suricata/src/app-layer-dnp3.c

/* Copyright (C) 2015-2025 Open Information Security Foundation
 *
 * You can copy, redistribute or modify this Program under the terms of
 * the GNU General Public License version 2 as published by the Free
 * Software Foundation.
 *
 * This program 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
 * version 2 along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

/**
 * \file
 *
 * DNP3 protocol implementation
 */

#include "suricata-common.h"
#include "suricata.h"
#include "util-unittest.h"

#include "util-spm-bs.h"
#include "util-enum.h"

#include "app-layer.h"
#include "app-layer-protos.h"
#include "app-layer-parser.h"
#include "app-layer-detect-proto.h"
#include "app-layer-events.h"

#include "app-layer-dnp3.h"
#include "app-layer-dnp3-objects.h"

/* Default number of unreplied requests to be considered a flood. */
#define DNP3_DEFAULT_REQ_FLOOD_COUNT 500

#define DNP3_DEFAULT_PORT "20000"

/* Expected values for the start bytes. */
#define DNP3_START_BYTE0  0x05
#define DNP3_START_BYTE1  0x64

/* Minimum length for a DNP3 frame. */
#define DNP3_MIN_LEN      5

/* Length of each CRC. */
#define DNP3_CRC_LEN      2

/* DNP3 block size. After the link header a CRC is inserted after
 * after 16 bytes of data. */
#define DNP3_BLOCK_SIZE   16

/* Maximum transport layer sequence number. */
#define DNP3_MAX_TRAN_SEQNO 64

/* Maximum application layer sequence number. */
// unused #define DNP3_MAX_APP_SEQNO  16

/* The number of bytes in the header that are counted as part of the
 * header length field. */
#define DNP3_LINK_HDR_LEN 5

/* Link function codes. */
enum {
    DNP3_LINK_FC_CONFIRMED_USER_DATA = 3,
    DNP3_LINK_FC_UNCONFIRMED_USER_DATA
};

/* Reserved addresses. */
// unused #define DNP3_RESERVED_ADDR_MIN 0xfff0
// unused #define DNP3_RESERVED_ADDR_MAX 0xfffb

/* Source addresses must be < 0xfff0. */
// unused #define DNP3_SRC_ADDR_MAX 0xfff0

/* Extract the prefix code from the object qualifier. */
#define DNP3_OBJ_PREFIX(x) ((x >> 4) & 0x7)

/* Extract the range code from the object qualifier. */
#define DNP3_OBJ_RANGE(x)  (x & 0xf)

/* Decoder event map. */
SCEnumCharMap dnp3_decoder_event_table[] = {
    {"FLOODED",           DNP3_DECODER_EVENT_FLOODED},
    {"LEN_TOO_SMALL",     DNP3_DECODER_EVENT_LEN_TOO_SMALL},
    {"BAD_LINK_CRC",      DNP3_DECODER_EVENT_BAD_LINK_CRC},
    {"BAD_TRANSPORT_CRC", DNP3_DECODER_EVENT_BAD_TRANSPORT_CRC},
    {"MALFORMED",         DNP3_DECODER_EVENT_MALFORMED},
    {"UNKNOWN_OBJECT",    DNP3_DECODER_EVENT_UNKNOWN_OBJECT},
    {NULL, -1},
};

/* Calculate the next transport sequence number. */
#define NEXT_TH_SEQNO(current) ((current + 1) % DNP3_MAX_TRAN_SEQNO)

/* CRC table generated by pycrc - http://github.com/tpircher/pycrc.
 * - Polynomial: 0x3d65. */
static const uint16_t crc_table[256] = {
    0x0000, 0x365e, 0x6cbc, 0x5ae2, 0xd978, 0xef26, 0xb5c4, 0x839a,
    0xff89, 0xc9d7, 0x9335, 0xa56b, 0x26f1, 0x10af, 0x4a4d, 0x7c13,
    0xb26b, 0x8435, 0xded7, 0xe889, 0x6b13, 0x5d4d, 0x07af, 0x31f1,
    0x4de2, 0x7bbc, 0x215e, 0x1700, 0x949a, 0xa2c4, 0xf826, 0xce78,
    0x29af, 0x1ff1, 0x4513, 0x734d, 0xf0d7, 0xc689, 0x9c6b, 0xaa35,
    0xd626, 0xe078, 0xba9a, 0x8cc4, 0x0f5e, 0x3900, 0x63e2, 0x55bc,
    0x9bc4, 0xad9a, 0xf778, 0xc126, 0x42bc, 0x74e2, 0x2e00, 0x185e,
    0x644d, 0x5213, 0x08f1, 0x3eaf, 0xbd35, 0x8b6b, 0xd189, 0xe7d7,
    0x535e, 0x6500, 0x3fe2, 0x09bc, 0x8a26, 0xbc78, 0xe69a, 0xd0c4,
    0xacd7, 0x9a89, 0xc06b, 0xf635, 0x75af, 0x43f1, 0x1913, 0x2f4d,
    0xe135, 0xd76b, 0x8d89, 0xbbd7, 0x384d, 0x0e13, 0x54f1, 0x62af,
    0x1ebc, 0x28e2, 0x7200, 0x445e, 0xc7c4, 0xf19a, 0xab78, 0x9d26,
    0x7af1, 0x4caf, 0x164d, 0x2013, 0xa389, 0x95d7, 0xcf35, 0xf96b,
    0x8578, 0xb326, 0xe9c4, 0xdf9a, 0x5c00, 0x6a5e, 0x30bc, 0x06e2,
    0xc89a, 0xfec4, 0xa426, 0x9278, 0x11e2, 0x27bc, 0x7d5e, 0x4b00,
    0x3713, 0x014d, 0x5baf, 0x6df1, 0xee6b, 0xd835, 0x82d7, 0xb489,
    0xa6bc, 0x90e2, 0xca00, 0xfc5e, 0x7fc4, 0x499a, 0x1378, 0x2526,
    0x5935, 0x6f6b, 0x3589, 0x03d7, 0x804d, 0xb613, 0xecf1, 0xdaaf,
    0x14d7, 0x2289, 0x786b, 0x4e35, 0xcdaf, 0xfbf1, 0xa113, 0x974d,
    0xeb5e, 0xdd00, 0x87e2, 0xb1bc, 0x3226, 0x0478, 0x5e9a, 0x68c4,
    0x8f13, 0xb94d, 0xe3af, 0xd5f1, 0x566b, 0x6035, 0x3ad7, 0x0c89,
    0x709a, 0x46c4, 0x1c26, 0x2a78, 0xa9e2, 0x9fbc, 0xc55e, 0xf300,
    0x3d78, 0x0b26, 0x51c4, 0x679a, 0xe400, 0xd25e, 0x88bc, 0xbee2,
    0xc2f1, 0xf4af, 0xae4d, 0x9813, 0x1b89, 0x2dd7, 0x7735, 0x416b,
    0xf5e2, 0xc3bc, 0x995e, 0xaf00, 0x2c9a, 0x1ac4, 0x4026, 0x7678,
    0x0a6b, 0x3c35, 0x66d7, 0x5089, 0xd313, 0xe54d, 0xbfaf, 0x89f1,
    0x4789, 0x71d7, 0x2b35, 0x1d6b, 0x9ef1, 0xa8af, 0xf24d, 0xc413,
    0xb800, 0x8e5e, 0xd4bc, 0xe2e2, 0x6178, 0x5726, 0x0dc4, 0x3b9a,
    0xdc4d, 0xea13, 0xb0f1, 0x86af, 0x0535, 0x336b, 0x6989, 0x5fd7,
    0x23c4, 0x159a, 0x4f78, 0x7926, 0xfabc, 0xcce2, 0x9600, 0xa05e,
    0x6e26, 0x5878, 0x029a, 0x34c4, 0xb75e, 0x8100, 0xdbe2, 0xedbc,
    0x91af, 0xa7f1, 0xfd13, 0xcb4d, 0x48d7, 0x7e89, 0x246b, 0x1235
};

/**
 * \brief Compute the CRC for a buffer.
 *
 * \param buf Buffer to create CRC from.
 * \param len Length of buffer (number of bytes to use for CRC).

 */
static uint16_t DNP3ComputeCRC(const uint8_t *buf, uint32_t len)
{
    const uint8_t *byte = buf;
    uint16_t crc = 0;
    int idx;

    while (len--) {
        idx = (crc ^ *byte) & 0xff;
        crc = (crc_table[idx] ^ (crc >> 8)) & 0xffff;
        byte++;
    }

    return ~crc & 0xffff;
}

/**
 * \brief Check the CRC of a block.
 *
 * \param block The block of data with CRC to be checked.
 * \param len The size of the data block.
 *
 * \retval 1 if CRC is OK, otherwise 0.
 */
static int DNP3CheckCRC(const uint8_t *block, uint32_t len)
{
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
    return 1;
#endif
    uint32_t crc_offset;
    uint16_t crc;

    /* Need at least one byte plus the CRC. */
    if (len < DNP3_CRC_LEN + 1) {
        return 0;
    }

    crc_offset = len - DNP3_CRC_LEN;
    crc = DNP3ComputeCRC(block, len - DNP3_CRC_LEN);
    if (((crc & 0xff) == block[crc_offset]) &&
        ((crc >> 8) == block[crc_offset + 1])) {
        return 1;
    }

    return 0;
}

/**
 * \brief Check the CRC of the link header.
 *
 * \param header Point to the link header.
 *
 * \retval 1 if header CRC is OK, otherwise 0.
 */
static int DNP3CheckLinkHeaderCRC(const DNP3LinkHeader *header)
{
    return DNP3CheckCRC((uint8_t *)header, sizeof(DNP3LinkHeader));
}

/**
 * \brief Check user data CRCs.
 *
 * \param data Pointer to user data.
 * \param len Length of user data.
 *
 * \retval 1 if CRCs are OK, otherwise 0.
 */
static int DNP3CheckUserDataCRCs(const uint8_t *data, uint32_t len)
{
    uint32_t offset = 0;
    uint32_t block_size;

    while (offset < len) {
        if (len - offset >= DNP3_BLOCK_SIZE + DNP3_CRC_LEN) {
            block_size = DNP3_BLOCK_SIZE + DNP3_CRC_LEN;
        }
        else {
            block_size = len - offset;
        }

        if (!DNP3CheckCRC(data + offset, block_size)) {
            /* Once failed, may as well return immediately. */
            return 0;
        }

        offset += block_size;
    }

    return 1;
}

/**
 * \brief Check the DNP3 frame start bytes.
 *
 * \retval 1 if valid, 0 if not.
 */
static int DNP3CheckStartBytes(const DNP3LinkHeader *header)
{
    return header->start_byte0 == DNP3_START_BYTE0 &&
        header->start_byte1 == DNP3_START_BYTE1;
}

/* Some DNP3 servers start with a banner. */
#define DNP3_BANNER "DNP3"

/**
 * \brief Check if a frame contains a banner.
 *
 * Some servers (outstations) appear to send back a banner that fails
 * the normal frame checks.  So first check for a banner.
 *
 * \retval 1 if a banner is found, 0 if not.
 */
static int DNP3ContainsBanner(const uint8_t *input, uint32_t len)
{
    return BasicSearch(input, len, (uint8_t *)DNP3_BANNER, strlen(DNP3_BANNER)) != NULL;
}

