linux如何创建PF_NETLINK协议通信,写出服务端和客户端

PF_NETLINK是Linux内核提供的一种用于内核与用户空间进程之间通信的协议。下面是一个简单的PF_NETLINK服务端和客户端的示例代码：

服务端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/netlink.h>

#define NETLINK_TEST 25
#define MSG_LEN 100

int main(int argc, char *argv[]) {
    int skfd;
    struct sockaddr_nl saddr, daddr;
    struct nlmsghdr *nlh = NULL;
    struct iovec iov;
    struct msghdr msg;
    char msg_buf[MSG_LEN];

    // 创建socket
    skfd = socket(AF_NETLINK, SOCK_RAW, NETLINK_TEST);
    if (skfd == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 绑定源地址
    memset(&saddr, 0, sizeof(saddr));
    saddr.nl_family = AF_NETLINK;
    saddr.nl_pid = getpid();
    saddr.nl_groups = 0;
    if (bind(skfd, (struct sockaddr *)&saddr, sizeof(saddr)) != 0) {
        perror("bind");
        close(skfd);
        exit(EXIT_FAILURE);
    }

    // 初始化目标地址
    memset(&daddr, 0, sizeof(daddr));
    daddr.nl_family = AF_NETLINK;
    daddr.nl_pid = 0;  // 目标地址为内核
    daddr.nl_groups = 0;

    // 构造netlink消息
    nlh = (struct nlmsghdr *)msg_buf;
    nlh->nlmsg_len = NLMSG_LENGTH(strlen("Hello from kernel!"));
    nlh->nlmsg_pid = getpid();
    nlh->nlmsg_flags = 0;
    strcpy(NLMSG_DATA(nlh), "Hello from kernel!");

    // 设置iov
    iov.iov_base = (void *)nlh;
    iov.iov_len = nlh->nlmsg_len;

    // 设置msghdr
    memset(&msg, 0, sizeof(msg));
    msg.msg_name = (void *)&daddr;
    msg.msg_namelen = sizeof(daddr);
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    // 发送消息
    if (sendmsg(skfd, &msg, 0) == -1) {
        perror("sendmsg");
        close(skfd);
        exit(EXIT_FAILURE);
    }

    printf("Kernel message sent.\n");

    close(skfd);

    return 0;
}

客户端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/netlink.h>

#define NETLINK_TEST 25
#define MSG_LEN 100

int main(int argc, char *argv[]) {
    int skfd;
    struct sockaddr_nl saddr, daddr;
    struct nlmsghdr *nlh = NULL;
    struct iovec iov;
    struct msghdr msg;
    char msg_buf[MSG_LEN];

    // 创建socket
    skfd = socket(AF_NETLINK, SOCK_RAW, NETLINK_TEST);
    if (skfd == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 初始化源地址
    memset(&saddr, 0, sizeof(saddr));
    saddr.nl_family = AF_NETLINK;
    saddr.nl_pid = getpid();
    saddr.nl_groups = 0;

    // 绑定源地址
    if (bind(skfd, (struct sockaddr *)&saddr, sizeof(saddr)) != 0) {
        perror("bind");
        close(skfd);
        exit(EXIT_FAILURE);
    }

    // 初始化目标地址
    memset(&daddr, 0, sizeof(daddr));
    daddr.nl_family = AF_NETLINK;
    daddr.nl_pid = 0;  // 目标地址为内核
    daddr.nl_groups = 0;

    // 构造netlink消息
    nlh = (struct nlmsghdr *)msg_buf;
    nlh->nlmsg_len = NLMSG_SPACE(MSG_LEN);
    nlh->nlmsg_pid = getpid();
    nlh->nlmsg_flags = 0;
    strcpy(NLMSG_DATA(nlh), "Hello from user space!");

    // 设置iov
    iov.iov_base = (void *)nlh;
    iov.iov_len = nlh->nlmsg_len;

    // 设置msghdr
    memset(&msg, 0, sizeof(msg));
    msg.msg_name = (void *)&daddr;
    msg.msg_namelen = sizeof(daddr);
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    // 发送消息
    if (sendmsg(skfd, &msg, 0) == -1) {
        perror("sendmsg");
        close(skfd);
        exit(EXIT_FAILURE);
    }

    printf("User message sent.\n");

    // 接收消息
    memset(&msg, 0, sizeof(msg));
    msg.msg_name = (void *)&saddr;
    msg.msg_namelen = sizeof(saddr);
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    if (recvmsg(skfd, &msg, 0) == -1) {
        perror("recvmsg");
        close(skfd);
        exit(EXIT_FAILURE);
    }

    printf("Received message from kernel: %s\n", (char *)NLMSG_DATA(nlh));

    close(skfd);

    return 0;
}

运行上述服务端和客户端代码即可进行PF_NETLINK通信。注意需要以root权限运行程序。