关于检测联网check_netdev_internet_up_work()

发布于 2022-11-24 14:42:51 浏览：778 订阅该版

rtt中，检测网络是否连网的策略是：向link.rt-thread.org发UDP包，在2秒内收到回包，则认为已联网

```c
/* check SAL network interface device internet status */
static void check_netdev_internet_up_work(struct rt_work *work, void *work_data)
{
#define SAL_INTERNET_VERSION   0x00
#define SAL_INTERNET_BUFF_LEN  12
#define SAL_INTERNET_TIMEOUT   (2)

#define SAL_INTERNET_HOST      "link.rt-thread.org"
#define SAL_INTERNET_PORT      8101

#define SAL_INTERNET_MONTH_LEN 4
#define SAL_INTERNET_DATE_LEN  16

int index, sockfd = -1, result = 0;
    struct sockaddr_in server_addr;
    struct hostent *host;
    struct timeval timeout;
    struct netdev *netdev = (struct netdev *)work_data;
    socklen_t addr_len = sizeof(struct sockaddr_in);
    char send_data[SAL_INTERNET_BUFF_LEN], recv_data = 0;
    struct rt_delayed_work *delay_work = (struct rt_delayed_work *)work;

const char month[][SAL_INTERNET_MONTH_LEN] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
    char date[SAL_INTERNET_DATE_LEN];
    int moth_num = 0;

struct sal_proto_family *pf = (struct sal_proto_family *) netdev->sal_user_data;
    const struct sal_socket_ops *skt_ops;

if (work)
    {
        rt_free(delay_work);
    }

/* get network interface socket operations */
    if (pf == RT_NULL || pf->skt_ops == RT_NULL)
    {
        result = -RT_ERROR;
        goto __exit;
    }

host = (struct hostent *) pf->netdb_ops->gethostbyname(SAL_INTERNET_HOST);
    if (host == RT_NULL)
    {
        result = -RT_ERROR;
        goto __exit;
    }

skt_ops = pf->skt_ops;
    if ((sockfd = skt_ops->socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        result = -RT_ERROR;
        goto __exit;
    }

server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SAL_INTERNET_PORT);
    server_addr.sin_addr = *((struct in_addr *)host->h_addr);
    rt_memset(&(server_addr.sin_zero), 0, sizeof(server_addr.sin_zero));

timeout.tv_sec = SAL_INTERNET_TIMEOUT;
    timeout.tv_usec = 0;

/* set receive and send timeout */
    skt_ops->setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (void *) &timeout, sizeof(timeout));
    skt_ops->setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, (void *) &timeout, sizeof(timeout));

/* get build moth value*/
    rt_memset(date, 0x00, SAL_INTERNET_DATE_LEN);
    rt_snprintf(date, SAL_INTERNET_DATE_LEN, "%s", __DATE__);

for (index = 0; index < sizeof(month) / SAL_INTERNET_MONTH_LEN; index++)
    {
        if (rt_memcmp(date, month[index], SAL_INTERNET_MONTH_LEN - 1) == 0)
        {
            moth_num = index + 1;
            break;
        }
    }

/* not find build month */
    if (moth_num == 0 || moth_num > sizeof(month) / SAL_INTERNET_MONTH_LEN)
    {
        result = -RT_ERROR;
        goto __exit;
    }

rt_memset(send_data, 0x00, SAL_INTERNET_BUFF_LEN);
    send_data[0] = SAL_INTERNET_VERSION;
    for (index = 0; index < netdev->hwaddr_len; index++)
    {
        send_data[index + 1] = netdev->hwaddr[index] + moth_num;
    }
    send_data[9] = RT_VERSION;
    send_data[10] = RT_SUBVERSION;
    send_data[11] = RT_REVISION;

skt_ops->sendto(sockfd, send_data, SAL_INTERNET_BUFF_LEN, 0,
                    (struct sockaddr *)&server_addr, sizeof(struct sockaddr));

result = skt_ops->recvfrom(sockfd, &recv_data, sizeof(recv_data), 0, (struct sockaddr *)&server_addr, &addr_len);
    if (result < 0)
    {
        goto __exit;
    }

if (recv_data == RT_FALSE)
    {
        result = -RT_ERROR;
        goto __exit;
    }

__exit:
    if (result > 0)
    {
        LOG_D("Set network interface device(%s) internet status up.", netdev->name);
        netdev->flags |= NETDEV_FLAG_INTERNET_UP;
    }
    else
    {
        LOG_D("Set network interface device(%s) internet status down.", netdev->name);
        netdev->flags &= ~NETDEV_FLAG_INTERNET_UP;
    }

if (sockfd >= 0)
    {
        skt_ops->closesocket(sockfd);
    }
}
```
疑问：
1. 收包超时时间怎么是2秒？一般网络通讯超时时间都是5秒
2. 随着物联设备增多，会不会出现批量问题？比如，rt-thread.org服务器宕机，导致批量不能上线？或者，换个说法，某事件导致设备批量集中上线，会不会挤爆rt-thread.org服务器？这种问题，本人有遇过。
3. 物联网卡，目前都有白名单机制，建议相关文档说明下，rt-thread.org应加入到sim卡白名单中。