make some functions static, ensure shutdown tasks could be run repeatedly if 1st...
[oweals/gnunet.git] / src / util / helper.c
index 03e71585c07330a428902459445ade51ec609b4c..a84b06e6645d013c3e18fedf80afb88e42ef3440 100644 (file)
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2011, 2012 Christian Grothoff
+     Copyright (C) 2011, 2012 Christian Grothoff
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
 
      You should have received a copy of the GNU General Public License
      along with GNUnet; see the file COPYING.  If not, write to the
-     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-     Boston, MA 02111-1307, USA.
+     Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+     Boston, MA 02110-1301, USA.
 */
 
 /**
  * @file util/helper.c
- * @brief API for dealing with (SUID) helper processes that communicate via GNUNET_MessageHeaders on stdin/stdout
+ * @brief API for dealing with (SUID) helper processes that communicate via
+ *          GNUNET_MessageHeaders on stdin/stdout
  * @author Philipp Toelke
  * @author Christian Grothoff
  */
 #include "platform.h"
 #include "gnunet_util_lib.h"
+#include "gnunet_mst_lib.h"
 
 
 /**
@@ -48,12 +50,12 @@ struct GNUNET_HELPER_SendHandle
    * Message to transmit (allocated at the end of this struct)
    */
   const struct GNUNET_MessageHeader *msg;
+
   /**
    * The handle to a helper process.
    */
   struct GNUNET_HELPER_Handle *h;
+
   /**
    * Function to call upon completion.
    */
@@ -82,22 +84,22 @@ struct GNUNET_HELPER_Handle
    * PipeHandle to receive data from the helper
    */
   struct GNUNET_DISK_PipeHandle *helper_in;
-  
+
   /**
    * PipeHandle to send data to the helper
    */
   struct GNUNET_DISK_PipeHandle *helper_out;
-  
+
   /**
    * FileHandle to receive data from the helper
    */
   const struct GNUNET_DISK_FileHandle *fh_from_helper;
-  
+
   /**
    * FileHandle to send data to the helper
    */
   const struct GNUNET_DISK_FileHandle *fh_to_helper;
-  
+
   /**
    * The process id of the helper
    */
@@ -106,7 +108,7 @@ struct GNUNET_HELPER_Handle
   /**
    * The Message-Tokenizer that tokenizes the messages comming from the helper
    */
-  struct GNUNET_SERVER_MessageStreamTokenizer *mst;
+  struct GNUNET_MessageStreamTokenizer *mst;
 
   /**
    * The exception callback
@@ -131,67 +133,122 @@ struct GNUNET_HELPER_Handle
   /**
    * Binary to run.
    */
-  const char *binary_name;
+  char *binary_name;
 
   /**
    * NULL-terminated list of command-line arguments.
    */
   char **binary_argv;
-                   
+
   /**
    * Task to read from the helper.
    */
-  GNUNET_SCHEDULER_TaskIdentifier read_task;
+  struct GNUNET_SCHEDULER_Task *read_task;
 
   /**
    * Task to read from the helper.
    */
-  GNUNET_SCHEDULER_TaskIdentifier write_task;
+  struct GNUNET_SCHEDULER_Task *write_task;
 
   /**
    * Restart task.
    */
-  GNUNET_SCHEDULER_TaskIdentifier restart_task;
+  struct GNUNET_SCHEDULER_Task *restart_task;
 
   /**
    * Does the helper support the use of a control pipe for signalling?
    */
   int with_control_pipe;
 
+  /**
+   * Count start attempts to increase linear back off
+   */
+  unsigned int retry_back_off;
 };
 
 
 /**
- * Stop the helper process, we're closing down or had an error.
+ * Sends termination signal to the helper process.  The helper process is not
+ * reaped; call GNUNET_HELPER_wait() for reaping the dead helper process.
  *
- * @param h handle to the helper process
+ * @param h the helper handle
+ * @param soft_kill if GNUNET_YES, signals termination by closing the helper's
+ *          stdin; GNUNET_NO to signal termination by sending SIGTERM to helper
+ * @return #GNUNET_OK on success; #GNUNET_SYSERR on error
  */
-static void
-stop_helper (struct GNUNET_HELPER_Handle *h)
+int
+GNUNET_HELPER_kill (struct GNUNET_HELPER_Handle *h,
+                   int soft_kill)
 {
   struct GNUNET_HELPER_SendHandle *sh;
+  int ret;
 
