Imported Upstream version 0.9.2upstream/0.9.2

1 files changed, 1216 insertions, 0 deletions

diff --git a/src/util/client.c b/src/util/client.c
new file mode 100644
index 0000000..2f09a90
--- /dev/null
+++ b/src/util/client.c
@@ -0,0 +1,1216 @@
+/*
+     This file is part of GNUnet.
+     (C) 2001, 2002, 2006, 2008, 2009 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 2, or (at your
+     option) any later version.
+
+     GNUnet 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
+     General Public License for more details.
+
+     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.
+*/
+
+/**
+ * @file util/client.c
+ * @brief code for access to services
+ * @author Christian Grothoff
+ *
+ * Generic TCP code for reliable, record-oriented TCP
+ * connections between clients and service providers.
+ */
+
+#include "platform.h"
+#include "gnunet_common.h"
+#include "gnunet_client_lib.h"
+#include "gnunet_protocols.h"
+#include "gnunet_server_lib.h"
+#include "gnunet_scheduler_lib.h"
+
+#define DEBUG_CLIENT GNUNET_EXTRA_LOGGING
+
+/**
+ * How often do we re-try tranmsitting requests before giving up?
+ * Note that if we succeeded transmitting a request but failed to read
+ * a response, we do NOT re-try.
+ */
+#define MAX_ATTEMPTS 50
+
+#define LOG(kind,...) GNUNET_log_from (kind, "util",__VA_ARGS__)
+
+/**
+ * Handle for a transmission request.
+ */
+struct GNUNET_CLIENT_TransmitHandle
+{
+  /**
+   * Connection state.
+   */
+  struct GNUNET_CLIENT_Connection *sock;
+
+  /**
+   * Function to call to get the data for transmission.
+   */
+  GNUNET_CONNECTION_TransmitReadyNotify notify;
+
+  /**
+   * Closure for notify.
+   */
+  void *notify_cls;
+
+  /**
+   * Handle to the transmission with the underlying
+   * connection.
+   */
+  struct GNUNET_CONNECTION_TransmitHandle *th;
+
+  /**
+   * If we are re-trying and are delaying to do so,
+   * handle to the scheduled task managing the delay.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier reconnect_task;
+
+  /**
+   * Timeout for the operation overall.
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+  /**
+   * Number of bytes requested.
+   */
+  size_t size;
+
+  /**
+   * Are we allowed to re-try to connect without telling
+   * the user (of this API) about the connection troubles?
+   */
+  int auto_retry;
+
+  /**
+   * Number of attempts left for transmitting the request.  We may
+   * fail the first time (say because the service is not yet up), in
+   * which case (if auto_retry is set) we wait a bit and re-try
+   * (timeout permitting).
+   */
+  unsigned int attempts_left;
+
+};
+
+
+/**
+ * Context for processing
+ * "GNUNET_CLIENT_transmit_and_get_response" requests.
+ */
+struct TransmitGetResponseContext
+{
+  /**
+   * Client handle.
+   */
+  struct GNUNET_CLIENT_Connection *sock;
+
+  /**
+   * Message to transmit; do not free, allocated
+   * right after this struct.
+   */
+  const struct GNUNET_MessageHeader *hdr;
+
+  /**
+   * Timeout to use.
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+  /**
+   * Function to call when done.
+   */
+  GNUNET_CLIENT_MessageHandler rn;
+
+  /**
+   * Closure for "rn".
+   */
+  void *rn_cls;
+};
+
+/**
+ * Struct to refer to a GNUnet TCP connection.
+ * This is more than just a socket because if the server
+ * drops the connection, the client automatically tries
+ * to reconnect (and for that needs connection information).
+ */
+struct GNUNET_CLIENT_Connection
+{
+
+  /**
+   * the socket handle, NULL if not live
+   */
+  struct GNUNET_CONNECTION_Handle *sock;
+
+  /**
+   * Our configuration.
+   */
+  const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+  /**
+   * Name of the service we interact with.
+   */
+  char *service_name;
+
+  /**
+   * Context of a transmit_and_get_response operation, NULL
+   * if no such operation is pending.
+   */
+  struct TransmitGetResponseContext *tag;
+
+  /**
+   * Handler for current receiver task.
+   */
+  GNUNET_CLIENT_MessageHandler receiver_handler;
+
+  /**
+   * Closure for receiver_handler.
+   */
+  void *receiver_handler_cls;
+
+  /**
+   * Handle for a pending transmission request, NULL if there is
+   * none pending.
+   */
+  struct GNUNET_CLIENT_TransmitHandle *th;
+
+  /**
+   * Handler for service test completion (NULL unless in service_test)
+   */
+  GNUNET_SCHEDULER_Task test_cb;
+
+  /**
+   * Deadline for calling 'test_cb'.
+   */
+  struct GNUNET_TIME_Absolute test_deadline;
+
+  /**
+   * If we are re-trying and are delaying to do so,
+   * handle to the scheduled task managing the delay.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier receive_task;
+
+  /**
+   * Closure for test_cb (NULL unless in service_test)
+   */
+  void *test_cb_cls;
+
+  /**
+   * Buffer for received message.
