path: root/src/lxc/start.c

/*
 * lxc: linux Container library
 *
 * (C) Copyright IBM Corp. 2007, 2008
 *
 * Authors:
 * Daniel Lezcano <dlezcano at fr.ibm.com>
 *
 * 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 "../config.h"
#include <stdio.h>
#undef _GNU_SOURCE
#include <string.h>
#include <stdlib.h>
#include <dirent.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <termios.h>
#include <namespace.h>
#include <sys/param.h>
#include <sys/file.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/capability.h>
#include <sys/wait.h>
#include <sys/un.h>
#include <sys/poll.h>

#include <lxc/lxc.h>
#include <lxc/confile.h>

#ifdef HAVE_SYS_SIGNALFD_H 
#  include <sys/signalfd.h>
#else
#  ifndef __NR_signalfd4
/* assume kernel headers are too old */
#    if __i386__
#      define __NR_signalfd4 327
#    elif __x86_64__
#      define __NR_signalfd4 289
#    elif __powerpc__
#      define __NR_signalfd4 313
#    elif __s390x__
#      define __NR_signalfd4 322
#    endif
#endif

#  ifndef __NR_signalfd
/* assume kernel headers are too old */
#    if __i386__
#      define __NR_signalfd 321
#    elif __x86_64__
#      define __NR_signalfd 282
#    elif __powerpc__
#      define __NR_signalfd 305
#    elif __s390x__
#      define __NR_signalfd 316
#    endif
#endif

int signalfd(int fd, const sigset_t *mask, int flags)
{
	int retval;

	retval = syscall (__NR_signalfd4, fd, mask, _NSIG / 8, flags);
	if (errno == ENOSYS && flags == 0)
		retval = syscall (__NR_signalfd, fd, mask, _NSIG / 8);
	return retval;
}
#endif

#if !HAVE_DECL_PR_CAPBSET_DROP
#define PR_CAPBSET_DROP 24
#endif

#include "error.h"
#include "af_unix.h"
#include "mainloop.h"
#include "commands.h"

#include <lxc/lxc.h>
#include <lxc/log.h>

lxc_log_define(lxc_start, lxc);

LXC_TTY_HANDLER(SIGINT);
LXC_TTY_HANDLER(SIGQUIT);

static int setup_sigchld_fd(sigset_t *oldmask)
{
	sigset_t mask;
	int fd;

	if (sigprocmask(SIG_BLOCK, NULL, &mask)) {
		SYSERROR("failed to get mask signal");
		return -1;
	}

	if (sigaddset(&mask, SIGCHLD) || sigprocmask(SIG_BLOCK, &mask, oldmask)) {
		SYSERROR("failed to set mask signal");
		return -1;
	}

	fd = signalfd(-1, &mask, 0);
	if (fd < 0) {
		SYSERROR("failed to create the signal fd");
		return -1;
	}

	if (fcntl(fd, F_SETFD, FD_CLOEXEC)) {
		SYSERROR("failed to set sigfd to close-on-exec");
		close(fd);
		return -1;
	}

	DEBUG("sigchild handler set");

	return fd;
}

static int sigchld_handler(int fd, void *data, 
			   struct lxc_epoll_descr *descr)
{
	DEBUG("child exited");

	return 1;
}

static int set_state(const char *name, struct lxc_handler *handler, lxc_state_t state)
{
	handler->state = state;
	lxc_monitor_send_state(name, state);
	return 0;
}

int lxc_poll(const char *name, struct lxc_handler *handler)
{
	int sigfd = handler->sigfd;
	int pid = handler->pid;
	int ret = -1;
	struct lxc_epoll_descr descr;

	if (lxc_mainloop_open(&descr)) {
		ERROR("failed to create mainloop");
		goto out_sigfd;
	}

	if (lxc_mainloop_add_handler(&descr, sigfd, sigchld_handler, &pid)) {
		ERROR("failed to add handler for the signal");
		goto out_mainloop_open;
	}

	if (lxc_command_mainloop_add(name, &descr, handler))
		goto out_mainloop_open;

	ret = lxc_mainloop(&descr);

out:
	return ret;

out_mainloop_open:
	lxc_mainloop_close(&descr);
out_sigfd:
	close(sigfd);
	goto out;
}

static void remove_init_pid(const char *name, pid_t pid)
{
	char init[MAXPATHLEN];

	snprintf(init, MAXPATHLEN, LXCPATH "/%s/init", name);
	unlink(init);
}

static int fdname(int fd, char *name, size_t size)
{
	char path[MAXPATHLEN];
	ssize_t len;

