source: lib/format_dpdk.c @ 6c3b3d7

/*
 * This file is part of libtrace
 *
 * Copyright (c) 2007,2008,2009,2010 The University of Waikato, Hamilton, 
 * New Zealand.
 *
 * Author: Richard Sanger 
 *          
 * 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: format_dpdk.c 1805 2013-03-08 02:01:35Z salcock $
 *
 */

/* This format module deals with using the Intel Data Plane Development
 * Kit capture format.
 *
 * Intel Data Plane Development Kit is a LIVE capture format.
 *
 * This format also supports writing which will write packets out to the 
 * network as a form of packet replay. This should not be confused with the 
 * RT protocol which is intended to transfer captured packet records between 
 * RT-speaking programs.
 */

#include "config.h"
#include "libtrace.h"
#include "libtrace_int.h"
#include "format_helper.h"
#include "libtrace_arphrd.h"

#ifdef HAVE_INTTYPES_H
#  include <inttypes.h>
#else
# error "Can't find inttypes.h"
#endif

#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <endian.h>
#include <string.h>

/* We can deal with any minor differences by checking the RTE VERSION
 * Typically DPDK backports some fixes (typically for building against
 * newer kernels) to the older version of DPDK.
 *
 * These get released with the rX suffix. The following macros where added
 * in these new releases.
 *
 * Below this is a log of version that required changes to the libtrace
 * code (that we still attempt to support).
 *
 * Currently 1.5 to 1.7 is supported.
 */
#include <rte_eal.h>
#include <rte_version.h>
#ifndef RTE_VERSION_NUM
#       define RTE_VERSION_NUM(a,b,c,d) ((a) << 24 | (b) << 16 | (c) << 8 | (d))
#endif
#ifndef RTE_VER_PATCH_RELEASE
#       define RTE_VER_PATCH_RELEASE 0
#endif
#ifndef RTE_VERSION
#       define RTE_VERSION RTE_VERSION_NUM(RTE_VER_MAJOR,RTE_VER_MINOR, \
        RTE_VER_PATCH_LEVEL, RTE_VER_PATCH_RELEASE)
#endif

/* 1.6.0r2 :
 *      rte_eal_pci_set_blacklist() is removed
 *      device_list is renamed ot pci_device_list
 *
 * Replaced by:
 *      rte_devargs (we can simply whitelist)
 */
#if RTE_VERSION <= RTE_VERSION_NUM(1, 6, 0, 1)
#       define DPDK_USE_BLACKLIST 1
#else
#       define DPDK_USE_BLACKLIST 0
#endif

/*
 * 1.7.0 :
 *      rte_pmd_init_all is removed
 *
 * Replaced by:
 *      Nothing, no longer needed
 */
#if RTE_VERSION < RTE_VERSION_NUM(1, 7, 0, 0)
#       define DPDK_USE_PMD_INIT 1
#else
#       define DPDK_USE_PMD_INIT 0
#endif

#include <rte_per_lcore.h>
#include <rte_debug.h>
#include <rte_errno.h>
#include <rte_common.h>
#include <rte_log.h>
#include <rte_memcpy.h>
#include <rte_prefetch.h>
#include <rte_branch_prediction.h>
#include <rte_pci.h>
#include <rte_ether.h>
#include <rte_ethdev.h>
#include <rte_ring.h>
#include <rte_mempool.h>
#include <rte_mbuf.h>

/* The default size of memory buffers to use - This is the max size of standard 
 * ethernet packet less the size of the MAC CHECKSUM */
#define RX_MBUF_SIZE 1514

/* The minimum number of memory buffers per queue tx or rx. Search for 
 * _MIN_RING_DESC in DPDK. The largest minimum is 64 for 10GBit cards.
 */
#define MIN_NB_BUF 64

/* Number of receive memory buffers to use
 * By default this is limited by driver to 4k and must be a multiple of 128.
 * A modification can be made to the driver to remove this limit.
 * This can be increased in the driver and here.
 * Should be at least MIN_NB_BUF.
 */
#define NB_RX_MBUF 4096

/* Number of send memory buffers to use.
 * Same limits apply as those to NB_TX_MBUF.
 */
#define NB_TX_MBUF 1024

/* The size of the PCI blacklist needs to be big enough to contain 
 * every PCI device address (listed by lspci every bus:device.function tuple).
 */
#define BLACK_LIST_SIZE 50

/* The maximum number of characters the mempool name can be */
#define MEMPOOL_NAME_LEN 20

#define MBUF(x) ((struct rte_mbuf *) x)
/* Get the original placement of the packet data */
#define MBUF_PKTDATA(x) ((char *) x + sizeof(struct rte_mbuf) + RTE_PKTMBUF_HEADROOM)
#define FORMAT(x) ((struct dpdk_format_data_t*)(x->format_data))
#define TV_TO_NS(tv) ((uint64_t) tv.tv_sec*1000000000ull + \
                        (uint64_t) tv.tv_usec*1000ull)
#define TS_TO_NS(ts) ((uint64_t) ts.tv_sec*1000000000ull + \
                        (uint64_t) ts.tv_nsec)

#if RTE_PKTMBUF_HEADROOM != 128
#warning "RTE_PKT_MBUF_HEADROOM is not set to the default value of 128 - " \
         "any libtrace instance processing these packet must be have the" \
         "same RTE_PKTMBUF_HEADROOM set"
#endif

/* ~~~~~~~~~~~~~~~~~~~~~~ Advance settings ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * THESE MAY REQUIRE MODIFICATIONS TO INTEL DPDK 
 * 
 * Make sure you understand what these are doing before enabling them.
 * They might make traces incompatable with other builds etc.
 * 
 * These are also included to show how to do somethings which aren't
 * obvious in the DPDK documentation.
 */

/* Print verbose messages to stdout */
#define DEBUG 0

/* Use clock_gettime() for nanosecond resolution rather than gettimeofday() 
 * only turn on if you know clock_gettime is a vsyscall on your system 
 * overwise could be a large overhead. Again gettimeofday() should be
 * vsyscall also if it's not you should seriously consider updating your
 * kernel.
 */
#ifdef HAVE_LIBRT
/* You can turn this on (set to 1) to prefer clock_gettime */
#define USE_CLOCK_GETTIME 0
#else
/* DONT CHANGE THIS !!! */
#define USE_CLOCK_GETTIME 0
#endif

/* This is fairly safe to turn on - currently there appears to be a 'bug'
 * in DPDK that will remove the checksum by making the packet appear 4bytes
 * smaller than what it really is. Most formats don't include the checksum
 * hence writing out a port such as int: ring: and dpdk: assumes there
 * is no checksum and will attempt to write the checksum as part of the
 * packet 
 */
#define GET_MAC_CRC_CHECKSUM 0

/* This requires a modification of the pmd drivers (inside Intel DPDK)
 */
#define HAS_HW_TIMESTAMPS_82580 0

#if HAS_HW_TIMESTAMPS_82580
# define TS_NBITS_82580     40
/* The maximum on the +ve or -ve side that we can be, make it half way */
# define MAXSKEW_82580 ((uint64_t) (.5 * (double)(1ull<<TS_NBITS_82580)))
#define WITHIN_VARIANCE(v1,v2,var) (((v1) - (var) < (v2)) && ((v1) + (var) > (v2)))
#endif

