RT-Thread-RT-Thread eth 模块(Lwip)修改为静态IP时,DNS设置问题RT-Thread问答社区

RT-Thread eth 模块(Lwip)修改为静态IP时,DNS设置问题

发布于 2023-04-20 17:46:14 浏览：1424 订阅该版

```c
    tsIpAddrress staticIp={
            .ip_address     = "192.168.0.240",
            .netmask        = "255.255.0.0",
            .gw_address     = "192.168.1.1",
            .dns_address[0] = "8.8.8.8",
            .dns_address[1] =  "114.114.114.114"};

void setStaticIp(const char *name, tsIpAddrress *ipaddr)
{
    struct netdev *netdev = RT_NULL;
    ip_addr_t addr;
    int ret;

netdev = netdev_get_by_name(name);
    if (netdev == RT_NULL)
    {
        rt_kprintf("bad network interface device name(%s).\n", name);
        return;
    }
    netdev_dhcp_enabled(netdev,RT_FALSE);

/* set IP address */
    if ((ipaddr->ip_address != NULL) && inet_aton(ipaddr->ip_address, &addr))
    {
        netdev_set_ipaddr(netdev, &addr);
    }

/* set netmask address */
    if ((ipaddr->netmask != NULL) && inet_aton(ipaddr->netmask, &addr))
    {
        netdev_set_netmask(netdev, &addr);
    }

/* set gateway address */
    if ((ipaddr->gw_address != NULL) && inet_aton(ipaddr->gw_address, &addr))
    {
        netdev_set_gw(netdev, &addr);
    }

/* set dns 0 */
    if ((ipaddr->dns_address[0] != NULL) && inet_aton(ipaddr->dns_address[0], &addr))
    {
        rt_kprintf("dns0 aton (%s).\n", ipaddr->dns_address[0]);
        ret = netdev_set_dns_server(netdev, 0, &addr);
        if(ret != RT_EOK)
            rt_kprintf("netdev_set_dns_server ERR %d!!!\n",ret);
    }
    else
    {
        if(ipaddr->dns_address[0] != NULL)
            rt_kprintf("dns0 aton err (%s).\n", ipaddr->dns_address[0]);
        inet_aton(ipaddr->gw_address, &addr);       /* 用网关地址替代DNS0 */
        ret = netdev_set_dns_server(netdev, 0, &addr);
        if(ret != RT_EOK)
            rt_kprintf("netdev_set_dns_server ERR %d!!!\n",ret);
    }

/* set dns 1 */
    if ((ipaddr->dns_address[1] != NULL) && inet_aton(ipaddr->dns_address[1], &addr))
    {
        rt_kprintf("dns1 aton (%s).\n", ipaddr->dns_address[1]);
        ret = netdev_set_dns_server(netdev, 1, &addr);
        if(ret != RT_EOK)
            rt_kprintf("netdev_set_dns_server ERR %d!!!\n",ret);
    }
    else
    {
        if(ipaddr->dns_address[1] != NULL)
            rt_kprintf("dns1 aton err (%s).\n", ipaddr->dns_address[1]);
        inet_aton("8.8.8.8", &addr);             /* 默认DNS1 */
        ret = netdev_set_dns_server(netdev, 1, &addr);
        if(ret != RT_EOK)
            rt_kprintf("netdev_set_dns_server ERR %d!!!\n",ret);
    }
}

setStaticIp("e0",&staticIp);
```
以上代码为应用部分代码,设备是接入到正常网络中,网络中有DHCP服务器,可以正常获取到IP和DNS
获取的地址如下:

```c
ip address: 192.168.0.64
gw address: 192.168.0.1
net mask  : 255.255.0.0
dns server #0: 192.168.0.1
dns server #1: 8.8.8.8
```
手动设置为静态IP时,IP如下:

```c
ip address: 192.168.0.240
gw address: 192.168.1.1
net mask  : 255.255.0.0
dns server #0: 192.168.0.1
dns server #1: 114.114.114.114
```
可以很明显的发现 dns server #0:与设置的并不相同
修改代码
`.dns_address[0] = "1.1.1.1",`
发现能正确修改,故判断代码没有问题,问题肯定是网卡层或者协议栈有限制
发现代码问题如下:
代码位于"netdev下"
```c
void netdev_low_level_set_dns_server(struct netdev *netdev, uint8_t dns_num, const ip_addr_t *dns_server)
{
    int index;

RT_ASSERT(dns_server);

if (netdev == RT_NULL)
    {
        return;
    }
	/* 问题代码就在这里
	* 	设置DNS不能两个同时设置,需要分两次设置
	*	由于测试环境是动态获取IP后设置为静态,之前DNS #1 是 新设置的 DNS #2
	*	这里循环判断了历史的两个DNS是否与新的相同,只要其中一个相同就返回
	*	此处这样写:我猜测有两个原因,1是防止两个DNS设置为一样了,2是相同DNS不重复设置
	*	此问题可以说是一个BUG,希望官方能修正
	*/
    /* check DNS servers is exist */
    for (index = 0; index < NETDEV_DNS_SERVERS_NUM; index++)
    {
        if (ip_addr_cmp(&(netdev->dns_servers[index]), dns_server))
        {
            return;
        }
    }

if (dns_num < NETDEV_DNS_SERVERS_NUM)
    {
        ip_addr_copy(netdev->dns_servers[dns_num], *dns_server);

/* execute DNS servers address change callback function */
        if (netdev->addr_callback)
        {
            netdev->addr_callback(netdev, NETDEV_CB_ADDR_DNS_SERVER);
        }
    }
}
```