source: lib/format_pcap.c @ b359a11

/*
 *
 * 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>

#ifdef HAVE_PCAP_H
#  include <pcap.h>
#  ifdef HAVE_PCAP_INT_H
#    include <pcap-int.h>
#  endif
#endif

/* This format module deals with traces captured using the PCAP library. This
 * format module handles both captures from a live interface and from PCAP
 * files.
 *
 * However, the PCAP file support featured in this code is superceded by our 
 * own implementation of the PCAP file format, called pcapfile. See 
 * format_pcapfile.c for more information.
 *
 * Both the live and trace formats support writing, provided your PCAP library
 * also supports it.
 *
 */

/* Formats implemented in this module:
 *      pcap - deals with PCAP trace files
 *      pcapint - deals with live PCAP interfaces
 */

#ifdef HAVE_LIBPCAP
static struct libtrace_format_t pcap;
static struct libtrace_format_t pcapint;

#define DATA(x) ((struct pcap_format_data_t*)((x)->format_data))
#define DATAOUT(x) ((struct pcap_format_data_out_t*)((x)->format_data))

#define INPUT DATA(libtrace)->input
#define OUTPUT DATAOUT(libtrace)->output
struct pcap_format_data_t {
        /** Information about the current state of the input trace */
        union {
                /* The PCAP input source */
                pcap_t *pcap;
        } input;
        /* A filter to be applied to all packets read from the source */
        libtrace_filter_t *filter;
        /* The snap length to be applied to all captured packets (live only) */
        int snaplen;
        /* Whether the capture interface should be set to promiscuous mode
         * (live only) */
        int promisc;
};

struct pcap_format_data_out_t {
        /* Information about the current state of the output trace */
        union {
                struct {
                        /* The PCAP output device or trace */
                        pcap_t *pcap;   
                        /* The PCAP dumper */
                        pcap_dumper_t *dump;
                } trace;

        } output;
};

static int pcap_init_input(libtrace_t *libtrace) {
        libtrace->format_data = malloc(sizeof(struct pcap_format_data_t));

        if (!libtrace->format_data) {
                trace_set_err(libtrace, TRACE_ERR_INIT_FAILED, "Unable to allocate memory for "
                        "format data inside pcap_init_input()");
                return -1;
        }

        INPUT.pcap = NULL;
        DATA(libtrace)->filter = NULL;
        DATA(libtrace)->snaplen = LIBTRACE_PACKET_BUFSIZE;
        DATA(libtrace)->promisc = 0;

        return 0;
}

static int pcap_start_input(libtrace_t *libtrace) {
        char errbuf[PCAP_ERRBUF_SIZE];


        /* Check if the file is already open */
        if (INPUT.pcap)
                return 0; /* success */

        /* Open the trace file for reading */
        if ((INPUT.pcap = 
                pcap_open_offline(libtrace->uridata,
                        errbuf)) == NULL) {
                trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",
                                errbuf);
                return -1;
        }

        /* If a filter has been configured, compile and apply it */
#ifdef HAVE_BPF
        if (DATA(libtrace)->filter) {
                if (DATA(libtrace)->filter->flag == 0) {
                        pcap_compile(INPUT.pcap, 
                                        &DATA(libtrace)->filter->filter,
                                        DATA(libtrace)->filter->filterstring, 
                                        1, 0);
                        DATA(libtrace)->filter->flag = 1;
                }
                if (pcap_setfilter(INPUT.pcap,&DATA(libtrace)->filter->filter) 
                                == -1) {
                        trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",
                                        pcap_geterr(INPUT.pcap));
                        return -1;
                }
        }
#endif
        return 0;
}

static int pcap_config_input(libtrace_t *libtrace,
                trace_option_t option,
                void *data)
{
        switch(option) {
                case TRACE_OPTION_FILTER:
#ifdef HAVE_BPF
                        DATA(libtrace)->filter=data;
                        return 0;
#else
                        return -1;
#endif
                case TRACE_OPTION_SNAPLEN:
                        /* Snapping isn't supported directly, so fall thru
                         * and let libtrace deal with it
                         */
                case TRACE_OPTION_PROMISC:
                        /* Can't do promisc on a trace! */
                case TRACE_OPTION_META_FREQ:
                        /* No meta data for this format */
                case TRACE_OPTION_EVENT_REALTIME:
                        /* We do not support this option for PCAP traces */
                default:
                        return -1;
        }
        return -1;
}

static int pcap_init_output(libtrace_out_t *libtrace) {
        libtrace->format_data = malloc(sizeof(struct pcap_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 pcap_init_output()");
                return -1;
        }