/* As per Intel 82580 specification - mismatch in 82580 datasheet
 * it states ts is stored in Big Endian, however its actually Little */
struct hw_timestamp_82580 {
    uint64_t reserved;
    uint64_t timestamp; /* Little Endian only lower 40 bits are valid */
};

enum paused_state {
    DPDK_NEVER_STARTED,
    DPDK_RUNNING,
    DPDK_PAUSED,
};

/* Used by both input and output however some fields are not used
 * for output */
struct dpdk_format_data_t {
    int8_t promisc; /* promiscuous mode - RX only */
    uint8_t port; /* Always 0 we only whitelist a single port - Shared TX & RX */
    uint8_t nb_ports; /* Total number of usable ports on system should be 1 */
    uint8_t paused; /* See paused_state */ 
    uint16_t queue_id; /* Always 0 we use a single queue - Shared TX & RX */
    int snaplen; /* The snap length for the capture - RX only */
    /* We always have to setup both rx and tx queues even if we don't want them */
    int nb_rx_buf; /* The number of packet buffers in the rx ring */
    int nb_tx_buf; /* The number of packet buffers in the tx ring */
    struct rte_mempool * pktmbuf_pool; /* Our packet memory pool */
#if DPDK_USE_BLACKLIST
    struct rte_pci_addr blacklist[BLACK_LIST_SIZE]; /* Holds our device blacklist */
        unsigned int nb_blacklist; /* Number of blacklist items in are valid */
#endif
    char mempool_name[MEMPOOL_NAME_LEN]; /* The name of the mempool that we are using */
#if HAS_HW_TIMESTAMPS_82580
    /* Timestamping only relevent to RX */
    uint64_t ts_first_sys; /* Sytem timestamp of the first packet in nanoseconds */
    uint64_t ts_last_sys; /* System timestamp of our most recent packet in nanoseconds */
    uint32_t wrap_count; /* Number of times the NIC clock has wrapped around completely */
#endif
};

enum dpdk_addt_hdr_flags {
    INCLUDES_CHECKSUM = 0x1,
    INCLUDES_HW_TIMESTAMP = 0x2, /* Used with 82580 driver */
};

/** 
 * A structure placed in front of the packet where we can store
 * additional information about the given packet.
 * +--------------------------+
 * |       rte_mbuf (pkt)     | sizeof(rte_mbuf)
 * +--------------------------+
 * |           padding        | RTE_PKTMBUF_HEADROOM-1-sizeof(dpdk_addt_hdr)
 * +--------------------------+
 * |       dpdk_addt_hdr      | sizeof(dpdk_addt_hdr)
 * +--------------------------+
 * |   sizeof(dpdk_addt_hdr)  | 1 byte
 * +--------------------------+ 
 * *   hw_timestamp_82580     * 16 bytes Optional
 * +--------------------------+
 * |       Packet data        | Variable Size
 * |                          |
 */
struct dpdk_addt_hdr {
    uint64_t timestamp;
    uint8_t flags;
    uint8_t direction;
    uint8_t reserved1;
    uint8_t reserved2;
    uint32_t cap_len; /* The size to say the capture is */
};

/**
 * We want to blacklist all devices except those on the whitelist
 * (I say list, but yes it is only the one).
 * 
 * The default behaviour of rte_pci_probe() will map every possible device
 * to its DPDK driver. The DPDK driver will take the ethernet device
 * out of the kernel (i.e. no longer /dev/ethx) and cannot be used.
 * 
 * So blacklist all devices except the one that we wish to use so that 
 * the others can still be used as standard ethernet ports.
 *
 * @return 0 if successful, otherwise -1 on error.
 */
#if DPDK_USE_BLACKLIST
static int blacklist_devices(struct dpdk_format_data_t *format_data, struct rte_pci_addr *whitelist)
{
        struct rte_pci_device *dev = NULL;
        format_data->nb_blacklist = 0;

        memset(format_data->blacklist, 0, sizeof (format_data->blacklist));

        TAILQ_FOREACH(dev, &device_list, next) {
        if (whitelist != NULL && whitelist->domain == dev->addr.domain 
            && whitelist->bus == dev->addr.bus
            && whitelist->devid == dev->addr.devid
            && whitelist->function == dev->addr.function)
            continue;
                if (format_data->nb_blacklist >= sizeof (format_data->blacklist)
                                / sizeof (format_data->blacklist[0])) {
                        printf("Warning: too many devices to blacklist consider"
                                        " increasing BLACK_LIST_SIZE");
                        break;
                }
                format_data->blacklist[format_data->nb_blacklist] = dev->addr;
                ++format_data->nb_blacklist;
        }

        rte_eal_pci_set_blacklist(format_data->blacklist, format_data->nb_blacklist);
        return 0;
}
#else /* DPDK_USE_BLACKLIST */
#include <rte_devargs.h>
static int blacklist_devices(struct dpdk_format_data_t *format_data UNUSED, struct rte_pci_addr *whitelist)
{
        char pci_str[20] = {0};
        snprintf(pci_str, sizeof(pci_str), PCI_PRI_FMT,
                 whitelist->domain,
                 whitelist->bus,
                 whitelist->devid,
                 whitelist->function);
        if (rte_eal_devargs_add(RTE_DEVTYPE_WHITELISTED_PCI, pci_str) < 0) {
                return -1;
        }
        return 0;
}
#endif

/**
 * Parse the URI format as a pci address
 * Fills in addr, note core is optional and is unchanged if
 * a value for it is not provided.
 * 
 * i.e. ./libtrace dpdk:0:1:0.0 -> 0:1:0.0
 * or ./libtrace dpdk:0:1:0.1-2 -> 0:1:0.1 (Using CPU core #2) 
 */
static int parse_pciaddr(char * str, struct rte_pci_addr * addr, long * core) {
    char * wrkstr;
    char * pch;
    assert(str);
    wrkstr = strdup(str);
    
    pch = strtok(wrkstr,":");
    if (pch == NULL || pch[0] == 0) {
        free(wrkstr); return -1;
    }
    addr->domain = (uint16_t) atoi(pch);

    pch = strtok(NULL,":");
    if (pch == NULL || pch[0] == 0) {
        free(wrkstr); return -1;
    }
    addr->bus = (uint8_t) atoi(pch);

    pch = strtok(NULL,".");
    if (pch == NULL || pch[0] == 0) {
        free(wrkstr); return -1;
    }
    addr->devid = (uint8_t) atoi(pch);

    pch = strtok(NULL,"-"); /* Might not find the '-' it's optional */
    if (pch == NULL || pch[0] == 0) {
        free(wrkstr); return -1;
    }
    addr->function = (uint8_t) atoi(pch);

    pch = strtok(NULL, ""); /* Find end of string */
    
    if (pch != NULL && pch[0] != 0) {
        *core = (long) atoi(pch);
    }

    free(wrkstr);
    return 0;
}

#if DEBUG
/* For debugging */
static inline void dump_configuration()
{
    struct rte_config * global_config;
    long nb_cpu = sysconf(_SC_NPROCESSORS_ONLN);
    
