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lxcfs.c
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/* lxcfs
*
* Copyright © 2014,2015 Canonical, Inc
* Author: Serge Hallyn <serge.hallyn@ubuntu.com>
*
* See COPYING file for details.
*/
/*
* TODO XXX
* sanitize paths for '..', cgmanager's not doing that for us any more
* does fuse help us?
* Surely there are more paths we'll need to sanitize - look back through
* cgmanager's sources.
*/
#define FUSE_USE_VERSION 26
#include <stdio.h>
#include <dirent.h>
#include <fcntl.h>
#include <fuse.h>
#include <unistd.h>
#include <errno.h>
#include <stdbool.h>
#include <time.h>
#include <string.h>
#include <stdlib.h>
#include <libgen.h>
#include <sched.h>
#include <linux/sched.h>
#include <sys/socket.h>
#include <sys/mount.h>
#include <wait.h>
#ifdef FORTRAVIS
#define GLIB_DISABLE_DEPRECATION_WARNINGS
#include <glib-object.h>
#endif
#include "cgfs.h"
#include "config.h" // for VERSION
enum {
LXC_TYPE_CGDIR,
LXC_TYPE_CGFILE,
LXC_TYPE_PROC_MEMINFO,
LXC_TYPE_PROC_CPUINFO,
LXC_TYPE_PROC_UPTIME,
LXC_TYPE_PROC_STAT,
LXC_TYPE_PROC_DISKSTATS,
};
struct file_info {
char *controller;
char *cgroup;
char *file;
int type;
char *buf; // unused as of yet
int buflen;
int size; //actual data size
int cached;
};
/* reserve buffer size, for cpuall in /proc/stat */
#define BUF_RESERVE_SIZE 256
/*
* append pid to *src.
* src: a pointer to a char* in which ot append the pid.
* sz: the number of characters printed so far, minus trailing \0.
* asz: the allocated size so far
* pid: the pid to append
*/
static void must_strcat_pid(char **src, size_t *sz, size_t *asz, pid_t pid)
{
char *d = *src;
char tmp[30];
sprintf(tmp, "%d\n", (int)pid);
if (!d) {
do {
d = malloc(BUF_RESERVE_SIZE);
} while (!d);
*src = d;
*asz = BUF_RESERVE_SIZE;
} else if (strlen(tmp) + sz + 1 >= asz) {
do {
d = realloc(d, *asz + BUF_RESERVE_SIZE);
} while (!d);
*src = d;
*asz += BUF_RESERVE_SIZE;
}
memcpy(d+*sz, tmp, strlen(tmp));
*sz += strlen(tmp);
d[*sz] = '\0';
}
static int wait_for_pid(pid_t pid)
{
int status, ret;
again:
ret = waitpid(pid, &status, 0);
if (ret == -1) {
if (errno == EINTR)
goto again;
return -1;
}
if (ret != pid)
goto again;
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
return -1;
return 0;
}
/*
* Given a open file * to /proc/pid/{u,g}id_map, and an id
* valid in the caller's namespace, return the id mapped into
* pid's namespace.
* Returns the mapped id, or -1 on error.
*/
unsigned int
convert_id_to_ns(FILE *idfile, unsigned int in_id)
{
unsigned int nsuid, // base id for a range in the idfile's namespace
hostuid, // base id for a range in the caller's namespace
count; // number of ids in this range
char line[400];
int ret;
fseek(idfile, 0L, SEEK_SET);
while (fgets(line, 400, idfile)) {
ret = sscanf(line, "%u %u %u\n", &nsuid, &hostuid, &count);
if (ret != 3)
continue;
if (hostuid + count < hostuid || nsuid + count < nsuid) {
/*
* uids wrapped around - unexpected as this is a procfile,
* so just bail.
