source: trunk/lib/trace.c @ 795

/*
 * This file is part of libtrace
 *
 * Copyright (c) 2004 The University of Waikato, Hamilton, New Zealand.
 * Authors: Daniel Lawson 
 *          Perry Lorier 
 *          
 * All rights reserved.
 *
 * 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 General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with libtrace; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id$
 *
 */


/* @file 
 *
 * @brief Trace file processing library
 *
 * @author Daniel Lawson
 * @author Perry Lorier
 *
 * @internal
 */
#define _GNU_SOURCE
#include "common.h"
#include "config.h"
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <stdarg.h>

#ifdef HAVE_LIMITS_H
#  include <limits.h>
#endif

#ifdef HAVE_SYS_LIMITS_H
#  include <sys/limits.h>
#endif

#ifdef HAVE_NET_IF_ARP_H
#  include <net/if_arp.h>
#endif

#ifdef HAVE_NET_IF_H
#  include <net/if.h>
#endif

#ifdef HAVE_NETINET_IN_H
#  include <netinet/in.h>
#endif

#ifdef HAVE_NET_ETHERNET_H
#  include <net/ethernet.h>
#endif

#ifdef HAVE_NETINET_IF_ETHER_H
#  include <netinet/if_ether.h>
#endif

#include <time.h>

#include "libtrace.h"
#include "fifo.h"
#include "libtrace_int.h"
#include "parse_cmd.h"

#if HAVE_PCAP_BPF_H
#  include <pcap-bpf.h>
#else
#  ifdef HAVE_NET_BPF_H
#    include <net/bpf.h>
#  endif
#endif

#include "libtrace_int.h"
#include "format_helper.h"
#include "rt_protocol.h"

#define MAXOPTS 1024


static struct libtrace_format_t *formats_list = 0;

/* strncpy is not assured to copy the final \0, so we
 * will use our own one that does
 */
static void xstrncpy(char *dest, const char *src, size_t n)
{
        strncpy(dest,src,n);
        dest[n]='\0';
}
 
static char *xstrndup(const char *src,size_t n)
{       
        char *ret=(char*)malloc(n+1);
        xstrncpy(ret,src,n);
        return ret;
}

void register_format(struct libtrace_format_t *f) {
        assert(f->next==NULL);
        f->next=formats_list;
        formats_list=f;
        /* Now, verify things 
         * This #if can be changed to a 1 to output warnings about inconsistant
         * functions being provided by format modules.  This generally is very
         * noisy, as almost all modules don't implement one or more functions
         * for various reasons.  This is very useful when checking a new 
         * format module is sane.
         */ 
#if 0
        if (f->init_input) {
#define REQUIRE(x) \
                if (!f->x) \
                        fprintf(stderr,"%s: Input format should provide " #x "\n",f->name)
                REQUIRE(read_packet);
                REQUIRE(start_input);
                REQUIRE(fin_input);
                REQUIRE(get_link_type);
                REQUIRE(get_capture_length);
                REQUIRE(get_wire_length);
                REQUIRE(get_framing_length);
                REQUIRE(trace_event);
                if (!f->get_erf_timestamp 
                        && !f->get_seconds
                        && !f->get_timeval) {
                        fprintf(stderr,"%s: A trace format capable of input, should provide at least one of\n"
"get_erf_timestamp, get_seconds or trace_timeval\n",f->name);
                }
                if (f->trace_event!=trace_event_trace) {
                        /* Theres nothing that a trace file could optimise with
                         * config_input
                         */
                        REQUIRE(pause_input);
                        REQUIRE(config_input);
                        REQUIRE(get_fd);
                }
                else {
                        if (f->get_fd) {
                                fprintf(stderr,"%s: Unnecessary get_fd\n",
                                                f->name);
                        }
                }
#undef REQUIRE
        }
        else {
#define REQUIRE(x) \
                if (f->x) \
                        fprintf(stderr,"%s: Non Input format shouldn't need " #x "\n",f->name)
                REQUIRE(read_packet);
                REQUIRE(start_input);
                REQUIRE(pause_input);
                REQUIRE(fin_input);
                REQUIRE(get_link_type);
                REQUIRE(get_capture_length);
                REQUIRE(get_wire_length);
                REQUIRE(get_framing_length);
                REQUIRE(trace_event);
                REQUIRE(get_seconds);
                REQUIRE(get_timeval);
                REQUIRE(get_erf_timestamp);
#undef REQUIRE
        }
        if (f->init_output) {
#define REQUIRE(x) \
                if (!f->x) \
                        fprintf(stderr,"%s: Output format should provide " #x "\n",f->name)
                REQUIRE(write_packet);
                REQUIRE(start_output);
                REQUIRE(config_output);
                REQUIRE(fin_output);
#undef REQUIRE
        }
        else {
#define REQUIRE(x) \
                if (f->x) \
                        fprintf(stderr,"%s: Non Output format shouldn't need " #x "\n",f->name)
                REQUIRE(write_packet);
                REQUIRE(start_output);
                REQUIRE(config_output);
                REQUIRE(fin_output);
#undef REQUIRE
        }
#endif
}

void erf_constructor();
void legacy_constructor();
void linuxnative_constructor();
void pcap_constructor();
void pcapfile_constructor();
void rt_constructor();
void wag_constructor();

/* call all the constructors if they haven't yet all been called */
void trace_init(void)
{
        if (!formats_list) {
                erf_constructor();
                legacy_constructor();
#ifdef HAVE_NETPACKET_PACKET_H
                linuxnative_constructor();
#endif
#ifdef HAVE_PCAP
                pcap_constructor();
#endif
                pcapfile_constructor();
                rt_constructor();
                wag_constructor();
        }
}