    if (nb_cpu <= 0) {
        perror("sysconf(_SC_NPROCESSORS_ONLN) failed. Falling back to the first core.");
        nb_cpu = 1; /* fallback to just 1 core */
    }
    if (nb_cpu > RTE_MAX_LCORE)
        nb_cpu = RTE_MAX_LCORE;
    
    global_config = rte_eal_get_configuration();
    
    if (global_config != NULL) {
        int i;
        fprintf(stderr, "Intel DPDK setup\n"
               "---Version      : %"PRIu32"\n"
               "---Magic        : %"PRIu32"\n"
               "---Master LCore : %"PRIu32"\n"
               "---LCore Count  : %"PRIu32"\n",
               global_config->version, global_config->magic, 
               global_config->master_lcore, global_config->lcore_count);
        
        for (i = 0 ; i < nb_cpu; i++) {
            fprintf(stderr, "   ---Core %d : %s\n", i, 
                   global_config->lcore_role[i] == ROLE_RTE ? "on" : "off");
        }
        
        const char * proc_type;
        switch (global_config->process_type) {
            case RTE_PROC_AUTO:
                proc_type = "auto";
                break;
            case RTE_PROC_PRIMARY:
                proc_type = "primary";
                break;
            case RTE_PROC_SECONDARY:
                proc_type = "secondary";
                break;
            case RTE_PROC_INVALID:
                proc_type = "invalid";
                break;
            default:
                proc_type = "something worse than invalid!!";
        }
        fprintf(stderr, "---Process Type : %s\n", proc_type);
    }
    
}
#endif

static inline int dpdk_init_environment(char * uridata, struct dpdk_format_data_t * format_data,
                                        char * err, int errlen) {
    int ret; /* Returned error codes */
    struct rte_pci_addr use_addr; /* The only address that we don't blacklist */
    char cpu_number[10] = {0}; /* The CPU mask we want to bind to */
    char mem_map[20] = {0}; /* The memory name */
    long nb_cpu; /* The number of CPUs in the system */
    long my_cpu; /* The CPU number we want to bind to */
    
#if DEBUG
    rte_set_log_level(RTE_LOG_DEBUG);
#else 
    rte_set_log_level(RTE_LOG_WARNING);
#endif
    /*
     * Using unique file prefixes mean separate memory is used, unlinking
     * the two processes. However be careful we still cannot access a 
     * port that already in use.
     */
    char* argv[] = {"libtrace", "-c", cpu_number, "-n", "1", "--proc-type", "auto",
                "--file-prefix", mem_map, "-m", "256", NULL};
    int argc = sizeof(argv) / sizeof(argv[0]) - 1;

    /* This initialises the Environment Abstraction Layer (EAL)
     * If we had slave workers these are put into WAITING state
     * 
     * Basically binds this thread to a fixed core, which we choose as
     * the last core on the machine (assuming fewer interrupts mapped here).
     * "-c" controls the cpu mask 0x1=1st core 0x2=2nd 0x4=3rd and so on
     * "-n" the number of memory channels into the CPU (hardware specific)
     *      - Most likely to be half the number of ram slots in your machine.
     *        We could count ram slots by "dmidecode -t 17 | grep -c 'Size:'"
     * Controls where in memory packets are stored and should spread across
     * the channels. We just use 1 to be safe.
     */

    /* Get the number of cpu cores in the system and use the last core */
    nb_cpu = sysconf(_SC_NPROCESSORS_ONLN);
    if (nb_cpu <= 0) {
        perror("sysconf(_SC_NPROCESSORS_ONLN) failed. Falling back to the first core.");
        nb_cpu = 1; /* fallback to the first core */
    }
    if (nb_cpu > RTE_MAX_LCORE)
        nb_cpu = RTE_MAX_LCORE;

    my_cpu = nb_cpu;
    /* This allows the user to specify the core - we would try to do this 
     * automatically but it's hard to tell that this is secondary
     * before running rte_eal_init(...). Currently we are limited to 1 
     * instance per core due to the way memory is allocated. */
    if (parse_pciaddr(uridata, &use_addr, &my_cpu) != 0) {
        snprintf(err, errlen, "Failed to parse URI");
        return -1;
    }

    snprintf(format_data->mempool_name, MEMPOOL_NAME_LEN,
                "libtrace_pool_%"PRIu32, (uint32_t) nb_cpu);

    if (!(my_cpu > 0 && my_cpu <= nb_cpu)) {
        snprintf(err, errlen, 
          "Intel DPDK - User defined a bad CPU number %"PRIu32" must be"
          " between 1 and %"PRIu32, (uint32_t) my_cpu, (uint32_t) nb_cpu);
        return -1;
    }

    /* Make our mask */
    snprintf(cpu_number, sizeof(cpu_number), "%x", 0x1 << (my_cpu - 1));


        /* Give the memory map a unique name */
        snprintf(mem_map, sizeof(mem_map), "libtrace-%d", (int) getpid());
    /* rte_eal_init it makes a call to getopt so we need to reset the 
     * global optind variable of getopt otherwise this fails */
    optind = 1;
    if ((ret = rte_eal_init(argc, argv)) < 0) {
        snprintf(err, errlen, 
          "Intel DPDK - Initialisation of EAL failed: %s", strerror(-ret));
        return -1;
    }
#if DEBUG
    dump_configuration();
#endif

#if DPDK_USE_PMD_INIT
    /* This registers all available NICs with Intel DPDK
     * These are not loaded until rte_eal_pci_probe() is called.
     */
    if ((ret = rte_pmd_init_all()) < 0) {
        snprintf(err, errlen, 
          "Intel DPDK - rte_pmd_init_all failed: %s", strerror(-ret));
        return -1;
    }
#endif

    /* Blacklist all ports besides the one that we want to use */
        if ((ret = blacklist_devices(format_data, &use_addr)) < 0) {
                snprintf(err, errlen, "Intel DPDK - Whitelisting PCI device failed,"
                         " are you sure the address is correct?: %s", strerror(-ret));
                return -1;
        }

    /* This loads DPDK drivers against all ports that are not blacklisted */
        if ((ret = rte_eal_pci_probe()) < 0) {
        snprintf(err, errlen, 
            "Intel DPDK - rte_eal_pci_probe failed: %s", strerror(-ret));
        return -1;
    }

    format_data->nb_ports = rte_eth_dev_count();

    if (format_data->nb_ports != 1) {
        snprintf(err, errlen, 
            "Intel DPDK - rte_eth_dev_count returned %d but it should be 1",
            format_data->nb_ports);
        return -1;
    }

    return 0;
}

static int dpdk_init_input (libtrace_t *libtrace) {
    char err[500];
    err[0] = 0;
    
