[libpcap] / savefile.c

/*
 * Copyright (c) 1993, 1994, 1995, 1996, 1997
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * savefile.c - supports offline use of tcpdump
 *      Extraction/creation by Jeffrey Mogul, DECWRL
 *      Modified by Steve McCanne, LBL.
 *
 * Used to save the received packet headers, after filtering, to
 * a file, and then read them later.
 * The first record in the file contains saved values for the machine
 * dependent values so we can print the dump file on any architecture.
 */

#ifndef lint
static const char rcsid[] =
    "@(#) $Header: /tcpdump/master/libpcap/savefile.c,v 1.67 2002-10-09 19:02:56 guy Exp $ (LBL)";
#endif

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

#include <errno.h>
#include <memory.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "pcap-int.h"

#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif

#define TCPDUMP_MAGIC 0xa1b2c3d4
#define PATCHED_TCPDUMP_MAGIC 0xa1b2cd34

/*
 * We use the "receiver-makes-right" approach to byte order,
 * because time is at a premium when we are writing the file.
 * In other words, the pcap_file_header and pcap_pkthdr,
 * records are written in host byte order.
 * Note that the packets are always written in network byte order.
 *
 * ntoh[ls] aren't sufficient because we might need to swap on a big-endian
 * machine (if the file was written in little-end order).
 */
#define SWAPLONG(y) \
((((y)&0xff)<<24) | (((y)&0xff00)<<8) | (((y)&0xff0000)>>8) | (((y)>>24)&0xff))
#define SWAPSHORT(y) \
        ( (((y)&0xff)<<8) | ((u_short)((y)&0xff00)>>8) )

#define SFERR_TRUNC             1
#define SFERR_BADVERSION        2
#define SFERR_BADF              3
#define SFERR_EOF               4 /* not really an error, just a status */

/*
 * We don't write DLT_* values to the capture file header, because
 * they're not the same on all platforms.
 *
 * Unfortunately, the various flavors of BSD have not always used the same
 * numerical values for the same data types, and various patches to
 * libpcap for non-BSD OSes have added their own DLT_* codes for link
 * layer encapsulation types seen on those OSes, and those codes have had,
 * in some cases, values that were also used, on other platforms, for other
 * link layer encapsulation types.
 *
 * This means that capture files of a type whose numerical DLT_* code
 * means different things on different BSDs, or with different versions
 * of libpcap, can't always be read on systems other than those like
 * the one running on the machine on which the capture was made.
 *
 * Instead, we define here a set of LINKTYPE_* codes, and map DLT_* codes
 * to LINKTYPE_* codes when writing a savefile header, and map LINKTYPE_*
 * codes to DLT_* codes when reading a savefile header.
 *
 * For those DLT_* codes that have, as far as we know, the same values on
 * all platforms (DLT_NULL through DLT_FDDI), we define LINKTYPE_xxx as
 * DLT_xxx; that way, captures of those types can still be read by
 * versions of libpcap that map LINKTYPE_* values to DLT_* values, and
 * captures of those types written by versions of libpcap that map DLT_
 * values to LINKTYPE_ values can still be read by older versions
 * of libpcap.
 *
 * The other LINKTYPE_* codes are given values starting at 100, in the
 * hopes that no DLT_* code will be given one of those values.
 *
 * In order to ensure that a given LINKTYPE_* code's value will refer to
 * the same encapsulation type on all platforms, you should not allocate
 * a new LINKTYPE_* value without consulting "tcpdump-workers@tcpdump.org".
 * The tcpdump developers will allocate a value for you, and will not
 * subsequently allocate it to anybody else; that value will be added to
 * the "pcap.h" in the tcpdump.org CVS repository, so that a future
 * libpcap release will include it.
 *
 * You should, if possible, also contribute patches to libpcap and tcpdump
 * to handle the new encapsulation type, so that they can also be checked
 * into the tcpdump.org CVS repository and so that they will appear in
 * future libpcap and tcpdump releases.
 */
#define LINKTYPE_NULL           DLT_NULL
#define LINKTYPE_ETHERNET       DLT_EN10MB      /* also for 100Mb and up */
#define LINKTYPE_EXP_ETHERNET   DLT_EN3MB       /* 3Mb experimental Ethernet */
#define LINKTYPE_AX25           DLT_AX25
#define LINKTYPE_PRONET         DLT_PRONET
#define LINKTYPE_CHAOS          DLT_CHAOS
#define LINKTYPE_TOKEN_RING     DLT_IEEE802     /* DLT_IEEE802 is used for Token Ring */
#define LINKTYPE_ARCNET         DLT_ARCNET
#define LINKTYPE_SLIP           DLT_SLIP
#define LINKTYPE_PPP            DLT_PPP
#define LINKTYPE_FDDI           DLT_FDDI