/* Prints help information for libtrace 
 *
 * Function prints out some basic help information regarding libtrace,
 * and then prints out the help() function registered with each input module
 */
DLLEXPORT void trace_help() {
        struct libtrace_format_t *tmp;
        trace_init();
        printf("libtrace %s\n",PACKAGE_VERSION);
        for(tmp=formats_list;tmp;tmp=tmp->next) {
                if (tmp->help)
                        tmp->help();
        }
}

#define RP_BUFSIZE 65536
#define URI_PROTO_LINE 16

/* Gets the name of the output format for a given output trace. 
 *
 * @params libtrace     the output trace to get the name of the format for
 * @returns callee-owned null-terminated char* containing the output format
 *
 */
DLLEXPORT SIMPLE_FUNCTION
char *trace_get_output_format(const libtrace_out_t *libtrace) {
        char * format = libtrace->format->name;

        return format;
}


/* Create a trace file from a URI
 *
 * @params char * containing a valid libtrace URI
 * @returns opaque pointer to a libtrace_t
 *
 * Valid URI's are:
 *  erf:/path/to/erf/file
 *  erf:/path/to/erf/file.gz
 *  erf:/path/to/rtclient/socket
 *  erf:-                       (stdin)
 *  dag:/dev/dagcard
 *  pcapint:pcapinterface               (eg: pcapint:eth0)
 *  pcap:/path/to/pcap/file
 *  pcap:-
 *  rtclient:hostname
 *  rtclient:hostname:port
 *  wag:-
 *  wag:/path/to/wag/file
 *  wag:/path/to/wag/file.gz
 *  wag:/path/to/wag/socket
 *
 * If an error occured when attempting to open a trace, NULL is returned
 * and an error is output to stdout.
 */
DLLEXPORT libtrace_t *trace_create(const char *uri) {
        libtrace_t *libtrace = 
                        (libtrace_t *)malloc(sizeof(libtrace_t));
        char *scan = 0;
        const char *uridata = 0;                  
        struct libtrace_format_t *tmp;

        trace_init();

        assert(uri && "Passing NULL to trace_create makes me a very sad program");
        
        libtrace->err.err_num = TRACE_ERR_NOERROR;
        libtrace->format=NULL;
        
        /* parse the URI to determine what sort of event we are dealing with */
        if ((uridata = trace_parse_uri(uri, &scan)) == 0) {
                trace_set_err(libtrace,TRACE_ERR_BAD_FORMAT,"Bad uri format (%s)",uri);
                return libtrace;
        }
        
        libtrace->event.tdelta = 0.0;
        libtrace->filter = NULL;
        libtrace->snaplen = 0;
        libtrace->started=false;

        for (tmp=formats_list;tmp;tmp=tmp->next) {
                if (strlen(scan) == strlen(tmp->name) &&
                                strncasecmp(scan, tmp->name, strlen(scan)) == 0
                                ) {
                        libtrace->format=tmp;
                        break;
                }
        }
        if (libtrace->format == 0) {
                trace_set_err(libtrace, TRACE_ERR_BAD_FORMAT,
                                "Unknown format (%s)",scan);
                return libtrace;
        }

        libtrace->uridata = strdup(uridata);
        /* libtrace->format now contains the type of uri
         * libtrace->uridata contains the appropriate data for this
         */
        
        if (libtrace->format->init_input) {
                int err=libtrace->format->init_input(libtrace);
                assert (err==-1 || err==0);
                if (err==-1) {
                        /* init_input should call trace_set_err to set 
                         * the error message
                         */
                        return libtrace;
                }
        } else {
                trace_set_err(libtrace,TRACE_ERR_UNSUPPORTED,
                                "Format does not support input (%s)",scan);
                return libtrace;
        }
        

        libtrace->fifo = create_tracefifo(1048576);
        if (!libtrace->fifo) {
                trace_set_err(libtrace,ENOMEM,"Could not allocate memory for fifo");
                free(scan);
                return libtrace;
        }
        assert(libtrace->fifo);
        free(scan);
        libtrace->err.err_num=TRACE_ERR_NOERROR;
        libtrace->err.problem[0]='\0';
        return libtrace;
}

/* Creates a "dummy" trace file that has only the format type set.
 *
 * @returns opaque pointer to a (sparsely initialised) libtrace_t
 *
 * IMPORTANT: Do not attempt to call trace_read_packet or other such functions
 * with the dummy trace. Its intended purpose is to act as a packet->trace for
 * libtrace_packet_t's that are not associated with a libtrace_t structure.
 */
DLLEXPORT libtrace_t * trace_create_dead (const char *uri) {
        libtrace_t *libtrace = (libtrace_t *) malloc(sizeof(libtrace_t));
        char *scan = (char *)calloc(sizeof(char),URI_PROTO_LINE);
        char *uridata;
        struct libtrace_format_t *tmp;
        
        libtrace->err.err_num = TRACE_ERR_NOERROR;

        if((uridata = strchr(uri,':')) == NULL) {
                xstrncpy(scan, uri, strlen(uri));
        } else {
                xstrncpy(scan,uri, (uridata - uri));
        }
        
        libtrace->format = 0;   
        
        for(tmp=formats_list;tmp;tmp=tmp->next) {
                if (strlen(scan) == strlen(tmp->name) &&
                                !strncasecmp(scan,
                                        tmp->name,
                                        strlen(scan))) {
                                libtrace->format=tmp;
                                break;
                                }
        }
        if (libtrace->format == 0) {
                trace_set_err(libtrace,TRACE_ERR_BAD_FORMAT,
                                "Unknown format (%s)",scan);
                return 0;
        }

        libtrace->format_data = NULL;
        free(scan);
        return libtrace;

