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   if (GNUNET_SYSERR == cstate->in_destroy)
 381   {
 382     /* defer destruction */
 383     cstate->in_destroy = GNUNET_YES;
 384     cstate->mq = NULL;
 385     return;
 386   }
 387   if (NULL != cstate->dns_active)
 388     GNUNET_RESOLVER_request_cancel (cstate->dns_active);
 389   if (NULL != cstate->send_task)
 390     GNUNET_SCHEDULER_cancel (cstate->send_task);
 391   if (NULL != cstate->recv_task)
 392     GNUNET_SCHEDULER_cancel (cstate->recv_task);
 393   if (NULL != cstate->retry_task)
 394     GNUNET_SCHEDULER_cancel (cstate->retry_task);
 395   if (NULL != cstate->sock){
 396     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 397                 "client: destroying socket: %p\n",
 398                 cstate->sock);
 399     GNUNET_NETWORK_socket_close (cstate->sock);
 400   }
 401   cancel_aps (cstate);
 402   GNUNET_free (cstate->service_name);
 403   GNUNET_free_non_null (cstate->hostname);
 404   GNUNET_MST_destroy (cstate->mst);
 405   GNUNET_free (cstate);
 406 }
 407
 408
 409 /**
 410  * This function is called once we have data ready to read.
 411  *
 412  * @param cls `struct ClientState` with connection to read from
 413  */
 414 static void
 415 receive_ready (void *cls)
 416 {
 417   struct ClientState *cstate = cls;
 418   int ret;
 419
 420   cstate->recv_task = NULL;
 421   cstate->in_destroy = GNUNET_SYSERR;
 422   ret = GNUNET_MST_read (cstate->mst,
 423                          cstate->sock,
 424                          GNUNET_NO,
 425                          GNUNET_NO);
 426   if (GNUNET_SYSERR == ret)
 427   {
 428     if (NULL != cstate->mq)
 429       GNUNET_MQ_inject_error (cstate->mq,
 430                               GNUNET_MQ_ERROR_READ);
 431     if (GNUNET_YES == cstate->in_destroy)
 432       connection_client_destroy_impl (cstate->mq,
 433                                       cstate);
 434     return;
 435   }
 436   if (GNUNET_YES == cstate->in_destroy)
 437   {
 438     connection_client_destroy_impl (cstate->mq,
 439                                     cstate);
 440     return;
 441   }
 442   cstate->in_destroy = GNUNET_NO;
 443   cstate->recv_task
 444     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 445                                      cstate->sock,
 446                                      &receive_ready,
 447                                      cstate);
 448 }
 449
 450
 451 /**
 452  * We've succeeded in establishing a connection.
 453  *
 454  * @param cstate the connection we tried to establish
 455  */
 456 static void
 457 connect_success_continuation (struct ClientState *cstate)
 458 {
 459   GNUNET_assert (NULL == cstate->recv_task);
 460   cstate->recv_task
 461     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 462                                      cstate->sock,
 463                                      &receive_ready,
 464                                      cstate);
 465   if (NULL != cstate->msg)
 466   {
 467     GNUNET_assert (NULL == cstate->send_task);
 468     cstate->send_task
 469       = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 470                                         cstate->sock,
 471                                         &transmit_ready,
 472                                         cstate);
 473   }
 474 }
 475
 476
 477 /**
 478  * Try connecting to the server using UNIX domain sockets.
