nmap/nsock/src/nsock_pcap.h

/***************************************************************************
 * nsock_pcap.h -- Header for pcap operations functions from               *
 * the nsock parallel socket event library                                 *
 *                                                                         *
 ***********************IMPORTANT NSOCK LICENSE TERMS***********************
 *
 * The nsock parallel socket event library is (C) 1999-2025 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).
 *
 ***************************************************************************/

/* $Id$ */

#ifndef NSOCK_PCAP_H
#define NSOCK_PCAP_H

#include "nsock_internal.h"
#ifdef HAVE_PCAP

#include "pcap.h"

#include <string.h>
#include <stdarg.h>

/*
 * There are three possible ways to read packets from pcap descriptor:
 *  - select() on descriptor:
 *      this one is of course the best, but there are systems that
 *      don't support this like WIN32. This works perfectly for Linux.
 *
 *  - select() + some hacks:
 *      this one is hack for older bsd systems,
 *      Descriptor *must* be set in nonblocking mode.
 *
 *   - never do select():
 *      this one is for WIN32 and other systems that return descriptor -1
 *      from pcap_get_selectable_fd().
 *      In this case descriptor *must* be set in nonblocking mode.
 *      If that fails than we can't do any sniffing from that box.
 *
 * In any case we try to set descriptor to non-blocking mode.
 */

/* Returns whether the system supports pcap_get_selectable_fd() properly */
#if !defined(WIN32) && !defined(SOLARIS_BPF_PCAP_CAPTURE)
#define PCAP_CAN_DO_SELECT 1
#endif

/* In some systems (like Windows), the pcap descriptor is not selectable.
 * Therefore, we cannot just select() on it and expect it to wake us up and
 * deliver a packet, but we need to poll it continuously. This define sets the
 * frequency, in milliseconds, at which the pcap handle is polled to determine
 * if there are any captured packets.  Note that this is only used when
 * PCAP_CAN_DO_SELECT is not defined and therefore it has no effect on systems
 * like Linux.
 */
#define PCAP_POLL_INTERVAL 2

/* Note that on most versions of most BSDs (including Mac OS X) select() and
 * poll() do not work correctly on BPF devices; pcap_get_selectable_fd() will
 * return a file descriptor on most of those versions (the exceptions being
 * FreeBSD 4.3 and 4.4), a simple select() or poll() will not return even after
 * a timeout specified in pcap_open_live() expires. To work around this, an
 * application that uses select() or poll() to wait for packets to arrive must
 * put the pcap_t in non-blocking mode, and must arrange that the select() or
 * poll() have a timeout less than or equal to the timeout specified in
 * pcap_open_live(), and must try to read packets after that timeout expires,
 * regardless of whether select() or poll() indicated that the file descriptor
 * for the pcap_t is ready to be read or not. (That workaround will not work in
 * FreeBSD 4.3 and later; however, in FreeBSD 4.6 and later, select() and poll()
 * work correctly on BPF devices, so the workaround isn't necessary, although it
 * does no harm.)
 */
#if defined(MACOSX) || defined(FREEBSD) || defined(OPENBSD)
/* Well, now select() is not receiving any pcap events on MACOSX, but maybe it
 * will someday :) in both cases. It never hurts to enable this feature. It just
 * has performance penalty. */
#define PCAP_BSD_SELECT_HACK 1
#endif

/* Returns whether the packet receive time value obtained from libpcap
 * (and thus by readip_pcap()) should be considered valid.  When
 * invalid (Windows and Amiga), readip_pcap returns the time you called it. */
#if !defined(WIN32) && !defined(__amigaos__)
#define PCAP_RECV_TIMEVAL_VALID 1
#endif


typedef struct{
  pcap_t *pt;
  int pcap_desc;
  /* Like the corresponding member in iod, when this reaches 0 we stop
   * watching the socket for readability. */
  int readsd_count;
  int datalink;
  int l3_offset;
  int snaplen;
  char *pcap_device;
} mspcap;

typedef struct{
  struct timeval ts;
  int caplen;
  int len;
  const unsigned char *packet;  /* caplen bytes */
} nsock_pcap;

int do_actual_pcap_read(struct nevent *nse);

#endif /* HAVE_PCAP */
#endif /* NSOCK_PCAP_H */