*/
fprintf(stderr, "pid wrapparound at entry %u %u %u in %s\n",
nsuid, hostuid, count, line);
return -1;
}
if (hostuid <= in_id && hostuid+count > in_id) {
/*
* now since hostuid <= in_id < hostuid+count, and
* hostuid+count and nsuid+count do not wrap around,
* we know that nsuid+(in_id-hostuid) which must be
* less that nsuid+(count) must not wrap around
*/
return (in_id - hostuid) + nsuid;
}
}
// no answer found
return -1;
}
/*
* for is_privileged_over,
* specify whether we require the calling uid to be root in his
* namespace
*/
#define NS_ROOT_REQD true
#define NS_ROOT_OPT false
#define PROCLEN 100
static bool is_privileged_over(pid_t pid, uid_t uid, uid_t victim, bool req_ns_root)
{
char fpath[PROCLEN];
int ret;
bool answer = false;
uid_t nsuid;
if (victim == -1 || uid == -1)
return false;
/*
* If the request is one not requiring root in the namespace,
* then having the same uid suffices. (i.e. uid 1000 has write
* access to files owned by uid 1000
*/
if (!req_ns_root && uid == victim)
return true;
ret = snprintf(fpath, PROCLEN, "/proc/%d/uid_map", pid);
if (ret < 0 || ret >= PROCLEN)
return false;
FILE *f = fopen(fpath, "r");
if (!f)
return false;
/* if caller's not root in his namespace, reject */
nsuid = convert_id_to_ns(f, uid);
if (nsuid)
goto out;
/*
* If victim is not mapped into caller's ns, reject.
* XXX I'm not sure this check is needed given that fuse
* will be sending requests where the vfs has converted
*/
nsuid = convert_id_to_ns(f, victim);
if (nsuid == -1)
goto out;
answer = true;
out:
fclose(f);
return answer;
}
static bool perms_include(int fmode, mode_t req_mode)
{
mode_t r;
switch (req_mode & O_ACCMODE) {
case O_RDONLY:
r = S_IROTH;
break;
case O_WRONLY:
r = S_IWOTH;
break;
case O_RDWR:
r = S_IROTH | S_IWOTH;
break;
default:
return false;
}
return ((fmode & r) == r);
}
static char *get_next_cgroup_dir(const char *taskcg, const char *querycg)
{
char *start, *end;
if (strlen(taskcg) <= strlen(querycg)) {
fprintf(stderr, "%s: I was fed bad input\n", __func__);
return NULL;
}
if (strcmp(querycg, "/") == 0)
start = strdup(taskcg + 1);
else
start = strdup(taskcg + strlen(querycg) + 1);
if (!start)
return NULL;
end = strchr(start, '/');
if (end)
*end = '\0';
return start;
}
static void stripnewline(char *x)
{
size_t l = strlen(x);
if (l && x[l-1] == '\n')
x[l-1] = '\0';
}
static char *get_pid_cgroup(pid_t pid, const char *contrl)
{
char fnam[PROCLEN];
FILE *f;
char *answer = NULL;
char *line = NULL;
size_t len = 0;
int ret;
const char *h = find_mounted_controller(contrl);
if (!h)
return NULL;
ret = snprintf(fnam, PROCLEN, "/proc/%d/cgroup", pid);
if (ret < 0 || ret >= PROCLEN)
return NULL;
if (!(f = fopen(fnam, "r")))
return NULL;
while (getline(&line, &len, f) != -1) {
char *c1, *c2;
if (!line[0])
continue;
c1 = strchr(line, ':');
if (!c1)
goto out;
c1++;
c2 = strchr(c1, ':');
if (!c2)
goto out;
*c2 = '\0';
if (strcmp(c1, h) != 0)
continue;
c2++;
stripnewline(c2);
do {
answer = strdup(c2);
} while (!answer);
break;
}
out:
fclose(f);
free(line);
return answer;
}
/*
* check whether a fuse context may access a cgroup dir or file
*
* If file is not null, it is a cgroup file to check under cg.
* If file is null, then we are checking perms on cg itself.
*
* For files we can check the mode of the list_keys result.
* For cgroups, we must make assumptions based on the files under the
* cgroup, because cgmanager doesn't tell us ownership/perms of cgroups
* yet.
