// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <sched.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <linux/limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/sched.h>
#include <fcntl.h>
#include <unistd.h>
#include <ftw.h>
#include "cgroup_helpers.h"
#include "bpf_util.h"
/*
* To avoid relying on the system setup, when setup_cgroup_env is called
* we create a new mount namespace, and cgroup namespace. The cgroupv2
* root is mounted at CGROUP_MOUNT_PATH. Unfortunately, most people don't
* have cgroupv2 enabled at this point in time. It's easier to create our
* own mount namespace and manage it ourselves. We assume /mnt exists.
*
* Related cgroupv1 helpers are named *classid*(), since we only use the
* net_cls controller for tagging net_cls.classid. We assume the default
* mount under /sys/fs/cgroup/net_cls, which should be the case for the
* vast majority of users.
*/
#define WALK_FD_LIMIT 16
#define CGROUP_MOUNT_PATH "/mnt"
#define CGROUP_MOUNT_DFLT "/sys/fs/cgroup"
#define NETCLS_MOUNT_PATH CGROUP_MOUNT_DFLT "/net_cls"
#define CGROUP_WORK_DIR "/cgroup-test-work-dir"
#define format_cgroup_path_pid(buf, path, pid) \
snprintf(buf, sizeof(buf), "%s%s%d%s", CGROUP_MOUNT_PATH, \
CGROUP_WORK_DIR, pid, path)
#define format_cgroup_path(buf, path) \
format_cgroup_path_pid(buf, path, getpid())
#define format_parent_cgroup_path(buf, path) \
format_cgroup_path_pid(buf, path, getppid())
#define format_classid_path_pid(buf, pid) \
snprintf(buf, sizeof(buf), "%s%s%d", NETCLS_MOUNT_PATH, \
CGROUP_WORK_DIR, pid)
#define format_classid_path(buf) \
format_classid_path_pid(buf, getpid())
static __thread bool cgroup_workdir_mounted;
static void __cleanup_cgroup_environment(void);
static int __enable_controllers(const char *cgroup_path, const char *controllers)
{
char path[PATH_MAX + 1];
char enable[PATH_MAX + 1];
char *c, *c2;
int fd, cfd;
ssize_t len;
/* If not controllers are passed, enable all available controllers */
if (!controllers) {
snprintf(path, sizeof(path), "%s/cgroup.controllers",
cgroup_path);
fd = open(path, O_RDONLY);
if (fd < 0) {
log_err("Opening cgroup.controllers: %s", path);
return 1;
}
len = read(fd, enable, sizeof(enable) - 1);
if (len < 0) {
close(fd);
log_err("Reading cgroup.controllers: %s", path);
return 1;
} else if (len == 0) { /* No controllers to enable */
close(fd);
return 0;
}
enable[len] = 0;
close(fd);
} else {
bpf_strlcpy(enable, controllers, sizeof(enable));
}
snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
cfd = open(path, O_RDWR);
if (cfd < 0) {
log_err("Opening cgroup.subtree_control: %s", path);
return 1;
}
for (c = strtok_r(enable, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
if (dprintf(cfd, "+%s\n", c) <= 0) {
log_err("Enabling controller %s: %s", c, path);
close(cfd);
return 1;
}
}
close(cfd);
return 0;
}
/**
* enable_controllers() - Enable cgroup v2 controllers
* @relative_path: The cgroup path, relative to the workdir
* @controllers: List of controllers to enable in cgroup.controllers format
*
*
* Enable given cgroup v2 controllers, if @controllers is NULL, enable all
* available controllers.
*
* If successful, 0 is returned.