-  if (NULL != h->helper_proc)
+  while (NULL != (sh = h->sh_head))
   {
-    GNUNET_break (0 == GNUNET_OS_process_kill (h->helper_proc, SIGTERM));
-    GNUNET_break (GNUNET_OK == GNUNET_OS_process_wait (h->helper_proc));
-    GNUNET_OS_process_destroy (h->helper_proc);
-    h->helper_proc = NULL;
+    GNUNET_CONTAINER_DLL_remove (h->sh_head,
+                                h->sh_tail,
+                                sh);
+    if (NULL != sh->cont)
+      sh->cont (sh->cont_cls, GNUNET_NO);
+    GNUNET_free (sh);
   }
-  if (GNUNET_SCHEDULER_NO_TASK != h->restart_task)
+  if (NULL != h->restart_task)
   {
     GNUNET_SCHEDULER_cancel (h->restart_task);
-    h->restart_task = GNUNET_SCHEDULER_NO_TASK;
+    h->restart_task = NULL;
+  }
+  if (NULL != h->read_task)
+  {
+    GNUNET_SCHEDULER_cancel (h->read_task);
+    h->read_task = NULL;
+  }
+  if (NULL == h->helper_proc)
+    return GNUNET_SYSERR;
+  if (GNUNET_YES == soft_kill)
+  {
+    /* soft-kill only possible with pipes */
+    GNUNET_assert (NULL != h->helper_in);
+    ret = GNUNET_DISK_pipe_close (h->helper_in);
+    h->helper_in = NULL;
+    h->fh_to_helper = NULL;
+    return ret;
+  }
+  if (0 != GNUNET_OS_process_kill (h->helper_proc, GNUNET_TERM_SIG))
+    return GNUNET_SYSERR;
+  return GNUNET_OK;
+}
+
+
+/**
+ * Reap the helper process.  This call is blocking(!).  The helper process
+ * should either be sent a termination signal before or should be dead before
+ * calling this function
+ *
+ * @param h the helper handle
+ * @return #GNUNET_OK on success; #GNUNET_SYSERR on error
+ */
+int
+GNUNET_HELPER_wait (struct GNUNET_HELPER_Handle *h)
+{
+  struct GNUNET_HELPER_SendHandle *sh;
+  int ret;
+
+  ret = GNUNET_SYSERR;
+  if (NULL != h->helper_proc)
+  {
+    ret = GNUNET_OS_process_wait (h->helper_proc);
+    GNUNET_OS_process_destroy (h->helper_proc);
+    h->helper_proc = NULL;
   }
-  if (GNUNET_SCHEDULER_NO_TASK != h->read_task)
+  if (NULL != h->read_task)
   {
     GNUNET_SCHEDULER_cancel (h->read_task);
-    h->read_task = GNUNET_SCHEDULER_NO_TASK;
+    h->read_task = NULL;
   }
-  if (GNUNET_SCHEDULER_NO_TASK != h->write_task)
+  if (NULL != h->write_task)
   {
     GNUNET_SCHEDULER_cancel (h->write_task);
-    h->write_task = GNUNET_SCHEDULER_NO_TASK;
+    h->write_task = NULL;
   }
   if (NULL != h->helper_in)
   {
@@ -215,7 +272,36 @@ stop_helper (struct GNUNET_HELPER_Handle *h)
     GNUNET_free (sh);
   }
   /* purge MST buffer */
-  (void) GNUNET_SERVER_mst_receive (h->mst, NULL, NULL, 0, GNUNET_YES, GNUNET_NO);
+  if (NULL != h->mst)
+    (void) GNUNET_MST_from_buffer (h->mst,
+                                   NULL, 0,
+                                   GNUNET_YES,
+                                   GNUNET_NO);
+  return ret;
+}
+
+
+/**
+ * Stop the helper process, we're closing down or had an error.
+ *
+ * @param h handle to the helper process
+ * @param soft_kill if #GNUNET_YES, signals termination by closing the helper's
+ *          stdin; #GNUNET_NO to signal termination by sending SIGTERM to helper
+ */
+static void
+stop_helper (struct GNUNET_HELPER_Handle *h,
+            int soft_kill)
+{
+  if (NULL != h->restart_task)
+  {
+    GNUNET_SCHEDULER_cancel (h->restart_task);
+    h->restart_task = NULL;
+  }
+  else
+  {
+    GNUNET_break (GNUNET_OK == GNUNET_HELPER_kill (h, soft_kill));
+    GNUNET_break (GNUNET_OK == GNUNET_HELPER_wait (h));
+  }
 }
 