+   */
+  char *received_buf;
+
+  /**
+   * Timeout for receiving a response (absolute time).
+   */
+  struct GNUNET_TIME_Absolute receive_timeout;
+
+  /**
+   * Current value for our incremental back-off (for
+   * connect re-tries).
+   */
+  struct GNUNET_TIME_Relative back_off;
+
+  /**
+   * Number of bytes in received_buf that are valid.
+   */
+  size_t received_pos;
+
+  /**
+   * Size of received_buf.
+   */
+  unsigned int received_size;
+
+  /**
+   * Do we have a complete response in received_buf?
+   */
+  int msg_complete;
+
+  /**
+   * Are we currently busy doing receive-processing?
+   * GNUNET_YES if so, GNUNET_NO if not.
+   */
+  int in_receive;
+
+  /**
+   * How often have we tried to connect?
+   */
+  unsigned int attempts;
+
+};
+
+
+/**
+ * Try to connect to the service.
+ *
+ * @param service_name name of service to connect to
+ * @param cfg configuration to use
+ * @param attempt counter used to alternate between IP and UNIX domain sockets
+ * @return NULL on error
+ */
+static struct GNUNET_CONNECTION_Handle *
+do_connect (const char *service_name,
+            const struct GNUNET_CONFIGURATION_Handle *cfg, unsigned int attempt)
+{
+  struct GNUNET_CONNECTION_Handle *sock;
+  char *hostname;
+  char *unixpath;
+  unsigned long long port;
+
+  sock = NULL;
+#if AF_UNIX
+  if (0 == (attempt % 2))
+  {
+    /* on even rounds, try UNIX */
+    unixpath = NULL;
+    if ((GNUNET_OK == GNUNET_CONFIGURATION_get_value_string (cfg, service_name, "UNIXPATH", &unixpath)) && (0 < strlen (unixpath)))     /* We have a non-NULL unixpath, does that mean it's valid? */
+    {
+      sock = GNUNET_CONNECTION_create_from_connect_to_unixpath (cfg, unixpath);
+      if (sock != NULL)
+      {
+#if DEBUG_CLIENT
+        LOG (GNUNET_ERROR_TYPE_DEBUG, "Connected to unixpath `%s'!\n",
+             unixpath);
+#endif
+        GNUNET_free (unixpath);
+        return sock;
+      }
+    }
+    GNUNET_free_non_null (unixpath);
+  }
+#endif
+
+  if (GNUNET_YES ==
+      GNUNET_CONFIGURATION_have_value (cfg, service_name, "PORT"))
+  {
+    if ((GNUNET_OK !=
+	 GNUNET_CONFIGURATION_get_value_number (cfg, service_name, "PORT", &port))
+	|| (port > 65535) ||
+	(GNUNET_OK !=
+	 GNUNET_CONFIGURATION_get_value_string (cfg, service_name, "HOSTNAME",
+						&hostname)))
+    {
+      LOG (GNUNET_ERROR_TYPE_WARNING,
+	   _
+	   ("Could not determine valid hostname and port for service `%s' from configuration.\n"),
+	   service_name);
+      return NULL;
+    }
+    if (0 == strlen (hostname))
+    {
+      GNUNET_free (hostname);
+      LOG (GNUNET_ERROR_TYPE_WARNING,
+	   _("Need a non-empty hostname for service `%s'.\n"), service_name);
+      return NULL;
+    }
+  }
+  else
+  {
+    /* unspecified means 0 (disabled) */
+    port = 0;
+    hostname = NULL;
+  }
+  if (port == 0)
+  {
+#if AF_UNIX
+    if (0 != (attempt % 2))
+    {
+      /* try UNIX */
+      unixpath = NULL;
+      if ((GNUNET_OK ==
+           GNUNET_CONFIGURATION_get_value_string (cfg, service_name, "UNIXPATH",
+                                                  &unixpath)) &&
+          (0 < strlen (unixpath)))
+      {
+        sock =
+            GNUNET_CONNECTION_create_from_connect_to_unixpath (cfg, unixpath);
+        if (sock != NULL)
+        {
+          GNUNET_free (unixpath);
+          GNUNET_free_non_null (hostname);
+          return sock;
+        }
+      }
+      GNUNET_free_non_null (unixpath);
+    }
+#endif
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Port is 0 for service `%s', UNIXPATH did not work, returning NULL!\n",
+         service_name);
+#endif
+    GNUNET_free_non_null (hostname);
+    return NULL;
+  }
+
+  sock = GNUNET_CONNECTION_create_from_connect (cfg, hostname, port);
+  GNUNET_free (hostname);
+  return sock;
+}
+
+
+/**
+ * Get a connection with a service.