}

/* Creates a trace output file from a URI. 
 *
 * @param uri   the uri string describing the output format and destination
 * @returns opaque pointer to a libtrace_output_t 
 *
 *  If an error occured when attempting to open the output trace, NULL is
 *  returned and trace_errno is set. 
 */
        
DLLEXPORT libtrace_out_t *trace_create_output(const char *uri) {
        libtrace_out_t *libtrace = 
                        (libtrace_out_t*)malloc(sizeof(libtrace_out_t));
        
        char *scan = 0;
        const char *uridata = 0;
        struct libtrace_format_t *tmp;

        trace_init();

        libtrace->err.err_num = TRACE_ERR_NOERROR;
        strcpy(libtrace->err.problem,"Error message set\n");
        
        /* parse the URI to determine what sort of event we are dealing with */

        if ((uridata = trace_parse_uri(uri, &scan)) == 0) {
                trace_set_err_out(libtrace,TRACE_ERR_BAD_FORMAT,
                                "Bad uri format (%s)",uri);
                return libtrace;
        }
        
        libtrace->format = NULL;
        for(tmp=formats_list;tmp;tmp=tmp->next) {
                if (strlen(scan) == strlen(tmp->name) &&
                                !strncasecmp(scan,
                                        tmp->name,
                                        strlen(scan))) {
                                libtrace->format=tmp;
                                break;
                                }
        }
        if (libtrace->format == NULL) {
                trace_set_err_out(libtrace,TRACE_ERR_BAD_FORMAT,
                                "Unknown output format (%s)",scan);
                return libtrace;
        }
        libtrace->uridata = strdup(uridata);


        /* libtrace->format now contains the type of uri
         * libtrace->uridata contains the appropriate data for this
         */

        if (libtrace->format->init_output) {
                /* 0 on success, -1 on failure */
                switch(libtrace->format->init_output(libtrace)) {
                        case -1: /* failure */
                                free(libtrace);
                                return libtrace;
                        case 0: /* success */
                                break;
                        default:
                                assert(!"init_output() should return -1 for failure, or 0 for success");
                }
        } else {
                trace_set_err_out(libtrace,TRACE_ERR_UNSUPPORTED,
                                "Format does not support writing (%s)",scan);
                return libtrace;
        }


        free(scan);
        libtrace->started=false;
        return libtrace;
}

/* Start a trace
 * @param libtrace      the input trace to start
 * @returns 0 on success
 *
 * This does the work associated with actually starting up
 * the trace.  it may fail.
 */
DLLEXPORT int trace_start(libtrace_t *libtrace)
{
        assert(libtrace);
        if (libtrace->format->start_input) {
                int ret=libtrace->format->start_input(libtrace);
                if (ret < 0) {
                        return ret;
                }
        }

        libtrace->started=true;
        return 0;
}

DLLEXPORT int trace_start_output(libtrace_out_t *libtrace) 
{
        assert(libtrace);
        if (libtrace->format->start_output) {
                int ret=libtrace->format->start_output(libtrace);
                if (ret < 0) {
                        return ret;
                }
        }

        libtrace->started=true;
        return 0;
}

DLLEXPORT int trace_pause(libtrace_t *libtrace)
{
        assert(libtrace);
        assert(libtrace->started && "BUG: Called trace_pause without calling trace_start first");
        if (libtrace->format->pause_input)
                libtrace->format->pause_input(libtrace);
        libtrace->started=false;
        return 0;
}

DLLEXPORT int trace_config(libtrace_t *libtrace,
                trace_option_t option,
                void *value)
{
        int ret;
        if (libtrace->format->config_input) {
                ret=libtrace->format->config_input(libtrace,option,value);
                if (ret==0)
                        return 0;
        }
        switch(option) {
                case TRACE_OPTION_SNAPLEN:
                        libtrace->snaplen=*(int*)value;
                        return 0;
                case TRACE_OPTION_FILTER:
                        libtrace->filter=(libtrace_filter_t *)value;
                        return 0;
                case TRACE_OPTION_PROMISC:
                        trace_set_err(libtrace,TRACE_ERR_OPTION_UNAVAIL,
                                "Promisc mode is not supported by this format module");
                        return -1;
        }
        trace_set_err(libtrace,TRACE_ERR_UNKNOWN_OPTION,
                "Unknown option %i", option);
        return -1;
}

/* Parses an output options string and calls the appropriate function to deal with output options.
 *
 * @param libtrace      the output trace object to apply the options to
 * @param options       the options string
 * @returns -1 if option configuration failed, 0 otherwise
 *
 * @author Shane Alcock
 */
DLLEXPORT int trace_config_output(libtrace_out_t *libtrace, 
                trace_option_output_t option,
                void *value) {
        if (libtrace->format->config_output) {
                return libtrace->format->config_output(libtrace, option, value);
        }
        return -1;
}

/* Close a trace file, freeing up any resources it may have been using
 *
 */
DLLEXPORT void trace_destroy(libtrace_t *libtrace) {
        assert(libtrace);
        if (libtrace->started && libtrace->format->pause_input)
                libtrace->format->pause_input(libtrace);
        libtrace->format->fin_input(libtrace);
        /* need to free things! */
        free(libtrace->uridata);
        destroy_tracefifo(libtrace->fifo);
        free(libtrace);
}


DLLEXPORT void trace_destroy_dead(libtrace_t *libtrace) {
        assert(libtrace);
        free(libtrace);
}
/* Close an output trace file, freeing up any resources it may have been using
 *
 * @param libtrace      the output trace file to be destroyed
 *
 * @author Shane Alcock
 * */
DLLEXPORT void trace_destroy_output(libtrace_out_t *libtrace) {
        assert(libtrace);
        libtrace->format->fin_output(libtrace);
        free(libtrace->uridata);
        free(libtrace);
}

