/* encap_util.c
 * Data Link Type (DLT) encapsulation utility definitions
 *
 * $Id$
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#include "encap_util.h"
#include <wiretap/wtap.h>

/*
 * Either LBL NRG wasn't an adequate central registry (e.g., because of
 * the slow rate of releases from them), or nobody bothered using them
 * as a central registry, as many different groups have patched libpcap
 * (and BPF, on the BSDs) to add new encapsulation types, and have ended
 * up using the same DLT_ values for different encapsulation types.
 *
 * For those numerical encapsulation type values that everybody uses for
 * the same encapsulation type (which inclues those that some platforms
 * specify different DLT_ names for but don't appear to use), we map
 * those values to the appropriate Wiretap values.
 *
 * For those numerical encapsulation type values that different libpcap
 * variants use for different encapsulation types, we check what
 * <pcap.h> defined to determine how to interpret them, so that we
 * interpret them the way the libpcap with which we're building
 * Wireshark/Wiretap interprets them (which, if it doesn't support
 * them at all, means we don't support them either - any capture files
 * using them are foreign, and we don't hazard a guess as to which
 * platform they came from; we could, I guess, choose the most likely
 * platform).
 *
 * Note: if you need a new encapsulation type for libpcap files, do
 * *N*O*T* use *ANY* of the values listed here!  I.e., do *NOT*
 * add a new encapsulation type by changing an existing entry;
 * leave the existing entries alone.
 *
 * Instead, send mail to tcpdump-workers@lists.tcpdump.org, asking for
 * a new DLT_ value, and specifying the purpose of the new value.  When
 * you get the new DLT_ value, use that numerical value in the "dlt_value"
 * field of "pcap_to_wtap_map[]".
 */

static const struct {
	int	dlt_value;
	int	wtap_encap_value;
} pcap_to_wtap_map[] = {
	/*
	 * These are the values that are almost certainly the same
	 * in all libpcaps (I've yet to find one where the values
	 * in question are used for some purpose other than the
	 * one below, but...), and that Wiretap and Wireshark
	 * currently support.
	 */
	{ 0,		WTAP_ENCAP_NULL },	/* null encapsulation */
	{ 1,		WTAP_ENCAP_ETHERNET },
	{ 6,		WTAP_ENCAP_TOKEN_RING },	/* IEEE 802 Networks - assume token ring */
	{ 7,		WTAP_ENCAP_ARCNET },
	{ 8,		WTAP_ENCAP_SLIP },
	{ 9,		WTAP_ENCAP_PPP },
#ifdef BIT_SWAPPED_MAC_ADDRS
	{ 10,		WTAP_ENCAP_FDDI_BITSWAPPED },
#else
	{ 10,		WTAP_ENCAP_FDDI },
#endif

