src/util/client.c

   1 /*
   2      This file is part of GNUnet.
   3      Copyright (C) 2001-2016 GNUnet e.V.
   4
   5      GNUnet is free software; you can redistribute it and/or modify
   6      it under the terms of the GNU General Public License as published
   7      by the Free Software Foundation; either version 3, or (at your
   8      option) any later version.
   9
  10      GNUnet is distributed in the hope that it will be useful, but
  11      WITHOUT ANY WARRANTY; without even the implied warranty of
  12      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13      General Public License for more details.
  14
  15      You should have received a copy of the GNU General Public License
  16      along with GNUnet; see the file COPYING.  If not, write to the
  17      Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  18      Boston, MA 02110-1301, USA.
  19 */
  20
  21 /**
  22  * @file util/client.c
  23  * @brief code for access to services
  24  * @author Christian Grothoff
  25  *
  26  * Generic TCP code for reliable, record-oriented TCP
  27  * connections between clients and service providers.
  28  */
  29 #include "platform.h"
  30 #include "gnunet_protocols.h"
  31 #include "gnunet_util_lib.h"
  32 #include "gnunet_resolver_service.h"
  33 #include "gnunet_socks.h"
  34
  35
  36 #define LOG(kind,...) GNUNET_log_from (kind, "util-client",__VA_ARGS__)
  37
  38 /**
  39  * Timeout we use on TCP connect before trying another
  40  * result from the DNS resolver.  Actual value used
  41  * is this value divided by the number of address families.
  42  * Default is 5s.
  43  */
  44 #define CONNECT_RETRY_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 5)
  45
  46
  47
  48 /**
  49  * Internal state for a client connected to a GNUnet service.
  50  */
  51 struct ClientState;
  52
  53
  54 /**
  55  * During connect, we try multiple possible IP addresses
  56  * to find out which one might work.
  57  */
  58 struct AddressProbe
  59 {
  60
  61   /**
  62    * This is a linked list.
  63    */
  64   struct AddressProbe *next;
  65
  66   /**
  67    * This is a doubly-linked list.
  68    */
  69   struct AddressProbe *prev;
  70
  71   /**
  72    * The address; do not free (allocated at the end of this struct).
  73    */
  74   const struct sockaddr *addr;
  75
  76   /**
  77    * Underlying OS's socket.
  78    */
  79   struct GNUNET_NETWORK_Handle *sock;
  80
  81   /**
  82    * Connection for which we are probing.
  83    */
  84   struct ClientState *cstate;
  85
  86   /**
  87    * Lenth of addr.
  88    */
  89   socklen_t addrlen;
  90
  91   /**
  92    * Task waiting for the connection to finish connecting.
  93    */
  94   struct GNUNET_SCHEDULER_Task *task;
  95 };
  96
  97
  98 /**
  99  * Internal state for a client connected to a GNUnet service.
 100  */
 101 struct ClientState
 102 {
 103
 104   /**
 105    * The connection handle, NULL if not live
 106    */
 107   struct GNUNET_NETWORK_Handle *sock;
 108
 109   /**
 110    * Handle to a pending DNS lookup request, NULL if DNS is finished.
 111    */
 112   struct GNUNET_RESOLVER_RequestHandle *dns_active;
 113
 114   /**
 115    * Our configuration.
 116    */
 117   const struct GNUNET_CONFIGURATION_Handle *cfg;
 118
 119   /**
 120    * Linked list of sockets we are currently trying out
 121    * (during connect).
 122    */
 123   struct AddressProbe *ap_head;
 124
 125   /**
 126    * Linked list of sockets we are currently trying out
 127    * (during connect).
 128    */
 129   struct AddressProbe *ap_tail;
 130
 131   /**
 132    * Name of the service we interact with.
 133    */
 134   char *service_name;
 135
 136   /**
 137    * Hostname, if any.
 138    */
 139   char *hostname;
 140
 141   /**
 142    * Next message to transmit to the service. NULL for none.
