/** @file

  A brief file description

  @section license License

  Licensed to the Apache Software Foundation (ASF) under one
  or more contributor license agreements.  See the NOTICE file
  distributed with this work for additional information
  regarding copyright ownership.  The ASF licenses this file
  to you under the Apache License, Version 2.0 (the
  "License"); you may not use this file except in compliance
  with the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
 */

#include "proxy/http3/Http3SessionAccept.h"

#include "../../iocore/net/P_Net.h"
#include "iocore/utils/Machine.h"
#include "proxy/IPAllow.h"
#include "iocore/net/TLSSNISupport.h"
#include "iocore/net/QUICSupport.h"

#include "proxy/http3/Http09App.h"
#include "proxy/http3/Http3App.h"

#if TS_USE_QMUX
#include "iocore/net/qmux/QMuxConnection.h"
#endif

namespace
{
DbgCtl dbg_ctl_http3{"http3"};

} // end anonymous namespace

Http3SessionAccept::Http3SessionAccept(OptionsHandle options, HttpProxyPort *proxy_port)
  : HttpSessionAcceptBase(std::move(options), proxy_port)
{
  SET_HANDLER(&Http3SessionAccept::mainEvent);
}

Http3SessionAccept::~Http3SessionAccept() {}

Http3SessionAccept::AppType
Http3SessionAccept::select_app_type(std::string_view alpn)
{
  if (alpn.empty()) {
    return AppType::UNKNOWN;
  }
  if (IP_PROTO_TAG_HTTP_QUIC.compare(alpn) == 0 || IP_PROTO_TAG_HTTP_QUIC_D29.compare(alpn) == 0) {
    return AppType::HTTP_09;
  } else if (IP_PROTO_TAG_HTTP_3.compare(alpn) == 0 || IP_PROTO_TAG_HTTP_3_D29.compare(alpn) == 0 ||
             IP_PROTO_TAG_H3QX.compare(alpn) == 0) {
    return AppType::HTTP_3;
  }
  return AppType::UNKNOWN;
}

bool
Http3SessionAccept::accept(NetVConnection *netvc, MIOBuffer * /* iobuf ATS_UNUSED */, IOBufferReader * /* reader ATS_UNUSED */)
{
  sockaddr const *client_ip   = netvc->get_remote_addr();
  IpAllow::ACL    session_acl = IpAllow::match(client_ip, IpAllow::match_key_t::SRC_ADDR);
  if (!session_acl.isValid()) {
    ip_port_text_buffer ipb;
    Warning("QUIC client '%s' prohibited by ip-allow policy", ats_ip_ntop(client_ip, ipb, sizeof(ipb)));
    return false;
  }
  // RFC9114, section 3.2-2: Client must send the SNI extension.
  if (auto sni = netvc->get_service<TLSSNISupport>(); !sni || sni->get_sni_server_name()[0] == '\0') {
    ip_port_text_buffer ipb;
    Dbg(dbg_ctl_http3, "SNI not found in connection from %s.", ats_ip_nptop(client_ip, ipb, sizeof(ipb)));
    return false;
  }

  netvc->attributes = this->options().transport_type;

  QUICConnection *qc = netvc->get_service<QUICSupport>()->get_quic_connection();

  if (dbg_ctl_http3.on()) {
    ip_port_text_buffer ipb;

    DbgPrint(dbg_ctl_http3, "[%s] accepted connection from %s transport type = %d", qc->cids().data(),
             ats_ip_nptop(client_ip, ipb, sizeof(ipb)), netvc->attributes);
  }
  std::string_view alpn = qc->negotiated_application_name();

  switch (select_app_type(alpn)) {
  case AppType::HTTP_09:
    Dbg(dbg_ctl_http3, "[%s] start HTTP/0.9 app (ALPN=%.*s)", qc->cids().data(), static_cast<int>(alpn.length()), alpn.data());
    new Http09App(netvc, qc, std::move(session_acl), this);
    break;
  case AppType::HTTP_3: {
    Dbg(dbg_ctl_http3, "[%s] start HTTP/3 app (ALPN=%.*s)", qc->cids().data(), static_cast<int>(alpn.length()), alpn.data());

    Http3App *app = new Http3App(netvc, qc, std::move(session_acl), this);

#if TS_USE_QMUX
    if (IP_PROTO_TAG_H3QX.compare(alpn) == 0) {
      // Http3App's constructor runs the generic ProxySession start-up (HQSession::start()),
      // which claims the netvc's read/write VIOs for itself. Reclaim them for QMuxConnection
      // here, after that clobber and before app->start() can generate any stream I/O that
      // would need them.
      auto *qmux_con = dynamic_cast<QMuxConnection *>(qc);
      if (!qmux_con) {
        ink_abort("negotiated h3qx-01 but QUICConnection is not a QMuxConnection");
      }
      qmux_con->start(netvc);
    }
#endif

    app->start();
    break;
  }
  case AppType::UNKNOWN:
  default: {
    // QUIC/TLS can complete without an ALPN extension, leaving the negotiated
    // name empty, and a client may also offer an unrecognized tag.
    ip_port_text_buffer ipb;
    Dbg(dbg_ctl_http3, "[%s] unknown or missing ALPN (ALPN=%.*s) from %s, closing connection", qc->cids().data(),
        static_cast<int>(alpn.length()), alpn.data(), ats_ip_nptop(client_ip, ipb, sizeof(ipb)));
    return false;
  }
  }

  return true;
}

int
Http3SessionAccept::mainEvent(int event, void *data)
{
  NetVConnection *netvc;
  ink_release_assert(event == NET_EVENT_ACCEPT || event == EVENT_ERROR);
  ink_release_assert((event == NET_EVENT_ACCEPT) ? (data != nullptr) : (1));

  if (event == NET_EVENT_ACCEPT) {
    netvc = static_cast<NetVConnection *>(data);
    if (!this->accept(netvc, nullptr, nullptr)) {
      netvc->do_io_close();
    }
    return EVENT_CONT;
  }

  return EVENT_CONT;
}