1// SPDX-License-Identifier: GPL-2.0
  2#define _GNU_SOURCE
  3#include <sched.h>
  4#include <sys/mount.h>
  5#include <sys/stat.h>
  6#include <sys/types.h>
  7#include <linux/limits.h>
  8#include <stdio.h>
  9#include <stdlib.h>
 10#include <linux/sched.h>
 11#include <fcntl.h>
 12#include <unistd.h>
 13#include <ftw.h>
 14
 15#include "cgroup_helpers.h"
 16#include "bpf_util.h"
 17
 18/*
 19 * To avoid relying on the system setup, when setup_cgroup_env is called
 20 * we create a new mount namespace, and cgroup namespace. The cgroupv2
 21 * root is mounted at CGROUP_MOUNT_PATH. Unfortunately, most people don't
 22 * have cgroupv2 enabled at this point in time. It's easier to create our
 23 * own mount namespace and manage it ourselves. We assume /mnt exists.
 24 *
 25 * Related cgroupv1 helpers are named *classid*(), since we only use the
 26 * net_cls controller for tagging net_cls.classid. We assume the default
 27 * mount under /sys/fs/cgroup/net_cls, which should be the case for the
 28 * vast majority of users.
 29 */
 30
 31#define WALK_FD_LIMIT			16
 32
 33#define CGROUP_MOUNT_PATH		"/mnt"
 34#define CGROUP_MOUNT_DFLT		"/sys/fs/cgroup"
 35#define NETCLS_MOUNT_PATH		CGROUP_MOUNT_DFLT "/net_cls"
 36#define CGROUP_WORK_DIR			"/cgroup-test-work-dir"
 37
 38#define format_cgroup_path_pid(buf, path, pid) \
 39	snprintf(buf, sizeof(buf), "%s%s%d%s", CGROUP_MOUNT_PATH, \
 40	CGROUP_WORK_DIR, pid, path)
 41
 42#define format_cgroup_path(buf, path) \
 43	format_cgroup_path_pid(buf, path, getpid())
 44
 45#define format_parent_cgroup_path(buf, path) \
 46	format_cgroup_path_pid(buf, path, getppid())
 47
 48#define format_classid_path(buf)				\
 49	snprintf(buf, sizeof(buf), "%s%s", NETCLS_MOUNT_PATH,	\
 50		 CGROUP_WORK_DIR)
 51
 52static int __enable_controllers(const char *cgroup_path, const char *controllers)
 53{
 54	char path[PATH_MAX + 1];
 55	char enable[PATH_MAX + 1];
 56	char *c, *c2;
 57	int fd, cfd;
 58	ssize_t len;
 59
 60	/* If not controllers are passed, enable all available controllers */
 61	if (!controllers) {
 62		snprintf(path, sizeof(path), "%s/cgroup.controllers",
 63			 cgroup_path);
 64		fd = open(path, O_RDONLY);
 65		if (fd < 0) {
 66			log_err("Opening cgroup.controllers: %s", path);
 67			return 1;
 68		}
 69		len = read(fd, enable, sizeof(enable) - 1);
 70		if (len < 0) {
 71			close(fd);
 72			log_err("Reading cgroup.controllers: %s", path);
 73			return 1;
 74		} else if (len == 0) { /* No controllers to enable */
 75			close(fd);
 76			return 0;
 77		}
 78		enable[len] = 0;
 79		close(fd);
 80	} else {
 81		bpf_strlcpy(enable, controllers, sizeof(enable));
 82	}
 83
 84	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
 85	cfd = open(path, O_RDWR);
 86	if (cfd < 0) {
 87		log_err("Opening cgroup.subtree_control: %s", path);
 88		return 1;
 89	}
 90
 91	for (c = strtok_r(enable, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
 92		if (dprintf(cfd, "+%s\n", c) <= 0) {
 93			log_err("Enabling controller %s: %s", c, path);
 94			close(cfd);
 95			return 1;
 96		}
 97	}
 98	close(cfd);
 99	return 0;
100}
101
102/**
103 * enable_controllers() - Enable cgroup v2 controllers
104 * @relative_path: The cgroup path, relative to the workdir
105 * @controllers: List of controllers to enable in cgroup.controllers format
106 *
107 *
108 * Enable given cgroup v2 controllers, if @controllers is NULL, enable all
109 * available controllers.
110 *
111 * If successful, 0 is returned.