/**
 * \brief DNP3 probing parser.
 */
static uint16_t DNP3ProbingParser(
        const Flow *f, uint8_t direction, const uint8_t *input, uint32_t len, uint8_t *rdir)
{
    const DNP3LinkHeader *const hdr = (const DNP3LinkHeader *)input;
    const bool toserver = (direction & STREAM_TOSERVER) != 0;

    /* May be a banner. */
    if (DNP3ContainsBanner(input, len)) {
        SCLogDebug("Packet contains a DNP3 banner.");
        bool is_banner = true;
        // magic 0x100 = 256 seems good enough
        for (uint32_t i = 0; i < len && i < 0x100; i++) {
            if (!isprint(input[i])) {
                is_banner = false;
                break;
            }
        }
        if (is_banner) {
            if (toserver) {
                *rdir = STREAM_TOCLIENT;
            }
            return ALPROTO_DNP3;
        }
    }

    /* Check that we have the minimum amount of bytes. */
    if (len < sizeof(DNP3LinkHeader)) {
        SCLogDebug("Length too small to be a DNP3 header.");
        return ALPROTO_UNKNOWN;
    }

    /* Verify start value (from AN2013-004b). */
    if (!DNP3CheckStartBytes(hdr)) {
        SCLogDebug("Invalid start bytes.");
        return ALPROTO_FAILED;
    }

    /* Verify minimum length. */
    if (hdr->len < DNP3_MIN_LEN) {
        SCLogDebug("Packet too small to be a valid DNP3 fragment.");
        return ALPROTO_FAILED;
    }

    // Test compatibility between direction and dnp3.ctl.direction
    if ((DNP3_LINK_DIR(hdr->control) != 0) != toserver) {
        *rdir = toserver ? STREAM_TOCLIENT : STREAM_TOSERVER;
    }
    SCLogDebug("Detected DNP3.");
    return ALPROTO_DNP3;
}

/**
 * \brief Calculate the length of the transport layer with CRCs removed.
 *
 * \param input_len The length of the transport layer buffer.
 *
 * \retval The length of the buffer after CRCs are removed.
 */
static int DNP3CalculateTransportLengthWithoutCRCs(uint32_t input_len)
{
    /* Too small. */
    if (input_len < DNP3_CRC_LEN) {
        return -1;
    }

    /* Get the number of complete blocks. */
    int blocks = input_len / (DNP3_BLOCK_SIZE + DNP3_CRC_LEN);

    /* And the number of bytes in the last block. */
    int rem = input_len - (blocks * (DNP3_BLOCK_SIZE + DNP3_CRC_LEN));

    if (rem) {
        if (rem < DNP3_CRC_LEN) {
            return -1;
        }
        return (blocks * DNP3_BLOCK_SIZE) + (rem - DNP3_CRC_LEN);
    }
    else {
        return (blocks * DNP3_BLOCK_SIZE);
    }
}

/**
 * \brief Reassemble the application layer by stripping the CRCs.
 *
 * Remove the CRCs from the user data blocks.  The output is the user
 * data with the CRCs removed as well as the transport header removed,
 * but the input data still needs to include the transport header as
 * its part of the first user data block.
 *
 * If the output length passed in is non-null, the new input data will
 * be appended, and the output length pointer incremented as needed.
 *
 * \param input Input buffer starting at the transport header (which
 *    will be removed from the output).
 * \param input_len Length of the input buffer.
 * \param output Pointer to output buffer (may be realloc'd).
 * \param output_len Pointer to output length.
 *
 * \retval 1 if reassembly was successful, otherwise 0.
 */
static int DNP3ReassembleApplicationLayer(const uint8_t *input,
    uint32_t input_len, uint8_t **output, uint32_t *output_len)
{
    int len = DNP3CalculateTransportLengthWithoutCRCs(input_len);

    if (len <= 0) {
        return 0;
    }

    /* Remove one byte for the transport header and make sure we have
     * at least one byte of user data. */
    if (--len < 1) {
        return 0;
    }

    if (*output == NULL) {
        *output = SCCalloc(1, len);
        if (unlikely(*output == NULL)) {
            return 0;
        }
    }
    else {
        uint8_t *ptr = SCRealloc(*output, (size_t)(*output_len + len));
        if (unlikely(ptr == NULL)) {
            return 0;
        }
        *output = ptr;
    }

    int offset = 0, block_size;
    while ((uint32_t)offset < input_len) {
        if (input_len - offset > DNP3_BLOCK_SIZE + DNP3_CRC_LEN) {
            block_size = DNP3_BLOCK_SIZE + DNP3_CRC_LEN;
        }
        else {
            block_size = input_len - offset;
        }

        /* If handling the first block (offset is 0), trim off the
         * first byte which is the transport header, and not part of
         * the application data. */
        if (offset == 0) {
            offset++;
            block_size--;
        }

        /* Need at least 3 bytes to continue. One for application
         * data, and 2 for the CRC.  If not, return failure for
         * malformed frame. */
        if (block_size < DNP3_CRC_LEN + 1) {
            SCLogDebug("Not enough data to continue.");
            return 0;
        }

        /* Make sure there is enough space to write into. */
        if (block_size - DNP3_CRC_LEN > len) {
            SCLogDebug("Not enough data to continue.");
            return 0;
        }

        memcpy(*output + *output_len, input + offset,
            block_size - DNP3_CRC_LEN);
        *output_len += block_size - DNP3_CRC_LEN;
        offset += block_size;
        len -= block_size - DNP3_CRC_LEN;
    }

    return 1;
}

/**
 * \brief Allocate a DNP3 state object.
 *
 * The DNP3 state object represents a single DNP3 TCP session.
 */
static void *DNP3StateAlloc(void *orig_state, AppProto proto_orig)
{
    SCEnter();
    DNP3State *dnp3;

    dnp3 = (DNP3State *)SCCalloc(1, sizeof(DNP3State));
    if (unlikely(dnp3 == NULL)) {
        return NULL;
    }
    TAILQ_INIT(&dnp3->tx_list);

    SCReturnPtr(dnp3, "void");
}

/**
 * \brief Set a DNP3 application layer event.
 *
 * Sets an event on the current transaction object.
 */
static void DNP3SetEvent(DNP3State *dnp3, uint8_t event)
{
    if (dnp3 && dnp3->curr) {
        AppLayerDecoderEventsSetEventRaw(&dnp3->curr->tx_data.events, event);
        dnp3->events++;
    }
    else {
        SCLogWarning("Failed to set event, state or tx pointer was NULL.");
    }
}

/**
 * \brief Set a DNP3 application layer event on a transaction.
 */
static void DNP3SetEventTx(DNP3Transaction *tx, uint8_t event)
{
    AppLayerDecoderEventsSetEventRaw(&tx->tx_data.events, event);
    tx->dnp3->events++;
}

/**
 * \brief Allocation a DNP3 transaction.
 */
static DNP3Transaction *DNP3TxAlloc(DNP3State *dnp3, bool request)
{
    DNP3Transaction *tx = SCCalloc(1, sizeof(DNP3Transaction));
    if (unlikely(tx == NULL)) {
        return NULL;
    }
    dnp3->transaction_max++;
    dnp3->unreplied++;
    dnp3->curr = tx;
    tx->dnp3 = dnp3;
    tx->tx_num = dnp3->transaction_max;
    tx->is_request = request;
    if (tx->is_request) {
        tx->tx_data.flags = APP_LAYER_TX_SKIP_INSPECT_TC;
    } else {
        tx->tx_data.flags = APP_LAYER_TX_SKIP_INSPECT_TS;
    }
    TAILQ_INIT(&tx->objects);
    TAILQ_INSERT_TAIL(&dnp3->tx_list, tx, next);

    /* Check for flood state. */
    if (dnp3->unreplied > DNP3_DEFAULT_REQ_FLOOD_COUNT) {
        DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_FLOODED);
        dnp3->flooded = 1;
    }

    return tx;
}

/**
 * \brief Calculate the length of a link frame with CRCs.
 *
 * This is required as the length parameter in the DNP3 header does not
 * include the added CRCs.
 *
 * \param length The length from the DNP3 link header.
 *
 * \retval The length of the frame with CRCs included or 0 if the length isn't
 *    long enough to be a valid DNP3 frame.
 */
static uint32_t DNP3CalculateLinkLength(uint8_t length)
{
    uint32_t frame_len = 0;
    int rem;

    /* Fail early if the length is less than the minimum size. */
    if (length < DNP3_LINK_HDR_LEN) {
        return 0;
    }

    /* Subtract the 5 bytes of the header that are included in the
     * length. */
    length -= DNP3_LINK_HDR_LEN;

    rem = length % DNP3_BLOCK_SIZE;
    frame_len = (length / DNP3_BLOCK_SIZE) * (DNP3_BLOCK_SIZE + DNP3_CRC_LEN);
    if (rem) {
        frame_len += rem + DNP3_CRC_LEN;
    }

    return frame_len + sizeof(DNP3LinkHeader);
}

/**
 * \brief Check if the link function code specifies user data.
 *
 * \param header Point to link header.
 *
 * \retval 1 if frame contains user data, otherwise 0.
 */
static int DNP3IsUserData(const DNP3LinkHeader *header)
{
    switch (DNP3_LINK_FC(header->control)) {
        case DNP3_LINK_FC_CONFIRMED_USER_DATA:
        case DNP3_LINK_FC_UNCONFIRMED_USER_DATA:
            return 1;
        default:
            return 0;
    }
}

/**
 * \brief Check if the frame has user data.
 *
 * Check if the DNP3 frame actually has user data by checking if data
 * exists after the headers.
 *
 * \retval 1 if user data exists, otherwise 0.
 */
static int DNP3HasUserData(const DNP3LinkHeader *header, uint8_t direction)
{
    if (direction == STREAM_TOSERVER) {
        return header->len >= DNP3_LINK_HDR_LEN + sizeof(DNP3TransportHeader) +
            sizeof(DNP3ApplicationHeader);
    }
    else {
        return header->len >= DNP3_LINK_HDR_LEN + sizeof(DNP3TransportHeader) +
            sizeof(DNP3ApplicationHeader) + sizeof(DNP3InternalInd);
    }
}

/**
 * \brief Reset a DNP3Buffer.
 */
static void DNP3BufferReset(DNP3Buffer *buffer)
{
    buffer->offset = 0;
    buffer->len = 0;
}

