xref: /freebsd/sys/netinet/libalias/alias.h (revision 61bf830cbb260c2a046cb44421d319184393e028)

/* lint -save -library Flexelint comment for external headers */

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2001 Charles Mott <cm@linktel.net>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Alias.h defines the outside world interfaces for the packet aliasing
 * software.
 *
 * This software is placed into the public domain with no restrictions on its
 * distribution.
 */

#ifndef _ALIAS_H_
#define	_ALIAS_H_

#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>

#define LIBALIAS_BUF_SIZE 128
#ifdef _KERNEL
/*
 * The kernel version of libalias does not support these features.
 */
#define	NO_FW_PUNCH
#define	NO_USE_SOCKETS
#endif

/*
 * The external interface to libalias, the packet aliasing engine.
 *
 * There are two sets of functions:
 *
 * PacketAlias*() the old API which doesn't take an instance pointer
 * and therefore can only have one packet engine at a time.
 *
 * LibAlias*() the new API which takes as first argument a pointer to
 * the instance of the packet aliasing engine.
 *
 * The functions otherwise correspond to each other one for one, except
 * for the LibAliasUnaliasOut()/PacketUnaliasOut() function which were
 * were misnamed in the old API.
 */

/*
 * The instance structure
 */
struct libalias;

/*
 * An anonymous structure, a pointer to which is returned from
 * PacketAliasRedirectAddr(), PacketAliasRedirectPort() or
 * PacketAliasRedirectProto(), passed to PacketAliasAddServer(),
 * and freed by PacketAliasRedirectDelete().
 */
struct alias_link;

/* Initialization and control functions. */
struct libalias *LibAliasInit(struct libalias *);
void		LibAliasSetAddress(struct libalias *, struct in_addr _addr);
void		LibAliasSetAliasPortRange(struct libalias *la, u_short port_low, u_short port_hi);
void		LibAliasSetFWBase(struct libalias *, unsigned int _base, unsigned int _num);
void		LibAliasSetSkinnyPort(struct libalias *, unsigned int _port);
unsigned int	LibAliasSetMode(struct libalias *, unsigned int _flags, unsigned int _mask);
void		LibAliasUninit(struct libalias *);

/* Packet Handling functions. */
int		LibAliasIn (struct libalias *, void *_ptr, int _maxpacketsize);
int		LibAliasOut(struct libalias *, void *_ptr, int _maxpacketsize);
int		LibAliasOutTry(struct libalias *, void *_ptr, int _maxpacketsize, int _create);
int		LibAliasUnaliasOut(struct libalias *, void *_ptr, int _maxpacketsize);

/* Port and address redirection functions. */

int		LibAliasAddServer(struct libalias *, struct alias_link *_lnk,
		    struct in_addr _addr, unsigned short _port);
struct alias_link * LibAliasRedirectAddr(struct libalias *, struct in_addr _src_addr,
		    struct in_addr _alias_addr);
int		LibAliasRedirectDynamic(struct libalias *, struct alias_link *_lnk);
void		LibAliasRedirectDelete(struct libalias *, struct alias_link *_lnk);
struct alias_link * LibAliasRedirectPort(struct libalias *, struct in_addr _src_addr,
		    unsigned short _src_port, struct in_addr _dst_addr,
		    unsigned short _dst_port, struct in_addr _alias_addr,
		    unsigned short _alias_port, unsigned char _proto);
struct alias_link * LibAliasRedirectProto(struct libalias *, struct in_addr _src_addr,
		    struct in_addr _dst_addr, struct in_addr _alias_addr,
		    unsigned char _proto);

/* Fragment Handling functions. */
void		LibAliasFragmentIn(struct libalias *, void *_ptr, void *_ptr_fragment);
void	       *LibAliasGetFragment(struct libalias *, void *_ptr);
int		LibAliasSaveFragment(struct libalias *, void *_ptr);

/* Miscellaneous functions. */
unsigned short	LibAliasInternetChecksum(struct libalias *, unsigned short *_ptr, int _nbytes);
void		LibAliasSetTarget(struct libalias *, struct in_addr _target_addr);

/* Transparent proxying routines. */
int		LibAliasProxyRule(struct libalias *, const char *_cmd);

/* Module handling API */
int		LibAliasLoadModule(char *);
int		LibAliasUnLoadAllModule(void);
int		LibAliasRefreshModules(void);

/* Mbuf helper function. */
struct mbuf    *m_megapullup(struct mbuf *, int);

/*
 * Mode flags and other constants.
 */

/* Mode flags, set using PacketAliasSetMode() */

/*
 * If PKT_ALIAS_LOG is set, a message will be printed to /var/log/alias.log
 * every time a link is created or deleted.  This is useful for debugging.
 */
#define	PKT_ALIAS_LOG			0x01