        OUTPUT.trace.pcap = NULL;
        OUTPUT.trace.dump = NULL;
        return 0;
}

static int pcapint_init_output(libtrace_out_t *libtrace) {
#ifdef HAVE_PCAP_INJECT
        libtrace->format_data = malloc(sizeof(struct pcap_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 pcapint_init_output()");
                return -1;
        }

        OUTPUT.trace.pcap = NULL;
        OUTPUT.trace.dump = NULL;
        return 0;
#else
#ifdef HAVE_PCAP_SENDPACKET
        libtrace->format_data = malloc(sizeof(struct pcap_format_data_out_t));
        OUTPUT.trace.pcap = NULL;
        OUTPUT.trace.dump = NULL;
        return 0;
#else
        trace_set_err_out(libtrace,TRACE_ERR_UNSUPPORTED,
                        "writing not supported by this version of pcap");
        return -1;
#endif
#endif
}

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

        DATA(libtrace)->filter = NULL;
        DATA(libtrace)->snaplen = LIBTRACE_PACKET_BUFSIZE;
        DATA(libtrace)->promisc = 0;
        return 0; /* success */
}

static int pcapint_config_input(libtrace_t *libtrace,
                trace_option_t option,
                void *data)
{
        switch(option) {
                case TRACE_OPTION_FILTER:
#ifdef HAVE_BPF
                        DATA(libtrace)->filter=(libtrace_filter_t*)data;
                        return 0;
#else
                        return -1;
#endif
                case TRACE_OPTION_SNAPLEN:
                        DATA(libtrace)->snaplen=*(int*)data;
                        return 0;
                case TRACE_OPTION_PROMISC:
                        DATA(libtrace)->promisc=*(int*)data;
                        return 0;
                case TRACE_OPTION_META_FREQ:
                        /* No meta-data for this format */
                case TRACE_OPTION_EVENT_REALTIME:
                        /* live interface is always real-time! */
                default:
                        /* Don't set an error here - trace_config will try
                         * to handle the option when we return. If it can't
                         * deal with it, then it will do the necessary
                         * error-setting. */
                        return -1;
        }
        return -1;
}

static int pcapint_start_input(libtrace_t *libtrace) {
        char errbuf[PCAP_ERRBUF_SIZE];

#ifdef HAVE_PCAP_CREATE
        int ret = 0;
        
        if ((INPUT.pcap = pcap_create(libtrace->uridata, errbuf)) == NULL) {
                trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",errbuf);
                return -1; /* failure */
        }
        if ((pcap_set_snaplen(INPUT.pcap, DATA(libtrace)->snaplen) == 
                                PCAP_ERROR_ACTIVATED)) {
                trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",errbuf);
                return -1; /* failure */
        }

        if ((pcap_set_promisc(INPUT.pcap, DATA(libtrace)->promisc) == 
                                PCAP_ERROR_ACTIVATED)) {
                trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",errbuf);
                return -1; /* failure */
        }
        
        if ((pcap_set_timeout(INPUT.pcap, 1) == PCAP_ERROR_ACTIVATED)) {
                trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",errbuf);
                return -1; /* failure */
        }

#ifdef HAVE_PCAP_IMMEDIATE
        if ((pcap_set_immediate_mode(INPUT.pcap, 1) == PCAP_ERROR_ACTIVATED)) {
                trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",errbuf);
                return -1; /* failure */
        }
#endif

        if ((ret = pcap_activate(INPUT.pcap)) != 0) {
                if (ret == PCAP_WARNING_PROMISC_NOTSUP) {
                        trace_set_err(libtrace, TRACE_ERR_INIT_FAILED,"Promiscuous mode unsupported");
                        return -1;
                }
                if (ret == PCAP_WARNING) {
                        pcap_perror(INPUT.pcap, "Pcap Warning:");
                } else {
                        trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",
                                        pcap_geterr(INPUT.pcap));
                        return -1;
                }
        }
                         
