lib: Split launch.c into separate files.

launch-appliance.c contains the code associated with the 'appliance'
attach-method.  Mostly.  In fact there are a few APIs which don't fit
so nicely:

 - config: deprecated API which fiddles with the qemu command
   line directly

 - max-disks: depends on the qemu implementation (virtio-scsi
   or not)

 - debug-drives: used for testing only

launch-unix.c contains the code associated with 'unix:<path>'.

launch.c is the common code for launching, along with a few other APIs
such as guestfs_add_drive_opts.

This commit also reduces the number of headers to just those
which are required.

1 files changed, 1164 insertions, 0 deletions

diff --git a/src/launch-appliance.c b/src/launch-appliance.c
new file mode 100644
index 00000000..9c950073
--- /dev/null
+++ b/src/launch-appliance.c
@@ -0,0 +1,1164 @@
+/* libguestfs
+ * Copyright (C) 2009-2012 Red Hat Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <signal.h>
+
+#include "glthread/lock.h"
+
+#include "guestfs.h"
+#include "guestfs-internal.h"
+#include "guestfs-internal-actions.h"
+#include "guestfs_protocol.h"
+
+static int is_openable (guestfs_h *g, const char *path, int flags);
+static int64_t timeval_diff (const struct timeval *x, const struct timeval *y);
+static void print_qemu_command_line (guestfs_h *g, char **argv);
+static int qemu_supports (guestfs_h *g, const char *option);
+static int qemu_supports_device (guestfs_h *g, const char *device_name);
+static int qemu_supports_virtio_scsi (guestfs_h *g);
+static char *qemu_drive_param (guestfs_h *g, const struct drive *drv, size_t index);
+static char *drive_name (size_t index, char *ret);
+
+#if 0
+static int qemu_supports_re (guestfs_h *g, const pcre *option_regex);
+
+static void compile_regexps (void) __attribute__((constructor));
+static void free_regexps (void) __attribute__((destructor));
+
+static void
+compile_regexps (void)
+{
+  const char *err;
+  int offset;
+
+#define COMPILE(re,pattern,options)                                     \
+  do {                                                                  \
+    re = pcre_compile ((pattern), (options), &err, &offset, NULL);      \
+    if (re == NULL) {                                                   \
+      ignore_value (write (2, err, strlen (err)));                      \
+      abort ();                                                         \
+    }                                                                   \
+  } while (0)
+}
+
+static void
+free_regexps (void)
+{
+}
+#endif
+
+/* Functions to add a string to the current command line. */
+static void
+alloc_cmdline (guestfs_h *g)
+{
+  if (g->cmdline == NULL) {
+    /* g->cmdline[0] is reserved for argv[0], set in guestfs_launch. */
+    g->cmdline_size = 1;
+    g->cmdline = safe_malloc (g, sizeof (char *));
+    g->cmdline[0] = NULL;
+  }
+}
+
+static void
+incr_cmdline_size (guestfs_h *g)
+{
+  alloc_cmdline (g);
+  g->cmdline_size++;
+  g->cmdline = safe_realloc (g, g->cmdline, sizeof (char *) * g->cmdline_size);
+}
+
+static int
+add_cmdline (guestfs_h *g, const char *str)
+{
+  if (g->state != CONFIG) {
+    error (g,
+        _("command line cannot be altered after qemu subprocess launched"));
+    return -1;
+  }
+
+  incr_cmdline_size (g);
+  g->cmdline[g->cmdline_size-1] = safe_strdup (g, str);
+  return 0;
+}
+
+/* Like 'add_cmdline' but allowing a shell-quoted string of zero or
+ * more options.  XXX The unquoting is not very clever.
+ */
+static int
+add_cmdline_shell_unquoted (guestfs_h *g, const char *options)
+{
+  char quote;
+  const char *startp, *endp, *nextp;
+
+  if (g->state != CONFIG) {
+    error (g,
+        _("command line cannot be altered after qemu subprocess launched"));
+    return -1;
+  }
+
+  while (*options) {
+    quote = *options;
+    if (quote == '\'' || quote == '"')
+      startp = options+1;
+    else {
+      startp = options;
+      quote = ' ';
+    }
+
+    endp = strchr (options, quote);
+    if (endp == NULL) {
+      if (quote != ' ') {
+        error (g, _("unclosed quote character (%c) in command line near: %s"),
+               quote, options);
+        return -1;
+      }
+      endp = options + strlen (options);
+    }
+
+    if (quote == ' ')
+      nextp = endp+1;
+    else {
+      if (!endp[1])
+        nextp = endp+1;
+      else if (endp[1] == ' ')
+        nextp = endp+2;
+      else {
+        error (g, _("cannot parse quoted string near: %s"), options);
+        return -1;
+      }
+    }
+    while (*nextp && *nextp == ' ')
+      nextp++;
+
+    incr_cmdline_size (g);
+    g->cmdline[g->cmdline_size-1] = safe_strndup (g, startp, endp-startp);
+
+    options = nextp;
+  }
+
+  return 0;
+}
+
+/* RHBZ#790721: It makes no sense to have multiple threads racing to
+ * build the appliance from within a single process, and the code
+ * isn't safe for that anyway.  Therefore put a thread lock around
+ * appliance building.
