[libpcap] / pcap-dag.c

/*
 * pcap-dag.c: Packet capture interface for Endace DAG card.
 *
 * The functionality of this code attempts to mimic that of pcap-linux as much
 * as possible.  This code is compiled in several different ways depending on
 * whether DAG_ONLY and HAVE_DAG_API are defined.  If HAVE_DAG_API is not
 * defined it should not get compiled in, otherwise if DAG_ONLY is defined then
 * the 'dag_' function calls are renamed to 'pcap_' equivalents.  If DAG_ONLY
 * is not defined then nothing is altered - the dag_ functions will be
 * called as required from their pcap-linux/bpf equivalents.
 *
 * Authors: Richard Littin, Sean Irvine ({richard,sean}@reeltwo.com)
 * Modifications: Jesper Peterson  <support@endace.com>
 *                Koryn Grant      <support@endace.com>
 *                Stephen Donnelly <support@endace.com>
 */

#ifndef lint
static const char rcsid[] _U_ =
        "@(#) $Header: /tcpdump/master/libpcap/pcap-dag.c,v 1.32 2007-10-30 10:16:45 guy Exp $ (LBL)";
#endif

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

#include <sys/param.h>                  /* optionally get BSD define */

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

#include "pcap-int.h"

#include <ctype.h>
#include <netinet/in.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

struct mbuf;            /* Squelch compiler warnings on some platforms for */
struct rtentry;         /* declarations in <net/if.h> */
#include <net/if.h>

#include "dagnew.h"
#include "dagapi.h"

#define ATM_CELL_SIZE           52
#define ATM_HDR_SIZE            4

/*
 * A header containing additional MTP information.
 */
#define MTP2_SENT_OFFSET                0       /* 1 byte */
#define MTP2_ANNEX_A_USED_OFFSET        1       /* 1 byte */
#define MTP2_LINK_NUMBER_OFFSET         2       /* 2 bytes */
#define MTP2_HDR_LEN                    4       /* length of the header */

#define MTP2_ANNEX_A_NOT_USED      0
#define MTP2_ANNEX_A_USED          1
#define MTP2_ANNEX_A_USED_UNKNOWN  2

/* SunATM pseudo header */
struct sunatm_hdr {
        unsigned char   flags;          /* destination and traffic type */
        unsigned char   vpi;            /* VPI */
        unsigned short  vci;            /* VCI */
};

typedef struct pcap_dag_node {
        struct pcap_dag_node *next;
        pcap_t *p;
        pid_t pid;
} pcap_dag_node_t;

static pcap_dag_node_t *pcap_dags = NULL;
static int atexit_handler_installed = 0;
static const unsigned short endian_test_word = 0x0100;

#define IS_BIGENDIAN() (*((unsigned char *)&endian_test_word))


#ifdef DAG_ONLY
/* This code is required when compiling for a DAG device only. */
#include "pcap-dag.h"

/* Replace dag function names with pcap equivalent. */
#define dag_open_live pcap_open_live
#define dag_platform_finddevs pcap_platform_finddevs
#endif /* DAG_ONLY */

#define MAX_DAG_PACKET 65536

static unsigned char TempPkt[MAX_DAG_PACKET];

static int dag_setfilter(pcap_t *p, struct bpf_program *fp);
static int dag_stats(pcap_t *p, struct pcap_stat *ps);
static int dag_set_datalink(pcap_t *p, int dlt);
static int dag_get_datalink(pcap_t *p);
static int dag_setnonblock(pcap_t *p, int nonblock, char *errbuf);

static void
delete_pcap_dag(pcap_t *p)
{
        pcap_dag_node_t *curr = NULL, *prev = NULL;

        for (prev = NULL, curr = pcap_dags; curr != NULL && curr->p != p; prev = curr, curr = curr->next) {
                /* empty */
        }

        if (curr != NULL && curr->p == p) {
                if (prev != NULL) {
                        prev->next = curr->next;
                } else {
                        pcap_dags = curr->next;
                }
        }
}

/*
 * Performs a graceful shutdown of the DAG card, frees dynamic memory held
 * in the pcap_t structure, and closes the file descriptor for the DAG card.
 */

static void
dag_platform_close(pcap_t *p)
{
        
        if (p != NULL) {
#ifdef HAVE_DAG_STREAMS_API
                if(dag_stop_stream(p->fd, p->md.dag_stream) < 0)
                        fprintf(stderr,"dag_stop_stream: %s\n", strerror(errno));
                
