path: root/discover/device-handler.c

#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/wait.h>

#include <talloc/talloc.h>
#include <list/list.h>
#include <log/log.h>
#include <pb-protocol/pb-protocol.h>

#include "device-handler.h"
#include "discover-server.h"
#include "parser.h"
#include "udev.h"
#include "paths.h"

#define MOUNT_BIN "/bin/mount"

#define UMOUNT_BIN "/bin/umount"

struct device_handler {
	struct discover_server *server;

	struct device **devices;
	unsigned int n_devices;

	struct list contexts;
};

struct mount_map {
	char *device_path;
	char *mount_point;
};

/**
 * device_handler_add - Add a device to the handler device array.
 */

static void device_handler_add(struct device_handler *handler,
	struct device *device)
{
	handler->n_devices++;
	handler->devices = talloc_realloc(handler, handler->devices,
		struct device *, handler->n_devices);
	handler->devices[handler->n_devices - 1] = device;
}

/**
 * device_handler_remove - Remove a device from the handler device array.
 */

static void device_handler_remove(struct device_handler *handler,
	struct device *device)
{
	unsigned int i;

	for (i = 0; i < handler->n_devices; i++)
		if (handler->devices[i] == device)
			break;

	if (i < handler->n_devices) {
		assert(0 && "unknown device");
		return;
	}

	handler->n_devices--;
	memmove(&handler->devices[i], &handler->devices[i + 1],
		(handler->n_devices - i) * sizeof(handler->devices[0]));
	handler->devices = talloc_realloc(handler, handler->devices,
		struct device *, handler->n_devices);
}

/**
 * device_handler_find - Find a handler device by id.
 */

static struct device *device_handler_find(struct device_handler *handler,
	const char *id)
{
	unsigned int i;

	assert(id);

	for (i = 0; i < handler->n_devices; i++)
		if (handler->devices[i]->id
			&& streq(handler->devices[i]->id, id))
			return handler->devices[i];

	assert(0 && "unknown device");
	return NULL;
}

/**
 * device_handler_get_device_count - Get the count of current handler devices.
 */

int device_handler_get_device_count(const struct device_handler *handler)
{
	return handler->n_devices;
}

/**
 * device_handler_get_device - Get a handler device by index.
 */

const struct device *device_handler_get_device(
	const struct device_handler *handler, unsigned int index)
{
	if (index >= handler->n_devices) {
		assert(0 && "bad index");
		return NULL;
	}

	return handler->devices[index];
}

static int mkdir_recursive(const char *dir)
{
	struct stat statbuf;
	char *str, *sep;
	int mode = 0755;

	if (!*dir)
		return 0;

	if (!stat(dir, &statbuf)) {
		if (!S_ISDIR(statbuf.st_mode)) {
			pb_log("%s: %s exists, but isn't a directory\n",
					__func__, dir);
			return -1;
		}
		return 0;
	}

	str = talloc_strdup(NULL, dir);
	sep = strchr(*str == '/' ? str + 1 : str, '/');

	while (1) {

		/* terminate the path at sep */
		if (sep)
			*sep = '\0';

		if (mkdir(str, mode) && errno != EEXIST) {
			pb_log("mkdir(%s): %s\n", str, strerror(errno));
			return -1;
		}

		if (!sep)
			break;

		/* reset dir to the full path */
		strcpy(str, dir);
		sep = strchr(sep + 1, '/');
	}

	talloc_free(str);

	return 0;
}

static int rmdir_recursive(const char *base, const char *dir)
{
	char *cur, *pos;

	/* sanity check: make sure that dir is within base */
	if (strncmp(base, dir, strlen(base)))
		return -1;

	cur = talloc_strdup(NULL, dir);

	while (strcmp(base, dir)) {

		rmdir(dir);

		/* null-terminate at the last slash */
		pos = strrchr(dir, '/');
		if (!pos)
			break;

		*pos = '\0';
	}

	talloc_free(cur);

	return 0;
}

static void setup_device_links(struct discover_context *ctx)
{
	struct link {
		char *env, *dir;
	} *link, links[] = {
		{
			.env = "ID_FS_UUID",
			.dir = "disk/by-uuid"
		},
		{
			.env = "ID_FS_LABEL",
			.dir = "disk/by-label"
		},
		{
			.env = NULL
		}
	};

	for (link = links; link->env; link++) {
		char *enc, *dir, *path;
		const char *value;

		value = udev_event_param(ctx->event, link->env);
		if (!value || !*value)
			continue;

		enc = encode_label(ctx, value);
		dir = join_paths(ctx, mount_base(), link->dir);
		path = join_paths(ctx, dir, value);

		if (!mkdir_recursive(dir)) {
			unlink(path);
			if (symlink(ctx->mount_path, path)) {
				pb_log("symlink(%s,%s): %s\n",
						ctx->mount_path, path,
						strerror(errno));
				talloc_free(path);
			} else {
				int i = ctx->n_links++;
				ctx->links = talloc_realloc(ctx,
						ctx->links, char *,
						ctx->n_links);
				ctx->links[i] = path;
			}