112 */
113int enable_controllers(const char *relative_path, const char *controllers)
114{
115	char cgroup_path[PATH_MAX + 1];
116
117	format_cgroup_path(cgroup_path, relative_path);
118	return __enable_controllers(cgroup_path, controllers);
119}
120
121static int __write_cgroup_file(const char *cgroup_path, const char *file,
122			       const char *buf)
123{
124	char file_path[PATH_MAX + 1];
125	int fd;
126
127	snprintf(file_path, sizeof(file_path), "%s/%s", cgroup_path, file);
128	fd = open(file_path, O_RDWR);
129	if (fd < 0) {
130		log_err("Opening %s", file_path);
131		return 1;
132	}
133
134	if (dprintf(fd, "%s", buf) <= 0) {
135		log_err("Writing to %s", file_path);
136		close(fd);
137		return 1;
138	}
139	close(fd);
140	return 0;
141}
142
143/**
144 * write_cgroup_file() - Write to a cgroup file
145 * @relative_path: The cgroup path, relative to the workdir
146 * @file: The name of the file in cgroupfs to write to
147 * @buf: Buffer to write to the file
148 *
149 * Write to a file in the given cgroup's directory.
150 *
151 * If successful, 0 is returned.
152 */
153int write_cgroup_file(const char *relative_path, const char *file,
154		      const char *buf)
155{
156	char cgroup_path[PATH_MAX - 24];
157
158	format_cgroup_path(cgroup_path, relative_path);
159	return __write_cgroup_file(cgroup_path, file, buf);
160}
161
162/**
163 * write_cgroup_file_parent() - Write to a cgroup file in the parent process
164 *                              workdir
165 * @relative_path: The cgroup path, relative to the parent process workdir
166 * @file: The name of the file in cgroupfs to write to
167 * @buf: Buffer to write to the file
168 *
169 * Write to a file in the given cgroup's directory under the parent process
170 * workdir.
171 *
172 * If successful, 0 is returned.
173 */
174int write_cgroup_file_parent(const char *relative_path, const char *file,
175			     const char *buf)
176{
177	char cgroup_path[PATH_MAX - 24];
178
179	format_parent_cgroup_path(cgroup_path, relative_path);
180	return __write_cgroup_file(cgroup_path, file, buf);
181}
182
183/**
184 * setup_cgroup_environment() - Setup the cgroup environment
185 *
186 * After calling this function, cleanup_cgroup_environment should be called
187 * once testing is complete.
188 *
189 * This function will print an error to stderr and return 1 if it is unable
190 * to setup the cgroup environment. If setup is successful, 0 is returned.
191 */
192int setup_cgroup_environment(void)
193{
194	char cgroup_workdir[PATH_MAX - 24];
195
196	format_cgroup_path(cgroup_workdir, "");
197
198	if (unshare(CLONE_NEWNS)) {
199		log_err("unshare");
200		return 1;
201	}
202
203	if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
204		log_err("mount fakeroot");
205		return 1;
206	}
207
208	if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL) && errno != EBUSY) {
209		log_err("mount cgroup2");
210		return 1;
211	}
212
213	/* Cleanup existing failed runs, now that the environment is setup */
214	cleanup_cgroup_environment();
215
216	if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
217		log_err("mkdir cgroup work dir");
218		return 1;
219	}
220
221	/* Enable all available controllers to increase test coverage */
222	if (__enable_controllers(CGROUP_MOUNT_PATH, NULL) ||
223	    __enable_controllers(cgroup_workdir, NULL))
224		return 1;
225
226	return 0;
227}
228
229static int nftwfunc(const char *filename, const struct stat *statptr,
230		    int fileflags, struct FTW *pfwt)
231{
232	if ((fileflags & FTW_D) && rmdir(filename))
233		log_err("Removing cgroup: %s", filename);
234	return 0;
235}
236
237static int join_cgroup_from_top(const char *cgroup_path)
238{
239	char cgroup_procs_path[PATH_MAX + 1];
240	pid_t pid = getpid();
241	int fd, rc = 0;
242
243	snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
244		 "%s/cgroup.procs", cgroup_path);
245
246	fd = open(cgroup_procs_path, O_WRONLY);
247	if (fd < 0) {
248		log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
249		return 1;
250	}
251
252	if (dprintf(fd, "%d\n", pid) < 0) {
253		log_err("Joining Cgroup");
254		rc = 1;
255	}
256
257	close(fd);
258	return rc;
259}
260
261/**
262 * join_cgroup() - Join a cgroup
263 * @relative_path: The cgroup path, relative to the workdir, to join
264 *
265 * This function expects a cgroup to already be created, relative to the cgroup
266 * work dir, and it joins it. For example, passing "/my-cgroup" as the path
267 * would actually put the calling process into the cgroup
268 * "/cgroup-test-work-dir/my-cgroup"
269 *
270 * On success, it returns 0, otherwise on failure it returns 1.
