source: lib/format_pcapfile.c @ 5cdb37d

/*
 *
 * Copyright (c) 2007-2016 The University of Waikato, Hamilton, New Zealand.
 * All rights reserved.
 *
 * This file is part of libtrace.
 *
 * This code has been developed by the University of Waikato WAND
 * research group. For further information please see http://www.wand.net.nz/
 *
 * libtrace is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * libtrace 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 */
#include "common.h"
#include "config.h"
#include "libtrace.h"
#include "libtrace_int.h"
#include "format_helper.h"

#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>

/* This format module implements our own, more efficient, version of the PCAP
 * file format. This should always be used in preference to the "pcap" format
 * provided in format_pcap.c.
 *
 * This is a trace file format and does not implement any live interface 
 * capture. This is covered by "pcapint" in format_pcap.c.
 *
 * This format supports both reading and writing, regardless of the version
 * of your PCAP library.
 */

#define DATA(x) ((struct pcapfile_format_data_t*)((x)->format_data))
#define DATAOUT(x) ((struct pcapfile_format_data_out_t*)((x)->format_data))
#define IN_OPTIONS DATA(libtrace)->options

typedef struct pcapfile_header_t {
                uint32_t magic_number;   /* magic number */
                uint16_t version_major;  /* major version number */
                uint16_t version_minor;  /* minor version number */
                int32_t  thiszone;       /* GMT to local correction */
                uint32_t sigfigs;        /* timestamp accuracy */
                uint32_t snaplen;        /* aka "wirelen" */
                uint32_t network;        /* data link type */
} pcapfile_header_t;

#define MAGIC1      0xa1b2c3d4  /* Original */
#define MAGIC2      0xa1b23c4d  /* Newer nanosecond format */
#define MAGIC1_REV  0xd4c3b2a1  /* Reversed byteorder detection */
#define MAGIC2_REV  0x4d3cb2a1

static bool pcapfile_can_write(libtrace_packet_t *packet) {
        /* Get the linktype */
        libtrace_linktype_t ltype = trace_get_link_type(packet);

        if (ltype == TRACE_TYPE_PCAPNG_META
                || ltype == TRACE_TYPE_CONTENT_INVALID
                || ltype == TRACE_TYPE_UNKNOWN
                || ltype == TRACE_TYPE_ERF_META
                || ltype == TRACE_TYPE_NONDATA) {

                return false;
        }

        return true;
}

static inline int header_is_backwards_magic(pcapfile_header_t *header) {
        return (header->magic_number == MAGIC1_REV || header->magic_number == MAGIC2_REV);
}

static inline int header_is_magic(pcapfile_header_t *header) {
        return (header->magic_number == MAGIC1 || header->magic_number == MAGIC2 ||
                header_is_backwards_magic(header));
}

static inline int trace_in_nanoseconds(pcapfile_header_t *header) {
        return (header->magic_number == MAGIC2 || header->magic_number == MAGIC2_REV);
}

struct pcapfile_format_data_t {
        struct {
                /* Indicates whether the event API should replicate the pauses
                 * between packets */
                int real_time;
        } options;

        /* The PCAP meta-header that should be written at the start of each
         * trace */
        pcapfile_header_t header;
        /* Indicates whether the input trace is started */
        bool started;
};

struct pcapfile_format_data_out_t {
        iow_t *file;
        int compress_type;
        int level;
        int flag;

};

static int pcapfile_probe_magic(io_t *io)
{
        pcapfile_header_t header;
        int len;
        len = wandio_peek(io, &header, sizeof(header));

        /* Is this long enough? */
        if (len < (int)sizeof(header)) {
                return 0;
        }
        /* Pcap magic? */
        if (header_is_magic(&header)) {
                return 1;
        }
        /* Nope, not pcap */
        return 0;
}


static int pcapfile_init_input(libtrace_t *libtrace) {
        libtrace->format_data = malloc(sizeof(struct pcapfile_format_data_t));
        if (!libtrace->format_data) {
                trace_set_err(libtrace, TRACE_ERR_INIT_FAILED, "Unable to allocate memory for "
                        "format data inside pcapfile_init_input()");
                return -1;
        }