*/
int enable_controllers(const char *relative_path, const char *controllers)
{
char cgroup_path[PATH_MAX + 1];
format_cgroup_path(cgroup_path, relative_path);
return __enable_controllers(cgroup_path, controllers);
}
static int __write_cgroup_file(const char *cgroup_path, const char *file,
const char *buf)
{
char file_path[PATH_MAX + 1];
int fd;
snprintf(file_path, sizeof(file_path), "%s/%s", cgroup_path, file);
fd = open(file_path, O_RDWR);
if (fd < 0) {
log_err("Opening %s", file_path);
return 1;
}
if (dprintf(fd, "%s", buf) <= 0) {
log_err("Writing to %s", file_path);
close(fd);
return 1;
}
close(fd);
return 0;
}
/**
* write_cgroup_file() - Write to a cgroup file
* @relative_path: The cgroup path, relative to the workdir
* @file: The name of the file in cgroupfs to write to
* @buf: Buffer to write to the file
*
* Write to a file in the given cgroup's directory.
*
* If successful, 0 is returned.
*/
int write_cgroup_file(const char *relative_path, const char *file,
const char *buf)
{
char cgroup_path[PATH_MAX - 24];
format_cgroup_path(cgroup_path, relative_path);
return __write_cgroup_file(cgroup_path, file, buf);
}
/**
* write_cgroup_file_parent() - Write to a cgroup file in the parent process
* workdir
* @relative_path: The cgroup path, relative to the parent process workdir
* @file: The name of the file in cgroupfs to write to
* @buf: Buffer to write to the file
*
* Write to a file in the given cgroup's directory under the parent process
* workdir.
*
* If successful, 0 is returned.
*/
int write_cgroup_file_parent(const char *relative_path, const char *file,
const char *buf)
{
char cgroup_path[PATH_MAX - 24];
format_parent_cgroup_path(cgroup_path, relative_path);
return __write_cgroup_file(cgroup_path, file, buf);
}
/**
* setup_cgroup_environment() - Setup the cgroup environment
*
* After calling this function, cleanup_cgroup_environment should be called
* once testing is complete.
*
* This function will print an error to stderr and return 1 if it is unable
* to setup the cgroup environment. If setup is successful, 0 is returned.
*/
int setup_cgroup_environment(void)
{
char cgroup_workdir[PATH_MAX - 24];
format_cgroup_path(cgroup_workdir, "");
if (mkdir(CGROUP_MOUNT_PATH, 0777) && errno != EEXIST) {
log_err("mkdir mount");
return 1;
}
if (unshare(CLONE_NEWNS)) {
log_err("unshare");
return 1;
}
if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
log_err("mount fakeroot");
return 1;
}
if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL) && errno != EBUSY) {
log_err("mount cgroup2");
return 1;
}
cgroup_workdir_mounted = true;
/* Cleanup existing failed runs, now that the environment is setup */
__cleanup_cgroup_environment();
if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
log_err("mkdir cgroup work dir");
return 1;
}
/* Enable all available controllers to increase test coverage */
if (__enable_controllers(CGROUP_MOUNT_PATH, NULL) ||
__enable_controllers(cgroup_workdir, NULL))
return 1;
return 0;
}
static int nftwfunc(const char *filename, const struct stat *statptr,
int fileflags, struct FTW *pfwt)
{
if ((fileflags & FTW_D) && rmdir(filename))
log_err("Removing cgroup: %s", filename);
return 0;
}
static int join_cgroup_from_top(const char *cgroup_path)
{
char cgroup_procs_path[PATH_MAX + 1];
pid_t pid = getpid();
int fd, rc = 0;
snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
"%s/cgroup.procs", cgroup_path);
fd = open(cgroup_procs_path, O_WRONLY);
if (fd < 0) {
log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
return 1;
}
if (dprintf(fd, "%d\n", pid) < 0) {
log_err("Joining Cgroup");
rc = 1;
}
close(fd);
return rc;
}
/**
* join_cgroup() - Join a cgroup
* @relative_path: The cgroup path, relative to the workdir, to join
*
* This function expects a cgroup to already be created, relative to the cgroup
* work dir, and it joins it. For example, passing "/my-cgroup" as the path
* would actually put the calling process into the cgroup
* "/cgroup-test-work-dir/my-cgroup"
*
* On success, it returns 0, otherwise on failure it returns 1.
