如何从C程序获取NIC详细信息？

获取所有接口的链接列表,然后使用ioctl(fd,SIOCGIFINDEX,struct ifreq *)获取每个接口的接口索引.由于接口是连续的并且总是列出(无论它们是否为(活动)),我选择使用ioctl(fd,SIOCGIFNAME,struct ifreq *)来循环枚举它们.在所有情况下,fd都是AF_INET套接字.

要获得接口的双工和速度,需要使用ioctl(fd,SIOCETHTOOL,struct ifreq *),ifr_data指向具有cmd = ETHTOOL_GSET的struct ethtool_cmd.

如果失败则ioctls应该返回-1,如果成功则返回非负值(零,我相信).

这是一个示例程序：

#include <unistd.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/ip.h>
#include <net/if.h>
#include <linux/ethtool.h>
#include <linux/sockios.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>

struct interface {
    int     index;
    int     flags;      /* IFF_UP etc. */
    long    speed;      /* Mbps; -1 is unknown */
    int     duplex;     /* DUPLEX_FULL, DUPLEX_HALF, or unknown */
    char    name[IF_NAMESIZE + 1];
};

static int get_interface_common(const int fd, struct ifreq *const ifr, struct interface *const info)
{
    struct ethtool_cmd  cmd;
    int                 result;

    /* Interface flags. */
    if (ioctl(fd, SIOCGIFFLAGS, ifr) == -1)
        info->flags = 0;
    else
        info->flags = ifr->ifr_flags;

    ifr->ifr_data = (void *)&cmd;
    cmd.cmd = ETHTOOL_GSET; /* "Get settings" */
    if (ioctl(fd, SIOCETHTOOL, ifr) == -1) {
        /* Unknown */
        info->speed = -1L;
        info->duplex = DUPLEX_UNKNOWN;
    } else {
        info->speed = ethtool_cmd_speed(&cmd);
        info->duplex = cmd.duplex;
    }

    do {
        result = close(fd);
    } while (result == -1 && errno == EINTR);
    if (result == -1)
        return errno;

    return 0;
}

int get_interface_by_index(const int index, struct interface *const info)
{
    int             socketfd, result;
    struct ifreq    ifr;

    if (index < 1 || !info)
        return errno = EINVAL;

    socketfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
    if (socketfd == -1)
        return errno;

    ifr.ifr_ifindex = index;
    if (ioctl(socketfd, SIOCGIFNAME, &ifr) == -1) {
        do {
            result = close(socketfd);
        } while (result == -1 && errno == EINTR);
        return errno = ENOENT;
    }

    info->index = index;
    strncpy(info->name, ifr.ifr_name, IF_NAMESIZE);
    info->name[IF_NAMESIZE] = '\0';

    return get_interface_common(socketfd, &ifr, info);
}

int get_interface_by_name(const char *const name, struct interface *const info)
{
    int             socketfd, result;
    struct ifreq    ifr;

    if (!name || !*name || !info)
        return errno = EINVAL;

    socketfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
    if (socketfd == -1)
        return errno;

    strncpy(ifr.ifr_name, name, IF_NAMESIZE);
    if (ioctl(socketfd, SIOCGIFINDEX, &ifr) == -1) {
        do {
            result = close(socketfd);
        } while (result == -1 && errno == EINTR);
        return errno = ENOENT;
    }

    info->index = ifr.ifr_ifindex;
    strncpy(info->name, name, IF_NAMESIZE);
    info->name[IF_NAMESIZE] = '\0';

    return get_interface_common(socketfd, &ifr, info);
}

int main(int argc, char *argv[])
{
    struct interface    iface;
    int                 arg;
    int                 status = 0;

    if (argc > 1 && (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help"))) {
        fprintf(stderr, "\n");
        fprintf(stderr, "Usage: %s { -h | --help }\n", argv[0]);
        fprintf(stderr, "       %s\n", argv[0]);
        fprintf(stderr, "       %s INTERFACE ...\n", argv[0]);
        fprintf(stderr, "\n");
        return 1;
    }

    if (argc > 1) {
        for (arg = 1; arg < argc; arg++) {
            if (get_interface_by_name(argv[arg], &iface) != 0) {
                fprintf(stderr, "%s: No such interface.\n", argv[arg]);
                status = 1;
                continue;
            }

            printf("%s: Interface %d", iface.name, iface.index);
            if (iface.flags & IFF_UP)
                printf(", up");
            if (iface.duplex == DUPLEX_FULL)
                printf(", full duplex");
            else
            if (iface.duplex == DUPLEX_HALF)
                printf(", half duplex");
            if (iface.speed > 0)
                printf(", %ld Mbps", iface.speed);
            printf("\n");
        }