        IN_OPTIONS.real_time = 0;
        DATA(libtrace)->started = false;
        return 0;
}

static int pcapfile_init_output(libtrace_out_t *libtrace) {
        libtrace->format_data = 
                malloc(sizeof(struct pcapfile_format_data_out_t));
        if (!libtrace->format_data) {
                trace_set_err_out(libtrace, TRACE_ERR_INIT_FAILED, "Unable to allocate memory for "
                        "format data inside pcapfile_init_output()");
                return -1;
        }

        DATAOUT(libtrace)->file=NULL;
        DATAOUT(libtrace)->compress_type=TRACE_OPTION_COMPRESSTYPE_NONE;
        DATAOUT(libtrace)->level=0;
        DATAOUT(libtrace)->flag=O_CREAT|O_WRONLY;

        return 0;
}


static inline uint16_t swaps(libtrace_t *libtrace, uint16_t num)
{
        /* To deal with open_dead traces that might try and use this
         * if we don't have any per trace data, assume host byte order
         */
        if (!DATA(libtrace))
                return num;
        
        /* We can use the PCAP magic number to determine the byte order */
        if (header_is_backwards_magic(&(DATA(libtrace)->header)))
                return byteswap16(num);

        return num;
}

static inline uint32_t swapl(libtrace_t *libtrace, uint32_t num)
{
        /* To deal with open_dead traces that might try and use this
         * if we don't have any per trace data, assume host byte order
         */
        if (!DATA(libtrace))
                return num;

        /* We can use the PCAP magic number to determine the byte order */
        if (header_is_backwards_magic(&(DATA(libtrace)->header)))
                return byteswap32(num);

        return num;
}


static int pcapfile_start_input(libtrace_t *libtrace) 
{
        int err;

        if (!libtrace->io) {
                libtrace->io=trace_open_file(libtrace);
                DATA(libtrace)->started=false;
        }

        if (!DATA(libtrace)->started) {

                if (!libtrace->io) {
                        trace_set_err(libtrace, TRACE_ERR_BAD_IO, "Trace cannot start IO in pcapfile_start_input()");
                        return -1;
                }

                err=wandio_read(libtrace->io,
                                &DATA(libtrace)->header,
                                sizeof(DATA(libtrace)->header));

                DATA(libtrace)->started = true;
                if (!(sizeof(DATA(libtrace)->header) > 0)) {
                        trace_set_err(libtrace, TRACE_ERR_INIT_FAILED, "Trace is missing header in pcapfile_start_input()");
                        return -1;
                }

                if (err<1) {
                        trace_set_err(libtrace, TRACE_ERR_INIT_FAILED,
                                "Error while reading pcap file header\n");
                        return -1;
                }

                if (err != (int)sizeof(DATA(libtrace)->header)) {
                        trace_set_err(libtrace, TRACE_ERR_INIT_FAILED,
                                "Incomplete pcap file header");
                        return -1;
                }
                
                if (!header_is_magic(&(DATA(libtrace)->header))) {
                        trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,
                                        "Not a pcap tracefile (magic=%08x)\n",swapl(libtrace,DATA(libtrace)->header.magic_number));
                        return -1; /* Not a pcap file */
                }

                if (swaps(libtrace,DATA(libtrace)->header.version_major)!=2
                        && swaps(libtrace,DATA(libtrace)->header.version_minor)!=4) {
                        trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,
                                        "Unknown pcap tracefile version %d.%d\n",
                                        swaps(libtrace,
                                                DATA(libtrace)->header.version_major),
                                        swaps(libtrace,
                                                DATA(libtrace)->header.version_minor));
                        return -1;
                }