+ */
+gl_lock_define_initialized (static, building_lock);
+
+int
+guestfs___launch_appliance (guestfs_h *g)
+{
+  int r;
+  int wfd[2], rfd[2];
+  char guestfsd_sock[256];
+  struct sockaddr_un addr;
+
+  /* At present you must add drives before starting the appliance.  In
+   * future when we enable hotplugging you won't need to do this.
+   */
+  if (!g->drives) {
+    error (g, _("you must call guestfs_add_drive before guestfs_launch"));
+    return -1;
+  }
+
+  /* Start the clock ... */
+  gettimeofday (&g->launch_t, NULL);
+  guestfs___launch_send_progress (g, 0);
+
+  TRACE0 (launch_build_appliance_start);
+
+  /* Locate and/or build the appliance. */
+  char *kernel = NULL, *initrd = NULL, *appliance = NULL;
+  gl_lock_lock (building_lock);
+  if (guestfs___build_appliance (g, &kernel, &initrd, &appliance) == -1) {
+    gl_lock_unlock (building_lock);
+    return -1;
+  }
+  gl_lock_unlock (building_lock);
+
+  TRACE0 (launch_build_appliance_end);
+
+  guestfs___launch_send_progress (g, 3);
+
+  if (g->verbose)
+    guestfs___print_timestamped_message (g, "begin testing qemu features");
+
+  /* Get qemu help text and version. */
+  if (qemu_supports (g, NULL) == -1)
+    goto cleanup0;
+
+  /* Using virtio-serial, we need to create a local Unix domain socket
+   * for qemu to connect to.
+   */
+  snprintf (guestfsd_sock, sizeof guestfsd_sock, "%s/guestfsd.sock", g->tmpdir);
+  unlink (guestfsd_sock);
+
+  g->sock = socket (AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
+  if (g->sock == -1) {
+    perrorf (g, "socket");
+    goto cleanup0;
+  }
+
+  if (fcntl (g->sock, F_SETFL, O_NONBLOCK) == -1) {
+    perrorf (g, "fcntl");
+    goto cleanup0;
+  }
+
+  addr.sun_family = AF_UNIX;
+  strncpy (addr.sun_path, guestfsd_sock, UNIX_PATH_MAX);
+  addr.sun_path[UNIX_PATH_MAX-1] = '\0';
+
+  if (bind (g->sock, &addr, sizeof addr) == -1) {
+    perrorf (g, "bind");
+    goto cleanup0;
+  }
+
+  if (listen (g->sock, 1) == -1) {
+    perrorf (g, "listen");
+    goto cleanup0;
+  }
+
+  if (!g->direct) {
+    if (pipe (wfd) == -1 || pipe (rfd) == -1) {
+      perrorf (g, "pipe");
+      goto cleanup0;
+    }
+  }
+
+  if (g->verbose)
+    guestfs___print_timestamped_message (g, "finished testing qemu features");
+
+  r = fork ();
+  if (r == -1) {
+    perrorf (g, "fork");
+    if (!g->direct) {
+      close (wfd[0]);
+      close (wfd[1]);
+      close (rfd[0]);
+      close (rfd[1]);
+    }
+    goto cleanup0;
+  }
+
+  if (r == 0) {			/* Child (qemu). */
+    char buf[256];
+    int virtio_scsi = qemu_supports_virtio_scsi (g);
+
+    /* Set up the full command line.  Do this in the subprocess so we
+     * don't need to worry about cleaning up.
+     */
+
+    /* Set g->cmdline[0] to the name of the qemu process.  However
+     * it is possible that no g->cmdline has been allocated yet so
+     * we must do that first.
+     */
+    alloc_cmdline (g);
+    g->cmdline[0] = g->qemu;
+
+    /* CVE-2011-4127 mitigation: Disable SCSI ioctls on virtio-blk
+     * devices.  The -global option must exist, but you can pass any
+     * strings to it so we don't need to check for the specific virtio
+     * feature.
+     */
+    if (qemu_supports (g, "-global")) {
+      add_cmdline (g, "-global");
+      add_cmdline (g, "virtio-blk-pci.scsi=off");
+    }
+
+    if (qemu_supports (g, "-nodefconfig"))
+      add_cmdline (g, "-nodefconfig");
+
+    /* Newer versions of qemu (from around 2009/12) changed the
+     * behaviour of monitors so that an implicit '-monitor stdio' is
+     * assumed if we are in -nographic mode and there is no other
+     * -monitor option.  Only a single stdio device is allowed, so
+     * this broke the '-serial stdio' option.  There is a new flag
+     * called -nodefaults which gets rid of all this default crud, so
+     * let's use that to avoid this and any future surprises.