/**
 * \brief Add data to a DNP3 buffer, enlarging the buffer if required.
 *
 * \param buffer Buffer to add data data.
 * \param data Data to be added to buffer.
 * \param len Size of data to be added to buffer.
 *
 * \param 1 if data was added successful, otherwise 0.
 */
static int DNP3BufferAdd(DNP3Buffer *buffer, const uint8_t *data, uint32_t len)
{
    if (buffer->size == 0) {
        buffer->buffer = SCCalloc(1, len);
        if (unlikely(buffer->buffer == NULL)) {
            return 0;
        }
        buffer->size = len;
    }
    else if (buffer->len + len > buffer->size) {
        uint8_t *tmp = SCRealloc(buffer->buffer, buffer->len + len);
        if (unlikely(tmp == NULL)) {
            return 0;
        }
        buffer->buffer = tmp;
        buffer->size = buffer->len + len;
    }
    memcpy(buffer->buffer + buffer->len, data, len);
    buffer->len += len;

    return 1;
}

/**
 * \brief Trim a DNP3 buffer.
 *
 * Trimming a buffer moves the data in the buffer up to the front of
 * the buffer freeing up room at the end for more incoming data.
 *
 * \param buffer The buffer to trim.
 */
static void DNP3BufferTrim(DNP3Buffer *buffer)
{
    if (buffer->offset == buffer->len) {
        DNP3BufferReset(buffer);
    }
    else if (buffer->offset > 0) {
        memmove(buffer->buffer, buffer->buffer + buffer->offset,
            buffer->len - buffer->offset);
        buffer->len = buffer->len - buffer->offset;
        buffer->offset = 0;
    }
}

/**
 * \brief Free a DNP3 object.
 */
static void DNP3ObjectFree(DNP3Object *object)
{
    if (object->points != NULL) {
        DNP3FreeObjectPointList(object->group, object->variation,
            object->points);
    }
    SCFree(object);
}

/**
 * \brief Allocate a DNP3 object.
 */
static DNP3Object *DNP3ObjectAlloc(void)
{
    DNP3Object *object = SCCalloc(1, sizeof(*object));
    if (unlikely(object == NULL)) {
        return NULL;
    }
    object->points = DNP3PointListAlloc();
    if (object->points == NULL) {
        DNP3ObjectFree(object);
        return NULL;
    }
    return object;
}

/**
 * \brief Decode DNP3 application objects.
 *
 * This function decoded known DNP3 application objects. As the
 * protocol isn't self describing, we can only decode the buffer while
 * the application objects are known.  As soon as an unknown
 * group/variation is hit, we must stop processing.
 *
 * \param buf the input buffer
 * \param len length of the input buffer
 * \param objects pointer to list where decoded objects will be stored.
 *
 * \retval 1 if all objects decoded, 0 if all objects could not be decoded (
 *    unknown group/variations)
 */
static int DNP3DecodeApplicationObjects(DNP3Transaction *tx, const uint8_t *buf,
    uint32_t len, DNP3ObjectList *objects)
{
    int retval = 0;

    if (buf == NULL || len == 0) {
        return 1;
    }

    while (len) {
        uint32_t offset = 0;

        if (len < sizeof(DNP3ObjHeader)) {
            goto done;
        }
        DNP3ObjHeader *header = (DNP3ObjHeader *)buf;
        offset += sizeof(DNP3ObjHeader);

        DNP3Object *object = DNP3ObjectAlloc();
        if (unlikely(object == NULL)) {
            goto done;
        }
        TAILQ_INSERT_TAIL(objects, object, next);

        object->group = header->group;
        object->variation = header->variation;
        object->qualifier = header->qualifier;
        object->prefix_code = DNP3_OBJ_PREFIX(header->qualifier);
        object->range_code = DNP3_OBJ_RANGE(header->qualifier);

        /* IEEE 1815-2012, Table 4-5. */
        switch (object->range_code) {
            case 0x00:
            case 0x03: {
                /* 1 octet start and stop indexes OR 1 octet start and
                 * stop virtual addresses. */
                if (offset + (sizeof(uint8_t) * 2) > len) {
                    /* Not enough data. */
                    SCLogDebug("Not enough data.");
                    goto not_enough_data;
                }
                object->start = buf[offset++];
                object->stop = buf[offset++];
                object->count = object->stop - object->start + 1;
                break;
            }
            case 0x01:
            case 0x04: {
                /* 2 octet start and stop indexes OR 2 octect start
                 * and stop virtual addresses. */
                if (offset + (sizeof(uint16_t) * 2) > len) {
                    /* Not enough data. */
                    SCLogDebug("Not enough data.");
                    goto not_enough_data;
                }
                object->start = DNP3_SWAP16(*(uint16_t *)(buf + offset));
                offset += sizeof(uint16_t);
                object->stop = DNP3_SWAP16(*(uint16_t *)(buf + offset));
                offset += sizeof(uint16_t);
                object->count = object->stop - object->start + 1;
                break;
            }
            case 0x02:
            case 0x05: {
                /* 4 octet start and stop indexes OR 4 octect start
                 * and stop virtual addresses. */
                if (offset + (sizeof(uint32_t) * 2) > len) {
                    /* Not enough data. */
                    SCLogDebug("Not enough data.");
                    goto not_enough_data;
                }
                object->start = DNP3_SWAP32(*(uint32_t *)(buf + offset));
                offset += sizeof(uint32_t);
                object->stop = DNP3_SWAP32(*(uint32_t *)(buf + offset));
                offset += sizeof(uint32_t);
                object->count = object->stop - object->start + 1;
                break;
            }
            case 0x06:
                /* No range field. */
                object->count = 0;
                break;
            case 0x07:
                /* 1 octet count of objects. */
                if (offset + sizeof(uint8_t) > len) {
                    SCLogDebug("Not enough data.");
                    goto not_enough_data;
                }
                object->count = buf[offset];
                offset += sizeof(uint8_t);
                break;
            case 0x08: {
                /* 2 octet count of objects. */
                if (offset + sizeof(uint16_t) > len) {
                    SCLogDebug("Not enough data.");
                    goto not_enough_data;
                }
                object->count = DNP3_SWAP16(*(uint16_t *)(buf + offset));
                offset += sizeof(uint16_t);
                break;
            }
            case 0x09: {
                /* 4 octet count of objects. */
                if (offset + sizeof(uint32_t) > len) {
                    SCLogDebug("Not enough data.");
                    goto not_enough_data;
                }
                object->count = DNP3_SWAP32(*(uint32_t *)(buf + offset));
                offset += sizeof(uint32_t);
                break;
            }
            case 0x0b: {
                if (offset + sizeof(uint8_t) > len) {
                    /* Not enough data. */
                    SCLogDebug("Not enough data.");
                    goto not_enough_data;
                }
                object->count = *(uint8_t *)(buf + offset);
                offset += sizeof(uint8_t);
                break;
            }
            default:
                SCLogDebug("Range code 0x%02x is reserved.",
                    object->range_code);
                goto done;
        }

        buf += offset;
        len -= offset;

        if (object->variation == 0 || object->count == 0) {
            goto next;
        }

        int event = DNP3DecodeObject(header->group, header->variation, &buf,
            &len, object->prefix_code, object->start, object->count,
            object->points);
        if (event) {
            DNP3SetEventTx(tx, DNP3_DECODER_EVENT_UNKNOWN_OBJECT);
            goto done;
        }

    next:
        continue;
    }

    /* All objects were decoded. */
    retval = 1;

not_enough_data:
done:
    return retval;
}

/**
 * \brief Handle DNP3 request user data.
 *
 * \param dnp3 the current DNP3State
 * \param input pointer to the DNP3 frame (starting with link header)
 * \param input_len length of the input frame
 */
static void DNP3HandleUserDataRequest(
        Flow *f, DNP3State *dnp3, const uint8_t *input, uint32_t input_len)
{
    DNP3LinkHeader *lh;
    DNP3TransportHeader th;
    DNP3ApplicationHeader *ah;
    DNP3Transaction *tx = NULL, *ttx;

    lh = (DNP3LinkHeader *)input;

    if (!DNP3CheckUserDataCRCs(input + sizeof(DNP3LinkHeader),
            input_len - sizeof(DNP3LinkHeader))) {
        return;
    }

    th = input[sizeof(DNP3LinkHeader)];

    if (!DNP3_TH_FIR(th)) {
        TAILQ_FOREACH(ttx, &dnp3->tx_list, next) {
            if (ttx->lh.src == lh->src && ttx->lh.dst == lh->dst && ttx->is_request && !ttx->done &&
                    NEXT_TH_SEQNO(DNP3_TH_SEQ(ttx->th)) == DNP3_TH_SEQ(th)) {
                tx = ttx;
                break;
            }
        }

        if (tx == NULL) {
            return;
        }

        /* Update the saved transport header so subsequent segments
         * will be matched to this sequence number. */
        tx->th = th;
        tx->tx_data.updated_ts = true;
    }
    else {
        ah = (DNP3ApplicationHeader *)(input + sizeof(DNP3LinkHeader) +
            sizeof(DNP3TransportHeader));

        /* Ignore confirms - for now. */
        if (ah->function_code == DNP3_APP_FC_CONFIRM) {
            return;
        }

        /* Create a transaction. */
        tx = DNP3TxAlloc(dnp3, true);
        if (unlikely(tx == NULL)) {
            return;
        }
        tx->tx_data.updated_ts = true;
        tx->lh = *lh;
        tx->th = th;
        tx->ah = *ah;
    }

    if (!DNP3ReassembleApplicationLayer(input + sizeof(DNP3LinkHeader),
                input_len - sizeof(DNP3LinkHeader), &tx->buffer, &tx->buffer_len)) {

        /* Malformed, set event and mark as done. */
        DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_MALFORMED);
        tx->done = 1;
        return;
    }

    /* If this is not the final segment, just return. */
    if (!DNP3_TH_FIN(th)) {
        return;
    }

    tx->done = 1;

    if (DNP3DecodeApplicationObjects(tx, tx->buffer + sizeof(DNP3ApplicationHeader),
                tx->buffer_len - sizeof(DNP3ApplicationHeader), &tx->objects)) {
        tx->complete = 1;
    }
    if (f != NULL) {
        AppLayerParserTriggerRawStreamInspection(f, STREAM_TOSERVER);
    }
}

static void DNP3HandleUserDataResponse(
        Flow *f, DNP3State *dnp3, const uint8_t *input, uint32_t input_len)
{
    DNP3LinkHeader *lh;
    DNP3TransportHeader th;
    DNP3ApplicationHeader *ah;
    DNP3InternalInd *iin;
    DNP3Transaction *tx = NULL, *ttx;
    uint32_t offset = 0;

    lh = (DNP3LinkHeader *)input;
    offset += sizeof(DNP3LinkHeader);

    if (!DNP3CheckUserDataCRCs(input + offset, input_len - offset)) {
        return;
    }

    th = input[offset++];

    if (!DNP3_TH_FIR(th)) {
        TAILQ_FOREACH(ttx, &dnp3->tx_list, next) {
            if (ttx->lh.src == lh->src && ttx->lh.dst == lh->dst && !ttx->is_request &&
                    !ttx->done && NEXT_TH_SEQNO(DNP3_TH_SEQ(ttx->th)) == DNP3_TH_SEQ(th)) {
                tx = ttx;
                break;
            }
        }

        if (tx == NULL) {
            return;
        }

        /* Replace the transport header in the transaction with this
         * one in case there are more frames. */
        tx->th = th;
        tx->tx_data.updated_tc = true;
    }
    else {
        ah = (DNP3ApplicationHeader *)(input + offset);
        offset += sizeof(DNP3ApplicationHeader);
        iin = (DNP3InternalInd *)(input + offset);

        tx = DNP3TxAlloc(dnp3, false);
        if (unlikely(tx == NULL)) {
            return;
        }
        tx->tx_data.updated_tc = true;
        tx->lh = *lh;
        tx->th = th;
        tx->ah = *ah;
        tx->iin = *iin;
    }

