#!/usr/bin/python2
import os
import subprocess

def read_elf_class(elf_file):
    import struct
    f = open(elf_file, "rb")
    f.seek(4)
    elf_class = f.read(1)
    f.close()
    elf_class = struct.unpack('B', elf_class)[0]
    return elf_class

def exec_chroot_cmd(args, chroot, pre_chroot = [], mount_vfs = True):
    pid = os.fork()
    if pid == 0:
        os.chroot(chroot)
        os.chdir("/")
        myargs = pre_chroot+args
        rc = subprocess.call(myargs)
        if mount_vfs:
            subprocess.call(("mount", "-t", "proc", "proc", "/proc"))
            subprocess.call(("mount", "-t", "devpts", "devpts", "/dev/pts"))
        os._exit(rc)
    else:
        rc_pid, rc = os.waitpid(pid, 0)
        return rc_pid, rc

def spawn_ssh(args, chroot):

    # bind /proc and /dev
    for path in []:
        b_args = ["mount", "--bind", path, os.path.join(chroot, path[1:])]
        subprocess.call(b_args)

    bash_exec = os.path.join(chroot, "bin/bash") # must exists
    elf_class = read_elf_class(bash_exec)
    pre_chroot = []
    if elf_class != 2: # 32 bit
        pre_chroot = ["linux32"]
    rc_pid, rc = exec_chroot_cmd(args, chroot, pre_chroot = pre_chroot)
    return rc_pid, rc


if __name__ == "__main__":

    start_port = 2000
    chroot_dir = "/sabayon/sources"
    chroots = os.listdir(chroot_dir)
    default_args = ["/usr/sbin/sshd"]
    chroot_map_file = "/sabayon/CHROOTS"

    ch_f = open(chroot_map_file, "w")
    ch_f.write("Sabayon Chroots available via SSH:\n")
    for chroot in chroots:
        if not os.path.isdir(os.path.join(chroot_dir, chroot)):
            continue
        print("starting chroot %s, ssh at localhost:%s" % (chroot, start_port,))
        start_port += 1
        args = default_args + ["-o", "ListenAddress=127.0.0.1:%s" % (start_port,)]
        pid, exit_st = spawn_ssh(args, os.path.join(chroot_dir, chroot))
        if exit_st == 0:
            print("started sshd in chroot: %s" % (chroot,))
        else:
            print("NOT started sshd in chroot: %s, perhaps already started?" % (chroot,))
        ch_f.write("\t%s at: root@localhost -p %s\n" % (chroot, start_port,))

    ch_f.flush()
    ch_f.close()