+     */
+    if (qemu_supports (g, "-nodefaults"))
+      add_cmdline (g, "-nodefaults");
+
+    add_cmdline (g, "-nographic");
+
+    /* Add drives */
+    struct drive *drv = g->drives;
+    size_t drv_index = 0;
+
+    if (virtio_scsi) {
+      /* Create the virtio-scsi bus. */
+      add_cmdline (g, "-device");
+      add_cmdline (g, "virtio-scsi-pci,id=scsi");
+    }
+
+    while (drv != NULL) {
+      /* Construct the final -drive parameter. */
+      char *buf = qemu_drive_param (g, drv, drv_index);
+
+      add_cmdline (g, "-drive");
+      add_cmdline (g, buf);
+      free (buf);
+
+      if (virtio_scsi && drv->iface == NULL) {
+        char buf2[64];
+        snprintf (buf2, sizeof buf2, "scsi-hd,drive=hd%zu", drv_index);
+        add_cmdline (g, "-device");
+        add_cmdline (g, buf2);
+      }
+
+      drv = drv->next;
+      drv_index++;
+    }
+
+    char appliance_root[64] = "";
+
+    /* Add the ext2 appliance drive (after all the drives). */
+    if (appliance) {
+      const char *cachemode = "";
+      if (qemu_supports (g, "cache=")) {
+        if (qemu_supports (g, "unsafe"))
+          cachemode = ",cache=unsafe";
+        else if (qemu_supports (g, "writeback"))
+          cachemode = ",cache=writeback";
+      }
+
+      char buf2[PATH_MAX + 64];
+      add_cmdline (g, "-drive");
+      snprintf (buf2, sizeof buf2, "file=%s,snapshot=on,id=appliance,if=%s%s",
+                appliance, virtio_scsi ? "none" : "virtio", cachemode);
+      add_cmdline (g, buf2);
+
+      if (virtio_scsi) {
+        add_cmdline (g, "-device");
+        add_cmdline (g, "scsi-hd,drive=appliance");
+      }
+
+      snprintf (appliance_root, sizeof appliance_root, "root=/dev/%cd",
+                virtio_scsi ? 's' : 'v');
+      drive_name (drv_index, &appliance_root[12]);
+    }
+
+    if (STRNEQ (QEMU_OPTIONS, "")) {
+      /* Add the extra options for the qemu command line specified
+       * at configure time.
+       */
+      add_cmdline_shell_unquoted (g, QEMU_OPTIONS);
+    }
+
+    /* The qemu -machine option (added 2010-12) is a bit more sane
+     * since it falls back through various different acceleration
+     * modes, so try that first (thanks Markus Armbruster).
+     */
+    if (qemu_supports (g, "-machine")) {
+      add_cmdline (g, "-machine");
+      add_cmdline (g, "accel=kvm:tcg");
+    } else {
+      /* qemu sometimes needs this option to enable hardware
+       * virtualization, but some versions of 'qemu-kvm' will use KVM
+       * regardless (even where this option appears in the help text).
+       * It is rumoured that there are versions of qemu where supplying
+       * this option when hardware virtualization is not available will
+       * cause qemu to fail, so we we have to check at least that
+       * /dev/kvm is openable.  That's not reliable, since /dev/kvm
+       * might be openable by qemu but not by us (think: SELinux) in
+       * which case the user would not get hardware virtualization,
+       * although at least shouldn't fail.  A giant clusterfuck with the
+       * qemu command line, again.
+       */
+      if (qemu_supports (g, "-enable-kvm") &&
+          is_openable (g, "/dev/kvm", O_RDWR|O_CLOEXEC))
+        add_cmdline (g, "-enable-kvm");
+    }
+
+    if (g->smp > 1) {
+      snprintf (buf, sizeof buf, "%d", g->smp);
+      add_cmdline (g, "-smp");
+      add_cmdline (g, buf);
+    }
+
+    snprintf (buf, sizeof buf, "%d", g->memsize);
+    add_cmdline (g, "-m");
+    add_cmdline (g, buf);
+
+    /* Force exit instead of reboot on panic */
+    add_cmdline (g, "-no-reboot");
+
+    /* These options recommended by KVM developers to improve reliability. */
+#ifndef __arm__
+    /* qemu-system-arm advertises the -no-hpet option but if you try
+     * to use it, it usefully says:
+     *   "Option no-hpet not supported for this target".
+     * Cheers qemu developers.  How many years have we been asking for
+     * capabilities?  Could be 3 or 4 years, I forget.
+     */
+    if (qemu_supports (g, "-no-hpet"))
+      add_cmdline (g, "-no-hpet");
+#endif
+
+    if (qemu_supports (g, "-rtc-td-hack"))
+      add_cmdline (g, "-rtc-td-hack");
+
+    /* Create the virtio serial bus. */
+    add_cmdline (g, "-device");
+    add_cmdline (g, "virtio-serial");
+
+#if 0
+    /* Use virtio-console (a variant form of virtio-serial) for the
+     * guest's serial console.
