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// SPDX-License-Identifier: GPL-2.0-or-later
/* nstool - maintain a namespace to be entered by other processes
*
* Copyright Red Hat
* Author: David Gibson <david@gibson.dropbear.id.au>
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/un.h>
#define die(...) \
do { \
fprintf(stderr, __VA_ARGS__); \
exit(1); \
} while (0)
static void usage(void)
{
die("Usage:\n"
" nstool hold SOCK\n"
" Run within a set of namespaces, open a Unix domain socket\n"
" (the \"control socket\") at SOCK and wait for requests from\n"
" other nstool subcommands.\n"
" nstool pid SOCK\n"
" Print the pid of the nstool hold process with control socket\n"
" at SOCK, as seen in the caller's namespace.\n"
" nstool stop SOCK\n"
" Instruct the nstool hold with control socket at SOCK to\n"
" terminate.\n");
}
static int connect_ctl(const char * sockpath, bool wait)
{
int fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
struct sockaddr_un addr = {
.sun_family = AF_UNIX,
};
int rc;
if (fd < 0)
die("socket(): %s\n", strerror(errno));
strncpy(addr.sun_path, sockpath, UNIX_PATH_MAX);
do {
rc = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
if (rc < 0 &&
(!wait || (errno != ENOENT && errno != ECONNREFUSED)))
die("connect() to %s: %s\n", sockpath, strerror(errno));
} while (rc < 0);
return fd;
}
static void cmd_hold(int argc, char *argv[])
{
int fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
struct sockaddr_un addr = {
.sun_family = AF_UNIX,
};
const char *sockpath = argv[1];
int rc;
if (argc != 2)
usage();
if (fd < 0)
die("socket(): %s\n", strerror(errno));
strncpy(addr.sun_path, sockpath, UNIX_PATH_MAX);
rc = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
if (rc < 0)
die("bind() to %s: %s\n", sockpath, strerror(errno));
rc = listen(fd, 0);
if (rc < 0)
die("listen() on %s: %s\n", sockpath, strerror(errno));
printf("nstool hold: local PID=%d local UID=%u local GID=%u\n",
getpid(), getuid(), getgid());
do {
int afd = accept(fd, NULL, NULL);
char buf;
if (afd < 0)
die("accept(): %s\n", strerror(errno));
rc = read(afd, &buf, sizeof(buf));
if (rc < 0)
die("read(): %s\n", strerror(errno));
} while (rc == 0);
unlink(sockpath);
}
static void cmd_pid(int argc, char *argv[])
{
const char *sockpath = argv[1];
struct ucred peercred;
socklen_t optlen = sizeof(peercred);
int fd, rc;
if (argc != 2)
usage();
fd = connect_ctl(sockpath, true);
rc = getsockopt(fd, SOL_SOCKET, SO_PEERCRED,
&peercred, &optlen);
if (rc < 0)
die("getsockopet(SO_PEERCRED) %s: %s\n",
sockpath, strerror(errno));
close(fd);
printf("%d\n", peercred.pid);
}
static void cmd_stop(int argc, char *argv[])
{
const char *sockpath = argv[1];
int fd, rc;
char buf = 'Q';
if (argc != 2)
usage();
fd = connect_ctl(sockpath, false);
rc = write(fd, &buf, sizeof(buf));
if (rc < 0)
die("write() to %s: %s\n", sockpath, strerror(errno));
close(fd);
}
int main(int argc, char *argv[])
{
const char *subcmd = argv[1];
int fd;
if (argc < 2)
usage();
fd = socket(AF_UNIX, SOCK_STREAM, PF_UNIX);
if (fd < 0)
die("socket(): %s\n", strerror(errno));
if (strcmp(subcmd, "hold") == 0)
cmd_hold(argc - 1, argv + 1);
else if (strcmp(subcmd, "pid") == 0)
cmd_pid(argc - 1, argv + 1);
else if (strcmp(subcmd, "stop") == 0)
cmd_stop(argc - 1, argv + 1);
else
usage();
exit(0);
}
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