使用ioctl获取网卡统计信息

ethtool -S获取接口统计信息总共分三步：

1、获取统计项个数，使用SIOCETHTOOL+ETHTOOL_GSSET_INFO

2、（可选）获取统计项名字，使用SIOCETHTOOL+ETHTOOL_GSTRINGS，需要使用第1步中获取的统计项个数来申请足够大的内存

3、获取统计值，使用SIOCETHTOOL+ETHTOOL_GSTATS，需要使用第1步中获取的统计项个数来申请足够大的内存

上代码：

#include <sys/types.h>
#include <string.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <net/if.h>

#include <linux/sockios.h>
#include <linux/ethtool.h>

int main(int argc, char* argv[])
{
    int fd;
    int ret;
    unsigned int n_stats, i;
    struct ifreq ifr;
    struct {
                struct ethtool_sset_info hdr;
                unsigned int buf[1];
        } sset_info;
    struct ethtool_stats *stats;
    struct ethtool_gstrings *strings;
    unsigned int sz_stats;

    fd = socket(AF_INET, SOCK_DGRAM, 0);

    sset_info.hdr.cmd = ETHTOOL_GSSET_INFO;
        sset_info.hdr.reserved = 0;
        sset_info.hdr.sset_mask = 1ULL << ETH_SS_STATS;

    memset(&ifr, 0, sizeof(ifr));
    strcpy(ifr.ifr_name, "eth2");
    ifr.ifr_data = (void*)&sset_info;
    ret = ioctl(fd, SIOCETHTOOL, &ifr);
    if (0 != ret) {
        printf("ETHTOOL_GSSET_INFO errno=%d
", errno);
        return -1;
    }

    n_stats = sset_info.hdr.sset_mask ? sset_info.hdr.data[0] : 0;
    printf("stats n_stats=%d
", n_stats);

    /*strings = calloc(1, sizeof(*strings) + n_stats * ETH_GSTRING_LEN);
        if (!strings)
                return -1;

        strings->cmd = ETHTOOL_GSTRINGS;
        strings->string_set = ETH_SS_STATS;
        strings->len = n_stats;

    memset(&ifr, 0, sizeof(ifr));
        strcpy(ifr.ifr_name, "eth2");
    ifr.ifr_data = (void*)strings;
    ret = ioctl(fd, SIOCETHTOOL, &ifr);
    if (0 != ret) {
        printf("ETH_SS_STATS, errno=%d
", errno);
        return -1;
    }
    */
    sz_stats = n_stats * sizeof(unsigned long long);
    stats = calloc(1, sz_stats + sizeof(struct ethtool_stats));
    stats->cmd = ETHTOOL_GSTATS;
    stats->n_stats = n_stats;

    memset(&ifr, 0, sizeof(ifr));
    strcpy(ifr.ifr_name, "eth2");
    ifr.ifr_data = (void*)stats;
    ret = ioctl(fd, SIOCETHTOOL, &ifr);
    if (0 != ret) {
        printf("ETHTOOL_GSTATS errno=%d
", errno);
        return -1;
    }

    for (i = 0; i < n_stats; i++) {
                printf("%llu
", stats->data[i]);
    }

    return 0;
}