blockd.c

#define _GNU_SOURCE
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/wait.h>

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

#include <errno.h>

#include <linux/limits.h>
#include <linux/auto_fs4.h>

#include <libubox/uloop.h>
#include <libubox/utils.h>
#include <libubox/vlist.h>
#include <libubox/ulog.h>
#include <libubox/avl-cmp.h>
#include <libubus.h>

#include "libfstools/libfstools.h"

#define	AUTOFS_MOUNT_PATH	"/tmp/run/blockd/"
#define AUTOFS_TIMEOUT		30
#define AUTOFS_EXPIRE_TIMER	(5 * 1000)

struct hotplug_context {
	struct uloop_process process;
	void *priv;
};

struct device {
	struct vlist_node node;
	struct blob_attr *msg;
	char *name;
	char *target;
	int autofs;
	int anon;
};

static struct uloop_fd fd_autofs_read;
static int fd_autofs_write = 0;
static struct ubus_auto_conn conn;
struct blob_buf bb = { 0 };

enum {
	MOUNT_UUID,
	MOUNT_LABEL,
	MOUNT_ENABLE,
	MOUNT_TARGET,
	MOUNT_DEVICE,
	MOUNT_OPTIONS,
	MOUNT_AUTOFS,
	MOUNT_ANON,
	MOUNT_REMOVE,
	__MOUNT_MAX
};

static const struct blobmsg_policy mount_policy[__MOUNT_MAX] = {
	[MOUNT_UUID] = { .name = "uuid", .type = BLOBMSG_TYPE_STRING },
	[MOUNT_LABEL] = { .name = "label", .type = BLOBMSG_TYPE_STRING },
	[MOUNT_DEVICE] = { .name = "device", .type = BLOBMSG_TYPE_STRING },
	[MOUNT_TARGET] = { .name = "target", .type = BLOBMSG_TYPE_STRING },
	[MOUNT_OPTIONS] = { .name = "options", .type = BLOBMSG_TYPE_STRING },
	[MOUNT_ENABLE] = { .name = "enabled", .type = BLOBMSG_TYPE_INT32 },
	[MOUNT_AUTOFS] = { .name = "autofs", .type = BLOBMSG_TYPE_INT32 },
	[MOUNT_ANON] = { .name = "anon", .type = BLOBMSG_TYPE_INT32 },
	[MOUNT_REMOVE] = { .name = "remove", .type = BLOBMSG_TYPE_INT32 },
};

enum {
	INFO_DEVICE,
	__INFO_MAX
};

static const struct blobmsg_policy info_policy[__INFO_MAX] = {
	[INFO_DEVICE] = { .name = "device", .type = BLOBMSG_TYPE_STRING },
};

static char*
_find_mount_point(char *device)
{
	char *dev, *mp;

	if (asprintf(&dev, "/dev/%s", device) == -1)
		exit(ENOMEM);

	mp = find_mount_point(dev, 0);
	free(dev);

	return mp;
}

static int
block(char *cmd, char *action, char *device, int sync, struct uloop_process *process)
{
	pid_t pid = fork();
	int ret = sync;
	int status;
	char *argv[5] = { 0 };
	int a = 0;

	switch (pid) {
	case -1:
		ULOG_ERR("failed to fork block process\n");
		break;

	case 0:
		uloop_end();

		argv[a++] = "/sbin/block";
		argv[a++] = cmd;
		argv[a++] = action;
		argv[a++] = device;
		execvp(argv[0], argv);
		ULOG_ERR("failed to spawn %s %s %s\n", *argv, action, device);
		exit(EXIT_FAILURE);

	default:
		if (!sync && process) {
			process->pid = pid;
			uloop_process_add(process);
		} else if (sync) {
			waitpid(pid, &status, 0);
			ret = WEXITSTATUS(status);
			if (ret)
				ULOG_ERR("failed to run block. %s/%s\n", action, device);
		}
		break;
	}

	return ret;
}

static int send_block_notification(struct ubus_context *ctx, const char *action,
			    const char *devname, const char *target);
static int hotplug_call_mount(struct ubus_context *ctx, const char *action,
			      const char *devname, uloop_process_handler cb, void *priv)
{
	char * const argv[] = { "hotplug-call", "mount", NULL };
	struct hotplug_context *c = NULL;
	pid_t pid;
	int err;