/*
 * LINKTYPE_PPP is for use when there might, or might not, be an RFC 1662
 * PPP in HDLC-like framing header (with 0xff 0x03 before the PPP protocol
 * field) at the beginning of the packet.
 *
 * This is for use when there is always such a header; the address field
 * might be 0xff, for regular PPP, or it might be an address field for Cisco
 * point-to-point with HDLC framing as per section 4.3.1 of RFC 1547 ("Cisco
 * HDLC").  This is, for example, what you get with NetBSD's DLT_PPP_SERIAL.
 *
 * We give it the same value as NetBSD's DLT_PPP_SERIAL, in the hopes that
 * nobody else will choose a DLT_ value of 50, and so that DLT_PPP_SERIAL
 * captures will be written out with a link type that NetBSD's tcpdump
 * can read.
 */
#define LINKTYPE_PPP_HDLC       50              /* PPP in HDLC-like framing */

#define LINKTYPE_PPP_ETHER      51              /* NetBSD PPP-over-Ethernet */

#define LINKTYPE_ATM_RFC1483    100             /* LLC/SNAP-encapsulated ATM */
#define LINKTYPE_RAW            101             /* raw IP */
#define LINKTYPE_SLIP_BSDOS     102             /* BSD/OS SLIP BPF header */
#define LINKTYPE_PPP_BSDOS      103             /* BSD/OS PPP BPF header */
#define LINKTYPE_C_HDLC         104             /* Cisco HDLC */
#define LINKTYPE_IEEE802_11     105             /* IEEE 802.11 (wireless) */
#define LINKTYPE_ATM_CLIP       106             /* Linux Classical IP over ATM */
#define LINKTYPE_FRELAY         107             /* Frame Relay */
#define LINKTYPE_LOOP           108             /* OpenBSD loopback */

#define LINKTYPE_LINUX_SLL      113             /* Linux cooked socket capture */
#define LINKTYPE_LTALK          114             /* Apple LocalTalk hardware */
#define LINKTYPE_ECONET         115             /* Acorn Econet */

#define LINKTYPE_CISCO_IOS      118             /* For Cisco-internal use */
#define LINKTYPE_PRISM_HEADER   119             /* 802.11+Prism II monitor mode */
#define LINKTYPE_AIRONET_HEADER 120             /* FreeBSD Aironet driver stuff */
#define LINKTYPE_SUNATM         123             /* Solaris+SunATM */

/*
 * These types are reserved for future use.
 */
#define LINKTYPE_ENC            109             /* OpenBSD IPSEC enc */
#define LINKTYPE_LANE8023       110             /* ATM LANE + 802.3 */
#define LINKTYPE_HIPPI          111             /* NetBSD HIPPI */
#define LINKTYPE_HDLC           112             /* NetBSD HDLC framing */
#define LINKTYPE_IPFILTER       116             /* IP Filter capture files */
#define LINKTYPE_PFLOG          117             /* OpenBSD DLT_PFLOG */
#define LINKTYPE_HHDLC          121             /* Siemens HiPath HDLC */
#define LINKTYPE_IP_OVER_FC     122             /* RFC 2625 IP-over-Fibre Channel */
#define LINKTYPE_RIO            123             /* RapidIO */
#define LINKTYPE_PCI_EXP        124             /* PCI Express */
#define LINKTYPE_AURORA         125             /* Xilinx Aurora link layer */