DLLEXPORT libtrace_packet_t *trace_create_packet() {
        libtrace_packet_t *packet = 
                (libtrace_packet_t*)calloc(1,sizeof(libtrace_packet_t));
        packet->buf_control=TRACE_CTRL_PACKET;
        return packet;
}

DLLEXPORT libtrace_packet_t *trace_copy_packet(const libtrace_packet_t *packet) {
        libtrace_packet_t *dest = 
                (libtrace_packet_t *)malloc(sizeof(libtrace_packet_t));
        dest->trace=packet->trace;
        dest->buffer=malloc(
                        trace_get_framing_length(packet)
                        +trace_get_capture_length(packet));
        dest->header=dest->buffer;
        dest->payload=(void*)
                ((char*)dest->buffer+trace_get_framing_length(packet));
        dest->size=packet->size;
        dest->type=packet->type;
        dest->buf_control=TRACE_CTRL_PACKET;
        memcpy(dest->header,packet->header,trace_get_framing_length(packet));
        memcpy(dest->payload,packet->payload,trace_get_capture_length(packet));

        return dest;
}

/** Destroy a packet object
 *
 * sideeffect: sets packet to NULL
 */
DLLEXPORT void trace_destroy_packet(libtrace_packet_t **packet) {
        if ((*packet)->buf_control == TRACE_CTRL_PACKET) {
                free((*packet)->buffer);
        }
        free((*packet));
        *packet = NULL;
}       

/* Read one packet from the trace into buffer
 *
 * @param libtrace      the libtrace opaque pointer
 * @param packet        the packet opaque pointer
 * @returns 0 on EOF, negative value on error
 *
 */
DLLEXPORT int trace_read_packet(libtrace_t *libtrace, libtrace_packet_t *packet) {

        assert(libtrace && "You called trace_read_packet() with a NULL libtrace parameter!\n");
        assert(libtrace->started && "BUG: You must call libtrace_start() before trace_read_packet()\n");
        assert(packet);
        assert((packet->buf_control==TRACE_CTRL_PACKET || packet->buf_control==TRACE_CTRL_EXTERNAL)&&
                "BUG: You must allocate a packet using packet_create()");
      
        /* Store the trace we are reading from into the packet opaque 
         * structure */
        packet->trace = libtrace;

        if (libtrace->format->read_packet) {
                do {
                        packet->size=libtrace->format->read_packet(libtrace,packet);
                        if (packet->size==(size_t)-1 || packet->size==0) {
                                return packet->size;
                        }
                        if (libtrace->filter) {
                                /* If the filter doesn't match, read another
                                 * packet
                                 */
                                if (!trace_bpf_filter(libtrace->filter,packet)){
                                        continue;
                                }
                        }
                        if (libtrace->snaplen>0) {
                                /* Snap the packet */
                                trace_set_capture_length(packet,
                                                libtrace->snaplen);
                        }
                        return packet->size;
                } while(1);
        }
        trace_set_err(libtrace,TRACE_ERR_UNSUPPORTED,"This format does not support reading packets\n");
        packet->size=-1;
        return -1;
}

/* Writes a packet to the specified output
 *
 * @param libtrace      describes the output format, destination, etc.
 * @param packet        the packet to be written out
 * @returns the number of bytes written, -1 if write failed
 *
 * @author Shane Alcock
 * */
DLLEXPORT int trace_write_packet(libtrace_out_t *libtrace, const libtrace_packet_t *packet) {
        assert(libtrace);
        assert(packet); 
        /* Verify the packet is valid */
        assert(packet->size<65536);
        assert(packet->size>0);
        assert(libtrace->started);

        if (libtrace->format->write_packet) {
                return libtrace->format->write_packet(libtrace, packet);
        }
        return -1;
}

DLLEXPORT void *trace_get_link(const libtrace_packet_t *packet) {
        return (void *)packet->payload;
}

/*
typedef struct legacy_framing {
        uint64_t        ts;
        uint32_t        crc;
        uint32_t        header;
        uint32_t        data[12]; // pad to 64 bytes 
} legacy_framing_t;
*/


/* Get the current time in DAG time format 
 * @param packet        a pointer to a libtrace_packet structure
 * @returns a 64 bit timestamp in DAG ERF format (upper 32 bits are the seconds
 * past 1970-01-01, the lower 32bits are partial seconds)
 * @author Daniel Lawson
 */ 
DLLEXPORT uint64_t trace_get_erf_timestamp(const libtrace_packet_t *packet) {
        uint64_t timestamp = 0;
        double seconds = 0.0;
        struct timeval ts;

        assert(packet->size>0 && packet->size<65536);

        if (packet->trace->format->get_erf_timestamp) {
                /* timestamp -> timestamp */
                timestamp = packet->trace->format->get_erf_timestamp(packet);
        } else if (packet->trace->format->get_timeval) {
                /* timeval -> timestamp */
                ts = packet->trace->format->get_timeval(packet);
                timestamp = ((((uint64_t)ts.tv_sec) << 32) + \
                                (((uint64_t)ts.tv_usec * UINT_MAX)/1000000));
        } else if (packet->trace->format->get_seconds) {
                /* seconds -> timestamp */
                seconds = packet->trace->format->get_seconds(packet);
                timestamp = ((uint64_t)((uint32_t)seconds) << 32) + \
                      (uint64_t)(( seconds - (uint32_t)seconds   ) * UINT_MAX);
        }
        return timestamp;
}