 143    */
 144   const struct GNUNET_MessageHeader *msg;
 145
 146   /**
 147    * Task for trying to connect to the service.
 148    */
 149   struct GNUNET_SCHEDULER_Task *retry_task;
 150
 151   /**
 152    * Task for sending messages to the service.
 153    */
 154   struct GNUNET_SCHEDULER_Task *send_task;
 155
 156   /**
 157    * Task for sending messages to the service.
 158    */
 159   struct GNUNET_SCHEDULER_Task *recv_task;
 160
 161   /**
 162    * Tokenizer for inbound messages.
 163    */
 164   struct GNUNET_MessageStreamTokenizer *mst;
 165
 166   /**
 167    * Message queue under our control.
 168    */
 169   struct GNUNET_MQ_Handle *mq;
 170
 171   /**
 172    * Timeout for receiving a response (absolute time).
 173    */
 174   struct GNUNET_TIME_Absolute receive_timeout;
 175
 176   /**
 177    * Current value for our incremental back-off (for
 178    * connect re-tries).
 179    */
 180   struct GNUNET_TIME_Relative back_off;
 181
 182   /**
 183    * TCP port (0 for disabled).
 184    */
 185   unsigned long long port;
 186
 187   /**
 188    * Offset in the message where we are for transmission.
 189    */
 190   size_t msg_off;
 191
 192   /**
 193    * How often have we tried to connect?
 194    */
 195   unsigned int attempts;
 196
 197   /**
 198    * Are we supposed to die?  #GNUNET_SYSERR if destruction must be
 199    * deferred, #GNUNET_NO by default, #GNUNET_YES if destruction was
 200    * deferred.
 201    */
 202   int in_destroy;
 203
 204 };
 205
 206
 207 /**
 208  * Try to connect to the service.
 209  *
 210  * @param cls the `struct ClientState` to try to connect to the service
 211  */
 212 static void
 213 start_connect (void *cls);
 214
 215
 216 /**
 217  * We've failed for good to establish a connection (timeout or
 218  * no more addresses to try).
 219  *
 220  * @param cstate the connection we tried to establish
 221  */
 222 static void
 223 connect_fail_continuation (struct ClientState *cstate)
 224 {
 225   GNUNET_break (NULL == cstate->ap_head);
 226   GNUNET_break (NULL == cstate->ap_tail);
 227   GNUNET_break (NULL == cstate->dns_active);
 228   GNUNET_break (NULL == cstate->sock);
 229   GNUNET_assert (NULL == cstate->send_task);
 230   GNUNET_assert (NULL == cstate->recv_task);
 231   // GNUNET_assert (NULL == cstate->proxy_handshake);
 232
 233   cstate->back_off = GNUNET_TIME_STD_BACKOFF (cstate->back_off);
 234   LOG (GNUNET_ERROR_TYPE_DEBUG,
 235        "Failed to establish connection to `%s', no further addresses to try, will try again in %s.\n",
 236        cstate->service_name,
 237        GNUNET_STRINGS_relative_time_to_string (cstate->back_off,
 238                                                GNUNET_YES));
 239   cstate->retry_task
 240     = GNUNET_SCHEDULER_add_delayed (cstate->back_off,
 241                                     &start_connect,
 242                                     cstate);
 243 }
 244
 245
 246 /**
 247  * We are ready to send a message to the service.
