c++ - ethtool ioctl 返回未填充的 ethtool_link_settings

Question

我正在尝试使用 Ethtool ioctl API 从我的 NIC 检索链接速度数据，但我只是在 ethtool_link_settings 实例中取回零。使用 ethtool 命令行工具返回预期值，我的 NIC 驱动程序支持更新的 ETHTOOL_GLINKSETTINGS API。

#include <iostream>
#include <cstring>

#include <linux/ethtool.h>
#include <linux/sockios.h>
#include <netinet/in.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <unistd.h>

int main()
{
    auto ifn = if_nameindex();
    auto fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);

    for (auto i = ifn; i->if_name; ++i) {
        // Skip the loopback
        if (i->if_index == 1) {
            continue;
        }

        std::cout << "Testing: " << i->if_name << std::endl;

        auto ifr = ifreq{};
        std::strncpy(ifr.ifr_name, i->if_name, IF_NAMESIZE);

        auto msg = ethtool_link_settings{};
        msg.cmd = ETHTOOL_GLINKSETTINGS;
        ifr.ifr_data = reinterpret_cast<char*>(&msg);

        if (ioctl(fd, SIOCETHTOOL, &ifr) == -1) {
            std::cerr << "ioctl fail: " << strerror(errno) << std::endl;
        }

        std::cout << "\tSpeed: " << msg.speed
                  << "\n\tDuplex: " << static_cast<int>(msg.duplex)
                  << "\n\tPort: " << static_cast<int>(msg.port)
                  << std::endl;
    }

    close(fd);
    if_freenameindex(ifn);
    return EXIT_SUCCESS;
}

结果:

Testing: enp0s3
    Speed: 0
    Duplex: 0
    Port: 0
Testing: enp0s8
    Speed: 0
    Duplex: 0
    Port: 0
Testing: enp0s9
    Speed: 0
    Duplex: 0
    Port: 0
Testing: enp0s10
    Speed: 0
    Duplex: 0
    Port: 0

我确定我在做一些愚蠢的事情，但我看不到。

Answer 1

在 /usr/include/linux/ethtool.h 中 struct ethtool_link_settings 的 link_mode_masks_nwords 字段的注释中隐藏着一些令人钦佩的神秘评论说 ETHTOOL_GLINKSETTINGS 会进行一些握手，因此您需要多次调用它。

我已经使用 ethtool command 的代码调整了您的代码到执行 ETHTOOL_GLINKSETTINGS 命令:

#include <iostream>
#include <cstring>

#include <linux/ethtool.h>
#include <linux/sockios.h>
#include <linux/netlink.h>
#include <netinet/in.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <unistd.h>

int main()
{
    auto ifn = if_nameindex();
    auto fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);

    for (auto i = ifn; i->if_name; ++i) {
        struct {
                struct ethtool_link_settings req;
                __u32 link_mode_data[3 * 127];
            } ecmd;

        // Skip the loopback
        if (i->if_index == 1) {
            continue;
        }

        std::cout << "Testing: " << i->if_name << std::endl;

        auto ifr = ifreq{};
        std::strncpy(ifr.ifr_name, i->if_name, IF_NAMESIZE);

        ecmd.req.cmd = ETHTOOL_GLINKSETTINGS;
        ifr.ifr_data = reinterpret_cast<char*>(&ecmd);

        if (ioctl(fd, SIOCETHTOOL, &ifr) == -1) {
            std::cerr << "ioctl fail: " << strerror(errno) << std::endl;
            return 1;
        }

        if (ecmd.req.link_mode_masks_nwords >= 0 || ecmd.req.cmd != ETHTOOL_GLINKSETTINGS)
            return 1;

        ecmd.req.link_mode_masks_nwords = -ecmd.req.link_mode_masks_nwords;

        if (ioctl(fd, SIOCETHTOOL, &ifr) == -1) {
            std::cerr << "ioctl fail: " << strerror(errno) << std::endl;
            return 1;
        }

        std::cout << "\tSpeed: " << ecmd.req.speed
                  << "\n\tDuplex: " << static_cast<int>(ecmd.req.duplex)
                  << "\n\tPort: " << static_cast<int>(ecmd.req.port)
                  << std::endl;
    }

    close(fd);
    if_freenameindex(ifn);
    return EXIT_SUCCESS;
}