 479  *
 480  * @param service_name name of service to connect to
 481  * @param cfg configuration to use
 482  * @return NULL on error, socket connected to UNIX otherwise
 483  */
 484 static struct GNUNET_NETWORK_Handle *
 485 try_unixpath (const char *service_name,
 486               const struct GNUNET_CONFIGURATION_Handle *cfg)
 487 {
 488 #if AF_UNIX
 489   struct GNUNET_NETWORK_Handle *sock;
 490   char *unixpath;
 491   struct sockaddr_un s_un;
 492
 493   unixpath = NULL;
 494   if ((GNUNET_OK ==
 495        GNUNET_CONFIGURATION_get_value_filename (cfg,
 496                                                 service_name,
 497                                                 "UNIXPATH",
 498                                                 &unixpath)) &&
 499       (0 < strlen (unixpath)))
 500   {
 501     /* We have a non-NULL unixpath, need to validate it */
 502     if (strlen (unixpath) >= sizeof (s_un.sun_path))
 503     {
 504       LOG (GNUNET_ERROR_TYPE_WARNING,
 505            _("UNIXPATH `%s' too long, maximum length is %llu\n"),
 506            unixpath,
 507            (unsigned long long) sizeof (s_un.sun_path));
 508       unixpath = GNUNET_NETWORK_shorten_unixpath (unixpath);
 509       LOG (GNUNET_ERROR_TYPE_INFO,
 510            _("Using `%s' instead\n"),
 511            unixpath);
 512       if (NULL == unixpath)
 513         return NULL;
 514     }
 515     memset (&s_un,
 516             0,
 517             sizeof (s_un));
 518     s_un.sun_family = AF_UNIX;
 519     strncpy (s_un.sun_path,
 520              unixpath,
 521              sizeof (s_un.sun_path) - 1);
 522 #ifdef LINUX
 523     {
 524       int abstract;
 525
 526       abstract = GNUNET_CONFIGURATION_get_value_yesno (cfg,
 527                                                        "TESTING",
 528                                                        "USE_ABSTRACT_SOCKETS");
 529       if (GNUNET_YES == abstract)
 530         s_un.sun_path[0] = '\0';
 531     }
 532 #endif
 533 #if HAVE_SOCKADDR_UN_SUN_LEN
 534     s_un.sun_len = (u_char) sizeof (struct sockaddr_un);
 535 #endif
 536     sock = GNUNET_NETWORK_socket_create (AF_UNIX,
 537                                          SOCK_STREAM,
 538                                          0);
 539     if ( (NULL != sock) &&
 540          ( (GNUNET_OK ==
 541             GNUNET_NETWORK_socket_connect (sock,
 542                                            (struct sockaddr *) &s_un,
 543                                            sizeof (s_un))) ||
 544            (EINPROGRESS == errno) ) )
 545     {
 546       LOG (GNUNET_ERROR_TYPE_DEBUG,
 547            "Successfully connected to unixpath `%s'!\n",
 548            unixpath);
 549       GNUNET_free (unixpath);
 550       return sock;
 551     }
 552     if (NULL != sock)
 553       GNUNET_NETWORK_socket_close (sock);
 554   }
 555   GNUNET_free_non_null (unixpath);
 556 #endif
 557   return NULL;
 558 }
 559
 560
 561 /**
 562  * Scheduler let us know that we're either ready to write on the
 563  * socket OR connect timed out.  Do the right thing.
 564  *
 565  * @param cls the `struct AddressProbe *` with the address that we are probing
 566  */
 567 static void
 568 connect_probe_continuation (void *cls)
 569 {
 570   struct AddressProbe *ap = cls;
 571   struct ClientState *cstate = ap->cstate;
 572   const struct GNUNET_SCHEDULER_TaskContext *tc;
 573   int error;
 574   socklen_t len;
 575
 576   ap->task = NULL;
 577   GNUNET_assert (NULL != ap->sock);
 578   GNUNET_CONTAINER_DLL_remove (cstate->ap_head,
 579                                cstate->ap_tail,
 580                                ap);
 581   len = sizeof (error);
 582   error = 0;
 583   tc = GNUNET_SCHEDULER_get_task_context ();
 584   if ( (0 == (tc->reason & GNUNET_SCHEDULER_REASON_WRITE_READY)) ||
 585        (GNUNET_OK !=
 586         GNUNET_NETWORK_socket_getsockopt (ap->sock,
 587                                           SOL_SOCKET,
 588                                           SO_ERROR,
 589                                           &error,
 590                                           &len)) ||
 591        (0 != error) )
 592   {
 593     GNUNET_break (GNUNET_OK ==
 594                   GNUNET_NETWORK_socket_close (ap->sock));
 595     GNUNET_free (ap);
 596     if ( (NULL == cstate->ap_head) &&
 597          //      (NULL == cstate->proxy_handshake) &&
 598          (NULL == cstate->dns_active) )
 599       connect_fail_continuation (cstate);
 600     return;
 601   }
 602   LOG (GNUNET_ERROR_TYPE_DEBUG,
 603        "Connection to `%s' succeeded!\n",
 604        cstate->service_name);
 605   /* trigger jobs that waited for the connection */
 606   GNUNET_assert (NULL == cstate->sock);
 607   cstate->sock = ap->sock;
 608   GNUNET_free (ap);
 609   cancel_aps (cstate);
 610   connect_success_continuation (cstate);
 611 }
 612
 613
 614 /**
 615  * Try to establish a connection given the specified address.