    libtrace->format_data = (struct dpdk_format_data_t *)
                            malloc(sizeof(struct dpdk_format_data_t));
    FORMAT(libtrace)->port = 0; /* Always assume 1 port loaded */
    FORMAT(libtrace)->queue_id = 0; /* Single queue per port */
    FORMAT(libtrace)->nb_ports = 0;
    FORMAT(libtrace)->snaplen = 0; /* Use default */
    FORMAT(libtrace)->nb_rx_buf = NB_RX_MBUF;
    FORMAT(libtrace)->nb_tx_buf = MIN_NB_BUF;
    FORMAT(libtrace)->promisc = -1;
    FORMAT(libtrace)->pktmbuf_pool = NULL;
#if DPDK_USE_BLACKLIST
    FORMAT(libtrace)->nb_blacklist = 0;
#endif
    FORMAT(libtrace)->paused = DPDK_NEVER_STARTED;
    FORMAT(libtrace)->mempool_name[0] = 0;
#if HAS_HW_TIMESTAMPS_82580
    FORMAT(libtrace)->ts_first_sys = 0;
    FORMAT(libtrace)->ts_last_sys = 0;
    FORMAT(libtrace)->wrap_count = 0;
#endif

    if (dpdk_init_environment(libtrace->uridata, FORMAT(libtrace), err, sizeof(err)) != 0) {
        trace_set_err(libtrace, TRACE_ERR_INIT_FAILED, "%s", err);
        free(libtrace->format_data);
        libtrace->format_data = NULL;
        return -1;
    }
    return 0;
};

static int dpdk_init_output(libtrace_out_t *libtrace)
{
    char err[500];
    err[0] = 0;
    
    libtrace->format_data = (struct dpdk_format_data_t *)
                            malloc(sizeof(struct dpdk_format_data_t));
    FORMAT(libtrace)->port = 0; /* Always assume 1 port loaded */
    FORMAT(libtrace)->queue_id = 0; /* Single queue per port */
    FORMAT(libtrace)->nb_ports = 0;
    FORMAT(libtrace)->snaplen = 0; /* Use default */
    FORMAT(libtrace)->nb_rx_buf = MIN_NB_BUF;
    FORMAT(libtrace)->nb_tx_buf = NB_TX_MBUF;
    FORMAT(libtrace)->promisc = -1;
    FORMAT(libtrace)->pktmbuf_pool = NULL;
#if DPDK_USE_BLACKLIST
    FORMAT(libtrace)->nb_blacklist = 0;
#endif
    FORMAT(libtrace)->paused = DPDK_NEVER_STARTED;
    FORMAT(libtrace)->mempool_name[0] = 0;
#if HAS_HW_TIMESTAMPS_82580
    FORMAT(libtrace)->ts_first_sys = 0;
    FORMAT(libtrace)->ts_last_sys = 0;
    FORMAT(libtrace)->wrap_count = 0;
#endif

    if (dpdk_init_environment(libtrace->uridata, FORMAT(libtrace), err, sizeof(err)) != 0) {
        trace_set_err_out(libtrace, TRACE_ERR_INIT_FAILED, "%s", err);
        free(libtrace->format_data);
        libtrace->format_data = NULL;
        return -1;
    }
    return 0;
};

/**
 * Note here snaplen excludes the MAC checksum. Packets over
 * the requested snaplen will be dropped. (Excluding MAC checksum)
 * 
 * I.e the maximum size of a standard ethernet packet is 1518 (Including MAC checksum)
 * So to allow packets upto 1518 this would be set to 1514 and if GET_MAC_CRC_CHECKSUM
 * is set the maximum size of the returned packet would be 1518 otherwise
 * 1514 would be the largest size possibly returned.
 * 
 */
static int dpdk_config_input (libtrace_t *libtrace,
                                        trace_option_t option,
                                        void *data) {
    switch (option) {
        case TRACE_OPTION_SNAPLEN:
            /* Only support changing snaplen before a call to start is 
             * made */
            if (FORMAT(libtrace)->paused == DPDK_NEVER_STARTED)
                FORMAT(libtrace)->snaplen=*(int*)data;
            else
                return -1;
            return 0;
                case TRACE_OPTION_PROMISC:
                        FORMAT(libtrace)->promisc=*(int*)data;
            return 0;
        case TRACE_OPTION_FILTER:
            /* TODO filtering */
            break;
        case TRACE_OPTION_META_FREQ:
            break;
        case TRACE_OPTION_EVENT_REALTIME:
            break;
        /* Avoid default: so that future options will cause a warning
         * here to remind us to implement it, or flag it as
         * unimplementable
         */
    }

        /* Don't set an error - trace_config will try to deal with the
         * option and will set an error if it fails */
    return -1;
}

/* Can set jumbo frames/ or limit the size of a frame by setting both
 * max_rx_pkt_len and jumbo_frame. This can be limited to less than
 * 
 */
static struct rte_eth_conf port_conf = {
        .rxmode = {
                .split_hdr_size = 0,
                .header_split   = 0, /**< Header Split disabled */
                .hw_ip_checksum = 0, /**< IP checksum offload disabled */
                .hw_vlan_filter = 0, /**< VLAN filtering disabled */
                .jumbo_frame    = 0, /**< Jumbo Frame Support disabled */
        .max_rx_pkt_len = 0, /**< Max frame Size if Jumbo enabled */
#if GET_MAC_CRC_CHECKSUM
/* So it appears that if hw_strip_crc is turned off the driver will still
 * take this off. See line 955ish in lib/librte_pmd_e1000/igb_rxtx.c.
 * So if .hw_strip_crc=0 a valid CRC exists 4 bytes after the end of the
 * So lets just add it back on when we receive the packet.
 */
                .hw_strip_crc   = 0, /**< CRC stripped by hardware */
#else
/* By default strip the MAC checksum because it's a bit of a hack to
 * actually read these. And don't want to rely on disabling this to actualy
 * always cut off the checksum in the future
 */
        .hw_strip_crc   = 1, /**< CRC stripped by hardware */
#endif
        },
        .txmode = {
                .mq_mode = ETH_DCB_NONE,
        },
};

static const struct rte_eth_rxconf rx_conf = {
        .rx_thresh = {
                .pthresh = 8,/* RX_PTHRESH prefetch */
                .hthresh = 8,/* RX_HTHRESH host */
                .wthresh = 4,/* RX_WTHRESH writeback */
        },
    .rx_free_thresh = 0,
    .rx_drop_en = 0, /* Drop packets oldest packets if out of space */
};

static const struct rte_eth_txconf tx_conf = {
        .tx_thresh = {
        /**
         * TX_PTHRESH prefetch
         * Set on the NIC, if the number of unprocessed descriptors to queued on
         * the card fall below this try grab at least hthresh more unprocessed
         * descriptors.
         */
                .pthresh = 36,

        /* TX_HTHRESH host
         * Set on the NIC, the batch size to prefetch unprocessed tx descriptors.
         */
                .hthresh = 0,
        
        /* TX_WTHRESH writeback
         * Set on the NIC, the number of sent descriptors before writing back
         * status to confirm the transmission. This is done more efficiently as
         * a bulk DMA-transfer rather than writing one at a time.
         * Similar to tx_free_thresh however this is applied to the NIC, where
         * as tx_free_thresh is when DPDK will check these. This is extended
         * upon by tx_rs_thresh (10Gbit cards) which doesn't write all
         * descriptors rather only every n'th item, reducing DMA memory bandwidth.
         */
                .wthresh = 4,
        },

    /* Used internally by DPDK rather than passed to the NIC. The number of
     * packet descriptors to send before checking for any responses written
     * back (to confirm the transmission). Default = 32 if set to 0)
     */
        .tx_free_thresh = 0,