static struct linktype_map {
        int     dlt;
        int     linktype;
} map[] = {
        /*
         * These DLT_* codes have LINKTYPE_* codes with values identical
         * to the values of the corresponding DLT_* code.
         */
        { DLT_NULL,             LINKTYPE_NULL },
        { DLT_EN10MB,           LINKTYPE_ETHERNET },
        { DLT_EN3MB,            LINKTYPE_EXP_ETHERNET },
        { DLT_AX25,             LINKTYPE_AX25 },
        { DLT_PRONET,           LINKTYPE_PRONET },
        { DLT_CHAOS,            LINKTYPE_CHAOS },
        { DLT_IEEE802,          LINKTYPE_TOKEN_RING },
        { DLT_ARCNET,           LINKTYPE_ARCNET },
        { DLT_SLIP,             LINKTYPE_SLIP },
        { DLT_PPP,              LINKTYPE_PPP },
        { DLT_FDDI,             LINKTYPE_FDDI },

        /*
         * These DLT_* codes have different values on different
         * platforms; we map them to LINKTYPE_* codes that
         * have values that should never be equal to any DLT_*
         * code.
         */
#ifdef DLT_FR
        /* BSD/OS Frame Relay */
        { DLT_FR,               LINKTYPE_FRELAY },
#endif
        { DLT_ATM_RFC1483,      LINKTYPE_ATM_RFC1483 },
        { DLT_RAW,              LINKTYPE_RAW },
        { DLT_SLIP_BSDOS,       LINKTYPE_SLIP_BSDOS },
        { DLT_PPP_BSDOS,        LINKTYPE_PPP_BSDOS },

        /* BSD/OS Cisco HDLC */
        { DLT_C_HDLC,           LINKTYPE_C_HDLC },

        /*
         * These DLT_* codes are not on all platforms, but, so far,
         * there don't appear to be any platforms that define
         * other codes with those values; we map them to
         * different LINKTYPE_* values anyway, just in case.
         */

        /* Linux ATM Classical IP */
        { DLT_ATM_CLIP,         LINKTYPE_ATM_CLIP },

        /* NetBSD sync/async serial PPP (or Cisco HDLC) */
        { DLT_PPP_SERIAL,       LINKTYPE_PPP_HDLC },

        /* NetBSD PPP over Ethernet */
        { DLT_PPP_ETHER,        LINKTYPE_PPP_ETHER },

        /* IEEE 802.11 wireless */
        { DLT_IEEE802_11,       LINKTYPE_IEEE802_11 },

        /* Frame Relay */
        { DLT_FRELAY,           LINKTYPE_FRELAY },

        /* OpenBSD loopback */
        { DLT_LOOP,             LINKTYPE_LOOP },

        /* Linux cooked socket capture */
        { DLT_LINUX_SLL,        LINKTYPE_LINUX_SLL },

        /* Apple LocalTalk hardware */
        { DLT_LTALK,            LINKTYPE_LTALK },

        /* Acorn Econet */
        { DLT_ECONET,           LINKTYPE_ECONET },

        /* For Cisco-internal use */
        { DLT_CISCO_IOS,        LINKTYPE_CISCO_IOS },

        /* Prism II monitor-mode header plus 802.11 header */
        { DLT_PRISM_HEADER,     LINKTYPE_PRISM_HEADER },

        /* FreeBSD Aironet driver stuff */
        { DLT_AIRONET_HEADER,   LINKTYPE_AIRONET_HEADER },

        /* Siemens HiPath HDLC */
        { DLT_HHDLC,            LINKTYPE_HHDLC },

        /* RFC 2625 IP-over-Fibre Channel */
        { DLT_IP_OVER_FC,       LINKTYPE_IP_OVER_FC },

        /* Solaris+SunATM */
        { DLT_SUNATM,           LINKTYPE_SUNATM },

        /* RapidIO */
        { DLT_RIO,              LINKTYPE_RIO },

        /* PCI Express */
        { DLT_PCI_EXP,          LINKTYPE_PCI_EXP },

        /* Xilinx Aurora link layer */
        { DLT_AURORA,           LINKTYPE_AURORA },