	{ 32,		WTAP_ENCAP_REDBACK },

	/*
	 * 50 is DLT_PPP_SERIAL in NetBSD; it appears that DLT_PPP
	 * on BSD (at least according to standard tcpdump) has, as
	 * the first octet, an indication of whether the packet was
	 * transmitted or received (rather than having the standard
	 * PPP address value of 0xff), but that DLT_PPP_SERIAL puts
	 * a real live PPP header there, or perhaps a Cisco PPP header
	 * as per section 4.3.1 of RFC 1547 (implementations of this
	 * exist in various BSDs in "sys/net/if_spppsubr.c", and
	 * I think also exist either in standard Linux or in
	 * various Linux patches; the implementations show how to handle
	 * Cisco keepalive packets).
	 *
	 * However, I don't see any obvious place in FreeBSD "if_ppp.c"
	 * where anything other than the standard PPP header would be
	 * passed up.  I see some stuff that sets the first octet
	 * to 0 for incoming and 1 for outgoing packets before applying
	 * a BPF filter to see whether to drop packets whose protocol
	 * field has the 0x8000 bit set, i.e. network control protocols -
	 * those are handed up to userland - but that code puts the
	 * address field back before passing the packet up.
	 *
	 * I also don't see anything immediately obvious that munges
	 * the address field for sync PPP, either.
	 *
	 * Wireshark currently assumes that if the first octet of a
	 * PPP frame is 0xFF, it's the address field and is followed
	 * by a control field and a 2-byte protocol, otherwise the
	 * address and control fields are absent and the frame begins
	 * with a protocol field.  If we ever see a BSD/OS PPP
	 * capture, we'll have to handle it differently, and we may
	 * have to handle standard BSD captures differently if, in fact,
	 * they don't have 0xff 0x03 as the first two bytes - but, as per
	 * the two paragraphs preceding this, it's not clear that
	 * the address field *is* munged into an incoming/outgoing
	 * field when the packet is handed to the BPF device.
	 *
	 * For now, we just map DLT_PPP_SERIAL to WTAP_ENCAP_PPP, as
	 * we treat WTAP_ENCAP_PPP packets as if those beginning with
	 * 0xff have the standard RFC 1662 "PPP in HDLC-like Framing"
	 * 0xff 0x03 address/control header, and DLT_PPP_SERIAL frames
	 * appear to contain that unless they're Cisco frames (if we
	 * ever see a capture with them, we'd need to implement the
	 * RFC 1547 stuff, and the keepalive protocol stuff).
	 *
	 * We may have to distinguish between "PPP where if it doesn't
	 * begin with 0xff there's no HDLC encapsulation and the frame
	 * begins with the protocol field" (which is how we handle
	 * WTAP_ENCAP_PPP now) and "PPP where there's either HDLC
	 * encapsulation or Cisco PPP" (which is what DLT_PPP_SERIAL
	 * is) at some point.
	 *
	 * XXX - NetBSD has DLT_HDLC, which appears to be used for
	 * Cisco HDLC.  Ideally, they should use DLT_PPP_SERIAL
	 * only for real live HDLC-encapsulated PPP, not for Cisco
	 * HDLC.
	 */
	{ 50,		WTAP_ENCAP_PPP },

	/*
	 * Apparently used by the Axent Raptor firewall (now Symantec
	 * Enterprise Firewall).
	 * Thanks, Axent, for not reserving that type with tcpdump.org
	 * and not telling anybody about it.
	 */
	{ 99,		WTAP_ENCAP_SYMANTEC },

	/*
	 * These are the values that libpcap 0.5 and later use in
	 * capture file headers, in an attempt to work around the
	 * confusion decried above, and that Wiretap and Wireshark
	 * currently support.
	 */
	{ 100,		WTAP_ENCAP_ATM_RFC1483 },
	{ 101,		WTAP_ENCAP_RAW_IP },
#if 0
	/*
	 * More values used by libpcap 0.5 as DLT_ values and used by the
	 * current CVS version of libpcap in capture file headers.
	 * They are not yet handled in Wireshark.
	 * If we get a capture that contains them, we'll implement them.
	 */
	{ 102,		WTAP_ENCAP_SLIP_BSDOS },
	{ 103,		WTAP_ENCAP_PPP_BSDOS },
#endif

	/*
	 * These ones are handled in Wireshark, though.
	 */
	{ 104,		WTAP_ENCAP_CHDLC },	/* Cisco HDLC */
	{ 105,		WTAP_ENCAP_IEEE_802_11 }, /* IEEE 802.11 */
	{ 106,		WTAP_ENCAP_LINUX_ATM_CLIP },
	{ 107,		WTAP_ENCAP_FRELAY },	/* Frame Relay */
	{ 108,		WTAP_ENCAP_NULL },	/* OpenBSD loopback */
	{ 109,		WTAP_ENCAP_ENC },	/* OpenBSD IPSEC enc */
#if 0
	{ 110,		WTAP_ENCAP_LANE_802_3 },/* ATM LANE 802.3 */
	{ 111,		WTAP_ENCAP_HIPPI },	/* NetBSD HIPPI */
#endif
	{ 112,		WTAP_ENCAP_CHDLC },	/* NetBSD HDLC framing */