+ *
+ * @param service_name name of the service
+ * @param cfg configuration to use
+ * @return NULL on error (service unknown to configuration)
+ */
+struct GNUNET_CLIENT_Connection *
+GNUNET_CLIENT_connect (const char *service_name,
+                       const struct GNUNET_CONFIGURATION_Handle *cfg)
+{
+  struct GNUNET_CLIENT_Connection *ret;
+  struct GNUNET_CONNECTION_Handle *sock;
+
+  sock = do_connect (service_name, cfg, 0);
+  ret = GNUNET_malloc (sizeof (struct GNUNET_CLIENT_Connection));
+  ret->attempts = 1;
+  ret->sock = sock;
+  ret->service_name = GNUNET_strdup (service_name);
+  ret->cfg = cfg;
+  ret->back_off = GNUNET_TIME_UNIT_MILLISECONDS;
+  return ret;
+}
+
+
+/**
+ * Destroy connection with the service.  This will automatically
+ * cancel any pending "receive" request (however, the handler will
+ * *NOT* be called, not even with a NULL message).  Any pending
+ * transmission request will also be cancelled UNLESS the callback for
+ * the transmission request has already been called, in which case the
+ * transmission 'finish_pending_write' argument determines whether or
+ * not the write is guaranteed to complete before the socket is fully
+ * destroyed (unless, of course, there is an error with the server in
+ * which case the message may still be lost).
+ *
+ * @param finish_pending_write should a transmission already passed to the
+ *          handle be completed?
+ * @param sock handle to the service connection
+ */
+void
+GNUNET_CLIENT_disconnect (struct GNUNET_CLIENT_Connection *sock,
+                          int finish_pending_write)
+{
+  if (sock->in_receive == GNUNET_YES)
+  {
+    GNUNET_CONNECTION_receive_cancel (sock->sock);
+    sock->in_receive = GNUNET_NO;
+  }
+  if (sock->th != NULL)
+  {
+    GNUNET_CLIENT_notify_transmit_ready_cancel (sock->th);
+    sock->th = NULL;
+  }
+  if (NULL != sock->sock)
+  {
+    GNUNET_CONNECTION_destroy (sock->sock, finish_pending_write);
+    sock->sock = NULL;
+  }
+  if (sock->receive_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (sock->receive_task);
+    sock->receive_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  if (sock->tag != NULL)
+  {
+    GNUNET_free (sock->tag);
+    sock->tag = NULL;
+  }
+  sock->receiver_handler = NULL;
+  GNUNET_array_grow (sock->received_buf, sock->received_size, 0);
+  GNUNET_free (sock->service_name);
+  GNUNET_free (sock);
+}
+
+
+/**
+ * Check if message is complete
+ */
+static void
+check_complete (struct GNUNET_CLIENT_Connection *conn)
+{
+  if ((conn->received_pos >= sizeof (struct GNUNET_MessageHeader)) &&
+      (conn->received_pos >=
+       ntohs (((const struct GNUNET_MessageHeader *) conn->received_buf)->
+              size)))
+    conn->msg_complete = GNUNET_YES;
+}
+
+
+/**
+ * Callback function for data received from the network.  Note that
+ * both "available" and "errCode" would be 0 if the read simply timed out.
+ *
+ * @param cls closure
+ * @param buf pointer to received data
+ * @param available number of bytes availabe in "buf",
+ *        possibly 0 (on errors)
+ * @param addr address of the sender
+ * @param addrlen size of addr
+ * @param errCode value of errno (on errors receiving)
+ */
+static void
+receive_helper (void *cls, const void *buf, size_t available,
+                const struct sockaddr *addr, socklen_t addrlen, int errCode)
+{
+  struct GNUNET_CLIENT_Connection *conn = cls;
+  struct GNUNET_TIME_Relative remaining;
+  GNUNET_CLIENT_MessageHandler receive_handler;
+  void *receive_handler_cls;
+
+  GNUNET_assert (conn->msg_complete == GNUNET_NO);
+  conn->in_receive = GNUNET_NO;
+  if ((available == 0) || (conn->sock == NULL) || (errCode != 0))
+  {
+    /* signal timeout! */
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Timeout in receive_helper, available %u, conn->sock %s, errCode `%s'\n",
+         (unsigned int) available, conn->sock == NULL ? "NULL" : "non-NULL",
+         STRERROR (errCode));
+#endif
+    if (NULL != (receive_handler = conn->receiver_handler))
+    {
+      receive_handler_cls = conn->receiver_handler_cls;
+      conn->receiver_handler = NULL;
+      receive_handler (receive_handler_cls, NULL);
+    }
+    return;
+  }
+
+  /* FIXME: optimize for common fast case where buf contains the
+   * entire message and we need no copying... */
+
+
+  /* slow path: append to array */
+  if (conn->received_size < conn->received_pos + available)
+    GNUNET_array_grow (conn->received_buf, conn->received_size,
+                       conn->received_pos + available);
+  memcpy (&conn->received_buf[conn->received_pos], buf, available);
+  conn->received_pos += available;
+  check_complete (conn);
+  /* check for timeout */
+  remaining = GNUNET_TIME_absolute_get_remaining (conn->receive_timeout);
+  if (remaining.rel_value == 0)
+  {
+    /* signal timeout! */
+    if (NULL != conn->receiver_handler)
+      conn->receiver_handler (conn->receiver_handler_cls, NULL);
+    return;
+  }
+  /* back to receive -- either for more data or to call callback! */
+  GNUNET_CLIENT_receive (conn, conn->receiver_handler,
+                         conn->receiver_handler_cls, remaining);
+}
+
+
+/**
+ * Continuation to call the receive callback.