        }

        return 0;
}

static int pcapfile_start_output(libtrace_out_t *libtrace UNUSED)
{
        /* We can't open the output file until we've seen the first packet.
         * This is because we need to know the DLT to set the "network" 
         * value in the meta-header */
        
        return 0;
}

static int pcapfile_config_input(libtrace_t *libtrace,
                trace_option_t option,
                void *data)
{
        switch(option) {
                case TRACE_OPTION_EVENT_REALTIME:
                        IN_OPTIONS.real_time = *(int *)data;
                        return 0;
                case TRACE_OPTION_META_FREQ:
                case TRACE_OPTION_SNAPLEN:
                case TRACE_OPTION_PROMISC:
                case TRACE_OPTION_FILTER:
                case TRACE_OPTION_HASHER:
                case TRACE_OPTION_REPLAY_SPEEDUP:
                case TRACE_OPTION_CONSTANT_ERF_FRAMING:
                        /* All these are either unsupported or handled
                         * by trace_config */
                        break;
                case TRACE_OPTION_DISCARD_META:
                        break;
        }
        
        trace_set_err(libtrace,TRACE_ERR_UNKNOWN_OPTION,
                        "Unknown option %i", option);
        return -1;
}

static int pcapfile_fin_input(libtrace_t *libtrace) 
{
        if (libtrace->io)
                wandio_destroy(libtrace->io);
        free(libtrace->format_data);
        return 0; /* success */
}

static int pcapfile_fin_output(libtrace_out_t *libtrace)
{
        if (DATAOUT(libtrace)->file)
                wandio_wdestroy(DATAOUT(libtrace)->file);
        free(libtrace->format_data);
        libtrace->format_data=NULL;
        return 0; /* success */
}

static int pcapfile_config_output(libtrace_out_t *libtrace,
                trace_option_output_t option,
                void *value)
{
        switch (option) {
                case TRACE_OPTION_OUTPUT_COMPRESS:
                        DATAOUT(libtrace)->level = *(int*)value;
                        return 0;
                case TRACE_OPTION_OUTPUT_COMPRESSTYPE:
                        DATAOUT(libtrace)->compress_type = *(int*)value;
                        return 0;
                case TRACE_OPTION_OUTPUT_FILEFLAGS:
                        DATAOUT(libtrace)->flag = *(int*)value;
                        return 0;
                default:
                        /* Unknown option */
                        trace_set_err_out(libtrace,TRACE_ERR_UNKNOWN_OPTION,
                                        "Unknown option");
                        return -1;
        }
        return -1;
}

static int pcapfile_prepare_packet(libtrace_t *libtrace, 
                libtrace_packet_t *packet, void *buffer, 
                libtrace_rt_types_t rt_type, uint32_t flags) {

        if (packet->buffer != buffer && 
                        packet->buf_control == TRACE_CTRL_PACKET) {
                free(packet->buffer);
        }

        if ((flags & TRACE_PREP_OWN_BUFFER) == TRACE_PREP_OWN_BUFFER) {
                packet->buf_control = TRACE_CTRL_PACKET;
        } else
                packet->buf_control = TRACE_CTRL_EXTERNAL;
        
        
        packet->buffer = buffer;
        packet->header = buffer;
        packet->payload = (char*)packet->buffer 
                + sizeof(libtrace_pcapfile_pkt_hdr_t);
        packet->type = rt_type; 

        if (libtrace->format_data == NULL) {
                if (pcapfile_init_input(libtrace))
                        return -1;
        }
        
        return 0;
}

static int pcapfile_read_packet(libtrace_t *libtrace, libtrace_packet_t *packet)
{
        int err;
        uint32_t flags = 0;
        size_t bytes_to_read = 0;

        if (!libtrace->format_data) {
                trace_set_err(libtrace, TRACE_ERR_BAD_FORMAT, "Trace format data missing, "
                        "call trace_create() before calling trace_read_packet()");
                return -1;
        }

        packet->type = pcap_linktype_to_rt(swapl(libtrace,
                                DATA(libtrace)->header.network));

        if (!packet->buffer || packet->buf_control == TRACE_CTRL_EXTERNAL) {
                packet->buffer = malloc((size_t)LIBTRACE_PACKET_BUFSIZE);
        }

        flags |= TRACE_PREP_OWN_BUFFER;

        err=wandio_read(libtrace->io,
                        packet->buffer,
                        sizeof(libtrace_pcapfile_pkt_hdr_t));