	if (cb) {
		c = calloc(1, sizeof(*c));
		if (!c)
			return -ENOMEM;
	}

	pid = fork();
	switch (pid) {
	case -1:
		if (c)
			free(c);

		err = -errno;
		ULOG_ERR("fork() failed\n");
		return err;
	case 0:
		uloop_end();

		setenv("ACTION", action, 1);
		setenv("DEVICE", devname, 1);

		execv("/sbin/hotplug-call", argv);
		exit(-1);
		break;
	default:
		if (c) {
			c->process.pid = pid;
			c->process.cb = cb;
			c->priv = priv;
			uloop_process_add(&c->process);
		}
		break;
	}

	return 0;
}

static void device_mount_remove_hotplug_cb(struct uloop_process *p, int stat)
{
	struct hotplug_context *hctx = container_of(p, struct hotplug_context, process);
	struct device *device = hctx->priv;
	char *mp;

	if (device->target)
		unlink(device->target);

	mp = _find_mount_point(device->name);
	if (mp) {
		block("autofs", "remove", device->name, 0, NULL);
		free(mp);
	}

	free(device);
	free(hctx);
}

static void device_mount_remove(struct ubus_context *ctx, struct device *device)
{
	static const char *action = "remove";

	hotplug_call_mount(ctx, action, device->name,
			   device_mount_remove_hotplug_cb, device);

	send_block_notification(ctx, action, device->name, device->target);
}

static void device_mount_add(struct ubus_context *ctx, struct device *device)
{
	struct stat st;
	char *path, *tmp;

	if (asprintf(&path, "/tmp/run/blockd/%s", device->name) == -1)
		exit(ENOMEM);

	if (!lstat(device->target, &st)) {
		if (S_ISLNK(st.st_mode))
			unlink(device->target);
		else if (S_ISDIR(st.st_mode))
			rmdir(device->target);
	}

	tmp = strrchr(device->target, '/');
	if (tmp && tmp != device->target && tmp != &device->target[strlen(path)-1]) {
		*tmp = '\0';
		mkdir_p(device->target, 0755);
		*tmp = '/';
	}

	if (symlink(path, device->target)) {
		ULOG_ERR("failed to symlink %s->%s (%d) - %m\n", device->target, path, errno);
	} else {
		static const char *action = "add";
		hotplug_call_mount(ctx, action, device->name, NULL, NULL);
		send_block_notification(ctx, action, device->name, device->target);
	}
	free(path);
}

static int
device_move(struct device *device_o, struct device *device_n)
{
	char *path;

	if (device_o->autofs != device_n->autofs)
		return -1;

	if (device_o->anon || device_n->anon)
		return -1;

	if (device_o->autofs) {
		unlink(device_o->target);
		if (asprintf(&path, "/tmp/run/blockd/%s", device_n->name) == -1)
			exit(ENOMEM);

		if (symlink(path, device_n->target))
			ULOG_ERR("failed to symlink %s->%s (%d) - %m\n", device_n->target, path, errno);

		free(path);
	} else {
		mkdir(device_n->target, 0755);
		if (mount(device_o->target, device_n->target, NULL, MS_MOVE, NULL))
			rmdir(device_n->target);
		else
			rmdir(device_o->target);
	}

	return 0;
}

static void vlist_nop_update(struct vlist_tree *tree,
			     struct vlist_node *node_new,
			     struct vlist_node *node_old)
{
}

VLIST_TREE(devices, avl_strcmp, vlist_nop_update, false, false);

static int
block_hotplug(struct ubus_context *ctx, struct ubus_object *obj,
	      struct ubus_request_data *req, const char *method,
	      struct blob_attr *msg)
{
	struct blob_attr *data[__MOUNT_MAX];
	struct device *device;
	struct blob_attr *_msg;
	char *devname, *_name;
	char *target = NULL, *__target;
	char *_target = NULL;

	blobmsg_parse(mount_policy, __MOUNT_MAX, data, blob_data(msg), blob_len(msg));

	if (!data[MOUNT_DEVICE])
		return UBUS_STATUS_INVALID_ARGUMENT;