 616  * This function is called by the resolver once we have a DNS reply.
 617  *
 618  * @param cls our `struct ClientState *`
 619  * @param addr address to try, NULL for "last call"
 620  * @param addrlen length of @a addr
 621  */
 622 static void
 623 try_connect_using_address (void *cls,
 624                            const struct sockaddr *addr,
 625                            socklen_t addrlen)
 626 {
 627   struct ClientState *cstate = cls;
 628   struct AddressProbe *ap;
 629
 630   if (NULL == addr)
 631   {
 632     cstate->dns_active = NULL;
 633     if ( (NULL == cstate->ap_head) &&
 634          //  (NULL == cstate->proxy_handshake) &&
 635          (NULL == cstate->sock) )
 636       connect_fail_continuation (cstate);
 637     return;
 638   }
 639   if (NULL != cstate->sock)
 640     return;                     /* already connected */
 641   /* try to connect */
 642   LOG (GNUNET_ERROR_TYPE_DEBUG,
 643        "Trying to connect using address `%s:%u'\n",
 644        GNUNET_a2s (addr,
 645                    addrlen),
 646        cstate->port);
 647   ap = GNUNET_malloc (sizeof (struct AddressProbe) + addrlen);
 648   ap->addr = (const struct sockaddr *) &ap[1];
 649   GNUNET_memcpy (&ap[1],
 650                  addr,
 651                  addrlen);
 652   ap->addrlen = addrlen;
 653   ap->cstate = cstate;
 654
 655   switch (ap->addr->sa_family)
 656   {
 657   case AF_INET:
 658     ((struct sockaddr_in *) ap->addr)->sin_port = htons (cstate->port);
 659     break;
 660   case AF_INET6:
 661     ((struct sockaddr_in6 *) ap->addr)->sin6_port = htons (cstate->port);
 662     break;
 663   default:
 664     GNUNET_break (0);
 665     GNUNET_free (ap);
 666     return;                     /* not supported by us */
 667   }
 668   ap->sock = GNUNET_NETWORK_socket_create (ap->addr->sa_family,
 669                                            SOCK_STREAM,
 670                                            0);
 671   if (NULL == ap->sock)
 672   {
 673     GNUNET_free (ap);
 674     return;                     /* not supported by OS */
 675   }
 676   if ( (GNUNET_OK !=
 677         GNUNET_NETWORK_socket_connect (ap->sock,
 678                                        ap->addr,
 679                                        ap->addrlen)) &&
 680        (EINPROGRESS != errno) )
 681   {
 682     /* maybe refused / unsupported address, try next */
 683     GNUNET_log_strerror (GNUNET_ERROR_TYPE_INFO,
 684                          "connect");
 685     GNUNET_break (GNUNET_OK ==
 686                   GNUNET_NETWORK_socket_close (ap->sock));
 687     GNUNET_free (ap);
 688     return;
 689   }
 690   GNUNET_CONTAINER_DLL_insert (cstate->ap_head,
 691                                cstate->ap_tail,
 692                                ap);
 693   ap->task = GNUNET_SCHEDULER_add_write_net (CONNECT_RETRY_TIMEOUT,
 694                                              ap->sock,
 695                                              &connect_probe_continuation,
 696                                              ap);
 697 }
 698
 699
 700 /**
 701  * Test whether the configuration has proper values for connection
 702  * (UNIXPATH || (PORT && HOSTNAME)).