	snprintf(path, MAXPATHLEN, "/proc/self/fd/%d", fd);

	len = readlink(path, name, size);
	if (len >  0)
		path[len] = '\0';

	return (len <= 0) ? -1 : 0;
}

static int console_init(char *console, size_t size)
{
	struct stat stat;
	int i;

	for (i = 0; i < 3; i++) {
		if (!isatty(i))
			continue;

		if (ttyname_r(i, console, size)) {
			SYSERROR("failed to retrieve tty name");
			return -1;
		}

		return 0;
	}

	if (!fstat(0, &stat)) {
		if (S_ISREG(stat.st_mode) || S_ISCHR(stat.st_mode) ||
		    S_ISFIFO(stat.st_mode) || S_ISLNK(stat.st_mode))
			return fdname(0, console, size);
	}

	console[0] = '\0';

	DEBUG("console initialized");

	return 0;
}

struct lxc_handler *lxc_init(const char *name, const char *rcfile)
{
	struct lxc_handler *handler;
	char path[MAXPATHLEN];

	handler = malloc(sizeof(*handler));
	if (!handler)
		return NULL;

	memset(handler, 0, sizeof(*handler));

	/* Begin the set the state to STARTING*/
	if (set_state(name, handler, STARTING)) {
		ERROR("failed to set state '%s'", lxc_state2str(STARTING));
		goto out_free;
	}

	if (lxc_conf_init(&handler->conf)) {
		ERROR("failed to initialize the configuration");
		goto out_aborting;
	}

	if (rcfile && access(path, F_OK)) {
		ERROR("failed to access rcfile");
		goto out_aborting;

		if (lxc_config_read(path, &handler->conf)) {
			ERROR("failed to read the configuration file");
			goto out_aborting;
		}
	}

	if (console_init(handler->conf.console,
			 sizeof(handler->conf.console))) {
		ERROR("failed to initialize the console");
		goto out_aborting;
	}

	if (lxc_create_tty(name, &handler->conf)) {
		ERROR("failed to create the ttys");
		goto out_aborting;
	}

	/* the signal fd has to be created before forking otherwise
	 * if the child process exits before we setup the signal fd,
	 * the event will be lost and the command will be stuck */
	handler->sigfd = setup_sigchld_fd(&handler->oldmask);
	if (handler->sigfd < 0) {
		ERROR("failed to set sigchild fd handler");
		goto out_delete_tty;
	}

	/* Avoid signals from terminal */
	LXC_TTY_ADD_HANDLER(SIGINT);
	LXC_TTY_ADD_HANDLER(SIGQUIT);

out:
	if (handler)
		INFO("'%s' is initialized", name);

	return handler;

out_delete_tty:
	lxc_delete_tty(&handler->conf.tty_info);
out_aborting:
	set_state(name, handler, ABORTING);
out_free:
	free(handler);
	handler = NULL;
	goto out;
}

void lxc_fini(const char *name, struct lxc_handler *handler)
{
	/* The STOPPING state is there for future cleanup code
	 * which can take awhile
	 */
	set_state(name, handler, STOPPING);
	set_state(name, handler, STOPPED);
	lxc_unlink_nsgroup(name);

	if (handler) {
		remove_init_pid(name, handler->pid);
		lxc_delete_tty(&handler->conf.tty_info);
		free(handler);
	}

	LXC_TTY_DEL_HANDLER(SIGQUIT);
	LXC_TTY_DEL_HANDLER(SIGINT);
}

void lxc_abort(const char *name, struct lxc_handler *handler)
{
	set_state(name, handler, ABORTING);
	kill(handler->pid, SIGKILL);
}

struct start_arg {
	const char *name;
	char *const *argv;
	struct lxc_handler *handler;
	int *sv;
};

static int do_start(void *arg)
{
	struct start_arg *start_arg = arg;
	struct lxc_handler *handler = start_arg->handler;
	const char *name = start_arg->name;
	char *const *argv = start_arg->argv;
	int *sv = start_arg->sv;
	int err = -1, sync;

	if (sigprocmask(SIG_SETMASK, &handler->oldmask, NULL)) {
		SYSERROR("failed to set sigprocmask");
		goto out_child;
	}

	close(sv[1]);

	/* Be sure we don't inherit this after the exec */
	fcntl(sv[0], F_SETFD, FD_CLOEXEC);

	/* Tell our father he can begin to configure the container */
	if (write(sv[0], &sync, sizeof(sync)) < 0) {
		SYSERROR("failed to write socket");
		goto out_child;
	}