#else   

        /* Open the live device */
        if ((INPUT.pcap = 
                        pcap_open_live(libtrace->uridata,
                        DATA(libtrace)->snaplen,
                        DATA(libtrace)->promisc,
                        1,
                        errbuf)) == NULL) {
                trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",errbuf);
                return -1; /* failure */
        }
#endif
#ifdef HAVE_PCAP_SETNONBLOCK
        pcap_setnonblock(INPUT.pcap,0,errbuf);
#endif
        /* Set a filter if one is defined */
#ifdef HAVE_BPF
        if (DATA(libtrace)->filter) {
                struct pcap_pkthdr *pcap_hdr = NULL;
                u_char *pcap_payload = NULL;
                int pcapret;
                
                if (DATA(libtrace)->filter->flag == 0) {
                        pcap_compile(INPUT.pcap, 
                                        &DATA(libtrace)->filter->filter,
                                        DATA(libtrace)->filter->filterstring, 
                                        1, 0);
                        DATA(libtrace)->filter->flag = 1;
                }
                if (pcap_setfilter(INPUT.pcap,&DATA(libtrace)->filter->filter)
                        == -1) {
                        trace_set_err(libtrace,TRACE_ERR_INIT_FAILED,"%s",
                                        pcap_geterr(INPUT.pcap));
                        return -1; /* failure */
                }

                /* Consume the first packet in the queue, as this may not
                 * have had the filter applied to it.
                 *
                 * Otherwise we can get problems with the event API, where
                 * select tells us that there is a packet available but
                 * calling trace_read_packet will block forever because the
                 * packet in the queue didn't match the filter so
                 * pcap_next_ex returns "timed out".
                 *
                 * This does mean we may consume a legitimate packet, but
                 * that's a pretty small downside compared with trace_event
                 * getting stuck in an infinite loop because of pcap
                 * wackiness. 
                 *
                 * For some reason, we only need to consume one packet for
                 * this to work, so let's hope that holds in the future.
                 */
                do {
                        pcapret = pcap_next_ex(INPUT.pcap, &pcap_hdr, 
                                (const u_char **)&pcap_payload);
                } while (0);

                if (pcapret < 0)
                        return -1;
        }
#endif
        return 0; /* success */
}

static int pcap_pause_input(libtrace_t *libtrace UNUSED)
{
        return 0; /* success */
}


static int pcap_fin_input(libtrace_t *libtrace) 
{
        pcap_close(INPUT.pcap);
        INPUT.pcap=NULL;
        free(libtrace->format_data);
        return 0; /* success */
}

static int pcap_fin_output(libtrace_out_t *libtrace) 
{
        if (OUTPUT.trace.dump) {
                pcap_dump_flush(OUTPUT.trace.dump);
                pcap_dump_close(OUTPUT.trace.dump);
        }
        if (OUTPUT.trace.pcap) {
                pcap_close(OUTPUT.trace.pcap);
        }
        free(libtrace->format_data);
        return 0;
}

static int pcapint_fin_output(libtrace_out_t *libtrace)
{
        pcap_close(OUTPUT.trace.pcap);
        free(libtrace->format_data);
        return 0;
}

static int pcap_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->type = rt_type;

        /* Assuming header and payload are sequential in the buffer - 
         * regular pcap often doesn't work like this though, so hopefully
         * we're not called by something that is reading genuine pcap! */
        packet->payload = (char *)packet->header + sizeof(struct pcap_pkthdr);

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

static int pcap_read_packet(libtrace_t *libtrace, libtrace_packet_t *packet) {
        int ret = 0;
        int linktype;
        uint32_t flags = 0;

        if (!libtrace->format_data) {
                trace_set_err(libtrace, TRACE_ERR_BAD_FORMAT, "Trace format data missing, "
                        "call trace_create() before calling pcap_read_packet()");
                return -1;
        }
        linktype = pcap_datalink(DATA(libtrace)->input.pcap);
        packet->type = pcap_linktype_to_rt(linktype);

        /* If we're using the replacement pcap_next_ex() we need to
         * make sure we have a buffer to *shudder* memcpy into 
         */
        if (!packet->buffer) {
                packet->buffer = malloc(LIBTRACE_PACKET_BUFSIZE);
                if (!packet->buffer) {
                        trace_set_err(libtrace, errno, 
                                        "Cannot allocate memory");
                        return -1;
                }
                packet->header = packet->buffer;
                packet->payload = (char *)packet->buffer+sizeof(struct pcap_pkthdr);
                        