                if(dag_detach_stream(p->fd, p->md.dag_stream) < 0)
                        fprintf(stderr,"dag_detach_stream: %s\n", strerror(errno));
#else
                if(dag_stop(p->fd) < 0)
                        fprintf(stderr,"dag_stop: %s\n", strerror(errno));
#endif /* HAVE_DAG_STREAMS_API */
                if(dag_close(p->fd) < 0)
                        fprintf(stderr,"dag_close: %s\n", strerror(errno));
        }
        delete_pcap_dag(p);
        /* Note: don't need to call close(p->fd) here as dag_close(p->fd) does this. */
}

static void
atexit_handler(void)
{
        while (pcap_dags != NULL) {
                if (pcap_dags->pid == getpid()) {
                        dag_platform_close(pcap_dags->p);
                } else {
                        delete_pcap_dag(pcap_dags->p);
                }
        }
}

static int
new_pcap_dag(pcap_t *p)
{
        pcap_dag_node_t *node = NULL;

        if ((node = malloc(sizeof(pcap_dag_node_t))) == NULL) {
                return -1;
        }

        if (!atexit_handler_installed) {
                atexit(atexit_handler);
                atexit_handler_installed = 1;
        }

        node->next = pcap_dags;
        node->p = p;
        node->pid = getpid();

        pcap_dags = node;

        return 0;
}

/*
 *  Read at most max_packets from the capture stream and call the callback
 *  for each of them. Returns the number of packets handled, -1 if an
 *  error occured, or -2 if we were told to break out of the loop.
 */
static int
dag_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
        unsigned int processed = 0;
        int flags = p->md.dag_offset_flags;
        unsigned int nonblocking = flags & DAGF_NONBLOCK;

        /* Get the next bufferful of packets (if necessary). */
        while (p->md.dag_mem_top - p->md.dag_mem_bottom < dag_record_size) {
 
                /*
                 * Has "pcap_breakloop()" been called?
                 */
                if (p->break_loop) {
                        /*
                         * Yes - clear the flag that indicates that
                         * it has, and return -2 to indicate that
                         * we were told to break out of the loop.
                         */
                        p->break_loop = 0;
                        return -2;
                }

#ifdef HAVE_DAG_STREAMS_API
                /* dag_advance_stream() will block (unless nonblock is called)
                 * until 64kB of data has accumulated.
                 * If to_ms is set, it will timeout before 64kB has accumulated.
                 * We wait for 64kB because processing a few packets at a time
                 * can cause problems at high packet rates (>200kpps) due
                 * to inefficiencies.
                 * This does mean if to_ms is not specified the capture may 'hang'
                 * for long periods if the data rate is extremely slow (<64kB/sec)
                 * If non-block is specified it will return immediately. The user
                 * is then responsible for efficiency.
                 */
                if ( NULL == (p->md.dag_mem_top = dag_advance_stream(p->fd, p->md.dag_stream, &(p->md.dag_mem_bottom))) ) {
                     return -1;
                }
#else
                /* dag_offset does not support timeouts */
                p->md.dag_mem_top = dag_offset(p->fd, &(p->md.dag_mem_bottom), flags);
#endif /* HAVE_DAG_STREAMS_API */

                if (nonblocking && (p->md.dag_mem_top - p->md.dag_mem_bottom < dag_record_size))
                {
                        /* Pcap is configured to process only available packets, and there aren't any, return immediately. */
                        return 0;
                }
                
                if(!nonblocking &&
                   p->md.dag_timeout &&
                   (p->md.dag_mem_top - p->md.dag_mem_bottom < dag_record_size))
                {
                        /* Blocking mode, but timeout set and no data has arrived, return anyway.*/
                        return 0;
                }

        }
        
        /* Process the packets. */
        while (p->md.dag_mem_top - p->md.dag_mem_bottom >= dag_record_size) {
                
                unsigned short packet_len = 0;
                int caplen = 0;
                struct pcap_pkthdr      pcap_header;
                
#ifdef HAVE_DAG_STREAMS_API
                dag_record_t *header = (dag_record_t *)(p->md.dag_mem_bottom);
#else
                dag_record_t *header = (dag_record_t *)(p->md.dag_mem_base + p->md.dag_mem_bottom);
#endif /* HAVE_DAG_STREAMS_API */

                u_char *dp = ((u_char *)header); /* + dag_record_size; */
                unsigned short rlen;
 
                /*
                 * Has "pcap_breakloop()" been called?
                 */
                if (p->break_loop) {
                        /*
                         * Yes - clear the flag that indicates that
                         * it has, and return -2 to indicate that
                         * we were told to break out of the loop.
                         */
                        p->break_loop = 0;
                        return -2;
                }
 
                rlen = ntohs(header->rlen);
                if (rlen < dag_record_size)
                {
                        strncpy(p->errbuf, "dag_read: record too small", PCAP_ERRBUF_SIZE);
                        return -1;
                }
                p->md.dag_mem_bottom += rlen;

