Repository navigation
Expand file tree
/
Copy pathmnexec.c
More file actions
198 lines (187 loc) · 5.23 KB
/
Copy pathmnexec.c
File metadata and controls
198 lines (187 loc) · 5.23 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
/* mnexec: execution utility for mininet
*
* Starts up programs and does things that are slow or
* difficult in Python, including:
*
* - closing all file descriptors except stdin/out/error
* - detaching from a controlling tty using setsid
* - running in network and mount namespaces
* - printing out the pid of a process so we can identify it later
* - attaching to a namespace and cgroup
* - setting RT scheduling
*
* Partially based on public domain setsid(1)
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <linux/sched.h>
#include <unistd.h>
#include <limits.h>
#include <syscall.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sched.h>
#include <ctype.h>
#include <sys/mount.h>
#if !defined(VERSION)
#define VERSION "(devel)"
#endif
void usage(char *name)
{
printf("Execution utility for Mininet\n\n"
"Usage: %s [-cdnp] [-a pid] [-g group] [-r rtprio] cmd args...\n\n"
"Options:\n"
" -c: close all file descriptors except stdin/out/error\n"
" -d: detach from tty by calling setsid()\n"
" -n: run in new network and mount namespaces\n"
" -p: print ^A + pid\n"
" -a pid: attach to pid's network and mount namespaces\n"
" -g group: add to cgroup\n"
" -r rtprio: run with SCHED_RR (usually requires -g)\n"
" -v: print version\n",
name);
}
int setns(int fd, int nstype)
{
return syscall(__NR_setns, fd, nstype);
}
/* Validate alphanumeric path foo1/bar2/baz */
void validate(char *path)
{
char *s;
for (s=path; *s; s++) {
if (!isalnum(*s) && *s != '/') {
fprintf(stderr, "invalid path: %s\n", path);
exit(1);
}
}
}
/* Add our pid to cgroup */
void cgroup(char *gname)
{
static char path[PATH_MAX];
static char *groups[] = {
"cpu", "cpuacct", "cpuset", NULL
};
char **gptr;
pid_t pid = getpid();
int count = 0;
validate(gname);
for (gptr = groups; *gptr; gptr++) {
FILE *f;
snprintf(path, PATH_MAX, "/sys/fs/cgroup/%s/%s/tasks",
*gptr, gname);
f = fopen(path, "w");
if (f) {
count++;
fprintf(f, "%d\n", pid);
fclose(f);
}
}
if (!count) {
fprintf(stderr, "cgroup: could not add to cgroup %s\n",
gname);
exit(1);
}
}
int main(int argc, char *argv[])
{
int c;
int fd;
char path[PATH_MAX];
int nsid;
int pid;
static struct sched_param sp;
while ((c = getopt(argc, argv, "+cdnpa:g:r:vh")) != -1)
switch(c) {
case 'c':
/* close file descriptors except stdin/out/error */
for (fd = getdtablesize(); fd > 2; fd--)
close(fd);
break;
case 'd':
/* detach from tty */
if (getpgrp() == getpid()) {
switch(fork()) {
case -1:
perror("fork");
return 1;
case 0: /* child */
break;
default: /* parent */
return 0;
}
}
setsid();
break;
case 'n':
/* run in network and mount namespaces */
if (unshare(CLONE_NEWNET|CLONE_NEWNS) == -1) {
perror("unshare");
return 1;
}
/* mount sysfs to pick up the new network namespace */
if (mount("sysfs", "/sys", "sysfs", MS_MGC_VAL, NULL) == -1) {
perror("mount");
return 1;
}
break;
case 'p':
/* print pid */
printf("\001%d\n", getpid());
fflush(stdout);
break;
case 'a':
/* Attach to pid's network namespace and mount namespace*/
pid = atoi(optarg);
sprintf(path, "/proc/%d/ns/net", pid );
nsid = open(path, O_RDONLY);
if (nsid < 0) {
perror(path);
return 1;
}
if (setns(nsid, 0) != 0) {
perror("setns");
return 1;
}
sprintf(path, "/proc/%d/ns/mnt", pid );
nsid = open(path, O_RDONLY);
if (nsid < 0) {
perror(path);
return 1;
}
if (setns(nsid, 0) != 0) {
perror("setns");
return 1;
}
break;
case 'g':
/* Attach to cgroup */
cgroup(optarg);
break;
case 'r':
/* Set RT scheduling priority */
sp.sched_priority = atoi(optarg);
if (sched_setscheduler(getpid(), SCHED_RR, &sp) < 0) {
perror("sched_setscheduler");
return 1;
}
break;
case 'v':
printf("%s\n", VERSION);
exit(0);
case 'h':
usage(argv[0]);
exit(0);
default:
usage(argv[0]);
exit(1);
}
if (optind < argc) {
execvp(argv[optind], &argv[optind]);
perror(argv[optind]);
return 1;
}
usage(argv[0]);
return 0;
}