+     */
+    add_cmdline (g, "-chardev");
+    add_cmdline (g, "stdio,id=console");
+    add_cmdline (g, "-device");
+    add_cmdline (g, "virtconsole,chardev=console,name=org.libguestfs.console.0");
+#else
+    /* When the above works ...  until then: */
+    add_cmdline (g, "-serial");
+    add_cmdline (g, "stdio");
+#endif
+
+    /* Use sgabios instead of vgabios.  This means we'll see BIOS
+     * messages on the serial port, and also works around this bug
+     * in qemu 1.1.0:
+     * https://bugs.launchpad.net/qemu/+bug/1021649
+     * QEmu has included sgabios upstream since just before 1.0.
+     */
+    add_cmdline (g, "-device");
+    add_cmdline (g, "sga");
+
+    /* Set up virtio-serial for the communications channel. */
+    add_cmdline (g, "-chardev");
+    snprintf (buf, sizeof buf, "socket,path=%s,id=channel0", guestfsd_sock);
+    add_cmdline (g, buf);
+    add_cmdline (g, "-device");
+    add_cmdline (g, "virtserialport,chardev=channel0,name=org.libguestfs.channel.0");
+
+#ifdef VALGRIND_DAEMON
+    /* Set up virtio-serial channel for valgrind messages. */
+    add_cmdline (g, "-chardev");
+    snprintf (buf, sizeof buf, "file,path=%s/valgrind.log.%d,id=valgrind",
+              VALGRIND_LOG_PATH, getpid ());
+    add_cmdline (g, buf);
+    add_cmdline (g, "-device");
+    add_cmdline (g, "virtserialport,chardev=valgrind,name=org.libguestfs.valgrind");
+#endif
+
+    /* Enable user networking. */
+    if (g->enable_network) {
+      add_cmdline (g, "-netdev");
+      add_cmdline (g, "user,id=usernet,net=169.254.0.0/16");
+      add_cmdline (g, "-device");
+      add_cmdline (g, "virtio-net-pci,netdev=usernet");
+    }
+
+#if defined(__arm__)
+#define SERIAL_CONSOLE "ttyAMA0"
+#else
+#define SERIAL_CONSOLE "ttyS0"
+#endif
+
+#define LINUX_CMDLINE							\
+    "panic=1 "         /* force kernel to panic if daemon exits */	\
+    "console=" SERIAL_CONSOLE " " /* serial console */		        \
+    "udevtimeout=600 " /* good for very slow systems (RHBZ#480319) */	\
+    "no_timer_check "  /* fix for RHBZ#502058 */                        \
+    "acpi=off "        /* we don't need ACPI, turn it off */		\
+    "printk.time=1 "   /* display timestamp before kernel messages */   \
+    "cgroup_disable=memory " /* saves us about 5 MB of RAM */
+
+    /* Linux kernel command line. */
+    snprintf (buf, sizeof buf,
+              LINUX_CMDLINE
+              "%s "             /* (root) */
+              "%s "             /* (selinux) */
+              "%s "             /* (verbose) */
+              "TERM=%s "        /* (TERM environment variable) */
+              "%s",             /* (append) */
+              appliance_root,
+              g->selinux ? "selinux=1 enforcing=0" : "selinux=0",
+              g->verbose ? "guestfs_verbose=1" : "",
+              getenv ("TERM") ? : "linux",
+              g->append ? g->append : "");
+
+    add_cmdline (g, "-kernel");
+    add_cmdline (g, kernel);
+    add_cmdline (g, "-initrd");
+    add_cmdline (g, initrd);
+    add_cmdline (g, "-append");
+    add_cmdline (g, buf);
+
+    /* Finish off the command line. */
+    incr_cmdline_size (g);
+    g->cmdline[g->cmdline_size-1] = NULL;
+
+    if (!g->direct) {
+      /* Set up stdin, stdout, stderr. */
+      close (0);
+      close (1);
+      close (wfd[1]);
+      close (rfd[0]);
+
+      /* Stdin. */
+      if (dup (wfd[0]) == -1) {
+      dup_failed:
+        perror ("dup failed");
+        _exit (EXIT_FAILURE);
+      }
+      /* Stdout. */
+      if (dup (rfd[1]) == -1)
+        goto dup_failed;
+
+      /* Particularly since qemu 0.15, qemu spews all sorts of debug
+       * information on stderr.  It is useful to both capture this and
+       * not confuse casual users, so send stderr to the pipe as well.
