qemu-start/trunk/qemu-start.c

/*
    qemu-start.c - Part of qemu-start, a package to start qemu nicely.
    Copyright (c) 2006  Frodo Looijaard <frodo@frodo.looijaard.name>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#define _GNU_SOURCE /* asprintf */
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <net/if.h>
#include <linux/if_tun.h>

#define QEMU "/usr/bin/qemu"
#define USER "qemu"

/* Tiny code to open tap/tun device, and hand the fd to qemu.
   Run as root, drops to given user. */
int main(int argc, char *argv[])
{
        struct ifreq ifr;
        struct passwd *userdata;
        char *newargs[argc + 2];
        int i,fd,vlan,tapnr;
        char *ptr;
        char *command;
        char *display;
        char *xauthfile;

        /* Check parameters */
        if (argc < 4) {
                fprintf(stderr, "Usage: qemu-start TAPDEVNR VLAN SYSTEM <qemu options>...\n");
                fprintf(stderr, "  A device tapTAPDEVNR must have been configured.\n");
                fprintf(stderr, "  VLAN is the Virtual LAN number (just use 0 if unsure).\n");
                fprintf(stderr, "  SYSTEM is the system to emulate. Use \"\" for the current architecture\n");
                fprintf(stderr, "  (uses /usr/bin/qemm); else a binary /usr/bin/qemu-system-SYSTEM is used.\n");
                exit(1);
        }

        /* First parameter: TAPDEVNR */
        tapnr = strtol(argv[1],&ptr,0);
        if (*ptr) {
                fprintf(stderr, "Invalid value for TAPDEVNR parameter (use a number!)\n");
                exit(1);
        }

        /* Second parameter: VLAN */
        vlan = strtol(argv[2],&ptr,0);
        if (*ptr) {
                fprintf(stderr, "Invalid value for VLAN parameter (use a number!)\n");
                exit(1);
        }

        /* Open /dev/net/tun */
        fd = open("/dev/net/tun", O_RDWR);
        if (fd < 0) {
                perror("Could not open /dev/net/tun");
                exit(1);
        }

        /* Bind to the right tap device */
        memset(&ifr, 0, sizeof(ifr));
        ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
        snprintf(ifr.ifr_name,IFNAMSIZ,"tap%d",tapnr);

        if (ioctl(fd, TUNSETIFF, (void *) &ifr) != 0) {
                perror("Could not get tap device");
                exit(1);
        }

        /* Fix X-display */
        userdata = getpwuid(getuid());
        if (! (xauthfile = getenv("XAUTHORITY")))
                asprintf(&xauthfile,"~%s/.Xauthority",userdata->pw_name);
        setuid(0);
        setgid(0);
        asprintf(&command,"xauth -f %s extract - $(echo $DISPLAY|sed \"s,^localhost,$(hostname)/unix,\") | xauth -f ~%s/.Xauthority merge -; chown %s: ~%s/.Xauthority",xauthfile,USER,USER,USER);
fprintf(stderr,"%s\n",command);
        system(command);

        /* Set correct userid. */
        userdata = getpwnam(USER);
        if (!userdata) {
                fprintf(stderr, "No user '%s'\n", USER);
                exit(1);
        }
        setgroups(0, NULL);
        setgid(userdata->pw_gid);
        if (setuid(userdata->pw_uid) != 0) {
                perror("setting uid");
                exit(1);
        }

        /* Clean the environment */
        display=getenv("DISPLAY");
        clearenv();
        setenv("HOME",userdata->pw_dir,1);
        setenv("DISPLAY",display,1);
        setenv("PATH","/usr/bin:/bin:/usr/local/bin",1);
        setenv("LOGNAME",userdata->pw_name,1);
        setenv("USER",userdata->pw_name,1);

        /* Create the right qemu invocation */
        if (!strlen(argv[3]))
                newargs[0] = QEMU;
        else
                asprintf(&newargs[0],"%s-system-%s",QEMU,argv[3]);
        newargs[1] = "-net";
        asprintf(&newargs[2],"nic,vlan=%d",vlan);
        newargs[3] = "-net";
        asprintf(&newargs[4],"tap,fd=%d,vlan=%d",fd,vlan);
        for (i = 4; i <= argc; i++)
                newargs[i+1] = argv[i];