 248  *
 249  * @param cls the `struct ClientState` with the `msg` to transmit
 250  */
 251 static void
 252 transmit_ready (void *cls)
 253 {
 254   struct ClientState *cstate = cls;
 255   ssize_t ret;
 256   size_t len;
 257   const char *pos;
 258   int notify_in_flight;
 259
 260   cstate->send_task = NULL;
 261   pos = (const char *) cstate->msg;
 262   len = ntohs (cstate->msg->size);
 263   GNUNET_assert (cstate->msg_off < len);
 264   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 265               "client: message of type %u trying to send with socket %p (MQ: %p\n",
 266               ntohs(cstate->msg->type),
 267               cstate->sock,
 268               cstate->mq);
 269
 270  RETRY:
 271   ret = GNUNET_NETWORK_socket_send (cstate->sock,
 272                                     &pos[cstate->msg_off],
 273                                     len - cstate->msg_off);
 274   if (-1 == ret)
 275   {
 276     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 277                 "client: error during sending message of type %u\n",
 278                 ntohs(cstate->msg->type));
 279     if (EINTR == errno){
 280       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 281                   "client: retrying message of type %u\n",
 282                   ntohs(cstate->msg->type));
 283       goto RETRY;
 284     }
 285     GNUNET_MQ_inject_error (cstate->mq,
 286                             GNUNET_MQ_ERROR_WRITE);
 287     return;
 288   }
 289   notify_in_flight = (0 == cstate->msg_off);
 290   cstate->msg_off += ret;
 291   if (cstate->msg_off < len)
 292   {
 293     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 294                 "client: rescheduling message of type %u\n",
 295                 ntohs(cstate->msg->type));
 296     cstate->send_task
 297       = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 298                                         cstate->sock,
 299                                         &transmit_ready,
 300                                         cstate);
 301     if (notify_in_flight)
 302       GNUNET_MQ_impl_send_in_flight (cstate->mq);
 303     return;
 304   }
 305   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 306               "client: sending message of type %u successful\n",
 307               ntohs(cstate->msg->type));
 308   cstate->msg = NULL;
 309   GNUNET_MQ_impl_send_continue (cstate->mq);
 310 }
 311
 312
 313 /**
 314  * We have received a full message, pass to the MQ dispatcher.
 315  * Called by the tokenizer via #receive_ready().
 316  *
 317  * @param cls the `struct ClientState`
 318  * @param msg message we received.
 319  * @return #GNUNET_OK on success,
 320  *     #GNUNET_NO to stop further processing due to disconnect (no error)
 321  *     #GNUNET_SYSERR to stop further processing due to error
 322  */
 323 static int
 324 recv_message (void *cls,
 325               const struct GNUNET_MessageHeader *msg)
 326 {
 327   struct ClientState *cstate = cls;
 328
 329   if (GNUNET_YES == cstate->in_destroy)
 330     return GNUNET_NO;
 331   LOG (GNUNET_ERROR_TYPE_DEBUG,
 332        "Received message of type %u and size %u from %s\n",
 333        ntohs (msg->type),
 334        ntohs (msg->size),
 335        cstate->service_name);
 336   GNUNET_MQ_inject_message (cstate->mq,
 337                             msg);
 338   if (GNUNET_YES == cstate->in_destroy)
 339     return GNUNET_NO;
 340   return GNUNET_OK;
 341 }
 342
 343
 344 /**
 345  * Cancel all remaining connect attempts
 346  *
 347  * @param cstate handle of the client state to process
 348  */
 349 static void
 350 cancel_aps (struct ClientState *cstate)
 351 {
 352   struct AddressProbe *pos;
 353
 354   while (NULL != (pos = cstate->ap_head))
 355   {
 356     GNUNET_break (GNUNET_OK ==
 357                   GNUNET_NETWORK_socket_close (pos->sock));
 358     GNUNET_SCHEDULER_cancel (pos->task);
 359     GNUNET_CONTAINER_DLL_remove (cstate->ap_head,
 360                                  cstate->ap_tail,
 361                                  pos);
 362     GNUNET_free (pos);
 363   }
 364 }
 365
 366
 367 /**
 368  * Implement the destruction of a message queue.  Implementations must
 369  * not free @a mq, but should take care of @a impl_state.