        /*
         * Any platform that defines additional DLT_* codes should:
         *
         *      request a LINKTYPE_* code and value from tcpdump.org,
         *      as per the above;
         *
         *      add, in their version of libpcap, an entry to map
         *      those DLT_* codes to the corresponding LINKTYPE_*
         *      code;
         *
         *      redefine, in their "net/bpf.h", any DLT_* values
         *      that collide with the values used by their additional
         *      DLT_* codes, to remove those collisions (but without
         *      making them collide with any of the LINKTYPE_*
         *      values equal to 50 or above; they should also avoid
         *      defining DLT_* values that collide with those
         *      LINKTYPE_* values, either).
         */
        { -1,                   -1 }
};

static int
dlt_to_linktype(int dlt)
{
        int i;

        for (i = 0; map[i].dlt != -1; i++) {
                if (map[i].dlt == dlt)
                        return (map[i].linktype);
        }

        /*
         * If we don't have a mapping for this DLT_ code, return an
         * error; that means that the table above needs to have an
         * entry added.
         */
        return (-1);
}

static int
linktype_to_dlt(int linktype)
{
        int i;

        for (i = 0; map[i].linktype != -1; i++) {
                if (map[i].linktype == linktype)
                        return (map[i].dlt);
        }

        /*
         * If we don't have an entry for this link type, return
         * the link type value; it may be a DLT_ value from an
         * older version of libpcap.
         */
        return linktype;
}

static int
sf_write_header(FILE *fp, int linktype, int thiszone, int snaplen)
{
        struct pcap_file_header hdr;

        hdr.magic = TCPDUMP_MAGIC;
        hdr.version_major = PCAP_VERSION_MAJOR;
        hdr.version_minor = PCAP_VERSION_MINOR;

        hdr.thiszone = thiszone;
        hdr.snaplen = snaplen;
        hdr.sigfigs = 0;
        hdr.linktype = linktype;

        if (fwrite((char *)&hdr, sizeof(hdr), 1, fp) != 1)
                return (-1);

        return (0);
}

static void
swap_hdr(struct pcap_file_header *hp)
{
        hp->version_major = SWAPSHORT(hp->version_major);
        hp->version_minor = SWAPSHORT(hp->version_minor);
        hp->thiszone = SWAPLONG(hp->thiszone);
        hp->sigfigs = SWAPLONG(hp->sigfigs);
        hp->snaplen = SWAPLONG(hp->snaplen);
        hp->linktype = SWAPLONG(hp->linktype);
}

pcap_t *
pcap_open_offline(const char *fname, char *errbuf)
{
        register pcap_t *p;
        register FILE *fp;
        struct pcap_file_header hdr;
        bpf_u_int32 magic;
        int linklen;

        p = (pcap_t *)malloc(sizeof(*p));
        if (p == NULL) {
                strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
                return (NULL);
        }

        memset((char *)p, 0, sizeof(*p));
        /*
         * Set this field so we don't close stdin in pcap_close!
         */
#ifndef WIN32
        p->fd = -1;
#else
        p->adapter = NULL;
#endif

        if (fname[0] == '-' && fname[1] == '\0')
                fp = stdin;
        else {
#ifndef WIN32
                fp = fopen(fname, "r");
#else
                fp = fopen(fname, "rb");
#endif
                if (fp == NULL) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", fname,
                            pcap_strerror(errno));
                        goto bad;
                }
        }
        if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) {
                snprintf(errbuf, PCAP_ERRBUF_SIZE, "fread: %s",
                    pcap_strerror(errno));
                goto bad;
        }
        magic = hdr.magic;
        if (magic != TCPDUMP_MAGIC && magic != PATCHED_TCPDUMP_MAGIC) {
                magic = SWAPLONG(magic);
                if (magic != TCPDUMP_MAGIC && magic != PATCHED_TCPDUMP_MAGIC) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE,
                            "bad dump file format");
                        goto bad;
                }
                p->sf.swapped = 1;
                swap_hdr(&hdr);
        }
        if (magic == PATCHED_TCPDUMP_MAGIC) {
                /*
                 * XXX - the patch that's in some versions of libpcap
                 * changes the packet header but not the magic number;
                 * we'd have to use some hacks^H^H^H^H^Hheuristics to
                 * detect that.
                 */
                p->sf.hdrsize = sizeof(struct pcap_sf_patched_pkthdr);
        } else
                p->sf.hdrsize = sizeof(struct pcap_sf_pkthdr);
        if (hdr.version_major < PCAP_VERSION_MAJOR) {
                snprintf(errbuf, PCAP_ERRBUF_SIZE, "archaic file format");
                goto bad;
        }
        p->tzoff = hdr.thiszone;
        p->snapshot = hdr.snaplen;
        p->linktype = linktype_to_dlt(hdr.linktype);
        p->sf.rfile = fp;
#ifndef WIN32
        p->bufsize = hdr.snaplen;
#else
        /* Allocate the space for pcap_pkthdr as well. It will be used by pcap_read_ex */
        p->bufsize = hdr.snaplen+sizeof(struct pcap_pkthdr);
#endif

