Linux下ipconfig分析及C语言实现

来源：互联网发布：windows优化大师下载编辑：程序博客网时间：2024/05/27 20:52

在linux下使用ifconfigl命令能很方便的查看网卡与网线是否连通，运行ifconfig eth0命令大致输出如下：

# ifconfig eth0eth0      Link encap:Ethernet  HWaddr 00:25:35:68:CC:D6            inet addr:192.168.1.168  Bcast:192.168.1.255  Mask:255.255.255.0          inet6 addr: fe80::215:c5ff:fe18:ccd6/64 Scope:Link          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1          RX packets:130722 errors:0 dropped:0 overruns:0 frame:0          TX packets:112560 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:1000           RX bytes:104371099 (99.5 MiB)  TX bytes:20518584 (19.5 MiB)          Interrupt:16

其中的RUNNING就表示网卡与网线正常链接，拔掉网线再运行此命令就会发现RUNNING不在了。

我的目的是用C语言来实现程序，而linux系统提供了popen/pclose进程管道让C和shell很方便的交互，不过使用的时候要注意设置权限，以免造成安全隐患。废话不多说，看下面C代码结合shell命令检测网卡与网线连通状况：
netstat.c

#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <string.h>/*********************************************************************** 函数名称： GetNetStat* 功能描述： 检测网络链接是否断开* 输入参数： * 输出参数： 无* 返 回 值： 正常链接1,断开返回-1* 其它说明： 本程序需要超级用户权限才能成功调用ifconfig命令* 修改日期        版本号     修改人          修改内容* ---------------------------------------------------------------------* 2010/04/02      V1.0      eden_mgqw***********************************************************************/ int GetNetStat( ){    char    buffer[BUFSIZ];    FILE    *read_fp;    int        chars_read;    int        ret;        memset( buffer, 0, BUFSIZ );    read_fp = popen("ifconfig eth0 | grep RUNNING", "r");    if ( read_fp != NULL )     {        chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);        if (chars_read > 0)         {            ret = 1;        }        else        {            ret = -1;        }        pclose(read_fp);    }    else    {        ret = -1;    }    return ret;}int main(){    int i=0;    i = GetNetStat();    printf( "\nNetStat = %d\n", i );    return 0;}

