From 2d013d5d67d5896869dff4b08c0674b2d91e721f Mon Sep 17 00:00:00 2001

From: "Richard W.M. Jones" <rjones@redhat.com>

Date: Thu, 2 Mar 2017 13:46:48 +0000

Subject: [PATCH] rescue: Modify virt-rescue so it doesn't use direct mode

 (RHBZ#1152819, RHBZ#1171654).

Instead of using "direct mode" (which was basically a quick hack),

virt-rescue now launches the appliance with a running daemon.

The daemon doesn't do much -- there is still a bash shell which the

user interacts with.  The daemon is there simply to provide the

initial GUESTFS_LAUNCH_FLAG message and to handle shutdown a bit more

gracefully.

To interact with the shell, and replacing direct mode, virt-rescue now

prints out log messages (the output of the shell), and sends input

typed by the user directly to the console socket.  This uses the

guestfs_internal_get_console_socket API added previously.  Most of the

complexity behind this is hidden in virt-rescue.

This fully fixes the handling of ^C (RHBZ#1152819).  Also there were

earlier reports that full screen commands like 'vim' didn't work well,

(RHBZ#1171654), but in this version vim appears to work fine, albeit

only using 80x24 of the screen because of the serial console.

(cherry picked from commit 32d60801443647b3523b9374c431fefdbf054e3c)

---

 appliance/init     |  93 ++++++++--------

 rescue/Makefile.am |   1 +

 rescue/rescue.c    | 306 +++++++++++++++++++++++++++++++++++++++++++++--------

 3 files changed, 313 insertions(+), 87 deletions(-)

diff --git a/appliance/init b/appliance/init

index 735ba8946..ea763c2d3 100755

--- a/appliance/init

+++ b/appliance/init

@@ -160,60 +160,63 @@ if test "$guestfs_verbose" = 1 && test "$guestfs_boot_analysis" != 1; then

     echo -n "uptime: "; cat /proc/uptime

 fi

-if ! test "$guestfs_rescue" = 1; then

-  # Run the daemon.

-  cmd="guestfsd"

-  eval `grep -Eo 'guestfs_channel=[^[:space:]]+' /proc/cmdline`

-  if test "x$guestfs_channel" != "x"; then

+# Run the daemon.

+cmd="guestfsd"

+eval `grep -Eo 'guestfs_channel=[^[:space:]]+' /proc/cmdline`

+if test "x$guestfs_channel" != "x"; then

     cmd="$cmd --channel $guestfs_channel"

-  fi

-  if test "$guestfs_verbose" = 1; then

+fi

+if test "$guestfs_verbose" = 1; then

     cmd="$cmd --verbose"

-  fi

-  if test "$guestfs_network" = 1; then

+fi

+if test "$guestfs_network" = 1; then

     cmd="$cmd --network"

-  fi

-  echo $cmd

-  $cmd

+fi

+if ! test "$guestfs_rescue" = 1; then

+    echo $cmd

+    $cmd

 else

-  # Run virt-rescue shell.

+    # Run virt-rescue shell.

-  # Get name of the serial port, from console= passed by libguestfs.

-  # XXX Consider using /proc/consoles

-  guestfs_serial=$(grep -Eo 'console=[^[:space:]]+' /proc/cmdline |

-                   sed s/console=//)

+    # We need a daemon, even in virt-rescue.

+    $cmd &

-  # Remove LD_PRELOAD=libSegFault set above.

-  unset LD_PRELOAD

+    # Get name of the serial port, from console= passed by libguestfs.

+    # XXX Consider using /proc/consoles

+    guestfs_serial=$(grep -Eo 'console=[^[:space:]]+' /proc/cmdline |

+                     sed s/console=//)

-  :> $HOME/.bashrc

-  grep -Eo 'TERM=[^[:space:]]+' /proc/cmdline >> $HOME/.bashrc

-  echo "PS1='><rescue> '" >> $HOME/.bashrc

-  echo "export TERM PS1" >> $HOME/.bashrc

+    # Remove LD_PRELOAD=libSegFault set above.

+    unset LD_PRELOAD

-  # The shell is opened by default on /dev/console, which (on Linux)

-  # is not a controlling terminal, causing job control to fail.  For

-  # how we work around this, see:

-  # https://busybox.net/FAQ.html#job_control

-  run_bash_with_ctty ()

-  {

-    setsid bash -c \

-      "exec bash </dev/$guestfs_serial >/dev/$guestfs_serial 2>&1"

-  }

+    :> $HOME/.bashrc

+    grep -Eo 'TERM=[^[:space:]]+' /proc/cmdline >> $HOME/.bashrc

+    echo "PS1='><rescue> '" >> $HOME/.bashrc

+    echo "export TERM PS1" >> $HOME/.bashrc

-  echo

-  echo "------------------------------------------------------------"

-  echo

-  echo "Welcome to virt-rescue, the libguestfs rescue shell."

