Method will_this_request_self_loop

src/proxy/http/HttpTransact.cc:6579–6657

}

bool
HttpTransact::will_this_request_self_loop(State *s)
{
  // The self-loop detection for this ATS node will allow up to max_proxy_cycles
  // (each time it sees it returns to itself it is one cycle) before declaring a self-looping condition detected.
  // If max_proxy_cycles is > 0 then next-hop is disabled since --
  //   * if first cycle then it is alright okay
  //   * if not first cycle then will be detected by via string checking the next time that
  //     it enters the node
  int max_proxy_cycles = s->txn_conf->max_proxy_cycles;

  ////////////////////////////////////////
  // check if we are about to self loop //
  ////////////////////////////////////////
  if (s->dns_info.active) {
    TxnDbg(dbg_ctl_http_transact, "max_proxy_cycles = %d", max_proxy_cycles);
    if (max_proxy_cycles == 0) {
      in_port_t dst_port   = s->hdr_info.client_request.url_get()->port_get(); // going to this port.
      in_port_t local_port = s->client_info.dst_addr.host_order_port();        // already connected proxy port.
      // It's a loop if connecting to the same port as it already connected to the proxy and
      // it's a proxy address or the same address it already connected to.
      TxnDbg(dbg_ctl_http_transact, "dst_port = %d local_port = %d", dst_port, local_port);
      if (dst_port == local_port && ((s->dns_info.active->data.ip == &Machine::instance()->ip.sa) ||
                                     (s->dns_info.active->data.ip == s->client_info.dst_addr))) {
        switch (s->dns_info.looking_up) {
        case ResolveInfo::ORIGIN_SERVER:
          TxnDbg(dbg_ctl_http_transact, "host ip and port same as local ip and port - bailing");
          break;
        case ResolveInfo::PARENT_PROXY:
          TxnDbg(dbg_ctl_http_transact, "parent proxy ip and port same as local ip and port - bailing");
          break;
        default:
          TxnDbg(dbg_ctl_http_transact, "unknown's ip and port same as local ip and port - bailing");
          break;
        }
        SET_VIA_STRING(VIA_ERROR_TYPE, VIA_ERROR_LOOP_DETECTED);
        Metrics::Counter::increment(http_rsb.proxy_loop_detected);
        build_error_response(s, HTTP_STATUS_BAD_REQUEST, "Cycle Detected", "request#cycle_detected");
        return true;
      }
    }

    // Now check for a loop using the Via string.
    int              count     = 0;
    MIMEField       *via_field = s->hdr_info.client_request.field_find(MIME_FIELD_VIA, MIME_LEN_VIA);
    std::string_view uuid{Machine::instance()->uuid.getString()};

    while (via_field) {
      // No need to waste cycles comma separating the via values since we want to do a match anywhere in the
      // in the string.  We can just loop over the dup hdr fields
      auto via_string{via_field->value_get()};

      if ((count <= max_proxy_cycles) && via_string.data()) {
        std::string_view            current{via_field->value_get()};
        std::string_view::size_type offset;
        TxnDbg(dbg_ctl_http_transact, "Incoming via: \"%.*s\" --has-- (%s[%s] (%s))", static_cast<int>(via_string.length()),
               via_string.data(), s->http_config_param->proxy_hostname, uuid.data(),
               s->http_config_param->proxy_request_via_string);