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Merge pull request #839 from brauner/2016-02-15/lxc_attach_pty

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lxc-attach: add comment, & implement login_tty()
This commit is contained in:
Stéphane Graber 2016-02-22 10:22:59 -05:00
commit b5c8400909
1 changed files with 48 additions and 13 deletions
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61
src/lxc/lxc_attach.c
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@ -210,6 +210,19 @@ struct wrapargs {
int ptyfd;
};
/* Minimalistic login_tty() implementation. */
static int login_pty(int fd)
{
setsid();
if (ioctl(fd, TIOCSCTTY, NULL) < 0)
return -1;
if (lxc_console_set_stdfds(fd) < 0)
return -1;
if (fd > STDERR_FILENO)
close(fd);
return 0;
}
/* Minimalistic forkpty() implementation. */
static pid_t fork_pty(int *masterfd)
{
@ -226,11 +239,8 @@ static pid_t fork_pty(int *masterfd)
return -1;
} else if (pid == 0) {
close(master);
setsid();
if (ioctl(slave, TIOCSCTTY, NULL) < 0)
_exit(-1); /* automatically closes fds */
if (lxc_console_set_stdfds(slave) < 0)
_exit(-1); /* automatically closes fds */
if (login_pty(slave) < 0)
_exit(-1); /* closes fds */
return 0;
} else {
*masterfd = master;
@ -239,6 +249,29 @@ static pid_t fork_pty(int *masterfd)
}
}
/*
* This is probably redundant but just so that intentions can be checked against
* code for future modifications. Here is what this is supposed to achieve:
* Since we fork() in pty_in_container() the shell that is run on the slave side
* of the pty is the grandchild of c->attach() in main(). But what we probably
* are interested in is the exit code of the grandchild. So we wait for the
* grandchild to change status and return its exit code from this function. We
* thereby make the exit code of the grandchild the exit code of the child and
* allow the grandparent to see the exit code of the grandchild by waiting on
* the pid of the child to change status:
*
* grandchild: lxc_attach_run_command()/lxc_attach_run_shell()
*
* child: pty_in_container()
* - perform waitpid() on pid returned by lxc_attach_run_command() or
* lxc_attach_run_shell()
*
* grandparent: c->attach()
* - return pid of pty_in_container() in pid argument.
*
* main()
* - perform waitpid() on pid returned in pid argument of c->attach()
*/
static int pty_in_container(void *p)
{
int ret;
@ -335,9 +368,14 @@ err2:
err1:
tcsetattr(args->ptyfd, TCSAFLUSH, &oldtios);
if (pid > 0)
ret = lxc_wait_for_pid_status(pid);
return ret;
ret = lxc_wait_for_pid_status(pid);
if (ret < 0)
return ret;
if (WIFEXITED(ret))
return WEXITSTATUS(ret);
return -1;
}
static int pty_on_host_callback(void *p)
@ -345,16 +383,13 @@ static int pty_on_host_callback(void *p)
struct wrapargs *wrap = p;
close(wrap->console->master);
setsid();
ioctl(wrap->console->slave, TIOCSCTTY, NULL);
if (lxc_console_set_stdfds(wrap->console->slave) < 0)
if (login_pty(wrap->console->slave) < 0)
return -1;
if (wrap->command->program)
lxc_attach_run_command(wrap->command);
else
lxc_attach_run_shell(NULL);
return -1;
}
@ -465,7 +500,7 @@ int main(int argc, char *argv[])
if (access(my_args.lxcpath[0], O_RDWR) < 0) {
if (!my_args.quiet)
fprintf(stderr, "You lack access to %s\n", my_args.lxcpath[0]);
exit(ret);
exit(EXIT_FAILURE);
}
}