	devname = blobmsg_get_string(data[MOUNT_DEVICE]);

	if (data[MOUNT_TARGET]) {
		target = blobmsg_get_string(data[MOUNT_TARGET]);
	} else {
		if (asprintf(&_target, "/mnt/%s",
			     blobmsg_get_string(data[MOUNT_DEVICE])) == -1)
			exit(ENOMEM);

		target = _target;
	}

	if (data[MOUNT_REMOVE])
		device = vlist_find(&devices, devname, device, node);
	else
		device = calloc_a(sizeof(*device), &_msg, blob_raw_len(msg),
				  &_name, strlen(devname) + 1, &__target, strlen(target) + 1);

	if (!device) {
		if (_target)
			free(_target);

		return UBUS_STATUS_UNKNOWN_ERROR;
	}

	if (data[MOUNT_REMOVE]) {
		vlist_delete(&devices, &device->node);

		if (device->autofs)
			device_mount_remove(ctx, device);
		else
			free(device);

		if (_target)
			free(_target);
	} else {
		struct device *old = vlist_find(&devices, devname, device, node);

		device->autofs = data[MOUNT_AUTOFS] ? blobmsg_get_u32(data[MOUNT_AUTOFS]) : 0;
		device->anon = data[MOUNT_ANON] ? blobmsg_get_u32(data[MOUNT_ANON]) : 0;
		device->msg = _msg;
		memcpy(_msg, msg, blob_raw_len(msg));
		device->name = _name;
		strcpy(_name, devname);
		device->target = __target;
		strcpy(__target, target);
		if (_target)
			free(_target);

		vlist_add(&devices, &device->node, device->name);

		if (old && device_move(old, device)) {
			device_mount_remove(ctx, old);
			device_mount_add(ctx, device);
			if (!device->autofs)
				block("mount", NULL, NULL, 0, NULL);
		} else if (device->autofs) {
			device_mount_add(ctx, device);
		}
	}

	return 0;
}

static int blockd_mount(struct ubus_context *ctx, struct ubus_object *obj,
			struct ubus_request_data *req, const char *method,
			struct blob_attr *msg)
{
	static const char *action = "add";
	struct blob_attr *data[__MOUNT_MAX];
	struct device *device;
	char *devname;

	blobmsg_parse(mount_policy, __MOUNT_MAX, data, blob_data(msg), blob_len(msg));

	if (!data[MOUNT_DEVICE])
		return UBUS_STATUS_INVALID_ARGUMENT;

	devname = blobmsg_get_string(data[MOUNT_DEVICE]);

	device = vlist_find(&devices, devname, device, node);
	if (!device)
		return UBUS_STATUS_UNKNOWN_ERROR;

	hotplug_call_mount(ctx, action, device->name, NULL, NULL);
	send_block_notification(ctx, action, device->name, device->target);

	return 0;
}

struct blockd_umount_context {
	struct ubus_context *ctx;
	struct ubus_request_data req;
};

static void blockd_umount_hotplug_cb(struct uloop_process *p, int stat)
{
	struct hotplug_context *hctx = container_of(p, struct hotplug_context, process);
	struct blockd_umount_context *c = hctx->priv;

	ubus_complete_deferred_request(c->ctx, &c->req, 0);

	free(c);
	free(hctx);
}

static int blockd_umount(struct ubus_context *ctx, struct ubus_object *obj,
			 struct ubus_request_data *req, const char *method,
			 struct blob_attr *msg)
{
	struct blob_attr *data[__MOUNT_MAX];
	struct blockd_umount_context *c;
	static const char *action = "remove";
	char *devname;
	static char oldtarget[PATH_MAX];
	struct device *device;
	int err;

	blobmsg_parse(mount_policy, __MOUNT_MAX, data, blob_data(msg), blob_len(msg));

	if (!data[MOUNT_DEVICE])
		return UBUS_STATUS_INVALID_ARGUMENT;

	devname = blobmsg_get_string(data[MOUNT_DEVICE]);
	device = vlist_find(&devices, devname, device, node);
	if (device) {
		strncpy(oldtarget, device->target, sizeof(oldtarget)-1);
		oldtarget[PATH_MAX - 1] = '\0';
	}