 703  *
 704  * @param service_name name of service to connect to
 705  * @param cfg configuration to use
 706  * @return #GNUNET_OK if the configuration is valid, #GNUNET_SYSERR if not
 707  */
 708 static int
 709 test_service_configuration (const char *service_name,
 710                             const struct GNUNET_CONFIGURATION_Handle *cfg)
 711 {
 712   int ret = GNUNET_SYSERR;
 713   char *hostname = NULL;
 714   unsigned long long port;
 715 #if AF_UNIX
 716   char *unixpath = NULL;
 717
 718   if ((GNUNET_OK ==
 719        GNUNET_CONFIGURATION_get_value_filename (cfg,
 720                                                 service_name,
 721                                                 "UNIXPATH",
 722                                                 &unixpath)) &&
 723       (0 < strlen (unixpath)))
 724     ret = GNUNET_OK;
 725   GNUNET_free_non_null (unixpath);
 726 #endif
 727
 728   if ( (GNUNET_YES ==
 729         GNUNET_CONFIGURATION_have_value (cfg,
 730                                          service_name,
 731                                          "PORT")) &&
 732        (GNUNET_OK ==
 733         GNUNET_CONFIGURATION_get_value_number (cfg,
 734                                                service_name,
 735                                                "PORT",
 736                                                &port)) &&
 737        (port <= 65535) &&
 738        (0 != port) &&
 739        (GNUNET_OK ==
 740         GNUNET_CONFIGURATION_get_value_string (cfg,
 741                                                service_name,
 742                                                "HOSTNAME",
 743                                                &hostname)) &&
 744        (0 != strlen (hostname)) )
 745     ret = GNUNET_OK;
 746   GNUNET_free_non_null (hostname);
 747   return ret;
 748 }
 749
 750
 751 /**
 752  * Try to connect to the service.
 753  *
 754  * @param cls the `struct ClientState` to try to connect to the service
 755  */
 756 static void
 757 start_connect (void *cls)
 758 {
 759   struct ClientState *cstate = cls;
 760
 761   cstate->retry_task = NULL;
 762 #if 0
 763   /* Never use a local source if a proxy is configured */
 764   if (GNUNET_YES ==
 765       GNUNET_SOCKS_check_service (cstate->service_name,
 766                                   cstate->cfg))
 767   {
 768     socks_connect (cstate);
 769     return;
 770   }
 771 #endif
 772
 773   if ( (0 == (cstate->attempts++ % 2)) ||
 774        (0 == cstate->port) ||
 775        (NULL == cstate->hostname) )
 776   {
 777     /* on even rounds, try UNIX first, or always
 778        if we do not have a DNS name and TCP port. */
 779     cstate->sock = try_unixpath (cstate->service_name,
 780                                  cstate->cfg);
 781     if (NULL != cstate->sock)
 782     {
 783       connect_success_continuation (cstate);
 784       return;
 785     }
 786   }
 787   if ( (NULL == cstate->hostname) ||
 788        (0 == cstate->port) )
 789   {
 790     /* All options failed. Boo! */
 791     connect_fail_continuation (cstate);
 792     return;
 793   }
 794   cstate->dns_active
 795     = GNUNET_RESOLVER_ip_get (cstate->hostname,
 796                               AF_UNSPEC,
 797                               CONNECT_RETRY_TIMEOUT,
 798                               &try_connect_using_address,
 799                               cstate);
 800 }
 801
 802
 803 /**
 804  * Implements the transmission functionality of a message queue.
