lvm2/daemons/common/daemon-server.c

/*
 * Copyright (C) 2011 Red Hat, Inc. All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License v.2.1.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <dlfcn.h>
#include <errno.h>
#include <pthread.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <netinet/in.h>
#include <sys/un.h>
#include <unistd.h>
#include <signal.h>

#include <syslog.h>
#include "daemon-server.h"
#include "libdevmapper.h"

#if 0
/* Create a device monitoring thread. */
static int _pthread_create(pthread_t *t, void *(*fun)(void *), void *arg, int stacksize)
{
	pthread_attr_t attr;
	pthread_attr_init(&attr);
	/*
	 * We use a smaller stack since it gets preallocated in its entirety
	 */
	pthread_attr_setstacksize(&attr, stacksize);
	return pthread_create(t, &attr, fun, arg);
}
#endif

static volatile sig_atomic_t _shutdown_requested = 0;

static void _exit_handler(int sig __attribute__((unused)))
{
	_shutdown_requested = 1;
}

#ifdef linux
#  define OOM_ADJ_FILE "/proc/self/oom_adj"
#  include <stdio.h>

/* From linux/oom.h */
#  define OOM_DISABLE (-17)
#  define OOM_ADJUST_MIN (-16)

/*
 * Protection against OOM killer if kernel supports it
 */
static int _set_oom_adj(int val)
{
	FILE *fp;

	struct stat st;

	if (stat(OOM_ADJ_FILE, &st) == -1) {
		if (errno == ENOENT)
			perror(OOM_ADJ_FILE " not found");
		else
			perror(OOM_ADJ_FILE ": stat failed");
		return 1;
	}

	if (!(fp = fopen(OOM_ADJ_FILE, "w"))) {
		perror(OOM_ADJ_FILE ": fopen failed");
		return 0;
	}

	fprintf(fp, "%i", val);
	if (fclose(fp))
		perror(OOM_ADJ_FILE ": fclose failed");

	return 1;
}
#endif

static int _open_socket(daemon_state s)
{
	int fd = -1;
	struct sockaddr_un sockaddr;
	mode_t old_mask;

	(void) dm_prepare_selinux_context(s.socket_path, S_IFSOCK);
	old_mask = umask(0077);

	/* Open local socket */
	fd = socket(PF_UNIX, SOCK_STREAM, 0);
	if (fd < 0) {
		perror("Can't create local socket.");
		goto error;
	}

	/* Set Close-on-exec & non-blocking */
	if (fcntl(fd, F_SETFD, 1))
		fprintf(stderr, "setting CLOEXEC on socket fd %d failed: %s\n", fd, strerror(errno));
	fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);

	fprintf(stderr, "creating %s\n", s.socket_path);
	memset(&sockaddr, 0, sizeof(sockaddr));
	strcpy(sockaddr.sun_path, s.socket_path);
	sockaddr.sun_family = AF_UNIX;

	if (bind(fd, (struct sockaddr *) &sockaddr, sizeof(sockaddr))) {
		perror("can't bind local socket.");
		goto error;
	}
	if (listen(fd, 1) != 0) {
		perror("listen local");
		goto error;
	}

out:
	umask(old_mask);
	(void) dm_prepare_selinux_context(NULL, 0);
	return fd;

error:
	if (fd >= 0) {
		close(fd);
		unlink(s.socket_path);
		fd = -1;
	}
	goto out;
}

static void remove_lockfile(const char *file)
{
	if (unlink(file))
		perror("unlink failed");
}

static void _daemonise(void)
{
	int child_status;
	int fd;
	pid_t pid;
	struct rlimit rlim;
	struct timeval tval;
	sigset_t my_sigset;

	sigemptyset(&my_sigset);
	if (sigprocmask(SIG_SETMASK, &my_sigset, NULL) < 0) {
		fprintf(stderr, "Unable to restore signals.\n");
		exit(EXIT_FAILURE);
	}
	signal(SIGTERM, &_exit_handler);

	switch (pid = fork()) {
	case -1:
		perror("fork failed:");
		exit(EXIT_FAILURE);

	case 0:		/* Child */
		break;

	default:
		/* Wait for response from child */
		while (!waitpid(pid, &child_status, WNOHANG) && !_shutdown_requested) {
			tval.tv_sec = 0;
			tval.tv_usec = 250000;	/* .25 sec */
			select(0, NULL, NULL, NULL, &tval);
		}

		if (_shutdown_requested) /* Child has signaled it is ok - we can exit now */
			exit(0);