                /* ERF encapsulation */
                /* The Extensible Record Format is not dropped for this kind of encapsulation, 
                 * and will be handled as a pseudo header by the decoding application.
                 * The information carried in the ERF header and in the optional subheader (if present)
                 * could be merged with the libpcap information, to offer a better decoding.
                 * The packet length is
                 * o the length of the packet on the link (header->wlen),
                 * o plus the length of the ERF header (dag_record_size), as the length of the 
                 *   pseudo header will be adjusted during the decoding,
                 * o plus the length of the optional subheader (if present).
                 *
                 * The capture length is header.rlen and the byte stuffing for alignment will be dropped
                 * if the capture length is greater than the packet length.
                 */
                if (p->linktype == DLT_ERF) {
                        packet_len = ntohs(header->wlen) + dag_record_size;
                        caplen = rlen;
                        switch (header->type) {
                        case TYPE_MC_AAL5:
                        case TYPE_MC_ATM:
                        case TYPE_MC_HDLC:
                                packet_len += 4; /* MC header */
                                break;

                        case TYPE_DSM_COLOR_ETH:
                        case TYPE_COLOR_ETH:
                        case TYPE_ETH:
                                packet_len += 2; /* ETH header */
                                break;
                        } /* switch type */

                        if (caplen > packet_len) {
                                caplen = packet_len;
                        }
                } else {
                        /* Other kind of encapsulation according to the header Type */
                        dp += dag_record_size;
                        
                        switch(header->type) {
                        case TYPE_ATM:
#ifdef TYPE_AAL5
                        case TYPE_AAL5:
                                if (header->type == TYPE_AAL5) {
                                        packet_len = ntohs(header->wlen);
                                        caplen = rlen - dag_record_size;
                                }
#endif
#ifdef TYPE_MC_ATM
                        case TYPE_MC_ATM:
                                if (header->type == TYPE_MC_ATM) {
                                        caplen = packet_len = ATM_CELL_SIZE;
                                        dp+=4;
                                }
#endif
#ifdef TYPE_MC_AAL5
                        case TYPE_MC_AAL5:
                                if (header->type == TYPE_MC_AAL5) {
                                        packet_len = ntohs(header->wlen);
                                        caplen = rlen - dag_record_size - 4;
                                        dp+=4;
                                }
#endif
                                if (header->type == TYPE_ATM) {
                                        caplen = packet_len = ATM_CELL_SIZE;
                                }
                                if (p->linktype == DLT_SUNATM) {
                                        struct sunatm_hdr *sunatm = (struct sunatm_hdr *)dp;
                                        unsigned long rawatm;
                                        
                                        rawatm = ntohl(*((unsigned long *)dp));
                                        sunatm->vci = htons((rawatm >>  4) & 0xffff);
                                        sunatm->vpi = (rawatm >> 20) & 0x00ff;
                                        sunatm->flags = ((header->flags.iface & 1) ? 0x80 : 0x00) | 
                                                ((sunatm->vpi == 0 && sunatm->vci == htons(5)) ? 6 :
                                                 ((sunatm->vpi == 0 && sunatm->vci == htons(16)) ? 5 : 
                                                  ((dp[ATM_HDR_SIZE] == 0xaa &&
                                                    dp[ATM_HDR_SIZE+1] == 0xaa &&
                                                    dp[ATM_HDR_SIZE+2] == 0x03) ? 2 : 1)));

                                } else {
                                        packet_len -= ATM_HDR_SIZE;
                                        caplen -= ATM_HDR_SIZE;
                                        dp += ATM_HDR_SIZE;
                                }
                                break;

#ifdef TYPE_DSM_COLOR_ETH
                        case TYPE_DSM_COLOR_ETH:
#endif
#ifdef TYPE_COLOR_ETH
                        case TYPE_COLOR_ETH:
#endif
                        case TYPE_ETH:
                                packet_len = ntohs(header->wlen);
                                packet_len -= (p->md.dag_fcs_bits >> 3);
                                caplen = rlen - dag_record_size - 2;
                                if (caplen > packet_len) {
                                        caplen = packet_len;
                                }
                                dp += 2;
                                break;
#ifdef TYPE_DSM_COLOR_HDLC_POS
                        case TYPE_DSM_COLOR_HDLC_POS:
#endif
#ifdef TYPE_COLOR_HDLC_POS
                        case TYPE_COLOR_HDLC_POS:
#endif
                        case TYPE_HDLC_POS:
                                packet_len = ntohs(header->wlen);
                                packet_len -= (p->md.dag_fcs_bits >> 3);
                                caplen = rlen - dag_record_size;
                                if (caplen > packet_len) {
                                        caplen = packet_len;
                                }
                                break;
#ifdef TYPE_COLOR_MC_HDLC_POS
                        case TYPE_COLOR_MC_HDLC_POS:
#endif
#ifdef TYPE_MC_HDLC
                        case TYPE_MC_HDLC:
                                packet_len = ntohs(header->wlen);
                                packet_len -= (p->md.dag_fcs_bits >> 3);
                                caplen = rlen - dag_record_size - 4;
                                if (caplen > packet_len) {
                                        caplen = packet_len;
                                }
                                /* jump the MC_HDLC_HEADER */
                                dp += 4;
                                if (p->linktype == DLT_MTP2_WITH_PHDR) {
                                        /* Add the MTP2 Pseudo Header */
                                        caplen += MTP2_HDR_LEN;
                                        packet_len += MTP2_HDR_LEN;