        if (err<0) {
                trace_set_err(libtrace,TRACE_ERR_WANDIO_FAILED,"reading packet");
                return -1;
        }
        if (err==0) {
                /* EOF */
                return 0;
        }

        if (err < (int)sizeof(libtrace_pcapfile_pkt_hdr_t)) {
                trace_set_err(libtrace, TRACE_ERR_BAD_PACKET, "Incomplete pcap packet header");
                return -1;
        }

        bytes_to_read = swapl(libtrace,((libtrace_pcapfile_pkt_hdr_t*)packet->buffer)->caplen);

        if (bytes_to_read >= (LIBTRACE_PACKET_BUFSIZE -
                        sizeof(libtrace_pcapfile_pkt_hdr_t))) {
                trace_set_err(libtrace, TRACE_ERR_BAD_PACKET, "Invalid caplen in pcap header (%u) - trace may be corrupt", (uint32_t)bytes_to_read);
                return -1;
        }

        /* If there is no payload to read, do not ask wandio_read to try and
         * read zero bytes - we'll just get back a zero that we will 
         * misinterpret as EOF! */
        if (bytes_to_read == 0) {
                packet->header = packet->buffer;
                return sizeof(libtrace_pcapfile_pkt_hdr_t);
        }

        err=wandio_read(libtrace->io,
                        (char*)packet->buffer+sizeof(libtrace_pcapfile_pkt_hdr_t),
                        (size_t)swapl(libtrace,((libtrace_pcapfile_pkt_hdr_t*)packet->buffer)->caplen)
                        );

        if (err<0) {
                trace_set_err(libtrace,TRACE_ERR_WANDIO_FAILED,"reading packet");
                return -1;
        }
        if (err==0) {
                return 0;
        }

        if (err < (int)bytes_to_read) {
                trace_set_err(libtrace, TRACE_ERR_WANDIO_FAILED, "Incomplete pcap packet body");
                return -1;
        }

        if (pcapfile_prepare_packet(libtrace, packet, packet->buffer,
                                packet->type, flags)) {
                return -1;
        }

        /* We may as well cache this value now, seeing as we already had to 
         * look it up */
        packet->cached.capture_length = bytes_to_read;  
        return sizeof(libtrace_pcapfile_pkt_hdr_t) + bytes_to_read;
}

static int pcapfile_write_packet(libtrace_out_t *out,
                libtrace_packet_t *packet)
{

        /* Check pcapfile can write this type of packet */
        if (!pcapfile_can_write(packet)) {
                return 0;
        }

        struct libtrace_pcapfile_pkt_hdr_t hdr;
        struct timeval tv = trace_get_timeval(packet);
        int numbytes;
        int ret;
        void *ptr;
        uint32_t remaining;
        libtrace_linktype_t linktype;

        ptr = trace_get_packet_buffer(packet,&linktype,&remaining);

        /* If this packet cannot be converted to a pcap linktype then
         * pop off the top header until it can be converted
         */
        while (libtrace_to_pcap_linktype(linktype)==TRACE_DLT_ERROR) {
                if (!demote_packet(packet)) {
                        trace_set_err_out(out, 
                                TRACE_ERR_NO_CONVERSION,
                                "pcap does not support this format");
                        return -1;
                }

                ptr = trace_get_packet_buffer(packet,&linktype,&remaining);
        }


        /* Now we know the link type write out a header if we've not done
         * so already
         */
        if (!DATAOUT(out)->file) {
                struct pcapfile_header_t pcaphdr;

                DATAOUT(out)->file=trace_open_file_out(out,
                                DATAOUT(out)->compress_type,
                                DATAOUT(out)->level,
                                DATAOUT(out)->flag);

                if (!DATAOUT(out)->file) {
                        trace_set_err_out(out,errno,"Unable to open file");
                        return -1;
                }

                pcaphdr.magic_number = 0xa1b2c3d4;
                pcaphdr.version_major = 2;
                pcaphdr.version_minor = 4;
                pcaphdr.thiszone = 0;
                pcaphdr.sigfigs = 0;
                pcaphdr.snaplen = 65536;
                pcaphdr.network = 
                        libtrace_to_pcap_linktype(linktype);