+       */
+      close (2);
+      if (dup (rfd[1]) == -1)
+        goto dup_failed;
+
+      close (wfd[0]);
+      close (rfd[1]);
+    }
+
+    /* Dump the command line (after setting up stderr above). */
+    if (g->verbose)
+      print_qemu_command_line (g, g->cmdline);
+
+    /* Put qemu in a new process group. */
+    if (g->pgroup)
+      setpgid (0, 0);
+
+    setenv ("LC_ALL", "C", 1);
+
+    TRACE0 (launch_run_qemu);
+
+    execv (g->qemu, g->cmdline); /* Run qemu. */
+    perror (g->qemu);
+    _exit (EXIT_FAILURE);
+  }
+
+  /* Parent (library). */
+  g->pid = r;
+
+  free (kernel);
+  kernel = NULL;
+  free (initrd);
+  initrd = NULL;
+  free (appliance);
+  appliance = NULL;
+
+  /* Fork the recovery process off which will kill qemu if the parent
+   * process fails to do so (eg. if the parent segfaults).
+   */
+  g->recoverypid = -1;
+  if (g->recovery_proc) {
+    r = fork ();
+    if (r == 0) {
+      int i, fd, max_fd;
+      struct sigaction sa;
+      pid_t qemu_pid = g->pid;
+      pid_t parent_pid = getppid ();
+
+      /* Remove all signal handlers.  See the justification here:
+       * https://www.redhat.com/archives/libvir-list/2008-August/msg00303.html
+       * We don't mask signal handlers yet, so this isn't completely
+       * race-free, but better than not doing it at all.
+       */
+      memset (&sa, 0, sizeof sa);
+      sa.sa_handler = SIG_DFL;
+      sa.sa_flags = 0;
+      sigemptyset (&sa.sa_mask);
+      for (i = 1; i < NSIG; ++i)
+        sigaction (i, &sa, NULL);
+
+      /* Close all other file descriptors.  This ensures that we don't
+       * hold open (eg) pipes from the parent process.
+       */
+      max_fd = sysconf (_SC_OPEN_MAX);
+      if (max_fd == -1)
+        max_fd = 1024;
+      if (max_fd > 65536)
+        max_fd = 65536; /* bound the amount of work we do here */
+      for (fd = 0; fd < max_fd; ++fd)
+        close (fd);
+
+      /* It would be nice to be able to put this in the same process
+       * group as qemu (ie. setpgid (0, qemu_pid)).  However this is
+       * not possible because we don't have any guarantee here that
+       * the qemu process has started yet.
+       */
+      if (g->pgroup)
+        setpgid (0, 0);
+
+      /* Writing to argv is hideously complicated and error prone.  See:
+       * http://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/utils/misc/ps_status.c;hb=HEAD
+       */
+
+      /* Loop around waiting for one or both of the other processes to
+       * disappear.  It's fair to say this is very hairy.  The PIDs that
+       * we are looking at might be reused by another process.  We are
+       * effectively polling.  Is the cure worse than the disease?
+       */
+      for (;;) {
+        if (kill (qemu_pid, 0) == -1) /* qemu's gone away, we aren't needed */
+          _exit (EXIT_SUCCESS);
+        if (kill (parent_pid, 0) == -1) {
+          /* Parent's gone away, qemu still around, so kill qemu. */
+          kill (qemu_pid, 9);
+          _exit (EXIT_SUCCESS);
+        }
+        sleep (2);
+      }
+    }
+
+    /* Don't worry, if the fork failed, this will be -1.  The recovery
+     * process isn't essential.
+     */
+    g->recoverypid = r;
+  }
+
+  if (!g->direct) {
+    /* Close the other ends of the pipe. */
+    close (wfd[0]);
+    close (rfd[1]);
+
+    if (fcntl (wfd[1], F_SETFL, O_NONBLOCK) == -1 ||
+        fcntl (rfd[0], F_SETFL, O_NONBLOCK) == -1) {
+      perrorf (g, "fcntl");
+      goto cleanup1;
+    }
+
+    g->fd[0] = wfd[1];		/* stdin of child */
+    g->fd[1] = rfd[0];		/* stdout of child */
+    wfd[1] = rfd[0] = -1;
+  } else {
+    g->fd[0] = open ("/dev/null", O_RDWR|O_CLOEXEC);
+    if (g->fd[0] == -1) {
+      perrorf (g, "open /dev/null");
+      goto cleanup1;
+    }
+    g->fd[1] = dup (g->fd[0]);
+    if (g->fd[1] == -1) {
+      perrorf (g, "dup");
+      close (g->fd[0]);
+      g->fd[0] = -1;
+      goto cleanup1;
+    }
+  }
+
+  g->state = LAUNCHING;
+
+  /* Wait for qemu to start and to connect back to us via
+   * virtio-serial and send the GUESTFS_LAUNCH_FLAG message.
+   */
+  r = guestfs___accept_from_daemon (g);
+  if (r == -1)
+    goto cleanup1;
+
+  /* NB: We reach here just because qemu has opened the socket.  It
+   * does not mean the daemon is up until we read the
+   * GUESTFS_LAUNCH_FLAG below.  Failures in qemu startup can still
+   * happen even if we reach here, even early failures like not being
+   * able to open a drive.
