run-lxc.c

/*
 * Copyright (C) 2013 Aaron Brady
 * Copyright (C) 2008-2012 Red Hat, Inc.
 * Copyright (C) 2008 IBM Corp.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <sched.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <mntent.h>
#include <string.h>
#include <strings.h>
#ifdef __dietlibc__
#include "/usr/include/linux/sched.h"
#endif

extern int pivot_root(const char * new_root,const char * put_old);

static int lxcContainerChildMountSort(const void *a, const void *b) {
    const char **sa = (const char**)a;
    const char **sb = (const char**)b;

    /* Deliberately reversed args - we need to unmount deepest
       children first */
    return strcmp(*sb, *sa);
}

void unmount_old(void) {
    struct mntent *mntent;
    char **mounts = NULL;
    int nmounts = 0;
    FILE *procmnt;
    int i;
    int saveErrno;
    const char *failedUmount = NULL;
    int ret = -1;

    procmnt = setmntent("/proc/mounts", "r");
    mounts = malloc(250);
    while (mntent = getmntent(procmnt)) {
        if (strncmp(mntent->mnt_dir, "/.old", 4) != 0)
            continue;
        mounts[nmounts++] = strdup(mntent->mnt_dir);
    }
    if (mounts)
        qsort(mounts, nmounts, sizeof(mounts[0]),
              lxcContainerChildMountSort);

    for (i = 0 ; i < nmounts ; i++) {
        umount(mounts[i]);
    }
    umount("/.old");
}

int child(void *n) {
    char buf[BUFSIZ] = {0};
    char buf2[BUFSIZ] = {0};
    snprintf(buf, BUFSIZ, "/lxc/%s/.old", n);
    mkdir(buf, 0700);
    snprintf(buf2, BUFSIZ, "/lxc/%s", n);
    pivot_root(buf2, buf);
    chdir("/");
    mount("/proc", "/proc", "proc", 0, NULL);
    close(2);
    close(1);
    close(0);
    unmount_old();
    mount("devpts", "/dev/pts", "devpts", 0, "newinstance,ptmxmode=0666,mode=0620,gid=5");
    execl("/sbin/init", "/sbin/init", (char *)NULL);
    perror(NULL);
    return 0;
}

void main(int c, char **v) {
    int cflags;
    int stacksize = getpagesize() * 4;
    char *stack, *stacktop;
    char buf[BUFSIZ] = {0}; // Bless me Father, for I have sinned.
    int ptmx;
    int unlock = 0;
    int ptyno;
    pid_t pid;
    void *pointer;
    int val;

    cflags = CLONE_NEWPID|CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC|SIGCHLD|CLONE_NEWNET;

    stack = (char *)malloc(stacksize);
    stacktop = stack + stacksize;

    pointer = malloc(BUFSIZ);
    bzero(pointer, BUFSIZ);
    strcpy(pointer, v[1]);

    snprintf(buf, BUFSIZ, "ip link add name %s type veth peer name slave", v[1]);
    system(buf);
    snprintf(buf, BUFSIZ, "ip link set dev %s up", v[1]);
    system(buf);
    snprintf(buf, BUFSIZ, "brctl addif br1 %s", v[1]);
    system(buf);
    sleep(5); // Give the bridge a chance to spin up
    pid = clone(child, stacktop, cflags, pointer);
    snprintf(buf, BUFSIZ, "ip link set slave netns %d", pid);
    system(buf);
}