*/
int join_cgroup(const char *relative_path)
{
char cgroup_path[PATH_MAX + 1];
format_cgroup_path(cgroup_path, relative_path);
return join_cgroup_from_top(cgroup_path);
}
/**
* join_root_cgroup() - Join the root cgroup
*
* This function joins the root cgroup.
*
* On success, it returns 0, otherwise on failure it returns 1.
*/
int join_root_cgroup(void)
{
return join_cgroup_from_top(CGROUP_MOUNT_PATH);
}
/**
* join_parent_cgroup() - Join a cgroup in the parent process workdir
* @relative_path: The cgroup path, relative to parent process workdir, to join
*
* See join_cgroup().
*
* On success, it returns 0, otherwise on failure it returns 1.
*/
int join_parent_cgroup(const char *relative_path)
{
char cgroup_path[PATH_MAX + 1];
format_parent_cgroup_path(cgroup_path, relative_path);
return join_cgroup_from_top(cgroup_path);
}
/**
* __cleanup_cgroup_environment() - Delete temporary cgroups
*
* This is a helper for cleanup_cgroup_environment() that is responsible for
* deletion of all temporary cgroups that have been created during the test.
*/
static void __cleanup_cgroup_environment(void)
{
char cgroup_workdir[PATH_MAX + 1];
format_cgroup_path(cgroup_workdir, "");
join_cgroup_from_top(CGROUP_MOUNT_PATH);
nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
}
/**
* cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
*
* This is an idempotent function to delete all temporary cgroups that
* have been created during the test and unmount the cgroup testing work
* directory.
*
* At call time, it moves the calling process to the root cgroup, and then
* runs the deletion process. It is idempotent, and should not fail, unless
* a process is lingering.
*
* On failure, it will print an error to stderr, and try to continue.
*/
void cleanup_cgroup_environment(void)
{
__cleanup_cgroup_environment();
if (cgroup_workdir_mounted && umount(CGROUP_MOUNT_PATH))
log_err("umount cgroup2");
cgroup_workdir_mounted = false;
}
/**
* get_root_cgroup() - Get the FD of the root cgroup
*
* On success, it returns the file descriptor. On failure, it returns -1.
* If there is a failure, it prints the error to stderr.
*/
int get_root_cgroup(void)
{
int fd;
fd = open(CGROUP_MOUNT_PATH, O_RDONLY);
if (fd < 0) {
log_err("Opening root cgroup");
return -1;
}
return fd;
}
/*
* remove_cgroup() - Remove a cgroup
* @relative_path: The cgroup path, relative to the workdir, to remove
*
* This function expects a cgroup to already be created, relative to the cgroup
* work dir. It also expects the cgroup doesn't have any children or live
* processes and it removes the cgroup.
*
* On failure, it will print an error to stderr.
*/
void remove_cgroup(const char *relative_path)
{
char cgroup_path[PATH_MAX + 1];
format_cgroup_path(cgroup_path, relative_path);
if (rmdir(cgroup_path))
log_err("rmdiring cgroup %s .. %s", relative_path, cgroup_path);
}
/**
* create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
* @relative_path: The cgroup path, relative to the workdir, to join
*
* This function creates a cgroup under the top level workdir and returns the
* file descriptor. It is idempotent.
*
* On success, it returns the file descriptor. On failure it returns -1.
* If there is a failure, it prints the error to stderr.
*/
int create_and_get_cgroup(const char *relative_path)
{
char cgroup_path[PATH_MAX + 1];
int fd;
format_cgroup_path(cgroup_path, relative_path);
if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
log_err("mkdiring cgroup %s .. %s", relative_path, cgroup_path);
return -1;
}
fd = open(cgroup_path, O_RDONLY);
if (fd < 0) {
log_err("Opening Cgroup");
return -1;
}
return fd;
}
/**
* get_cgroup_id_from_path - Get cgroup id for a particular cgroup path
* @cgroup_workdir: The absolute cgroup path
*
* On success, it returns the cgroup id. On failure it returns 0,
* which is an invalid cgroup id.
