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/* |
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qemu-start.c - Part of qemu-start, a package to start qemu nicely. |
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Copyright (c) 2006 Frodo Looijaard <frodo@frodo.looijaard.name> |
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|
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This program is free software; you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation; either version 2 of the License, or |
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(at your option) any later version. |
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|
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This program is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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|
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You should have received a copy of the GNU General Public License |
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along with this program; if not, write to the Free Software |
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
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*/ |
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|
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#define _GNU_SOURCE /* asprintf */ |
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#include <stdio.h> |
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#include <string.h> |
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#include <sys/types.h> |
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#include <pwd.h> |
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#include <grp.h> |
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#include <sys/stat.h> |
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#include <sys/ioctl.h> |
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#include <fcntl.h> |
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#include <unistd.h> |
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#include <stdlib.h> |
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#include <net/if.h> |
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#include <linux/if_tun.h> |
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#include <sys/wait.h> |
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#include <errno.h> |
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|
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/* This define is present in recent glibc, it is not available on sarge */ |
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#ifndef HOST_NAME_MAX |
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#define HOST_NAME_MAX 64 |
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#endif |
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|
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#define QEMU "/usr/bin/qemu" |
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#define USER "qemu" |
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|
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/* |
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* This function merges the xauthority data of the current X context |
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* into the QEMU user's .Xauthority file. |
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*/ |
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void fix_xauthority(void) { |
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struct passwd *userdata; |
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int pfd[2]; |
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char *xauthfile; |
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char *display; |
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char *newdisplay; |
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char *hostname; |
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// int status1, status2; |
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int status,pid; |
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pid_t cpid1, cpid2; |
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|
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if (pipe(pfd)) { |
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perror("pipe failed"); |
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exit(1); |
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} |
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|
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cpid1 = fork(); |
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if (cpid1 < 0) { |
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perror("first fork failed"); |
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exit(1); |
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} |
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|
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/* Child: will execute the xauth extract */ |
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if (cpid1 == 0) { |
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/* Child may run as original process starter */ |
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if (setgroups(0, NULL)) { |
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perror("setgroups failed"); |
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exit(1); |
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} |
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if (setgid(getgid())) { |
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perror("setgid failed"); |
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exit(1); |
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} |
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if (setuid(getuid())) { |
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perror("setuid failed"); |
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exit(1); |
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} |
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|
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/* Write side of pipe corresponds to stdout */ |
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if (dup2(pfd[1],1) < 0) { |
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perror("dup2 failed"); |
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exit(1); |
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} |
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if (close(pfd[0])) { |
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perror("close of pfd[0] failed"); |
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exit(1); |
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} |
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if (close(pfd[1])) { |
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perror("close of pfd[1] failed"); |
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exit(1); |
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} |
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|
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userdata = getpwuid(getuid()); |
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if (!userdata) { |
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fprintf(stderr, "No user '%s'\n", USER); |
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exit(1); |
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} |
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|
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|
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/* Get xauthority file to use */ |
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if (! (xauthfile = getenv("XAUTHORITY"))) { |
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if (asprintf(&xauthfile,"%s/.Xauthority",userdata->pw_dir) < 1) { |
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perror("Constructing xauthority filename failed"); |
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exit(1); |
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} |
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} |
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|
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/* Get display */ |
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if (! (display = getenv("DISPLAY"))) { |
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perror("No DISPLAY variable found\n"); |
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exit(1); |
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} |
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|
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/* Substitution: if display starts with `localhost', substitute |
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`localhost' by `HOSTNAME/unix'. */ |
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if (strstr(display,"localhost") == display) { |
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hostname = malloc(HOST_NAME_MAX+1); |
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if (gethostname(hostname,HOST_NAME_MAX+1)) { |
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perror("Getting hostname failed"); |
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exit(1); |
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} |
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|
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if (!(newdisplay = malloc(strlen(hostname) + 5 + strlen(display)-9 + 1))) { |
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perror("Allocating new display failed"); |
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exit(1); |
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} |
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strcpy(newdisplay,hostname); |
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strcpy(newdisplay + strlen(hostname),"/unix"); |
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strcpy(newdisplay + strlen(hostname) + 5, display + 9); |
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display = newdisplay; |
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} else if (! (display = strdup(display))) { |
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perror("strdup DISPLAY failed"); |
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exit(1); |
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} |
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|
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execl("/usr/bin/X11/xauth","/usr/bin/X11/xauth","-f",xauthfile,"extract","-",display,NULL); |
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exit(1); |
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} |
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|
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|
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cpid2 = fork(); |
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if (cpid2 < 0) { |
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perror("second fork failed"); |
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exit(1); |
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} |
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|
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/* Child: will execute the xauth merge */ |
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if (cpid2 == 0) { |
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/* Get userid data. */ |
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userdata = getpwnam(USER); |
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if (!userdata) { |
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fprintf(stderr, "No user '%s'\n", USER); |
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exit(1); |
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} |
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|
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if (setgroups(0, NULL)) { |
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perror("setgroups failed"); |
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exit(1); |
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} |
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|
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/* Child may run as qemu user */ |
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if (setgid(userdata->pw_gid)) { |
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perror("setgid failed"); |
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exit(1); |
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} |
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if (setuid(userdata->pw_uid)) { |
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perror("setuid failed"); |
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exit(1); |
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} |
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/* Read side of pipe is stdin */ |
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if (dup2(pfd[0],0) < 0) { |