/* Get the current time in struct timeval
 * @param packet        a pointer to a libtrace_packet structure
 *
 * @returns time that this packet was seen in a struct timeval
 * @author Daniel Lawson
 * @author Perry Lorier
 */ 
DLLEXPORT struct timeval trace_get_timeval(const libtrace_packet_t *packet) {
        struct timeval tv;
        uint64_t ts = 0;
        double seconds = 0.0;
        assert(packet->size>0 && packet->size<65536);
        if (packet->trace->format->get_timeval) {
                /* timeval -> timeval */
                tv = packet->trace->format->get_timeval(packet);
        } else if (packet->trace->format->get_erf_timestamp) {
                /* timestamp -> timeval */
                ts = packet->trace->format->get_erf_timestamp(packet);
#if __BYTE_ORDER == __BIG_ENDIAN
                tv.tv_sec = ts & 0xFFFFFFFF;
#elif __BYTE_ORDER == __LITTLE_ENDIAN
                tv.tv_sec = ts >> 32;
#else
#error "What on earth are you running this on?"
#endif
                tv.tv_usec = ((ts&0xFFFFFFFF)*1000000)>>32;
                if (tv.tv_usec >= 1000000) {
                        tv.tv_usec -= 1000000;
                        tv.tv_sec += 1;
                }
        } else if (packet->trace->format->get_seconds) {
                /* seconds -> timeval */
                seconds = packet->trace->format->get_seconds(packet);
                tv.tv_sec = (uint32_t)seconds;
                tv.tv_usec = (uint32_t)(((seconds - tv.tv_sec) * 1000000)/UINT_MAX);
        }

        return tv;
}

/* Get the current time in floating point seconds
 * @param packet        a pointer to a libtrace_packet structure
 * @returns time that this packet was seen in 64bit floating point seconds
 * @author Perry Lorier
 */ 
DLLEXPORT double trace_get_seconds(const libtrace_packet_t *packet) {
        double seconds = 0.0;
        uint64_t ts = 0;
        struct timeval tv;

        assert(packet->size>0 && packet->size<65536);
        
        if (packet->trace->format->get_seconds) {
                /* seconds->seconds */
                seconds = packet->trace->format->get_seconds(packet);
        } else if (packet->trace->format->get_erf_timestamp) {
                /* timestamp -> seconds */
                ts = packet->trace->format->get_erf_timestamp(packet);
                seconds =  (ts>>32) + ((ts & UINT_MAX)*1.0 / UINT_MAX);
        } else if (packet->trace->format->get_timeval) {
                /* timeval -> seconds */
                tv = packet->trace->format->get_timeval(packet);
                seconds = tv.tv_sec + ((tv.tv_usec * 1.0) / 1000000);
        }

        return seconds;
}

DLLEXPORT size_t trace_get_capture_length(const libtrace_packet_t *packet) {

        assert(packet->size<65536);

        if (packet->trace->format->get_capture_length) {
                return packet->trace->format->get_capture_length(packet);
        }
        return -1;
}
        
/* Get the size of the packet as it was seen on the wire.
 * @param packet        a pointer to a libtrace_packet structure
 *
 * @returns the size of the packet as it was on the wire.
 * @author Perry Lorier
 * @author Daniel Lawson
 * @note Due to the trace being a header capture, or anonymisation this may
 * not be the same as the Capture Len.
 */ 
DLLEXPORT size_t trace_get_wire_length(const libtrace_packet_t *packet){
        assert(packet->size>0 && packet->size<65536);

        if (packet->trace->format->get_wire_length) {
                return packet->trace->format->get_wire_length(packet);
        }
        return -1;

}

/* Get the length of the capture framing headers.
 * @param packet        the packet opaque pointer
 * @returns the size of the packet as it was on the wire.
 * @author Perry Lorier
 * @author Daniel Lawson
 * @note this length corresponds to the difference between the size of a 
 * captured packet in memory, and the captured length of the packet
 */ 
DLLEXPORT SIMPLE_FUNCTION
size_t trace_get_framing_length(const libtrace_packet_t *packet) {
        if (packet->trace->format->get_framing_length) {
                return packet->trace->format->get_framing_length(packet);
        }
        return -1;
}


/* Get the type of the link layer
 * @param packet        a pointer to a libtrace_packet structure
 * @returns libtrace_linktype_t
 * @author Perry Lorier
 * @author Daniel Lawson
 */
DLLEXPORT libtrace_linktype_t trace_get_link_type(const libtrace_packet_t *packet ) {
        if (packet->trace->format->get_link_type) {
                return packet->trace->format->get_link_type(packet);
        }
        return (libtrace_linktype_t)-1;
}

/* process a libtrace event
 * @param trace the libtrace opaque pointer
 * @param packet the libtrace_packet opaque pointer
 * @returns
 *  TRACE_EVENT_IOWAIT  Waiting on I/O on fd
 *  TRACE_EVENT_SLEEP   Next event in seconds
 *  TRACE_EVENT_PACKET  Packet arrived in buffer with size size
 *  TRACE_EVENT_TERMINATE Trace terminated (perhaps with an error condition)
 * FIXME currently keeps a copy of the packet inside the trace pointer,
 * which in turn is stored inside the new packet object...
 * @author Perry Lorier
 */
DLLEXPORT libtrace_eventobj_t trace_event(libtrace_t *trace, 
                libtrace_packet_t *packet) {
        libtrace_eventobj_t event = {TRACE_EVENT_IOWAIT,0,0.0,0};

        if (!trace) {
                fprintf(stderr,"You called trace_event() with a NULL trace object!\n");
        }
        assert(trace);
        assert(packet);