                                        TempPkt[MTP2_SENT_OFFSET] = 0;
                                        TempPkt[MTP2_ANNEX_A_USED_OFFSET] = MTP2_ANNEX_A_USED_UNKNOWN;
                                        *(TempPkt+MTP2_LINK_NUMBER_OFFSET) = ((header->rec.mc_hdlc.mc_header>>16)&0x01);
                                        *(TempPkt+MTP2_LINK_NUMBER_OFFSET+1) = ((header->rec.mc_hdlc.mc_header>>24)&0xff);
                                        memcpy(TempPkt+MTP2_HDR_LEN, dp, caplen);
                                        dp = TempPkt;
                                }
                                break;
#endif
                        default:
                                /* Unhandled ERF type.
                                 * Ignore rather than generating error
                                 */
                                continue;
                        } /* switch type */
                } /* ERF encapsulation */
                
                if (caplen > p->snapshot)
                        caplen = p->snapshot;

                /* Count lost packets. */
                switch(header->type) {
#ifdef TYPE_COLOR_HDLC_POS
                        /* in this type the color value overwrites the lctr */
                case TYPE_COLOR_HDLC_POS:
                        break;
#endif
#ifdef TYPE_COLOR_ETH
                        /* in this type the color value overwrites the lctr */
                case TYPE_COLOR_ETH:
                        break;
#endif
#ifdef TYPE_DSM_COLOR_HDLC_POS
                        /* in this type the color value overwrites the lctr */
                case TYPE_DSM_COLOR_HDLC_POS:
                        break;
#endif
#ifdef TYPE_DSM_COLOR_ETH
                        /* in this type the color value overwrites the lctr */
                case TYPE_DSM_COLOR_ETH:
                        break;
#endif
#ifdef TYPE_COLOR_MC_HDLC_POS
                case TYPE_COLOR_MC_HDLC_POS:
                        break;
#endif

                default:
                        if (header->lctr) {
                                if (p->md.stat.ps_drop > (UINT_MAX - ntohs(header->lctr))) {
                                        p->md.stat.ps_drop = UINT_MAX;
                                } else {
                                        p->md.stat.ps_drop += ntohs(header->lctr);
                                }
                        }
                }
                
                /* Run the packet filter if there is one. */
                if ((p->fcode.bf_insns == NULL) || bpf_filter(p->fcode.bf_insns, dp, packet_len, caplen)) {
                        
                        /* convert between timestamp formats */
                        register unsigned long long ts;
                                
                        if (IS_BIGENDIAN()) {
                                ts = SWAPLL(header->ts);
                        } else {
                                ts = header->ts;
                        }

                        pcap_header.ts.tv_sec = ts >> 32;
                        ts = (ts & 0xffffffffULL) * 1000000;
                        ts += 0x80000000; /* rounding */
                        pcap_header.ts.tv_usec = ts >> 32;              
                        if (pcap_header.ts.tv_usec >= 1000000) {
                                pcap_header.ts.tv_usec -= 1000000;
                                pcap_header.ts.tv_sec++;
                        }

                        /* Fill in our own header data */
                        pcap_header.caplen = caplen;
                        pcap_header.len = packet_len;
        
                        /* Count the packet. */
                        p->md.stat.ps_recv++;
        
                        /* Call the user supplied callback function */
                        callback(user, &pcap_header, dp);
        
                        /* Only count packets that pass the filter, for consistency with standard Linux behaviour. */
                        processed++;
                        if (processed == cnt)
                        {
                                /* Reached the user-specified limit. */
                                return cnt;
                        }
                }
        }

        return processed;
}

static int
dag_inject(pcap_t *p, const void *buf _U_, size_t size _U_)
{
        strlcpy(p->errbuf, "Sending packets isn't supported on DAG cards",
            PCAP_ERRBUF_SIZE);
        return (-1);
}