+   */
+
+  /* Close the listening socket. */
+  if (close (g->sock) != 0) {
+    perrorf (g, "close: listening socket");
+    close (r);
+    g->sock = -1;
+    goto cleanup1;
+  }
+  g->sock = r; /* This is the accepted data socket. */
+
+  if (fcntl (g->sock, F_SETFL, O_NONBLOCK) == -1) {
+    perrorf (g, "fcntl");
+    goto cleanup1;
+  }
+
+  uint32_t size;
+  void *buf = NULL;
+  r = guestfs___recv_from_daemon (g, &size, &buf);
+  free (buf);
+
+  if (r == -1) {
+    error (g, _("guestfs_launch failed, see earlier error messages"));
+    goto cleanup1;
+  }
+
+  if (size != GUESTFS_LAUNCH_FLAG) {
+    error (g, _("guestfs_launch failed, see earlier error messages"));
+    goto cleanup1;
+  }
+
+  if (g->verbose)
+    guestfs___print_timestamped_message (g, "appliance is up");
+
+  /* This is possible in some really strange situations, such as
+   * guestfsd starts up OK but then qemu immediately exits.  Check for
+   * it because the caller is probably expecting to be able to send
+   * commands after this function returns.
+   */
+  if (g->state != READY) {
+    error (g, _("qemu launched and contacted daemon, but state != READY"));
+    goto cleanup1;
+  }
+
+  TRACE0 (launch_end);
+
+  guestfs___launch_send_progress (g, 12);
+
+  return 0;
+
+ cleanup1:
+  if (!g->direct) {
+    if (wfd[1] >= 0) close (wfd[1]);
+    if (rfd[1] >= 0) close (rfd[0]);
+  }
+  if (g->pid > 0) kill (g->pid, 9);
+  if (g->recoverypid > 0) kill (g->recoverypid, 9);
+  if (g->pid > 0) waitpid (g->pid, NULL, 0);
+  if (g->recoverypid > 0) waitpid (g->recoverypid, NULL, 0);
+  if (g->fd[0] >= 0) close (g->fd[0]);
+  if (g->fd[1] >= 0) close (g->fd[1]);
+  g->fd[0] = -1;
+  g->fd[1] = -1;
+  g->pid = 0;
+  g->recoverypid = 0;
+  memset (&g->launch_t, 0, sizeof g->launch_t);
+
+ cleanup0:
+  if (g->sock >= 0) {
+    close (g->sock);
+    g->sock = -1;
+  }
+  g->state = CONFIG;
+  free (kernel);
+  free (initrd);
+  free (appliance);
+  return -1;
+}
+
+/* launch (of the appliance) generates approximate progress
+ * messages.  Currently these are defined as follows:
+ *
+ *    0 / 12: launch clock starts
+ *    3 / 12: appliance created
+ *    6 / 12: detected that guest kernel started
+ *    9 / 12: detected that /init script is running
+ *   12 / 12: launch completed successfully
+ *
+ * Notes:
+ * (1) This is not a documented ABI and the behaviour may be changed
+ * or removed in future.
+ * (2) Messages are only sent if more than 5 seconds has elapsed
+ * since the launch clock started.
+ * (3) There is a gross hack in proto.c to make this work.
+ */
+void
+guestfs___launch_send_progress (guestfs_h *g, int perdozen)
+{
+  struct timeval tv;
+
+  gettimeofday (&tv, NULL);
+  if (timeval_diff (&g->launch_t, &tv) >= 5000) {
+    guestfs_progress progress_message =
+      { .proc = 0, .serial = 0, .position = perdozen, .total = 12 };
+
+    guestfs___progress_message_callback (g, &progress_message);
+  }
+}
+
+/* Compute Y - X and return the result in milliseconds.
+ * Approximately the same as this code:
+ * http://www.mpp.mpg.de/~huber/util/timevaldiff.c
+ */
+static int64_t
+timeval_diff (const struct timeval *x, const struct timeval *y)
+{
+  int64_t msec;
+
+  msec = (y->tv_sec - x->tv_sec) * 1000;
+  msec += (y->tv_usec - x->tv_usec) / 1000;
+  return msec;
+}
+
+/* Note that since this calls 'debug' it should only be called
+ * from the parent process.
+ */
+void
+guestfs___print_timestamped_message (guestfs_h *g, const char *fs, ...)
+{
+  va_list args;
+  char *msg;
+  int err;
+  struct timeval tv;
+
+  va_start (args, fs);
+  err = vasprintf (&msg, fs, args);
+  va_end (args);
+
+  if (err < 0) return;
+
+  gettimeofday (&tv, NULL);
+
+  debug (g, "[%05" PRIi64 "ms] %s", timeval_diff (&g->launch_t, &tv), msg);
+
+  free (msg);
+}
+
+/* This is called from the forked subprocess just before qemu runs, so
+ * it can just print the message straight to stderr, where it will be
+ * picked up and funnelled through the usual appliance event API.