271 */
272int join_cgroup(const char *relative_path)
273{
274	char cgroup_path[PATH_MAX + 1];
275
276	format_cgroup_path(cgroup_path, relative_path);
277	return join_cgroup_from_top(cgroup_path);
278}
279
280/**
281 * join_parent_cgroup() - Join a cgroup in the parent process workdir
282 * @relative_path: The cgroup path, relative to parent process workdir, to join
283 *
284 * See join_cgroup().
285 *
286 * On success, it returns 0, otherwise on failure it returns 1.
287 */
288int join_parent_cgroup(const char *relative_path)
289{
290	char cgroup_path[PATH_MAX + 1];
291
292	format_parent_cgroup_path(cgroup_path, relative_path);
293	return join_cgroup_from_top(cgroup_path);
294}
295
296/**
297 * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
298 *
299 * This is an idempotent function to delete all temporary cgroups that
300 * have been created during the test, including the cgroup testing work
301 * directory.
302 *
303 * At call time, it moves the calling process to the root cgroup, and then
304 * runs the deletion process. It is idempotent, and should not fail, unless
305 * a process is lingering.
306 *
307 * On failure, it will print an error to stderr, and try to continue.
308 */
309void cleanup_cgroup_environment(void)
310{
311	char cgroup_workdir[PATH_MAX + 1];
312
313	format_cgroup_path(cgroup_workdir, "");
314	join_cgroup_from_top(CGROUP_MOUNT_PATH);
315	nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
316}
317
318/**
319 * get_root_cgroup() - Get the FD of the root cgroup
320 *
321 * On success, it returns the file descriptor. On failure, it returns -1.
322 * If there is a failure, it prints the error to stderr.
323 */
324int get_root_cgroup(void)
325{
326	int fd;
327
328	fd = open(CGROUP_MOUNT_PATH, O_RDONLY);
329	if (fd < 0) {
330		log_err("Opening root cgroup");
331		return -1;
332	}
333	return fd;
334}
335
336/*
337 * remove_cgroup() - Remove a cgroup
338 * @relative_path: The cgroup path, relative to the workdir, to remove
339 *
340 * This function expects a cgroup to already be created, relative to the cgroup
341 * work dir. It also expects the cgroup doesn't have any children or live
342 * processes and it removes the cgroup.
343 *
344 * On failure, it will print an error to stderr.
345 */
346void remove_cgroup(const char *relative_path)
347{
348	char cgroup_path[PATH_MAX + 1];
349
350	format_cgroup_path(cgroup_path, relative_path);
351	if (rmdir(cgroup_path))
352		log_err("rmdiring cgroup %s .. %s", relative_path, cgroup_path);
353}
354
355/**
356 * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
357 * @relative_path: The cgroup path, relative to the workdir, to join
358 *
359 * This function creates a cgroup under the top level workdir and returns the
360 * file descriptor. It is idempotent.
361 *
362 * On success, it returns the file descriptor. On failure it returns -1.
363 * If there is a failure, it prints the error to stderr.
364 */
365int create_and_get_cgroup(const char *relative_path)
366{
367	char cgroup_path[PATH_MAX + 1];
368	int fd;
369
370	format_cgroup_path(cgroup_path, relative_path);
371	if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
372		log_err("mkdiring cgroup %s .. %s", relative_path, cgroup_path);
373		return -1;
374	}
375
376	fd = open(cgroup_path, O_RDONLY);
377	if (fd < 0) {
378		log_err("Opening Cgroup");
379		return -1;
380	}
381
382	return fd;
383}
384
385/**
386 * get_cgroup_id() - Get cgroup id for a particular cgroup path
387 * @relative_path: The cgroup path, relative to the workdir, to join
388 *
389 * On success, it returns the cgroup id. On failure it returns 0,
390 * which is an invalid cgroup id.
391 * If there is a failure, it prints the error to stderr.