		}

		talloc_free(dir);
		talloc_free(enc);
	}
}

static void remove_device_links(struct discover_context *ctx)
{
	int i;

	for (i = 0; i < ctx->n_links; i++)
		unlink(ctx->links[i]);
}

static int mount_device(struct discover_context *ctx)
{
	const char *mountpoint;
	int status;
	pid_t pid;

	if (!ctx->mount_path) {
		mountpoint = mountpoint_for_device(ctx->device_path);
		ctx->mount_path = talloc_strdup(ctx, mountpoint);
	}

	if (mkdir_recursive(ctx->mount_path))
		pb_log("couldn't create mount directory %s: %s\n",
				ctx->mount_path, strerror(errno));

	pid = fork();
	if (pid == -1) {
		pb_log("%s: fork failed: %s\n", __func__, strerror(errno));
		goto out_rmdir;
	}

	if (pid == 0) {
		execl(MOUNT_BIN, MOUNT_BIN, ctx->device_path, ctx->mount_path,
				"-o", "ro", NULL);
		exit(EXIT_FAILURE);
	}

	if (waitpid(pid, &status, 0) == -1) {
		pb_log("%s: waitpid failed: %s\n", __func__,
				strerror(errno));
		goto out_rmdir;
	}

	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
		pb_log("%s: mount failed (%d): %s\n", __func__,
			WEXITSTATUS(status), ctx->event->device);
		goto out_rmdir;
	}

	setup_device_links(ctx);
	return 0;

out_rmdir:
	rmdir_recursive(mount_base(), ctx->mount_path);
	return -1;
}

static int umount_device(struct discover_context *ctx)
{
	int status;
	pid_t pid;

	remove_device_links(ctx);

	pid = fork();
	if (pid == -1) {
		pb_log("%s: fork failed: %s\n", __func__, strerror(errno));
		return -1;
	}

	if (pid == 0) {
		execl(UMOUNT_BIN, UMOUNT_BIN, ctx->mount_path, NULL);
		exit(EXIT_FAILURE);
	}

	if (waitpid(pid, &status, 0) == -1) {
		pb_log("%s: waitpid failed: %s\n", __func__,
				strerror(errno));
		return -1;
	}

	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
		return -1;

	rmdir_recursive(mount_base(), ctx->mount_path);

	return 0;
}

static struct discover_context *find_context(struct device_handler *handler,
		const char *id)
{
	struct discover_context *ctx;

	list_for_each_entry(&handler->contexts, ctx, list) {
		if (!strcmp(ctx->id, id))
			return ctx;
	}

	return NULL;
}

static int destroy_context(void *arg)
{
	struct discover_context *ctx = arg;

	list_remove(&ctx->list);
	umount_device(ctx);

	return 0;
}

static int handle_add_event(struct device_handler *handler,
		struct udev_event *event)
{
	struct discover_context *ctx;
	const char *devname;
	int rc;

	/* create our context */
	ctx = talloc(handler, struct discover_context);
	ctx->event = event;
	ctx->mount_path = NULL;
	ctx->links = NULL;
	ctx->n_links = 0;

	ctx->id = talloc_strdup(ctx, event->device);

	devname = udev_event_param(ctx->event, "DEVNAME");
	if (!devname) {
		pb_log("no devname for %s?\n", event->device);
		return 0;
	}

	ctx->device_path = talloc_strdup(ctx, devname);

	rc = mount_device(ctx);
	if (rc) {
		talloc_free(ctx);
		return 0;
	}

	list_add(&handler->contexts, &ctx->list);
	talloc_set_destructor(ctx, destroy_context);

	/* set up the top-level device */
	ctx->device = talloc_zero(ctx, struct device);
	ctx->device->id = talloc_strdup(ctx->device, ctx->id);
	list_init(&ctx->device->boot_options);

	/* run the parsers */
	iterate_parsers(ctx);

	/* add device to handler device array */
	device_handler_add(handler, ctx->device);

	discover_server_notify_add(handler->server, ctx->device);

	return 0;
}

static int handle_remove_event(struct device_handler *handler,
		struct udev_event *event)
{
	struct discover_context *ctx;

	ctx = find_context(handler, event->device);
	if (!ctx)
		return 0;

	discover_server_notify_remove(handler->server, ctx->device);

	/* remove device from handler device array */
	device_handler_remove(handler, ctx->device);

	talloc_free(ctx);

	return 0;
}

int device_handler_event(struct device_handler *handler,
		struct udev_event *event)
{
	int rc;

	switch (event->action) {
	case UDEV_ACTION_ADD:
		rc = handle_add_event(handler, event);
		break;

	case UDEV_ACTION_REMOVE:
		rc = handle_remove_event(handler, event);
		break;
	}

	return rc;
}

struct device_handler *device_handler_init(struct discover_server *server)
{
	struct device_handler *handler;

	handler = talloc(NULL, struct device_handler);
	handler->devices = NULL;
	handler->n_devices = 0;
	handler->server = server;

	list_init(&handler->contexts);

	/* set up our mount point base */
	mkdir_recursive(mount_base());

	parser_init();

	return handler;
}

void device_handler_destroy(struct device_handler *handler)
{
	talloc_free(handler);
}