nomadinit.c

/*=============================================================================
 |       Author:  John Boero - jboero@hashicorp.com
 |  Description:  Simple custom init poc for Hashicorp NomadOS. 
 *===========================================================================*/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/wait.h>
#include <net/if.h>

void mounter(const char * src, const char *dst, const char * type, int rwflag, const char *data)
{
    if (!mount(src, dst, type, rwflag, data))
        printf("Mounted: %s\n", dst);
    else
        printf("ERROR:   %s: %s\n", strerror(errno), dst);
}

int ifup(char *ifname)
{
    int sockfd;
    struct ifreq ifr;

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    if (sockfd < 0)
        return sockfd;

    memset(&ifr, 0, sizeof ifr);

    strncpy(ifr.ifr_name, ifname, IFNAMSIZ);

    ifr.ifr_flags |= IFF_UP;
    ioctl(sockfd, SIOCSIFFLAGS, &ifr);

    printf("IFUP: %s\n", ifname);
    return sockfd;
}

int main()
{
    // Remount root read/write
    mounter("",           "/",                "",         MS_REMOUNT, "discard");

    mkdir("/dev",           S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mkdir("/dev/pts",       S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("devpts",     "/dev/pts",         "devpts",   0, "");
    mkdir("/dev/hugepages", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mkdir("/dev/mqueue",    S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("mqueue",     "/dev/mqueue",      "mqueue",   0, "");
    mkdir("/dev/pts",       S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("devpts",     "/dev/pts",         "devpts",   0, "");
    mkdir("/dev/kernel",    S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mkdir("/dev/kernel/debug", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("debugfs",     "/dev/kernel/debug","debugfs", 0, "");
    mounter("tracefs",     "/sys/kernel/tracing","tracefs", 0, "");
    mkdir("/proc",          S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("proc",       "/proc",            "proc",      0, "");
    mkdir("/proc/sys",      S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mkdir("/proc/sys/fs",   S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mkdir("/proc/sys/fs/binfmt_misc", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("binfmt_misc","/proc/sys/fs/binfmt_misc","binfmt_misc",
        MS_NODEV | MS_NOEXEC | MS_NOEXEC, "");

    mkdir("/tmp",         S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("tmpfs",      "/tmp",             "tmpfs",     0, "");
    mkdir("/sys",         S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("sysfs",      "/sys",             "sysfs",     0, "");
    mkdir("/sys/fs",      S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("selinuxfs",  "/sys/fs/selinux",  "selinuxfs", 0, "");
    mkdir("/sys/fs/cgroup",      S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    mounter("cgroup",  "/sys/fs/cgroup",  "cgroup2", 0, "");

    // Set default hostname in case DHCP doesn't set it.
    sethostname("nomados", 7);
    while (1)
    {
        pid_t child = fork();
        if (child == -1) {
            perror("init: fork");
            return 1;
        }
        else if (child == 0)
        {
            ifup("lo");
            ifup("eth0");
            setenv("PATH", "/sbin:/usr/sbin:/usr/bin:/bin:/usr/local/bin", 1);
            system("/sbin/sdhcp eth0 || echo DHCP Failure");
            system("/usr/sbin/ip a");
            system("cat /etc/resolv.conf");
			//system("/usr/bin/podman system service -t 0&");
            system("/usr/bin/nomad agent -dev -config=/etc/nomad/init.json >/var/log/nomad.log 2>/var/log/nomad.err&");
            // Only enable shell for debugging.
			system("/usr/bin/bash");
        }
        while (1)
        {
            // TODO should handle signals, acpi events, etc.
            sleep(1);
            wait(0);
        }
    }
    return 0;
}