/*
 * If PKT_ALIAS_DENY_INCOMING is set, then incoming connections (e.g. to ftp,
 * telnet or web servers will be prevented by the aliasing mechanism.
 */
#define	PKT_ALIAS_DENY_INCOMING		0x02

/*
 * If PKT_ALIAS_SAME_PORTS is set, packets will be attempted sent from the
 * same port as they originated on.  This allows e.g. rsh to work *99% of the
 * time*, but _not_ 100% (it will be slightly flakey instead of not working
 * at all).  This mode bit is set by PacketAliasInit(), so it is a default
 * mode of operation.
 */
#define	PKT_ALIAS_SAME_PORTS		0x04

/*
 * If PKT_ALIAS_USE_SOCKETS is set, then when partially specified links (e.g.
 * destination port and/or address is zero), the packet aliasing engine will
 * attempt to allocate a socket for the aliasing port it chooses.  This will
 * avoid interference with the host machine.  Fully specified links do not
 * require this.  This bit is set after a call to PacketAliasInit(), so it is
 * a default mode of operation.
 */
#ifndef NO_USE_SOCKETS
#define	PKT_ALIAS_USE_SOCKETS		0x08
#endif
/*-
 * If PKT_ALIAS_UNREGISTERED_ONLY is set, then only packets with
 * unregistered source addresses will be aliased.  Private
 * addresses are those in the following ranges:
 *
 *		10.0.0.0     ->   10.255.255.255
 *		172.16.0.0   ->   172.31.255.255
 *		192.168.0.0  ->   192.168.255.255
 */
#define	PKT_ALIAS_UNREGISTERED_ONLY	0x10

/*
 * If PKT_ALIAS_RESET_ON_ADDR_CHANGE is set, then the table of dynamic
 * aliasing links will be reset whenever PacketAliasSetAddress() changes the
 * default aliasing address.  If the default aliasing address is left
 * unchanged by this function call, then the table of dynamic aliasing links
 * will be left intact.  This bit is set after a call to PacketAliasInit().
 */
#define	PKT_ALIAS_RESET_ON_ADDR_CHANGE	0x20

/*
 * If PKT_ALIAS_PROXY_ONLY is set, then NAT will be disabled and only
 * transparent proxying is performed.
 */
#define	PKT_ALIAS_PROXY_ONLY		0x40

/*
 * If PKT_ALIAS_REVERSE is set, the actions of PacketAliasIn() and
 * PacketAliasOut() are reversed.
 */
#define	PKT_ALIAS_REVERSE		0x80

#ifndef NO_FW_PUNCH
/*
 * If PKT_ALIAS_PUNCH_FW is set, active FTP and IRC DCC connections will
 * create a 'hole' in the firewall to allow the transfers to work.  The
 * ipfw rule number that the hole is created with is controlled by
 * PacketAliasSetFWBase().  The hole will be attached to that
 * particular alias_link, so when the link goes away the hole is deleted.
 */
#define	PKT_ALIAS_PUNCH_FW		0x100
#endif

/*
 * If PKT_ALIAS_SKIP_GLOBAL is set, nat instance is not checked for matching
 * states in 'ipfw nat global' rule.
 */
#define	PKT_ALIAS_SKIP_GLOBAL		0x200

/*
 * Like PKT_ALIAS_UNREGISTERED_ONLY, but includes the RFC 6598
 * (Carrier Grade NAT) address range as follows:
 *
 *		100.64.0.0   ->   100.127.255.255
 */
#define	PKT_ALIAS_UNREGISTERED_CGN	0x400

/*
 * When this bit is set, UDP uses endpoint-independent mapping (EIM), as per
 * RFC 4787 ("full cone" NAT of RFC 3489). All packets from the same internal
 * address:port are mapped to the same NAT address:port, regardless of their
 * destination address:port. If filtering rules allow, and if
 * PKT_ALIAS_DENY_INCOMING is unset, any other external address:port can also
 * send to the internal address:port through its mapped NAT address:port. This
 * is more compatible with applications, and can reduce the need for port
 * forwarding, but less scalable as each NAT address:port can only be
 * concurrently used by at most one internal address:port.
 *
 * When this bit is unset, UDP packets use endpoint-dependent mapping (EDM)
 * ("symmetric" NAT). Each connection from a particular internal address:port
 * to different external addresses:ports is mapped to a random and
 * unpredictable NAT address:port. Two appplications behind EDM NATs can only
 * connect to each other by port forwarding on the NAT, or tunnelling through
 * an in-between server.
 */
#define PKT_ALIAS_UDP_EIM		0x800

/* Function return codes. */
#define	PKT_ALIAS_ERROR			-1
#define	PKT_ALIAS_OK			1
#define	PKT_ALIAS_IGNORED		2
#define	PKT_ALIAS_UNRESOLVED_FRAGMENT	3
#define	PKT_ALIAS_FOUND_HEADER_FRAGMENT	4

#endif				/* !_ALIAS_H_ */

/* lint -restore */