/*
 *  Get a handle for a live capture from the given DAG device.  Passing a NULL
 *  device will result in a failure.  The promisc flag is ignored because DAG
 *  cards are always promiscuous.  The to_ms parameter is also ignored as it is
 *  not supported in hardware.
 *  
 *  snaplen is now also ignored, until we get per-stream slen support. Set
 *  slen with approprite DAG tool BEFORE pcap_open_live().
 *
 *  See also pcap(3).
 */
pcap_t *
dag_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebuf)
{
        char conf[30]; /* dag configure string */
        pcap_t *handle;
        char *s;
        int n;
        daginf_t* daginf;
        char * newDev = NULL;
#ifdef HAVE_DAG_STREAMS_API
        uint32_t mindata;
        struct timeval maxwait;
        struct timeval poll;
#endif

        if (device == NULL) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "device is NULL: %s", pcap_strerror(errno));
                return NULL;
        }
        /* Allocate a handle for this session. */

        handle = malloc(sizeof(*handle));
        if (handle == NULL) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc %s: %s", device, pcap_strerror(errno));
                return NULL;
        }
        
        /* Initialize some components of the pcap structure. */
        
        memset(handle, 0, sizeof(*handle));

#ifdef HAVE_DAG_STREAMS_API
        newDev = (char *)malloc(strlen(device) + 16);
        if (newDev == NULL) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "Can't allocate string for device name: %s\n", pcap_strerror(errno));
                goto fail;
        }
        
        /* Parse input name to get dag device and stream number if provided */
        if (dag_parse_name(device, newDev, strlen(device) + 16, &handle->md.dag_stream) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_parse_name: %s\n", pcap_strerror(errno));
                goto fail;
        }
        device = newDev;

        if (handle->md.dag_stream%2) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_parse_name: tx (even numbered) streams not supported for capture\n");
                goto fail;
        }
#else
        if (strncmp(device, "/dev/", 5) != 0) {
                newDev = (char *)malloc(strlen(device) + 5);
                if (newDev == NULL) {
                        snprintf(ebuf, PCAP_ERRBUF_SIZE, "Can't allocate string for device name: %s\n", pcap_strerror(errno));
                        goto fail;
                }
                strcpy(newDev, "/dev/");
                strcat(newDev, device);
                device = newDev;
        }
#endif /* HAVE_DAG_STREAMS_API */

        /* setup device parameters */
        if((handle->fd = dag_open((char *)device)) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_open %s: %s", device, pcap_strerror(errno));
                goto fail;
        }

#ifdef HAVE_DAG_STREAMS_API
        /* Open requested stream. Can fail if already locked or on error */
        if (dag_attach_stream(handle->fd, handle->md.dag_stream, 0, 0) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_attach_stream: %s\n", pcap_strerror(errno));
                goto failclose;
        }

        /* Set up default poll parameters for stream
         * Can be overridden by pcap_set_nonblock()
         */
        if (dag_get_stream_poll(handle->fd, handle->md.dag_stream,
                                &mindata, &maxwait, &poll) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_get_stream_poll: %s\n", pcap_strerror(errno));
                goto faildetach;
        }
        
        /* Amount of data to collect in Bytes before calling callbacks.
         * Important for efficiency, but can introduce latency
         * at low packet rates if to_ms not set!
         */
        mindata = 65536;

        /* Obey to_ms if supplied. This is a good idea!
         * Recommend 10-100ms. Calls will time out even if no data arrived.
         */
        maxwait.tv_sec = to_ms/1000;
        maxwait.tv_usec = (to_ms%1000) * 1000;

        if (dag_set_stream_poll(handle->fd, handle->md.dag_stream,
                                mindata, &maxwait, &poll) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_set_stream_poll: %s\n", pcap_strerror(errno));
                goto faildetach;
        }
                
#else
        if((handle->md.dag_mem_base = dag_mmap(handle->fd)) == MAP_FAILED) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE,"dag_mmap %s: %s\n", device, pcap_strerror(errno));
                goto failclose;
        }

#endif /* HAVE_DAG_STREAMS_API */

        /* XXX Not calling dag_configure() to set slen; this is unsafe in
         * multi-stream environments as the gpp config is global.
         * Once the firmware provides 'per-stream slen' this can be supported
         * again via the Config API without side-effects */
#if 0
        /* set the card snap length to the specified snaplen parameter */
        /* This is a really bad idea, as different cards have different
         * valid slen ranges. Should fix in Config API. */
        if (snaplen == 0 || snaplen > MAX_DAG_SNAPLEN) {
                snaplen = MAX_DAG_SNAPLEN;
        } else if (snaplen < MIN_DAG_SNAPLEN) {
                snaplen = MIN_DAG_SNAPLEN;
        }
        /* snap len has to be a multiple of 4 */
        snprintf(conf, 30, "varlen slen=%d", (snaplen + 3) & ~3); 

        if(dag_configure(handle->fd, conf) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE,"dag_configure %s: %s\n", device, pcap_strerror(errno));
                goto faildetach;
        }
#endif  
        