+ *
+ * @param cls  our handle to the client connection
+ * @param tc scheduler context
+ */
+static void
+receive_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_CLIENT_Connection *sock = cls;
+  GNUNET_CLIENT_MessageHandler handler = sock->receiver_handler;
+  const struct GNUNET_MessageHeader *cmsg =
+      (const struct GNUNET_MessageHeader *) sock->received_buf;
+  void *handler_cls = sock->receiver_handler_cls;
+  uint16_t msize = ntohs (cmsg->size);
+  char mbuf[msize];
+  struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) mbuf;
+
+#if DEBUG_CLIENT
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "Received message of type %u and size %u\n",
+       ntohs (cmsg->type), msize);
+#endif
+  sock->receive_task = GNUNET_SCHEDULER_NO_TASK;
+  GNUNET_assert (GNUNET_YES == sock->msg_complete);
+  GNUNET_assert (sock->received_pos >= msize);
+  memcpy (msg, cmsg, msize);
+  memmove (sock->received_buf, &sock->received_buf[msize],
+           sock->received_pos - msize);
+  sock->received_pos -= msize;
+  sock->msg_complete = GNUNET_NO;
+  sock->receiver_handler = NULL;
+  check_complete (sock);
+  if (handler != NULL)
+    handler (handler_cls, msg);
+}
+
+
+/**
+ * Read from the service.
+ *
+ * @param sock the service
+ * @param handler function to call with the message
+ * @param handler_cls closure for handler
+ * @param timeout how long to wait until timing out
+ */
+void
+GNUNET_CLIENT_receive (struct GNUNET_CLIENT_Connection *sock,
+                       GNUNET_CLIENT_MessageHandler handler, void *handler_cls,
+                       struct GNUNET_TIME_Relative timeout)
+{
+  if (sock->sock == NULL)
+  {
+    /* already disconnected, fail instantly! */
+    GNUNET_break (0);           /* this should not happen in well-written code! */
+    if (NULL != handler)
+      handler (handler_cls, NULL);
+    return;
+  }
+  sock->receiver_handler = handler;
+  sock->receiver_handler_cls = handler_cls;
+  sock->receive_timeout = GNUNET_TIME_relative_to_absolute (timeout);
+  if (GNUNET_YES == sock->msg_complete)
+  {
+    GNUNET_assert (GNUNET_SCHEDULER_NO_TASK == sock->receive_task);
+    sock->receive_task = GNUNET_SCHEDULER_add_now (&receive_task, sock);
+  }
+  else
+  {
+    GNUNET_assert (sock->in_receive == GNUNET_NO);
+    sock->in_receive = GNUNET_YES;
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "calling GNUNET_CONNECTION_receive\n");
+#endif
+    GNUNET_CONNECTION_receive (sock->sock, GNUNET_SERVER_MAX_MESSAGE_SIZE - 1,
+                               timeout, &receive_helper, sock);
+  }
+}
+
+
+/**
+ * Report service unavailable.
+ */
+static void
+service_test_error (GNUNET_SCHEDULER_Task task, void *task_cls)
+{
+  GNUNET_SCHEDULER_add_continuation (task, task_cls,
+                                     GNUNET_SCHEDULER_REASON_TIMEOUT);
+}
+
+
+/**
+ * Receive confirmation from test, service is up.
+ *
+ * @param cls closure
+ * @param msg message received, NULL on timeout or fatal error
+ */
+static void
+confirm_handler (void *cls, const struct GNUNET_MessageHeader *msg)
+{
+  struct GNUNET_CLIENT_Connection *conn = cls;
+
+  /* We may want to consider looking at the reply in more
+   * detail in the future, for example, is this the
+   * correct service? FIXME! */
+  if (msg != NULL)
+  {
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Received confirmation that service is running.\n");
+#endif
+    GNUNET_SCHEDULER_add_continuation (conn->test_cb, conn->test_cb_cls,
+                                       GNUNET_SCHEDULER_REASON_PREREQ_DONE);
+  }
+  else
+  {
+    service_test_error (conn->test_cb, conn->test_cb_cls);
+  }
+  GNUNET_CLIENT_disconnect (conn, GNUNET_NO);
+}
+
+
+/**
+ * Send the 'TEST' message to the service.  If successful, prepare to
+ * receive the reply.
