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Copy pathmnexec.c
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79 lines (73 loc) · 2.05 KB
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/* 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 a network namespace
* - printing out the pid of a process so we can identify it later
*
* Partially based on public domain setsid(1)
*/
#include <stdio.h>
#include <linux/sched.h>
#include <unistd.h>
void usage(char *name)
{
printf("Execution utility for Mininet.\n"
"usage: %s [-cdnp]\n"
"-c: close all file descriptors except stdin/out/error\n"
"-d: detach from tty by calling setsid()\n"
"-n: run in new network namespace\n"
"-p: print ^A + pid\n", name);
}
int main(int argc, char *argv[])
{
char c;
int fd;
while ((c = getopt(argc, argv, "+cdnp")) != -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 namespace */
if (unshare(CLONE_NEWNET) == -1) {
perror("unshare");
return 1;
}
break;
case 'p':
/* print pid */
printf("\001%d\n", getpid());
fflush(stdout);
break;
default:
usage(argv[0]);
break;
}
if (optind < argc) {
execvp(argv[optind], &argv[optind]);
perror(argv[optind]);
return 1;
}
usage(argv[0]);
}