curl/lib/asyn.h

#ifndef HEADER_CURL_ASYN_H
#define HEADER_CURL_ASYN_H
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/

#include "curl_setup.h"

struct Curl_easy;
struct Curl_dns_entry;

#ifdef CURLRES_ASYNCH

#include "curl_addrinfo.h"
#include "httpsrr.h"

struct addrinfo;
struct hostent;
struct connectdata;

#if defined(CURLRES_ARES) && defined(CURLRES_THREADED)
#error cannot have both CURLRES_ARES and CURLRES_THREADED defined
#endif

/*
 * This header defines all functions in the internal asynch resolver interface.
 * All asynch resolvers need to provide these functions.
 * asyn-ares.c and asyn-thread.c are the current implementations of asynch
 * resolver backends.
 */

/*
 * Curl_async_global_init()
 *
 * Called from curl_global_init() to initialize global resolver environment.
 * Returning anything else than CURLE_OK fails curl_global_init().
 */
int Curl_async_global_init(void);

/*
 * Curl_async_global_cleanup()
 * Called from curl_global_cleanup() to destroy global resolver environment.
 */
void Curl_async_global_cleanup(void);

/*
 * Curl_async_get_impl()
 * Get the resolver implementation instance (c-ares channel) or NULL
 * for passing to application callback.
 */
CURLcode Curl_async_get_impl(struct Curl_easy *easy, void **impl);

/* Curl_async_getsock()
 *
 * This function is called from the Curl_multi_getsock() function.  'sock' is a
 * pointer to an array to hold the file descriptors, with 'numsock' being the
 * size of that array (in number of entries). This function is supposed to
 * return bitmask indicating what file descriptors (referring to array indexes
 * in the 'sock' array) to wait for, read/write.
 */
int Curl_async_getsock(struct Curl_easy *data, curl_socket_t *sock);

/*
 * Curl_async_is_resolved()
 *
 * Called repeatedly to check if a previous name resolve request has
 * completed. It should also make sure to time-out if the operation seems to
 * take too long.
 *
 * Returns normal CURLcode errors.
 */
CURLcode Curl_async_is_resolved(struct Curl_easy *data,
                                struct Curl_dns_entry **dns);

/*
 * Curl_async_await()
 *
 * Waits for a resolve to finish. This function should be avoided since using
 * this risk getting the multi interface to "hang".
 *
 * On return 'entry' is assigned the resolved dns (CURLE_OK or NULL otherwise.
 *
 * Returns CURLE_COULDNT_RESOLVE_HOST if the host was not resolved,
 * CURLE_OPERATION_TIMEDOUT if a time-out occurred, or other errors.
 */
CURLcode Curl_async_await(struct Curl_easy *data,
                          struct Curl_dns_entry **dnsentry);

/*
 * Curl_async_getaddrinfo() - when using this resolver
 *
 * Returns name information about the given hostname and port number. If
 * successful, the 'hostent' is returned and the fourth argument will point to
 * memory we need to free after use. That memory *MUST* be freed with
 * Curl_freeaddrinfo(), nothing else.
 *
 * Each resolver backend must of course make sure to return data in the
 * correct format to comply with this.
 */
struct Curl_addrinfo *Curl_async_getaddrinfo(struct Curl_easy *data,
                                             const char *hostname,
                                             int port,
                                             int ip_version,
                                             int *waitp);

#ifdef USE_ARES
/* common functions for c-ares and threaded resolver with HTTPSRR */
#include <ares.h>

int Curl_ares_getsock(struct Curl_easy *data,
                      ares_channel channel,
                      curl_socket_t *socks);
int Curl_ares_perform(ares_channel channel,
                      timediff_t timeout_ms);
#endif

#ifdef CURLRES_ARES
/* async resolving implementation using c-ares alone */
struct async_ares_ctx {
  ares_channel channel;
  int num_pending; /* number of outstanding c-ares requests */
  struct Curl_addrinfo *temp_ai; /* intermediary result while fetching c-ares
                                    parts */
  int last_status;
  CURLcode result; /* CURLE_OK or error handling response */
#ifndef HAVE_CARES_GETADDRINFO
  struct curltime happy_eyeballs_dns_time; /* when this timer started, or 0 */
#endif
#ifdef USE_HTTPSRR
  struct Curl_https_rrinfo hinfo;
#endif
};

void Curl_async_ares_shutdown(struct Curl_easy *data);
void Curl_async_ares_destroy(struct Curl_easy *data);

