bindings: fix struct lxcfs_opts by making it versioned

Signed-off-by: Christian Brauner <[email protected]>

Author: Christian Brauner

src/bindings.c

@@ -58,6 +58,8 @@
 
 static bool can_use_pidfd;
 static bool can_use_swap;
+static bool can_use_sys_cpu;
+static bool has_versioned_opts;
 
 static volatile sig_atomic_t reload_successful;
 
@@ -71,6 +73,16 @@ bool liblxcfs_can_use_swap(void)
 	return can_use_swap;
 }
 
+bool liblxcfs_can_use_sys_cpu(void)
+{
+	return can_use_sys_cpu;
+}
+
+bool liblxcfs_has_versioned_opts(void)
+{
+	return has_versioned_opts;
+}
+
 /* Define pivot_root() if missing from the C library */
 #ifndef HAVE_PIVOT_ROOT
 static int pivot_root(const char *new_root, const char *put_old)
@@ -929,3 +941,11 @@ static void __attribute__((destructor)) lxcfs_exit(void)
 	free_cpuview();
 	cgroup_exit(cgroup_ops);
 }
+
+void *lxcfs_fuse_init(struct fuse_conn_info *conn, struct fuse_config *cfg)
+{
+	struct fuse_context *fc = fuse_get_context();
+	can_use_sys_cpu = true;
+	has_versioned_opts = true;
+	return fc->private_data;
+}

src/bindings.h

@@ -14,6 +14,7 @@
 #define _FILE_OFFSET_BITS 64
 
 #include <fuse.h>
+#include <linux/types.h>
 #include <signal.h>
 #include <stdbool.h>
 #include <stdio.h>
@@ -91,6 +92,11 @@ struct lxcfs_opts {
 	bool swap_off;
 	bool use_pidfd;
 	bool use_cfs;
+	/*
+	 * Ideally we'd version by size but because of backwards compatability
+	 * and the use of bool instead of explicited __u32 and __u64 we can't.
+	 */
+	__u32 version;
 };
 
 typedef enum lxcfs_opt_t {
@@ -106,6 +112,8 @@ extern void prune_init_slice(char *cg);
 extern bool supports_pidfd(void);
 extern bool liblxcfs_functional(void);
 extern bool liblxcfs_can_use_swap(void);
+extern bool liblxcfs_can_use_sys_cpu(void);
+extern bool liblxcfs_has_versioned_opts(void);
 
 static inline bool lxcfs_has_opt(struct lxcfs_opts *opts, lxcfs_opt_t opt)
 {
@@ -156,4 +164,7 @@ static inline pid_t lxcfs_clone(int (*fn)(void *), void *arg, int flags)
 	return pid;
 }
 
+__visible extern void *lxcfs_fuse_init(struct fuse_conn_info *conn,
+				       struct fuse_config *cfg);
+
 #endif /* __LXCFS_BINDINGS_H */

src/lxcfs.c

@@ -1015,13 +1015,28 @@ int lxcfs_chmod(const char *path, mode_t mode)
 	return -ENOENT;
 }
 
+static void *lxcfs_init(struct fuse_conn_info *conn, struct fuse_config *cfg)
+{
+	char *error;
+	void *(*__lxcfs_fuse_init)(struct fuse_conn_info * conn, struct fuse_config * cfg);
+
+	dlerror();
+	__lxcfs_fuse_init = (void *(*)(struct fuse_conn_info * conn, struct fuse_config * cfg))dlsym(dlopen_handle, "lxcfs_fuse_init");
+	error = dlerror();
+	if (error)
+		return log_error(NULL, "%s - Failed to find lxcfs_fuse_init()", error);
+
+	return __lxcfs_fuse_init(conn, cfg);
+}
+
 const struct fuse_operations lxcfs_ops = {
 	.access		= lxcfs_access,
 	.chmod		= lxcfs_chmod,
 	.chown		= lxcfs_chown,
 	.flush		= lxcfs_flush,
 	.fsync		= lxcfs_fsync,
 	.getattr	= lxcfs_getattr,
+	.init		= lxcfs_init,
 	.mkdir		= lxcfs_mkdir,
 	.open		= lxcfs_open,
 	.opendir	= lxcfs_opendir,
@@ -1045,7 +1060,6 @@ const struct fuse_operations lxcfs_ops = {
 	.getdir		= NULL,
 #endif
 	.getxattr	= NULL,
-	.init		= NULL,
 	.link		= NULL,
 	.listxattr	= NULL,
 	.mknod		= NULL,
@@ -1195,6 +1209,7 @@ int main(int argc, char *argv[])
 	opts->swap_off = false;
 	opts->use_pidfd = false;
 	opts->use_cfs = false;
+	opts->version = 1;
 
 	while ((c = getopt_long(argc, argv, "dulfhvso:p:", long_options, &idx)) != -1) {
 		switch (c) {