*/
static bool fc_may_access(struct fuse_context *fc, const char *contrl, const char *cg, const char *file, mode_t mode)
{
struct cgfs_files *k = NULL;
bool ret = false;
if (!file)
file = "tasks";
if (*file == '/')
file++;
k = cgfs_get_key(contrl, cg, file);
if (!k)
return false;
if (is_privileged_over(fc->pid, fc->uid, k->uid, NS_ROOT_OPT)) {
if (perms_include(k->mode >> 6, mode)) {
ret = true;
goto out;
}
}
if (fc->gid == k->gid) {
if (perms_include(k->mode >> 3, mode)) {
ret = true;
goto out;
}
}
ret = perms_include(k->mode, mode);
out:
free_key(k);
return ret;
}
#define INITSCOPE "/init.scope"
static void prune_init_slice(char *cg)
{
char *point;
point = cg + strlen(cg) - strlen(INITSCOPE);
if (point < cg)
return;
if (strcmp(point, INITSCOPE) == 0) {
if (point == cg)
*(point+1) = '\0';
else
*point = '\0';
}
}
/*
* If caller is in /a/b/c/d, he may only act on things under cg=/a/b/c/d.
* If caller is in /a, he may act on /a/b, but not on /b.
* if the answer is false and nextcg is not NULL, then *nextcg will point
* to a string containing the next cgroup directory under cg, which must be
* freed by the caller.
*/
static bool caller_is_in_ancestor(pid_t pid, const char *contrl, const char *cg, char **nextcg)
{
char fnam[PROCLEN];
FILE *f;
bool answer = false;
char *line = NULL;
size_t len = 0;
int ret;
ret = snprintf(fnam, PROCLEN, "/proc/%d/cgroup", pid);
if (ret < 0 || ret >= PROCLEN)
return false;
if (!(f = fopen(fnam, "r")))
return false;
while (getline(&line, &len, f) != -1) {
char *c1, *c2, *linecmp;
if (!line[0])
continue;
c1 = strchr(line, ':');
if (!c1)
goto out;
c1++;
c2 = strchr(c1, ':');
if (!c2)
goto out;
*c2 = '\0';
if (strcmp(c1, contrl) != 0)
continue;
c2++;
stripnewline(c2);
prune_init_slice(c2);
/*
* callers pass in '/' for root cgroup, otherwise they pass
* in a cgroup without leading '/'
*/
linecmp = *cg == '/' ? c2 : c2+1;
if (strncmp(linecmp, cg, strlen(linecmp)) != 0) {
if (nextcg)
*nextcg = get_next_cgroup_dir(linecmp, cg);
goto out;
}
answer = true;
goto out;
}
out:
fclose(f);
free(line);
return answer;
}
/*
* given /cgroup/freezer/a/b, return "freezer".
* the returned char* should NOT be freed.
*/
static char *pick_controller_from_path(struct fuse_context *fc, const char *path)
{
const char *p1;
char *contr, *slash;
if (strlen(path) < 9)
return NULL;
if (*(path+7) != '/')
return NULL;
p1 = path+8;
contr = strdupa(p1);
if (!contr)
return NULL;
slash = strstr(contr, "/");
if (slash)
*slash = '\0';
int i;
for (i = 0; i < num_hierarchies; i++) {
if (hierarchies[i] && strcmp(hierarchies[i], contr) == 0)
return hierarchies[i];
}
return NULL;
}
/*
* Find the start of cgroup in /cgroup/controller/the/cgroup/path
* Note that the returned value may include files (keynames) etc
*/
static const char *find_cgroup_in_path(const char *path)
{
const char *p1;
if (strlen(path) < 9)
return NULL;
p1 = strstr(path+8, "/");
if (!p1)
return NULL;
return p1+1;
}
/*
* dir should be freed, file not
*/
static void get_cgdir_and_path(const char *cg, char **dir, char **file)
{
char *p;
do {
*dir = strdup(cg);
} while (!*dir);
*file = strrchr(cg, '/');
if (!*file) {
*file = NULL;
return;
}
p = strrchr(*dir, '/');
*p = '\0';
}
/*
* FUSE ops for /cgroup
*/
static int cg_getattr(const char *path, struct stat *sb)
{
struct timespec now;
struct fuse_context *fc = fuse_get_context();
char * cgdir = NULL;
char *fpath = NULL, *path1, *path2;
struct cgfs_files *k = NULL;
const char *cgroup;
const char *controller = NULL;
int ret = -ENOENT;
if (!fc)
return -EIO;
memset(sb, 0, sizeof(struct stat));
if (clock_gettime(CLOCK_REALTIME, &now) < 0)
return -EINVAL;
sb->st_uid = sb->st_gid = 0;
sb->st_atim = sb->st_mtim = sb->st_ctim = now;
sb->st_size = 0;
if (strcmp(path, "/cgroup") == 0) {
sb->st_mode = S_IFDIR | 00755;
sb->st_nlink = 2;
return 0;
}
controller = pick_controller_from_path(fc, path);
if (!controller)
return -EIO;
cgroup = find_cgroup_in_path(path);
if (!cgroup) {
/* this is just /cgroup/controller, return it as a dir */
sb->st_mode = S_IFDIR | 00755;
sb->st_nlink = 2;
return 0;
}
get_cgdir_and_path(cgroup, &cgdir, &fpath);
if (!fpath) {
path1 = "/";
path2 = cgdir;
} else {
path1 = cgdir;
path2 = fpath;
}
/* check that cgcopy is either a child cgroup of cgdir, or listed in its keys.
