Bob Lantz
80 lines
2.1 KiB
C
80 lines
2.1 KiB
C
/* mnexec: execution utility for mininet
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*
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* Starts up programs and does things that are slow or
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* difficult in Python, including:
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*
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* - closing all file descriptors except stdin/out/error
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* - detaching from a controlling tty using setsid
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* - running in a network namespace
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* - printing out the pid of a process so we can identify it later
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*
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* Partially based on public domain setsid(1)
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*/
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#include <stdio.h>
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#include <linux/sched.h>
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#include <unistd.h>
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void usage(char *name)
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{
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printf("Execution utility for Mininet.\n"
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"usage: %s [-cdnp]\n"
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"-c: close all file descriptors except stdin/out/error\n"
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"-d: detach from tty by calling setsid()\n"
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"-n: run in new network namespace\n"
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"-p: print ^A + pid\n", name);
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}
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int main(int argc, char *argv[])
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{
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char c;
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int fd;
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while ((c = getopt(argc, argv, "+cdnp")) != -1)
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switch(c) {
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case 'c':
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/* close file descriptors except stdin/out/error */
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for (fd = getdtablesize(); fd > 2; fd--)
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close(fd);
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break;
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case 'd':
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/* detach from tty */
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if (getpgrp() == getpid()) {
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switch(fork()) {
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case -1:
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perror("fork");
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return 1;
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case 0: /* child */
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break;
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default: /* parent */
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return 0;
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}
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}
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setsid();
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break;
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case 'n':
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/* run in network namespace */
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if (unshare(CLONE_NEWNET) == -1) {
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perror("unshare");
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return 1;
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}
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break;
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case 'p':
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/* print pid */
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printf("\001%d\n", getpid());
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fflush(stdout);
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break;
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default:
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usage(argv[0]);
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break;
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}
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if (optind < argc) {
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execvp(argv[optind], &argv[optind]);
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perror(argv[optind]);
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return 1;
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}
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usage(argv[0]);
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}
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