        /* Store the trace we are reading from into the packet opaque
         * structure */
        packet->trace = trace;

        if (packet->trace->format->trace_event) {
                return packet->trace->format->trace_event(trace,packet);
        } else {
                return event;
        }

}

/* setup a BPF filter
 * @param filterstring a char * containing the bpf filter string
 * @returns opaque pointer pointer to a libtrace_filter_t object
 * @author Daniel Lawson
 */
DLLEXPORT libtrace_filter_t *trace_bpf_setfilter(const char *filterstring) {
#if HAVE_BPF
        libtrace_filter_t *filter = (libtrace_filter_t*)
                                malloc(sizeof(libtrace_filter_t));
        filter->filterstring = strdup(filterstring);
        filter->flag = 0;
        return filter;
#else
        fprintf(stderr,"This version of libtrace does not have bpf filter support\n");
        return NULL;
#endif
}

DLLEXPORT void trace_destroy_bpf(libtrace_filter_t *filter)
{
#if HAVE_BPF
        free(filter->filterstring);
        if (filter->flag)
                pcap_freecode(&filter->filter);
        free(filter);
#else

#endif
}

/* compile a bpf filter, now we know what trace it's on
 * @internal
 *
 * @returns -1 on error, 0 on success
 */
int trace_bpf_compile(libtrace_filter_t *filter,
                const libtrace_packet_t *packet ) {
#if HAVE_BPF
        void *linkptr = 0;
        assert(filter);

        /* If this isn't a real packet, then fail */
        linkptr = trace_get_link(packet);
        if (!linkptr) {
                trace_set_err(packet->trace,
                                TRACE_ERR_BAD_PACKET,"Packet has no payload");
                return -1;
        }
        
        if (filter->filterstring && ! filter->flag) {
                pcap_t *pcap;
                libtrace_linktype_t linktype=trace_get_link_type(packet);
                if (linktype==(libtrace_linktype_t)-1) {
                        trace_set_err(packet->trace,TRACE_ERR_BAD_PACKET,
                                        "Packet has an unknown linktype");
                        return -1;
                }
                if (libtrace_to_pcap_dlt(linktype) == -1) {
                        trace_set_err(packet->trace,TRACE_ERR_BAD_PACKET,
                                        "Unknown pcap equivilent linktype");
                        return -1;
                }
                pcap=(pcap_t *)pcap_open_dead(
                                libtrace_to_pcap_dlt(linktype),
                                1500);
                /* build filter */
                if (pcap_compile( pcap, &filter->filter, filter->filterstring, 
                                        1, 0)) {
                        pcap_close(pcap);
                        trace_set_err(packet->trace,TRACE_ERR_BAD_PACKET,
                                        "Packet has no payload");
                        return -1;
                }
                pcap_close(pcap);
                filter->flag=1;
        }
        return 0;
#else
        assert(!"This should never be called when BPF not enabled");
        trace_set_err(packet->trace,TRACE_ERR_OPTION_UNAVAIL,
                                "Feature unavailable");
        return -1;
#endif
}

DLLEXPORT int trace_bpf_filter(libtrace_filter_t *filter,
                        const libtrace_packet_t *packet) {
#if HAVE_BPF
        void *linkptr = 0;
        int clen = 0;
        assert(filter);
        assert(packet);
        linkptr = trace_get_link(packet);
        if (!linkptr) {
                return 0;
        }

        /* We need to compile it now, because before we didn't know what the 
         * link type was
         */
        if (trace_bpf_compile(filter,packet)==-1)
                return -1;
        
        clen = trace_get_capture_length(packet);

        assert(filter->flag);
        return bpf_filter(filter->filter.bf_insns, linkptr, clen, clen);
#else
        fprintf(stderr,"This version of libtrace does not have bpf filter support\n");
        return 0;
#endif
}

/* Set the direction flag, if it has one
 * @param packet the packet opaque pointer
 * @param direction the new direction (0,1,2,3)
 * @returns a signed value containing the direction flag, or -1 if this is not supported
 */
DLLEXPORT libtrace_direction_t trace_set_direction(libtrace_packet_t *packet, 
                libtrace_direction_t direction) 
{
        assert(packet);
        assert(packet->size>0 && packet->size<65536);
        if (packet->trace->format->set_direction) {
                return packet->trace->format->set_direction(packet,direction);
        }
        return -1;
}

/* Get the direction flag, if it has one
 * @param packet a pointer to a libtrace_packet structure
 * @returns a signed value containing the direction flag, or -1 if this is not supported
 * The direction is defined as 0 for packets originating locally (ie, outbound)
 * and 1 for packets originating remotely (ie, inbound).
 * Other values are possible, which might be overloaded to mean special things
 * for a special trace.
 * @author Daniel Lawson
 */
DLLEXPORT libtrace_direction_t trace_get_direction(const libtrace_packet_t *packet) 
{
        assert(packet);
        assert(packet->size>0 && packet->size<65536);
        if (packet->trace->format->get_direction) {
                return packet->trace->format->get_direction(packet);
        }
        return -1;
}

#define ROOT_SERVER(x) ((x) < 512)
#define ROOT_CLIENT(x) ((512 <= (x)) && ((x) < 1024))
#define NONROOT_SERVER(x) ((x) >= 5000)
#define NONROOT_CLIENT(x) ((1024 <= (x)) && ((x) < 5000))
#define DYNAMIC(x) ((49152 < (x)) && ((x) < 65535))
#define SERVER(x) ROOT_SERVER(x) || NONROOT_SERVER(x)
#define CLIENT(x) ROOT_CLIENT(x) || NONROOT_CLIENT(x) 

