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/***************************************************************************
 * nsock_engines.c -- This contains the functions and definitions to       *
 * manage the list of available IO engines.  Each IO engine leverages a    *
 * specific IO notification function to wait for events.  Nsock will try   *
 * to use the most efficient engine for your system.                       *
 *                                                                         *
 ***********************IMPORTANT NSOCK LICENSE TERMS***********************
 *
 * The nsock parallel socket event library is (C) 1999-2023 Nmap Software LLC
 * This library is free software; you may redistribute and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; Version 2. This guarantees your right to use, modify, and
 * redistribute this software under certain conditions. If this license is
 * unacceptable to you, Nmap Software LLC may be willing to sell alternative
 * licenses (contact sales@nmap.com ).
 *
 * As a special exception to the GPL terms, Nmap Software LLC grants permission
 * to link the code of this program with any version of the OpenSSL library
 * which is distributed under a license identical to that listed in the included
 * docs/licenses/OpenSSL.txt file, and distribute linked combinations including
 * the two. You must obey the GNU GPL in all respects for all of the code used
 * other than OpenSSL. If you modify this file, you may extend this exception to
 * your version of the file, but you are not obligated to do so.
 *
 * If you received these files with a written license agreement stating terms
 * other than the (GPL) terms above, then that alternative license agreement
 * takes precedence over this comment.
 *
 * Source is provided to this software because we believe users have a right to
 * know exactly what a program is going to do before they run it. This also
 * allows you to audit the software for security holes.
 *
 * Source code also allows you to port Nmap to new platforms, fix bugs, and add
 * new features. You are highly encouraged to send your changes to the
 * dev@nmap.org mailing list for possible incorporation into the main
 * distribution. By sending these changes to Fyodor or one of the Insecure.Org
 * development mailing lists, or checking them into the Nmap source code
 * repository, it is understood (unless you specify otherwise) that you are
 * offering the Nmap Project (Nmap Software LLC) the unlimited, non-exclusive
 * right to reuse, modify, and relicense the code. Nmap will always be available
 * Open Source, but this is important because the inability to relicense code
 * has caused devastating problems for other Free Software projects (such as KDE
 * and NASM). We also occasionally relicense the code to third parties as
 * discussed above. If you wish to specify special license conditions of your
 * contributions, just say so when you send them.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License v2.0 for more
 * details (http://www.gnu.org/licenses/gpl-2.0.html).
 *
 ***************************************************************************/

/* $Id$ */

#ifdef HAVE_CONFIG_H
#include "nsock_config.h"
#endif

#include "nsock_internal.h"

#if HAVE_IOCP
  extern struct io_engine engine_iocp;
  #define ENGINE_IOCP &engine_iocp,
#else
  #define ENGINE_IOCP
#endif /* HAVE_IOCP */

#if HAVE_EPOLL
  extern struct io_engine engine_epoll;
  #define ENGINE_EPOLL &engine_epoll,
#else
  #define ENGINE_EPOLL
#endif /* HAVE_EPOLL */

#if HAVE_KQUEUE
  extern struct io_engine engine_kqueue;
  #define ENGINE_KQUEUE &engine_kqueue,
#else
  #define ENGINE_KQUEUE
#endif /* HAVE_KQUEUE */

#if HAVE_POLL
  extern struct io_engine engine_poll;
  #define ENGINE_POLL &engine_poll,
#else
  #define ENGINE_POLL
#endif /* HAVE_POLL */

/* select() based engine is the fallback engine, we assume it's always available */
extern struct io_engine engine_select;
#define ENGINE_SELECT &engine_select,

/* Available IO engines. This depends on which IO management interfaces are
 * available on your system. Engines must be sorted by order of preference */
static struct io_engine *available_engines[] = {
  ENGINE_EPOLL
  ENGINE_KQUEUE
  ENGINE_POLL
  ENGINE_IOCP
  ENGINE_SELECT
  NULL
};

static char *engine_hint;

int posix_iod_connect(struct npool *nsp, int sockfd, const struct sockaddr *addr, socklen_t addrlen) {
  return connect(sockfd, addr, addrlen);
}

int posix_iod_read(struct npool *nsp, int sockfd, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen) {
  return recvfrom(sockfd, (char *)buf, len, flags, src_addr, addrlen);
}

int posix_iod_write(struct npool *nsp, int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen) {
  struct sockaddr_storage *dest = (struct sockaddr_storage *)dest_addr;
  if (dest->ss_family == AF_UNSPEC)
    return send(sockfd, (char *)buf, len, flags);
  else
    return sendto(sockfd, (char *)buf, len, flags, dest_addr, addrlen);
}

struct io_operations posix_io_operations = {
  posix_iod_connect,
  posix_iod_read,
  posix_iod_write
};

struct io_engine *get_io_engine(void) {
  struct io_engine *engine = NULL;
  int i;

  if (!engine_hint) {
    engine = available_engines[0];
  } else {
    for (i = 0; available_engines[i] != NULL; i++)
      if (strcmp(engine_hint, available_engines[i]->name) == 0) {
        engine = available_engines[i];
        break;
      }
  }

  if (!engine)
    fatal("No suitable IO engine found! (%s)\n",
          engine_hint ? engine_hint : "no hint");

  return engine;
}

int nsock_set_default_engine(char *engine) {
  if (engine_hint)
    free(engine_hint);

  if (engine) {
    int i;

    for (i = 0; available_engines[i] != NULL; i++) {
      if (strcmp(engine, available_engines[i]->name) == 0) {
        engine_hint = strdup(engine);
        return 0;
      }
    }
    return -1;
  }
  /* having engine = NULL is fine. This is actually the
   * way to tell nsock to use the default engine again. */
  engine_hint = NULL;
  return 0;
}

const char *nsock_list_engines(void) {
  return
#if HAVE_IOCP
  "iocp "
#endif
#if HAVE_EPOLL
  "epoll "
#endif
#if HAVE_KQUEUE
  "kqueue "
#endif
#if HAVE_POLL
  "poll "
#endif
  "select";
}