-  echo

-  echo "Note: The contents of / are the rescue appliance."

-  echo "You have to mount the guest's partitions under /sysroot"

-  echo "before you can examine them."

-  echo

-  run_bash_with_ctty

-  echo

-  echo "virt-rescue: Syncing the disk now before exiting ..."

-  echo

+    # The shell is opened by default on /dev/console, which (on Linux)

+    # is not a controlling terminal, causing job control to fail.  For

+    # how we work around this, see:

+    # https://busybox.net/FAQ.html#job_control

+    run_bash_with_ctty ()

+    {

+        setsid bash -c \

+            "exec bash </dev/$guestfs_serial >/dev/$guestfs_serial 2>&1"

+    }

+

+    echo

+    echo "------------------------------------------------------------"

+    echo

+    echo "Welcome to virt-rescue, the libguestfs rescue shell."

+    echo

+    echo "Note: The contents of / (root) are the rescue appliance."

+    echo "You have to mount the guest's partitions under /sysroot"

+    echo "before you can examine them."

+    echo

+    run_bash_with_ctty

+    echo

+    echo "virt-rescue: Syncing the disk now before exiting ..."

+    echo

 fi

 sync

diff --git a/rescue/Makefile.am b/rescue/Makefile.am

index 7919aafd5..99d4b79ae 100644

--- a/rescue/Makefile.am

+++ b/rescue/Makefile.am

@@ -30,6 +30,7 @@ virt_rescue_SOURCES = \

 virt_rescue_CPPFLAGS = \

 	-DGUESTFS_WARN_DEPRECATED=1 \

+	-DGUESTFS_PRIVATE=1 \

 	-DLOCALEBASEDIR=\""$(datadir)/locale"\" \

 	-I$(top_srcdir)/common/utils -I$(top_builddir)/common/utils \

 	-I$(top_srcdir)/lib -I$(top_builddir)/lib \

diff --git a/rescue/rescue.c b/rescue/rescue.c

index b692e5a07..b145dcd40 100644

--- a/rescue/rescue.c

+++ b/rescue/rescue.c

@@ -23,21 +23,32 @@

 #include <string.h>

 #include <inttypes.h>

 #include <unistd.h>

+#include <fcntl.h>

 #include <getopt.h>

 #include <errno.h>

 #include <error.h>

+#include <signal.h>

+#include <termios.h>

+#include <poll.h>

 #include <locale.h>

 #include <assert.h>

 #include <libintl.h>

+#include "full-write.h"

+#include "getprogname.h"

 #include "ignore-value.h"

 #include "xvasprintf.h"

-#include "getprogname.h"

 #include "guestfs.h"

 #include "options.h"

 #include "display-options.h"

+static void log_message_callback (guestfs_h *g, void *opaque, uint64_t event, int event_handle, int flags, const char *buf, size_t buf_len, const uint64_t *array, size_t array_len);

+static void do_rescue (int sock);

+static void raw_tty (void);

+static void restore_tty (void);

+static void tstp_handler (int sig);

+static void cont_handler (int sig);

 static void add_scratch_disks (int n, struct drv **drvs);

 static void do_suggestion (struct drv *drvs);

@@ -54,6 +65,9 @@ int inspector = 0;

 int in_guestfish = 0;

 int in_virt_rescue = 1;

+/* Old terminal settings. */

+static struct termios old_termios;

+

 static void __attribute__((noreturn))

 usage (int status)

 {

@@ -135,6 +149,8 @@ main (int argc, char *argv[])

   int memsize = 0;

   int smp = 0;

   int suggest = 0;

+  char *append_full;

+  int sock;

   g = guestfs_create ();

   if (g == NULL)

@@ -295,30 +311,6 @@ main (int argc, char *argv[])

     usage (EXIT_FAILURE);

   }

-#pragma GCC diagnostic push

-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"

-  /* Setting "direct mode" is required for the rescue appliance. */

-  if (guestfs_set_direct (g, 1) == -1)

-    exit (EXIT_FAILURE);

-#pragma GCC diagnostic pop

-

-  {

-    /* The libvirt backend doesn't support direct mode.  As a temporary

-     * workaround, force the appliance backend, but warn about it.

-     */

-    CLEANUP_FREE char *backend = guestfs_get_backend (g);

-    if (backend) {

-      if (STREQ (backend, "libvirt") ||

-          STRPREFIX (backend, "libvirt:")) {

-        fprintf (stderr, _("%s: warning: virt-rescue doesn't work with the libvirt backend\n"

-                           "at the moment.  As a workaround, forcing backend = 'direct'.\n"),

-                 getprogname ());

-        if (guestfs_set_backend (g, "direct") == -1)

-          exit (EXIT_FAILURE);

-      }

-    }

-  }

-

   /* Set other features. */

   if (memsize > 0)

     if (guestfs_set_memsize (g, memsize) == -1)

@@ -330,16 +322,15 @@ main (int argc, char *argv[])

     if (guestfs_set_smp (g, smp) == -1)

       exit (EXIT_FAILURE);

-  {

-    /* Kernel command line must include guestfs_rescue=1 (see

-     * appliance/init) as well as other options.

