class NetworkContext extends RequestStackCacheContextBase implements CacheContextInterface {

  /**
   * {@inheritdoc}
   */
  public static function getLabel() {
    return t('Network');
  }

  /**
   * {@inheritdoc}
   */
  public function getContext() {
    if (Util::requestFromCampus($this->requestStack->getCurrentRequest()->getClientIp())) {
      return 'oncampus';
    }
    else {
      return 'offcampus';
    }
  }

  /**
   * {@inheritdoc}
   */
  public function getCacheableMetadata() {
    return new CacheableMetadata();
  }

}

public function myCustomAction(Request $request) {
  $build = [];

  $build['my_data'] = [
    '#theme' => 'my_custom_theme_function',
    '#rawdata' => $this->fetchData(Util::requestIsFromCampus($request->getClientIp()));
  ];

  // Add some cache metadata that indicates this render array varies
  // based on the user's network. We can't effectively use cache tags
  // here since the data is retrieved from an external service and we
  // don't know when it's updated. Instead, expire the result after
  // one hour.
  $build['#cache'] = [
    'max-age' => 60 * 60,
    'contexts' => [
      'network',
    ],
  ];

  return $build;
}

public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
    $ip = $request->getClientIp();
    if (Util::requestFromCampus($ip)) {
      $request->query->add(['oncampus' => '1']);
    }
    else {
      // remove the query parameter in case an off-campus user sets it incorrectly
      $request->query->remove('oncampus');
    }
    return $this->httpKernel->handle($request, $type, $catch);
  }

<?php

namespace Drupalmy_moduleEventSubscriber;

/**
 * Class MyCustomSubscriber.
 */
class MyCustomSubscriber implements EventSubscriberInterface {

  public static function getSubscribedEvents() {
    $events[KernelEvents::REQUEST] = ['myCustomRedirect', 28];
    return $events;
  }

  public function myCustomRedirect(GetResponseEvent $response, $event, ContainerAwareEventDispatcher $event_dispatcher) {
    if (Drupal::service('router.admin_context')->isAdminRoute()) {
      return;
    }

    Drupal::service('page_cache_kill_switch')->trigger();

    // ...

  }
}