 
@@ -223,35 +309,24 @@ stop_helper (struct GNUNET_HELPER_Handle *h)
  * Restart the helper process.
  *
  * @param cls handle to the helper process
- * @param tc scheduler context
  */
 static void
-restart_task (void *cls,
-             const struct GNUNET_SCHEDULER_TaskContext *tc);
+restart_task (void *cls);
 
 
 /**
  * Read from the helper-process
  *
  * @param cls handle to the helper process
- * @param tc scheduler context
  */
 static void
-helper_read (void *cls,
-            const struct GNUNET_SCHEDULER_TaskContext *tc)
+helper_read (void *cls)
 {
   struct GNUNET_HELPER_Handle *h = cls;
-  char buf[GNUNET_SERVER_MAX_MESSAGE_SIZE] GNUNET_ALIGN;
+  char buf[GNUNET_MAX_MESSAGE_SIZE] GNUNET_ALIGN;
   ssize_t t;
 
-  h->read_task = GNUNET_SCHEDULER_NO_TASK;
-  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
-  {
-    /* try again */
-    h->read_task = GNUNET_SCHEDULER_add_read_file (GNUNET_TIME_UNIT_FOREVER_REL,
-                                                  h->fh_from_helper, &helper_read, h);
-    return;
-  }
+  h->read_task = NULL;
   t = GNUNET_DISK_file_read (h->fh_from_helper, &buf, sizeof (buf));
   if (t < 0)
   {
@@ -263,58 +338,64 @@ helper_read (void *cls,
     if (NULL != h->exp_cb)
     {
       h->exp_cb (h->cb_cls);
-      GNUNET_HELPER_stop (h);
+      GNUNET_HELPER_stop (h, GNUNET_NO);
       return;
     }
-    stop_helper (h);
+    stop_helper (h, GNUNET_NO);
     /* Restart the helper */
-    h->restart_task =
-       GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS, &restart_task, h);
+    h->restart_task = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS,
+                                                                                  h->retry_back_off),
+                                                   &restart_task, h);
     return;
   }
   if (0 == t)
   {
-    /* this happens if the helper is shut down via a 
+    /* this happens if the helper is shut down via a
        signal, so it is not a "hard" error */
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, 
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Got 0 bytes from helper `%s' (EOF)\n",
                h->binary_name);
     if (NULL != h->exp_cb)
     {
       h->exp_cb (h->cb_cls);
-      GNUNET_HELPER_stop (h);
+      GNUNET_HELPER_stop (h, GNUNET_NO);
       return;
     }
-    stop_helper (h);
+    stop_helper (h, GNUNET_NO);
     /* Restart the helper */
-    h->restart_task =
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                   &restart_task, h);
+    h->restart_task
+      = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS,
+                                                                  h->retry_back_off),
+                                    &restart_task, h);
     return;
   }
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, 
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Got %u bytes from helper `%s'\n",
              (unsigned int) t,
              h->binary_name);
   h->read_task = GNUNET_SCHEDULER_add_read_file (GNUNET_TIME_UNIT_FOREVER_REL,
-                                                h->fh_from_helper, &helper_read, h);
+                                                h->fh_from_helper,
+                                                &helper_read, h);
   if (GNUNET_SYSERR ==
-      GNUNET_SERVER_mst_receive (h->mst, NULL, buf, t, GNUNET_NO, GNUNET_NO))
+      GNUNET_MST_from_buffer (h->mst,
+                              buf, t,
+                              GNUNET_NO,
+                              GNUNET_NO))
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_WARNING, 
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                _("Failed to parse inbound message from helper `%s'\n"),
                h->binary_name);
     if (NULL != h->exp_cb)
     {
       h->exp_cb (h->cb_cls);
-      GNUNET_HELPER_stop (h);
+      GNUNET_HELPER_stop (h, GNUNET_NO);
       return;
-    }     
-    stop_helper (h);
+    }
+    stop_helper (h, GNUNET_NO);
     /* Restart the helper */
-    h->restart_task =
-        GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                      &restart_task, h);
+    h->restart_task = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS,
+                                                                                 h->retry_back_off),
+                                                   &restart_task, h);
     return;
   }
 }
@@ -333,10 +414,11 @@ start_helper (struct GNUNET_HELPER_Handle *h)
   if ( (h->helper_in == NULL) || (h->helper_out == NULL))
   {
     /* out of file descriptors? try again later... */
-    stop_helper (h);
+    stop_helper (h, GNUNET_NO);
     h->restart_task =
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                   &restart_task, h);    
+      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS,
+                                                                 h->retry_back_off),
+                                   &restart_task, h);
     return;
   }
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
@@ -347,25 +429,26 @@ start_helper (struct GNUNET_HELPER_Handle *h)
   h->fh_to_helper =
       GNUNET_DISK_pipe_handle (h->helper_in, GNUNET_DISK_PIPE_END_WRITE);
   h->helper_proc =
-    GNUNET_OS_start_process_vap (h->with_control_pipe, GNUNET_OS_INHERIT_STD_ERR, 
-                                h->helper_in, h->helper_out,
+    GNUNET_OS_start_process_vap (h->with_control_pipe, GNUNET_OS_INHERIT_STD_ERR,
+                                h->helper_in, h->helper_out, NULL,
                                 h->binary_name,
                                 h->binary_argv);
   if (NULL == h->helper_proc)
   {
     /* failed to start process? try again later... */
-    stop_helper (h);
-    h->restart_task =
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                   &restart_task, h);    
+    stop_helper (h, GNUNET_NO);
+    h->restart_task = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS,
+                                                                                 h->retry_back_off),
+                                                   &restart_task, h);
     return;
   }
   GNUNET_DISK_pipe_close_end (h->helper_out, GNUNET_DISK_PIPE_END_WRITE);
   GNUNET_DISK_pipe_close_end (h->helper_in, GNUNET_DISK_PIPE_END_READ);
-  h->read_task = GNUNET_SCHEDULER_add_read_file (GNUNET_TIME_UNIT_FOREVER_REL,
-                                                h->fh_from_helper, 
-                                                &helper_read, 
-                                                h);
+  if (NULL != h->mst)
+    h->read_task = GNUNET_SCHEDULER_add_read_file (GNUNET_TIME_UNIT_FOREVER_REL,
+                                                  h->fh_from_helper,
+                                                  &helper_read,
+                                                  h);
 }
 