        /* Align link header as required for proper data alignment */
        /* XXX should handle all types */
        switch (p->linktype) {

        case DLT_EN10MB:
                linklen = 14;
                break;

        case DLT_FDDI:
                linklen = 13 + 8;       /* fddi_header + llc */
                break;

        case DLT_NULL:
        default:
                linklen = 0;
                break;
        }

        if (p->bufsize < 0)
                p->bufsize = BPF_MAXBUFSIZE;
        p->sf.base = (u_char *)malloc(p->bufsize + BPF_ALIGNMENT);
        if (p->sf.base == NULL) {
                strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
                goto bad;
        }
        p->buffer = p->sf.base + BPF_ALIGNMENT - (linklen % BPF_ALIGNMENT);
        p->sf.version_major = hdr.version_major;
        p->sf.version_minor = hdr.version_minor;
#ifdef PCAP_FDDIPAD
        /* XXX padding only needed for kernel fcode */
        pcap_fddipad = 0;
#endif

        return (p);
 bad:
        free(p);
        return (NULL);
}

/*
 * Read sf_readfile and return the next packet.  Return the header in hdr
 * and the contents in buf.  Return 0 on success, SFERR_EOF if there were
 * no more packets, and SFERR_TRUNC if a partial packet was encountered.
 */
#ifdef WIN32
int
#else
static int
#endif
sf_next_packet(pcap_t *p, struct pcap_pkthdr *hdr, u_char *buf, int buflen)
{
        struct pcap_sf_patched_pkthdr sf_hdr;
        FILE *fp = p->sf.rfile;

        /*
         * Read the packet header; the structure we use as a buffer
         * is the longer structure for files generated by the patched
         * libpcap, but if the file has the magic number for an
         * unpatched libpcap we only read as many bytes as the regular
         * header has.
         */
        if (fread(&sf_hdr, p->sf.hdrsize, 1, fp) != 1) {
                /* probably an EOF, though could be a truncated packet */
                return (1);
        }

        if (p->sf.swapped) {
                /* these were written in opposite byte order */
                hdr->caplen = SWAPLONG(sf_hdr.caplen);
                hdr->len = SWAPLONG(sf_hdr.len);
                hdr->ts.tv_sec = SWAPLONG(sf_hdr.ts.tv_sec);
                hdr->ts.tv_usec = SWAPLONG(sf_hdr.ts.tv_usec);
        } else {
                hdr->caplen = sf_hdr.caplen;
                hdr->len = sf_hdr.len;
                hdr->ts.tv_sec = sf_hdr.ts.tv_sec;
                hdr->ts.tv_usec = sf_hdr.ts.tv_usec;
        }
        /*
         * We interchanged the caplen and len fields at version 2.3,
         * in order to match the bpf header layout.  But unfortunately
         * some files were written with version 2.3 in their headers
         * but without the interchanged fields.
         */
        if (p->sf.version_minor < 3 ||
            (p->sf.version_minor == 3 && hdr->caplen > hdr->len)) {
                int t = hdr->caplen;
                hdr->caplen = hdr->len;
                hdr->len = t;
        }

        if (hdr->caplen > buflen) {
                /*
                 * This can happen due to Solaris 2.3 systems tripping
                 * over the BUFMOD problem and not setting the snapshot
                 * correctly in the savefile header.  If the caplen isn't
                 * grossly wrong, try to salvage.
                 */
                static u_char *tp = NULL;
                static int tsize = 0;