下面是编译运行程序的输出结果（正常返回1，断开返回-1）：
# cc netstat.c
# ./a.out
NetStat = 1

C语言实现：

    #include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>#include <string.h>#include <ctype.h>#include <sys/socket.h>#include <netinet/in.h>#include <linux/if.h>#include <linux/sockios.h>#include <arpa/inet.h>static void die(const char *s){    fprintf(stderr,"error: %s (%s)\n", s, strerror(errno));    exit(-1);}static void setflags(int s, struct ifreq *ifr, int set, int clr){    if(ioctl(s, SIOCGIFFLAGS, ifr) < 0) die("SIOCGIFFLAGS");    ifr->ifr_flags = (ifr->ifr_flags & (~clr)) | set;    if(ioctl(s, SIOCSIFFLAGS, ifr) < 0) die("SIOCSIFFLAGS");}static inline void init_sockaddr_in(struct sockaddr_in *sin, const char *addr){    sin->sin_family = AF_INET;    sin->sin_port = 0;    sin->sin_addr.s_addr = inet_addr(addr);}static void setmtu(int s, struct ifreq *ifr, const char *mtu){    int m = atoi(mtu);    ifr->ifr_mtu = m;    if(ioctl(s, SIOCSIFMTU, ifr) < 0) die("SIOCSIFMTU");}static void setdstaddr(int s, struct ifreq *ifr, const char *addr){    init_sockaddr_in((struct sockaddr_in *) &ifr->ifr_dstaddr, addr);    if(ioctl(s, SIOCSIFDSTADDR, ifr) < 0) die("SIOCSIFDSTADDR");}static void setnetmask(int s, struct ifreq *ifr, const char *addr){    init_sockaddr_in((struct sockaddr_in *) &ifr->ifr_netmask, addr);    if(ioctl(s, SIOCSIFNETMASK, ifr) < 0) die("SIOCSIFNETMASK");}static void setaddr(int s, struct ifreq *ifr, const char *addr){    init_sockaddr_in((struct sockaddr_in *) &ifr->ifr_addr, addr);    if(ioctl(s, SIOCSIFADDR, ifr) < 0) die("SIOCSIFADDR");}int main(int argc, char *argv[]){    struct ifreq ifr;    int s;    unsigned int addr, mask, flags;    char astring[20];    char mstring[20];    char *updown, *brdcst, *loopbk, *ppp, *running, *multi;    argc--;    argv++;    if(argc == 0) return 0;    memset(&ifr, 0, sizeof(struct ifreq));    strncpy(ifr.ifr_name, argv[0], IFNAMSIZ);    ifr.ifr_name[IFNAMSIZ-1] = 0;    argc--, argv++;    if((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {        die("cannot open control socket\n");    }    if (argc == 0) {        if (ioctl(s, SIOCGIFADDR, &ifr) < 0) {            perror(ifr.ifr_name);            return -1;        } else            addr = ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr.s_addr;        if (ioctl(s, SIOCGIFNETMASK, &ifr) < 0) {            perror(ifr.ifr_name);            return -1;        } else            mask = ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr.s_addr;        if (ioctl(s, SIOCGIFFLAGS, &ifr) < 0) {            perror(ifr.ifr_name);            return -1;        } else            flags = ifr.ifr_flags;        sprintf(astring, "%d.%d.%d.%d",                addr & 0xff,                ((addr >> 8) & 0xff),                ((addr >> 16) & 0xff),                ((addr >> 24) & 0xff));        sprintf(mstring, "%d.%d.%d.%d",                mask & 0xff,                ((mask >> 8) & 0xff),                ((mask >> 16) & 0xff),                ((mask >> 24) & 0xff));        printf("%s: ip %s mask %s flags [", ifr.ifr_name,               astring,               mstring               );        updown =  (flags & IFF_UP)           ? "up" : "down";        brdcst =  (flags & IFF_BROADCAST)    ? " broadcast" : "";        loopbk =  (flags & IFF_LOOPBACK)     ? " loopback" : "";        ppp =     (flags & IFF_POINTOPOINT)  ? " point-to-point" : "";        running = (flags & IFF_RUNNING)      ? " running" : "";        multi =   (flags & IFF_MULTICAST)    ? " multicast" : "";        printf("%s%s%s%s%s%s]\n", updown, brdcst, loopbk, ppp, running, multi);        return 0;    }    while(argc > 0) {        if (!strcmp(argv[0], "up")) {            setflags(s, &ifr, IFF_UP, 0);        } else if (!strcmp(argv[0], "mtu")) {            argc--, argv++;            if (!argc) {                errno = EINVAL;                die("expecting a value for parameter \"mtu\"");            }            setmtu(s, &ifr, argv[0]);        } else if (!strcmp(argv[0], "-pointopoint")) {            setflags(s, &ifr, IFF_POINTOPOINT, 1);        } else if (!strcmp(argv[0], "pointopoint")) {            argc--, argv++;            if (!argc) {                errno = EINVAL;                die("expecting an IP address for parameter \"pointtopoint\"");            }            setdstaddr(s, &ifr, argv[0]);            setflags(s, &ifr, IFF_POINTOPOINT, 0);        } else if (!strcmp(argv[0], "down")) {            setflags(s, &ifr, 0, IFF_UP);        } else if (!strcmp(argv[0], "netmask")) {            argc--, argv++;            if (!argc) {                errno = EINVAL;                die("expecting an IP address for parameter \"netmask\"");            }            setnetmask(s, &ifr, argv[0]);        } else if (isdigit(argv[0][0])) {            setaddr(s, &ifr, argv[0]);            setflags(s, &ifr, IFF_UP, 0);        }        argc--, argv++;    }    return 0;}