    BUG_ON(tx->is_request);

    if (!DNP3ReassembleApplicationLayer(input + sizeof(DNP3LinkHeader),
                input_len - sizeof(DNP3LinkHeader), &tx->buffer, &tx->buffer_len)) {
        DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_MALFORMED);
        return;
    }

    if (!DNP3_TH_FIN(th)) {
        return;
    }

    tx->done = 1;

    offset = sizeof(DNP3ApplicationHeader) + sizeof(DNP3InternalInd);
    if (DNP3DecodeApplicationObjects(
                tx, tx->buffer + offset, tx->buffer_len - offset, &tx->objects)) {
        tx->complete = 1;
    }
    if (f != NULL) {
        AppLayerParserTriggerRawStreamInspection(f, STREAM_TOCLIENT);
    }
}

/**
 * \brief Decode the DNP3 request link layer.
 *
 * \retval number of bytes processed or -1 if the data stream does not look
 *     like DNP3.
 */
static int DNP3HandleRequestLinkLayer(
        Flow *f, DNP3State *dnp3, const uint8_t *input, uint32_t input_len)
{
    SCEnter();
    uint32_t processed = 0;

    while (input_len) {

        /* Need at least enough bytes for a DNP3 header. */
        if (input_len < sizeof(DNP3LinkHeader)) {
            break;
        }

        DNP3LinkHeader *header = (DNP3LinkHeader *)input;

        if (!DNP3CheckStartBytes(header)) {
            goto error;
        }

        if (!DNP3CheckLinkHeaderCRC(header)) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_BAD_LINK_CRC);
            goto error;
        }

        uint32_t frame_len = DNP3CalculateLinkLength(header->len);
        if (frame_len == 0) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_LEN_TOO_SMALL);
            goto error;
        }
        if (input_len < frame_len) {
            /* Insufficient data, just break - will wait for more data. */
            break;
        }

        /* Ignore non-user data for now. */
        if (!DNP3IsUserData(header)) {
            goto next;
        }

        /* Make sure the header length is large enough for transport and
         * application headers. */
        if (!DNP3HasUserData(header, STREAM_TOSERVER)) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_LEN_TOO_SMALL);
            goto next;
        }

        if (!DNP3CheckUserDataCRCs(input + sizeof(DNP3LinkHeader),
                frame_len - sizeof(DNP3LinkHeader))) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_BAD_TRANSPORT_CRC);
            goto next;
        }

        DNP3HandleUserDataRequest(f, dnp3, input, frame_len);

    next:
        /* Advance the input buffer. */
        input += frame_len;
        input_len -= frame_len;
        processed += frame_len;
    }

    SCReturnInt(processed);
error:
    /* Error out. Should only happen if this doesn't look like a DNP3
     * frame. */
    SCReturnInt(-1);
}

/**
 * \brief Handle incoming request data.
 *
 * The actual request PDU parsing is done in
 * DNP3HandleRequestLinkLayer. This function takes care of buffering TCP
 * date if a segment does not contain a complete frame (or contains
 * multiple frames, but not the complete final frame).
 */
static AppLayerResult DNP3ParseRequest(Flow *f, void *state, AppLayerParserState *pstate,
        StreamSlice stream_slice, void *local_data)
{
    SCEnter();
    DNP3State *dnp3 = (DNP3State *)state;
    DNP3Buffer *buffer = &dnp3->request_buffer;
    int processed = 0;

    const uint8_t *input = StreamSliceGetData(&stream_slice);
    uint32_t input_len = StreamSliceGetDataLen(&stream_slice);

    if (input_len == 0) {
        SCReturnStruct(APP_LAYER_OK);
    }

    if (buffer->len) {
        if (!DNP3BufferAdd(buffer, input, input_len)) {
            goto error;
        }
        processed = DNP3HandleRequestLinkLayer(
                f, dnp3, buffer->buffer + buffer->offset, buffer->len - buffer->offset);
        if (processed < 0) {
            goto error;
        }
        buffer->offset += processed;
        DNP3BufferTrim(buffer);
    }
    else {
        processed = DNP3HandleRequestLinkLayer(f, dnp3, input, input_len);
        if (processed < 0) {
            SCLogDebug("Failed to process request link layer.");
            goto error;
        }

        input += processed;
        input_len -= processed;

        /* Not all data was processed, buffer it. */
        if (input_len) {
            if (!DNP3BufferAdd(buffer, input, input_len)) {
                goto error;
            }
        }
    }

    SCReturnStruct(APP_LAYER_OK);

error:
    /* Reset the buffer. */
    DNP3BufferReset(buffer);
    SCReturnStruct(APP_LAYER_ERROR);
}

/**
 * \brief Decode the DNP3 response link layer.
 *
 * \retval number of bytes processed or -1 if the data stream does not
 *     like look DNP3.
 */
static int DNP3HandleResponseLinkLayer(
        Flow *f, DNP3State *dnp3, const uint8_t *input, uint32_t input_len)
{
    SCEnter();
    uint32_t processed = 0;

    while (input_len) {

        /* Need at least enough bytes for a DNP3 header. */
        if (input_len < sizeof(DNP3LinkHeader)) {
            break;
        }

        DNP3LinkHeader *header = (DNP3LinkHeader *)input;

        if (!DNP3CheckStartBytes(header)) {
            goto error;
        }

        if (!DNP3CheckLinkHeaderCRC(header)) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_BAD_LINK_CRC);
            goto error;
        }

        /* Calculate the number of bytes needed to for this frame. */
        uint32_t frame_len = DNP3CalculateLinkLength(header->len);
        if (frame_len == 0) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_LEN_TOO_SMALL);
            goto error;
        }
        if (input_len < frame_len) {
            /* Insufficient data, just break - will wait for more data. */
            break;
        }

        /* Only handle user data frames for now. */
        if (!DNP3IsUserData(header)) {
            goto next;
        }

        /* Make sure the header length is large enough for transport and
         * application headers. */
        if (!DNP3HasUserData(header, STREAM_TOCLIENT)) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_LEN_TOO_SMALL);
            goto error;
        }

        if (!DNP3CheckUserDataCRCs(input + sizeof(DNP3LinkHeader),
                frame_len - sizeof(DNP3LinkHeader))) {
            DNP3SetEvent(dnp3, DNP3_DECODER_EVENT_BAD_TRANSPORT_CRC);
            goto next;
        }

        DNP3HandleUserDataResponse(f, dnp3, input, frame_len);

    next:
        /* Advance the input buffer. */
        input += frame_len;
        input_len -= frame_len;
        processed += frame_len;
    }

    SCReturnInt(processed);
error:
    /* Error out. Should only happen if the data stream no longer
     * looks like DNP3. */
    SCReturnInt(-1);
}

/**
 * \brief Parse incoming data.
 *
 * This is the entry function for DNP3 application layer data. Its
 * main responsibility is buffering incoming data that cannot be
 * processed.
 *
 * See DNP3ParseResponsePDUs for DNP3 frame handling.
 */
static AppLayerResult DNP3ParseResponse(Flow *f, void *state, AppLayerParserState *pstate,
        StreamSlice stream_slice, void *local_data)
{
    SCEnter();

    DNP3State *dnp3 = (DNP3State *)state;
    DNP3Buffer *buffer = &dnp3->response_buffer;
    int processed;

    const uint8_t *input = StreamSliceGetData(&stream_slice);
    uint32_t input_len = StreamSliceGetDataLen(&stream_slice);

    if (buffer->len) {
        if (!DNP3BufferAdd(buffer, input, input_len)) {
            goto error;
        }
        processed = DNP3HandleResponseLinkLayer(
                f, dnp3, buffer->buffer + buffer->offset, buffer->len - buffer->offset);
        if (processed < 0) {
            goto error;
        }
        buffer->offset += processed;
        DNP3BufferTrim(buffer);
    }
    else {

        /* Check if this is a banner, ignore if it is. */
        if (DNP3ContainsBanner(input, input_len)) {
            goto done;
        }

        processed = DNP3HandleResponseLinkLayer(f, dnp3, input, input_len);
        if (processed < 0) {
            goto error;
        }
        input += processed;
        input_len -= processed;

        /* Not all data was processed, buffer it. */
        if (input_len) {
            if (!DNP3BufferAdd(buffer, input, input_len)) {
                goto error;
            }
        }
    }

done:
    SCReturnStruct(APP_LAYER_OK);

error:
    /* An error occurred while processing DNP3 frames.  Dump the
     * buffer as we can't be assured that they are valid anymore. */
    DNP3BufferReset(buffer);
    SCReturnStruct(APP_LAYER_ERROR);
}

static void *DNP3GetTx(void *alstate, uint64_t tx_id)
{
    SCEnter();
    DNP3State *dnp3 = (DNP3State *)alstate;
    DNP3Transaction *tx = NULL;
    uint64_t tx_num = tx_id + 1;

    if (dnp3->curr && dnp3->curr->tx_num == (tx_num)) {
        SCReturnPtr(dnp3->curr, "void");
    }

    TAILQ_FOREACH(tx, &dnp3->tx_list, next) {
        if (tx_num != tx->tx_num) {
            continue;
        }
        SCReturnPtr(tx, "void");
    }

    SCReturnPtr(NULL, "void");
}

static uint64_t DNP3GetTxCnt(void *state)
{
    SCEnter();
    uint64_t count = ((uint64_t)((DNP3State *)state)->transaction_max);
    SCReturnUInt(count);
}

/**
 * \brief Free all the objects in a DNP3ObjectList.
 */
static void DNP3TxFreeObjectList(DNP3ObjectList *objects)
{
    DNP3Object *object;

    while ((object = TAILQ_FIRST(objects)) != NULL) {
        TAILQ_REMOVE(objects, object, next);
        DNP3ObjectFree(object);
    }
}

/**
 * \brief Free a DNP3 transaction.
 */
static void DNP3TxFree(DNP3Transaction *tx)
{
    SCEnter();

    if (tx->buffer != NULL) {
        SCFree(tx->buffer);
    }

    SCAppLayerTxDataCleanup(&tx->tx_data);

    DNP3TxFreeObjectList(&tx->objects);

    SCFree(tx);
    SCReturn;
}

/**
 * \brief Free a transaction by ID on a specific DNP3 state.
 *
 * This function is called by the app-layer to free a transaction on a
 * specific DNP3 state object.
 */
static void DNP3StateTxFree(void *state, uint64_t tx_id)
{
    SCEnter();
    DNP3State *dnp3 = state;
    DNP3Transaction *tx = NULL, *ttx;
    uint64_t tx_num = tx_id + 1;

    TAILQ_FOREACH_SAFE(tx, &dnp3->tx_list, next, ttx) {

        if (tx->tx_num != tx_num) {
            continue;
        }

        if (tx == dnp3->curr) {
            dnp3->curr = NULL;
        }

        if (tx->tx_data.events != NULL) {
            if (tx->tx_data.events->cnt <= dnp3->events) {
                dnp3->events -= tx->tx_data.events->cnt;
            } else {
                dnp3->events = 0;
            }
        }
        dnp3->unreplied--;

