monitor: Use tee to save pcap stream

Previously, Bustle read directly from dbus-monitor, parsed the pcap
stream, then reserialized it back to a file.

    dbus-monitor → bustle → UI
                     ↓
                    file

Instead, use tee between dbus-monitor and Bustle to write the raw pcap
stream to disk:

    dbus-monitor → tee → bustle
                    ↓
                   file

This makes the code in Bustle quite a bit simpler.

1 files changed, 34 insertions, 43 deletions

diff --git a/c-sources/pcap-monitor.c b/c-sources/pcap-monitor.c
index cb1d272..9ecba12 100644
--- a/c-sources/pcap-monitor.c
+++ b/c-sources/pcap-monitor.c
@@ -101,13 +101,12 @@ typedef struct _BustlePcapMonitor {
     GSubprocess *dbus_monitor;
     /* If >= 0, master side of controlling terminal for dbus_monitor */
     int pt_master;
-    GSource *dbus_monitor_source;
+    GSubprocess *tee_proc;
+    GSource *tee_source;
     BustlePcapReader *reader;
 
     /* output */
     gchar *filename;
-    pcap_t *pcap_out;
-    pcap_dumper_t *dumper;
 
     /* errors */
     GError *pcap_error;
@@ -208,16 +207,6 @@ bustle_pcap_monitor_set_property (
 }
 
 static void
-close_dump (BustlePcapMonitor *self)
-{
-  if (self->dumper != NULL)
-    pcap_dump_flush (self->dumper);
-
-  g_clear_pointer (&self->dumper, pcap_dump_close);
-  g_clear_pointer (&self->pcap_out, pcap_close);
-}
-
-static void
 bustle_pcap_monitor_dispose (GObject *object)
 {
   BustlePcapMonitor *self = BUSTLE_PCAP_MONITOR (object);
@@ -231,12 +220,11 @@ bustle_pcap_monitor_dispose (GObject *object)
     }
 
   g_clear_object (&self->cancellable);
-  g_clear_pointer (&self->dbus_monitor_source, g_source_destroy);
+  g_clear_pointer (&self->tee_source, g_source_destroy);
+  g_clear_object (&self->tee_proc);
   g_clear_object (&self->reader);
   g_clear_object (&self->dbus_monitor);
 
-  close_dump (self);
-
   if (parent_class->dispose != NULL)
     parent_class->dispose (object);
 }
@@ -409,7 +397,6 @@ handle_error (BustlePcapMonitor *self)
     }
 
   self->state = STATE_STOPPED;
-  close_dump (self);
 
   g_debug ("%s: emitting ::stopped(%s, %d, %s)", G_STRFUNC,
            g_quark_to_string (error->domain), error->code, error->message);
@@ -657,7 +644,7 @@ start_pcap (
   gint stdout_fd = -1;
   FILE *dbus_monitor_filep = NULL;
 
-  stdout_pipe = g_subprocess_get_stdout_pipe (self->dbus_monitor);
+  stdout_pipe = g_subprocess_get_stdout_pipe (self->tee_proc);
   g_return_val_if_fail (stdout_pipe != NULL, FALSE);
 
   stdout_fd = g_unix_input_stream_get_fd (G_UNIX_INPUT_STREAM (stdout_pipe));
@@ -718,11 +705,6 @@ read_one (
       g_signal_emit (self, signals[SIG_MESSAGE_LOGGED], 0,
           hdr->ts.tv_sec, hdr->ts.tv_usec, blob, hdr->caplen, message);
 
-      /* cast necessary because pcap_dump has a type matching the callback
-       * argument to pcap_loop()
-       * TODO don't block
-       */
-      pcap_dump ((u_char *) self->dumper, hdr, blob);
       return TRUE;
     }
 }
@@ -924,6 +906,27 @@ spawn_monitor (BustlePcapMonitor *self,
   return child;
 }
 
+static GSubprocess *
+spawn_tee (BustlePcapMonitor  *self,
+           GError            **error)
+{
+  g_autoptr(GSubprocessLauncher) launcher =
+    g_subprocess_launcher_new (G_SUBPROCESS_FLAGS_STDOUT_PIPE);
+  GInputStream *stdout_pipe = NULL;
+  gint stdout_fd = -1;
+
+  stdout_pipe = g_subprocess_get_stdout_pipe (self->dbus_monitor);
+  g_return_val_if_fail (stdout_pipe != NULL, FALSE);
+
+  stdout_fd = g_unix_input_stream_get_fd (G_UNIX_INPUT_STREAM (stdout_pipe));
+  g_return_val_if_fail (stdout_fd >= 0, FALSE);
+
+  g_subprocess_launcher_take_stdin_fd (launcher, stdout_fd);
+
+  return g_subprocess_launcher_spawn (launcher, error,
+                                      "tee", self->filename, NULL);
+}
+
 static gboolean
 initable_init (
     GInitable *initable,
@@ -950,36 +953,24 @@ initable_init (
                            G_CALLBACK (cancellable_cancelled_cb),
                            self, NULL);
 
-  self->pcap_out = pcap_open_dead (DLT_DBUS, 1 << 27);
-  if (self->pcap_out == NULL)
-    {
-      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
-          "pcap_open_dead failed. wtf");
-      return FALSE;
-    }
-
-  self->dumper = pcap_dump_open (self->pcap_out, self->filename);
-  if (self->dumper == NULL)
-    {
-      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
-          "Couldn't open target file %s", pcap_geterr (self->pcap_out));
-      return FALSE;
-    }
-
   self->dbus_monitor = spawn_monitor (self, (const char * const *) argv, error);
   if (self->dbus_monitor == NULL)
     return FALSE;
 
-  stdout_pipe = g_subprocess_get_stdout_pipe (self->dbus_monitor);
+  self->tee_proc = spawn_tee (self, error);
+  if (self->tee_proc == NULL)
+    return FALSE;
+
+  stdout_pipe = g_subprocess_get_stdout_pipe (self->tee_proc);
   g_return_val_if_fail (stdout_pipe != NULL, FALSE);
   g_return_val_if_fail (G_IS_POLLABLE_INPUT_STREAM (stdout_pipe), FALSE);
   g_return_val_if_fail (G_IS_UNIX_INPUT_STREAM (stdout_pipe), FALSE);
 
-  self->dbus_monitor_source = g_pollable_input_stream_create_source (
+  self->tee_source = g_pollable_input_stream_create_source (
       G_POLLABLE_INPUT_STREAM (stdout_pipe), self->cancellable);
-  g_source_set_callback (self->dbus_monitor_source,
+  g_source_set_callback (self->tee_source,
       (GSourceFunc) dbus_monitor_readable, self, NULL);
-  g_source_attach (self->dbus_monitor_source, NULL);
+  g_source_attach (self->tee_source, NULL);
 
   g_subprocess_wait_check_async (
       self->dbus_monitor,