    /* This is the Report Status threshold, used by 10Gbit cards,
     * This signals the card to only write back status (such as 
     * transmission successful) after this minimum number of transmit
     * descriptors are seen. The default is 32 (if set to 0) however if set
     * to greater than 1 TX wthresh must be set to zero, because this is kindof
     * a replacement. See the dpdk programmers guide for more restrictions.
     */
        .tx_rs_thresh = 1,
};

/* Attach memory to the port and start the port or restart the port.
 */
static int dpdk_start_port (struct dpdk_format_data_t * format_data, char *err, int errlen){
    int ret; /* Check return values for errors */
    struct rte_eth_link link_info; /* Wait for link */
    
    /* Already started */
    if (format_data->paused == DPDK_RUNNING)
        return 0;

    /* First time started we need to alloc our memory, doing this here 
     * rather than in environment setup because we don't have snaplen then */
    if (format_data->paused == DPDK_NEVER_STARTED) {
        if (format_data->snaplen == 0) {
            format_data->snaplen = RX_MBUF_SIZE;
            port_conf.rxmode.jumbo_frame = 0;
            port_conf.rxmode.max_rx_pkt_len = 0;
        } else {
            /* Use jumbo frames */
            port_conf.rxmode.jumbo_frame = 1;
            port_conf.rxmode.max_rx_pkt_len = format_data->snaplen;
        }

        /* This is additional overhead so make sure we allow space for this */
#if GET_MAC_CRC_CHECKSUM
        format_data->snaplen += ETHER_CRC_LEN;
#endif
#if HAS_HW_TIMESTAMPS_82580
        format_data->snaplen += sizeof(struct hw_timestamp_82580);
#endif

        /* Create the mbuf pool, which is the place our packets are allocated
         * from - TODO figure out if there is is a free function (I cannot see one) 
         * NOTE: RX queue requires nb_packets + 1 otherwise it fails to 
         * allocate however that extra 1 packet is not used. 
         * (I assume <= vs < error some where in DPDK code)
         * TX requires nb_tx_buffers + 1 in the case the queue is full 
         * so that will fill the new buffer and wait until slots in the
         * ring become available.
         */
#if DEBUG
    fprintf(stderr, "Creating mempool named %s\n", format_data->mempool_name);
#endif
        format_data->pktmbuf_pool =
            rte_mempool_create(format_data->mempool_name,
                       format_data->nb_rx_buf + format_data->nb_tx_buf + 1,
                       format_data->snaplen + sizeof(struct rte_mbuf) 
                                        + RTE_PKTMBUF_HEADROOM,
                       8, sizeof(struct rte_pktmbuf_pool_private),
                       rte_pktmbuf_pool_init, NULL, rte_pktmbuf_init, NULL,
                       0, MEMPOOL_F_SP_PUT | MEMPOOL_F_SC_GET);

        if (format_data->pktmbuf_pool == NULL) {
            snprintf(err, errlen, "Intel DPDK - Initialisation of mbuf "
                        "pool failed: %s", strerror(rte_errno));
            return -1;
        }
    }
    
    /* ----------- Now do the setup for the port mapping ------------ */
    /* Order of calls must be 
     * rte_eth_dev_configure()
     * rte_eth_tx_queue_setup()
     * rte_eth_rx_queue_setup()
     * rte_eth_dev_start()
     * other rte_eth calls
     */
    
    /* This must be called first before another *eth* function
     * 1 rx, 1 tx queue, port_conf sets checksum stripping etc */
    ret = rte_eth_dev_configure(format_data->port, 1, 1, &port_conf);
    if (ret < 0) {
        snprintf(err, errlen, "Intel DPDK - Cannot configure device port"
                            " %"PRIu8" : %s", format_data->port,
                            strerror(-ret));
        return -1;
    }
    /* Initialise the TX queue a minimum value if using this port for
     * receiving. Otherwise a larger size if writing packets.
     */
    ret = rte_eth_tx_queue_setup(format_data->port, format_data->queue_id,
                        format_data->nb_tx_buf, SOCKET_ID_ANY, &tx_conf);
    if (ret < 0) {
        snprintf(err, errlen, "Intel DPDK - Cannot configure TX queue on port"
                            " %"PRIu8" : %s", format_data->port,
                            strerror(-ret));
        return -1;
    }
    /* Initialise the RX queue with some packets from memory */
    ret = rte_eth_rx_queue_setup(format_data->port, format_data->queue_id,
                            format_data->nb_rx_buf, SOCKET_ID_ANY, 
                            &rx_conf, format_data->pktmbuf_pool);
    if (ret < 0) {
        snprintf(err, errlen, "Intel DPDK - Cannot configure RX queue on port"
                    " %"PRIu8" : %s", format_data->port,
                    strerror(-ret));
        return -1;
    }
    
    /* Start device */
    ret = rte_eth_dev_start(format_data->port);
    if (ret < 0) {
        snprintf(err, errlen, "Intel DPDK - rte_eth_dev_start failed : %s",
                    strerror(-ret));
        return -1;
    }

    /* Default promiscuous to on */
    if (format_data->promisc == -1)
        format_data->promisc = 1;
    
    if (format_data->promisc == 1)
        rte_eth_promiscuous_enable(format_data->port);
    else
        rte_eth_promiscuous_disable(format_data->port);
    
    /* Wait for the link to come up */
    rte_eth_link_get(format_data->port, &link_info);
#if DEBUG
    fprintf(stderr, "Link status is %d %d %d\n", (int) link_info.link_status,
            (int) link_info.link_duplex, (int) link_info.link_speed);
#endif

    /* We have now successfully started/unpaused */
    format_data->paused = DPDK_RUNNING;
    
    return 0;
}

static int dpdk_start_input (libtrace_t *libtrace) {
    char err[500];
    err[0] = 0;

    if (dpdk_start_port(FORMAT(libtrace), err, sizeof(err)) != 0) {
        trace_set_err(libtrace, TRACE_ERR_INIT_FAILED, "%s", err);
        free(libtrace->format_data);
        libtrace->format_data = NULL;
        return -1;
    }
    return 0;
}

static int dpdk_start_output(libtrace_out_t *libtrace)
{
    char err[500];
    err[0] = 0;
    
    if (dpdk_start_port(FORMAT(libtrace), err, sizeof(err)) != 0) {
        trace_set_err_out(libtrace, TRACE_ERR_INIT_FAILED, "%s", err);
        free(libtrace->format_data);
        libtrace->format_data = NULL;
        return -1;
    }
    return 0;
}

static int dpdk_pause_input(libtrace_t * libtrace){
    /* This stops the device, but can be restarted using rte_eth_dev_start() */
    if (FORMAT(libtrace)->paused == DPDK_RUNNING) {
#if DEBUG      
        fprintf(stderr, "Pausing port\n");
#endif
        rte_eth_dev_stop(FORMAT(libtrace)->port);
        FORMAT(libtrace)->paused = DPDK_PAUSED;
        /* If we pause it the driver will be reset and likely our counter */
#if HAS_HW_TIMESTAMPS_82580
        FORMAT(libtrace)->ts_first_sys = 0;
        FORMAT(libtrace)->ts_last_sys = 0;
#endif
    }
    return 0;
}

static int dpdk_write_packet(libtrace_out_t *trace, 
                libtrace_packet_t *packet){
    struct rte_mbuf* m_buff[1];
    
    int wirelen = trace_get_wire_length(packet);
    int caplen = trace_get_capture_length(packet);
    