#ifdef HAVE_DAG_STREAMS_API
        if(dag_start_stream(handle->fd, handle->md.dag_stream) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_start_stream %s: %s\n", device, pcap_strerror(errno));
                goto faildetach;
        }
#else
        if(dag_start(handle->fd) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_start %s: %s\n", device, pcap_strerror(errno));
                goto failclose;
        }
#endif /* HAVE_DAG_STREAMS_API */

        /*
         * Important! You have to ensure bottom is properly
         * initialized to zero on startup, it won't give you
         * a compiler warning if you make this mistake!
         */
        handle->md.dag_mem_bottom = 0;
        handle->md.dag_mem_top = 0;

        /*
         * Find out how many FCS bits we should strip.
         * First, query the card to see if it strips the FCS.
         */
        daginf = dag_info(handle->fd);
        if ((0x4200 == daginf->device_code) || (0x4230 == daginf->device_code)) {
                /* DAG 4.2S and 4.23S already strip the FCS.  Stripping the final word again truncates the packet. */
                handle->md.dag_fcs_bits = 0;

                /* Note that no FCS will be supplied. */
                handle->linktype_ext = LT_FCS_DATALINK_EXT(0);
        } else {
                /*
                 * Start out assuming it's 32 bits.
                 */
                handle->md.dag_fcs_bits = 32;

                /* Allow an environment variable to override. */
                if ((s = getenv("ERF_FCS_BITS")) != NULL) {
                        if ((n = atoi(s)) == 0 || n == 16 || n == 32) {
                                handle->md.dag_fcs_bits = n;
                        } else {
                                snprintf(ebuf, PCAP_ERRBUF_SIZE,
                                        "pcap_open_live %s: bad ERF_FCS_BITS value (%d) in environment\n", device, n);
                                goto failstop;
                        }
                }

                /*
                 * Did the user request that they not be stripped?
                 */
                if ((s = getenv("ERF_DONT_STRIP_FCS")) != NULL) {
                        /* Yes.  Note the number of bytes that will be
                           supplied. */
                        handle->linktype_ext = LT_FCS_DATALINK_EXT(handle->md.dag_fcs_bits/16);

                        /* And don't strip them. */
                        handle->md.dag_fcs_bits = 0;
                }
        }

        handle->snapshot        = snaplen;
        handle->md.dag_timeout  = to_ms;

        handle->linktype = -1;
        if (dag_get_datalink(handle) < 0) {
                strcpy(ebuf, handle->errbuf);
                goto failstop;
        }
        
        handle->bufsize = 0;

        if (new_pcap_dag(handle) < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "new_pcap_dag %s: %s\n", device, pcap_strerror(errno));
                goto failstop;
        }

        /*
         * "select()" and "poll()" don't work on DAG device descriptors.
         */
        handle->selectable_fd = -1;

        if (newDev != NULL) {
                free((char *)newDev);
        }

        handle->read_op = dag_read;
        handle->inject_op = dag_inject;
        handle->setfilter_op = dag_setfilter;
        handle->setdirection_op = NULL; /* Not implemented.*/
        handle->set_datalink_op = dag_set_datalink;
        handle->getnonblock_op = pcap_getnonblock_fd;
        handle->setnonblock_op = dag_setnonblock;
        handle->stats_op = dag_stats;
        handle->close_op = dag_platform_close;
        handle->md.stat.ps_drop = 0;
        handle->md.stat.ps_recv = 0;
        return handle;

#ifdef HAVE_DAG_STREAMS_API 
failstop:
        if (handle != NULL) {
                if (dag_stop_stream(handle->fd, handle->md.dag_stream) < 0)
                        fprintf(stderr,"dag_stop_stream: %s\n", strerror(errno));
        }
        
faildetach:
        if (handle != NULL) {
                if (dag_detach_stream(handle->fd, handle->md.dag_stream) < 0)
                        fprintf(stderr,"dag_detach_stream: %s\n", strerror(errno));
        }
#else   
failstop:
        if (handle != NULL) {
                if (dag_stop(p->fd) < 0)
                        fprintf(stderr,"dag_stop: %s\n", strerror(errno));
        }
#endif /* HAVE_DAG_STREAMS_API */
        
failclose:
        if (handle != NULL) {
                if (dag_close(handle->fd) < 0)
                        fprintf(stderr,"dag_close: %s\n", strerror(errno));
        }
        if (handle != NULL)
                delete_pcap_dag(handle);
        
fail:
        if (newDev != NULL) {
                free((char *)newDev);
        }
        if (handle != NULL) {
                /*
                 * Get rid of any link-layer type list we allocated.
                 */
                if (handle->dlt_list != NULL) {
                        free(handle->dlt_list);
                }
                free(handle);
        }

        return NULL;
}

static int
dag_stats(pcap_t *p, struct pcap_stat *ps) {
        /* This needs to be filled out correctly.  Hopefully a dagapi call will
                 provide all necessary information.
        */
        /*p->md.stat.ps_recv = 0;*/
        /*p->md.stat.ps_drop = 0;*/
        