392 */
393unsigned long long get_cgroup_id(const char *relative_path)
394{
395	int dirfd, err, flags, mount_id, fhsize;
396	union {
397		unsigned long long cgid;
398		unsigned char raw_bytes[8];
399	} id;
400	char cgroup_workdir[PATH_MAX + 1];
401	struct file_handle *fhp, *fhp2;
402	unsigned long long ret = 0;
403
404	format_cgroup_path(cgroup_workdir, relative_path);
405
406	dirfd = AT_FDCWD;
407	flags = 0;
408	fhsize = sizeof(*fhp);
409	fhp = calloc(1, fhsize);
410	if (!fhp) {
411		log_err("calloc");
412		return 0;
413	}
414	err = name_to_handle_at(dirfd, cgroup_workdir, fhp, &mount_id, flags);
415	if (err >= 0 || fhp->handle_bytes != 8) {
416		log_err("name_to_handle_at");
417		goto free_mem;
418	}
419
420	fhsize = sizeof(struct file_handle) + fhp->handle_bytes;
421	fhp2 = realloc(fhp, fhsize);
422	if (!fhp2) {
423		log_err("realloc");
424		goto free_mem;
425	}
426	err = name_to_handle_at(dirfd, cgroup_workdir, fhp2, &mount_id, flags);
427	fhp = fhp2;
428	if (err < 0) {
429		log_err("name_to_handle_at");
430		goto free_mem;
431	}
432
433	memcpy(id.raw_bytes, fhp->f_handle, 8);
434	ret = id.cgid;
435
436free_mem:
437	free(fhp);
438	return ret;
439}
440
441int cgroup_setup_and_join(const char *path) {
442	int cg_fd;
443
444	if (setup_cgroup_environment()) {
445		fprintf(stderr, "Failed to setup cgroup environment\n");
446		return -EINVAL;
447	}
448
449	cg_fd = create_and_get_cgroup(path);
450	if (cg_fd < 0) {
451		fprintf(stderr, "Failed to create test cgroup\n");
452		cleanup_cgroup_environment();
453		return cg_fd;
454	}
455
456	if (join_cgroup(path)) {
457		fprintf(stderr, "Failed to join cgroup\n");
458		cleanup_cgroup_environment();
459		return -EINVAL;
460	}
461	return cg_fd;
462}
463
464/**
465 * setup_classid_environment() - Setup the cgroupv1 net_cls environment
466 *
467 * After calling this function, cleanup_classid_environment should be called
468 * once testing is complete.
469 *
470 * This function will print an error to stderr and return 1 if it is unable
471 * to setup the cgroup environment. If setup is successful, 0 is returned.
472 */
473int setup_classid_environment(void)
474{
475	char cgroup_workdir[PATH_MAX + 1];
476
477	format_classid_path(cgroup_workdir);
478
479	if (mount("tmpfs", CGROUP_MOUNT_DFLT, "tmpfs", 0, NULL) &&
480	    errno != EBUSY) {
481		log_err("mount cgroup base");
482		return 1;
483	}
484
485	if (mkdir(NETCLS_MOUNT_PATH, 0777) && errno != EEXIST) {
486		log_err("mkdir cgroup net_cls");
487		return 1;
488	}
489
490	if (mount("net_cls", NETCLS_MOUNT_PATH, "cgroup", 0, "net_cls") &&
491	    errno != EBUSY) {
492		log_err("mount cgroup net_cls");
493		return 1;
494	}
495
496	cleanup_classid_environment();
497
498	if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
499		log_err("mkdir cgroup work dir");
500		return 1;
501	}
502
503	return 0;
504}
505
506/**
507 * set_classid() - Set a cgroupv1 net_cls classid
508 * @id: the numeric classid
509 *
510 * Writes the passed classid into the cgroup work dir's net_cls.classid
511 * file in order to later on trigger socket tagging.
512 *
513 * On success, it returns 0, otherwise on failure it returns 1. If there
514 * is a failure, it prints the error to stderr.
515 */
516int set_classid(unsigned int id)
517{
518	char cgroup_workdir[PATH_MAX - 42];
519	char cgroup_classid_path[PATH_MAX + 1];
520	int fd, rc = 0;
521
522	format_classid_path(cgroup_workdir);
523	snprintf(cgroup_classid_path, sizeof(cgroup_classid_path),
524		 "%s/net_cls.classid", cgroup_workdir);
525
526	fd = open(cgroup_classid_path, O_WRONLY);
527	if (fd < 0) {
528		log_err("Opening cgroup classid: %s", cgroup_classid_path);
529		return 1;
530	}
531
532	if (dprintf(fd, "%u\n", id) < 0) {
533		log_err("Setting cgroup classid");
534		rc = 1;
535	}
536
537	close(fd);
538	return rc;
539}
540
541/**
542 * join_classid() - Join a cgroupv1 net_cls classid
543 *
544 * This function expects the cgroup work dir to be already created, as we
545 * join it here. This causes the process sockets to be tagged with the given
546 * net_cls classid.
547 *
548 * On success, it returns 0, otherwise on failure it returns 1.
549 */
550int join_classid(void)
551{
552	char cgroup_workdir[PATH_MAX + 1];
553
554	format_classid_path(cgroup_workdir);
555	return join_cgroup_from_top(cgroup_workdir);
556}
557
558/**
559 * cleanup_classid_environment() - Cleanup the cgroupv1 net_cls environment
560 *
561 * At call time, it moves the calling process to the root cgroup, and then
562 * runs the deletion process.
563 *
564 * On failure, it will print an error to stderr, and try to continue.
565 */
566void cleanup_classid_environment(void)
567{
568	char cgroup_workdir[PATH_MAX + 1];
569
570	format_classid_path(cgroup_workdir);
571	join_cgroup_from_top(NETCLS_MOUNT_PATH);
572	nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
573}