    /* Check for a checksum and remove it */
    if (trace_get_link_type(packet) == TRACE_TYPE_ETH &&
                                            wirelen == caplen)
        caplen -= ETHER_CRC_LEN;

    m_buff[0] = rte_pktmbuf_alloc(FORMAT(trace)->pktmbuf_pool);
    if (m_buff[0] == NULL) {
        trace_set_err_out(trace, errno, "Cannot get an empty packet buffer");
        return -1;
    } else {
        int ret;
        memcpy(rte_pktmbuf_append(m_buff[0], caplen), packet->payload, caplen);
        do {
            ret = rte_eth_tx_burst(FORMAT(trace)->queue_id, FORMAT(trace)->port, m_buff, 1);
        } while (ret != 1);
    }

    return 0;
}

static int dpdk_fin_input(libtrace_t * libtrace) {
    /* Free our memory structures */
    if (libtrace->format_data != NULL) {
        /* Close the device completely, device cannot be restarted */
        if (FORMAT(libtrace)->port != 0xFF)
            rte_eth_dev_close(FORMAT(libtrace)->port);
        /* filter here if we used it */
                free(libtrace->format_data);
        }

    /* Revert to the original PCI drivers */
    /* No longer in DPDK
    rte_eal_pci_exit(); */
    return 0;
}


static int dpdk_fin_output(libtrace_out_t * libtrace) {
    /* Free our memory structures */
    if (libtrace->format_data != NULL) {
        /* Close the device completely, device cannot be restarted */
        if (FORMAT(libtrace)->port != 0xFF)
            rte_eth_dev_close(FORMAT(libtrace)->port);
        /* filter here if we used it */
                free(libtrace->format_data);
        }

    /* Revert to the original PCI drivers */
    /* No longer in DPDK
    rte_eal_pci_exit(); */
    return 0;
}

/** 
 * Get the start of additional header that we added to a packet.
 */
static inline struct dpdk_addt_hdr * get_addt_hdr (const libtrace_packet_t *packet) {
    uint8_t *hdrsize;
    assert(packet);
    assert(packet->buffer);
    hdrsize = (uint8_t *) MBUF_PKTDATA(packet->buffer);
    /* The byte before the original packet data denotes the size in bytes
     * of our additional header that we added sits before the 'size byte' */
    hdrsize--;
    return (struct dpdk_addt_hdr *) (hdrsize - *hdrsize);
}

static int dpdk_get_capture_length (const libtrace_packet_t *packet) {
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    return hdr->cap_len;
}

static size_t dpdk_set_capture_length(libtrace_packet_t *packet, size_t size) {
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    if (size > hdr->cap_len) {
        /* Cannot make a packet bigger */
                return trace_get_capture_length(packet);
        }

    /* Reset the cached capture length first*/
    packet->capture_length = -1;
    hdr->cap_len = (uint32_t) size;
        return trace_get_capture_length(packet);
}

static int dpdk_get_wire_length (const libtrace_packet_t *packet) {
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    int org_cap_size; /* The original capture size */
    if (hdr->flags & INCLUDES_HW_TIMESTAMP) {
        org_cap_size = (int) rte_pktmbuf_pkt_len(MBUF(packet->buffer)) -
                            (MBUF_PKTDATA(packet->buffer) - (char *) hdr) -
                            sizeof(struct hw_timestamp_82580);
    } else {
        org_cap_size = (int) rte_pktmbuf_pkt_len(MBUF(packet->buffer)) -
                            (MBUF_PKTDATA(packet->buffer) - (char *) hdr);
    }
    if (hdr->flags & INCLUDES_CHECKSUM) {
        return org_cap_size;
    } else {
        /* DPDK packets are always TRACE_TYPE_ETH packets */
        return org_cap_size + ETHER_CRC_LEN;
    }
}
static int dpdk_get_framing_length (const libtrace_packet_t *packet) {
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    if (hdr->flags & INCLUDES_HW_TIMESTAMP)
        return sizeof(struct rte_mbuf) + RTE_PKTMBUF_HEADROOM +
                sizeof(struct hw_timestamp_82580);
    else
        return sizeof(struct rte_mbuf) + RTE_PKTMBUF_HEADROOM;
}

static int dpdk_prepare_packet(libtrace_t *libtrace UNUSED,
                libtrace_packet_t *packet, void *buffer,
                libtrace_rt_types_t rt_type, uint32_t flags) {
    assert(packet);
    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;

    /* Don't use pktmbuf_mtod will fail if the packet is a copy */
    packet->payload = (char *)buffer + dpdk_get_framing_length(packet);
    packet->type = rt_type;
    return 0;
}

/*
 * Does any extra preperation to a captured packet.
 * This includes adding our extra header to it with the timestamp
 */
static inline int dpdk_ready_pkt(libtrace_t *libtrace, libtrace_packet_t *packet,
                                                        struct rte_mbuf* pkt){
    uint8_t * hdr_size;
    struct dpdk_addt_hdr *hdr;
#if HAS_HW_TIMESTAMPS_82580
    struct hw_timestamp_82580 *hw_ts;
    struct timeval cur_sys_time;
    uint64_t cur_sys_time_ns;
    uint64_t estimated_wraps;
    
    /* Using gettimeofday because it's most likely to be a vsyscall
     * We don't want to slow down anything with systemcalls we dont need
     * accauracy */
    gettimeofday(&cur_sys_time, NULL);
#else
# if USE_CLOCK_GETTIME
    struct timespec cur_sys_time;
    
    /* This looks terrible and I feel bad doing it. But it's OK 
     * on new kernels, because this is a vsyscall */
    clock_gettime(CLOCK_REALTIME, &cur_sys_time);
# else
    struct timeval cur_sys_time;
    /* Should be a vsyscall */
    gettimeofday(&cur_sys_time, NULL);
# endif
#endif

    /* Record the size of our header */
    hdr_size = (uint8_t *) rte_pktmbuf_prepend(pkt, sizeof(uint8_t));
    *hdr_size = sizeof(struct dpdk_addt_hdr);
    /* Now put our header in front of that size */
    hdr = (struct dpdk_addt_hdr *) rte_pktmbuf_prepend(pkt, sizeof(struct dpdk_addt_hdr));
    memset(hdr, 0, sizeof(struct dpdk_addt_hdr));
    
#if GET_MAC_CRC_CHECKSUM
    /* Add back in the CRC sum */
    pkt->pkt.pkt_len += ETHER_CRC_LEN;
    pkt->pkt.data_len += ETHER_CRC_LEN;
    hdr->flags |= INCLUDES_CHECKSUM;
#endif

#if HAS_HW_TIMESTAMPS_82580
    /* Taken from igb_ptp.c part of Intel Linux drivers (Good example code)
     *
     *        +----------+---+   +--------------+
     *  82580 |    24    | 8 |   |      32      |
     *        +----------+---+   +--------------+
     *          reserved  \______ 40 bits _____/
     * 
     * The 40 bit 82580 SYSTIM overflows every
     *   2^40 * 10^-9 /  60  = 18.3 minutes.
     * 
     * NOTE picture is in Big Endian order, in memory it's acutally in Little
     * Endian (for the full 64 bits) i.e. picture is mirrored
     */
    