/* Attempt to deduce the 'server' port
 * @param protocol the IP protocol (eg, 6 or 17 for TCP or UDP)
 * @param source the TCP or UDP source port
 * @param dest the TCP or UDP destination port
 * @returns a hint as to which port is the server port
 * @author Daniel Lawson
 */
DLLEXPORT int8_t trace_get_server_port(uint8_t protocol UNUSED, uint16_t source, uint16_t dest) {
        /*
         * * If the ports are equal, return DEST
         * * Check for well-known ports in the given protocol
         * * Root server ports: 0 - 511
         * * Root client ports: 512 - 1023
         * * non-root client ports: 1024 - 4999
         * * non-root server ports: 5000+
         * * Check for static ranges: 1024 - 49151
         * * Check for dynamic ranges: 49152 - 65535
         * * flip a coin.
         */
        
        /* equal */
        if (source == dest)
                return USE_DEST;

        /* root server port, 0 - 511 */
        if (ROOT_SERVER(source) && ROOT_SERVER(dest)) {
                if (source < dest)
                        return USE_SOURCE;
                return USE_DEST;
        }

        if (ROOT_SERVER(source) && !ROOT_SERVER(dest))
                return USE_SOURCE;
        if (!ROOT_SERVER(source) && ROOT_SERVER(dest))
                return USE_DEST;

        /* non-root server */
        if (NONROOT_SERVER(source) && NONROOT_SERVER(dest)) {
                if (source < dest)
                        return USE_SOURCE;
                return USE_DEST;
        }
        if (NONROOT_SERVER(source) && !NONROOT_SERVER(dest))
                return USE_SOURCE;
        if (!NONROOT_SERVER(source) && NONROOT_SERVER(dest))
                return USE_DEST;

        /* root client */
        if (ROOT_CLIENT(source) && ROOT_CLIENT(dest)) {
                if (source < dest)
                        return USE_SOURCE;
                return USE_DEST;
        }
        if (ROOT_CLIENT(source) && !ROOT_CLIENT(dest)) {
                /* prefer root-client over nonroot-client */
                if (NONROOT_CLIENT(dest))
                        return USE_SOURCE;
                return USE_DEST;
        }
        if (!ROOT_CLIENT(source) && ROOT_CLIENT(dest)) {
                /* prefer root-client over nonroot-client */
                if (NONROOT_CLIENT(source))
                        return USE_DEST;
                return USE_SOURCE;
        }
        
        /* nonroot client */
        if (NONROOT_CLIENT(source) && NONROOT_CLIENT(dest)) {
                if (source < dest) 
                        return USE_SOURCE;
                return USE_DEST;
        }
        if (NONROOT_CLIENT(source) && !NONROOT_CLIENT(dest))
                return USE_DEST;
        if (!NONROOT_CLIENT(source) && NONROOT_CLIENT(dest))
                return USE_SOURCE;

        /* dynamic range */
        if (DYNAMIC(source) && DYNAMIC(dest))
                if (source < dest)
                        return USE_SOURCE;
                return USE_DEST;
        if (DYNAMIC(source) && !DYNAMIC(dest))
                return USE_DEST;
        if (!DYNAMIC(source) && DYNAMIC(dest))
                return USE_SOURCE;
        /*
        if (SERVER(source) && CLIENT(dest)) 
                return USE_SOURCE;
        
        if (SERVER(dest) && CLIENT(source)) 
                return USE_DEST;
        if (ROOT_SERVER(source) && !ROOT_SERVER(dest)) 
                return USE_SOURCE;
        if (ROOT_SERVER(dest) && !ROOT_SERVER(source)) 
                return USE_DEST;
        */
        /* failing that test... */
        if (source < dest) {
                return USE_SOURCE;
        } 
        return USE_DEST;
        
}

/* Truncate the packet at the suggested length
 * @param packet        the packet opaque pointer
 * @param size          the new length of the packet
 * @returns the new size of the packet
 * @note size and the return size refer to the network-level payload of the
 * packet, and do not include any capture headers. For example, to truncate a
 * packet after the IP header, set size to sizeof(ethernet_header) +
 * sizeof(ip_header)
 * @note If the original network-level payload is smaller than size, then the
 * original size is returned and the packet is left unchanged.
 * @author Daniel Lawson
 */
DLLEXPORT size_t trace_set_capture_length(libtrace_packet_t *packet, size_t size) {
        assert(packet);
        assert(packet->size>0 && packet->size<65536);

        if (packet->trace->format->set_capture_length) {
                int caplen=packet->trace->format->set_capture_length(packet,size);
                if (caplen!=-1) {
                        packet->size=trace_get_framing_length(packet)+caplen;
                }
                return caplen;
        }

        return -1;
}

DLLEXPORT const char * trace_parse_uri(const char *uri, char **format) {
        const char *uridata = 0;
        
        if((uridata = strchr(uri,':')) == NULL) {
                /* badly formed URI - needs a : */
                return 0;
        }

        if ((uridata - uri) > URI_PROTO_LINE) {
                /* badly formed URI - uri type is too long */
                return 0;
        }

        *format=xstrndup(uri, (uridata - uri));

        /* push uridata past the delimiter */
        uridata++;
        
        return uridata;
}

enum base_format_t trace_get_format(libtrace_packet_t *packet) 
{
        assert(packet);

        return packet->trace->format->type;
}
        
DLLEXPORT libtrace_err_t trace_get_err(libtrace_t *trace)
{
        libtrace_err_t err = trace->err;
        trace->err.err_num = 0; /* "OK" */
        trace->err.problem[0]='\0';
        return err;
}

DLLEXPORT bool trace_is_err(libtrace_t *trace)
{
        return trace->err.err_num != 0;
}