 
@@ -373,15 +456,17 @@ start_helper (struct GNUNET_HELPER_Handle *h)
  * Restart the helper process.
  *
  * @param cls handle to the helper process
- * @param tc scheduler context
  */
 static void
-restart_task (void *cls,
-             const struct GNUNET_SCHEDULER_TaskContext *tc)
+restart_task (void *cls)
 {
   struct GNUNET_HELPER_Handle*h = cls;
 
-  h->restart_task = GNUNET_SCHEDULER_NO_TASK;
+  h->restart_task = NULL;
+  h->retry_back_off++;
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Restarting helper with back-off %u\n",
+              h->retry_back_off);
   start_helper (h);
 }
 
@@ -406,43 +491,54 @@ struct GNUNET_HELPER_Handle *
 GNUNET_HELPER_start (int with_control_pipe,
                     const char *binary_name,
                     char *const binary_argv[],
-                    GNUNET_SERVER_MessageTokenizerCallback cb,
+                    GNUNET_MessageTokenizerCallback cb,
                     GNUNET_HELPER_ExceptionCallback exp_cb,
                     void *cb_cls)
 {
-  struct GNUNET_HELPER_Handle*h;
-  int c = 0;
-  h =  GNUNET_malloc (sizeof (struct GNUNET_HELPER_Handle));
-  h->with_control_pipe = with_control_pipe;
-  h->binary_name = GNUNET_strdup (binary_name);
+  struct GNUNET_HELPER_Handle *h;
+  unsigned int c;
 
-  for (c = 0; binary_argv[c] != NULL; c++)
-    c ++;
-  h->binary_argv = GNUNET_malloc (sizeof (char *[c + 1]));
-  for (c = 0; binary_argv[c] != NULL; c++)
+  h = GNUNET_new (struct GNUNET_HELPER_Handle);
+  h->with_control_pipe = with_control_pipe;
+  /* Lookup in libexec path only if we are starting gnunet helpers */
+  if (NULL != strstr (binary_name, "gnunet"))
+    h->binary_name = GNUNET_OS_get_libexec_binary_path (binary_name);
+  else
+    h->binary_name = GNUNET_strdup (binary_name);
+  for (c = 0; NULL != binary_argv[c]; c++);
+  h->binary_argv = GNUNET_malloc (sizeof (char *) * (c + 1));
+  for (c = 0; NULL != binary_argv[c]; c++)
     h->binary_argv[c] = GNUNET_strdup (binary_argv[c]);
   h->binary_argv[c] = NULL;
-
   h->cb_cls = cb_cls;
-  h->mst = GNUNET_SERVER_mst_create (cb, h->cb_cls);
+  if (NULL != cb)
+    h->mst = GNUNET_MST_create (cb,
+                                h->cb_cls);
   h->exp_cb = exp_cb;
+  h->retry_back_off = 0;
   start_helper (h);
   return h;
 }
 