		/* Problem with child.  Determine what it is by exit code */
		fprintf(stderr, "Child exited with code %d\n", WEXITSTATUS(child_status));
		exit(WEXITSTATUS(child_status));
	}

	if (chdir("/"))
		exit(1);

	if (getrlimit(RLIMIT_NOFILE, &rlim) < 0)
		fd = 256; /* just have to guess */
	else
		fd = rlim.rlim_cur;

	for (--fd; fd >= 0; fd--)
		close(fd);

	if ((open("/dev/null", O_RDONLY) < 0) ||
	    (open("/dev/null", O_WRONLY) < 0) ||
	    (open("/dev/null", O_WRONLY) < 0))
		exit(1);

	setsid();
}

struct thread_baton {
	daemon_state s;
	client_handle client;
};

void *client_thread(void *baton)
{
	struct thread_baton *b = baton;
	request req;
	while (1) {
		if (!read_buffer(b->client.socket_fd, &req.buffer))
			goto fail;

		/* TODO parse the buffer into req.cft */
		response res = b->s.handler(b->s, b->client, req);

		if (!res.buffer) {
			/* TODO fill in the buffer from res.cft */
		}

		write_buffer(b->client.socket_fd, res.buffer, strlen(res.buffer));

		free(res.buffer);
		free(req.buffer);
	}
fail:
	/* TODO what should we really do here? */
	return NULL;
}

int handle_connect(daemon_state s)
{
	struct sockaddr_un sockaddr;
	client_handle client;
	socklen_t sl = sizeof(sockaddr);
	int client_fd = accept(s.socket_fd, (struct sockaddr *) &sockaddr, &sl);
	if (client_fd < 0)
		return 0;

	struct thread_baton *baton = malloc(sizeof(struct thread_baton));
	if (!baton)
		return 0;

	client.socket_fd = client_fd;
	client.read_buf = 0;
	client.private = 0;
	baton->s = s;
	baton->client = client;

	if (pthread_create(&baton->client.thread_id, NULL, client_thread, baton))
		return 0;
	return 1;
}

void daemon_start(daemon_state s)
{
	int failed = 0;
	/*
	 * Switch to C locale to avoid reading large locale-archive file used by
	 * some glibc (on some distributions it takes over 100MB). Some daemons
	 * need to use mlockall().
	 */
	if (setenv("LANG", "C", 1))
		perror("Cannot set LANG to C");

	if (!s.foreground)
		_daemonise();

	/* TODO logging interface should be somewhat more elaborate */
	openlog(s.name, LOG_PID, LOG_DAEMON);

	(void) dm_prepare_selinux_context(s.pidfile, S_IFREG);

	/*
	 * NB. Take care to not keep stale locks around. Best not exit(...)
	 * after this point.
	 */
	if (dm_create_lockfile(s.pidfile) == 0)
		exit(1);

	(void) dm_prepare_selinux_context(NULL, 0);

	/* Set normal exit signals to request shutdown instead of dying. */
	signal(SIGINT, &_exit_handler);
	signal(SIGHUP, &_exit_handler);
	signal(SIGQUIT, &_exit_handler);
	signal(SIGTERM, &_exit_handler);
	signal(SIGPIPE, SIG_IGN);

#ifdef linux
	if (s.avoid_oom && !_set_oom_adj(OOM_DISABLE) && !_set_oom_adj(OOM_ADJUST_MIN))
		syslog(LOG_ERR, "Failed to set oom_adj to protect against OOM killer");
#endif

	if (s.socket_path) {
		s.socket_fd = _open_socket(s);
		if (s.socket_fd < 0)
			failed = 1;
	}

	/* Signal parent, letting them know we are ready to go. */
	if (!s.foreground)
		kill(getppid(), SIGTERM);

	while (!_shutdown_requested && !failed) {
		int status;
		fd_set in;
		FD_ZERO(&in);
		FD_SET(s.socket_fd, &in);
		if (select(FD_SETSIZE, &in, NULL, NULL, NULL) < 0 && errno != EINTR)
			perror("select error");
		if (FD_ISSET(s.socket_fd, &in))
			if (!handle_connect(s))
				syslog(LOG_ERR, "Failed to handle a client connection.");
	}

	if (s.socket_fd >= 0)
		unlink(s.socket_path);

	syslog(LOG_NOTICE, "%s shutting down", s.name);
	closelog();
	remove_lockfile(s.pidfile);
	if (failed)
		exit(1);
}