        *ps = p->md.stat;
 
        return 0;
}

/*
 * Previously we just generated a list of all possible names and let
 * pcap_add_if() attempt to open each one, but with streams this adds up
 * to 81 possibilities which is inefficient.
 *
 * Since we know more about the devices we can prune the tree here.
 * pcap_add_if() will still retest each device but the total number of
 * open attempts will still be much less than the naive approach.
 */
int
dag_platform_finddevs(pcap_if_t **devlistp, char *errbuf)
{
        char name[12];  /* XXX - pick a size */
        int ret = 0;
        int c;
        char dagname[DAGNAME_BUFSIZE];
        int dagstream;
        int dagfd;

        /* Try all the DAGs 0-9 */
        for (c = 0; c < 9; c++) {
                snprintf(name, 12, "dag%d", c);
                if (-1 == dag_parse_name(name, dagname, DAGNAME_BUFSIZE, &dagstream))
                {
                        return -1;
                }
                if ( (dagfd = dag_open(dagname)) >= 0 ) {
                        if (pcap_add_if(devlistp, name, 0, NULL, errbuf) == -1) {
                                /*
                                 * Failure.
                                 */
                                ret = -1;
                        }
#ifdef HAVE_DAG_STREAMS_API
                        {
                                int stream, rxstreams, found=0;
                                rxstreams = dag_rx_get_stream_count(dagfd);
                                for(stream=0;stream<16;stream+=2) {
                                        if (0 == dag_attach_stream(dagfd, stream, 0, 0)) {
                                                dag_detach_stream(dagfd, stream);

                                                snprintf(name,  10, "dag%d:%d", c, stream);
                                                if (pcap_add_if(devlistp, name, 0, NULL, errbuf) == -1) {
                                                        /*
                                                         * Failure.
                                                         */
                                                        ret = -1;
                                                }
                                        }
                                }                               
                        }
#endif  /* HAVE_DAG_STREAMS_API */
                        dag_close(dagfd);
                }

        }
        return (ret);
}

/*
 * Installs the given bpf filter program in the given pcap structure.  There is
 * no attempt to store the filter in kernel memory as that is not supported
 * with DAG cards.
 */
static int
dag_setfilter(pcap_t *p, struct bpf_program *fp)
{
        if (!p)
                return -1;
        if (!fp) {
                strncpy(p->errbuf, "setfilter: No filter specified",
                        sizeof(p->errbuf));
                return -1;
        }

        /* Make our private copy of the filter */

        if (install_bpf_program(p, fp) < 0)
                return -1;

        p->md.use_bpf = 0;

        return (0);
}

static int
dag_set_datalink(pcap_t *p, int dlt)
{
        p->linktype = dlt;

        return (0);
}

static int
dag_setnonblock(pcap_t *p, int nonblock, char *errbuf)
{
        /*
         * Set non-blocking mode on the FD.
         * XXX - is that necessary?  If not, don't bother calling it,
         * and have a "dag_getnonblock()" function that looks at
         * "p->md.dag_offset_flags".
         */
        if (pcap_setnonblock_fd(p, nonblock, errbuf) < 0)
                return (-1);
#ifdef HAVE_DAG_STREAMS_API
        {
                uint32_t mindata;
                struct timeval maxwait;
                struct timeval poll;
                
                if (dag_get_stream_poll(p->fd, p->md.dag_stream,
                                        &mindata, &maxwait, &poll) < 0) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE, "dag_get_stream_poll: %s\n", pcap_strerror(errno));
                        return -1;
                }
                
                /* Amount of data to collect in Bytes before calling callbacks.
                 * Important for efficiency, but can introduce latency
                 * at low packet rates if to_ms not set!
                 */
                if(nonblock)
                        mindata = 0;
                else
                        mindata = 65536;
                
                if (dag_set_stream_poll(p->fd, p->md.dag_stream,
                                        mindata, &maxwait, &poll) < 0) {
                        snprintf(errbuf, PCAP_ERRBUF_SIZE, "dag_set_stream_poll: %s\n", pcap_strerror(errno));
                        return -1;
                }
        }
#endif /* HAVE_DAG_STREAMS_API */
        if (nonblock) {
                p->md.dag_offset_flags |= DAGF_NONBLOCK;
        } else {
                p->md.dag_offset_flags &= ~DAGF_NONBLOCK;
        }
        return (0);
}
                
static int
dag_get_datalink(pcap_t *p)
{
        int index=0, dlt_index=0;
        uint8_t types[255];

        memset(types, 0, 255);

        if (p->dlt_list == NULL && (p->dlt_list = malloc(255*sizeof(*(p->dlt_list)))) == NULL) {
                (void)snprintf(p->errbuf, sizeof(p->errbuf), "malloc: %s", pcap_strerror(errno));
                return (-1);
        }

        p->linktype = 0;

