[lxc-devel] [PATCH] introduce lxcapi_add_device_node and lxcapi_remove_device_node to API

[Serge Hallyn]

Quoting S.Çağlar Onur (caglar at 10ur.org):
> Adding block/char devices to running container is a common operation so provide a common
> implementation for users to consume.
> 
> Signed-off-by: S.Çağlar Onur <caglar at 10ur.org>

Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>

> ---
>  src/lxc/lxccontainer.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++
>  src/lxc/lxccontainer.h |   9 +++++
>  2 files changed, 109 insertions(+)
> 
> diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> index ede0113..58eebb0 100644
> --- a/src/lxc/lxccontainer.c
> +++ b/src/lxc/lxccontainer.c
> @@ -2912,6 +2912,104 @@ static bool lxcapi_may_control(struct lxc_container *c)
>  	return lxc_try_cmd(c->name, c->config_path) == 0;
>  }
>  
> +static bool lxcapi_add_device_node(struct lxc_container *c, char *path)
> +{
> +	int ret, size = 32;
> +	struct stat st;
> +	char *value = alloca(size);
> +	char dest_path[MAXPATHLEN];
> +
> +	/* make sure container is running */
> +	if (!c->is_running(c)) {
> +		ERROR("container is not running");
> +		return false;
> +	}
> +
> +	/* make sure that we can access given path */
> +	if(access(path, F_OK) < 0 || lstat(path, &st) < 0)
> +		return false;
> +
> +	/* continue if path is character device or block device */
> +	if S_ISCHR(st.st_mode)
> +		ret = snprintf(value, size, "c %d:%d rwm", major(st.st_rdev), minor(st.st_rdev));
> +	else if S_ISBLK(st.st_mode)
> +		ret = snprintf(value, size, "b %d:%d rwm", major(st.st_rdev), minor(st.st_rdev));
> +	else
> +		return false;
> +
> +	/* check snprintf return code */
> +	if (ret < 0 || ret >= size)
> +		return false;
> +
> +	/* prepare dest_path */
> +	ret = snprintf(dest_path, MAXPATHLEN, "/proc/%d/root%s", c->init_pid(c), path);
> +	if (ret < 0 || ret >= MAXPATHLEN)
> +		return false;
> +
> +	/* remove dest_path if exists in the container */
> +	if(access(dest_path, F_OK) == 0)
> +		unlink(dest_path);
> +
> +	/* create the device node */
> +	if (mknod(dest_path, st.st_mode, st.st_rdev) < 0)
> +		return false;
> +
> +	/* add to device list */
> +	if (!c->set_cgroup_item(c, "devices.allow", value)) {
> +		ERROR("set_cgroup_item failed");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +static bool lxcapi_remove_device_node(struct lxc_container *c, char *path)
> +{
> +	int ret, size = 32;
> +	struct stat st;
> +	char *value = alloca(size);
> +	char dest_path[MAXPATHLEN];
> +
> +	/* make sure container is running */
> +	if (!c->is_running(c)) {
> +		ERROR("container is not running");
> +		return false;
> +	}
> +
> +	/* prepare dest_path */
> +	ret = snprintf(dest_path, MAXPATHLEN, "/proc/%d/root%s", c->init_pid(c), path);
> +	if (ret < 0 || ret >= MAXPATHLEN)
> +		return false;
> +
> +	/* make sure that we can access dest_path */
> +	if(access(dest_path, F_OK) < 0 || lstat(dest_path, &st) < 0)
> +		return false;
> +
> +	/* continue if path is character device or block device */
> +	if S_ISCHR(st.st_mode)
> +		ret = snprintf(value, size, "c %d:%d rwm", major(st.st_rdev), minor(st.st_rdev));
> +	else if S_ISBLK(st.st_mode)
> +		ret = snprintf(value, size, "b %d:%d rwm", major(st.st_rdev), minor(st.st_rdev));
> +	else
> +		return false;
> +
> +	/* check snprintf return code */
> +	if (ret < 0 || ret >= size)
> +		return false;
> +
> +	/* remove dest_path if exists in the container */
> +	if(access(dest_path, F_OK) == 0)
> +		unlink(dest_path);
> +
> +	/* remove from device list */
> +	if (!c->set_cgroup_item(c, "devices.deny", value)) {
> +		ERROR("set_cgroup_item failed");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
>  static int lxcapi_attach_run_waitl(struct lxc_container *c, lxc_attach_options_t *options, const char *program, const char *arg, ...)
>  {
>  	va_list ap;
> @@ -3033,6 +3131,8 @@ struct lxc_container *lxc_container_new(const char *name, const char *configpath
>  	c->snapshot_restore = lxcapi_snapshot_restore;
>  	c->snapshot_destroy = lxcapi_snapshot_destroy;
>  	c->may_control = lxcapi_may_control;
> +	c->add_device_node = lxcapi_add_device_node;
> +	c->remove_device_node = lxcapi_remove_device_node;
>  
>  	/* we'll allow the caller to update these later */
>  	if (lxc_log_init(NULL, "none", NULL, "lxc_container", 0, c->config_path)) {
> diff --git a/src/lxc/lxccontainer.h b/src/lxc/lxccontainer.h
> index 486035a..a94de9a 100644
> --- a/src/lxc/lxccontainer.h
> +++ b/src/lxc/lxccontainer.h
> @@ -236,6 +236,15 @@ struct lxc_container {
>  	 * and the caller may not access it.  Return true otherwise.
>  	 */
>  	bool (*may_control)(struct lxc_container *c);
> +
> +	/*
> +	 * Returns true if given device succesfully added to container
> +	 */
> +	bool (*add_device_node)(struct lxc_container *c, char *path);
> +	/*
> +	 * Returns true if given device succesfully removed from container
> +	 */
> +	bool (*remove_device_node)(struct lxc_container *c, char *path);
>  };
>  
>  struct lxc_snapshot {
> -- 
> 1.8.3.2
> 
> 
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