 370  *
 371  * @param mq the message queue to destroy
 372  * @param impl_state our `struct ClientState`
 373  */
 374 static void
 375 connection_client_destroy_impl (struct GNUNET_MQ_Handle *mq,
 376                                 void *impl_state)
 377 {
 378   struct ClientState *cstate = impl_state;
 379
 380   (void) mq;
 381   if (GNUNET_SYSERR == cstate->in_destroy)
 382   {
 383     /* defer destruction */
 384     cstate->in_destroy = GNUNET_YES;
 385     cstate->mq = NULL;
 386     return;
 387   }
 388   if (NULL != cstate->dns_active)
 389     GNUNET_RESOLVER_request_cancel (cstate->dns_active);
 390   if (NULL != cstate->send_task)
 391     GNUNET_SCHEDULER_cancel (cstate->send_task);
 392   if (NULL != cstate->recv_task)
 393     GNUNET_SCHEDULER_cancel (cstate->recv_task);
 394   if (NULL != cstate->retry_task)
 395     GNUNET_SCHEDULER_cancel (cstate->retry_task);
 396   if (NULL != cstate->sock){
 397     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 398                 "client: destroying socket: %p\n",
 399                 cstate->sock);
 400     GNUNET_NETWORK_socket_close (cstate->sock);
 401   }
 402   cancel_aps (cstate);
 403   GNUNET_free (cstate->service_name);
 404   GNUNET_free_non_null (cstate->hostname);
 405   GNUNET_MST_destroy (cstate->mst);
 406   GNUNET_free (cstate);
 407 }
 408
 409
 410 /**
 411  * This function is called once we have data ready to read.
 412  *
 413  * @param cls `struct ClientState` with connection to read from
 414  */
 415 static void
 416 receive_ready (void *cls)
 417 {
 418   struct ClientState *cstate = cls;
 419   int ret;
 420
 421   cstate->recv_task = NULL;
 422   cstate->in_destroy = GNUNET_SYSERR;
 423   ret = GNUNET_MST_read (cstate->mst,
 424                          cstate->sock,
 425                          GNUNET_NO,
 426                          GNUNET_NO);
 427   if (GNUNET_SYSERR == ret)
 428   {
 429     if (NULL != cstate->mq)
 430       GNUNET_MQ_inject_error (cstate->mq,
 431                               GNUNET_MQ_ERROR_READ);
 432     if (GNUNET_YES == cstate->in_destroy)
 433       connection_client_destroy_impl (cstate->mq,
 434                                       cstate);
 435     return;
 436   }
 437   if (GNUNET_YES == cstate->in_destroy)
 438   {
 439     connection_client_destroy_impl (cstate->mq,
 440                                     cstate);
 441     return;
 442   }
 443   cstate->in_destroy = GNUNET_NO;
 444   cstate->recv_task
 445     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 446                                      cstate->sock,
 447                                      &receive_ready,
 448                                      cstate);
 449 }
 450
 451
 452 /**
 453  * We've succeeded in establishing a connection.
 454  *
 455  * @param cstate the connection we tried to establish
 456  */
 457 static void
 458 connect_success_continuation (struct ClientState *cstate)
 459 {
 460   GNUNET_assert (NULL == cstate->recv_task);
 461   cstate->recv_task
 462     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 463                                      cstate->sock,
 464                                      &receive_ready,
 465                                      cstate);
 466   if (NULL != cstate->msg)
 467   {
 468     GNUNET_assert (NULL == cstate->send_task);
 469     cstate->send_task
 470       = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 471                                         cstate->sock,
 472                                         &transmit_ready,
 473                                         cstate);
 474   }
 475 }
 476
 477
 478 /**
 479  * Try connecting to the server using UNIX domain sockets.