+ *
+ * @param cls the 'struct GNUNET_CLIENT_Connection' of the connection to test
+ * @param size number of bytes available in buf
+ * @param buf where to write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+write_test (void *cls, size_t size, void *buf)
+{
+  struct GNUNET_CLIENT_Connection *conn = cls;
+  struct GNUNET_MessageHeader *msg;
+
+  if (size < sizeof (struct GNUNET_MessageHeader))
+  {
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG, _("Failure to transmit TEST request.\n"));
+#endif
+    service_test_error (conn->test_cb, conn->test_cb_cls);
+    GNUNET_CLIENT_disconnect (conn, GNUNET_NO);
+    return 0;                   /* client disconnected */
+  }
+#if DEBUG_CLIENT
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "Transmitting `%s' request.\n", "TEST");
+#endif
+  msg = (struct GNUNET_MessageHeader *) buf;
+  msg->type = htons (GNUNET_MESSAGE_TYPE_TEST);
+  msg->size = htons (sizeof (struct GNUNET_MessageHeader));
+  GNUNET_CLIENT_receive (conn, &confirm_handler, conn,
+                         GNUNET_TIME_absolute_get_remaining
+                         (conn->test_deadline));
+  return sizeof (struct GNUNET_MessageHeader);
+}
+
+
+/**
+ * Test if the service is running.  If we are given a UNIXPATH or a local address,
+ * we do this NOT by trying to connect to the service, but by trying to BIND to
+ * the same port.  If the BIND fails, we know the service is running.
+ *
+ * @param service name of the service to wait for
+ * @param cfg configuration to use
+ * @param timeout how long to wait at most
+ * @param task task to run if service is running
+ *        (reason will be "PREREQ_DONE" (service running)
+ *         or "TIMEOUT" (service not known to be running))
+ * @param task_cls closure for task
+ */
+void
+GNUNET_CLIENT_service_test (const char *service,
+                            const struct GNUNET_CONFIGURATION_Handle *cfg,
+                            struct GNUNET_TIME_Relative timeout,
+                            GNUNET_SCHEDULER_Task task, void *task_cls)
+{
+  char *hostname;
+  unsigned long long port;
+  struct GNUNET_NETWORK_Handle *sock;
+  struct GNUNET_CLIENT_Connection *conn;
+
+#if DEBUG_CLIENT
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "Testing if service `%s' is running.\n",
+       service);
+#endif
+#ifdef AF_UNIX
+  {
+    /* probe UNIX support */
+    struct sockaddr_un s_un;
+    size_t slen;
+    char *unixpath;
+
+    unixpath = NULL;
+    if ((GNUNET_OK == GNUNET_CONFIGURATION_get_value_string (cfg, service, "UNIXPATH", &unixpath)) && (0 < strlen (unixpath)))  /* We have a non-NULL unixpath, does that mean it's valid? */
+    {
+      if (strlen (unixpath) >= sizeof (s_un.sun_path))
+      {
+        LOG (GNUNET_ERROR_TYPE_WARNING,
+             _("UNIXPATH `%s' too long, maximum length is %llu\n"), unixpath,
+             sizeof (s_un.sun_path));
+      }
+      else
+      {
+        sock = GNUNET_NETWORK_socket_create (PF_UNIX, SOCK_STREAM, 0);
+        if (sock != NULL)
+        {
+          memset (&s_un, 0, sizeof (s_un));
+          s_un.sun_family = AF_UNIX;
+          slen = strlen (unixpath) + 1;
+          if (slen >= sizeof (s_un.sun_path))
+            slen = sizeof (s_un.sun_path) - 1;
+          memcpy (s_un.sun_path, unixpath, slen);
+          s_un.sun_path[slen] = '\0';
+          slen = sizeof (struct sockaddr_un);
+#if LINUX
+          s_un.sun_path[0] = '\0';
+#endif
+#if HAVE_SOCKADDR_IN_SIN_LEN
+          s_un.sun_len = (u_char) slen;
+#endif
+          if (GNUNET_OK !=
+              GNUNET_NETWORK_socket_bind (sock, (const struct sockaddr *) &s_un,
+                                          slen))
+          {
+            /* failed to bind => service must be running */
+            GNUNET_free (unixpath);
+            (void) GNUNET_NETWORK_socket_close (sock);
+            GNUNET_SCHEDULER_add_continuation (task, task_cls,
+                                               GNUNET_SCHEDULER_REASON_PREREQ_DONE);
+            return;
+          }
+          (void) GNUNET_NETWORK_socket_close (sock);
+        }
+        /* let's try IP */
+      }
+    }
+    GNUNET_free_non_null (unixpath);
+  }
+#endif
+
+  hostname = NULL;
