namespaces_netlink_test.c

namespaces_netlink_test.c

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#include <unistd.h>
#include <asm/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sched.h>

int main()
{
    pid_t pid;
    //int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_USERSOCK);
    unshare(CLONE_NEWPID);
    pid = fork();
    if (pid == -1) {
        perror("fork error");
        exit(-1);
    }
    if (pid == 0) {
        int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_USERSOCK);
        unshare(CLONE_NEWNS|CLONE_NEWNET);
        //system("mount -t none none /proc --make-private && mount -t proc proc /proc && ps");
        printf("child proc, pid=%lu\n", (long)getpid());
        if (sock == -1) {
            perror("socket error");
            return -1;
        }
        unshare(CLONE_NEWNET);
        struct sockaddr_nl sa;
        memset(&sa, 0, sizeof(sa));
        sa.nl_family = AF_NETLINK;
        sa.nl_groups = 0;
        int ret;
        printf("child proc: binding\n");
        ret = bind(sock, (struct sockaddr *)&sa, sizeof(sa));
        if (ret == -1) {
            perror("bind error\n");
            return -1;
        }
        int len;
        ret = getsockname(sock, (struct sockaddr *)&sa, &len);
        if (ret == -1) {
            perror("getsockname error\n");
            return -1;
        }
        printf("bind nl_pid=%lu\n", (long)sa.nl_pid);
        struct sockaddr_nl sa_remote;
        char buffer[4096];
        struct iovec iov = { buffer, sizeof(buffer) };
        struct msghdr msg = { &sa_remote, sizeof(sa_remote), &iov, 1, NULL, 0, 0 };
        struct nlmsghdr *nh;
        printf("waiting...\n");
        len = recvmsg(sock, &msg, 0);
        for (nh = (struct nlmsghdr *) buffer; NLMSG_OK(nh, len); nh = NLMSG_NEXT(nh, len)) {
            printf("type=%d\n", nh->nlmsg_type);
            const char *payload = buffer + sizeof(struct nlmsghdr);
            printf("payload: %s\n", payload);
        }
        return 0;
    }
    printf("parent proc\n");
    char buffer[4096];
    int fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_USERSOCK);
    if (fd == -1) {
            perror("socket error");
            return -1;
    }
    struct nlmsghdr *nh = (struct nlmsghdr *)buffer;
    nh->nlmsg_pid = pid;
    nh->nlmsg_len = 100;

    struct sockaddr_nl sa;
    memset(&sa, 0, sizeof(sa));
    sa.nl_family = AF_NETLINK;
    sa.nl_groups = 0;
    int ret = bind(fd, (struct sockaddr *)&sa, sizeof(sa));
    if (ret == -1) {
        perror("bind error");
        return -1;
    }
    
    struct sockaddr_nl sa_remote;
    memset(&sa_remote, 0, sizeof(sa_remote));
    sa_remote.nl_family = AF_NETLINK;
    sa_remote.nl_groups = 0;
    sa_remote.nl_pid = pid;

    struct iovec iov = { nh, nh->nlmsg_len };
    struct msghdr msg = { &sa_remote, sizeof(sa_remote), &iov, 1, NULL, 0, 0 };
    nh->nlmsg_pid = 0;
    nh->nlmsg_seq = 1234;
    nh->nlmsg_flags |= NLM_F_ACK;
    nh->nlmsg_type = 12345;
    char *payload = buffer + sizeof(struct nlmsghdr);
    strcpy(payload, "Hello world");
    sleep(1);
    printf("prepare to send\n");
    int len = sendmsg(fd, &msg, 0);
    if (len == -1) {
        perror("sendmsg error");
        return -1;
    }
    printf("sent %d\n", len);
    printf("waitpid\n");
    waitpid(pid, NULL, 0);
    return 0;
}