Method OSDNSLookup

src/proxy/http/HttpTransact.cc:1899–2081

////////////////////////////////////////////////////////////////////////// Name : OSDNSLookup Description: called after the DNS lookup of origin server name Details : normally called after Start. may be called more than once, however, if the dns lookup fails. this may be because it was not possible to resolve the name after several attempts. the next action depends. since this function

//
///////////////////////////////////////////////////////////////////////////////
void
HttpTransact::OSDNSLookup(State *s)
{
  ink_assert(s->dns_info.looking_up == ResolveInfo::UpstreamResolveStyle::ORIGIN_SERVER);

  TxnDbg(dbg_ctl_http_trans, "Entering HttpTransact::OSDNSLookup");

  if (!s->dns_info.resolved_p) {
    if (ResolveInfo::OS_Addr::TRY_HOSTDB == s->dns_info.os_addr_style) {
      /* Transparent case: We tried to connect to client target address, failed and tried to use a different addr
       * but that failed to resolve therefore keep on with the CTA.
       */
      s->dns_info.addr.assign(s->state_machine->get_ua_txn()->get_netvc()->get_local_addr()); // fetch CTA
      s->dns_info.resolved_p    = true;
      s->dns_info.os_addr_style = ResolveInfo::OS_Addr::USE_CLIENT;
      TxnDbg(dbg_ctl_http_seq, "DNS lookup unsuccessful, using client target address");
    } else {
      TxnDbg(dbg_ctl_http_seq, "DNS Lookup unsuccessful");
      char const *log_msg;

      // Even with unsuccessful DNS lookup, return stale object from cache if applicable
      if (is_cache_hit(s->cache_lookup_result) && is_stale_cache_response_returnable(s)) {
        s->source = SOURCE_CACHE;
        TxnDbg(dbg_ctl_http_trans, "[hscno] serving stale doc to client");
        build_response_from_cache(s, HTTP_WARNING_CODE_REVALIDATION_FAILED);
        return;
      }
      // output the DNS failure error message
      SET_VIA_STRING(VIA_DETAIL_TUNNEL, VIA_DETAIL_TUNNEL_NO_FORWARD);
      if (!s->dns_info.record || s->dns_info.record->is_failed()) {
        // Set to internal server error so later logging will pick up SQUID_LOG_ERR_DNS_FAIL
        build_error_response(s, HTTP_STATUS_INTERNAL_SERVER_ERROR, "Cannot find server.", Dns_error_body);
        log_msg = "looking up";
      } else {
        build_error_response(s, HTTP_STATUS_INTERNAL_SERVER_ERROR, "No valid server.", "connect#all_down");
        log_msg = "no valid server";
      }
      char *url_str = s->hdr_info.client_request.url_string_get(&s->arena, nullptr);
      swoc::bwprint(error_bw_buffer, "DNS Error: {} {}", log_msg, swoc::bwf::FirstOf(url_str, "<none>"));
      Log::error("%s", error_bw_buffer.c_str());
      // s->cache_info.action = CACHE_DO_NO_ACTION;
      TRANSACT_RETURN(SM_ACTION_SEND_ERROR_CACHE_NOOP, nullptr);
    }
    return;
  }

  // The dns lookup succeeded
  ink_assert(s->dns_info.resolved_p);
  TxnDbg(dbg_ctl_http_seq, "DNS Lookup successful");

  // It's never valid to connect *to* INADDR_ANY, so let's reject the request now.
  if (ats_is_ip_any(s->dns_info.addr)) {
    TxnDbg(dbg_ctl_http_trans, "[OSDNSLookup] Invalid request IP: INADDR_ANY");
    build_error_response(s, HTTP_STATUS_BAD_REQUEST, "Bad Destination Address", "request#syntax_error");
    SET_VIA_STRING(VIA_DETAIL_TUNNEL, VIA_DETAIL_TUNNEL_NO_FORWARD);
    TRANSACT_RETURN(SM_ACTION_SEND_ERROR_CACHE_NOOP, nullptr);
  }