 480  *
 481  * @param service_name name of service to connect to
 482  * @param cfg configuration to use
 483  * @return NULL on error, socket connected to UNIX otherwise
 484  */
 485 static struct GNUNET_NETWORK_Handle *
 486 try_unixpath (const char *service_name,
 487               const struct GNUNET_CONFIGURATION_Handle *cfg)
 488 {
 489 #if AF_UNIX
 490   struct GNUNET_NETWORK_Handle *sock;
 491   char *unixpath;
 492   struct sockaddr_un s_un;
 493
 494   unixpath = NULL;
 495   if ((GNUNET_OK ==
 496        GNUNET_CONFIGURATION_get_value_filename (cfg,
 497                                                 service_name,
 498                                                 "UNIXPATH",
 499                                                 &unixpath)) &&
 500       (0 < strlen (unixpath)))
 501   {
 502     /* We have a non-NULL unixpath, need to validate it */
 503     if (strlen (unixpath) >= sizeof (s_un.sun_path))
 504     {
 505       LOG (GNUNET_ERROR_TYPE_WARNING,
 506            _("UNIXPATH `%s' too long, maximum length is %llu\n"),
 507            unixpath,
 508            (unsigned long long) sizeof (s_un.sun_path));
 509       unixpath = GNUNET_NETWORK_shorten_unixpath (unixpath);
 510       LOG (GNUNET_ERROR_TYPE_INFO,
 511            _("Using `%s' instead\n"),
 512            unixpath);
 513       if (NULL == unixpath)
 514         return NULL;
 515     }
 516     memset (&s_un,
 517             0,
 518             sizeof (s_un));
 519     s_un.sun_family = AF_UNIX;
 520     strncpy (s_un.sun_path,
 521              unixpath,
 522              sizeof (s_un.sun_path) - 1);
 523 #ifdef LINUX
 524     {
 525       int abstract;
 526
 527       abstract = GNUNET_CONFIGURATION_get_value_yesno (cfg,
 528                                                        "TESTING",
 529                                                        "USE_ABSTRACT_SOCKETS");
 530       if (GNUNET_YES == abstract)
 531         s_un.sun_path[0] = '\0';
 532     }
 533 #endif
 534 #if HAVE_SOCKADDR_UN_SUN_LEN
 535     s_un.sun_len = (u_char) sizeof (struct sockaddr_un);
 536 #endif
 537     sock = GNUNET_NETWORK_socket_create (AF_UNIX,
 538                                          SOCK_STREAM,
 539                                          0);
 540     if ( (NULL != sock) &&
 541          ( (GNUNET_OK ==
 542             GNUNET_NETWORK_socket_connect (sock,
 543                                            (struct sockaddr *) &s_un,
 544                                            sizeof (s_un))) ||
 545            (EINPROGRESS == errno) ) )
 546     {
 547       LOG (GNUNET_ERROR_TYPE_DEBUG,
 548            "Successfully connected to unixpath `%s'!\n",
 549            unixpath);
 550       GNUNET_free (unixpath);
 551       return sock;
 552     }
 553     if (NULL != sock)
 554       GNUNET_NETWORK_socket_close (sock);
 555   }
 556   GNUNET_free_non_null (unixpath);
 557 #endif
 558   return NULL;
 559 }
 560
 561
 562 /**
 563  * Scheduler let us know that we're either ready to write on the
 564  * socket OR connect timed out.  Do the right thing.
 565  *
 566  * @param cls the `struct AddressProbe *` with the address that we are probing
 567  */
 568 static void
 569 connect_probe_continuation (void *cls)
 570 {
 571   struct AddressProbe *ap = cls;
 572   struct ClientState *cstate = ap->cstate;
 573   const struct GNUNET_SCHEDULER_TaskContext *tc;
 574   int error;
 575   socklen_t len;
 576
 577   ap->task = NULL;
 578   GNUNET_assert (NULL != ap->sock);
 579   GNUNET_CONTAINER_DLL_remove (cstate->ap_head,
 580                                cstate->ap_tail,
 581                                ap);
 582   len = sizeof (error);
 583   error = 0;
 584   tc = GNUNET_SCHEDULER_get_task_context ();
 585   if ( (0 == (tc->reason & GNUNET_SCHEDULER_REASON_WRITE_READY)) ||
 586        (GNUNET_OK !=
 587         GNUNET_NETWORK_socket_getsockopt (ap->sock,
 588                                           SOL_SOCKET,
 589                                           SO_ERROR,
 590                                           &error,
 591                                           &len)) ||
 592        (0 != error) )
 593   {
 594     GNUNET_break (GNUNET_OK ==
 595                   GNUNET_NETWORK_socket_close (ap->sock));
 596     GNUNET_free (ap);
 597     if ( (NULL == cstate->ap_head) &&
 598          //      (NULL == cstate->proxy_handshake) &&
 599          (NULL == cstate->dns_active) )
 600       connect_fail_continuation (cstate);
 601     return;
 602   }
 603   LOG (GNUNET_ERROR_TYPE_DEBUG,
 604        "Connection to `%s' succeeded!\n",
 605        cstate->service_name);
 606   /* trigger jobs that waited for the connection */
 607   GNUNET_assert (NULL == cstate->sock);
 608   cstate->sock = ap->sock;
 609   GNUNET_free (ap);
 610   cancel_aps (cstate);
 611   connect_success_continuation (cstate);
 612 }
 613
 614
 615 /**
 616  * Try to establish a connection given the specified address.
