generic.hpp

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//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012- OpenVPN Inc.
//
//    SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
 
#ifndef OPENVPN_CLIENT_ASYNC_RESOLVE_GENERIC_H
#define OPENVPN_CLIENT_ASYNC_RESOLVE_GENERIC_H
 
#include <openvpn/common/bigmutex.hpp>
#include <openvpn/common/rc.hpp>
#include <openvpn/common/hostport.hpp>
 
 
namespace openvpn {
template <typename RESOLVER_TYPE>
class AsyncResolvable : public virtual RC<thread_unsafe_refcount>
{
  private:
    typedef RCPtr<AsyncResolvable> Ptr;
 
    openvpn_io::io_context &io_context;
    RESOLVER_TYPE resolver;
 
  public:
    using resolver_type = RESOLVER_TYPE;
    using results_type = typename RESOLVER_TYPE::results_type;
 
    AsyncResolvable(openvpn_io::io_context &io_context_arg)
        : io_context(io_context_arg),
          resolver(io_context_arg)
    {
    }
 
    virtual void resolve_callback(const openvpn_io::error_code &error,
                                  results_type results) = 0;
 
    // This implementation assumes that the i/o reactor provides an asynchronous
    // DNS resolution routine using its own primitives and that doesn't require
    // us to take care of any non-interruptible opration (i.e. getaddrinfo() in
    // case of ASIO).
    //
    // For example, iOS implements aync_resolve using GCD and CFHost. This
    // implementation satisfies the constraints mentioned above
    virtual void async_resolve_name(const std::string &host, const std::string &port)
    {
        resolver.async_resolve(host,
                               port,
                               [self = Ptr(this)](const openvpn_io::error_code &error, results_type results)
                               {
      OPENVPN_ASYNC_HANDLER;
      self->resolve_callback(error, results); });
    }
 
    // no-op: needed to provide the same class signature of the ASIO version
    void async_resolve_lock()
    {
    }
 
    void async_resolve_cancel()
    {
        resolver.cancel();
    }
};
} // namespace openvpn
 
#endif /* OPENVPN_CLIENT_ASYNC_RESOLVE_GENERIC_H */