	/* Wait for the father to finish the configuration */
	if (read(sv[0], &sync, sizeof(sync)) < 0) {
		SYSERROR("failed to read socket");
		goto out_child;
	}

	/* Setup the container, ip, names, utsname, ... */
	if (lxc_setup(name, &handler->conf)) {
		ERROR("failed to setup the container");
		goto out_warn_father;
	}

	if (prctl(PR_CAPBSET_DROP, CAP_SYS_BOOT, 0, 0, 0)) {
		SYSERROR("failed to remove CAP_SYS_BOOT capability");
		goto out_child;
	}

	if (prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0)) {
		SYSERROR("failed to set pdeath signal");
		goto out_child;
	}

	NOTICE("exec'ing '%s'", argv[0]);

	execvp(argv[0], argv);
	SYSERROR("failed to exec %s", argv[0]);

out_warn_father:
	/* If the exec fails, tell that to our father */
	if (write(sv[0], &err, sizeof(err)) < 0)
		SYSERROR("failed to write the socket");
out_child:
	return -1;
}

int lxc_spawn(const char *name, struct lxc_handler *handler, char *const argv[])
{
	int sv[2];
	int clone_flags;
	int err = -1, sync;

	struct start_arg start_arg = {
		.name = name,
		.argv = argv,
		.handler = handler,
		.sv = sv,
	};

	/* Synchro socketpair */
	if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sv)) {
		SYSERROR("failed to create communication socketpair");
		goto out;
	}

	clone_flags = CLONE_NEWUTS|CLONE_NEWPID|CLONE_NEWIPC|CLONE_NEWNS;
	if (!lxc_list_empty(&handler->conf.network)) {

		clone_flags |= CLONE_NEWNET;

		/* that should be done before the clone because we will
		 * fill the netdev index and use them in the child
		 */
		if (lxc_create_network(&handler->conf.network)) {
			ERROR("failed to create the network");
			goto out_close;
		}
	}

	/* Create a process in a new set of namespaces */
	handler->pid = lxc_clone(do_start, &start_arg, clone_flags);
	if (handler->pid < 0) {
		SYSERROR("failed to fork into a new namespace");
		goto out_close;
	}

	close(sv[0]);
	
	/* Wait for the child to be ready */
	if (read(sv[1], &sync, sizeof(sync)) < 0) {
		SYSERROR("failed to read the socket");
		goto out_abort;
	}

	if (lxc_rename_nsgroup(name, handler))
		goto out_abort;

	/* Create the network configuration */
	if (clone_flags & CLONE_NEWNET) {
		if (lxc_assign_network(&handler->conf.network, handler->pid)) {
			ERROR("failed to create the configured network");
			goto out_abort;
		}
	}

	/* Tell the child to continue its initialization */
	if (write(sv[1], &sync, sizeof(sync)) < 0) {
		SYSERROR("failed to write the socket");
		goto out_abort;
	}

	/* Wait for the child to exec or returning an error */
	if (read(sv[1], &sync, sizeof(sync)) < 0) {
		ERROR("failed to read the socket");
		goto out_abort;
	}

	if (set_state(name, handler, RUNNING)) {
		ERROR("failed to set state to %s",
			      lxc_state2str(RUNNING));
		goto out_abort;
	}

	err = 0;

	NOTICE("'%s' started with pid '%d'", argv[0], handler->pid);

out_close:
	close(sv[0]);
	close(sv[1]);
out:
	return err;

out_abort:
	lxc_abort(name, handler);
	goto out_close;
}

int lxc_start(const char *name, char *const argv[], const char *rcfile)
{
	struct lxc_handler *handler;
	int err = -1;
	int status;

	handler = lxc_init(name, rcfile);
	if (!handler) {
		ERROR("failed to initialize the container");
		return -1;
	}

	err = lxc_spawn(name, handler, argv);
	if (err) {
		ERROR("failed to spawn '%s'", argv[0]);
		goto out;
	}

	err = lxc_close_all_inherited_fd();
	if (err) {
		ERROR("unable to close inherited fds");
		goto out_abort;
	}

	err = lxc_poll(name, handler);
	if (err) {
		ERROR("mainloop exited with an error");
		goto out_abort;
	}

	while (waitpid(handler->pid, &status, 0) < 0 && errno == EINTR)
		continue;

	err =  lxc_error_set_and_log(handler->pid, status);
out:
	lxc_fini(name, handler);
	return err;

out_abort:
	lxc_abort(name, handler);
	goto out;
}