* Then check that caller's cgroup is under path if fpath is a child
* cgroup, or cgdir if fpath is a file */
if (is_child_cgroup(controller, path1, path2)) {
if (!caller_is_in_ancestor(fc->pid, controller, cgroup, NULL)) {
/* this is just /cgroup/controller, return it as a dir */
sb->st_mode = S_IFDIR | 00555;
sb->st_nlink = 2;
ret = 0;
goto out;
}
if (!fc_may_access(fc, controller, cgroup, NULL, O_RDONLY)) {
ret = -EACCES;
goto out;
}
// get uid, gid, from '/tasks' file and make up a mode
// That is a hack, until cgmanager gains a GetCgroupPerms fn.
sb->st_mode = S_IFDIR | 00755;
k = cgfs_get_key(controller, cgroup, "tasks");
if (!k) {
sb->st_uid = sb->st_gid = 0;
} else {
sb->st_uid = k->uid;
sb->st_gid = k->gid;
}
free_key(k);
sb->st_nlink = 2;
ret = 0;
goto out;
}
if ((k = cgfs_get_key(controller, path1, path2)) != NULL) {
sb->st_mode = S_IFREG | k->mode;
sb->st_nlink = 1;
sb->st_uid = k->uid;
sb->st_gid = k->gid;
sb->st_size = 0;
free_key(k);
if (!caller_is_in_ancestor(fc->pid, controller, path1, NULL)) {
ret = -ENOENT;
goto out;
}
if (!fc_may_access(fc, controller, path1, path2, O_RDONLY)) {
ret = -EACCES;
goto out;
}
ret = 0;
}
out:
free(cgdir);
return ret;
}
static int cg_opendir(const char *path, struct fuse_file_info *fi)
{
struct fuse_context *fc = fuse_get_context();
const char *cgroup;
struct file_info *dir_info;
char *controller = NULL;
if (!fc)
return -EIO;
if (strcmp(path, "/cgroup") == 0) {
cgroup = NULL;
controller = NULL;
} else {
// return list of keys for the controller, and list of child cgroups
controller = pick_controller_from_path(fc, path);
if (!controller)
return -EIO;
cgroup = find_cgroup_in_path(path);
if (!cgroup) {
/* this is just /cgroup/controller, return its contents */
cgroup = "/";
}
}
if (cgroup && !fc_may_access(fc, controller, cgroup, NULL, O_RDONLY)) {
return -EACCES;
}
/* we'll free this at cg_releasedir */
dir_info = malloc(sizeof(*dir_info));
if (!dir_info)
return -ENOMEM;
dir_info->controller = must_copy_string(controller);
dir_info->cgroup = must_copy_string(cgroup);
dir_info->type = LXC_TYPE_CGDIR;
dir_info->buf = NULL;
dir_info->file = NULL;
dir_info->buflen = 0;
fi->fh = (unsigned long)dir_info;
return 0;
}
static int cg_readdir(const char *path, void *buf, fuse_fill_dir_t filler, off_t offset,
struct fuse_file_info *fi)
{
struct file_info *d = (struct file_info *)fi->fh;
struct cgfs_files **list = NULL;
int i, ret;
char *nextcg = NULL;
struct fuse_context *fc = fuse_get_context();
char **clist = NULL;
if (d->type != LXC_TYPE_CGDIR) {
fprintf(stderr, "Internal error: file cache info used in readdir\n");
return -EIO;
}
if (!d->cgroup && !d->controller) {
// ls /var/lib/lxcfs/cgroup - just show list of controllers
int i;
for (i = 0; i < num_hierarchies; i++) {
if (hierarchies[i] && filler(buf, hierarchies[i], NULL, 0) != 0) {
return -EIO;
}
}
return 0;
}
if (!cgfs_list_keys(d->controller, d->cgroup, &list)) {
// not a valid cgroup
ret = -EINVAL;
goto out;
}
if (!caller_is_in_ancestor(fc->pid, d->controller, d->cgroup, &nextcg)) {