	/*
	 * Linux "cooked mode" captures, used by the current CVS version
	 * of libpcap
         * OR
         * it could be a packet in Cisco's ERSPAN encapsulation which uses
         * this number as well (why can't people stick to protocols when it
         * comes to allocating/using DLT types).
	 */
	{ 113,		WTAP_ENCAP_SLL },	/* Linux cooked capture */

	{ 114,		WTAP_ENCAP_LOCALTALK },	/* Localtalk */

	/*
	 * The tcpdump.org version of libpcap uses 117, rather than 17,
	 * for OpenBSD packet filter logging, so as to avoid conflicting
	 * with DLT_LANE8023 in SuSE 6.3 libpcap.
	 */
	{ 117,		WTAP_ENCAP_PFLOG },

	{ 118,		WTAP_ENCAP_CISCO_IOS },
	{ 119,		WTAP_ENCAP_PRISM_HEADER }, /* Prism monitor mode hdr */
	{ 121,		WTAP_ENCAP_HHDLC },	/* HiPath HDLC */
	{ 122,		WTAP_ENCAP_IP_OVER_FC },   /* RFC 2625 IP-over-FC */
	{ 123,		WTAP_ENCAP_ATM_PDUS },  /* SunATM */
	{ 127,		WTAP_ENCAP_IEEE_802_11_WLAN_RADIOTAP },  /* 802.11 plus radiotap WLAN header */
	{ 128,		WTAP_ENCAP_TZSP },	/* Tazmen Sniffer Protocol */
	{ 129,		WTAP_ENCAP_ARCNET_LINUX },
	{ 130,		WTAP_ENCAP_JUNIPER_MLPPP }, /* Juniper MLPPP on ML-, LS-, AS- PICs */
	{ 131,		WTAP_ENCAP_JUNIPER_MLFR }, /* Juniper MLFR (FRF.15) on ML-, LS-, AS- PICs */
	{ 133,		WTAP_ENCAP_JUNIPER_GGSN},
	/*
	 * Values 132-134, 136 not listed here are reserved for use
	 * in Juniper hardware.
	 */
	{ 135,		WTAP_ENCAP_JUNIPER_ATM2 }, /* various encapsulations captured on the ATM2 PIC */
	{ 137,		WTAP_ENCAP_JUNIPER_ATM1 }, /* various encapsulations captured on the ATM1 PIC */

	{ 138,		WTAP_ENCAP_APPLE_IP_OVER_IEEE1394 },
						/* Apple IP-over-IEEE 1394 */

	{ 139,		WTAP_ENCAP_MTP2_WITH_PHDR },
	{ 140,		WTAP_ENCAP_MTP2 },
	{ 141,		WTAP_ENCAP_MTP3 },
	{ 142,		WTAP_ENCAP_SCCP },
	{ 143,		WTAP_ENCAP_DOCSIS },
	{ 144,		WTAP_ENCAP_IRDA },	/* IrDA capture */

	/* Reserved for private use. */
	{ 147,		WTAP_ENCAP_USER0 },
	{ 148,		WTAP_ENCAP_USER1 },
	{ 149,		WTAP_ENCAP_USER2 },
	{ 150,		WTAP_ENCAP_USER3 },
	{ 151,		WTAP_ENCAP_USER4 },
	{ 152,		WTAP_ENCAP_USER5 },
	{ 153,		WTAP_ENCAP_USER6 },
	{ 154,		WTAP_ENCAP_USER7 },
	{ 155,		WTAP_ENCAP_USER8 },
	{ 156,		WTAP_ENCAP_USER9 },
	{ 157,		WTAP_ENCAP_USER10 },
	{ 158,		WTAP_ENCAP_USER11 },
	{ 159,		WTAP_ENCAP_USER12 },
	{ 160,		WTAP_ENCAP_USER13 },
	{ 161,		WTAP_ENCAP_USER14 },
	{ 162,		WTAP_ENCAP_USER15 },