* If there is a failure, it prints the error to stderr.
*/
static unsigned long long get_cgroup_id_from_path(const char *cgroup_workdir)
{
int dirfd, err, flags, mount_id, fhsize;
union {
unsigned long long cgid;
unsigned char raw_bytes[8];
} id;
struct file_handle *fhp, *fhp2;
unsigned long long ret = 0;
dirfd = AT_FDCWD;
flags = 0;
fhsize = sizeof(*fhp);
fhp = calloc(1, fhsize);
if (!fhp) {
log_err("calloc");
return 0;
}
err = name_to_handle_at(dirfd, cgroup_workdir, fhp, &mount_id, flags);
if (err >= 0 || fhp->handle_bytes != 8) {
log_err("name_to_handle_at");
goto free_mem;
}
fhsize = sizeof(struct file_handle) + fhp->handle_bytes;
fhp2 = realloc(fhp, fhsize);
if (!fhp2) {
log_err("realloc");
goto free_mem;
}
err = name_to_handle_at(dirfd, cgroup_workdir, fhp2, &mount_id, flags);
fhp = fhp2;
if (err < 0) {
log_err("name_to_handle_at");
goto free_mem;
}
memcpy(id.raw_bytes, fhp->f_handle, 8);
ret = id.cgid;
free_mem:
free(fhp);
return ret;
}
unsigned long long get_cgroup_id(const char *relative_path)
{
char cgroup_workdir[PATH_MAX + 1];
format_cgroup_path(cgroup_workdir, relative_path);
return get_cgroup_id_from_path(cgroup_workdir);
}
int cgroup_setup_and_join(const char *path) {
int cg_fd;
if (setup_cgroup_environment()) {
fprintf(stderr, "Failed to setup cgroup environment\n");
return -EINVAL;
}
cg_fd = create_and_get_cgroup(path);
if (cg_fd < 0) {
fprintf(stderr, "Failed to create test cgroup\n");
cleanup_cgroup_environment();
return cg_fd;
}
if (join_cgroup(path)) {
fprintf(stderr, "Failed to join cgroup\n");
cleanup_cgroup_environment();
return -EINVAL;
}
return cg_fd;
}
/**
* setup_classid_environment() - Setup the cgroupv1 net_cls environment
*
* This function should only be called in a custom mount namespace, e.g.
* created by running setup_cgroup_environment.
*
* After calling this function, cleanup_classid_environment should be called
* once testing is complete.
*
* This function will print an error to stderr and return 1 if it is unable
* to setup the cgroup environment. If setup is successful, 0 is returned.
*/
int setup_classid_environment(void)
{
char cgroup_workdir[PATH_MAX + 1];
format_classid_path(cgroup_workdir);
if (mount("tmpfs", CGROUP_MOUNT_DFLT, "tmpfs", 0, NULL) &&
errno != EBUSY) {
log_err("mount cgroup base");
return 1;
}
if (mkdir(NETCLS_MOUNT_PATH, 0777) && errno != EEXIST) {
log_err("mkdir cgroup net_cls");
return 1;
}
if (mount("net_cls", NETCLS_MOUNT_PATH, "cgroup", 0, "net_cls")) {
if (errno != EBUSY) {
log_err("mount cgroup net_cls");
return 1;
}
if (rmdir(NETCLS_MOUNT_PATH)) {
log_err("rmdir cgroup net_cls");
return 1;
}
if (umount(CGROUP_MOUNT_DFLT)) {
log_err("umount cgroup base");
return 1;
}
}
cleanup_classid_environment();
if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
log_err("mkdir cgroup work dir");
return 1;
}
return 0;
}
/**
* set_classid() - Set a cgroupv1 net_cls classid
*
* Writes the classid into the cgroup work dir's net_cls.classid
* file in order to later on trigger socket tagging.
