lwip协议栈就会调用该函数，在这个函数中我们就需要实现netif和netdev，pbuf和netbuf的转换，调用NetDeviceInterFace 里的函数发送数据。

void LwipSend(struct netif *netif, struct pbuf *lwipBuf)
{
    struct NetDeviceImpl *ndImpl = (struct NetDeviceImpl *)netif->state;
    //get netdev
    struct NetDevice *netDev = ndImpl->netDevice;
    struct NetDeviceInterFace *netDevIf = NULL;
	//get netbuf
    struct NetBuf *netBuff = ConverPbuffToNetBuf(netDev, lwipBuf);
	//get NetDeviceInterFace 
    netDevIf = netDev->netDeviceIf;
    //send netbuf
    netDevIf->xmit(netDev, netBuff);
    return;
}
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分类

标签

51CTO

51CTO博客

51CTO学堂

OpenHarmony NetDev 原创精华

NetDev

一、前提

二、NetDevice

三、NetBuf

四、适配器 NetDeviceImpl

NetDeviceImplOp

五、netif

网口发送数据到lwip

网口从lwip接收数据

目录

订阅鸿蒙技术特刊，精选内容抢先看

51CTO

51CTO博客

51CTO学堂

OpenHarmony NetDev 原创 精华

NetDev

一、前提

二、NetDevice

三、NetBuf

四、适配器 NetDeviceImpl

NetDeviceImplOp

五、netif

网口发送数据到lwip

网口从lwip接收数据

目录

订阅鸿蒙技术特刊，精选内容抢先看

OpenHarmony NetDev 原创精华