                wandio_wwrite(DATAOUT(out)->file, 
                                &pcaphdr, sizeof(pcaphdr));
        }


        hdr.ts_sec = (uint32_t)tv.tv_sec;
        hdr.ts_usec = (uint32_t)tv.tv_usec;
        hdr.caplen = trace_get_capture_length(packet);
        if (hdr.caplen >= LIBTRACE_PACKET_BUFSIZE) {
                trace_set_err_out(out, TRACE_ERR_BAD_PACKET, "Capture length is greater than buffer size in pcap_write_packet()");
                return -1;
        }
        /* PCAP doesn't include the FCS in its wire length value, but we do */
        if (linktype==TRACE_TYPE_ETH) {
                if (trace_get_wire_length(packet) >= 4) {
                        hdr.wirelen = trace_get_wire_length(packet)-4;
                }
                else {
                        hdr.wirelen = 0;
                }
        }
        else
                hdr.wirelen = trace_get_wire_length(packet);

        /* Reason for removing this assert:
         *
         * There exist some packets, e.g. in IPLS II, where the wire length
         * is clearly corrupt. When converting to pcap, we *could* try to
         * adjust the wire length to something sane but for now, I'll just let
         * the broken length persist through the conversion.
         *
         * XXX Is setting the wire length to zero the best solution in such
         * cases?
         */

        /* assert(hdr.wirelen < LIBTRACE_PACKET_BUFSIZE); */

        /* Ensure we have a valid capture length, especially if we're going
         * to "remove" the FCS from the wire length */
        if (hdr.caplen > hdr.wirelen)
                hdr.caplen = hdr.wirelen;

        /* Write the packet header */
        numbytes=wandio_wwrite(DATAOUT(out)->file,
                        &hdr, sizeof(hdr));

        if (numbytes!=sizeof(hdr)) 
                return -1;

        /* Write the rest of the packet now */
        ret=wandio_wwrite(DATAOUT(out)->file,
                        ptr,
                        hdr.caplen);

        if (ret!=(int)hdr.caplen)
                return -1;

        return numbytes+ret;
}

static int pcapfile_flush_output(libtrace_out_t *out) {

        return wandio_wflush(DATAOUT(out)->file);
}

static libtrace_linktype_t pcapfile_get_link_type(
                const libtrace_packet_t *packet) 
{
        return pcap_linktype_to_libtrace(rt_to_pcap_linktype(packet->type));
}

static libtrace_direction_t pcapfile_get_direction(const libtrace_packet_t *packet) 
{
        /* This function can be found in format_helper.c */
        return pcap_get_direction(packet);
}


static struct timeval pcapfile_get_timeval(
                const libtrace_packet_t *packet) 
{
        libtrace_pcapfile_pkt_hdr_t *hdr;
        struct timeval ts;

        memset(&ts, 0, sizeof(struct timeval));

        if (!packet) {
                fprintf(stderr, "NULL packet passed to pcapfile_get_timeval()\n");
                /* Return default timeval on error? */
                return ts;
        }

        if (!packet->header) {
                trace_set_err(packet->trace, TRACE_ERR_BAD_HEADER, "pcap packet with NULL header passed to "
                        "pcapfile_get_timeval()");
                /* Return default timeval on error? */
                return ts;
        }

        hdr = (libtrace_pcapfile_pkt_hdr_t*)packet->header;
        ts.tv_sec = swapl(packet->trace,hdr->ts_sec);
        /* Check trace is not a dummy calling trace_in_nanoseconds */
        if (DATA(packet->trace) && trace_in_nanoseconds(&DATA(packet->trace)->header))
                ts.tv_usec = swapl(packet->trace, hdr->ts_usec) / 1000;
        else
                ts.tv_usec = swapl(packet->trace,hdr->ts_usec);
        return ts;
}

static struct timespec pcapfile_get_timespec(
                const libtrace_packet_t *packet) 
{
        libtrace_pcapfile_pkt_hdr_t *hdr;
        struct timespec ts;