-     */

-    CLEANUP_FREE char *append_full = xasprintf ("guestfs_rescue=1%s%s",

-                                                append ? " " : "",

-                                                append ? append : "");

-    if (guestfs_set_append (g, append_full) == -1)

-      exit (EXIT_FAILURE);

-  }

+  /* Kernel command line must include guestfs_rescue=1 (see

+   * appliance/init) as well as other options.

+   */

+  append_full = xasprintf ("guestfs_rescue=1%s%s",

+                           append ? " " : "",

+                           append ? append : "");

+  if (guestfs_set_append (g, append_full) == -1)

+    exit (EXIT_FAILURE);

+  free (append_full);

   /* Add drives. */

   add_drives (drvs);

@@ -347,22 +338,253 @@ main (int argc, char *argv[])

   /* Free up data structures, no longer needed after this point. */

   free_drives (drvs);

-  /* Run the appliance.  This won't return until the user quits the

-   * appliance.

+  /* Add an event handler to print "log messages".  These will be the

+   * output of the appliance console during launch and shutdown.

+   * After launch, we will read the console messages directly from the

+   * socket and they won't be passed through the event callback.

    */

-  if (!verbose)

-    guestfs_set_error_handler (g, NULL, NULL);

+  if (guestfs_set_event_callback (g, log_message_callback,

+                                  GUESTFS_EVENT_APPLIANCE, 0, NULL) == -1)

+    exit (EXIT_FAILURE);

-  /* We expect launch to fail, so ignore the return value, and don't

-   * bother with explicit guestfs_shutdown either.

+  /* Run the appliance. */

+  if (guestfs_launch (g) == -1)

+    exit (EXIT_FAILURE);

+

+  sock = guestfs_internal_get_console_socket (g);

+  if (sock == -1)

+    exit (EXIT_FAILURE);

+

+  /* Try to set all sockets to non-blocking. */

+  if (fcntl (STDIN_FILENO, F_SETFL, O_NONBLOCK) == -1)

+    perror ("could not set stdin to non-blocking");

+  if (fcntl (STDOUT_FILENO, F_SETFL, O_NONBLOCK) == -1)

+    perror ("could not set stdout to non-blocking");

+  if (fcntl (sock, F_SETFL, O_NONBLOCK) == -1)

+    perror ("could not set console socket to non-blocking");

+

+  /* Save the initial state of the tty so we always have the original

+   * state to go back to.

+   */

+  if (tcgetattr (STDIN_FILENO, &old_termios) == -1) {

+    perror ("tcgetattr: stdin");

+    exit (EXIT_FAILURE);

+  }

+

+  /* Put stdin in raw mode so that we can receive ^C and other

+   * special keys.

+   */

+  raw_tty ();

+

+  /* Restore the tty settings when the process exits. */

+  atexit (restore_tty);

+

+  /* Catch tty stop and cont signals so we can cleanup.

+   * See https://www.gnu.org/software/libc/manual/html_node/Signaling-Yourself.html

    */

-  ignore_value (guestfs_launch (g));

+  signal (SIGTSTP, tstp_handler);

+  signal (SIGCONT, cont_handler);

+

+  do_rescue (sock);

+

+  restore_tty ();

+

+  /* Shut down the appliance. */

+  guestfs_push_error_handler (g, NULL, NULL);

+  if (guestfs_shutdown (g) == -1) {

+    const char *err;

+

+    /* Ignore "appliance closed the connection unexpectedly" since

+     * this can happen if the user reboots the appliance.

+     */

+    if (guestfs_last_errno (g) == EPIPE)

+      goto next;

+    /* Otherwise it's a real error. */

+    err = guestfs_last_error (g);

+    fprintf (stderr, "libguestfs: error: %s\n", err);

+    exit (EXIT_FAILURE);

+  }

+ next:

+  guestfs_pop_error_handler (g);

   guestfs_close (g);

   exit (EXIT_SUCCESS);

 }

+static void

+log_message_callback (guestfs_h *g, void *opaque, uint64_t event,

+                      int event_handle, int flags,

+                      const char *buf, size_t buf_len,

+                      const uint64_t *array, size_t array_len)

+{

+  if (buf_len > 0) {

+    ignore_value (full_write (STDOUT_FILENO, buf, buf_len));

+  }

+}

+

+/* This is the main loop for virt-rescue.  We read and write

+ * directly to the console socket.