	c = calloc(1, sizeof(*c));
	if (!c)
		return UBUS_STATUS_UNKNOWN_ERROR;

	c->ctx = ctx;
	ubus_defer_request(ctx, req, &c->req);

	err = hotplug_call_mount(ctx, action, devname, blockd_umount_hotplug_cb, c);
	if (err) {
		free(c);
		return UBUS_STATUS_UNKNOWN_ERROR;
	}

	send_block_notification(ctx, action, devname, oldtarget);

	return 0;
}

static void block_info_dump(struct blob_buf *b, struct device *device)
{
	struct blob_attr *v;
	char *mp;
	int rem;

	blob_for_each_attr(v, device->msg, rem)
		blobmsg_add_blob(b, v);

	mp = _find_mount_point(device->name);
	if (mp) {
		blobmsg_add_string(b, "mount", mp);
		free(mp);
	} else if (device->autofs && device->target) {
		blobmsg_add_string(b, "mount", device->target);
	}
}

static int
block_info(struct ubus_context *ctx, struct ubus_object *obj,
	   struct ubus_request_data *req, const char *method,
	   struct blob_attr *msg)
{
	struct blob_attr *data[__INFO_MAX];
	struct device *device = NULL;

	blobmsg_parse(info_policy, __INFO_MAX, data, blob_data(msg), blob_len(msg));

	if (data[INFO_DEVICE]) {
		device = vlist_find(&devices, blobmsg_get_string(data[INFO_DEVICE]), device, node);
		if (!device)
			return UBUS_STATUS_INVALID_ARGUMENT;
	}

	blob_buf_init(&bb, 0);
	if (device) {
		block_info_dump(&bb, device);
	} else {
		void *a;

		a = blobmsg_open_array(&bb, "devices");
		vlist_for_each_element(&devices, device, node) {
			void *t;

			t = blobmsg_open_table(&bb, "");
			block_info_dump(&bb, device);
			blobmsg_close_table(&bb, t);
		}
		blobmsg_close_array(&bb, a);
	}
	ubus_send_reply(ctx, req, bb.head);

	return 0;
}

static const struct ubus_method block_methods[] = {
	UBUS_METHOD("hotplug", block_hotplug, mount_policy),
	UBUS_METHOD("mount", blockd_mount, mount_policy),
	UBUS_METHOD("umount", blockd_umount, mount_policy),
	UBUS_METHOD("info", block_info, info_policy),
};

static struct ubus_object_type block_object_type =
	UBUS_OBJECT_TYPE("block", block_methods);

static struct ubus_object block_object = {
	.name = "block",
	.type = &block_object_type,
	.methods = block_methods,
	.n_methods = ARRAY_SIZE(block_methods),
};

/* send ubus event for successful mounts, useful for procd triggers */
static int send_block_notification(struct ubus_context *ctx, const char *action,
			    const char *devname, const char *target)
{
	struct blob_buf buf = { 0 };
	char evname[16] = "mount.";
	int err;

	if (!ctx)
		return -ENXIO;

	strncat(evname, action, sizeof(evname) - 1);

	blob_buf_init(&buf, 0);

	if (devname)
		blobmsg_add_string(&buf, "device", devname);

	if (target)
		blobmsg_add_string(&buf, "target", target);

	err = ubus_notify(ctx, &block_object, evname, buf.head, -1);

	return err;
}

static void
ubus_connect_handler(struct ubus_context *ctx)
{
	int ret;

	ret = ubus_add_object(ctx, &block_object);
	if (ret)
		fprintf(stderr, "Failed to add object: %s\n", ubus_strerror(ret));
}

static int autofs_umount(void)
{
	umount2(AUTOFS_MOUNT_PATH, MNT_DETACH);
	return 0;
}

static void autofs_read_handler(struct uloop_fd *u, unsigned int events)
{
	union autofs_v5_packet_union pktu;
	const struct autofs_v5_packet *pkt;
	int cmd = AUTOFS_IOC_READY;
	struct stat st;

	while (read(u->fd, &pktu, sizeof(pktu)) == -1) {
		if (errno != EINTR)
			return;
		continue;
	}

	if (pktu.hdr.type != autofs_ptype_missing_indirect) {
		ULOG_ERR("unknown packet type %d\n", pktu.hdr.type);
		return;
	}