                if (hdr->caplen > 65535) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "bogus savefile header");
                        return (-1);
                }

                if (tsize < hdr->caplen) {
                        tsize = ((hdr->caplen + 1023) / 1024) * 1024;
                        if (tp != NULL)
                                free((u_char *)tp);
                        tp = (u_char *)malloc(tsize);
                        if (tp == NULL) {
                                tsize = 0;
                                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                                    "BUFMOD hack malloc");
                                return (-1);
                        }
                }
                if (fread((char *)tp, hdr->caplen, 1, fp) != 1) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "truncated dump file");
                        return (-1);
                }
                /*
                 * We can only keep up to buflen bytes.  Since caplen > buflen
                 * is exactly how we got here, we know we can only keep the
                 * first buflen bytes and must drop the remainder.  Adjust
                 * caplen accordingly, so we don't get confused later as
                 * to how many bytes we have to play with.
                 */
                hdr->caplen = buflen;
                memcpy((char *)buf, (char *)tp, buflen);

        } else {
                /* read the packet itself */

                if (fread((char *)buf, hdr->caplen, 1, fp) != 1) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                            "truncated dump file");
                        return (-1);
                }
        }
        return (0);
}

/*
 * Print out packets stored in the file initialized by sf_read_init().
 * If cnt > 0, return after 'cnt' packets, otherwise continue until eof.
 */
int
pcap_offline_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
        struct bpf_insn *fcode = p->fcode.bf_insns;
        int status = 0;
        int n = 0;

        while (status == 0) {
                struct pcap_pkthdr h;

                status = sf_next_packet(p, &h, p->buffer, p->bufsize);
                if (status) {
                        if (status == 1)
                                return (0);
                        return (status);
                }

                if (fcode == NULL ||
                    bpf_filter(fcode, p->buffer, h.len, h.caplen)) {
                        (*callback)(user, &h, p->buffer);
                        if (++n >= cnt && cnt > 0)
                                break;
                }
        }
        /*XXX this breaks semantics tcpslice expects */
        return (n);
}

/*
 * Output a packet to the initialized dump file.
 */
void
pcap_dump(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
{
        register FILE *f;
        struct pcap_sf_pkthdr sf_hdr;

        f = (FILE *)user;
        sf_hdr.ts.tv_sec  = h->ts.tv_sec;
        sf_hdr.ts.tv_usec = h->ts.tv_usec;
        sf_hdr.caplen     = h->caplen;
        sf_hdr.len        = h->len;
        /* XXX we should check the return status */
        (void)fwrite(&sf_hdr, sizeof(sf_hdr), 1, f);
        (void)fwrite((char *)sp, h->caplen, 1, f);
}

/*
 * Initialize so that sf_write() will output to the file named 'fname'.
 */
pcap_dumper_t *
pcap_dump_open(pcap_t *p, const char *fname)
{
        FILE *f;
        int linktype;

        linktype = dlt_to_linktype(p->linktype);
        if (linktype == -1) {
                snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
                    "%s: link-layer type %d isn't supported in savefiles",
                    fname, linktype);
                return (NULL);
        }

        if (fname[0] == '-' && fname[1] == '\0') {
                f = stdout;
#ifdef WIN32
                _setmode(_fileno(f), _O_BINARY);
#endif
        } else {
#ifndef WIN32
                f = fopen(fname, "w");
#else
                f = fopen(fname, "wb");
                setbuf(f, NULL);        /* XXX - why? */
#endif
                if (f == NULL) {
                        snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "%s: %s",
                            fname, pcap_strerror(errno));
                        return (NULL);
                }
        }
        (void)sf_write_header(f, linktype, p->tzoff, p->snapshot);
        return ((pcap_dumper_t *)f);
}

void
pcap_dump_close(pcap_dumper_t *p)
{

#ifdef notyet
        if (ferror((FILE *)p))
                return-an-error;
        /* XXX should check return from fclose() too */
#endif
        (void)fclose((FILE *)p);
}