+ */

+#define BUFSIZE 4096

+static char rbuf[BUFSIZE];      /* appliance -> local tty */

+static char wbuf[BUFSIZE];      /* local tty -> appliance */

+

+static void

+do_rescue (int sock)

+{

+  size_t rlen = 0;

+  size_t wlen = 0;

+

+  while (sock >= 0 || rlen > 0) {

+    struct pollfd fds[3];

+    nfds_t nfds = 2;

+    int r;

+    ssize_t n;

+

+    fds[0].fd = STDIN_FILENO;

+    fds[0].events = 0;

+    if (BUFSIZE-wlen > 0)

+      fds[0].events = POLLIN;

+    fds[0].revents = 0;

+

+    fds[1].fd = STDOUT_FILENO;

+    fds[1].events = 0;

+    if (rlen > 0)

+      fds[1].events |= POLLOUT;

+    fds[1].revents = 0;

+

+    if (sock >= 0) {

+      fds[2].fd = sock;

+      fds[2].events = 0;

+      if (BUFSIZE-rlen > 0)

+        fds[2].events |= POLLIN;

+      if (wlen > 0)

+        fds[2].events |= POLLOUT;

+      fds[2].revents = 0;

+      nfds++;

+    }

+

+    r = poll (fds, nfds, -1);

+    if (r == -1) {

+      if (errno == EINTR || errno == EAGAIN)

+        continue;

+      perror ("poll");

+      return;

+    }

+

+    /* Input from local tty. */

+    if ((fds[0].revents & POLLIN) != 0) {

+      assert (BUFSIZE-wlen > 0);

+      n = read (STDIN_FILENO, wbuf+wlen, BUFSIZE-wlen);

+      if (n == -1) {

+        if (errno == EINTR || errno == EAGAIN)

+          continue;

+        perror ("read");

+        return;

+      }

+      if (n == 0) {

+        /* We don't expect this to happen.  Maybe the whole tty went away?

+         * Anyway, we should exit as soon as possible.

+         */

+        return;

+      }

+      if (n > 0)

+        wlen += n;

+    }

+

+    /* Log message from appliance. */

+    if (nfds > 2 && (fds[2].revents & POLLIN) != 0) {

+      assert (BUFSIZE-rlen > 0);

+      n = read (sock, rbuf+rlen, BUFSIZE-rlen);

+      if (n == -1) {

+        if (errno == EINTR || errno == EAGAIN)

+          continue;

+        if (errno == ECONNRESET)

+          goto appliance_closed;

+        perror ("read");

+        return;

+      }

+      if (n == 0) {

+      appliance_closed:

+        sock = -1;

+        /* Don't actually close the socket, because it's owned by

+         * the guestfs handle.

+         */

+        continue;

+      }

+      if (n > 0)

+        rlen += n;

+    }

+

+    /* Write log messages to local tty. */

+    if ((fds[1].revents & POLLOUT) != 0) {

+      assert (rlen > 0);

+      n = write (STDOUT_FILENO, rbuf, rlen);

+      if (n == -1) {

+        perror ("write");

+        continue;

+      }

+      rlen -= n;

+      memmove (rbuf, rbuf+n, rlen);

+    }

+

+    /* Write commands to the appliance. */

+    if (nfds > 2 && (fds[2].revents & POLLOUT) != 0) {

+      assert (wlen > 0);

+      n = write (sock, wbuf, wlen);

+      if (n == -1) {

+        perror ("write");

+        continue;

+      }

+      wlen -= n;

+      memmove (wbuf, wbuf+n, wlen);

+    }

+  }

+}

+

+/* Put the tty in raw mode. */

+static void

+raw_tty (void)

+{

+  struct termios termios;

+

+  if (tcgetattr (STDIN_FILENO, &termios) == -1) {

+    perror ("tcgetattr: stdin");

+    exit (EXIT_FAILURE);

+  }

+  cfmakeraw (&termios);

+  if (tcsetattr (STDIN_FILENO, TCSANOW, &termios) == -1) {

+    perror ("tcsetattr: stdin");

+    exit (EXIT_FAILURE);

+  }

+}

+

+/* Restore the tty to (presumably) cooked mode as it was when

+ * the program was started.

+ */

+static void

+restore_tty (void)

+{

+  tcsetattr (STDIN_FILENO, TCSANOW, &old_termios);

+}

+

+/* When we get SIGTSTP, switch back to cooked mode. */

+static void

+tstp_handler (int sig)

+{

+  restore_tty ();

+  signal (SIGTSTP, SIG_DFL);

+  raise (SIGTSTP);

+}

+

+/* When we get SIGCONF, switch to raw mode. */

+static void

+cont_handler (int sig)

+{

+  raw_tty ();

+}

+

 static void suggest_filesystems (void);

 static int

-- 

2.14.3