	{ 163,		WTAP_ENCAP_IEEE_802_11_WLAN_AVS },  /* 802.11 plus AVS WLAN header */

	/*
	 * 164 is reserved for Juniper-private chassis-internal
	 * meta-information such as QoS profiles, etc..
	 */

	{ 165,		WTAP_ENCAP_BACNET_MS_TP },

	/*
	 * 166 is reserved for a PPP variant in which the first byte
	 * of the 0xff03 header, the 0xff, is replaced by a direction
	 * byte.  I don't know whether any captures look like that,
	 * but it is used for some Linux IP filtering (ipfilter?).
	 */

	/* Ethernet PPPoE frames captured on a service PIC */
	{ 167,		WTAP_ENCAP_JUNIPER_PPPOE },

        /*
	 * 168 is reserved for more Juniper private-chassis-
	 * internal meta-information.
	 */

	{ 169,		WTAP_ENCAP_GPRS_LLC },

	/*
	 * 170 and 171 are reserved for ITU-T G.7041/Y.1303 Generic
	 * Framing Procedure.
	 */

	/* Registered by Gcom, Inc. */
	{ 172,		WTAP_GCOM_TIE1 },
	{ 173,		WTAP_GCOM_SERIAL },

	{ 177,		WTAP_ENCAP_LINUX_LAPD },

	/* Ethernet frames prepended with meta-information */
	{ 178,		WTAP_ENCAP_JUNIPER_ETHER },
	/* PPP frames prepended with meta-information */
	{ 179,		WTAP_ENCAP_JUNIPER_PPP },
	/* Frame-Relay frames prepended with meta-information */
	{ 180,		WTAP_ENCAP_JUNIPER_FRELAY },
	/* C-HDLC frames prepended with meta-information */
	{ 181,		WTAP_ENCAP_JUNIPER_CHDLC },
	/* VOIP Frames prepended with meta-information */
	{ 183,		WTAP_ENCAP_JUNIPER_VP },
	/* raw USB packets */
	{ 186, 		WTAP_ENCAP_USB },
	/* Bluetooth HCI UART transport (part H:4) frames, like hcidump */
	{ 187, 		WTAP_ENCAP_BLUETOOTH_H4 },
	/* IEEE 802.16 MAC Common Part Sublayer */
	{ 188,		WTAP_ENCAP_IEEE802_16_MAC_CPS },
	/* USB packets with Linux-specified header */
	{ 189, 		WTAP_ENCAP_USB_LINUX },
	/* CAN 2.0b frame */
	{ 190, 		WTAP_ENCAP_CAN20B },
        /* Per-Packet Information header */
	{ 192,		WTAP_ENCAP_PPI },
	/* IEEE 802.15.4 Wireless PAN */
	{ 195,		WTAP_ENCAP_IEEE802_15_4 },
	/* SITA File Encapsulation */
	{ 196,		WTAP_ENCAP_SITA },
	/* Endace Record File Encapsulation */
	{ 197,		WTAP_ENCAP_ERF },
	{ 199,		WTAP_ENCAP_IPMB },
	/* Bluetooth HCI UART transport (part H:4) frames, like hcidump */
	{ 201, 		WTAP_ENCAP_BLUETOOTH_H4_WITH_PHDR },
	/* IPMB/I2C */
	{ 209,		WTAP_ENCAP_I2C },
	/* FlexRay frame */
	{ 210, 		WTAP_ENCAP_FLEXRAY },
	/* MOST frame */
	{ 211, 		WTAP_ENCAP_MOST },
	/* LIN frame */
	{ 212, 		WTAP_ENCAP_LIN },
	/* X2E Xoraya serial frame */
	{ 213, 		WTAP_ENCAP_X2E_SERIAL },
	/* X2E Xoraya frame */
	{ 214, 		WTAP_ENCAP_X2E_XORAYA },

