获取设备的接口名、ip、子网掩码、MAC、网关信息

梦里梦外; 2022-12-20 02:18 140阅读 0赞

# 问题 #

今天一个项目需要在Linux中获取这些信息，查了一番资料得到了解答。

# 办法 #

接口名、ip、子网掩码、MAC通过`ioctl`接口获得，网关通过执行`route`指令，查询内核路由表获得：

#include <stdio.h>
    #include <string.h>
    #include <unistd.h>
    #include <net/if.h>
    #include <sys/ioctl.h>
    #include <arpa/inet.h>
    #include <errno.h>
    
    typedef struct interface_info_s
    { 
        char ifname[16];
        char ifnet[16];
        char ifnet6[40];
        char ifmask[16];
        char ifmac[18];
        char ifgateway[16];
    }interface_info_t;
    
    int get_default_gateway(char* gateway) 
    { 
        char cmd [128] = { 0};
        char line[256] = { 0};
        int len;
    
        sprintf(cmd,"route -n | grep 'UG[ \t]' | awk '{print $2}'");
        FILE* fp = popen(cmd, "r");
        if(fp == NULL)
        { 
            return -1;
        }
    
        fgets(line, sizeof(line), fp);
        len = strlen(line);
        memcpy(gateway, line, len);
        while (len > 0)
        { 
            if(gateway[len-1] == ' ' || gateway[len-1] == '\n')
            { 
                gateway[len-1] = '\0';
                --len;
            }
            else
            { 
                break;
            }
        }
    
        pclose(fp);
        return 0;
    }
    
    /** * @brief 获取网卡的地址、MAC、网关等各种信息 * * @param info 存储获取信息的位置 * @param info_size 存储信息结构体的大小 * @return int 获取的网卡数量 */
    int get_iface_info(interface_info_t *info, int info_size){ 
        int fd;
        int if_num = 0, i, j, t_len = 0;
        struct ifreq buf[16];
        struct ifreq ifrcopy;
        struct ifconf ifc;
    
        char mac[20] = { 0};
        char ip[32] = { 0};
        char subnetMask[32] = { 0};
        char gateway[32] = { 0};
    
        if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
        { 
            perror("socket");
            close(fd);
            return -1;
        }
    
        ifc.ifc_len = sizeof(buf);
        ifc.ifc_buf = (caddr_t)buf;
    
        if (ioctl(fd, SIOCGIFCONF, (char *)&ifc))
        { 
            printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
            close(fd);
            return -1;
        }
    
        if(get_default_gateway(gateway) < 0)
        { 
            return -1;
        }
    
        if_num = ifc.ifc_len / sizeof(struct ifreq);
        //printf("interface num = %d\n", if_num);
        
        for (i=0, t_len=0; i < if_num; i++)
        { 
            //printf("device name: %s\n", buf[i].ifr_name);
    
            //ignore the interface info that have same ifname in the list
            for(j = 0; j < t_len; j++)
            { 
                if(strcmp(buf[i].ifr_name, info[j].ifname) == 0)
                { 
                    break;
                }
            }
            if(j < t_len)
            { 
                continue;
            }
            else
            { 
                t_len++;
            }
            
            //return error code when data big than alloced memory
            if(t_len > info_size)
            { 
                return -2;
            }
            
            //get the name of this interface 
            strcpy(info[t_len-1].ifname, buf[i].ifr_name);
            
            //get the gateway of this interface 
            strcpy(info[t_len-1].ifgateway, gateway);
            
            //ignore the interface that not up or not runing 
            ifrcopy = buf[i];
            if (ioctl(fd, SIOCGIFFLAGS, &ifrcopy))
            { 
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
    
                close(fd);
                return -1;
            }
    
            //get the mac of this interface 
            if (!ioctl(fd, SIOCGIFHWADDR, (char *)(&buf[i])))
            { 
                memset(mac, 0, sizeof(mac));
                snprintf(mac, sizeof(mac), "%02x:%02x:%02x:%02x:%02x:%02x",
                    (unsigned char)buf[i].ifr_hwaddr.sa_data[0],
                    (unsigned char)buf[i].ifr_hwaddr.sa_data[1],
                    (unsigned char)buf[i].ifr_hwaddr.sa_data[2],
    
                    (unsigned char)buf[i].ifr_hwaddr.sa_data[3],
                    (unsigned char)buf[i].ifr_hwaddr.sa_data[4],
                    (unsigned char)buf[i].ifr_hwaddr.sa_data[5]);
                strcpy(info[t_len - 1].ifmac, mac);
                //printf("device mac: %s\n", mac);
            }
            else
            { 
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
    
            //get the IP of this interface 
            if (!ioctl(fd, SIOCGIFADDR, (char *)&buf[i]))
            { 
                snprintf(ip, sizeof(ip), "%s",
                    (char *)inet_ntoa(((struct sockaddr_in *)&(buf[i].ifr_addr))->sin_addr));
                strcpy(info[t_len - 1].ifnet, ip);
                //printf("device ip: %s\n", ip);
            }
            else
            { 
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
    
            //get the subnet mask of this interface 
            if (!ioctl(fd, SIOCGIFNETMASK, &buf[i]))
            { 
                snprintf(subnetMask, sizeof(subnetMask), "%s",
                    (char *)inet_ntoa(((struct sockaddr_in *)&(buf[i].ifr_netmask))->sin_addr));
                strcpy(info[t_len - 1].ifmask, subnetMask);
                //printf("device subnetMask: %s\n", subnetMask);
            }
            else
            { 
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
        }
        close(fd);
    
        return t_len;
    }
    
    int main(void)
    { 
        int len, i;
        interface_info_t if_info[16];
    
        len = get_iface_info(if_info, 16);
        
        for(i = 0; i < len; i++)
        { 
            printf("-----------\ndev name: %s\nip: %s\nmask: %s\nmac: %s\ngateway: %s\n", if_info[i].ifname,
                if_info[i].ifnet, if_info[i].ifmask, if_info[i].ifmac, if_info[i].ifgateway);
        }
    
        return 0;
    }

**存在的问题** ：  
代码中能看到我去除了同接口名的接口信息，其实同接口名出现是因为同一个接口赋予了多个ip地址，但是通过`ioctl`去读取获得的始终是第一个ip，因此我对其进行了过滤，如果你要获取同一个接口的多个ip地址，上面的代码会存在问题，当然如果你解决了这个问题，非常欢迎评论告知我改正，谢谢。

# 参考文章 #

1.  [Linux下C获取所有可用网卡信息][Linux_C]

[Linux_C]: https://www.cnblogs.com/fnlingnzb-learner/p/6427388.html