+  if ((GNUNET_OK !=
+       GNUNET_CONFIGURATION_get_value_number (cfg, service, "PORT", &port)) ||
+      (port > 65535) ||
+      (GNUNET_OK !=
+       GNUNET_CONFIGURATION_get_value_string (cfg, service, "HOSTNAME",
+                                              &hostname)))
+  {
+    /* UNIXPATH failed (if possible) AND IP failed => error */
+    service_test_error (task, task_cls);
+    return;
+  }
+
+  if (0 == strcmp ("localhost", hostname)
+#if !LINUX
+      && 0
+#endif
+      )
+  {
+    /* can test using 'bind' */
+    struct sockaddr_in s_in;
+
+    memset (&s_in, 0, sizeof (s_in));
+#if HAVE_SOCKADDR_IN_SIN_LEN
+    s_in.sin_len = sizeof (struct sockaddr_in);
+#endif
+    s_in.sin_family = AF_INET;
+    s_in.sin_port = htons (port);
+
+    sock = GNUNET_NETWORK_socket_create (AF_INET, SOCK_STREAM, 0);
+    if (sock != NULL)
+    {
+      if (GNUNET_OK !=
+          GNUNET_NETWORK_socket_bind (sock, (const struct sockaddr *) &s_in,
+                                      sizeof (s_in)))
+      {
+        /* failed to bind => service must be running */
+        GNUNET_free (hostname);
+        (void) GNUNET_NETWORK_socket_close (sock);
+        GNUNET_SCHEDULER_add_continuation (task, task_cls,
+                                           GNUNET_SCHEDULER_REASON_PREREQ_DONE);
+        return;
+      }
+      (void) GNUNET_NETWORK_socket_close (sock);
+    }
+  }
+
+  if (0 == strcmp ("ip6-localhost", hostname)
+#if !LINUX
+      && 0
+#endif
+      )
+  {
+    /* can test using 'bind' */
+    struct sockaddr_in6 s_in6;
+
+    memset (&s_in6, 0, sizeof (s_in6));
+#if HAVE_SOCKADDR_IN_SIN_LEN
+    s_in6.sin6_len = sizeof (struct sockaddr_in6);
+#endif
+    s_in6.sin6_family = AF_INET6;
+    s_in6.sin6_port = htons (port);
+
+    sock = GNUNET_NETWORK_socket_create (AF_INET6, SOCK_STREAM, 0);
+    if (sock != NULL)
+    {
+      if (GNUNET_OK !=
+          GNUNET_NETWORK_socket_bind (sock, (const struct sockaddr *) &s_in6,
+                                      sizeof (s_in6)))
+      {
+        /* failed to bind => service must be running */
+        GNUNET_free (hostname);
+        (void) GNUNET_NETWORK_socket_close (sock);
+        GNUNET_SCHEDULER_add_continuation (task, task_cls,
+                                           GNUNET_SCHEDULER_REASON_PREREQ_DONE);
+        return;
+      }
+      (void) GNUNET_NETWORK_socket_close (sock);
+    }
+  }
+
+  if (((0 == strcmp ("localhost", hostname)) ||
+       (0 == strcmp ("ip6-localhost", hostname)))
+#if !LINUX
+      && 0
+#endif
+      )
+  {
+    /* all binds succeeded => claim service not running right now */
+    GNUNET_free_non_null (hostname);
+    service_test_error (task, task_cls);
+    return;
+  }
+  GNUNET_free_non_null (hostname);
+
+  /* non-localhost, try 'connect' method */
+  conn = GNUNET_CLIENT_connect (service, cfg);
+  if (conn == NULL)
+  {
+    LOG (GNUNET_ERROR_TYPE_INFO,
+         _("Could not connect to service `%s', must not be running.\n"),
+         service);
+    service_test_error (task, task_cls);
+    return;
+  }
+  conn->test_cb = task;
+  conn->test_cb_cls = task_cls;
+  conn->test_deadline = GNUNET_TIME_relative_to_absolute (timeout);
+
+  if (NULL ==
+      GNUNET_CLIENT_notify_transmit_ready (conn,
+                                           sizeof (struct GNUNET_MessageHeader),
+                                           timeout, GNUNET_YES, &write_test,
+                                           conn))
+  {
+    LOG (GNUNET_ERROR_TYPE_WARNING,
+         _("Failure to transmit request to service `%s'\n"), service);
+    service_test_error (task, task_cls);
+    GNUNET_CLIENT_disconnect (conn, GNUNET_NO);
+    return;
+  }
+}
+
+
+/**
+ * Connection notifies us about failure or success of
+ * a transmission request.  Either pass it on to our
+ * user or, if possible, retry.
+ *
+ * @param cls our "struct GNUNET_CLIENT_TransmissionHandle"
+ * @param size number of bytes available for transmission
+ * @param buf where to write them
+ * @return number of bytes written to buf
+ */
+static size_t
+client_notify (void *cls, size_t size, void *buf);
+
+
+/**
+ * This task is run if we should re-try connection to the
+ * service after a while.