        memset(&ts, 0, sizeof(struct timespec));
        if (!packet) {
                fprintf(stderr, "NULL packet passed to pcapfile_get_timespec()");
                /* Return default timespec on error? */
                return ts;
        }

        if (!packet->header) {
                trace_set_err(packet->trace, TRACE_ERR_BAD_HEADER, "pcap packet with NULL header passed to "
                        "pcapfile_get_timespec()");
                /* Return fefault timespec on error? */
                return ts;
        }

        hdr = (libtrace_pcapfile_pkt_hdr_t*)packet->header;
        ts.tv_sec = swapl(packet->trace,hdr->ts_sec);
        /* Check trace is not a dummy calling trace_in_nanoseconds */
        if (DATA(packet->trace) && trace_in_nanoseconds(&DATA(packet->trace)->header))
                ts.tv_nsec = swapl(packet->trace, hdr->ts_usec);
        else
                ts.tv_nsec = swapl(packet->trace, hdr->ts_usec) * 1000;
        return ts;
}


static int pcapfile_get_capture_length(const libtrace_packet_t *packet) {
        libtrace_pcapfile_pkt_hdr_t *pcapptr; 

        if (!packet) {
                fprintf(stderr, "NULL packet passed to pcapfile_get_capture_length()\n");
                return TRACE_ERR_NULL_PACKET;
        }

        if (!packet->header) {
                trace_set_err(packet->trace, TRACE_ERR_BAD_HEADER, "pcap packet with NULL header passed to "
                        "pcapfile_get_capture_length()");
                return -1;
        }
        pcapptr = (libtrace_pcapfile_pkt_hdr_t *)packet->header;

        return swapl(packet->trace,pcapptr->caplen);
}

static int pcapfile_get_wire_length(const libtrace_packet_t *packet) {
        libtrace_pcapfile_pkt_hdr_t *pcapptr;

        if (!packet) {
                fprintf(stderr, "NULL packet passed to pcapfile_get_wire_length()\n");
                return TRACE_ERR_NULL_PACKET;
        }

        if (!packet->header) {
                trace_set_err(packet->trace, TRACE_ERR_BAD_HEADER, "pcap packet with NULL header passed to "
                        "pcapfile_get_wire_length()");
                return -1;
        }

        if (packet->payload == NULL) {
                return 0;
        }

        pcapptr = (libtrace_pcapfile_pkt_hdr_t *)packet->header;
        if (packet->type==pcap_linktype_to_rt(TRACE_DLT_EN10MB))
                /* Include the missing FCS */
                return swapl(packet->trace,pcapptr->wirelen)+4; 
        else if (packet->type==pcap_linktype_to_rt(TRACE_DLT_IEEE802_11_RADIO)){
                /* If the packet is Radiotap and the flags field indicates
                 * that the FCS is not included in the 802.11 frame, then
                 * we need to add 4 to the wire-length to account for it.
                 */
                uint8_t flags;
                void *link;
                libtrace_linktype_t linktype;
                link = trace_get_packet_buffer(packet, &linktype, NULL);
                trace_get_wireless_flags(link, linktype, &flags);
                if ((flags & TRACE_RADIOTAP_F_FCS) == 0)
                        return swapl(packet->trace,pcapptr->wirelen)+4;
        } else if (packet->type == pcap_linktype_to_rt(TRACE_DLT_LINUX_SLL)) {
                libtrace_sll_header_t *sll;
                sll = (libtrace_sll_header_t *)packet->payload;

                /* Account for FCS when dealing with Ethernet packets that are
                 * encapsulated in Linux SLL. This should fix the problem
                 * where the wire lengths differ if we convert the packet to
                 * ERF */
                if (ntohs(sll->protocol) == TRACE_ETHERTYPE_LOOPBACK)
                        return swapl(packet->trace,pcapptr->wirelen)+4;
        }

        return swapl(packet->trace,pcapptr->wirelen);
}

static int pcapfile_get_framing_length(const libtrace_packet_t *packet UNUSED) {
        return sizeof(libtrace_pcapfile_pkt_hdr_t);
}

static size_t pcapfile_set_capture_length(libtrace_packet_t *packet,size_t size) {
        libtrace_pcapfile_pkt_hdr_t *pcapptr = 0;