*
* We leverage the current pid as the classid, ensuring unique identification.
*
* On success, it returns 0, otherwise on failure it returns 1. If there
* is a failure, it prints the error to stderr.
*/
int set_classid(void)
{
char cgroup_workdir[PATH_MAX - 42];
char cgroup_classid_path[PATH_MAX + 1];
int fd, rc = 0;
format_classid_path(cgroup_workdir);
snprintf(cgroup_classid_path, sizeof(cgroup_classid_path),
"%s/net_cls.classid", cgroup_workdir);
fd = open(cgroup_classid_path, O_WRONLY);
if (fd < 0) {
log_err("Opening cgroup classid: %s", cgroup_classid_path);
return 1;
}
if (dprintf(fd, "%u\n", getpid()) < 0) {
log_err("Setting cgroup classid");
rc = 1;
}
close(fd);
return rc;
}
/**
* join_classid() - Join a cgroupv1 net_cls classid
*
* This function expects the cgroup work dir to be already created, as we
* join it here. This causes the process sockets to be tagged with the given
* net_cls classid.
*
* On success, it returns 0, otherwise on failure it returns 1.
*/
int join_classid(void)
{
char cgroup_workdir[PATH_MAX + 1];
format_classid_path(cgroup_workdir);
return join_cgroup_from_top(cgroup_workdir);
}
/**
* cleanup_classid_environment() - Cleanup the cgroupv1 net_cls environment
*
* At call time, it moves the calling process to the root cgroup, and then
* runs the deletion process.
*
* On failure, it will print an error to stderr, and try to continue.
*/
void cleanup_classid_environment(void)
{
char cgroup_workdir[PATH_MAX + 1];
format_classid_path(cgroup_workdir);
join_cgroup_from_top(NETCLS_MOUNT_PATH);
nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
}
/**
* get_classid_cgroup_id - Get the cgroup id of a net_cls cgroup
*/
unsigned long long get_classid_cgroup_id(void)
{
char cgroup_workdir[PATH_MAX + 1];
format_classid_path(cgroup_workdir);
return get_cgroup_id_from_path(cgroup_workdir);
}
/**
* get_cgroup1_hierarchy_id - Retrieves the ID of a cgroup1 hierarchy from the cgroup1 subsys name.
* @subsys_name: The cgroup1 subsys name, which can be retrieved from /proc/self/cgroup. It can be
* a named cgroup like "name=systemd", a controller name like "net_cls", or multi-controllers like
* "net_cls,net_prio".
*/
int get_cgroup1_hierarchy_id(const char *subsys_name)
{
char *c, *c2, *c3, *c4;
bool found = false;
char line[1024];
FILE *file;
int i, id;
if (!subsys_name)
return -1;
file = fopen("/proc/self/cgroup", "r");
if (!file) {
log_err("fopen /proc/self/cgroup");
return -1;
}
while (fgets(line, 1024, file)) {
i = 0;
for (c = strtok_r(line, ":", &c2); c && i < 2; c = strtok_r(NULL, ":", &c2)) {
if (i == 0) {
id = strtol(c, NULL, 10);
} else if (i == 1) {
if (!strcmp(c, subsys_name)) {
found = true;
break;
}
/* Multiple subsystems may share one single mount point */
for (c3 = strtok_r(c, ",", &c4); c3;
c3 = strtok_r(NULL, ",", &c4)) {
if (!strcmp(c, subsys_name)) {
found = true;
break;
}
}
}
i++;
}
if (found)
break;
}
fclose(file);
return found ? id : -1;
}
/**
* open_classid() - Open a cgroupv1 net_cls classid
*
* This function expects the cgroup work dir to be already created, as we
* open it here.
*
* On success, it returns the file descriptor. On failure it returns -1.
*/
int open_classid(void)
{
char cgroup_workdir[PATH_MAX + 1];
format_classid_path(cgroup_workdir);
return open(cgroup_workdir, O_RDONLY);
}
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