+ */
+static void
+print_qemu_command_line (guestfs_h *g, char **argv)
+{
+  int i = 0;
+  int needs_quote;
+
+  struct timeval tv;
+  gettimeofday (&tv, NULL);
+  fprintf (stderr, "[%05" PRIi64 "ms] ", timeval_diff (&g->launch_t, &tv));
+
+  while (argv[i]) {
+    if (argv[i][0] == '-') /* -option starts a new line */
+      fprintf (stderr, " \\\n   ");
+
+    if (i > 0) fputc (' ', stderr);
+
+    /* Does it need shell quoting?  This only deals with simple cases. */
+    needs_quote = strcspn (argv[i], " ") != strlen (argv[i]);
+
+    if (needs_quote) fputc ('\'', stderr);
+    fprintf (stderr, "%s", argv[i]);
+    if (needs_quote) fputc ('\'', stderr);
+    i++;
+  }
+}
+
+static int test_qemu_cmd (guestfs_h *g, const char *cmd, char **ret);
+static int read_all (guestfs_h *g, FILE *fp, char **ret);
+
+/* Test qemu binary (or wrapper) runs, and do 'qemu -help' and
+ * 'qemu -version' so we know what options this qemu supports and
+ * the version.
+ */
+static int
+test_qemu (guestfs_h *g)
+{
+  char cmd[1024];
+
+  free (g->qemu_help);
+  g->qemu_help = NULL;
+  free (g->qemu_version);
+  g->qemu_version = NULL;
+  free (g->qemu_devices);
+  g->qemu_devices = NULL;
+
+  snprintf (cmd, sizeof cmd, "LC_ALL=C '%s' -nographic -help", g->qemu);
+
+  /* If this command doesn't work then it probably indicates that the
+   * qemu binary is missing.
+   */
+  if (test_qemu_cmd (g, cmd, &g->qemu_help) == -1) {
+  qemu_error:
+    error (g, _("command failed: %s\nerrno: %s\n\nIf qemu is located on a non-standard path, try setting the LIBGUESTFS_QEMU\nenvironment variable.  There may also be errors printed above."),
+           cmd, strerror (errno));
+    return -1;
+  }
+
+  snprintf (cmd, sizeof cmd, "LC_ALL=C '%s' -nographic -version 2>/dev/null",
+            g->qemu);
+
+  if (test_qemu_cmd (g, cmd, &g->qemu_version) == -1)
+    goto qemu_error;
+
+  snprintf (cmd, sizeof cmd,
+            "LC_ALL=C '%s' -nographic -machine accel=kvm:tcg -device '?' 2>&1",
+            g->qemu);
+
+  if (test_qemu_cmd (g, cmd, &g->qemu_devices) == -1)
+    goto qemu_error;
+
+  return 0;
+}
+
+static int
+test_qemu_cmd (guestfs_h *g, const char *cmd, char **ret)
+{
+  FILE *fp;
+
+  fp = popen (cmd, "r");
+  if (fp == NULL)
+    return -1;
+
+  if (read_all (g, fp, ret) == -1) {
+    pclose (fp);
+    return -1;
+  }
+
+  if (pclose (fp) != 0)
+    return -1;
+
+  return 0;
+}
+
+static int
+read_all (guestfs_h *g, FILE *fp, char **ret)
+{
+  int r, n = 0;
+  char *p;
+
+ again:
+  if (feof (fp)) {
+    *ret = safe_realloc (g, *ret, n + 1);
+    (*ret)[n] = '\0';
+    return n;
+  }
+
+  *ret = safe_realloc (g, *ret, n + BUFSIZ);
+  p = &(*ret)[n];
+  r = fread (p, 1, BUFSIZ, fp);
+  if (ferror (fp))
+    return -1;
+  n += r;
+  goto again;
+}
+
+/* Test if option is supported by qemu command line (just by grepping
+ * the help text).
+ *
+ * The first time this is used, it has to run the external qemu
+ * binary.  If that fails, it returns -1.
+ *
+ * To just do the first-time run of the qemu binary, call this with
+ * option == NULL, in which case it will return -1 if there was an
+ * error doing that.
+ */
+static int
+qemu_supports (guestfs_h *g, const char *option)
+{
+  if (!g->qemu_help) {
+    if (test_qemu (g) == -1)
+      return -1;
+  }
+
+  if (option == NULL)
+    return 1;
+
+  return strstr (g->qemu_help, option) != NULL;
+}
+
+#if 0
+/* As above but using a regex instead of a fixed string. */
+static int
+qemu_supports_re (guestfs_h *g, const pcre *option_regex)
+{
+  if (!g->qemu_help) {
+    if (test_qemu (g) == -1)
+      return -1;
+  }
+
+  return match (g, g->qemu_help, option_regex);
+}
+#endif
+
+/* Test if device is supported by qemu (currently just greps the -device ?
+ * output).