DLLEXPORT void trace_perror(libtrace_t *trace,const char *msg,...)
{
        char buf[256];
        va_list va;
        va_start(va,msg);
        vsnprintf(buf,sizeof(buf),msg,va);
        va_end(va);
        if(trace->err.err_num) {
                fprintf(stderr,"%s(%s): %s\n",
                                buf,trace->uridata,trace->err.problem);
        } else {
                fprintf(stderr,"%s(%s): No error\n",
                                buf,trace->uridata);
        }
        trace->err.err_num = 0; /* "OK" */
        trace->err.problem[0]='\0';
}

DLLEXPORT libtrace_err_t trace_get_err_output(libtrace_out_t *trace)
{
        libtrace_err_t err = trace->err;
        trace->err.err_num = TRACE_ERR_NOERROR; /* "OK" */
        trace->err.problem[0]='\0';
        return err;
}

DLLEXPORT bool trace_is_err_output(libtrace_out_t *trace)
{
        return trace->err.err_num != 0;
}

DLLEXPORT void trace_perror_output(libtrace_out_t *trace,const char *msg,...)
{
        char buf[256];
        va_list va;
        va_start(va,msg);
        vsnprintf(buf,sizeof(buf),msg,va);
        va_end(va);
        if(trace->err.err_num) {
                fprintf(stderr,"%s(%s): %s\n",
                                buf,trace->uridata,trace->err.problem);
        } else {
                fprintf(stderr,"%s(%s): No error\n",buf,trace->uridata);
        }
}

DLLEXPORT int trace_seek_erf_timestamp(libtrace_t *trace, uint64_t ts)
{
        if (trace->format->seek_erf) {
                return trace->format->seek_erf(trace,ts);
        }
        else {
                if (trace->format->seek_timeval) {
                        struct timeval tv;
#if __BYTE_ORDER == __BIG_ENDIAN
                        tv.tv_sec = ts & 0xFFFFFFFF;
#elif __BYTE_ORDER == __LITTLE_ENDIAN
                        tv.tv_sec = ts >> 32;
#else
#error "What on earth are you running this on?"
#endif
                        tv.tv_usec = ((ts&0xFFFFFFFF)*1000000)>>32;
                        if (tv.tv_usec >= 1000000) {
                                tv.tv_usec -= 1000000;
                                tv.tv_sec += 1;
                        }
                        return trace->format->seek_timeval(trace,tv);
                }
                if (trace->format->seek_seconds) {
                        double seconds =  
                                (ts>>32) + ((ts & UINT_MAX)*1.0 / UINT_MAX);
                        return trace->format->seek_seconds(trace,seconds);
                }
                trace_set_err(trace,
                                TRACE_ERR_OPTION_UNAVAIL,
                                "Feature unimplemented");
                return -1;
        }
}

DLLEXPORT int trace_seek_seconds(libtrace_t *trace, double seconds)
{
        if (trace->format->seek_seconds) {
                return trace->format->seek_seconds(trace,seconds);
        }
        else {
                if (trace->format->seek_timeval) {
                        struct timeval tv;
                        tv.tv_sec = (uint32_t)seconds;
                        tv.tv_usec = (uint32_t)(((seconds - tv.tv_sec) * 1000000)/UINT_MAX);
                        return trace->format->seek_timeval(trace,tv);
                }
                if (trace->format->seek_erf) {
                        uint64_t timestamp = 
                                ((uint64_t)((uint32_t)seconds) << 32) + \
                            (uint64_t)(( seconds - (uint32_t)seconds   ) * UINT_MAX);
                        return trace->format->seek_erf(trace,timestamp);
                }
                trace_set_err(trace,
                                TRACE_ERR_OPTION_UNAVAIL,
                                "Feature unimplemented");
                return -1;
        }
}

DLLEXPORT int trace_seek_timeval(libtrace_t *trace, struct timeval tv)
{
        if (trace->format->seek_timeval) {
                return trace->format->seek_timeval(trace,tv);
        }
        else {
                if (trace->format->seek_erf) {
                        uint64_t timestamp = ((((uint64_t)tv.tv_sec) << 32) + \
                                (((uint64_t)tv.tv_usec * UINT_MAX)/1000000));
                        return trace->format->seek_erf(trace,timestamp);
                }
                if (trace->format->seek_seconds) {
                        double seconds = tv.tv_sec + ((tv.tv_usec * 1.0)/1000000);
                        return trace->format->seek_seconds(trace,seconds);
                }
                trace_set_err(trace,
                                TRACE_ERR_OPTION_UNAVAIL,
                                "Feature unimplemented");
                return -1;
        }
}

DLLEXPORT char *trace_ether_ntoa(const uint8_t *addr, char *buf)
{
        char *buf2 = buf;
        char staticbuf[18]={0,};
        if (!buf2)
                buf2=staticbuf;
        snprintf(buf2,18,"%02x:%02x:%02x:%02x:%02x:%02x",
                        addr[0],addr[1],addr[2],
                        addr[3],addr[4],addr[5]);
        return buf2;
}

DLLEXPORT uint8_t *trace_ether_aton(const char *buf, uint8_t *addr)
{
        uint8_t *buf2 = addr;
        unsigned int tmp[6];
        static uint8_t staticaddr[6];
        if (!buf2)
                buf2=staticaddr;
        sscanf(buf,"%x:%x:%x:%x:%x:%x",
                        &tmp[0],&tmp[1],&tmp[2],
                        &tmp[3],&tmp[4],&tmp[5]);
        buf2[0]=tmp[0]; buf2[1]=tmp[1]; buf2[2]=tmp[2];
        buf2[3]=tmp[3]; buf2[4]=tmp[4]; buf2[5]=tmp[5];
        return buf2;
}