    /* The timestamp is sitting before our packet and is included in pkt_len */
    hdr->flags |= INCLUDES_HW_TIMESTAMP;
    hw_ts = (struct hw_timestamp_82580 *) MBUF_PKTDATA(pkt);
    
    /* Despite what the documentation says this is in Little 
     * Endian byteorder. Mask the reserved section out.
     */
    hdr->timestamp = le64toh(hw_ts->timestamp) & 
                ~(((~0ull)>>TS_NBITS_82580)<<TS_NBITS_82580);
                
    cur_sys_time_ns = TV_TO_NS(cur_sys_time);
    if (unlikely(FORMAT(libtrace)->ts_first_sys == 0)) {
        FORMAT(libtrace)->ts_first_sys = cur_sys_time_ns - hdr->timestamp;
        FORMAT(libtrace)->ts_last_sys = FORMAT(libtrace)->ts_first_sys;
    }
    
    /* This will have serious problems if packets aren't read quickly
     * that is within a couple of seconds because our clock cycles every
     * 18 seconds */
    estimated_wraps = (cur_sys_time_ns - FORMAT(libtrace)->ts_last_sys)
                            / (1ull<<TS_NBITS_82580);
    
    /* Estimated_wraps gives the number of times the counter should have
     * wrapped (however depending on value last time it could have wrapped
     * twice more (if hw clock is close to its max value) or once less (allowing
     * for a bit of variance between hw and sys clock). But if the clock
     * shouldn't have wrapped once then don't allow it to go backwards in time */
    if (unlikely(estimated_wraps >= 2)) {
        /* 2 or more wrap arounds add all but the very last wrap */
        FORMAT(libtrace)->wrap_count += estimated_wraps - 1;
    }
    
    /* Set the timestamp to the lowest possible value we're considering */
    hdr->timestamp += FORMAT(libtrace)->ts_first_sys +
                        FORMAT(libtrace)->wrap_count * (1ull<<TS_NBITS_82580);
    
    /* In most runs only the first if() will need evaluating - i.e our
     * estimate is correct. */
    if (unlikely(!WITHIN_VARIANCE(cur_sys_time_ns,
                                hdr->timestamp, MAXSKEW_82580))) {
        /* Failed to match estimated_wraps-1 (or estimated_wraps in ==0 case) */
        FORMAT(libtrace)->wrap_count++;
        hdr->timestamp += (1ull<<TS_NBITS_82580);
        if (!WITHIN_VARIANCE(cur_sys_time_ns,
                                hdr->timestamp, MAXSKEW_82580)) {
            /* Failed to match estimated_wraps */
            FORMAT(libtrace)->wrap_count++;
            hdr->timestamp += (1ull<<TS_NBITS_82580);
            if (!WITHIN_VARIANCE(cur_sys_time_ns,
                                hdr->timestamp, MAXSKEW_82580)) {
                if (estimated_wraps == 0) {
                    /* 0 case Failed to match estimated_wraps+2 */
                    printf("WARNING - Hardware Timestamp failed to"
                                            " match using systemtime!\n");
                    hdr->timestamp = cur_sys_time_ns;
                } else {
                    /* Failed to match estimated_wraps+1 */
                    FORMAT(libtrace)->wrap_count++;
                    hdr->timestamp += (1ull<<TS_NBITS_82580);
                    if (!WITHIN_VARIANCE(cur_sys_time_ns,
                                hdr->timestamp, MAXSKEW_82580)) {
                        /* Failed to match estimated_wraps+2 */
                        printf("WARNING - Hardware Timestamp failed to"
                                            " match using systemtime!!\n");
                    }
                }
            }
        }
    }

    /* Log our previous for the next loop */
    FORMAT(libtrace)->ts_last_sys = TV_TO_NS(cur_sys_time);

#else
# if USE_CLOCK_GETTIME
    hdr->timestamp = TS_TO_NS(cur_sys_time);
# else
    hdr->timestamp = TV_TO_NS(cur_sys_time);
# endif
#endif

    /* Intels samples prefetch into level 0 cache lets assume it is a good
     * idea and do the same */
    rte_prefetch0(rte_pktmbuf_mtod(pkt, void *));
    packet->buffer = pkt;
    dpdk_prepare_packet(libtrace, packet, packet->buffer, packet->type, 0);

    /* Set our capture length for the first time */
    hdr->cap_len = dpdk_get_wire_length(packet);
    if (!(hdr->flags & INCLUDES_CHECKSUM)) {
        hdr->cap_len -= ETHER_CRC_LEN;
    }
    

    return dpdk_get_framing_length(packet) +
                        dpdk_get_capture_length(packet);
}

static int dpdk_read_packet (libtrace_t *libtrace, libtrace_packet_t *packet) {
    int nb_rx; /* Number of rx packets we've recevied */
    struct rte_mbuf* pkts_burst[1]; /* Array of 1 pointer(s) */

    /* Free the last packet buffer */
    if (packet->buffer != NULL) {
        /* Buffer is owned by DPDK */
        if ( packet->buf_control == TRACE_CTRL_EXTERNAL ) {
            rte_pktmbuf_free(packet->buffer);
            packet->buffer = NULL;
        } else
        /* Buffer is owned by packet i.e. has been malloc'd */
        if (packet->buf_control == TRACE_CTRL_PACKET) {
            free(packet->buffer);
            packet->buffer = NULL;
        }
    }
    
    packet->buf_control = TRACE_CTRL_EXTERNAL;
    packet->type = TRACE_RT_DATA_DPDK;
    
    /* Wait for a packet */
    while (1) {
        /* Poll for a single packet */
        nb_rx = rte_eth_rx_burst(FORMAT(libtrace)->port,
                            FORMAT(libtrace)->queue_id, pkts_burst, 1);        
        if (nb_rx > 0) { /* Got a packet - otherwise we keep spining */
            return dpdk_ready_pkt(libtrace, packet, pkts_burst[0]);
        }
    }
    
    /* We'll never get here - but if we did it would be bad */
    return -1;
}

static struct timeval dpdk_get_timeval (const libtrace_packet_t *packet) {
    struct timeval tv;
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    
    tv.tv_sec = hdr->timestamp / (uint64_t) 1000000000;
    tv.tv_usec = (hdr->timestamp % (uint64_t) 1000000000) / 1000;
    return tv;
}

static struct timespec dpdk_get_timespec (const libtrace_packet_t *packet) {
    struct timespec ts;
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    
    ts.tv_sec = hdr->timestamp / (uint64_t) 1000000000;
    ts.tv_nsec = hdr->timestamp % (uint64_t) 1000000000;
    return ts;
}

static libtrace_linktype_t dpdk_get_link_type (const libtrace_packet_t *packet UNUSED) {
    return TRACE_TYPE_ETH; /* Always ethernet until proven otherwise */
}

static libtrace_direction_t dpdk_get_direction (const libtrace_packet_t *packet) {
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    return (libtrace_direction_t) hdr->direction;
}

static libtrace_direction_t dpdk_set_direction(libtrace_packet_t *packet, libtrace_direction_t direction) {
    struct dpdk_addt_hdr * hdr = get_addt_hdr(packet);
    hdr->direction = (uint8_t) direction;
    return (libtrace_direction_t) hdr->direction;
}