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perror("dup2 failed"); |
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exit(1); |
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} |
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if (close(pfd[0])) { |
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perror("close of pfd[0] failed"); |
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exit(1); |
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} |
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if (close(pfd[1])) { |
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perror("close of pfd[1] failed"); |
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exit(1); |
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} |
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|
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if (asprintf(&xauthfile,"%s/.Xauthority",userdata->pw_dir) < 1) { |
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perror("Constructing xauthority filename failed"); |
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exit(1); |
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} |
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|
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execl("/usr/bin/X11/xauth","/usr/bin/X11/xauth","-f",xauthfile,"merge","-",NULL); |
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exit(1); |
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} |
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|
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if (close(pfd[0])) { |
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perror("close of pfd[0] failed"); |
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exit(1); |
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} |
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if (close(pfd[1])) { |
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perror("close of pfd[1] failed"); |
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exit(1); |
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} |
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|
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while(1) { |
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|
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pid = wait(&status); |
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if ((pid < 1) && (errno == ECHILD)) |
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break; |
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if (pid < 1) { |
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perror("wait failed"); |
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exit(1); |
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} |
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if (! WIFEXITED(status) || WEXITSTATUS(status)) { |
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fprintf(stderr,"Child returned error"); |
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exit(1); |
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} |
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} |
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} |
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|
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|
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/* Tiny code to open tap/tun device, and hand the fd to qemu. |
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Run as root, drops to given user. */ |
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int main(int argc, char *argv[]) |
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{ |
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struct ifreq ifr; |
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struct passwd *userdata; |
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char *newargs[argc + 2]; |
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int i,fd,vlan,tapnr; |
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char *ptr; |
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char *display; |
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|
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/* Check parameters */ |
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if (argc < 4) { |
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fprintf(stderr, "Usage: qemu-start TAPDEVNR VLAN SYSTEM <qemu options>...\n"); |
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fprintf(stderr, " A device tapTAPDEVNR must have been configured.\n"); |
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fprintf(stderr, " VLAN is the Virtual LAN number (just use 0 if unsure).\n"); |
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fprintf(stderr, " SYSTEM is the system to emulate. Use \"\" for the current architecture\n"); |
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fprintf(stderr, " (uses /usr/bin/qemm); else a binary /usr/bin/qemu-system-SYSTEM is used.\n"); |
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exit(1); |
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} |
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|
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/* First parameter: TAPDEVNR */ |
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tapnr = strtol(argv[1],&ptr,0); |
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if (*ptr) { |
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fprintf(stderr, "Invalid value `%s' for TAPDEVNR parameter (use a number!)\n",argv[1]); |
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exit(1); |
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} |
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|
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/* Second parameter: VLAN */ |
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vlan = strtol(argv[2],&ptr,0); |
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if (*ptr) { |
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fprintf(stderr, "Invalid value `%s' for VLAN parameter (use a number!)\n", argv[2]); |
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exit(1); |
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} |
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|
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/* Third parameter: System type */ |
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if (index(argv[3],'/')) { |
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fprintf(stderr, "Invalid value `%s' for system (may not contain a slash character)\n", argv[3]); |
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exit(1); |
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} |
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|
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/* Export the xauth data */ |
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fix_xauthority(); |
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|
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/* Open /dev/net/tun */ |
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fd = open("/dev/net/tun", O_RDWR); |
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if (fd < 0) { |
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perror("Could not open /dev/net/tun"); |
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exit(1); |
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} |
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|
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/* Bind to the right tap device */ |
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memset(&ifr, 0, sizeof(ifr)); |
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ifr.ifr_flags = IFF_TAP | IFF_NO_PI; |
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snprintf(ifr.ifr_name,IFNAMSIZ,"tap%d",tapnr); |
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|
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if (ioctl(fd, TUNSETIFF, (void *) &ifr) != 0) { |
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perror("Could not get tap device"); |
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exit(1); |
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} |
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|
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/* Get userid data. */ |
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userdata = getpwnam(USER); |
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if (!userdata) { |
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fprintf(stderr, "No user '%s'\n", USER); |
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exit(1); |
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} |
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|
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/* Change to QEMU user */ |
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if (setgroups(0, NULL)) { |
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perror("setgroups failed"); |
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exit(1); |
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} |
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if (setgid(userdata->pw_gid)) { |
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perror("setgid failed"); |
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exit(1); |
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} |
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if (setuid(userdata->pw_uid)) { |
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perror("setuid failed"); |
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exit(1); |
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} |
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|
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/* Clean the environment */ |
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if(!(display=getenv("DISPLAY"))) { |
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perror("Getting DISPLAY failed"); |
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exit(1); |
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} |
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if(clearenv()) { |
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perror("Clearing environment failed"); |
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exit(1); |
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} |
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if(setenv("HOME",userdata->pw_dir,1) || |
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setenv("DISPLAY",display,1) || |
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setenv("PATH","/usr/bin:/bin:/usr/local/bin",1) || |
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setenv("LOGNAME",userdata->pw_name,1) || |
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setenv("USER",userdata->pw_name,1)) { |
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perror("Setting environment failed"); |
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exit(1); |
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} |
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|
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/* Create the right qemu invocation */ |
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if (!strlen(argv[3])) |
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newargs[0] = QEMU; |
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else if (asprintf(&newargs[0],"%s-system-%s",QEMU,argv[3]) < 0) { |
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perror("Preparing qemu executable filename failed"); |
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exit(1); |
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} |
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newargs[1] = "-net"; |
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if (asprintf(&newargs[2],"nic,vlan=%d",vlan) < 0) { |
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perror("Preparing nic argument failed"); |
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exit(1); |
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} |
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newargs[3] = "-net"; |
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if (asprintf(&newargs[4],"tap,fd=%d,vlan=%d",fd,vlan) < 0) { |
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perror("Preparing tap argument failed"); |
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exit(1); |
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} |
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for (i = 4; i <= argc; i++) |
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newargs[i+1] = argv[i]; |
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|
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execvp(newargs[0], newargs); |
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perror("Execution of qemu failed"); |
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exit(1); |
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} |
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