	pkt = &pktu.missing_indirect;
        ULOG_ERR("kernel is requesting a mount -> %s\n", pkt->name);
	if (lstat(pkt->name, &st) == -1)
		if (block("autofs", "add", (char *)pkt->name, 1, NULL))
			cmd = AUTOFS_IOC_FAIL;

	if (ioctl(fd_autofs_write, cmd, pkt->wait_queue_token) < 0)
		ULOG_ERR("failed to report back to kernel\n");
}

static void autofs_expire(struct uloop_timeout *t)
{
	struct autofs_packet_expire pkt;

	while (ioctl(fd_autofs_write, AUTOFS_IOC_EXPIRE, &pkt) == 0)
		block("autofs", "remove", pkt.name, 1, NULL);

	uloop_timeout_set(t, AUTOFS_EXPIRE_TIMER);
}

struct uloop_timeout autofs_expire_timer = {
	.cb = autofs_expire,
};

static int autofs_mount(void)
{
	unsigned long autofs_timeout = AUTOFS_TIMEOUT;
	int kproto_version;
	int pipefd[2];
	char source[64];
	char opts[64];

	if (pipe(pipefd) < 0) {
		ULOG_ERR("failed to get kernel pipe\n");
		return -1;
	}

	snprintf(source, sizeof(source), "mountd(pid%u)", getpid());
	snprintf(opts, sizeof(opts), "fd=%d,pgrp=%u,minproto=5,maxproto=5", pipefd[1], (unsigned) getpgrp());
	mkdir(AUTOFS_MOUNT_PATH, 0555);
	if (mount(source, AUTOFS_MOUNT_PATH, "autofs", 0, opts)) {
		ULOG_ERR("unable to mount autofs on %s\n", AUTOFS_MOUNT_PATH);
		close(pipefd[0]);
		close(pipefd[1]);
		return -1;
	}
	close(pipefd[1]);
	fd_autofs_read.fd = pipefd[0];
	fd_autofs_read.cb = autofs_read_handler;
	uloop_fd_add(&fd_autofs_read, ULOOP_READ);

	fd_autofs_write = open(AUTOFS_MOUNT_PATH, O_RDONLY);
	if(fd_autofs_write < 0) {
		autofs_umount();
		ULOG_ERR("failed to open direcory\n");
		return -1;
	}

	ioctl(fd_autofs_write, AUTOFS_IOC_PROTOVER, &kproto_version);
	if (kproto_version != 5) {
		ULOG_ERR("only kernel protocol version 5 is tested. You have %d.\n",
			kproto_version);
		exit(EXIT_FAILURE);
	}
	if (ioctl(fd_autofs_write, AUTOFS_IOC_SETTIMEOUT, &autofs_timeout))
		ULOG_ERR("failed to set autofs timeout\n");

	uloop_timeout_set(&autofs_expire_timer, AUTOFS_EXPIRE_TIMER);

	fcntl(fd_autofs_write, F_SETFD, fcntl(fd_autofs_write, F_GETFD) | FD_CLOEXEC);
	fcntl(fd_autofs_read.fd, F_SETFD, fcntl(fd_autofs_read.fd, F_GETFD) | FD_CLOEXEC);

	return 0;
}

static void blockd_startup_cb(struct uloop_process *p, int stat)
{
	send_block_notification(&conn.ctx, "ready", NULL, NULL);
}

static struct uloop_process startup_process = {
	.cb = blockd_startup_cb,
};

static void blockd_startup(struct uloop_timeout *t)
{
	block("autofs", "start", NULL, 0, &startup_process);
}

struct uloop_timeout startup = {
	.cb = blockd_startup,
};

int main(int argc, char **argv)
{
	/* make sure blockd is in it's own POSIX process group */
	setpgrp();

	ulog_open(ULOG_SYSLOG | ULOG_STDIO, LOG_DAEMON, "blockd");
	uloop_init();

	autofs_mount();

	conn.cb = ubus_connect_handler;
	ubus_auto_connect(&conn);

	uloop_timeout_set(&startup, 1000);

	uloop_run();
	uloop_done();

	autofs_umount();

	vlist_flush_all(&devices);

	return 0;
}