 
 /**
- * @brief Kills the helper, closes the pipe and frees the h
+ * Free's the resources occupied by the helper handle
  *
- * @param h h to helper to stop
+ * @param h the helper handle to free
  */
 void
-GNUNET_HELPER_stop (struct GNUNET_HELPER_Handle *h)
+GNUNET_HELPER_destroy (struct GNUNET_HELPER_Handle *h)
 {
+  unsigned int c;
   struct GNUNET_HELPER_SendHandle *sh;
-  int c;
-  h->exp_cb = NULL;
-  /* signal pending writes that we were stopped */
+
+  if (NULL != h->write_task)
+  {
+    GNUNET_SCHEDULER_cancel (h->write_task);
+    h->write_task = NULL;
+  }
+  GNUNET_assert (NULL == h->read_task);
+  GNUNET_assert (NULL == h->restart_task);
   while (NULL != (sh = h->sh_head))
   {
     GNUNET_CONTAINER_DLL_remove (h->sh_head,
@@ -452,9 +548,9 @@ GNUNET_HELPER_stop (struct GNUNET_HELPER_Handle *h)
       sh->cont (sh->cont_cls, GNUNET_SYSERR);
     GNUNET_free (sh);
   }
-  stop_helper (h);
-  GNUNET_SERVER_mst_destroy (h->mst);
-  GNUNET_free ((char *) h->binary_name);
+  if (NULL != h->mst)
+    GNUNET_MST_destroy (h->mst);
+  GNUNET_free (h->binary_name);
   for (c = 0; h->binary_argv[c] != NULL; c++)
     GNUNET_free (h->binary_argv[c]);
   GNUNET_free (h->binary_argv);
@@ -462,53 +558,73 @@ GNUNET_HELPER_stop (struct GNUNET_HELPER_Handle *h)
 }
 
 
+/**
+ * Kills the helper, closes the pipe and frees the handle
+ *
+ * @param h handle to helper to stop
+ * @param soft_kill if #GNUNET_YES, signals termination by closing the helper's
+ *          stdin; #GNUNET_NO to signal termination by sending SIGTERM to helper
+ */
+void
+GNUNET_HELPER_stop (struct GNUNET_HELPER_Handle *h,
+                   int soft_kill)
+{
+  h->exp_cb = NULL;
+  stop_helper (h, soft_kill);
+  GNUNET_HELPER_destroy (h);
+}
+
+
 /**
  * Write to the helper-process
  *
  * @param cls handle to the helper process
- * @param tc scheduler context
  */
 static void
-helper_write (void *cls,
-            const struct GNUNET_SCHEDULER_TaskContext *tc)
+helper_write (void *cls)
 {
   struct GNUNET_HELPER_Handle *h = cls;
   struct GNUNET_HELPER_SendHandle *sh;
   const char *buf;
   ssize_t t;
 