        }

        flags |= TRACE_PREP_OWN_BUFFER;
        
        for(;;) {
                
                struct pcap_pkthdr *pcap_hdr = NULL;
                u_char *pcap_payload = NULL;

                ret = pcap_next_ex(INPUT.pcap, &pcap_hdr, 
                                (const u_char **)&pcap_payload);
                
                packet->header = pcap_hdr;
                packet->payload = pcap_payload;

                switch(ret) {
                        case 1: break; /* no error */
                        case 0: 
                                if ((ret=is_halted(libtrace)) != -1)
                                        return ret;
                                continue; /* timeout expired */
                        case -1: 
                                trace_set_err(libtrace,TRACE_ERR_BAD_PACKET,
                                                "%s",pcap_geterr(INPUT.pcap));
                                return -1; /* Error */
                        case -2:
                                return 0; /* EOF */
                }

                /*
                 * pcap is nasty in that the header and payload aren't 
                 * necessarily located sequentially in memory, but most
                 * sensible uses of pcap_prepare_packet will involve a
                 * buffer where header and payload are sequential. 
                 *
                 * Basically, don't call pcap_prepare_packet here! 
                 *
                if (pcap_prepare_packet(libtrace, packet, packet->buffer,
                                packet->type, flags)) {
                        return -1;
                }
                */
                return ((struct pcap_pkthdr*)packet->header)->len
                        +sizeof(struct pcap_pkthdr);
        }
}

static int pcap_write_packet(libtrace_out_t *libtrace, 
                libtrace_packet_t *packet) 
{

        if (!libtrace) {
                fprintf(stderr, "NULL trace passed into pcap_write_packet()\n");
                return TRACE_ERR_NULL_TRACE;
        }
        if (!packet) {
                trace_set_err_out(libtrace, TRACE_ERR_NULL_PACKET, "NULL packet passed into pcap_write_packet()\n");
                return -1;
        }

        struct pcap_pkthdr pcap_pkt_hdr;
        void *link;
        libtrace_linktype_t linktype;
        uint32_t remaining;

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

        /* Silently discard RT metadata packets and packets with an
         * unknown linktype. */
        if (linktype == TRACE_TYPE_NONDATA || linktype == TRACE_TYPE_UNKNOWN || linktype == TRACE_TYPE_ERF_META || linktype == TRACE_TYPE_CONTENT_INVALID) {
                return 0;
        }

        /* We may have to convert this packet into a suitable PCAP packet */

        /* 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(libtrace, 
                                TRACE_ERR_NO_CONVERSION,
                                "pcap does not support this format");
                        return -1;
                }

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


        if (!OUTPUT.trace.pcap) {
                int linktype=libtrace_to_pcap_dlt(trace_get_link_type(packet));
                OUTPUT.trace.pcap = pcap_open_dead(linktype,65536);
                if (!OUTPUT.trace.pcap) {
                        trace_set_err_out(libtrace,TRACE_ERR_INIT_FAILED,
                                        "Failed to open dead trace: %s\n",
                                        pcap_geterr(OUTPUT.trace.pcap));
                }
                OUTPUT.trace.dump = pcap_dump_open(OUTPUT.trace.pcap,
                                libtrace->uridata);
                if (!OUTPUT.trace.dump) {
                        char *errmsg = pcap_geterr(OUTPUT.trace.pcap);
                        trace_set_err_out(libtrace,TRACE_ERR_INIT_FAILED,"Failed to open output file: %s\n",
                                        errmsg ? errmsg : "Unknown error");
                        return -1;
                }
        }

        /* Corrupt packet, or other "non data" packet, so skip it */
        if (link == NULL) {
                /* Return "success", but nothing written */
                return 0;
        }

        /* Check if the packet was captured using one of the PCAP formats */
        if (packet->trace->format == &pcap || 
                        packet->trace->format == &pcapint) {
                /* Yes - this means we can write it straight out */
                pcap_dump((u_char*)OUTPUT.trace.dump,
                                (struct pcap_pkthdr *)packet->header,
                                packet->payload);
        } else {
                /* No - need to fill in a PCAP header with the appropriate
                 * values */