+ *
+ * @param cls our "struct GNUNET_CLIENT_TransmitHandle" of the request
+ * @param tc unused
+ */
+static void
+client_delayed_retry (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_CLIENT_TransmitHandle *th = cls;
+  struct GNUNET_TIME_Relative delay;
+
+  th->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
+  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+  {
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "Transmission failed due to shutdown.\n");
+#endif
+    th->sock->th = NULL;
+    th->notify (th->notify_cls, 0, NULL);
+    GNUNET_free (th);
+    return;
+  }
+  th->sock->sock =
+      do_connect (th->sock->service_name, th->sock->cfg, th->sock->attempts++);
+  if (NULL == th->sock->sock)
+  {
+    /* could happen if we're out of sockets */
+    delay =
+        GNUNET_TIME_relative_min (GNUNET_TIME_absolute_get_remaining
+                                  (th->timeout), th->sock->back_off);
+    th->sock->back_off =
+        GNUNET_TIME_relative_min (GNUNET_TIME_relative_multiply
+                                  (th->sock->back_off, 2),
+                                  GNUNET_TIME_UNIT_SECONDS);
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Transmission failed %u times, trying again in %llums.\n",
+         MAX_ATTEMPTS - th->attempts_left,
+         (unsigned long long) delay.rel_value);
+#endif
+    th->reconnect_task =
+        GNUNET_SCHEDULER_add_delayed (delay, &client_delayed_retry, th);
+    return;
+  }
+  th->th =
+      GNUNET_CONNECTION_notify_transmit_ready (th->sock->sock, th->size,
+                                               GNUNET_TIME_absolute_get_remaining
+                                               (th->timeout), &client_notify,
+                                               th);
+  if (th->th == NULL)
+  {
+    GNUNET_break (0);
+    th->sock->th = NULL;
+    th->notify (th->notify_cls, 0, NULL);
+    GNUNET_free (th);
+    return;
+  }
+}
+
+
+/**
+ * Connection notifies us about failure or success of a transmission
+ * request.  Either pass it on to our user or, if possible, retry.
+ *
+ * @param cls our "struct GNUNET_CLIENT_TransmissionHandle"
+ * @param size number of bytes available for transmission
+ * @param buf where to write them
+ * @return number of bytes written to buf
+ */
+static size_t
+client_notify (void *cls, size_t size, void *buf)
+{
+  struct GNUNET_CLIENT_TransmitHandle *th = cls;
+  size_t ret;
+  struct GNUNET_TIME_Relative delay;
+
+  th->th = NULL;
+  th->sock->th = NULL;
+  if (buf == NULL)
+  {
+    delay = GNUNET_TIME_absolute_get_remaining (th->timeout);
+    delay.rel_value /= 2;
+    if ((0 !=
+         (GNUNET_SCHEDULER_REASON_SHUTDOWN & GNUNET_SCHEDULER_get_reason ())) ||
+        (GNUNET_YES != th->auto_retry) || (0 == --th->attempts_left) ||
+        (delay.rel_value < 1))
+    {
+#if DEBUG_CLIENT
+      LOG (GNUNET_ERROR_TYPE_DEBUG,
+           "Transmission failed %u times, giving up.\n",
+           MAX_ATTEMPTS - th->attempts_left);
+#endif
+      GNUNET_break (0 == th->notify (th->notify_cls, 0, NULL));
+      GNUNET_free (th);
+      return 0;
+    }
+    /* auto-retry */
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Failed to connect to `%s', automatically trying again.\n",
+         th->sock->service_name);
+#endif
+    GNUNET_CONNECTION_destroy (th->sock->sock, GNUNET_NO);
+    th->sock->sock = NULL;
+    delay = GNUNET_TIME_relative_min (delay, th->sock->back_off);
+    th->sock->back_off =
+        GNUNET_TIME_relative_min (GNUNET_TIME_relative_multiply
+                                  (th->sock->back_off, 2),
+                                  GNUNET_TIME_UNIT_SECONDS);
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Transmission failed %u times, trying again in %llums.\n",
+         MAX_ATTEMPTS - th->attempts_left,
+         (unsigned long long) delay.rel_value);
+#endif
+    th->sock->th = th;
+    th->reconnect_task =
+        GNUNET_SCHEDULER_add_delayed (delay, &client_delayed_retry, th);
+    return 0;
+  }
+  GNUNET_assert (size >= th->size);
+  ret = th->notify (th->notify_cls, size, buf);
+  GNUNET_free (th);
+  return ret;
+}
+
+
+/**
+ * Ask the client to call us once the specified number of bytes
+ * are free in the transmission buffer.  May call the notify
+ * method immediately if enough space is available.
+ *
+ * @param sock connection to the service
+ * @param size number of bytes to send
+ * @param timeout after how long should we give up (and call
+ *        notify with buf NULL and size 0)?
+ * @param auto_retry if the connection to the service dies, should we
+ *        automatically re-connect and retry (within the timeout period)
+ *        or should we immediately fail in this case?  Pass GNUNET_YES
+ *        if the caller does not care about temporary connection errors,
+ *        for example because the protocol is stateless
+ * @param notify function to call
+ * @param notify_cls closure for notify
+ * @return NULL if our buffer will never hold size bytes,
+ *         a handle if the notify callback was queued (can be used to cancel)
+ */
+struct GNUNET_CLIENT_TransmitHandle *
+GNUNET_CLIENT_notify_transmit_ready (struct GNUNET_CLIENT_Connection *sock,
+                                     size_t size,
+                                     struct GNUNET_TIME_Relative timeout,
+                                     int auto_retry,
+                                     GNUNET_CONNECTION_TransmitReadyNotify
+                                     notify, void *notify_cls)
+{
+  struct GNUNET_CLIENT_TransmitHandle *th;
+
+  if (NULL != sock->th)
+  {
+    /* If this breaks, you most likley called this function twice without waiting
+     * for completion or canceling the request */
+    GNUNET_break (0);
+    return NULL;
+  }
+  th = GNUNET_malloc (sizeof (struct GNUNET_CLIENT_TransmitHandle));
+  th->sock = sock;
+  th->size = size;
+  th->timeout = GNUNET_TIME_relative_to_absolute (timeout);
+  th->auto_retry = auto_retry;
+  th->notify = notify;
+  th->notify_cls = notify_cls;
+  th->attempts_left = MAX_ATTEMPTS;
+  sock->th = th;
+  if (sock->sock == NULL)
+  {
+    th->reconnect_task =
+        GNUNET_SCHEDULER_add_delayed (sock->back_off, &client_delayed_retry,
+                                      th);
+
+  }
+  else
+  {
+    th->th =
+        GNUNET_CONNECTION_notify_transmit_ready (sock->sock, size, timeout,
+                                                 &client_notify, th);
+    if (NULL == th->th)
+    {
+      GNUNET_break (0);
+      GNUNET_free (th);
+      sock->th = NULL;
+      return NULL;
+    }
+  }
+  return th;
+}
+
+
+/**
+ * Cancel a request for notification.