        /* Check flood state. */
        if (dnp3->flooded && dnp3->unreplied < DNP3_DEFAULT_REQ_FLOOD_COUNT) {
            dnp3->flooded = 0;
        }

        TAILQ_REMOVE(&dnp3->tx_list, tx, next);
        DNP3TxFree(tx);
        break;
    }

    SCReturn;
}

/**
 * \brief Free a DNP3 state.
 */
static void DNP3StateFree(void *state)
{
    SCEnter();
    DNP3State *dnp3 = state;
    DNP3Transaction *tx;
    if (state != NULL) {
        while ((tx = TAILQ_FIRST(&dnp3->tx_list)) != NULL) {
            TAILQ_REMOVE(&dnp3->tx_list, tx, next);
            DNP3TxFree(tx);
        }
        if (dnp3->request_buffer.buffer != NULL) {
            SCFree(dnp3->request_buffer.buffer);
        }
        if (dnp3->response_buffer.buffer != NULL) {
            SCFree(dnp3->response_buffer.buffer);
        }
        SCFree(dnp3);
    }
    SCReturn;
}

/**
 * \brief Called by the app-layer to get the state progress.
 */
static int DNP3GetAlstateProgress(void *tx, uint8_t direction)
{
    DNP3Transaction *dnp3tx = (DNP3Transaction *)tx;
    DNP3State *dnp3 = dnp3tx->dnp3;
    int retval = 0;

    /* If flooded, "ack" old transactions. */
    if (dnp3->flooded && (dnp3->transaction_max -
            dnp3tx->tx_num >= DNP3_DEFAULT_REQ_FLOOD_COUNT)) {
        SCLogDebug("flooded: returning tx as done.");
        SCReturnInt(1);
    }

    if (dnp3tx->complete)
        retval = 1;

    SCReturnInt(retval);
}

/**
 * \brief App-layer support.
 */
static int DNP3StateGetEventInfo(
        const char *event_name, uint8_t *event_id, AppLayerEventType *event_type)
{
    if (SCAppLayerGetEventIdByName(event_name, dnp3_decoder_event_table, event_id) == 0) {
        *event_type = APP_LAYER_EVENT_TYPE_TRANSACTION;
        return 0;
    }
    return -1;
}

/**
 * \brief App-layer support.
 */
static int DNP3StateGetEventInfoById(
        uint8_t event_id, const char **event_name, AppLayerEventType *event_type)
{
    *event_name = SCMapEnumValueToName(event_id, dnp3_decoder_event_table);
    if (*event_name == NULL) {
        SCLogError("Event \"%d\" not present in "
                   "the DNP3 enum event map table.",
                event_id);
        return -1;
    }

    *event_type = APP_LAYER_EVENT_TYPE_TRANSACTION;

    return 0;
}

static AppLayerTxData *DNP3GetTxData(void *vtx)
{
    DNP3Transaction *tx = (DNP3Transaction *)vtx;
    return &tx->tx_data;
}

static AppLayerStateData *DNP3GetStateData(void *vstate)
{
    DNP3State *state = (DNP3State *)vstate;
    return &state->state_data;
}

/**
 * \brief Check if the prefix code is a size prefix.
 *
 * \retval 1 if the prefix_code specifies a size prefix, 0 if not.
 */
int DNP3PrefixIsSize(uint8_t prefix_code)
{
    switch (prefix_code) {
        case 0x04:
        case 0x05:
        case 0x06:
            return 1;
            break;
        default:
            return 0;
    }
}

static AppLayerGetTxIterTuple DNP3GetTxIterator(const uint8_t ipproto, const AppProto alproto,
        void *alstate, uint64_t min_tx_id, uint64_t max_tx_id, AppLayerGetTxIterState *state)
{
    DNP3State *dnp_state = (DNP3State *)alstate;
    AppLayerGetTxIterTuple no_tuple = { NULL, 0, false };
    if (dnp_state) {
        DNP3Transaction *tx_ptr;
        if (state->un.ptr == NULL) {
            tx_ptr = TAILQ_FIRST(&dnp_state->tx_list);
        } else {
            tx_ptr = (DNP3Transaction *)state->un.ptr;
        }
        if (tx_ptr) {
            while (tx_ptr->tx_num < min_tx_id + 1) {
                tx_ptr = TAILQ_NEXT(tx_ptr, next);
                if (!tx_ptr) {
                    return no_tuple;
                }
            }
            if (tx_ptr->tx_num >= max_tx_id + 1) {
                return no_tuple;
            }
            state->un.ptr = TAILQ_NEXT(tx_ptr, next);
            AppLayerGetTxIterTuple tuple = {
                .tx_ptr = tx_ptr,
                .tx_id = tx_ptr->tx_num - 1,
                .has_next = (state->un.ptr != NULL),
            };
            return tuple;
        }
    }
    return no_tuple;
}

/**
 * \brief Register the DNP3 application protocol parser.
 */
void RegisterDNP3Parsers(void)
{
    SCEnter();

    const char *proto_name = "dnp3";

    if (SCAppLayerProtoDetectConfProtoDetectionEnabledDefault("tcp", proto_name, false)) {
        AppLayerProtoDetectRegisterProtocol(ALPROTO_DNP3, proto_name);

        if (RunmodeIsUnittests()) {
            SCAppLayerProtoDetectPPRegister(IPPROTO_TCP, DNP3_DEFAULT_PORT, ALPROTO_DNP3, 0,
                    sizeof(DNP3LinkHeader), STREAM_TOSERVER, DNP3ProbingParser, DNP3ProbingParser);
        }
        else {
            if (!SCAppLayerProtoDetectPPParseConfPorts("tcp", IPPROTO_TCP, proto_name, ALPROTO_DNP3,
                        0, sizeof(DNP3LinkHeader), DNP3ProbingParser, DNP3ProbingParser)) {
                return;
            }
        }

    } else {
        SCLogConfig("Protocol detection and parser disabled for DNP3.");
        SCReturn;
    }

    if (SCAppLayerParserConfParserEnabled("tcp", proto_name)) {
        SCLogConfig("Registering DNP3/tcp parsers.");

        AppLayerParserRegisterParser(IPPROTO_TCP, ALPROTO_DNP3, STREAM_TOSERVER,
            DNP3ParseRequest);
        AppLayerParserRegisterParser(IPPROTO_TCP, ALPROTO_DNP3, STREAM_TOCLIENT,
            DNP3ParseResponse);

        AppLayerParserRegisterStateFuncs(IPPROTO_TCP, ALPROTO_DNP3,
            DNP3StateAlloc, DNP3StateFree);

        AppLayerParserRegisterGetTx(IPPROTO_TCP, ALPROTO_DNP3, DNP3GetTx);
        AppLayerParserRegisterGetTxIterator(IPPROTO_TCP, ALPROTO_DNP3, DNP3GetTxIterator);
        AppLayerParserRegisterGetTxCnt(IPPROTO_TCP, ALPROTO_DNP3, DNP3GetTxCnt);
        AppLayerParserRegisterTxFreeFunc(IPPROTO_TCP, ALPROTO_DNP3,
            DNP3StateTxFree);

        AppLayerParserRegisterGetStateProgressFunc(IPPROTO_TCP, ALPROTO_DNP3,
            DNP3GetAlstateProgress);
        AppLayerParserRegisterStateProgressCompletionStatus(ALPROTO_DNP3, 1, 1);

        AppLayerParserRegisterGetEventInfo(IPPROTO_TCP, ALPROTO_DNP3,
            DNP3StateGetEventInfo);
        AppLayerParserRegisterGetEventInfoById(IPPROTO_TCP, ALPROTO_DNP3,
            DNP3StateGetEventInfoById);

        AppLayerParserRegisterTxDataFunc(IPPROTO_TCP, ALPROTO_DNP3,
            DNP3GetTxData);
        AppLayerParserRegisterStateDataFunc(IPPROTO_TCP, ALPROTO_DNP3, DNP3GetStateData);
    } else {
        SCLogConfig("Parser disabled for protocol %s. "
            "Protocol detection still on.", proto_name);
    }

#ifdef UNITTESTS
    AppLayerParserRegisterProtocolUnittests(IPPROTO_TCP, ALPROTO_DNP3,
        DNP3ParserRegisterTests);
#endif

    SCReturn;
}

#ifdef UNITTESTS

#include "flow-util.h"
#include "stream-tcp.h"

/**
 * \brief Utility function to fix CRCs when mangling a frame.
 */
static void DNP3FixCrc(uint8_t *data, uint32_t len)
{
    uint32_t block_size;

    while (len) {
        if (len >= DNP3_BLOCK_SIZE + DNP3_CRC_LEN) {
            block_size = DNP3_BLOCK_SIZE;
        } else {
            block_size = len - DNP3_CRC_LEN;
        }
        uint16_t crc = DNP3ComputeCRC(data, block_size);
        data[block_size + 1] = (crc >> 8) & 0xff;
        data[block_size] = crc & 0xff;
        data += block_size + DNP3_CRC_LEN;
        len -= block_size + DNP3_CRC_LEN;
    }
}

/**
 * \test Test CRC checking on partial and full blocks.
 */
static int DNP3ParserTestCheckCRC(void)
{
    uint8_t request[] = {
        /* DNP3 start. */
        0x05, 0x64, 0x1a, 0xc4, 0x02, 0x00, 0x01, 0x00,
        0xa5, 0xe9,

        /* Transport header. */
        0xff,

        /* Application layer - segment 1. */
        0xc9, 0x05, 0x0c, 0x01, 0x28, 0x01, 0x00, 0x00,
        0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x72,
        0xef,

        /* Application layer - segment 2. */
        0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff
    };

    /* Check link header CRC. */
    FAIL_IF(!DNP3CheckCRC(request, sizeof(DNP3LinkHeader)));

    /* Check first application layer segment. */
    FAIL_IF(!DNP3CheckCRC(request + sizeof(DNP3LinkHeader),
            DNP3_BLOCK_SIZE + DNP3_CRC_LEN));

#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
    /* Change a byte in link header, should fail now. */
    request[2]++;
    FAIL_IF(DNP3CheckCRC(request, sizeof(DNP3LinkHeader)));

    /* Change a byte in the first application segment, should fail
     * now. */
    request[sizeof(DNP3LinkHeader) + 3]++;
    FAIL_IF(DNP3CheckCRC(request + sizeof(DNP3LinkHeader),
            DNP3_BLOCK_SIZE + DNP3_CRC_LEN));
#endif

    PASS;
}

/**
 * \test Test validation of all CRCs in user data.
 */
static int DNP3CheckUserDataCRCsTest(void)
{
    /* Multi-block data with valid CRCs. */
    uint8_t data_valid[] = {
        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0x00, 0x00, 0x00, 0x00,
        0x00,
        0xff, 0xff, /* CRC. */
    };
    FAIL_IF(!DNP3CheckUserDataCRCs(data_valid, sizeof(data_valid)));

#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
    /* Multi-block data with one non-crc byte altered. */
    uint8_t data_invalid[] = {
        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0x00, 0x00, 0x00, 0x00,
        0x01, /* Invalid byte. */
        0xff, 0xff, /* CRC. */
    };
    FAIL_IF(DNP3CheckUserDataCRCs(data_invalid, sizeof(data_invalid)));

