编程以获取/设置Linux系统的网络信息

说明：文章代码整理自网上其它资料。

1. 获取IP地址、子网掩码地址、Mac地址、广播地址

#include <stdio.h>
#include <string.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <errno.h>

int GetNetworkInfo(void)
{
    int fd;
    int interfaceNum = 0;
    struct ifreq buf[16];
    struct ifconf ifc;
    struct ifreq ifrcopy;
    char mac[32] = {0};
    char ip[32] = {0};
    char broadAddr[32] = {0};
    char subnetMask[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;
    /* 执行完这句后ifc.ifc_len已经不一定就等于sizeof(buf)，而是小于或等于sizeof(buf)，取决于网卡的个数 */

    if (!ioctl(fd, SIOCGIFCONF, (char *)&ifc))
    {
        interfaceNum = ifc.ifc_len / sizeof(struct ifreq);
        while (interfaceNum-- > 0)
        {             
            ifrcopy = buf[interfaceNum];
            if (ioctl(fd, SIOCGIFFLAGS, &ifrcopy))
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }

            //获取IP地址
            if (!ioctl(fd, SIOCGIFADDR, (char *)&buf[interfaceNum]))
            {
                snprintf(ip, sizeof(ip), "%s",
                            (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_addr))->sin_addr));
                printf("device ip: %s\n", ip);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
            //获取子网掩码地址
            if (!ioctl(fd, SIOCGIFNETMASK, &buf[interfaceNum]))
            {
                snprintf(subnetMask, sizeof(subnetMask), "%s",
                            (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_netmask))->sin_addr));
                printf("device subnetMask: %s\n", subnetMask);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
            //获取mac地址
            if (!ioctl(fd, SIOCGIFHWADDR, (char *)(&buf[interfaceNum])))
            {
                memset(mac, 0, sizeof(mac));
                snprintf(mac, sizeof(mac), "%02x:%02x:%02x:%02x:%02x:%02x",
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[0],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[1],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[2],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[3],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[4],
                (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[5]);
                printf("device mac: %s\n", mac);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
            //获取广播地址
            if (!ioctl(fd, SIOCGIFBRDADDR, &buf[interfaceNum]))
            {
                snprintf(broadAddr, sizeof(broadAddr), "%s",
                            (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_broadaddr))->sin_addr));
                printf("device broadAddr: %s\n", broadAddr);
            }
            else
            {
                printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
                close(fd);
                return -1;
            }
        }
    }
    else
    {
        printf("ioctl: %s [%s:%d]\n", strerror(errno), __FILE__, __LINE__);
        close(fd);
        return -1;
    }
    close(fd);
    return 0;
}

2. 设置IP地址、子网掩码、网关地址

#include <sys/types.h>    
#include <sys/socket.h>    
#include <netinet/in.h>    
#include <net/if.h>    
#include <sys/ioctl.h>    
#include <errno.h>    
#include <string.h>    
#include <net/route.h>    
#include <unistd.h>    
#include <stdio.h> 

int SetNetworkInfo(const char *ifname, const char *ipaddr, const char *netmask, const char *gwip)
{
    struct sockaddr_in sin;
    struct ifreq ifr;
    int fd;

    bzero(&ifr, sizeof(struct ifreq));

    if (!ifname == NULL || !ipaddr || !gwip) return -1;
    fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd == -1)
    {
        perror("Not create network socket connection\n");
        return -1;
    }

    //设置IP地址
    strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
    ifr.ifr_name[IFNAMSIZ   -   1]   =   0;
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr(ipaddr);
    memcpy(&ifr.ifr_addr, &sin, sizeof(sin));
    if (ioctl(fd, SIOCSIFADDR, &ifr) < 0)
    {
        perror( "Not setup interface\n ");
        return -1;
    }

    //设置子网掩码
    bzero(&ifr, sizeof(struct ifreq));
    strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
    ifr.ifr_name[IFNAMSIZ   -   1]   =   0;
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr(netmask);
    memcpy(&ifr.ifr_addr, &sin, sizeof(sin));
    if(ioctl(fd, SIOCSIFNETMASK, &ifr ) < 0)
    {
        perror("net mask ioctl error\n");
        return -1;
    }

    //设置网关地址
    struct rtentry rm;
    bzero(&rm, sizeof(struct rtentry));
    rm.rt_dst.sa_family = AF_INET;
    rm.rt_gateway.sa_family = AF_INET;
    rm.rt_genmask.sa_family = AF_INET;
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr(gwip);
    memcpy(&rm.rt_gateway, &sin, sizeof(sin)); 
    rm.rt_dev = (char *)ifname;
    rm.rt_flags = RTF_UP | RTF_GATEWAY ;
    if(ioctl(fd, SIOCADDRT, &rm ) < 0)
    {
        perror("gateway ioctl error\n");
        return -1;
    }

    //激活接口
    ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
    if (ioctl(fd, SIOCSIFFLAGS, &ifr) < 0)
    {
        perror("SIOCSIFFLAGS");
        return -1;
    }

    return 0;
}