	/*
	 * To repeat:
	 *
	 * If you need a new encapsulation type for libpcap files, do
	 * *N*O*T* use *ANY* of the values listed here!  I.e., do *NOT*
	 * add a new encapsulation type by changing an existing entry;
	 * leave the existing entries alone.
	 *
	 * Instead, send mail to tcpdump-workers@lists.tcpdump.org, asking
	 * for a new DLT_ value, and specifying the purpose of the new value.
	 * When you get the new DLT_ value, use that numerical value in
	 * the "dlt_value" field of "pcap_to_wtap_map[]".
	 */

	/*
	 * The following are entries for libpcap type values that have
	 * different meanings on different OSes.
	 *
	 * We put these *after* the entries for the platform-independent
	 * libpcap type values for those Wiretap encapsulation types, so
	 * that Wireshark chooses the platform-independent libpcap type
	 * value for those encapsulatioin types, not the platform-dependent
	 * one.
	 */

	/*
	 * 11 is DLT_ATM_RFC1483 on most platforms; the only libpcaps I've
	 * seen that define anything other than DLT_ATM_RFC1483 as 11 are
	 * the BSD/OS one, which defines DLT_FR as 11, and libpcap 0.5,
	 * which define it as 100, mapping the kernel's value to 100, in
	 * an attempt to hide the different values used on different
	 * platforms.
	 *
	 * If this is a platform where DLT_FR is defined as 11, we
	 * don't handle 11 at all; otherwise, we handle it as
	 * DLT_ATM_RFC1483 (this means we'd misinterpret Frame Relay
	 * captures from BSD/OS if running on platforms other than BSD/OS,
	 * but
	 *
	 *	1) we don't yet support DLT_FR
	 *
	 * and
	 *
	 *	2) nothing short of a heuristic would let us interpret
	 *	   them correctly).
	 */
#if defined(DLT_FR) && (DLT_FR == 11)
	{ 11,		WTAP_ENCAP_FRELAY },
#else
	{ 11,		WTAP_ENCAP_ATM_RFC1483 },
#endif

	/*
	 * 12 is DLT_RAW on most platforms, but it's DLT_C_HDLC on
	 * BSD/OS, and DLT_LOOP on OpenBSD.
	 *
	 * We don't yet handle DLT_C_HDLC, but we can handle DLT_LOOP
	 * (it's just like DLT_NULL, only with the AF_ value in network
	 * rather than host byte order - Wireshark figures out the
	 * byte order from the data, so we don't care what byte order
	 * it's in), so if DLT_LOOP is defined as 12, interpret 12
	 * as WTAP_ENCAP_NULL, otherwise, unless DLT_C_HDLC is defined
	 * as 12, interpret it as WTAP_ENCAP_RAW_IP.
	 */
#if defined(DLT_LOOP) && (DLT_LOOP == 12)
	{ 12,		WTAP_ENCAP_NULL },
#elif defined(DLT_C_HDLC) && (DLT_C_HDLC == 12)
	/*
	 * Put entry for Cisco HDLC here.
	 * XXX - is this just WTAP_ENCAP_CHDLC, i.e. does the frame
	 * start with a 4-byte Cisco HDLC header?
	 */
#else
	{ 12,		WTAP_ENCAP_RAW_IP },
#endif