 805  *
 806  * @param mq the message queue
 807  * @param msg the message to send
 808  * @param impl_state our `struct ClientState`
 809  */
 810 static void
 811 connection_client_send_impl (struct GNUNET_MQ_Handle *mq,
 812                              const struct GNUNET_MessageHeader *msg,
 813                              void *impl_state)
 814 {
 815   struct ClientState *cstate = impl_state;
 816
 817   /* only one message at a time allowed */
 818   GNUNET_assert (NULL == cstate->msg);
 819   GNUNET_assert (NULL == cstate->send_task);
 820   cstate->msg = msg;
 821   cstate->msg_off = 0;
 822   if (NULL == cstate->sock){
 823     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 824                 "client: message of type %u waiting for socket\n",
 825                 ntohs(msg->type));
 826     return; /* still waiting for connection */
 827    }
 828   cstate->send_task
 829     = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 830                                       cstate->sock,
 831                                       &transmit_ready,
 832                                       cstate);
 833 }
 834
 835
 836 /**
 837  * Cancel the currently sent message.
 838  *
 839  * @param mq message queue
 840  * @param impl_state our `struct ClientState`
 841  */
 842 static void
 843 connection_client_cancel_impl (struct GNUNET_MQ_Handle *mq,
 844                                void *impl_state)
 845 {
 846   struct ClientState *cstate = impl_state;
 847
 848   GNUNET_assert (NULL != cstate->msg);
 849   GNUNET_assert (0 == cstate->msg_off);
 850   cstate->msg = NULL;
 851   if (NULL != cstate->send_task)
 852   {
 853     GNUNET_SCHEDULER_cancel (cstate->send_task);
 854     cstate->send_task = NULL;
 855   }
 856 }
 857
 858
 859 /**
 860  * Create a message queue to connect to a GNUnet service.
 861  * If handlers are specfied, receive messages from the connection.
 862  *
 863  * @param cfg our configuration
 864  * @param service_name name of the service to connect to
 865  * @param handlers handlers for receiving messages, can be NULL
 866  * @param error_handler error handler
 867  * @param error_handler_cls closure for the @a error_handler
 868  * @return the message queue, NULL on error
 869  */
 870 struct GNUNET_MQ_Handle *
 871 GNUNET_CLIENT_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
 872                        const char *service_name,
 873                        const struct GNUNET_MQ_MessageHandler *handlers,
 874                        GNUNET_MQ_ErrorHandler error_handler,
 875                        void *error_handler_cls)
 876 {
 877   struct ClientState *cstate;
 878
 879   if (GNUNET_OK !=
 880       test_service_configuration (service_name,
 881                                   cfg))
 882     return NULL;
 883   cstate = GNUNET_new (struct ClientState);
 884   cstate->service_name = GNUNET_strdup (service_name);
 885   cstate->cfg = cfg;
 886   cstate->retry_task = GNUNET_SCHEDULER_add_now (&start_connect,
 887                                                  cstate);
 888   cstate->mst = GNUNET_MST_create (&recv_message,
 889                                    cstate);
 890   if (GNUNET_YES ==
 891       GNUNET_CONFIGURATION_have_value (cfg,
 892                                        service_name,
 893                                        "PORT"))
 894   {
 895     if (! ( (GNUNET_OK !=
 896              GNUNET_CONFIGURATION_get_value_number (cfg,
 897                                                     service_name,
 898                                                     "PORT",
 899                                                     &cstate->port)) ||
 900             (cstate->port > 65535) ||
 901             (GNUNET_OK !=
 902              GNUNET_CONFIGURATION_get_value_string (cfg,
 903                                                     service_name,
 904                                                     "HOSTNAME",
 905                                                     &cstate->hostname)) ) &&
 906         (0 == strlen (cstate->hostname)) )
 907     {
 908       GNUNET_free (cstate->hostname);
 909       cstate->hostname = NULL;
 910       LOG (GNUNET_ERROR_TYPE_WARNING,
 911            _("Need a non-empty hostname for service `%s'.\n"),
 912            service_name);
 913     }
 914   }
 915   cstate->mq = GNUNET_MQ_queue_for_callbacks (&connection_client_send_impl,
 916                                               &connection_client_destroy_impl,
 917                                               &connection_client_cancel_impl,
 918                                               cstate,
 919                                               handlers,
 920                                               error_handler,
 921                                               error_handler_cls);
 922   return cstate->mq;
 923 }
 924
 925 /* end of client.c */