                /* Leave the manual copy as it is, as it gets around 
                 * some OS's having different structures in pcap_pkt_hdr
                 */
                struct timeval ts = trace_get_timeval(packet);
                pcap_pkt_hdr.ts.tv_sec = ts.tv_sec;
                pcap_pkt_hdr.ts.tv_usec = ts.tv_usec;
                pcap_pkt_hdr.caplen = remaining;
                /* trace_get_wire_length includes FCS, while pcap doesn't */
                if (trace_get_link_type(packet)==TRACE_TYPE_ETH)
                        if (trace_get_wire_length(packet) >= 4) { 
                                pcap_pkt_hdr.len = 
                                        trace_get_wire_length(packet)-4;
                        }
                        else {
                                pcap_pkt_hdr.len = 0;
                        }
                else
                        pcap_pkt_hdr.len = trace_get_wire_length(packet);

                if (pcap_pkt_hdr.caplen >= 65536) {
                        trace_set_err_out(libtrace, TRACE_ERR_BAD_HEADER, "Header capture length is larger than it should be in pcap_write_packet()");
                        return -1;
                }
                if (pcap_pkt_hdr.len >= 65536) {
                        trace_set_err_out(libtrace, TRACE_ERR_BAD_HEADER, "Header wire length is larger than it should be pcap_write_packet()");
                        return -1;
                }

                pcap_dump((u_char*)OUTPUT.trace.dump, &pcap_pkt_hdr, packet->payload);
        }
        return remaining;
}

static int pcap_flush_output(libtrace_out_t *libtrace) {
        return pcap_dump_flush(OUTPUT.trace.dump);
}

static int pcapint_write_packet(libtrace_out_t *libtrace,
                libtrace_packet_t *packet) 
{
        int err;
        libtrace_linktype_t linktype = trace_get_link_type(packet);

        /* Silently discard RT metadata packets and packets with an
         * unknown linktype. */
        if (linktype == TRACE_TYPE_NONDATA || linktype == TRACE_TYPE_UNKNOWN || linktype == TRACE_TYPE_ERF_META || linktype == TRACE_TYPE_CONTENT_INVALID) {
                return 0;
        }

        if (!OUTPUT.trace.pcap) {
                OUTPUT.trace.pcap = (pcap_t *)pcap_open_live(
                        libtrace->uridata,65536,0,0,NULL);
        }
#ifdef HAVE_PCAP_INJECT
        err=pcap_inject(OUTPUT.trace.pcap,
                        packet->payload,
                        trace_get_capture_length(packet));
        if (err!=(int)trace_get_capture_length(packet))
                err=-1;
#else 
#ifdef HAVE_PCAP_SENDPACKET
        err=pcap_sendpacket(OUTPUT.trace.pcap,
                        packet->payload,
                        trace_get_capture_length(packet));
#else
    trace_set_err(packet->trace,TRACE_ERR_UNSUPPORTED,"writing is not supported on this platform");
        return -1;
#endif
#endif
        return err;
}

static libtrace_linktype_t pcap_get_link_type(const libtrace_packet_t *packet) {
        /* PCAP doesn't store linktype in the framing header so we need
         * RT to do it for us 
         */
        int linktype = rt_to_pcap_linktype(packet->type);
        return pcap_linktype_to_libtrace(linktype);
}

static libtrace_direction_t pcap_set_direction(libtrace_packet_t *packet,
                libtrace_direction_t dir) {

        /* We only support tagging with IN or OUT return error for any others */
        if(!(dir == TRACE_DIR_OUTGOING || dir == TRACE_DIR_INCOMING))
                return -1;

        /* PCAP doesn't have a direction field in the header, so we need to
         * promote to Linux SLL to tag it properly */
        libtrace_sll_header_t *sll;
        promote_packet(packet);
        sll=packet->payload;
        