-  h->write_task = GNUNET_SCHEDULER_NO_TASK;
-  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
-  {
-    /* try again */
-    h->write_task = GNUNET_SCHEDULER_add_read_file (GNUNET_TIME_UNIT_FOREVER_REL,
-                                                   h->fh_to_helper, &helper_write, h);
-    return;
-  }  
+  h->write_task = NULL;
   if (NULL == (sh = h->sh_head))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Helper write had no work!\n");
     return; /* how did this happen? */
+  }
   buf = (const char*) sh->msg;
-  t = GNUNET_DISK_file_write (h->fh_to_helper, &buf[sh->wpos], ntohs (sh->msg->size) - sh->wpos);
-  if (t <= 0)
+  t = GNUNET_DISK_file_write (h->fh_to_helper,
+                             &buf[sh->wpos],
+                             ntohs (sh->msg->size) - sh->wpos);
+  if (-1 == t)
   {
     /* On write-error, restart the helper */
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                _("Error writing to `%s': %s\n"),
+               _("Error writing to `%s': %s\n"),
                h->binary_name,
                STRERROR (errno));
     if (NULL != h->exp_cb)
     {
       h->exp_cb (h->cb_cls);
-      GNUNET_HELPER_stop (h);
+      GNUNET_HELPER_stop (h, GNUNET_NO);
       return;
     }
-    stop_helper (h);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+               "Stopping and restarting helper task!\n");
+    stop_helper (h, GNUNET_NO);
     /* Restart the helper */
-    h->restart_task =
-      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
-                                   &restart_task, h);
+    h->restart_task = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS,
+                                                                                 h->retry_back_off),
+                                                   &restart_task, h);
     return;
   }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Transmitted %u bytes to %s\n",
+             (unsigned int) t,
+             h->binary_name);
   sh->wpos += t;
   if (sh->wpos == ntohs (sh->msg->size))
   {
@@ -521,8 +637,8 @@ helper_write (void *cls,
   }
   if (NULL != h->sh_head)
     h->write_task = GNUNET_SCHEDULER_add_write_file (GNUNET_TIME_UNIT_FOREVER_REL,
-                                                    h->fh_to_helper, 
-                                                    &helper_write, 
+                                                    h->fh_to_helper,
+                                                    &helper_write,
                                                     h);
 }
 
@@ -533,15 +649,15 @@ helper_write (void *cls,
  * @param h helper to send message to
  * @param msg message to send
  * @param can_drop can the message be dropped if there is already one in the queue?
- * @param cont continuation to run once the message is out (PREREQ_DONE on succees, CANCEL
- *             if the helper process died, NULL during GNUNET_HELPER_stop).
- * @param cont_cls closure for 'cont'
- * @return NULL if the message was dropped, 
+ * @param cont continuation to run once the message is out (#GNUNET_OK on succees, #GNUNET_NO
+ *             if the helper process died, #GNUNET_SYSERR during #GNUNET_HELPER_destroy).
+ * @param cont_cls closure for @a cont
+ * @return NULL if the message was dropped,
  *         otherwise handle to cancel *cont* (actual transmission may
  *         not be abortable)
  */
 struct GNUNET_HELPER_SendHandle *
-GNUNET_HELPER_send (struct GNUNET_HELPER_Handle *h, 
+GNUNET_HELPER_send (struct GNUNET_HELPER_Handle *h,
                    const struct GNUNET_MessageHeader *msg,
                    int can_drop,
                    GNUNET_HELPER_Continuation cont,
@@ -558,24 +674,24 @@ GNUNET_HELPER_send (struct GNUNET_HELPER_Handle *h,
   mlen = ntohs (msg->size);
   sh = GNUNET_malloc (sizeof (struct GNUNET_HELPER_SendHandle) + mlen);
   sh->msg = (const struct GNUNET_MessageHeader*) &sh[1];
-  memcpy (&sh[1], msg, mlen);
+  GNUNET_memcpy (&sh[1], msg, mlen);
   sh->h = h;
   sh->cont = cont;
   sh->cont_cls = cont_cls;
   GNUNET_CONTAINER_DLL_insert_tail (h->sh_head,
                                    h->sh_tail,
                                    sh);
-  if (GNUNET_SCHEDULER_NO_TASK == h->write_task)
+  if (NULL == h->write_task)
     h->write_task = GNUNET_SCHEDULER_add_write_file (GNUNET_TIME_UNIT_FOREVER_REL,
-                                                    h->fh_to_helper, 
-                                                    &helper_write, 
+                                                    h->fh_to_helper,
+                                                    &helper_write,
                                                     h);
-    
+
   return sh;
 }
 
 /**
- * Cancel a 'send' operation.  If possible, transmitting the
+ * Cancel a #GNUNET_HELPER_send operation.  If possible, transmitting the
  * message is also aborted, but at least 'cont' won't be
  * called.
  *
@@ -591,12 +707,12 @@ GNUNET_HELPER_send_cancel (struct GNUNET_HELPER_SendHandle *sh)
   if (0 == sh->wpos)
   {
     GNUNET_CONTAINER_DLL_remove (h->sh_head, h->sh_tail, sh);
+    GNUNET_free (sh);
     if (NULL == h->sh_head)
     {
       GNUNET_SCHEDULER_cancel (h->write_task);
-      h->write_task = GNUNET_SCHEDULER_NO_TASK;
+      h->write_task = NULL;
     }
-    GNUNET_free (sh);
   }
 }