    } else {
        for (arg = 1; ; arg++) {
            if (get_interface_by_index(arg, &iface) != 0)
                break;

            printf("%s: Interface %d", iface.name, iface.index);
            if (iface.flags & IFF_UP)
                printf(", up");
            if (iface.duplex == DUPLEX_FULL)
                printf(", full duplex");
            else
            if (iface.duplex == DUPLEX_HALF)
                printf(", half duplex");
            if (iface.speed > 0)
                printf(", %ld Mbps", iface.speed);
            printf("\n");
        }
    }

    return status;
}

如果将上面保存为iflist.c,则可以使用它进行编译

gcc -W -Wall -O3 iflist.c -o iflist

要查看用法,请运行iflist -h.要列出所有接口,请运行它而不带参数：

./iflist

以上将使用我描述的枚举方法.要仅列出特定接口,请运行命名接口：

./iflist eth0 lo

当然,仅为以太网接口列出双工和速度.

编辑添加：

如果上述程序没有为接口提供带宽和模式,这里有一个简化版本,它报告确切原因(错误).这个接口名称作为命令行参数;它没有枚举接口.

#include <unistd.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/ip.h>
#include <net/if.h>
#include <linux/ethtool.h>
#include <linux/sockios.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>

int ethernet_interface(const char *const name,
                       int *const index, int *const speed, int *const duplex)
{
    struct ifreq        ifr;
    struct ethtool_cmd  cmd;
    int                 fd, result;

    if (!name || !*name) {
        fprintf(stderr, "Error: NULL interface name.\n");
        fflush(stderr);
        return errno = EINVAL;
    }

    if (index)  *index = -1;
    if (speed)  *speed = -1;
    if (duplex) *duplex = -1;

    fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd == -1) {
        const int err = errno;
        fprintf(stderr, "%s: Cannot create AF_INET socket: %s.\n", name, strerror(err));
        fflush(stderr);
        return errno = err;
    }

    strncpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
    ifr.ifr_data = (void *)&cmd;
    cmd.cmd = ETHTOOL_GSET;
    if (ioctl(fd, SIOCETHTOOL, &ifr) < 0) {
        const int err = errno;
        do {
            result = close(fd);
        } while (result == -1 && errno == EINTR);
        fprintf(stderr, "%s: SIOCETHTOOL ioctl: %s.\n", name, strerror(err));
        return errno = err;
    }

    if (speed)
        *speed = ethtool_cmd_speed(&cmd);

    if (duplex)
        switch (cmd.duplex) {
        case DUPLEX_HALF: *duplex = 0; break;
        case DUPLEX_FULL: *duplex = 1; break;
        default:
            fprintf(stderr, "%s: Unknown mode (0x%x).\n", name, cmd.duplex);
            fflush(stderr);
            *duplex = -1;
        }

    if (index && ioctl(fd, SIOCGIFINDEX, &ifr) >= 0)
        *index = ifr.ifr_ifindex;

    do {
        result = close(fd);
    } while (result == -1 && errno == EINTR);
    if (result == -1) {
        const int err = errno;
        fprintf(stderr, "%s: Error closing socket: %s.\n", name, strerror(err));
        return errno = err;
    }

    return 0;
}

int main(int argc, char *argv[])
{
    int  arg, speed, index, duplex;

    if (argc < 2 || !strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
        fprintf(stderr, "\n");
        fprintf(stderr, "Usage: %s [ -h | --help ]\n", argv[0]);
        fprintf(stderr, "       %s INTERFACE ...\n", argv[0]);
        fprintf(stderr, "\n");
        return 0;
    }

    for (arg = 1; arg < argc; arg++) {
        if (ethernet_interface(argv[arg], &index, &speed, &duplex))
            return 1;

        if (index == -1)
            printf("%s: (no interface index)", argv[arg]);
        else
            printf("%s: interface %d", argv[arg], index);

        if (speed == -1)
            printf(", unknown bandwidth");
        else
            printf(", %d Mbps bandwidth", speed);

        if (duplex == 0)
            printf(", half duplex.\n");
        else if (duplex == 1)
            printf(", full duplex.\n");
        else
            printf(", unknown mode.\n");
    }

    return 0;
}

有问题吗？