        /* sll->pkttype should be in the endianness of the host that the
         * trace was taken on.  This is impossible to achieve so we assume 
         * host endianness
         */
        if(dir==TRACE_DIR_OUTGOING)
                sll->pkttype=TRACE_SLL_OUTGOING;
        else
                sll->pkttype=TRACE_SLL_HOST;
        return dir;
}

static libtrace_direction_t pcapint_get_direction(const libtrace_packet_t *packet) {
        /* This function is defined in format_helper.c */
        return pcap_get_direction(packet);
}


static struct timeval pcap_get_timeval(const libtrace_packet_t *packet) {
        struct pcap_pkthdr *pcapptr = (struct pcap_pkthdr *)packet->header;
        struct timeval ts;
        ts.tv_sec = pcapptr->ts.tv_sec;
        ts.tv_usec = pcapptr->ts.tv_usec;
        return ts;
}


static int pcap_get_capture_length(const libtrace_packet_t *packet) {
        if (!packet) {
                fprintf(stderr, "NULL packet passed into pcapng_get_capture_length()\n");
                return TRACE_ERR_NULL_PACKET;
        }
        struct pcap_pkthdr *pcapptr = 0;
        pcapptr = (struct pcap_pkthdr *)packet->header;
        if (pcapptr->caplen > 65536) {
                trace_set_err(packet->trace, TRACE_ERR_BAD_PACKET, "Capture length is to large, Packet may be corrupt in pcap_get_capture_length()");
                return -1;
        }

        return pcapptr->caplen;
}

static int pcap_get_wire_length(const libtrace_packet_t *packet) {
        struct pcap_pkthdr *pcapptr = 0;
        pcapptr = (struct pcap_pkthdr *)packet->header;
        if (packet->type==pcap_linktype_to_rt(TRACE_DLT_EN10MB))
                return pcapptr->len+4; /* Include the missing FCS */
        else if (packet->type==pcap_linktype_to_rt(TRACE_DLT_IEEE802_11_RADIO)) {
                libtrace_linktype_t linktype;
                void *link = trace_get_packet_buffer(packet,&linktype,NULL);
                /* 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;
                trace_get_wireless_flags(link, 
                                linktype, &flags);
                if ((flags & TRACE_RADIOTAP_F_FCS) == 0)
                        return pcapptr->len + 4;
        }
        return pcapptr->len;
}

static int pcap_get_framing_length(UNUSED const libtrace_packet_t *packet) {
        return sizeof(struct pcap_pkthdr);
}

static size_t pcap_set_capture_length(libtrace_packet_t *packet,size_t size) {
        struct pcap_pkthdr *pcapptr = 0;
        if (!packet) {
                fprintf(stderr, "NULL packet passed to pcap_set_capture_length()\n");
                return TRACE_ERR_NULL_PACKET;
        }
        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 = (struct pcap_pkthdr *)packet->header;
        pcapptr->caplen = size;
        return trace_get_capture_length(packet);
}

static int pcap_get_fd(const libtrace_t *trace) {
        if (!trace) {
                fprintf(stderr, "NULL trace passed to pcap_get_fd()\n");
                return TRACE_ERR_NULL_TRACE;
        }
        if (!trace->format_data) {
                /* cant do this because trace is a const? */
                /*trace_set_err(trace, TRACE_ERR_BAD_FORMAT, "Trace format data missing, call init_input() before calling pcap_get_fd()");*/
                fprintf(stderr, "Trace format data missing, call init_input() before calling pcap_get_fd()\n");
                return TRACE_ERR_BAD_FORMAT;
        }
        return pcap_fileno(DATA(trace)->input.pcap);
}

static void pcap_get_statistics(libtrace_t *trace, libtrace_stat_t *stat) {

        struct pcap_stat pcapstats;
        if (pcap_stats(DATA(trace)->input.pcap,&pcapstats)==-1) {
                char *errmsg = pcap_geterr(DATA(trace)->input.pcap);
                trace_set_err(trace,TRACE_ERR_UNSUPPORTED,
                                "Failed to retrieve stats: %s\n",
                                errmsg ? errmsg : "Unknown pcap error");
                return;
        }

        stat->received_valid = 1;
        stat->received = pcapstats.ps_recv;
        stat->dropped_valid = 1;
        stat->dropped = pcapstats.ps_drop;
}

static void pcap_help(void) {
        printf("pcap format module: $Revision: 1729 $\n");
        printf("Supported input URIs:\n");
        printf("\tpcap:/path/to/file\n");
        printf("\n");
        printf("\te.g.: pcap:/tmp/trace.pcap\n");
        printf("\n");
        printf("Supported output URIs:\n");
        printf("\tnone\n");
        printf("\n");
}

