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/* This is a more significant example of a tool which can grab the
* DHCP address from some types of virtual machine. Since there are
* so many possible ways to do this, without clarity on which is the
* best way, I don't want to make this into an official virt tool.
*
* For more information, see:
*
* https://rwmj.wordpress.com/2010/10/26/tip-find-the-ip-address-of-a-virtual-machine/
* https://rwmj.wordpress.com/2011/03/30/tip-another-way-to-get-the-ip-address-of-a-virtual-machine/
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <assert.h>
#include <guestfs.h>
static int compare_keys_len (const void *p1, const void *p2);
static size_t count_strings (char *const *argv);
static void free_strings (char **argv);
static void mount_disks (guestfs_h *g, char *root);
static void print_dhcp_address (guestfs_h *g, char *root);
static void print_dhcp_address_linux (guestfs_h *g, char *root, const char *logfile);
static void print_dhcp_address_windows (guestfs_h *g, char *root);
int
main (int argc, char *argv[])
{
guestfs_h *g;
size_t i;
char **roots, *root;
if (argc < 2) {
fprintf (stderr,
"Usage: virt-dhcp-address disk.img [disk.img [...]]\n"
"Note that all disks must come from a single virtual machine.\n");
exit (EXIT_FAILURE);
}
g = guestfs_create ();
if (g == NULL) {
perror ("failed to create libguestfs handle");
exit (EXIT_FAILURE);
}
for (i = 1; i < (size_t) argc; ++i) {
/* Attach the disk image(s) read-only to libguestfs. */
if (guestfs_add_drive_opts (g, argv[i],
/* GUESTFS_ADD_DRIVE_OPTS_FORMAT, "raw", */
GUESTFS_ADD_DRIVE_OPTS_READONLY, 1,
-1) /* this marks end of optional arguments */
== -1)
exit (EXIT_FAILURE);
}
/* Run the libguestfs back-end. */
if (guestfs_launch (g) == -1)
exit (EXIT_FAILURE);
/* Ask libguestfs to inspect for operating systems. */
roots = guestfs_inspect_os (g);
if (roots == NULL)
exit (EXIT_FAILURE);
if (roots[0] == NULL) {
fprintf (stderr, "virt-dhcp-address: no operating systems found\n");
exit (EXIT_FAILURE);
}
if (count_strings (roots) > 1) {
fprintf (stderr, "virt-dhcp-address: multi-boot operating system\n");
exit (EXIT_FAILURE);
}
root = roots[0];
/* Mount up the guest's disks. */
mount_disks (g, root);
/* Print DHCP address. */
print_dhcp_address (g, root);
/* Close handle and exit. */
guestfs_close (g);
free_strings (roots);
exit (EXIT_SUCCESS);
}
static void
mount_disks (guestfs_h *g, char *root)
{
char **mountpoints;
size_t i;
/* Mount up the disks, like guestfish -i.
*
* Sort keys by length, shortest first, so that we end up
* mounting the filesystems in the correct order.
*/
mountpoints = guestfs_inspect_get_mountpoints (g, root);
if (mountpoints == NULL)
exit (EXIT_FAILURE);
qsort (mountpoints, count_strings (mountpoints) / 2, 2 * sizeof (char *),
compare_keys_len);
for (i = 0; mountpoints[i] != NULL; i += 2) {
/* Ignore failures from this call, since bogus entries can
* appear in the guest's /etc/fstab.
*/
guestfs_mount_ro (g, mountpoints[i+1], mountpoints[i]);
}
free_strings (mountpoints);
}
static void
print_dhcp_address (guestfs_h *g, char *root)
{
char *guest_type, *guest_distro;
/* Depending on the guest type, try to get the DHCP address. */
guest_type = guestfs_inspect_get_type (g, root);
if (guest_type == NULL)
exit (EXIT_FAILURE);
if (strcmp (guest_type, "linux") == 0) {
guest_distro = guestfs_inspect_get_distro (g, root);
if (guest_distro == NULL)
exit (EXIT_FAILURE);
if (strcmp (guest_distro, "fedora") == 0 ||
strcmp (guest_distro, "rhel") == 0 ||
strcmp (guest_distro, "redhat-based") == 0) {
print_dhcp_address_linux (g, root, "/var/log/messages");
}
else if (strcmp (guest_distro, "debian") == 0 ||
strcmp (guest_distro, "ubuntu") == 0) {
print_dhcp_address_linux (g, root, "/var/log/syslog");
}
else {
fprintf (stderr, "virt-dhcp-address: don't know how to get DHCP address from '%s'\n",
guest_distro);
exit (EXIT_FAILURE);
}
free (guest_distro);
}
else if (strcmp (guest_type, "windows") == 0) {
print_dhcp_address_windows (g, root);
}
else {
fprintf (stderr, "virt-dhcp-address: don't know how to get DHCP address from '%s'\n",
guest_type);
exit (EXIT_FAILURE);
}
free (guest_type);
}
/* Look for dhclient messages in logfile.