#ifdef HAVE_DAG_GET_STREAM_ERF_TYPES
        /* Get list of possible ERF types for this card */
        if (dag_get_stream_erf_types(p->fd, p->md.dag_stream, types, 255) < 0) {
                snprintf(p->errbuf, sizeof(p->errbuf), "dag_get_stream_erf_types: %s", pcap_strerror(errno));
                return (-1);            
        }
        
        while (types[index]) {

#elif defined HAVE_DAG_GET_ERF_TYPES
        /* Get list of possible ERF types for this card */
        if (dag_get_erf_types(p->fd, types, 255) < 0) {
                snprintf(p->errbuf, sizeof(p->errbuf), "dag_get_erf_types: %s", pcap_strerror(errno));
                return (-1);            
        }
        
        while (types[index]) {
#else
        /* Check the type through a dagapi call. */
        types[index] = dag_linktype(p->fd);

        {
#endif
                switch(types[index]) {

                case TYPE_HDLC_POS:
#ifdef TYPE_COLOR_HDLC_POS
                case TYPE_COLOR_HDLC_POS:
#endif
#ifdef TYPE_DSM_COLOR_HDLC_POS
                case TYPE_DSM_COLOR_HDLC_POS:
#endif
                        if (p->dlt_list != NULL) {
                                p->dlt_list[dlt_index++] = DLT_CHDLC;
                                p->dlt_list[dlt_index++] = DLT_PPP_SERIAL;
                                p->dlt_list[dlt_index++] = DLT_FRELAY;
                        }
                        if(!p->linktype)
                                p->linktype = DLT_CHDLC;
                        break;

                case TYPE_ETH:
#ifdef TYPE_COLOR_ETH
                case TYPE_COLOR_ETH:
#endif
#ifdef TYPE_DSM_COLOR_ETH
                case TYPE_DSM_COLOR_ETH:
#endif
                        /*
                         * This is (presumably) a real Ethernet capture; give it a
                         * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, so
                         * that an application can let you choose it, in case you're
                         * capturing DOCSIS traffic that a Cisco Cable Modem
                         * Termination System is putting out onto an Ethernet (it
                         * doesn't put an Ethernet header onto the wire, it puts raw
                         * DOCSIS frames out on the wire inside the low-level
                         * Ethernet framing).
                         */
                        if (p->dlt_list != NULL) {
                                p->dlt_list[dlt_index++] = DLT_EN10MB;
                                p->dlt_list[dlt_index++] = DLT_DOCSIS;
                        }
                        if(!p->linktype)
                                p->linktype = DLT_EN10MB;
                        break;

                case TYPE_ATM: 
#ifdef TYPE_AAL5
                case TYPE_AAL5:
#endif
#ifdef TYPE_MC_ATM
                case TYPE_MC_ATM:
#endif
#ifdef TYPE_MC_AAL5
                case TYPE_MC_AAL5:
#endif
                        if (p->dlt_list != NULL) {
                                p->dlt_list[dlt_index++] = DLT_ATM_RFC1483;
                                p->dlt_list[dlt_index++] = DLT_SUNATM;
                        }
                        if(!p->linktype)
                                p->linktype = DLT_ATM_RFC1483;
                        break;

#ifdef TYPE_COLOR_MC_HDLC_POS
                case TYPE_COLOR_MC_HDLC_POS:
#endif
#ifdef TYPE_MC_HDLC
                case TYPE_MC_HDLC:
                        if (p->dlt_list != NULL) {
                                p->dlt_list[dlt_index++] = DLT_CHDLC;
                                p->dlt_list[dlt_index++] = DLT_PPP_SERIAL;
                                p->dlt_list[dlt_index++] = DLT_FRELAY;
                                p->dlt_list[dlt_index++] = DLT_MTP2;
                                p->dlt_list[dlt_index++] = DLT_MTP2_WITH_PHDR;
                                p->dlt_list[dlt_index++] = DLT_LAPD;
                        }
                        if(!p->linktype)
                                p->linktype = DLT_CHDLC;
                        break;
#endif

                case TYPE_LEGACY:
                        if(!p->linktype)
                                p->linktype = DLT_NULL;
                        break;

                default:
                        snprintf(p->errbuf, sizeof(p->errbuf), "unknown DAG linktype %d", types[index]);
                        return (-1);

                } /* switch */
                index++;
        }

        p->dlt_list[dlt_index++] = DLT_ERF;

        p->dlt_count = dlt_index;

        return p->linktype;
}