	/*
	 * 13 is DLT_SLIP_BSDOS on FreeBSD and NetBSD, but those OSes
	 * don't actually generate it.  I infer that BSD/OS translates
	 * DLT_SLIP from the kernel BPF code to DLT_SLIP_BSDOS in
	 * libpcap, as the BSD/OS link-layer header is different;
	 * however, in BSD/OS, DLT_SLIP_BSDOS is 15.
	 *
	 * From this, I infer that there's no point in handling 13
	 * as DLT_SLIP_BSDOS.
	 *
	 * 13 is DLT_ATM_RFC1483 on BSD/OS.
	 *
	 * 13 is DLT_ENC in OpenBSD, which is, I suspect, some kind
	 * of decrypted IPSEC traffic.
	 */
#if defined(DLT_ATM_RFC1483) && (DLT_ATM_RFC1483 == 13)
	{ 13,		WTAP_ENCAP_ATM_RFC1483 },
#elif defined(DLT_ENC) && (DLT_ENC == 13)
	{ 13,		WTAP_ENCAP_ENC },
#endif

	/*
	 * 14 is DLT_PPP_BSDOS on FreeBSD and NetBSD, but those OSes
	 * don't actually generate it.  I infer that BSD/OS translates
	 * DLT_PPP from the kernel BPF code to DLT_PPP_BSDOS in
	 * libpcap, as the BSD/OS link-layer header is different;
	 * however, in BSD/OS, DLT_PPP_BSDOS is 16.
	 *
	 * From this, I infer that there's no point in handling 14
	 * as DLT_PPP_BSDOS.
	 *
	 * 14 is DLT_RAW on BSD/OS and OpenBSD.
	 */
	{ 14,		WTAP_ENCAP_RAW_IP },

	/*
	 * 15 is:
	 *
	 *	DLT_SLIP_BSDOS on BSD/OS;
	 *
	 *	DLT_HIPPI on NetBSD;
	 *
	 *	DLT_LANE8023 with Alexey Kuznetzov's patches for
	 *	Linux libpcap;
	 *
	 *	DLT_I4L_RAWIP with the ISDN4Linux patches for libpcap
	 *	(and on SuSE 6.3);
	 *
	 * but we don't currently handle any of those.
	 */

	/*
	 * 16 is:
	 *
	 *	DLT_PPP_BSDOS on BSD/OS;
	 *
	 *	DLT_HDLC on NetBSD (Cisco HDLC);
	 *
	 *	DLT_CIP with Alexey Kuznetzov's patches for
	 *	Linux libpcap - this is WTAP_ENCAP_LINUX_ATM_CLIP;
	 *
	 *	DLT_I4L_IP with the ISDN4Linux patches for libpcap
	 *	(and on SuSE 6.3).
	 */
#if defined(DLT_CIP) && (DLT_CIP == 16)
	{ 16,		WTAP_ENCAP_LINUX_ATM_CLIP },
#endif
#if defined(DLT_HDLC) && (DLT_HDLC == 16)
	{ 16,		WTAP_ENCAP_CHDLC },
#endif

	/*
	 * 17 is DLT_LANE8023 in SuSE 6.3 libpcap; we don't currently
	 * handle it.
	 * It is also used as the PF (Packet Filter) logging format beginning
	 * with OpenBSD 3.0; we use 17 for PF logs unless DLT_LANE8023 is
	 * defined with the value 17.
	 */
#if !defined(DLT_LANE8023) || (DLT_LANE8023 != 17)
	{ 17,		WTAP_ENCAP_OLD_PFLOG },
#endif

	/*
	 * 18 is DLT_CIP in SuSE 6.3 libpcap; if it's the same as the
	 * DLT_CIP of 16 that the Alexey Kuznetzov patches for
	 * libpcap/tcpdump define, it's WTAP_ENCAP_LINUX_ATM_CLIP.
	 * I've not found any libpcap that uses it for any other purpose -
	 * hopefully nobody will do so in the future.
	 */
	{ 18,		WTAP_ENCAP_LINUX_ATM_CLIP },

	/*
	 * 19 is DLT_ATM_CLIP in the libpcap/tcpdump patches in the
	 * recent versions I've seen of the Linux ATM distribution;
	 * I've not yet found any libpcap that uses it for any other
	 * purpose - hopefully nobody will do so in the future.
	 */
	{ 19,		WTAP_ENCAP_LINUX_ATM_CLIP },