if (nextcg) {
int ret;
ret = filler(buf, nextcg, NULL, 0);
free(nextcg);
if (ret != 0) {
ret = -EIO;
goto out;
}
}
ret = 0;
goto out;
}
for (i = 0; list[i]; i++) {
if (filler(buf, list[i]->name, NULL, 0) != 0) {
ret = -EIO;
goto out;
}
}
// now get the list of child cgroups
if (!cgfs_list_children(d->controller, d->cgroup, &clist)) {
ret = 0;
goto out;
}
for (i = 0; clist[i]; i++) {
if (filler(buf, clist[i], NULL, 0) != 0) {
ret = -EIO;
goto out;
}
}
ret = 0;
out:
free_keys(list);
if (clist) {
for (i = 0; clist[i]; i++)
free(clist[i]);
free(clist);
}
return ret;
}
static void do_release_file_info(struct file_info *f)
{
if (!f)
return;
free(f->controller);
free(f->cgroup);
free(f->file);
free(f->buf);
free(f);
}
static int cg_releasedir(const char *path, struct fuse_file_info *fi)
{
struct file_info *d = (struct file_info *)fi->fh;
do_release_file_info(d);
return 0;
}
static int cg_open(const char *path, struct fuse_file_info *fi)
{
const char *cgroup;
char *fpath = NULL, *path1, *path2, * cgdir = NULL, *controller;
struct cgfs_files *k = NULL;
struct file_info *file_info;
struct fuse_context *fc = fuse_get_context();
int ret;
if (!fc)
return -EIO;
controller = pick_controller_from_path(fc, path);
if (!controller)
return -EIO;
cgroup = find_cgroup_in_path(path);
if (!cgroup)
return -EINVAL;
get_cgdir_and_path(cgroup, &cgdir, &fpath);
if (!fpath) {
path1 = "/";
path2 = cgdir;
} else {
path1 = cgdir;
path2 = fpath;
}
k = cgfs_get_key(controller, path1, path2);
if (!k) {
ret = -EINVAL;
goto out;
}
free_key(k);
if (!fc_may_access(fc, controller, path1, path2, fi->flags)) {
// should never get here
ret = -EACCES;
goto out;
}
/* we'll free this at cg_release */
file_info = malloc(sizeof(*file_info));
if (!file_info) {
ret = -ENOMEM;
goto out;
}
file_info->controller = must_copy_string(controller);
file_info->cgroup = must_copy_string(path1);
file_info->file = must_copy_string(path2);
file_info->type = LXC_TYPE_CGFILE;
file_info->buf = NULL;
file_info->buflen = 0;
fi->fh = (unsigned long)file_info;
ret = 0;
out:
free(cgdir);
return ret;
}
static int cg_release(const char *path, struct fuse_file_info *fi)
{
struct file_info *f = (struct file_info *)fi->fh;
do_release_file_info(f);
return 0;
}
static int msgrecv(int sockfd, void *buf, size_t len)
{
struct timeval tv;
fd_set rfds;
FD_ZERO(&rfds);
FD_SET(sockfd, &rfds);
tv.tv_sec = 2;
tv.tv_usec = 0;
if (select(sockfd+1, &rfds, NULL, NULL, &tv) <= 0)
return -1;
return recv(sockfd, buf, len, MSG_DONTWAIT);
}
#define SEND_CREDS_OK 0
#define SEND_CREDS_NOTSK 1
#define SEND_CREDS_FAIL 2
static int send_creds(int sock, struct ucred *cred, char v, bool pingfirst)
{
struct msghdr msg = { 0 };
struct iovec iov;
struct cmsghdr *cmsg;
char cmsgbuf[CMSG_SPACE(sizeof(*cred))];
char buf[1];
buf[0] = 'p';
if (pingfirst) {
if (msgrecv(sock, buf, 1) != 1) {
fprintf(stderr, "%s: Error getting reply from server over socketpair\n",
__func__);
return SEND_CREDS_FAIL;
}
}
msg.msg_control = cmsgbuf;
msg.msg_controllen = sizeof(cmsgbuf);