*/
static void
print_dhcp_address_linux (guestfs_h *g, char *root, const char *logfile)
{
char **lines, *p;
size_t len;
lines = guestfs_grep_opts (g, "dhclient.*: bound to ", logfile,
GUESTFS_GREP_OPTS_EXTENDED, 1,
-1);
if (lines == NULL)
exit (EXIT_FAILURE);
len = count_strings (lines);
if (len == 0) {
fprintf (stderr, "virt-dhcp-address: cannot find DHCP address for this guest.\n");
exit (EXIT_FAILURE);
}
/* Only want the last message. */
p = strstr (lines[len-1], "bound to ");
assert (p);
p += 9;
len = strcspn (p, " ");
p[len] = '\0';
printf ("%s\n", p);
free_strings (lines);
}
/* Download the Windows SYSTEM hive and find DHCP configuration in there. */
static void
print_dhcp_address_windows (guestfs_h *g, char *root_fs)
{
char *system_path;
int64_t root, node, value;
struct guestfs_hivex_node_list *nodes;
char *controlset;
size_t i;
char *p;
/* Locate the SYSTEM hive case-sensitive path. */
system_path =
guestfs_case_sensitive_path (g, "/windows/system32/config/system");
if (!system_path) {
fprintf (stderr, "virt-dhcp-address: HKLM\\System not found in this guest.");
exit (EXIT_FAILURE);
}
/* Open the hive to parse it. Note that before libguestfs 1.19.35
* you had to download the file and parse it using hivex(3). Since
* libguestfs 1.19.35, parts of the hivex(3) API are now exposed
* through libguestfs, and that is what we'll use here because it is
* more convenient and avoids having to download the hive.
*/
if (guestfs_hivex_open (g, system_path, -1) == -1)
exit (EXIT_FAILURE);
free (system_path);
root = guestfs_hivex_root (g);
if (root == -1)
exit (EXIT_FAILURE);
/* Get ControlSetXXX\Services\Tcpip\Parameters\Interfaces. */
controlset = guestfs_inspect_get_windows_current_control_set (g, root_fs);
if (controlset == NULL)
exit (EXIT_FAILURE);
const char *path[] = { controlset, "Services", "Tcpip", "Parameters",
"Interfaces" };
node = root;
for (i = 0; node > 0 && i < sizeof path / sizeof path[0]; ++i)
node = guestfs_hivex_node_get_child (g, node, path[i]);
if (node == -1)
exit (EXIT_FAILURE);
if (node == 0) {
fprintf (stderr, "virt-dhcp-address: HKLM\\System\\%s\\Services\\Tcpip\\Parameters\\Interfaces not found.", controlset);
exit (EXIT_FAILURE);
}
free (controlset);
/* Look for a node under here which has a "DhcpIPAddress" entry in it. */
nodes = guestfs_hivex_node_children (g, node);
if (nodes == NULL)
exit (EXIT_FAILURE);
value = 0;
for (i = 0; value == 0 && i < nodes->len; ++i) {
value = guestfs_hivex_node_get_value (g, nodes->val[i].hivex_node_h,
"DhcpIPAddress");
if (value == -1)
exit (EXIT_FAILURE);
}
if (value == 0) {
fprintf (stderr, "virt-dhcp-address: cannot find DHCP address for this guest.\n");
exit (EXIT_FAILURE);
}
guestfs_free_hivex_node_list (nodes);
/* Get the string and use libguestfs's auto-conversion to convert it
* to UTF-8 for output.
*/
p = guestfs_hivex_value_utf8 (g, value);
if (!p)
exit (EXIT_FAILURE);
printf ("%s\n", p);
free (p);
/* Close the hive handle. */
guestfs_hivex_close (g);
}
static int
compare_keys_len (const void *p1, const void *p2)
{
const char *key1 = * (char * const *) p1;
const char *key2 = * (char * const *) p2;
return strlen (key1) - strlen (key2);
}
static size_t
count_strings (char *const *argv)
{
size_t c;
for (c = 0; argv[c]; ++c)
;
return c;
}
static void
free_strings (char **argv)
{
size_t i;
for (i = 0; argv[i]; ++i)
free (argv[i]);
free (argv);
}
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