 617  * This function is called by the resolver once we have a DNS reply.
 618  *
 619  * @param cls our `struct ClientState *`
 620  * @param addr address to try, NULL for "last call"
 621  * @param addrlen length of @a addr
 622  */
 623 static void
 624 try_connect_using_address (void *cls,
 625                            const struct sockaddr *addr,
 626                            socklen_t addrlen)
 627 {
 628   struct ClientState *cstate = cls;
 629   struct AddressProbe *ap;
 630
 631   if (NULL == addr)
 632   {
 633     cstate->dns_active = NULL;
 634     if ( (NULL == cstate->ap_head) &&
 635          //  (NULL == cstate->proxy_handshake) &&
 636          (NULL == cstate->sock) )
 637       connect_fail_continuation (cstate);
 638     return;
 639   }
 640   if (NULL != cstate->sock)
 641     return;                     /* already connected */
 642   /* try to connect */
 643   LOG (GNUNET_ERROR_TYPE_DEBUG,
 644        "Trying to connect using address `%s:%u'\n",
 645        GNUNET_a2s (addr,
 646                    addrlen),
 647        cstate->port);
 648   ap = GNUNET_malloc (sizeof (struct AddressProbe) + addrlen);
 649   ap->addr = (const struct sockaddr *) &ap[1];
 650   GNUNET_memcpy (&ap[1],
 651                  addr,
 652                  addrlen);
 653   ap->addrlen = addrlen;
 654   ap->cstate = cstate;
 655
 656   switch (ap->addr->sa_family)
 657   {
 658   case AF_INET:
 659     ((struct sockaddr_in *) ap->addr)->sin_port = htons (cstate->port);
 660     break;
 661   case AF_INET6:
 662     ((struct sockaddr_in6 *) ap->addr)->sin6_port = htons (cstate->port);
 663     break;
 664   default:
 665     GNUNET_break (0);
 666     GNUNET_free (ap);
 667     return;                     /* not supported by us */
 668   }
 669   ap->sock = GNUNET_NETWORK_socket_create (ap->addr->sa_family,
 670                                            SOCK_STREAM,
 671                                            0);
 672   if (NULL == ap->sock)
 673   {
 674     GNUNET_free (ap);
 675     return;                     /* not supported by OS */
 676   }
 677   if ( (GNUNET_OK !=
 678         GNUNET_NETWORK_socket_connect (ap->sock,
 679                                        ap->addr,
 680                                        ap->addrlen)) &&
 681        (EINPROGRESS != errno) )
 682   {
 683     /* maybe refused / unsupported address, try next */
 684     GNUNET_log_strerror (GNUNET_ERROR_TYPE_INFO,
 685                          "connect");
 686     GNUNET_break (GNUNET_OK ==
 687                   GNUNET_NETWORK_socket_close (ap->sock));
 688     GNUNET_free (ap);
 689     return;
 690   }
 691   GNUNET_CONTAINER_DLL_insert (cstate->ap_head,
 692                                cstate->ap_tail,
 693                                ap);
 694   ap->task = GNUNET_SCHEDULER_add_write_net (CONNECT_RETRY_TIMEOUT,
 695                                              ap->sock,
 696                                              &connect_probe_continuation,
 697                                              ap);
 698 }
 699
 700
 701 /**
 702  * Test whether the configuration has proper values for connection
 703  * (UNIXPATH || (PORT && HOSTNAME)).
