New APIs: set-pgroup, get-pgroup

If the pgroup flag is set in the handle, then the qemu and recovery
subprocesses are placed in separate process groups.  The default is
false.

The purpose for setting up a process group is that ^C will not be
passed from the main process down to these processes (killing them).
This allows ^C and other keyboard events to be caught and handled in
the main process.

4 files changed, 45 insertions, 6 deletions

diff --git a/generator/generator_actions.ml b/generator/generator_actions.ml
index 1ccacdb8..87c934aa 100644
--- a/generator/generator_actions.ml
+++ b/generator/generator_actions.ml
@@ -1526,6 +1526,25 @@ advice before using trademarks in applications.
 
 =back");
 
+  ("set_pgroup", (RErr, [Bool "pgroup"], []), -1, [FishAlias "pgroup"],
+   [],
+   "set process group flag",
+   "\
+If C<pgroup> is true, child processes are placed into
+their own process group.
+
+The practical upshot of this is that signals like C<SIGINT> (from
+users pressing C<^C>) won't be received by the child process.
+
+The default for this flag is false, because usually you want
+C<^C> to kill the subprocess.");
+
+  ("get_pgroup", (RBool "pgroup", [], []), -1, [],
+   [],
+   "get process group flag",
+   "\
+This returns the process group flag.");
+
 ]
 
 (* daemon_functions are any functions which cause some action
diff --git a/src/guestfs-internal.h b/src/guestfs-internal.h
index 96f81525..e2ffdf30 100644
--- a/src/guestfs-internal.h
+++ b/src/guestfs-internal.h
@@ -170,6 +170,8 @@ struct guestfs_h
 
   int selinux;                  /* selinux enabled? */
 
+  int pgroup;                   /* Create process group for children? */
+
   char *last_error;
   int last_errnum;              /* errno, or 0 if there was no errno */
 
diff --git a/src/guestfs.c b/src/guestfs.c
index b02bdb9d..e2b71594 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -801,6 +801,19 @@ guestfs__get_attach_method (guestfs_h *g)
   return ret;
 }
 
+int
+guestfs__set_pgroup (guestfs_h *g, int v)
+{
+  g->pgroup = !!v;
+  return 0;
+}
+
+int
+guestfs__get_pgroup (guestfs_h *g)
+{
+  return g->pgroup;
+}
+
 /* Note the private data area is allocated lazily, since the vast
  * majority of callers will never use it.  This means g->pda is
  * likely to be NULL.
diff --git a/src/launch.c b/src/launch.c
index 0b15ce98..1a47363d 100644
--- a/src/launch.c
+++ b/src/launch.c
@@ -643,12 +643,9 @@ launch_appliance (guestfs_h *g)
       close (rfd[1]);
     }
 
-#if 0
-    /* Set up a new process group, so we can signal this process
-     * and all subprocesses (eg. if qemu is really a shell script).
-     */
-    setpgid (0, 0);
-#endif
+    /* Put qemu in a new process group. */
+    if (g->pgroup)
+      setpgid (0, 0);
 
     setenv ("LC_ALL", "C", 1);
 
@@ -677,6 +674,14 @@ launch_appliance (guestfs_h *g)
       pid_t qemu_pid = g->pid;
       pid_t parent_pid = getppid ();
 
+      /* 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://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/ps_status.c?rev=1.33.2.1;content-type=text%2Fplain
        */