        if (!packet) {
                fprintf(stderr, "NULL packet passed into pcapfile_set_capture_length\n");
                /* Return -1 on error? */
                return ~0U;
        }

        if (!packet->header) {
                trace_set_err(packet->trace, TRACE_ERR_BAD_HEADER, "pcap packet with NULL header passed to "
                        "pcapfile_set_capture_length()");
                /* Return -1 on error? */
                return ~0U;
        }
        if (size > trace_get_capture_length(packet)) {
                /* Can't make a packet larger */
                return trace_get_capture_length(packet);
        }
        /* Reset the cached capture length */
        packet->cached.capture_length = -1;
        pcapptr = (libtrace_pcapfile_pkt_hdr_t *)packet->header;
        pcapptr->caplen = swapl(packet->trace,(uint32_t)size);
        return trace_get_capture_length(packet);
}

static struct libtrace_eventobj_t pcapfile_event(libtrace_t *libtrace, libtrace_packet_t *packet) {
        
        libtrace_eventobj_t event = {0,0,0.0,0};
        
        /* If we are being told to replay packets as fast as possible, then
         * we just need to read and return the next packet in the trace */

        if (IN_OPTIONS.real_time) {
                event.size = trace_read_packet(libtrace, packet);
                if (event.size < 1)
                        event.type = TRACE_EVENT_TERMINATE;
                else
                        event.type = TRACE_EVENT_PACKET;
                return event;
        } else {
                return trace_event_trace(libtrace, packet);
        }
}

static void pcapfile_help(void) {
        printf("pcapfile format module: $Revision: 1768 $\n");
        printf("Supported input URIs:\n");
        printf("\tpcapfile:/path/to/file\n");
        printf("\tpcapfile:/path/to/file.gz\n");
        printf("\n");
        printf("\te.g.: pcapfile:/tmp/trace.pcap\n");
        printf("\n");
}

static struct libtrace_format_t pcapfile = {
        "pcapfile",
        "$Id$",
        TRACE_FORMAT_PCAPFILE,
        NULL,                           /* probe filename */
        pcapfile_probe_magic,           /* probe magic */
        pcapfile_init_input,            /* init_input */
        pcapfile_config_input,          /* config_input */
        pcapfile_start_input,           /* start_input */
        NULL,                           /* pause_input */
        pcapfile_init_output,           /* init_output */
        pcapfile_config_output,         /* config_output */
        pcapfile_start_output,          /* start_output */
        pcapfile_fin_input,             /* fin_input */
        pcapfile_fin_output,            /* fin_output */
        pcapfile_read_packet,           /* read_packet */
        pcapfile_prepare_packet,        /* prepare_packet */
        NULL,                           /* fin_packet */
        pcapfile_write_packet,          /* write_packet */
        pcapfile_flush_output,          /* flush_output */
        pcapfile_get_link_type,         /* get_link_type */
        pcapfile_get_direction,         /* get_direction */
        NULL,                           /* set_direction */
        NULL,                           /* get_erf_timestamp */
        pcapfile_get_timeval,           /* get_timeval */
        pcapfile_get_timespec,          /* get_timespec */
        NULL,                           /* get_seconds */
        NULL,                           /* get_meta_section */
        NULL,                           /* seek_erf */
        NULL,                           /* seek_timeval */
        NULL,                           /* seek_seconds */
        pcapfile_get_capture_length,    /* get_capture_length */
        pcapfile_get_wire_length,       /* get_wire_length */
        pcapfile_get_framing_length,    /* get_framing_length */
        pcapfile_set_capture_length,    /* set_capture_length */
        NULL,                           /* get_received_packets */
        NULL,                           /* get_filtered_packets */
        NULL,                           /* get_dropped_packets */
        NULL,                           /* get_statistics */
        NULL,                           /* get_fd */
        pcapfile_event,         /* trace_event */
        pcapfile_help,                  /* help */
        NULL,                   /* next pointer */
        NON_PARALLEL(false)
};


void pcapfile_constructor(void) {
        register_format(&pcapfile);
}