static void pcapint_help(void) {
        printf("pcapint format module: $Revision: 1729 $\n");
        printf("Supported input URIs:\n");
        printf("\tpcapint:interface\n");
        printf("\n");
        printf("\te.g.: pcapint:eth0\n");
        printf("\n");
        printf("Supported output URIs:\n");
        printf("\tnone\n");
        printf("\n");
}


static struct libtrace_format_t pcap = {
        "pcap",
        "$Id$",
        TRACE_FORMAT_PCAP,
        NULL,                           /* probe filename */
        NULL,                           /* probe magic */
        pcap_init_input,                /* init_input */
        pcap_config_input,              /* config_input */
        pcap_start_input,               /* start_input */
        pcap_pause_input,               /* pause_input */
        pcap_init_output,               /* init_output */
        NULL,                           /* config_output */
        NULL,                           /* start_output */
        pcap_fin_input,                 /* fin_input */
        pcap_fin_output,                /* fin_output */
        pcap_read_packet,               /* read_packet */
        pcap_prepare_packet,            /* prepare_packet */
        NULL,                           /* fin_packet */
        pcap_write_packet,              /* write_packet */
        pcap_flush_output,              /* flush_output */
        pcap_get_link_type,             /* get_link_type */
        pcapint_get_direction,          /* get_direction */
        pcap_set_direction,             /* set_direction */
        NULL,                           /* get_erf_timestamp */
        pcap_get_timeval,               /* get_timeval */
        NULL,                           /* get_seconds */
        NULL,                           /* get_timespec */
        NULL,                           /* seek_erf */
        NULL,                           /* seek_timeval */
        NULL,                           /* seek_seconds */
        pcap_get_capture_length,        /* get_capture_length */
        pcap_get_wire_length,           /* get_wire_length */
        pcap_get_framing_length,        /* get_framing_length */
        pcap_set_capture_length,        /* set_capture_length */
        NULL,                           /* get_received_packets */
        NULL,                           /* get_filtered_packets */
        NULL,                           /* get_dropped_packets */
        NULL,                           /* get_statistics */
        NULL,                           /* get_fd */
        trace_event_trace,              /* trace_event */
        pcap_help,                      /* help */
        NULL,                   /* next pointer */
        NON_PARALLEL(false)
};

static struct libtrace_format_t pcapint = {
        "pcapint",
        "$Id$",
        TRACE_FORMAT_PCAP,
        NULL,                           /* probe filename */
        NULL,                           /* probe magic */
        pcapint_init_input,             /* init_input */
        pcapint_config_input,           /* config_input */
        pcapint_start_input,            /* start_input */
        pcap_pause_input,               /* pause_input */
        pcapint_init_output,            /* init_output */
        NULL,                           /* config_output */
        NULL,                           /* start_output */
        pcap_fin_input,                 /* fin_input */
        pcapint_fin_output,             /* fin_output */
        pcap_read_packet,               /* read_packet */
        pcap_prepare_packet,            /* prepare_packet */
        NULL,                           /* fin_packet */
        pcapint_write_packet,           /* write_packet */
        NULL,                           /* flush_output */
        pcap_get_link_type,             /* get_link_type */
        pcapint_get_direction,          /* get_direction */
        pcap_set_direction,             /* set_direction */
        NULL,                           /* get_erf_timestamp */
        pcap_get_timeval,               /* get_timeval */
        NULL,                           /* get_seconds */
        NULL,                           /* get_timespec */
        NULL,                           /* seek_erf */
        NULL,                           /* seek_timeval */
        NULL,                           /* seek_seconds */
        pcap_get_capture_length,        /* get_capture_length */
        pcap_get_wire_length,           /* get_wire_length */
        pcap_get_framing_length,        /* get_framing_length */
        pcap_set_capture_length,        /* set_capture_length */
        NULL,                           /* get_received_packets */
        NULL,                           /* get_filtered_packets */
        NULL,                           /* get_dropped_packets */
        pcap_get_statistics,            /* get_statistics */
        pcap_get_fd,                    /* get_fd */
        trace_event_device,             /* trace_event */
        pcapint_help,                   /* help */
        NULL,                   /* next pointer */
        NON_PARALLEL(true)
};

void pcap_constructor(void) {
        register_format(&pcap);
        register_format(&pcapint);
}


#endif