text: /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   * Copyright (c) 2007-2021, The Tor Project, Inc. */
  /* See LICENSE for licensing information */
  
  /**
   * \file rendcommon.c
   * \brief Rendezvous implementation: shared code between
   * introducers, services, clients, and rendezvous points.
   **/
  
  #define RENDCOMMON_PRIVATE
  
  #include "core/or/or.h"
  
  #include "app/config/config.h"
  
  #include "core/or/circuitlist.h"
  #include "core/or/circuituse.h"
  
  #include "feature/hs/hs_client.h"
  #include "feature/hs/hs_common.h"
  #include "feature/hs/hs_intropoint.h"
  #include "feature/rend/rendcommon.h"
  #include "feature/rend/rendmid.h"
  
  #include "core/or/circuit_st.h"
  #include "core/or/cpath_build_state_st.h"
  #include "core/or/crypt_path_st.h"
  #include "core/or/origin_circuit_st.h"
  
  /** Called when we get a rendezvous-related relay cell on circuit
   * <b>circ</b>.  Dispatch on rendezvous relay command. */
  void
  rend_process_relay_cell(circuit_t *circ, const crypt_path_t *layer_hint,
                          int command, size_t length,
                          const uint8_t *payload)
  {
    or_circuit_t *or_circ = NULL;
    origin_circuit_t *origin_circ = NULL;
    int r = -2;
    if (CIRCUIT_IS_ORIGIN(circ)) {
      origin_circ = TO_ORIGIN_CIRCUIT(circ);
      if (!layer_hint || layer_hint != origin_circ->cpath->prev) {
        log_fn(LOG_PROTOCOL_WARN, LD_APP,
               "Relay cell (rend purpose %d) from wrong hop on origin circ",
               command);
        origin_circ = NULL;
      }
    } else {
      or_circ = TO_OR_CIRCUIT(circ);
    }
  
    switch (command) {
      case RELAY_COMMAND_ESTABLISH_INTRO:
        if (or_circ)
          r = hs_intro_received_establish_intro(or_circ, payload, length);
        break;
      case RELAY_COMMAND_ESTABLISH_RENDEZVOUS:
        if (or_circ)
          r = rend_mid_establish_rendezvous(or_circ, payload, length);
        break;
      case RELAY_COMMAND_INTRODUCE1:
        if (or_circ)
          r = hs_intro_received_introduce1(or_circ, payload, length);
        break;
      case RELAY_COMMAND_INTRODUCE2:
        if (origin_circ)
          r = hs_service_receive_introduce2(origin_circ, payload, length);
        break;
      case RELAY_COMMAND_INTRODUCE_ACK:
        if (origin_circ)
          r = hs_client_receive_introduce_ack(origin_circ, payload, length);
        break;
      case RELAY_COMMAND_RENDEZVOUS1:
        if (or_circ)
          r = rend_mid_rendezvous(or_circ, payload, length);
        break;
      case RELAY_COMMAND_RENDEZVOUS2:
        if (origin_circ)
          r = hs_client_receive_rendezvous2(origin_circ, payload, length);
        break;
      case RELAY_COMMAND_INTRO_ESTABLISHED:
        if (origin_circ)
          r = hs_service_receive_intro_established(origin_circ, payload, length);
        break;
      case RELAY_COMMAND_RENDEZVOUS_ESTABLISHED:
        if (origin_circ)
          r = hs_client_receive_rendezvous_acked(origin_circ, payload, length);
        break;
      default:
        tor_fragile_assert();
    }
  
    if (r == 0 && origin_circ) {
      /* This was a valid cell. Count it as delivered + overhead. */
      circuit_read_valid_data(origin_circ, length);
    }
  
    if (r == -2)
      log_info(LD_PROTOCOL, "Dropping cell (type %d) for wrong circuit type.",
               command);
  }
  
  /* Make sure that tor only builds one-hop circuits when they would not
   * compromise user anonymity.
   *
   * One-hop circuits are permitted in Single Onion modes.
   *
   * Single Onion modes are also allowed to make multi-hop circuits.
   * For example, single onion HSDir circuits are 3-hop to prevent denial of
   * service.
   */
  void
  assert_circ_anonymity_ok(const origin_circuit_t *circ,
                           const or_options_t *options)
  {
    tor_assert(options);
    tor_assert(circ);
    tor_assert(circ->build_state);
  
    if (circ->build_state->onehop_tunnel) {
      tor_assert(hs_service_allow_non_anonymous_connection(options));
    }
  }
  