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_CREDENTIALS;
memcpy(CMSG_DATA(cmsg), cred, sizeof(*cred));
msg.msg_name = NULL;
msg.msg_namelen = 0;
buf[0] = v;
iov.iov_base = buf;
iov.iov_len = sizeof(buf);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
if (sendmsg(sock, &msg, 0) < 0) {
fprintf(stderr, "%s: failed at sendmsg: %s\n", __func__,
strerror(errno));
if (errno == 3)
return SEND_CREDS_NOTSK;
return SEND_CREDS_FAIL;
}
return SEND_CREDS_OK;
}
static bool recv_creds(int sock, struct ucred *cred, char *v)
{
struct msghdr msg = { 0 };
struct iovec iov;
struct cmsghdr *cmsg;
char cmsgbuf[CMSG_SPACE(sizeof(*cred))];
char buf[1];
int ret;
int optval = 1;
struct timeval tv;
fd_set rfds;
*v = '1';
cred->pid = -1;
cred->uid = -1;
cred->gid = -1;
if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &optval, sizeof(optval)) == -1) {
fprintf(stderr, "Failed to set passcred: %s\n", strerror(errno));
return false;
}
buf[0] = '1';
if (write(sock, buf, 1) != 1) {
fprintf(stderr, "Failed to start write on scm fd: %s\n", strerror(errno));
return false;
}
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_control = cmsgbuf;
msg.msg_controllen = sizeof(cmsgbuf);
iov.iov_base = buf;
iov.iov_len = sizeof(buf);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
FD_ZERO(&rfds);
FD_SET(sock, &rfds);
tv.tv_sec = 2;
tv.tv_usec = 0;
if (select(sock+1, &rfds, NULL, NULL, &tv) <= 0) {
fprintf(stderr, "Failed to select for scm_cred: %s\n",
strerror(errno));
return false;
}
ret = recvmsg(sock, &msg, MSG_DONTWAIT);
if (ret < 0) {
fprintf(stderr, "Failed to receive scm_cred: %s\n",
strerror(errno));
return false;
}
cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg && cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred)) &&
cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_CREDENTIALS) {
memcpy(cred, CMSG_DATA(cmsg), sizeof(*cred));
}
*v = buf[0];
return true;
}
/*
* pid_to_ns - reads pids from a ucred over a socket, then writes the
* int value back over the socket. This shifts the pid from the
* sender's pidns into tpid's pidns.
*/
static void pid_to_ns(int sock, pid_t tpid)
{
char v = '0';
struct ucred cred;
while (recv_creds(sock, &cred, &v)) {
if (v == '1')
_exit(0);
if (write(sock, &cred.pid, sizeof(pid_t)) != sizeof(pid_t))
_exit(1);
}
_exit(0);
}
/*
* pid_to_ns_wrapper: when you setns into a pidns, you yourself remain
* in your old pidns. Only children which you fork will be in the target
* pidns. So the pid_to_ns_wrapper does the setns, then forks a child to
* actually convert pids
*/
static void pid_to_ns_wrapper(int sock, pid_t tpid)
{
int newnsfd = -1, ret, cpipe[2];
char fnam[100];
pid_t cpid;
struct timeval tv;
fd_set s;
char v;
ret = snprintf(fnam, sizeof(fnam), "/proc/%d/ns/pid", tpid);
if (ret < 0 || ret >= sizeof(fnam))
_exit(1);
newnsfd = open(fnam, O_RDONLY);
if (newnsfd < 0)
_exit(1);
if (setns(newnsfd, 0) < 0)
_exit(1);
close(newnsfd);
if (pipe(cpipe) < 0)
_exit(1);
loop:
cpid = fork();
if (cpid < 0)
_exit(1);