/*
 * NOTE: Drops could occur for other reasons than running out of buffer
 * space. Such as failed MAC checksums and oversized packets.
 */
static uint64_t dpdk_get_dropped_packets (libtrace_t *trace) {
    struct rte_eth_stats stats = {0};
    
    if (trace->format_data == NULL || FORMAT(trace)->port == 0xFF)
        return UINT64_MAX;
    /* Grab the current stats */
    rte_eth_stats_get(FORMAT(trace)->port, &stats);
    
    /* Get the drop counter */
    return (uint64_t) stats.ierrors;
}

static uint64_t dpdk_get_captured_packets (libtrace_t *trace) {
    struct rte_eth_stats stats = {0};
    
    if (trace->format_data == NULL || FORMAT(trace)->port == 0xFF)
        return UINT64_MAX;
    /* Grab the current stats */
    rte_eth_stats_get(FORMAT(trace)->port, &stats);
    
    /* Get the drop counter */
    return (uint64_t) stats.ipackets;
}

/*
 * This is the number of packets filtered by the NIC
 * and maybe ahead of number read using libtrace.
 * 
 * XXX we are yet to implement any filtering, but if it was this should
 * get the result. So this will just return 0 for now.
 */
static uint64_t dpdk_get_filtered_packets (libtrace_t *trace) {
    struct rte_eth_stats stats = {0};
    
    if (trace->format_data == NULL || FORMAT(trace)->port == 0xFF)
        return UINT64_MAX;
    /* Grab the current stats */
    rte_eth_stats_get(FORMAT(trace)->port, &stats);
    
    /* Get the drop counter */
    return (uint64_t) stats.fdirmiss;
}

/* Attempts to read a packet in a non-blocking fashion. If one is not
 * available a SLEEP event is returned. We do not have the ability to
 * create a select()able file descriptor in DPDK.
 */
static libtrace_eventobj_t dpdk_trace_event(libtrace_t *trace,
                                        libtrace_packet_t *packet) {
    libtrace_eventobj_t event = {0,0,0.0,0};
    int nb_rx; /* Number of receive packets we've read */
    struct rte_mbuf* pkts_burst[1]; /* Array of 1 pointer(s) to rx buffers */
    
    do {
    
        /* See if we already have a packet waiting */
        nb_rx = rte_eth_rx_burst(FORMAT(trace)->port,
                        FORMAT(trace)->queue_id, pkts_burst, 1);
        
        if (nb_rx > 0) {
            /* Free the last packet buffer */
            if (packet->buffer != NULL) {
                /* Buffer is owned by DPDK */
                if ( packet->buf_control == TRACE_CTRL_EXTERNAL ) {
                    rte_pktmbuf_free(packet->buffer);
                    packet->buffer = NULL;
                } else
                /* Buffer is owned by packet i.e. has been malloc'd */
                if (packet->buf_control == TRACE_CTRL_PACKET) {
                    free(packet->buffer);
                    packet->buffer = NULL;
                }
            }
            
            packet->buf_control = TRACE_CTRL_EXTERNAL;
            packet->type = TRACE_RT_DATA_DPDK;
            event.type = TRACE_EVENT_PACKET;
            event.size = dpdk_ready_pkt(trace, packet, pkts_burst[0]);
            
            /* XXX - Check this passes the filter trace_read_packet normally
             * does this for us but this wont */
            if (trace->filter) {
                if (!trace_apply_filter(trace->filter, packet)) {
                    /* Failed the filter so we loop for another packet */
                    trace->filtered_packets ++;
                    continue;
                }
            }
            trace->accepted_packets ++;
        } else {
            /* We only want to sleep for a very short time - we are non-blocking */
            event.type = TRACE_EVENT_SLEEP;
            event.seconds = 0.0001;
            event.size = 0;
        }
        
        /* If we get here we have our event */
        break;
    } while (1);

    return event;
}


static void dpdk_help(void) {
    printf("dpdk format module: $Revision: 1752 $\n");
    printf("Supported input URIs:\n");
    printf("\tdpdk:<domain:bus:devid.func>-<coreid>\n");
    printf("\tThe -<coreid> is optional \n");
    printf("\t e.g. dpdk:0000:01:00.1\n");
    printf("\t e.g. dpdk:0000:01:00.1-2 (Use the second CPU core)\n\n");
    printf("\t By default the last CPU core is used if not otherwise specified.\n");
    printf("\t Only a single libtrace instance of dpdk can use the same CPU core.\n");
    printf("\t Support for multiple simultaneous instances of dpdk format is currently limited.\n");
    printf("\n");
    printf("Supported output URIs:\n");
    printf("\tSame format as the input URI.\n");
    printf("\t e.g. dpdk:0000:01:00.1\n");
    printf("\t e.g. dpdk:0000:01:00.1-2 (Use the second CPU core)\n");
    printf("\n");
}

 static struct libtrace_format_t dpdk = {
        "dpdk",
        "$Id: format_dpdk.c 1805 2013-03-08 02:01:35Z salcock $",
        TRACE_FORMAT_DPDK,
        NULL,                   /* probe filename */
        NULL,                               /* probe magic */
        dpdk_init_input,            /* init_input */
        dpdk_config_input,          /* config_input */
        dpdk_start_input,           /* start_input */
        dpdk_pause_input,           /* pause_input */
        dpdk_init_output,           /* init_output */
        NULL,                               /* config_output */
        dpdk_start_output,          /* start_ouput */
        dpdk_fin_input,             /* fin_input */
        dpdk_fin_output,        /* fin_output */
        dpdk_read_packet,           /* read_packet */
        dpdk_prepare_packet,    /* prepare_packet */
        NULL,                               /* fin_packet */
        dpdk_write_packet,          /* write_packet */
        dpdk_get_link_type,         /* get_link_type */
        dpdk_get_direction,         /* get_direction */
        dpdk_set_direction,         /* set_direction */
        NULL,                               /* get_erf_timestamp */
        dpdk_get_timeval,           /* get_timeval */
        dpdk_get_timespec,          /* get_timespec */
        NULL,                               /* get_seconds */
        NULL,                               /* seek_erf */
        NULL,                               /* seek_timeval */
        NULL,                               /* seek_seconds */
        dpdk_get_capture_length,/* get_capture_length */
        dpdk_get_wire_length,   /* get_wire_length */
        dpdk_get_framing_length,/* get_framing_length */
        dpdk_set_capture_length,/* set_capture_length */
        NULL,                               /* get_received_packets */
        dpdk_get_filtered_packets,/* get_filtered_packets */
        dpdk_get_dropped_packets,/* get_dropped_packets */
    dpdk_get_captured_packets,/* get_captured_packets */
        NULL,                       /* get_fd */
        dpdk_trace_event,               /* trace_event */
    dpdk_help,              /* help */
        NULL
};

void dpdk_constructor(void) {
        register_format(&dpdk);
}