static EarlyDataType negotiateEarlyDataType()

in fizz/server/ServerProtocol.cpp [823:891]
59 lines of code
15 McCabe index (conditional complexity)

static EarlyDataType negotiateEarlyDataType(
    bool acceptEarlyData,
    const ClientHello& chlo,
    const Optional<ResumptionState>& psk,
    CipherSuite cipher,
    Optional<KeyExchangeType> keyExchangeType,
    const Optional<CookieState>& cookieState,
    Optional<std::string> alpn,
    ReplayCacheResult replayCacheResult,
    Optional<std::chrono::milliseconds> clockSkew,
    ClockSkewTolerance clockSkewTolerance,
    const AppTokenValidator* appTokenValidator) {
  if (!getExtension<ClientEarlyData>(chlo.extensions)) {
    return EarlyDataType::NotAttempted;
  }

  if (!acceptEarlyData) {
    VLOG(5) << "Rejecting early data: disabled";
    return EarlyDataType::Rejected;
  }

  if (!psk) {
    VLOG(5) << "Rejected early data: psk rejected";
    return EarlyDataType::Rejected;
  }

  if (psk->cipher != cipher) {
    VLOG(5) << "Rejected early data: cipher mismatch";
    return EarlyDataType::Rejected;
  }

  if (psk->alpn != alpn) {
    VLOG(5) << "Rejecting early data: alpn mismatch";
    return EarlyDataType::Rejected;
  }

  if (keyExchangeType &&
      *keyExchangeType == KeyExchangeType::HelloRetryRequest) {
    VLOG(5) << "Rejecting early data: HelloRetryRequest";
    return EarlyDataType::Rejected;
  }

  if (cookieState) {
    VLOG(5) << "Rejecting early data: Cookie";
    return EarlyDataType::Rejected;
  }

  if (replayCacheResult != ReplayCacheResult::NotReplay) {
    VLOG(5) << "Rejecting early data: replay";
    return EarlyDataType::Rejected;
  }

  if (!clockSkew || *clockSkew < clockSkewTolerance.before ||
      *clockSkew > clockSkewTolerance.after) {
    VLOG(5) << "Rejecting early data: clock skew clockSkew="
            << (clockSkew ? folly::to<std::string>(clockSkew->count())
                          : "(none)")
            << " toleranceBefore=" << clockSkewTolerance.before.count()
            << " toleranceAfter=" << clockSkewTolerance.after.count();
    return EarlyDataType::Rejected;
  }

  if (appTokenValidator && !appTokenValidator->validate(*psk)) {
    VLOG(5) << "Rejecting early data: invalid app token";
    return EarlyDataType::Rejected;
  }

  return EarlyDataType::Accepted;
}