1#define _GNU_SOURCE
  2#include <sched.h>
  3#include <sys/mount.h>
  4#include <sys/stat.h>
  5#include <sys/types.h>
  6#include <linux/limits.h>
  7#include <stdio.h>
  8#include <linux/sched.h>
  9#include <fcntl.h>
 10#include <unistd.h>
 11#include <ftw.h>
 12
 13
 14#include "cgroup_helpers.h"
 15
 16/*
 17 * To avoid relying on the system setup, when setup_cgroup_env is called
 18 * we create a new mount namespace, and cgroup namespace. The cgroup2
 19 * root is mounted at CGROUP_MOUNT_PATH
 20 *
 21 * Unfortunately, most people don't have cgroupv2 enabled at this point in time.
 22 * It's easier to create our own mount namespace and manage it ourselves.
 23 *
 24 * We assume /mnt exists.
 25 */
 26
 27#define WALK_FD_LIMIT			16
 28#define CGROUP_MOUNT_PATH		"/mnt"
 29#define CGROUP_WORK_DIR			"/cgroup-test-work-dir"
 30#define format_cgroup_path(buf, path) \
 31	snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
 32		 CGROUP_WORK_DIR, path)
 33
 34/**
 35 * setup_cgroup_environment() - Setup the cgroup environment
 36 *
 37 * After calling this function, cleanup_cgroup_environment should be called
 38 * once testing is complete.
 39 *
 40 * This function will print an error to stderr and return 1 if it is unable
 41 * to setup the cgroup environment. If setup is successful, 0 is returned.
 42 */
 43int setup_cgroup_environment(void)
 44{
 45	char cgroup_workdir[PATH_MAX + 1];
 46
 47	format_cgroup_path(cgroup_workdir, "");
 48
 49	if (unshare(CLONE_NEWNS)) {
 50		log_err("unshare");
 51		return 1;
 52	}
 53
 54	if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
 55		log_err("mount fakeroot");
 56		return 1;
 57	}
 58
 59	if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL)) {
 60		log_err("mount cgroup2");
 61		return 1;
 62	}
 63
 64	/* Cleanup existing failed runs, now that the environment is setup */
 65	cleanup_cgroup_environment();
 66
 67	if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
 68		log_err("mkdir cgroup work dir");
 69		return 1;
 70	}
 71
 72	return 0;
 73}
 74
 75static int nftwfunc(const char *filename, const struct stat *statptr,
 76		    int fileflags, struct FTW *pfwt)
 77{
 78	if ((fileflags & FTW_D) && rmdir(filename))
 79		log_err("Removing cgroup: %s", filename);
 80	return 0;
 81}
 82
 83
 84static int join_cgroup_from_top(char *cgroup_path)
 85{
 86	char cgroup_procs_path[PATH_MAX + 1];
 87	pid_t pid = getpid();
 88	int fd, rc = 0;
 89
 90	snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
 91		 "%s/cgroup.procs", cgroup_path);
 92
 93	fd = open(cgroup_procs_path, O_WRONLY);
 94	if (fd < 0) {
 95		log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
 96		return 1;
 97	}
 98
 99	if (dprintf(fd, "%d\n", pid) < 0) {
100		log_err("Joining Cgroup");
101		rc = 1;
102	}
103
104	close(fd);
105	return rc;
106}
107
108/**
109 * join_cgroup() - Join a cgroup
110 * @path: The cgroup path, relative to the workdir, to join
111 *
112 * This function expects a cgroup to already be created, relative to the cgroup
113 * work dir, and it joins it. For example, passing "/my-cgroup" as the path
114 * would actually put the calling process into the cgroup
115 * "/cgroup-test-work-dir/my-cgroup"
116 *
117 * On success, it returns 0, otherwise on failure it returns 1.
118 */
119int join_cgroup(char *path)
120{
121	char cgroup_path[PATH_MAX + 1];
122
123	format_cgroup_path(cgroup_path, path);
124	return join_cgroup_from_top(cgroup_path);
125}
126
127/**
128 * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
129 *
130 * This is an idempotent function to delete all temporary cgroups that
131 * have been created during the test, including the cgroup testing work
132 * directory.
133 *
134 * At call time, it moves the calling process to the root cgroup, and then
135 * runs the deletion process. It is idempotent, and should not fail, unless
136 * a process is lingering.
137 *
138 * On failure, it will print an error to stderr, and try to continue.
139 */
140void cleanup_cgroup_environment(void)
141{
142	char cgroup_workdir[PATH_MAX + 1];
143
144	format_cgroup_path(cgroup_workdir, "");
145	join_cgroup_from_top(CGROUP_MOUNT_PATH);
146	nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
147}
148
149/**
150 * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
151 * @path: The cgroup path, relative to the workdir, to join
152 *
153 * This function creates a cgroup under the top level workdir and returns the
154 * file descriptor. It is idempotent.
155 *
156 * On success, it returns the file descriptor. On failure it returns 0.
157 * If there is a failure, it prints the error to stderr.
158 */
159int create_and_get_cgroup(char *path)
160{
161	char cgroup_path[PATH_MAX + 1];
162	int fd;
163
164	format_cgroup_path(cgroup_path, path);
165	if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
166		log_err("mkdiring cgroup");
167		return 0;
168	}
169
170	fd = open(cgroup_path, O_RDONLY);
171	if (fd < 0) {
172		log_err("Opening Cgroup");
173		return 0;
174	}
175
176	return fd;
177}