 704  *
 705  * @param service_name name of service to connect to
 706  * @param cfg configuration to use
 707  * @return #GNUNET_OK if the configuration is valid, #GNUNET_SYSERR if not
 708  */
 709 static int
 710 test_service_configuration (const char *service_name,
 711                             const struct GNUNET_CONFIGURATION_Handle *cfg)
 712 {
 713   int ret = GNUNET_SYSERR;
 714   char *hostname = NULL;
 715   unsigned long long port;
 716 #if AF_UNIX
 717   char *unixpath = NULL;
 718
 719   if ((GNUNET_OK ==
 720        GNUNET_CONFIGURATION_get_value_filename (cfg,
 721                                                 service_name,
 722                                                 "UNIXPATH",
 723                                                 &unixpath)) &&
 724       (0 < strlen (unixpath)))
 725     ret = GNUNET_OK;
 726   GNUNET_free_non_null (unixpath);
 727 #endif
 728
 729   if ( (GNUNET_YES ==
 730         GNUNET_CONFIGURATION_have_value (cfg,
 731                                          service_name,
 732                                          "PORT")) &&
 733        (GNUNET_OK ==
 734         GNUNET_CONFIGURATION_get_value_number (cfg,
 735                                                service_name,
 736                                                "PORT",
 737                                                &port)) &&
 738        (port <= 65535) &&
 739        (0 != port) &&
 740        (GNUNET_OK ==
 741         GNUNET_CONFIGURATION_get_value_string (cfg,
 742                                                service_name,
 743                                                "HOSTNAME",
 744                                                &hostname)) &&
 745        (0 != strlen (hostname)) )
 746     ret = GNUNET_OK;
 747   GNUNET_free_non_null (hostname);
 748   return ret;
 749 }
 750
 751
 752 /**
 753  * Try to connect to the service.
 754  *
 755  * @param cls the `struct ClientState` to try to connect to the service
 756  */
 757 static void
 758 start_connect (void *cls)
 759 {
 760   struct ClientState *cstate = cls;
 761
 762   cstate->retry_task = NULL;
 763 #if 0
 764   /* Never use a local source if a proxy is configured */
 765   if (GNUNET_YES ==
 766       GNUNET_SOCKS_check_service (cstate->service_name,
 767                                   cstate->cfg))
 768   {
 769     socks_connect (cstate);
 770     return;
 771   }
 772 #endif
 773
 774   if ( (0 == (cstate->attempts++ % 2)) ||
 775        (0 == cstate->port) ||
 776        (NULL == cstate->hostname) )
 777   {
 778     /* on even rounds, try UNIX first, or always
 779        if we do not have a DNS name and TCP port. */
 780     cstate->sock = try_unixpath (cstate->service_name,
 781                                  cstate->cfg);
 782     if (NULL != cstate->sock)
 783     {
 784       connect_success_continuation (cstate);
 785       return;
 786     }
 787   }
 788   if ( (NULL == cstate->hostname) ||
 789        (0 == cstate->port) )
 790   {
 791     /* All options failed. Boo! */
 792     connect_fail_continuation (cstate);
 793     return;
 794   }
 795   cstate->dns_active
 796     = GNUNET_RESOLVER_ip_get (cstate->hostname,
 797                               AF_UNSPEC,
 798                               CONNECT_RETRY_TIMEOUT,
 799                               &try_connect_using_address,
 800                               cstate);
 801 }
 802
 803
 804 /**
 805  * Implements the transmission functionality of a message queue.