/*
 * Function provided by the resolver backend to set DNS servers to use.
 */
CURLcode Curl_set_dns_servers(struct Curl_easy *data, char *servers);

/*
 * Function provided by the resolver backend to set
 * outgoing interface to use for DNS requests
 */
CURLcode Curl_set_dns_interface(struct Curl_easy *data,
                                const char *interf);

/*
 * Function provided by the resolver backend to set
 * local IPv4 address to use as source address for DNS requests
 */
CURLcode Curl_set_dns_local_ip4(struct Curl_easy *data,
                                const char *local_ip4);

/*
 * Function provided by the resolver backend to set
 * local IPv6 address to use as source address for DNS requests
 */
CURLcode Curl_set_dns_local_ip6(struct Curl_easy *data,
                                const char *local_ip6);

#endif /* CURLRES_ARES */

#ifdef CURLRES_THREADED
/* async resolving implementation using POSIX threads */
#include "curl_threads.h"

/* Context for threaded address resolver */
struct async_thrdd_addr_ctx {
  curl_thread_t thread_hnd;
  char *hostname;        /* hostname to resolve, Curl_async.hostname
                            duplicate */
  curl_mutex_t mutx;
#ifndef CURL_DISABLE_SOCKETPAIR
  curl_socket_t sock_pair[2]; /* eventfd/pipes/socket pair */
#endif
  struct Curl_addrinfo *res;
#ifdef HAVE_GETADDRINFO
  struct addrinfo hints;
#endif
  struct curltime start;
  timediff_t interval_end;
  unsigned int poll_interval;
  int port;
  int sock_error;
  int ref_count;
};

/* Context for threaded resolver */
struct async_thrdd_ctx {
  /* `addr` is a pointer since this memory is shared with a started
   * thread. Since threads cannot be killed, we use reference counting
   * so that we can "release" our pointer to this memory while the
   * thread is still running. */
  struct async_thrdd_addr_ctx *addr;
#if defined(USE_HTTPSRR) && defined(USE_ARES)
  struct {
    ares_channel channel;
    struct Curl_https_rrinfo hinfo;
    CURLcode result;
    BIT(done);
  } rr;
#endif
};

void Curl_async_thrdd_shutdown(struct Curl_easy *data);
void Curl_async_thrdd_destroy(struct Curl_easy *data);

#endif /* CURLRES_THREADED */

#ifndef CURL_DISABLE_DOH
struct doh_probes;
#endif

#else /* CURLRES_ASYNCH */

/* convert these functions if an asynch resolver is not used */
#define Curl_async_get_impl(x,y)    (*(y) = NULL, CURLE_OK)
#define Curl_async_is_resolved(x,y) CURLE_COULDNT_RESOLVE_HOST
#define Curl_async_await(x,y) CURLE_COULDNT_RESOLVE_HOST
#define Curl_async_global_init() CURLE_OK
#define Curl_async_global_cleanup() Curl_nop_stmt

#endif /* !CURLRES_ASYNCH */

#if defined(CURLRES_ASYNCH) || !defined(CURL_DISABLE_DOH)
#define USE_CURL_ASYNC
#endif

#ifdef USE_CURL_ASYNC
struct Curl_async {
#ifdef CURLRES_ARES /*  */
  struct async_ares_ctx ares;
#elif defined(CURLRES_THREADED)
  struct async_thrdd_ctx thrdd;
#endif
#ifndef CURL_DISABLE_DOH
  struct doh_probes *doh; /* DoH specific data for this request */
#endif
  struct Curl_dns_entry *dns; /* result of resolving on success */
  char *hostname; /* copy of the params resolv started with */
  int port;
  int ip_version;
  BIT(done);
};

/*
 * Curl_async_shutdown().
 *
 * This shuts down all ongoing operations.
 */
void Curl_async_shutdown(struct Curl_easy *data);

/*
 * Curl_async_destroy().
 *
 * This frees the resources of any async resolve.
 */
void Curl_async_destroy(struct Curl_easy *data);
#else /* !USE_CURL_ASYNC */
#define Curl_async_shutdown(x) Curl_nop_stmt
#endif /* USE_CURL_ASYNC */


/********** end of generic resolver interface functions *****************/
#endif /* HEADER_CURL_ASYN_H */