Method PPDNSLookup

src/proxy/http/HttpTransact.cc:1810–1871

- HttpTransact::SM_ACTION_DNS_LOOKUP; - HttpTransact::ORIGIN_SERVER_RAW_OPEN; - HttpTransact::ORIGIN_SERVER_OPEN; //////////////////////////////////////////////////////////////////////////

//
///////////////////////////////////////////////////////////////////////////////
void
HttpTransact::PPDNSLookup(State *s)
{
  TxnDbg(dbg_ctl_http_trans, "Entering HttpTransact::PPDNSLookup");

  ink_assert(s->dns_info.looking_up == ResolveInfo::PARENT_PROXY);
  if (!s->dns_info.resolved_p) {
    // Mark parent as down due to resolving failure
    markParentDown(s);
    // DNS lookup of parent failed, find next parent or o.s.
    if (find_server_and_update_current_info(s) == ResolveInfo::HOST_NONE) {
      if (is_cache_hit(s->cache_lookup_result) && is_stale_cache_response_returnable(s)) {
        s->source = SOURCE_CACHE;
        TxnDbg(dbg_ctl_http_trans, "All parents are down, serving stale doc to client");
        build_response_from_cache(s, HTTP_WARNING_CODE_REVALIDATION_FAILED);
        return;
      }
      ink_assert(s->current.request_to == ResolveInfo::HOST_NONE);
      handle_parent_down(s);
      return;
    }

    if (!s->current.server->dst_addr.isValid()) {
      if (s->current.request_to == ResolveInfo::PARENT_PROXY) {
        TRANSACT_RETURN(SM_ACTION_DNS_LOOKUP, PPDNSLookupAPICall);
      } else if (s->parent_result.result == PARENT_DIRECT && s->txn_conf->no_dns_forward_to_parent != 1) {
        // We ran out of parents but parent configuration allows us to go to Origin Server directly
        CallOSDNSLookup(s);
        return;
      } else {
        // We could be out of parents here if all the parents failed DNS lookup
        ink_assert(s->current.request_to == ResolveInfo::HOST_NONE);
        handle_parent_down(s);
      }
      return;
    }
  } else {
    // lookup succeeded, open connection to p.p.
    ats_ip_copy(&s->parent_info.dst_addr, s->dns_info.addr);
    s->parent_info.dst_addr.network_order_port() = htons(s->parent_result.port);
    get_ka_info_from_host_db(s, &s->parent_info, &s->client_info, s->dns_info.active);

    ip_port_text_buffer addrbuf;
    TxnDbg(dbg_ctl_http_trans, "DNS lookup for successful IP: %s",
           ats_ip_nptop(&s->parent_info.dst_addr.sa, addrbuf, sizeof(addrbuf)));
  }

  // Since this function can be called several times while retrying
  //  parents, check to see if we've already built our request
  if (!s->hdr_info.server_request.valid()) {
    build_request(s, &s->hdr_info.client_request, &s->hdr_info.server_request, s->current.server->http_version);
    // Take care of deferred (issue revalidate) work in building
    //   the request
    if (s->pending_work != nullptr) {
      ink_assert(s->pending_work == issue_revalidate);
      (*s->pending_work)(s);
      s->pending_work = nullptr;
    }