	/*
	 * nettl (HP-UX) mappings to standard DLT values
         */

	{ 1,		WTAP_ENCAP_NETTL_ETHERNET },
	{ 6,		WTAP_ENCAP_NETTL_TOKEN_RING },
	{ 10,		WTAP_ENCAP_NETTL_FDDI },
	{ 70,		WTAP_ENCAP_RAW_IP },
	{ 101,		WTAP_ENCAP_NETTL_RAW_IP },

	/*
	 * To repeat:
	 *
	 * If you need a new encapsulation type for libpcap files, do
	 * *N*O*T* use *ANY* of the values listed here!  I.e., do *NOT*
	 * add a new encapsulation type by changing an existing entry;
	 * leave the existing entries alone.
	 *
	 * Instead, send mail to tcpdump-workers@lists.tcpdump.org, asking
	 * for a new DLT_ value, and specifying the purpose of the new value.
	 * When you get the new DLT_ value, use that numerical value in
	 * the "dlt_value" field of "pcap_to_wtap_map[]".
	 */

};
#define NUM_PCAP_ENCAPS (sizeof pcap_to_wtap_map / sizeof pcap_to_wtap_map[0])

int wtap_pcap_encap_to_wtap_encap(int encap)
{
	unsigned int i;

	for (i = 0; i < NUM_PCAP_ENCAPS; i++) {
		if (pcap_to_wtap_map[i].dlt_value == encap)
			return pcap_to_wtap_map[i].wtap_encap_value;
	}
	return WTAP_ENCAP_UNKNOWN;
}

int wtap_wtap_encap_to_pcap_encap(int encap)
{
	unsigned int i;

	switch (encap) {

	case WTAP_ENCAP_FDDI:
	case WTAP_ENCAP_FDDI_BITSWAPPED:
	case WTAP_ENCAP_NETTL_FDDI:
		/*
		 * Special-case WTAP_ENCAP_FDDI and
		 * WTAP_ENCAP_FDDI_BITSWAPPED; both of them get mapped
		 * to DLT_FDDI (even though that may mean that the bit
		 * order in the FDDI MAC addresses is wrong; so it goes
		 * - libpcap format doesn't record the byte order,
		 * so that's not fixable).
		 */
		return 10;	/* that's DLT_FDDI */

	case WTAP_ENCAP_PPP_WITH_PHDR:
		/*
		 * Also special-case PPP with direction bits; map it to
		 * PPP, even though that means that the direction of the
		 * packet is lost.
		 */
		return 9;

	case WTAP_ENCAP_FRELAY_WITH_PHDR:
		/*
		 * Do the same with Frame Relay.
		 */
		return 107;

	case WTAP_ENCAP_IEEE_802_11_WITH_RADIO:
		/*
		 * Map this to DLT_IEEE802_11, for now, even though
		 * that means the radio information will be lost.
		 * Once tcpdump support for the BSD radiotap header
		 * is sufficiently widespread, we should probably
		 * use that, instead - although we should probably
		 * ultimately just have WTAP_ENCAP_IEEE_802_11
		 * as the only Wiretap encapsulation for 802.11,
		 * and have the pseudo-header include a radiotap-style
		 * list of attributes.  If we do that, though, we
		 * should probably bypass the regular Wiretap code
		 * when writing out packets during a capture, and just
		 * do the equivalent of a libpcap write (unfortunately,
		 * libpcap doesn't have an "open dump by file descriptor"
		 * function, so we can't just use "pcap_dump()"), so
		 * that we don't spend cycles mapping from libpcap to
		 * Wiretap and then back to libpcap.  (There are other
		 * reasons to do that, e.g. to handle AIX libpcap better.)
		 */
		return 105;
	}

	for (i = 0; i < NUM_PCAP_ENCAPS; i++) {
		if (pcap_to_wtap_map[i].wtap_encap_value == encap)
			return pcap_to_wtap_map[i].dlt_value;
	}
	return -1;
}