        execvp(newargs[0], newargs);
        exit(1);
}
1	frodo	290	/*
2			qemu-start.c - Part of qemu-start, a package to start qemu nicely.
3			Copyright (c) 2006 Frodo Looijaard <frodo@frodo.looijaard.name>
4
5			This program is free software; you can redistribute it and/or modify
6			it under the terms of the GNU General Public License as published by
7			the Free Software Foundation; either version 2 of the License, or
8			(at your option) any later version.
9
10			This program is distributed in the hope that it will be useful,
11			but WITHOUT ANY WARRANTY; without even the implied warranty of
12			MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13			GNU General Public License for more details.
14
15			You should have received a copy of the GNU General Public License
16			along with this program; if not, write to the Free Software
17			Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18			*/
19
20			#define _GNU_SOURCE /* asprintf */
21			#include <stdio.h>
22			#include <string.h>
23			#include <sys/types.h>
24			#include <pwd.h>
25			#include <grp.h>
26			#include <sys/stat.h>
27			#include <sys/ioctl.h>
28			#include <fcntl.h>
29			#include <unistd.h>
30			#include <stdlib.h>
31			#include <net/if.h>
32			#include <linux/if_tun.h>
33
34			#define QEMU "/usr/bin/qemu"
35			#define USER "qemu"
36
37			/* Tiny code to open tap/tun device, and hand the fd to qemu.
38			Run as root, drops to given user. */
39			int main(int argc, char *argv[])
40			{
41			struct ifreq ifr;
42			struct passwd *userdata;
43			char *newargs[argc + 2];
44			int i,fd,vlan,tapnr;
45			char *ptr;
46			char *command;
47			char *display;
48	frodo	292	char *xauthfile;
49	frodo	290
50			/* Check parameters */
51			if (argc < 4) {
52			fprintf(stderr, "Usage: qemu-start TAPDEVNR VLAN SYSTEM <qemu options>...\n");
53			fprintf(stderr, " A device tapTAPDEVNR must have been configured.\n");
54			fprintf(stderr, " VLAN is the Virtual LAN number (just use 0 if unsure).\n");
55			fprintf(stderr, " SYSTEM is the system to emulate. Use \"\" for the current architecture\n");
56			fprintf(stderr, " (uses /usr/bin/qemm); else a binary /usr/bin/qemu-system-SYSTEM is used.\n");
57			exit(1);
58			}
59
60			/* First parameter: TAPDEVNR */
61			tapnr = strtol(argv[1],&ptr,0);
62			if (*ptr) {
63			fprintf(stderr, "Invalid value for TAPDEVNR parameter (use a number!)\n");
64			exit(1);
65			}
66
67			/* Second parameter: VLAN */
68			vlan = strtol(argv[2],&ptr,0);
69			if (*ptr) {
70			fprintf(stderr, "Invalid value for VLAN parameter (use a number!)\n");
71			exit(1);
72			}
73
74			/* Open /dev/net/tun */
75			fd = open("/dev/net/tun", O_RDWR);
76			if (fd < 0) {
77			perror("Could not open /dev/net/tun");
78			exit(1);
79			}
80
81			/* Bind to the right tap device */
82			memset(&ifr, 0, sizeof(ifr));
83			ifr.ifr_flags = IFF_TAP \| IFF_NO_PI;
84			snprintf(ifr.ifr_name,IFNAMSIZ,"tap%d",tapnr);
85
86			if (ioctl(fd, TUNSETIFF, (void *) &ifr) != 0) {
87			perror("Could not get tap device");
88			exit(1);
89			}
90
91			/* Fix X-display */
92			userdata = getpwuid(getuid());
93	frodo	292	if (! (xauthfile = getenv("XAUTHORITY")))
94			asprintf(&xauthfile,"~%s/.Xauthority",userdata->pw_name);
95	frodo	290	setuid(0);
96			setgid(0);
97	frodo	292	asprintf(&command,"xauth -f %s extract - $(echo $DISPLAY\|sed \"s,^localhost,$(hostname)/unix,\") \| xauth -f ~%s/.Xauthority merge -; chown %s: ~%s/.Xauthority",xauthfile,USER,USER,USER);
98			fprintf(stderr,"%s\n",command);
99	frodo	290	system(command);
100
101			/* Set correct userid. */
102			userdata = getpwnam(USER);
103			if (!userdata) {
104			fprintf(stderr, "No user '%s'\n", USER);
105			exit(1);
106			}
107			setgroups(0, NULL);
108			setgid(userdata->pw_gid);
109			if (setuid(userdata->pw_uid) != 0) {
110			perror("setting uid");
111			exit(1);
112			}
113
114			/* Clean the environment */
115			display=getenv("DISPLAY");
116			clearenv();
117			setenv("HOME",userdata->pw_dir,1);
118			setenv("DISPLAY",display,1);
119			setenv("PATH","/usr/bin:/bin:/usr/local/bin",1);
120			setenv("LOGNAME",userdata->pw_name,1);
121			setenv("USER",userdata->pw_name,1);
122
123			/* Create the right qemu invocation */
124			if (!strlen(argv[3]))
125			newargs[0] = QEMU;
126			else
127			asprintf(&newargs[0],"%s-system-%s",QEMU,argv[3]);
128			newargs[1] = "-net";
129			asprintf(&newargs[2],"nic,vlan=%d",vlan);
130			newargs[3] = "-net";
131			asprintf(&newargs[4],"tap,fd=%d,vlan=%d",fd,vlan);
132			for (i = 4; i <= argc; i++)
133			newargs[i+1] = argv[i];
134
135			execvp(newargs[0], newargs);
136			exit(1);
137			}
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