+ */
+static int
+qemu_supports_device (guestfs_h *g, const char *device_name)
+{
+  if (!g->qemu_devices) {
+    if (test_qemu (g) == -1)
+      return -1;
+  }
+
+  return strstr (g->qemu_devices, device_name) != NULL;
+}
+
+/* Check if a file can be opened. */
+static int
+is_openable (guestfs_h *g, const char *path, int flags)
+{
+  int fd = open (path, flags);
+  if (fd == -1) {
+    debug (g, "is_openable: %s: %m", path);
+    return 0;
+  }
+  close (fd);
+  return 1;
+}
+
+/* Returns 1 = use virtio-scsi, or 0 = use virtio-blk. */
+static int
+qemu_supports_virtio_scsi (guestfs_h *g)
+{
+  int r;
+
+  /* g->virtio_scsi has these values:
+   *   0 = untested (after handle creation)
+   *   1 = supported
+   *   2 = not supported (use virtio-blk)
+   *   3 = test failed (use virtio-blk)
+   */
+  if (g->virtio_scsi == 0) {
+    r = qemu_supports_device (g, "virtio-scsi-pci");
+    if (r > 0)
+      g->virtio_scsi = 1;
+    else if (r == 0)
+      g->virtio_scsi = 2;
+    else
+      g->virtio_scsi = 3;
+  }
+
+  return g->virtio_scsi == 1;
+}
+
+static char *
+qemu_drive_param (guestfs_h *g, const struct drive *drv, size_t index)
+{
+  size_t i;
+  size_t len = 128;
+  const char *p;
+  char *r;
+  const char *iface;
+
+  len += strlen (drv->path) * 2; /* every "," could become ",," */
+  if (drv->iface)
+    len += strlen (drv->iface);
+  if (drv->format)
+    len += strlen (drv->format);
+
+  r = safe_malloc (g, len);
+
+  strcpy (r, "file=");
+  i = 5;
+
+  /* Copy the path in, escaping any "," as ",,". */
+  for (p = drv->path; *p; p++) {
+    if (*p == ',') {
+      r[i++] = ',';
+      r[i++] = ',';
+    } else
+      r[i++] = *p;
+  }
+
+  if (drv->iface)
+    iface = drv->iface;
+  else if (qemu_supports_virtio_scsi (g))
+    iface = "none"; /* sic */
+  else
+    iface = "virtio";
+
+  snprintf (&r[i], len-i, "%s%s%s%s,id=hd%zu,if=%s",
+            drv->readonly ? ",snapshot=on" : "",
+            drv->use_cache_none ? ",cache=none" : "",
+            drv->format ? ",format=" : "",
+            drv->format ? drv->format : "",
+            index,
+            iface);
+
+  return r;                     /* caller frees */
+}
+
+/* https://rwmj.wordpress.com/2011/01/09/how-are-linux-drives-named-beyond-drive-26-devsdz/ */
+static char *
+drive_name (size_t index, char *ret)
+{
+  if (index >= 26)
+    ret = drive_name (index/26 - 1, ret);
+  index %= 26;
+  *ret++ = 'a' + index;
+  *ret = '\0';
+  return ret;
+}
+
+/* Internal command to return the list of drives. */
+char **
+guestfs__debug_drives (guestfs_h *g)
+{
+  size_t i, count;
+  char **ret;
+  struct drive *drv;
+
+  for (count = 0, drv = g->drives; drv; count++, drv = drv->next)
+    ;
+
+  ret = safe_malloc (g, sizeof (char *) * (count + 1));
+
+  for (i = 0, drv = g->drives; drv; i++, drv = drv->next)
+    ret[i] = qemu_drive_param (g, drv, i);
+
+  ret[count] = NULL;
+
+  return ret;                   /* caller frees */
+}
+
+/* Maximum number of disks. */
+int
+guestfs__max_disks (guestfs_h *g)
+{
+  if (qemu_supports_virtio_scsi (g))
+    return 255;
+  else
+    return 27;                  /* conservative estimate */
+}
+
+int
+guestfs__config (guestfs_h *g,
+                 const char *qemu_param, const char *qemu_value)
+{
+  if (qemu_param[0] != '-') {
+    error (g, _("guestfs_config: parameter must begin with '-' character"));
+    return -1;
+  }
+
+  /* A bit fascist, but the user will probably break the extra
+   * parameters that we add if they try to set any of these.
+   */
+  if (STREQ (qemu_param, "-kernel") ||
+      STREQ (qemu_param, "-initrd") ||
+      STREQ (qemu_param, "-nographic") ||
+      STREQ (qemu_param, "-serial") ||
+      STREQ (qemu_param, "-full-screen") ||
+      STREQ (qemu_param, "-std-vga") ||
+      STREQ (qemu_param, "-vnc")) {
+    error (g, _("guestfs_config: parameter '%s' isn't allowed"), qemu_param);
+    return -1;
+  }
+
+  if (add_cmdline (g, qemu_param) != 0) return -1;
+
+  if (qemu_value != NULL) {
+    if (add_cmdline (g, qemu_value) != 0) return -1;
+  }
+
+  return 0;
+}