    /* 1 byte - need at least 3. */
    uint8_t one_byte_nocrc[] = { 0x01 };
    FAIL_IF(DNP3CheckUserDataCRCs(one_byte_nocrc, sizeof(one_byte_nocrc)));

    /* 2 bytes - need at least 3. */
    uint8_t two_byte_nocrc[] = { 0x01, 0x02 };
    FAIL_IF(DNP3CheckUserDataCRCs(two_byte_nocrc, sizeof(two_byte_nocrc)));
#endif

    /* 3 bytes, valid CRC. */
    uint8_t three_bytes_good_crc[] = { 0x00, 0x00, 0x00 };
    *(uint16_t *)(three_bytes_good_crc + 1) = DNP3ComputeCRC(
        three_bytes_good_crc, 1);
    FAIL_IF(!DNP3CheckUserDataCRCs(three_bytes_good_crc,
            sizeof(three_bytes_good_crc)));

    PASS;
}

/**
 * \test Test the link layer length calculation.
 *
 * Test the calculation that converts the link provided in the DNP3
 * header to the actual length of the frame. That is the length with
 * CRCs as the length in the header does not include CRCs.
 */
static int DNP3CalculateLinkLengthTest(void)
{
    /* These are invalid. */
    FAIL_IF(DNP3CalculateLinkLength(0) != 0);
    FAIL_IF(DNP3CalculateLinkLength(1) != 0);
    FAIL_IF(DNP3CalculateLinkLength(2) != 0);
    FAIL_IF(DNP3CalculateLinkLength(3) != 0);
    FAIL_IF(DNP3CalculateLinkLength(4) != 0);

    /* This is the minimum size. */
    FAIL_IF(DNP3CalculateLinkLength(5) != 10);

    /* 1 full user data blocks of data. */
    FAIL_IF(DNP3CalculateLinkLength(21) != 28);

    /* 2 full user data blocks of data. */
    FAIL_IF(DNP3CalculateLinkLength(37) != 46);

    /* 2 full user data blocks, plus one more byte. */
    /* 2 full user data blocks of data. */
    FAIL_IF(DNP3CalculateLinkLength(38) != 49);

    /* The maximum size. */
    FAIL_IF(DNP3CalculateLinkLength(255) != 292);

    PASS;
}

/**
 * \test The conversion of length with CRCs to the length without
 *     CRCs.
 */
static int DNP3CalculateTransportLengthWithoutCRCsTest(void)
{
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(0) != -1);
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(1) != -1);
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(2) != 0);
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(3) != 1);
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(16) != 14);
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(17) != 15);
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(18) != 16);

    /* 19 bytes is not enough for a second block. */
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(19) != -1);

    /* 20 bytes really isn't enough either, but is large enough to
     * satisfy the CRC on the second block. */
    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(20) != 16);

    FAIL_IF(DNP3CalculateTransportLengthWithoutCRCs(21) != 17);

    PASS;
}

/**
 * \test Test the validation of the link header CRC.
 */
static int DNP3ParserCheckLinkHeaderCRC(void)
{
    /* DNP3 frame with valid headers and CRCs. */
    uint8_t request[] = {
        /* DNP3 start. */
        0x05, 0x64, 0x1a, 0xc4, 0x02, 0x00, 0x01, 0x00,
        0xa5, 0xe9,

        /* Transport header. */
        0xff,

        /* Application layer. */
        0xc9, 0x05, 0x0c, 0x01, 0x28, 0x01, 0x00, 0x00,
        0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x72,
        0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff
    };

    DNP3LinkHeader *header = (DNP3LinkHeader *)request;
    FAIL_IF(!DNP3CheckLinkHeaderCRC(header));

#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
    /* Alter a byte in the header. */
    request[4] = 0;
    FAIL_IF(DNP3CheckLinkHeaderCRC(header));
#endif

    PASS;
}

/**
 * \test Test removal of CRCs from user data.
 */
static int DNP3ReassembleApplicationLayerTest01(void)
{
    uint32_t reassembled_len = 0;
    uint8_t *output = NULL;

    uint8_t payload[] = {

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0x00, 0x00, 0x00, 0x00,
        0x00,
        0xff, 0xff, /* CRC. */
    };

    uint8_t expected[] = {
              0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        /* CRC removed. */
        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        /* CRC removed. */
        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        /* CRC removed. */
        0x00, 0x00, 0x00, 0x00,
        0x00
        /* CRC removed. */
    };

    /* Valid frame. */
    FAIL_IF(!DNP3ReassembleApplicationLayer(payload,
            sizeof(payload), &output, &reassembled_len));
    FAIL_IF(output == NULL);
    FAIL_IF(reassembled_len != sizeof(expected));
    FAIL_IF(memcmp(expected, output, reassembled_len));
    SCFree(output);

    /* 1 byte, invalid. */
    reassembled_len = 0;
    output = NULL;
    FAIL_IF(DNP3ReassembleApplicationLayer(payload, 1, &output,
            &reassembled_len));
    FAIL_IF(output != NULL);
    FAIL_IF(reassembled_len != 0);

    /* 2 bytes, invalid. */
    reassembled_len = 0;
    output = NULL;
    FAIL_IF(DNP3ReassembleApplicationLayer(payload, 2, &output,
            &reassembled_len));
    FAIL_IF(output != NULL);
    FAIL_IF(reassembled_len != 0);

    /* 3 bytes, minimum - but that would only be the transport header
     * which isn't included in the output. */
    reassembled_len = 0;
    output = NULL;
    FAIL_IF(DNP3ReassembleApplicationLayer(payload, 3, &output,
            &reassembled_len));
    FAIL_IF(output != NULL);
    FAIL_IF(reassembled_len != 0);

    /* 4 bytes is the minimum to get any reassembled data. */
    reassembled_len = 0;
    output = NULL;
    FAIL_IF(!DNP3ReassembleApplicationLayer(payload, 4, &output,
            &reassembled_len));
    FAIL_IF(output == NULL);
    FAIL_IF(reassembled_len != 1);

    /* Last block too short (by 1 byte) for data + CRC. */
    uint8_t short_payload1[] = {

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0x00, 0x00
    };
    reassembled_len = 0;
    FAIL_IF(DNP3ReassembleApplicationLayer(short_payload1,
            sizeof(short_payload1), &output, &reassembled_len));

    /* Last block too short (by 2 bytes) for data + CRC. */
    uint8_t short_payload2[] = {

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0xff, 0xc9, 0x05, 0x0c,
        0x01, 0x28, 0x01, 0x00,
        0x00, 0x00, 0x01, 0x01,
        0x01, 0x00, 0x00, 0x00,
        0x72, 0xef, /* CRC. */

        0x00,
    };
    reassembled_len = 0;
    FAIL_IF(DNP3ReassembleApplicationLayer(short_payload2,
            sizeof(short_payload2), &output, &reassembled_len));

    PASS;
}

/**
 * \test Test the probing parser.
 */
static int DNP3ProbingParserTest(void)
{
    uint8_t pkt[] = {
        0x05, 0x64, 0x05, 0xc9, 0x03, 0x00, 0x04, 0x00,
        0xbd, 0x71
    };
    uint8_t rdir = 0;

    /* Valid frame. */
    FAIL_IF(DNP3ProbingParser(NULL, STREAM_TOSERVER, pkt, sizeof(pkt), &rdir) != ALPROTO_DNP3);

    /* Send too little bytes. */
    FAIL_IF(DNP3ProbingParser(NULL, STREAM_TOSERVER, pkt, sizeof(DNP3LinkHeader) - 1, &rdir) != ALPROTO_UNKNOWN);

    /* Bad start bytes. */
    pkt[0] = 0x06;
    FAIL_IF(DNP3ProbingParser(NULL, STREAM_TOSERVER, pkt, sizeof(pkt), &rdir) != ALPROTO_FAILED);

    /* Restore start byte. */
    pkt[0] = 0x05;

    /* Set the length to a value less than the minimum length of 5. */
    pkt[2] = 0x03;
    FAIL_IF(DNP3ProbingParser(NULL, STREAM_TOSERVER, pkt, sizeof(pkt), &rdir) != ALPROTO_FAILED);

    /* Send a banner. */
    char mybanner[] = "Welcome to DNP3 SCADA.";
    FAIL_IF(DNP3ProbingParser(NULL, STREAM_TOSERVER, (uint8_t *)mybanner, sizeof(mybanner) - 1,
                    &rdir) != ALPROTO_DNP3);
    FAIL_IF(rdir != STREAM_TOCLIENT);

    PASS;
}

/**
 * \test Test a basic request/response.
 */
static int DNP3ParserTestRequestResponse(void)
{
    DNP3State *state = NULL;

    uint8_t request[] = {
        /* DNP3 start. */
        0x05, 0x64, 0x1a, 0xc4, 0x02, 0x00, 0x01, 0x00,
        0xa5, 0xe9,

        /* Transport header. */
        0xff,

        /* Application layer. */
        0xc9, 0x05, 0x0c, 0x01, 0x28, 0x01, 0x00, 0x00,
        0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x72,
        0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff
    };

    uint8_t response[] = {
        /* DNP3 start. */
        0x05, 0x64, 0x1c, 0x44, 0x01, 0x00, 0x02, 0x00,
        0xe2, 0x59,

        /* Transport header. */
        0xc3,

        /* Application layer. */
        0xc9, 0x81, 0x00, 0x00, 0x0c, 0x01, 0x28, 0x01,
        0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x7a,
        0x65, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0xff, 0xff
    };

    AppLayerParserThreadCtx *alp_tctx = AppLayerParserThreadCtxAlloc();
    Flow flow;
    TcpSession ssn;

    memset(&flow, 0, sizeof(flow));
    memset(&ssn, 0, sizeof(ssn));

    flow.protoctx = (void *)&ssn;
    flow.proto = IPPROTO_TCP;
    flow.alproto = ALPROTO_DNP3;

    StreamTcpInitConfig(true);

    SCMutexLock(&flow.m);
    FAIL_IF(AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
            STREAM_TOSERVER, request, sizeof(request)));
    SCMutexUnlock(&flow.m);

    state = flow.alstate;
    FAIL_IF(state == NULL);

    DNP3Transaction *tx = DNP3GetTx(state, 0);
    FAIL_IF(tx == NULL);
    FAIL_IF(tx->tx_num != 1);
    FAIL_IF(tx != state->curr);
    FAIL_IF(tx->buffer == NULL);
    FAIL_IF(tx->buffer_len != 20);
    FAIL_IF(tx->ah.function_code != DNP3_APP_FC_DIR_OPERATE);

    SCMutexLock(&flow.m);
    FAIL_IF(AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
            STREAM_TOCLIENT, response, sizeof(response)));
    SCMutexUnlock(&flow.m);
    DNP3Transaction *tx0 = DNP3GetTx(state, 1);
    FAIL_IF(tx0 == NULL);
    FAIL_IF(tx0 == tx);
    FAIL_IF(!tx0->done);
    FAIL_IF(tx0->buffer == NULL);