+ *
+ * @param th handle from the original request.
+ */
+void
+GNUNET_CLIENT_notify_transmit_ready_cancel (struct GNUNET_CLIENT_TransmitHandle
+                                            *th)
+{
+  if (th->reconnect_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_assert (NULL == th->th);
+    GNUNET_SCHEDULER_cancel (th->reconnect_task);
+    th->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  else
+  {
+    GNUNET_assert (NULL != th->th);
+    GNUNET_CONNECTION_notify_transmit_ready_cancel (th->th);
+  }
+  th->sock->th = NULL;
+  GNUNET_free (th);
+}
+
+
+/**
+ * Function called to notify a client about the socket
+ * begin ready to queue the message.  "buf" will be
+ * NULL and "size" zero if the socket was closed for
+ * writing in the meantime.
+ *
+ * @param cls closure of type "struct TransmitGetResponseContext*"
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_for_response (void *cls, size_t size, void *buf)
+{
+  struct TransmitGetResponseContext *tc = cls;
+  uint16_t msize;
+
+  tc->sock->tag = NULL;
+  msize = ntohs (tc->hdr->size);
+  if (NULL == buf)
+  {
+#if DEBUG_CLIENT
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         _("Could not submit request, not expecting to receive a response.\n"));
+#endif
+    if (NULL != tc->rn)
+      tc->rn (tc->rn_cls, NULL);
+    GNUNET_free (tc);
+    return 0;
+  }
+  GNUNET_assert (size >= msize);
+  memcpy (buf, tc->hdr, msize);
+  GNUNET_CLIENT_receive (tc->sock, tc->rn, tc->rn_cls,
+                         GNUNET_TIME_absolute_get_remaining (tc->timeout));
+  GNUNET_free (tc);
+  return msize;
+}
+
+
+/**
+ * Convenience API that combines sending a request
+ * to the service and waiting for a response.
+ * If either operation times out, the callback
+ * will be called with a "NULL" response (in which
+ * case the connection should probably be destroyed).
+ *
+ * @param sock connection to use
+ * @param hdr message to transmit
+ * @param timeout when to give up (for both transmission
+ *         and for waiting for a response)
+ * @param auto_retry if the connection to the service dies, should we
+ *        automatically re-connect and retry (within the timeout period)
+ *        or should we immediately fail in this case?  Pass GNUNET_YES
+ *        if the caller does not care about temporary connection errors,
+ *        for example because the protocol is stateless
+ * @param rn function to call with the response
+ * @param rn_cls closure for rn
+ * @return GNUNET_OK on success, GNUNET_SYSERR if a request
+ *         is already pending
+ */
+int
+GNUNET_CLIENT_transmit_and_get_response (struct GNUNET_CLIENT_Connection *sock,
+                                         const struct GNUNET_MessageHeader *hdr,
+                                         struct GNUNET_TIME_Relative timeout,
+                                         int auto_retry,
+                                         GNUNET_CLIENT_MessageHandler rn,
+                                         void *rn_cls)
+{
+  struct TransmitGetResponseContext *tc;
+  uint16_t msize;
+
+  if (NULL != sock->th)
+    return GNUNET_SYSERR;
+  GNUNET_assert (sock->tag == NULL);
+  msize = ntohs (hdr->size);
+  tc = GNUNET_malloc (sizeof (struct TransmitGetResponseContext) + msize);
+  tc->sock = sock;
+  tc->hdr = (const struct GNUNET_MessageHeader *) &tc[1];
+  memcpy (&tc[1], hdr, msize);
+  tc->timeout = GNUNET_TIME_relative_to_absolute (timeout);
+  tc->rn = rn;
+  tc->rn_cls = rn_cls;
+  if (NULL ==
+      GNUNET_CLIENT_notify_transmit_ready (sock, msize, timeout, auto_retry,
+                                           &transmit_for_response, tc))
+  {
+    GNUNET_break (0);
+    GNUNET_free (tc);
+    return GNUNET_SYSERR;
+  }
+  sock->tag = tc;
+  return GNUNET_OK;
+}
+
+
+
+/*  end of client.c */