 806  *
 807  * @param mq the message queue
 808  * @param msg the message to send
 809  * @param impl_state our `struct ClientState`
 810  */
 811 static void
 812 connection_client_send_impl (struct GNUNET_MQ_Handle *mq,
 813                              const struct GNUNET_MessageHeader *msg,
 814                              void *impl_state)
 815 {
 816   struct ClientState *cstate = impl_state;
 817
 818   (void) mq;
 819   /* only one message at a time allowed */
 820   GNUNET_assert (NULL == cstate->msg);
 821   GNUNET_assert (NULL == cstate->send_task);
 822   cstate->msg = msg;
 823   cstate->msg_off = 0;
 824   if (NULL == cstate->sock){
 825     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 826                 "client: message of type %u waiting for socket\n",
 827                 ntohs(msg->type));
 828     return; /* still waiting for connection */
 829    }
 830   cstate->send_task
 831     = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 832                                       cstate->sock,
 833                                       &transmit_ready,
 834                                       cstate);
 835 }
 836
 837
 838 /**
 839  * Cancel the currently sent message.
 840  *
 841  * @param mq message queue
 842  * @param impl_state our `struct ClientState`
 843  */
 844 static void
 845 connection_client_cancel_impl (struct GNUNET_MQ_Handle *mq,
 846                                void *impl_state)
 847 {
 848   struct ClientState *cstate = impl_state;
 849
 850   (void) mq;
 851   GNUNET_assert (NULL != cstate->msg);
 852   GNUNET_assert (0 == cstate->msg_off);
 853   cstate->msg = NULL;
 854   if (NULL != cstate->send_task)
 855   {
 856     GNUNET_SCHEDULER_cancel (cstate->send_task);
 857     cstate->send_task = NULL;
 858   }
 859 }
 860
 861
 862 /**
 863  * Create a message queue to connect to a GNUnet service.
 864  * If handlers are specfied, receive messages from the connection.
 865  *
 866  * @param cfg our configuration
 867  * @param service_name name of the service to connect to
 868  * @param handlers handlers for receiving messages, can be NULL
 869  * @param error_handler error handler
 870  * @param error_handler_cls closure for the @a error_handler
 871  * @return the message queue, NULL on error
 872  */
 873 struct GNUNET_MQ_Handle *
 874 GNUNET_CLIENT_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
 875                        const char *service_name,
 876                        const struct GNUNET_MQ_MessageHandler *handlers,
 877                        GNUNET_MQ_ErrorHandler error_handler,
 878                        void *error_handler_cls)
 879 {
 880   struct ClientState *cstate;
 881
 882   if (GNUNET_OK !=
 883       test_service_configuration (service_name,
 884                                   cfg))
 885     return NULL;
 886   cstate = GNUNET_new (struct ClientState);
 887   cstate->service_name = GNUNET_strdup (service_name);
 888   cstate->cfg = cfg;
 889   cstate->retry_task = GNUNET_SCHEDULER_add_now (&start_connect,
 890                                                  cstate);
 891   cstate->mst = GNUNET_MST_create (&recv_message,
 892                                    cstate);
 893   if (GNUNET_YES ==
 894       GNUNET_CONFIGURATION_have_value (cfg,
 895                                        service_name,
 896                                        "PORT"))
 897   {
 898     if (! ( (GNUNET_OK !=
 899              GNUNET_CONFIGURATION_get_value_number (cfg,
 900                                                     service_name,
 901                                                     "PORT",
 902                                                     &cstate->port)) ||
 903             (cstate->port > 65535) ||
 904             (GNUNET_OK !=
 905              GNUNET_CONFIGURATION_get_value_string (cfg,
 906                                                     service_name,
 907                                                     "HOSTNAME",
 908                                                     &cstate->hostname)) ) &&
 909         (0 == strlen (cstate->hostname)) )
 910     {
 911       GNUNET_free (cstate->hostname);
 912       cstate->hostname = NULL;
 913       LOG (GNUNET_ERROR_TYPE_WARNING,
 914            _("Need a non-empty hostname for service `%s'.\n"),
 915            service_name);
 916     }
 917   }
 918   cstate->mq = GNUNET_MQ_queue_for_callbacks (&connection_client_send_impl,
 919                                               &connection_client_destroy_impl,
 920                                               &connection_client_cancel_impl,
 921                                               cstate,
 922                                               handlers,
 923                                               error_handler,
 924                                               error_handler_cls);
 925   return cstate->mq;
 926 }
 927
 928 /* end of client.c */