    AppLayerParserThreadCtxFree(alp_tctx);
    StreamTcpFreeConfig(true);
    FLOW_DESTROY(&flow);
    PASS;
}

/**
 * \test Test an unsolicited response from an outstation.
 *
 * This is kind of like a request initiated from the "server".
 */
static int DNP3ParserTestUnsolicitedResponseConfirm(void)
{
    DNP3State *state = NULL;

    /* Unsolicited response with confirm bit set. */
    uint8_t response[] = {
        0x05, 0x64, 0x16, 0x44, 0x01, 0x00, 0x02, 0x00,
        0x89, 0xe5, 0xc4, 0xfa, 0x82, 0x00, 0x00, 0x02,
        0x02, 0x17, 0x01, 0x01, 0x81, 0xa7, 0x75, 0xd8,
        0x32, 0x4c, 0x81, 0x3e, 0x01, 0xa1, 0xc9
    };

    /* Confirm. */
    uint8_t confirm[] = {
        0x05, 0x64, 0x08, 0xc4, 0x02, 0x00,
        0x01, 0x00, 0xd3, 0xb7, 0xc0, 0xda, 0x00, 0x6a,
        0x3d
    };

    AppLayerParserThreadCtx *alp_tctx = AppLayerParserThreadCtxAlloc();
    Flow flow;
    TcpSession ssn;

    memset(&flow, 0, sizeof(flow));
    memset(&ssn, 0, sizeof(ssn));

    flow.protoctx = (void *)&ssn;
    flow.proto = IPPROTO_TCP;
    flow.alproto = ALPROTO_DNP3;

    StreamTcpInitConfig(true);

    SCMutexLock(&flow.m);
    FAIL_IF(AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
            STREAM_TOCLIENT, response, sizeof(response)));
    SCMutexUnlock(&flow.m);

    state = flow.alstate;
    FAIL_IF(state == NULL);

    DNP3Transaction *tx = DNP3GetTx(state, 0);
    FAIL_IF(tx == NULL);
    FAIL_IF(tx->tx_num != 1);
    FAIL_IF(tx != state->curr);
    FAIL_IF(!tx->done);
    FAIL_IF(tx->ah.function_code != DNP3_APP_FC_UNSOLICITED_RESP);

    SCMutexLock(&flow.m);
    FAIL_IF(AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
            STREAM_TOSERVER, confirm, sizeof(confirm)));
    SCMutexUnlock(&flow.m);

    /* Confirms are ignored currently.  With the move to
       unidirectional transactions it might be easy to support these
       now. */
    DNP3Transaction *resptx = DNP3GetTx(state, 1);
    FAIL_IF(resptx);

    AppLayerParserThreadCtxFree(alp_tctx);
    StreamTcpFreeConfig(true);
    FLOW_DESTROY(&flow);
    PASS;
}

/**
 * \test Test flood state.
 *
 * Note that flood state needs to revisited with the modification to a
 * unidirectional protocol.
 */
static int DNP3ParserTestFlooded(void)
{
    DNP3State *state = NULL;

    uint8_t request[] = {
        /* DNP3 start. */
        0x05, 0x64, 0x1a, 0xc4, 0x02, 0x00, 0x01, 0x00,
        0xa5, 0xe9,

        /* Transport header. */
        0xff,

        /* Application layer. */
        0xc9, 0x05, 0x0c, 0x01, 0x28, 0x01, 0x00, 0x00,
        0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x72,
        0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff
    };

    AppLayerParserThreadCtx *alp_tctx = AppLayerParserThreadCtxAlloc();
    Flow flow;
    TcpSession ssn;

    memset(&flow, 0, sizeof(flow));
    memset(&ssn, 0, sizeof(ssn));

    flow.protoctx = (void *)&ssn;
    flow.proto = IPPROTO_TCP;
    flow.alproto = ALPROTO_DNP3;

    StreamTcpInitConfig(true);

    SCMutexLock(&flow.m);
    FAIL_IF(AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
            STREAM_TOSERVER, request, sizeof(request)));
    SCMutexUnlock(&flow.m);

    state = flow.alstate;
    FAIL_IF(state == NULL);

    DNP3Transaction *tx = DNP3GetTx(state, 0);
    FAIL_IF(tx == NULL);
    FAIL_IF(tx->tx_num != 1);
    FAIL_IF(tx != state->curr);
    FAIL_IF(tx->buffer == NULL);
    FAIL_IF(tx->buffer_len != 20);
    FAIL_IF(tx->ah.function_code != DNP3_APP_FC_DIR_OPERATE);
    FAIL_IF_NOT(tx->done);
    FAIL_IF_NOT(DNP3GetAlstateProgress(tx, STREAM_TOSERVER));

    for (int i = 0; i < DNP3_DEFAULT_REQ_FLOOD_COUNT - 1; i++) {
        SCMutexLock(&flow.m);
        FAIL_IF(AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
                STREAM_TOSERVER, request, sizeof(request)));
        SCMutexUnlock(&flow.m);
    }
    FAIL_IF(state->flooded);
    FAIL_IF_NOT(DNP3GetAlstateProgress(tx, STREAM_TOSERVER));

    /* One more request should trip us into flooded state. */
    SCMutexLock(&flow.m);
    FAIL_IF(AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
            STREAM_TOSERVER, request, sizeof(request)));
    SCMutexUnlock(&flow.m);
    FAIL_IF(!state->flooded);

    /* Progress for the oldest tx should return 1. */
    FAIL_IF(!DNP3GetAlstateProgress(tx, 0));

    AppLayerParserThreadCtxFree(alp_tctx);
    StreamTcpFreeConfig(true);
    FLOW_DESTROY(&flow);
    PASS;
}

/**
 * \test Test parsing of partial frames.
 *
 * As DNP3 operates over TCP, it is possible that a partial DNP3 frame
 * is received. Test that the partial frame will be buffered until the
 * remainder is seen.
 */
static int DNP3ParserTestPartialFrame(void)
{
    DNP3State *state = NULL;
    DNP3Transaction *tx;
    int r;

    uint8_t request_partial1[] = {
        /* DNP3 start. */
        0x05, 0x64, 0x1a, 0xc4, 0x02, 0x00, 0x01, 0x00,
        0xa5, 0xe9,

        /* Transport header. */
        0xff,

        /* Application layer. */
        0xc9, 0x05, 0x0c, 0x01, 0x28, 0x01, 0x00, 0x00,
    };

    uint8_t request_partial2[] = {
        /* Remainder of application layer. */
        0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x72,
        0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff
    };

    uint8_t response_partial1[] = {
        /* DNP3 start. */
        0x05, 0x64, 0x1c, 0x44, 0x01, 0x00, 0x02, 0x00,
        0xe2, 0x59,

        /* Transport header. */
        0xc3,

        /* Application layer. */
        0xc9, 0x81, 0x00, 0x00, 0x0c, 0x01, 0x28, 0x01,
    };

    uint8_t response_partial2[] = {
        0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x7a,
        0x65, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0xff, 0xff
    };

    /* Boiler plate for app layer setup. */
    AppLayerParserThreadCtx *alp_tctx = AppLayerParserThreadCtxAlloc();
    Flow flow;
    TcpSession ssn;
    memset(&flow, 0, sizeof(flow));
    memset(&ssn, 0, sizeof(ssn));
    flow.protoctx = (void *)&ssn;
    flow.proto = IPPROTO_TCP;
    flow.alproto = ALPROTO_DNP3;
    StreamTcpInitConfig(true);

    /* Pass in the first partial frame. */

    SCMutexLock(&flow.m);
    r = AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
        STREAM_TOSERVER, request_partial1, sizeof(request_partial1));
    SCMutexUnlock(&flow.m);
    FAIL_IF(r != 0);

    /* Frame should just be buffered, but not yet processed. */
    state = flow.alstate;
    FAIL_IF(state == NULL);
    FAIL_IF(state->request_buffer.len != sizeof(request_partial1));
    FAIL_IF(state->request_buffer.offset != 0);
    FAIL_IF(memcmp(state->request_buffer.buffer, request_partial1,
            sizeof(request_partial1)));

    /* There should not be a transaction yet. */
    FAIL_IF(state->transaction_max != 0);
    FAIL_IF(DNP3GetTx(state, 0) != NULL);

    /* Send the second partial. */
    SCMutexLock(&flow.m);
    r = AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
        STREAM_TOSERVER, request_partial2, sizeof(request_partial2));
    SCMutexUnlock(&flow.m);
    FAIL_IF(r != 0);

    /* The second partial completed the frame, the buffer should now
     * be clear. */
    FAIL_IF(state->request_buffer.len != 0);
    FAIL_IF(state->request_buffer.offset != 0);

    /* Should now have a complete transaction. */
    tx = DNP3GetTx(state, 0);
    FAIL_IF(tx == NULL);
    FAIL_IF(tx->tx_num != 1);
    FAIL_IF(tx != state->curr);
    FAIL_IF(tx->buffer == NULL);
    FAIL_IF(tx->buffer_len != 20);
    FAIL_IF(tx->ah.function_code != DNP3_APP_FC_DIR_OPERATE);

    /* Send partial response. */
    SCMutexLock(&flow.m);
    r = AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
        STREAM_TOCLIENT, response_partial1, sizeof(response_partial1));
    SCMutexUnlock(&flow.m);
    FAIL_IF(r != 0);
    FAIL_IF(state->response_buffer.len != sizeof(response_partial1));
    FAIL_IF(state->response_buffer.offset != 0);
    tx = DNP3GetTx(state, 1);
    FAIL_IF_NOT_NULL(tx);

    /* Send rest of response. */
    SCMutexLock(&flow.m);
    r = AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
        STREAM_TOCLIENT, response_partial2, sizeof(response_partial2));
    SCMutexUnlock(&flow.m);
    FAIL_IF(r != 0);

    /* Buffer should now be empty. */
    FAIL_IF(state->response_buffer.len != 0);
    FAIL_IF(state->response_buffer.offset != 0);

    /* There should now be a response transaction. */
    tx = DNP3GetTx(state, 1);
    FAIL_IF_NULL(tx);
    FAIL_IF(tx->buffer == NULL);
    FAIL_IF(tx->buffer_len == 0);

    AppLayerParserThreadCtxFree(alp_tctx);
    StreamTcpFreeConfig(true);
    FLOW_DESTROY(&flow);
    PASS;
}

/**
 * \test Test multiple DNP3 frames in one TCP read.
 */
static int DNP3ParserTestMultiFrame(void)
{
    DNP3State *state = NULL;

    /* Unsolicited response 1. */
    uint8_t unsol_response1[] = {
        0x05, 0x64, 0x16, 0x44, 0x01, 0x00, 0x02, 0x00,
        0x89, 0xe5, 0xc4, 0xfa, 0x82, 0x00, 0x00, 0x02,
        0x02, 0x17, 0x01, 0x01, 0x81, 0xa7, 0x75, 0xd8,
        0x32, 0x4c, 0x81, 0x3e, 0x01, 0xa1, 0xc9,
    };

    /* Unsolicited response 2. */
    uint8_t unsol_response2[] = {
        0x05, 0x64, 0x16, 0x44, 0x01, 0x00, 0x02, 0x00,
        0x89, 0xe5, 0xc5, 0xfb, 0x82, 0x00, 0x00, 0x02,
        0x02, 0x17, 0x01, 0x0c, 0x01, 0xd8, 0x75, 0xd8,
        0x32, 0x4c, 0xc9, 0x3c, 0x01, 0xa1, 0xc9,
    };

    uint8_t combined[sizeof(unsol_response1) + sizeof(unsol_response2)];
    memcpy(combined, unsol_response1, sizeof(unsol_response1));
    memcpy(combined + sizeof(unsol_response1), unsol_response2,
        sizeof(unsol_response2));

    /* Setup. */
    AppLayerParserThreadCtx *alp_tctx = AppLayerParserThreadCtxAlloc();
    Flow flow;
    TcpSession ssn;
    int r;
    memset(&flow, 0, sizeof(flow));
    memset(&ssn, 0, sizeof(ssn));
    flow.protoctx = (void *)&ssn;
    flow.proto = IPPROTO_TCP;
    flow.alproto = ALPROTO_DNP3;
    StreamTcpInitConfig(true);

    SCMutexLock(&flow.m);
    r = AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
        STREAM_TOCLIENT, combined, sizeof(combined));
    SCMutexUnlock(&flow.m);
    FAIL_IF(r != 0);

    state = flow.alstate;
    FAIL_IF(state == NULL);
    FAIL_IF(state->transaction_max != 2);

    AppLayerParserThreadCtxFree(alp_tctx);
    StreamTcpFreeConfig(true);
    FLOW_DESTROY(&flow);
    PASS;
}

/**
 * \test Test the parsing of a request PDU.
 *
 * The PDU under test contains a single read request object:
 * - Group: 1
 * - Variation: 0
 * - Count: 0
 */
static int DNP3ParserTestParsePDU01(void)
{
    /* Frame to be tested. This frame is a DNP3 request with one read
     * request data object, group 1, variation 0. */
    const uint8_t pkt[] = {
        0x05, 0x64,
        0x0b, 0xc4, 0x17, 0x00, 0xef, 0xff, 0xc4, 0x8f,
        0xe1, 0xc8, 0x01, 0x01, 0x00, 0x06, 0x77, 0x6e
    };

    DNP3State *dnp3state = DNP3StateAlloc(NULL, ALPROTO_UNKNOWN);
    int pdus = DNP3HandleRequestLinkLayer(NULL, dnp3state, pkt, sizeof(pkt));
    FAIL_IF(pdus < 1);
    DNP3Transaction *dnp3tx = DNP3GetTx(dnp3state, 0);
    FAIL_IF_NULL(dnp3tx);
    FAIL_IF(!dnp3tx->is_request);
    FAIL_IF(TAILQ_EMPTY(&dnp3tx->objects));
    DNP3Object *object = TAILQ_FIRST(&dnp3tx->objects);
    FAIL_IF(object->group != 1 || object->variation != 0);
    FAIL_IF(object->count != 0);

    DNP3StateFree(dnp3state);
    PASS;
}

/**
 * \test Test the decode of a DNP3 fragment with a single 70:3 object.
 */
static int DNP3ParserDecodeG70V3Test(void)
{
    const uint8_t pkt[] = {
        0x05, 0x64,
        0x63, 0xc4, 0x04, 0x00, 0x03, 0x00, 0xc7, 0xee,
        0xc7, 0xc9, 0x1b, 0x46, 0x03, 0x5b, 0x01, 0x55,
        0x00, 0x1a, 0x00, 0x3b, 0x00, 0x00, 0x00, 0x00,
        0x9e, 0xc7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0xff, 0xff, 0x00, 0x1e, 0x00, 0x43,
        0x3a, 0x2f, 0x74, 0x65, 0x6d, 0x70, 0x2f, 0x44,
        0x4e, 0x50, 0x44, 0x65, 0x67, 0x7d, 0x76, 0x69,
        0x63, 0x65, 0x43, 0x6f, 0x6e, 0x66, 0x69, 0x67,
        0x75, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x93, 0x0c,
        0x6e, 0x20, 0x77, 0x72, 0x69, 0x74, 0x74, 0x65,
        0x6e, 0x20, 0x74, 0x6f, 0x20, 0x52, 0x65, 0x6d,
        0x35, 0x20, 0x6f, 0x74, 0x65, 0x20, 0x44, 0x65,
        0x76, 0x69, 0x63, 0x65, 0x2e, 0x78, 0x6d, 0x6c,
        0xc4, 0x8b
    };

    DNP3State *dnp3state = DNP3StateAlloc(NULL, ALPROTO_UNKNOWN);
    FAIL_IF_NULL(dnp3state);
    int bytes = DNP3HandleRequestLinkLayer(NULL, dnp3state, pkt, sizeof(pkt));
    FAIL_IF(bytes != sizeof(pkt));
    DNP3Transaction *tx = DNP3GetTx(dnp3state, 0);
    FAIL_IF_NULL(tx);
    FAIL_IF_NOT(tx->is_request);
    DNP3Object *obj = TAILQ_FIRST(&tx->objects);
    FAIL_IF_NULL(obj);
    FAIL_IF_NOT(obj->group == 70);
    FAIL_IF_NOT(obj->variation == 3);
    FAIL_IF_NOT(obj->prefix_code == 0x5);
    FAIL_IF_NOT(obj->range_code == 0xb);
    FAIL_IF_NOT(obj->count == 1);
    DNP3Point *point = TAILQ_FIRST(obj->points);
    FAIL_IF_NULL(point);
    FAIL_IF_NOT(point->prefix == 85);
    FAIL_IF_NOT(point->size == 85);
    FAIL_IF_NULL(point->data);
    DNP3ObjectG70V3 *data = point->data;
    FAIL_IF_NOT(strcmp(
        data->filename,
        "C:/temp/DNPDeviceConfiguration written to Remote Device.xml") == 0);
    DNP3StateFree(dnp3state);
    PASS;
}

/**
 * \brief Test that an alert is raised on an unknown object.
 */
static int DNP3ParserUnknownEventAlertTest(void)
{
    /* Valid DNP3 frame with 70:3 object. */
    uint8_t pkt[] = {
        0x05, 0x64, 0x63, 0xc4, 0x04, 0x00, 0x03, 0x00,
        0xc7, 0xee,

        0xc7, 0xc9, 0x1b,

        /* Object and variation. Originally 70:3, now 70:99, an
         * unknown object. */
        0x46, 0x63,

        0x5b, 0x01, 0x55,
        0x00, 0x1a, 0x00, 0x3b, 0x00, 0x00, 0x00, 0x00,
        0x9e, 0xc7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0xff, 0xff, 0x00, 0x1e, 0x00, 0x43,
        0x3a, 0x2f, 0x74, 0x65, 0x6d, 0x70, 0x2f, 0x44,
        0x4e, 0x50, 0x44, 0x65, 0x67, 0x7d, 0x76, 0x69,
        0x63, 0x65, 0x43, 0x6f, 0x6e, 0x66, 0x69, 0x67,
        0x75, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x93, 0x0c,
        0x6e, 0x20, 0x77, 0x72, 0x69, 0x74, 0x74, 0x65,
        0x6e, 0x20, 0x74, 0x6f, 0x20, 0x52, 0x65, 0x6d,
        0x35, 0x20, 0x6f, 0x74, 0x65, 0x20, 0x44, 0x65,
        0x76, 0x69, 0x63, 0x65, 0x2e, 0x78, 0x6d, 0x6c,
        0xc4, 0x8b
    };

    DNP3FixCrc(pkt + 10, sizeof(pkt) - 10);

    DNP3State *dnp3state = DNP3StateAlloc(NULL, ALPROTO_UNKNOWN);
    FAIL_IF_NULL(dnp3state);
    int bytes = DNP3HandleRequestLinkLayer(NULL, dnp3state, pkt, sizeof(pkt));
    FAIL_IF(bytes != sizeof(pkt));

    DNP3StateFree(dnp3state);
    PASS;
}

/**
* \brief Test that an alert is raised on incorrect data.
*/
static int DNP3ParserIncorrectUserData(void)
{
    uint8_t packet_bytes[] = {
        0x05, 0x64, 0x08, 0xc4, 0x03, 0x00, 0x04, 0x00,
        0xbf, 0xe9, 0xc1, 0xc1, 0x82, 0xc5, 0xee
    };

    AppLayerParserThreadCtx *alp_tctx = AppLayerParserThreadCtxAlloc();
    Flow flow;
    TcpSession ssn;
    memset(&flow, 0, sizeof(flow));
    memset(&ssn, 0, sizeof(ssn));
    flow.protoctx = (void *)&ssn;
    flow.proto = IPPROTO_TCP;
    flow.alproto = ALPROTO_DNP3;
    StreamTcpInitConfig(true);

    int r = AppLayerParserParse(NULL, alp_tctx, &flow, ALPROTO_DNP3,
                                STREAM_TOCLIENT, packet_bytes, sizeof(packet_bytes));

    FAIL_IF(r == 0);

    AppLayerParserThreadCtxFree(alp_tctx);
    StreamTcpFreeConfig(true);
    FLOW_DESTROY(&flow);
    PASS;
}

#endif

void DNP3ParserRegisterTests(void)
{
#ifdef UNITTESTS
    UtRegisterTest("DNP3ParserTestCheckCRC", DNP3ParserTestCheckCRC);
    UtRegisterTest("DNP3ParserCheckLinkHeaderCRC",
                   DNP3ParserCheckLinkHeaderCRC);
    UtRegisterTest("DNP3CheckUserDataCRCsTest", DNP3CheckUserDataCRCsTest);
    UtRegisterTest("DNP3CalculateLinkLengthTest", DNP3CalculateLinkLengthTest);
    UtRegisterTest("DNP3CalculateTransportLengthWithoutCRCsTest",
                   DNP3CalculateTransportLengthWithoutCRCsTest);
    UtRegisterTest("DNP3ReassembleApplicationLayerTest01",
                   DNP3ReassembleApplicationLayerTest01);
    UtRegisterTest("DNP3ProbingParserTest", DNP3ProbingParserTest);
    UtRegisterTest("DNP3ParserTestRequestResponse",
                   DNP3ParserTestRequestResponse);
    UtRegisterTest("DNP3ParserTestUnsolicitedResponseConfirm",
                   DNP3ParserTestUnsolicitedResponseConfirm);
    UtRegisterTest("DNP3ParserTestPartialFrame", DNP3ParserTestPartialFrame);
    UtRegisterTest("DNP3ParserTestMultiFrame", DNP3ParserTestMultiFrame);
    UtRegisterTest("DNP3ParserTestFlooded", DNP3ParserTestFlooded);
    UtRegisterTest("DNP3ParserTestParsePDU01", DNP3ParserTestParsePDU01);
    UtRegisterTest("DNP3ParserDecodeG70V3Test", DNP3ParserDecodeG70V3Test);
    UtRegisterTest("DNP3ParserUnknownEventAlertTest",
        DNP3ParserUnknownEventAlertTest);
    UtRegisterTest("DNP3ParserIncorrectUserData", DNP3ParserIncorrectUserData);
#endif
}