/*

 *  $Id: libnet_build_ip.c,v 1.19 2004/04/13 17:32:28 mike Exp $

 *

 *  libnet

 *  libnet_build_ip.c - IP packet assembler

 *

 *  Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com>

 *  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 *

 */

#if (HAVE_CONFIG_H)

#include "../include/config.h"

#endif

#if (!(_WIN32) || (__CYGWIN__)) 

#include "../include/libnet.h"

#else

#include "../include/win32/libnet.h"

#endif

/* TODO len - should be calculated if -1 */

libnet_ptag_t

libnet_build_ipv4(uint16_t ip_len, uint8_t tos, uint16_t id, uint16_t frag,

uint8_t ttl, uint8_t prot, uint16_t sum, uint32_t src, uint32_t dst,

const uint8_t *payload, uint32_t payload_s, libnet_t *l, libnet_ptag_t ptag)

{

    uint32_t n = LIBNET_IPV4_H; /* size of memory block */

    libnet_pblock_t *p, *p_data, *p_temp;

    struct libnet_ipv4_hdr ip_hdr;

    libnet_ptag_t ptag_data = 0; /* used if there is ipv4 payload */

    libnet_ptag_t ptag_hold;

    if (l == NULL)

    { 

        return (-1);

    } 

    /*

     *  Find the existing protocol block if a ptag is specified, or create

     *  a new one.

     */

    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_IPV4_H);

    if (p == NULL)

    {

        return (-1);

    }

    memset(&ip_hdr, 0, sizeof(ip_hdr));

    ip_hdr.ip_v          = 4;      /* version 4 */

    ip_hdr.ip_hl         = 5;      /* 20 byte header,  measured in 32-bit words */

    /* check to see if there are IP options to include */

    if (p->prev)

    {

        if (p->prev->type == LIBNET_PBLOCK_IPO_H)

        {

            /* IPO block's length must be multiple of 4, or it's incorrectly

             * padded, in which case there is no "correct" IP header length,

             * it will too short or too long, we choose too short.

             */

            ip_hdr.ip_hl += p->prev->b_len / 4;

        }

    }

    /* Note that p->h_len is not adjusted. This seems a bug, but it is because

     * it is not used!  libnet_do_checksum() is passed the h_len (as `len'),

     * but for IPPROTO_IP it is ignored in favor of the ip_hl.

     */

    ip_hdr.ip_tos        = tos;                       /* IP tos */

    ip_hdr.ip_len        = htons(ip_len);             /* total length */

    ip_hdr.ip_id         = htons(id);                 /* IP ID */

    ip_hdr.ip_off        = htons(frag);               /* fragmentation flags */

    ip_hdr.ip_ttl        = ttl;                       /* time to live */

    ip_hdr.ip_p          = prot;                      /* transport protocol */

    ip_hdr.ip_sum        = (sum ? htons(sum) : 0);    /* checksum */

    ip_hdr.ip_src.s_addr = src;                       /* source ip */

    ip_hdr.ip_dst.s_addr = dst;                       /* destination ip */

    n = libnet_pblock_append(l, p, (uint8_t *)&ip_hdr, LIBNET_IPV4_H);

    if (n == -1)

    {

        goto bad;

    }

    /* save the original ptag value */

    ptag_hold = ptag;

    if (ptag == LIBNET_PTAG_INITIALIZER)

    {

        ptag = libnet_pblock_update(l, p, LIBNET_IPV4_H, LIBNET_PBLOCK_IPV4_H);

    }

    /* find and set the appropriate ptag, or else use the default of 0 */

    /* When updating the ipv4 block, we need to find the data block, and

     * adjust our ip_offset if the new payload size is different from what

     * it used to be.

     */

    if (ptag_hold && p->prev)

    {

        p_temp = p->prev;

        while (p_temp->prev &&

              (p_temp->type != LIBNET_PBLOCK_IPDATA) &&

              (p_temp->type != LIBNET_PBLOCK_IPV4_H))

        {

            p_temp = p_temp->prev;

        }

        if (p_temp->type == LIBNET_PBLOCK_IPDATA)

        {

            ptag_data = p_temp->ptag;

        }

        else

        {

             snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

                     "%s(): IPv4 data pblock not found\n", __func__);

        }

    }

    if (payload_s && !payload)

    {

         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

                 "%s(): payload inconsistency\n", __func__);

        goto bad;

    }

    if (payload_s)

    {

        /* update ptag_data with the new payload */

        /* on create:

         *    b_len = payload_s

         *    l->total_size += b_len

         *    h_len = 0

         * on update:

         *    b_len = payload_s

         *    h_len += <diff in size between new b_len and old b_len>

         *      increments if if b_len goes up, down if it goes down

         * in either case:

         *    copied = 0

	 */

        p_data = libnet_pblock_probe(l, ptag_data, payload_s,

                LIBNET_PBLOCK_IPDATA);

        if (p_data == NULL)

        {

            return (-1);

        }

        if (libnet_pblock_append(l, p_data, payload, payload_s) == -1)

        {

            goto bad;

        }

        if (ptag_data == LIBNET_PTAG_INITIALIZER)

        {

            /* IPDATA's h_len gets set to payload_s in both branches */

            if (p_data->prev->type == LIBNET_PBLOCK_IPV4_H)

            {

                libnet_pblock_update(l, p_data, payload_s,

                        LIBNET_PBLOCK_IPDATA);

                /* swap pblocks to correct the protocol order */

                libnet_pblock_swap(l, p->ptag, p_data->ptag); 

            }

            else

            {

                /* SR - I'm not sure how to reach this code. Maybe if the first

                 * time we added an ipv4 block, there was no payload, but when

                 * we modify the block the next time, we have payload?

		 */

                /* update without setting this as the final pblock */

                p_data->type  =  LIBNET_PBLOCK_IPDATA;

                p_data->ptag  =  ++(l->ptag_state);

                p_data->h_len =  payload_s; /* TODO dead code, data blocks don't have headers */

                /* data was added after the initial construction */

                for (p_temp = l->protocol_blocks;

                        p_temp->type == LIBNET_PBLOCK_IPV4_H ||

                        p_temp->type == LIBNET_PBLOCK_IPO_H;

                        p_temp = p_temp->next)

                {

                    libnet_pblock_insert_before(l, p_temp->ptag, p_data->ptag);

                    break;

                }

                /* the end block needs to have its next pointer cleared */

                l->pblock_end->next = NULL;

            }

            if (p_data->prev && p_data->prev->type == LIBNET_PBLOCK_IPO_H)

            {

                libnet_pblock_swap(l, p_data->prev->ptag, p_data->ptag); 

            }

        }

    }

    else

    {

        p_data = libnet_pblock_find(l, ptag_data);

        if (p_data) 

        {

            libnet_pblock_delete(l, p_data);

        }

        else

        {

            /* 

             * XXX - When this completes successfully, libnet errbuf contains 

             * an error message so to come correct, we'll clear it.

             */ 

            memset(l->err_buf, 0, sizeof (l->err_buf));

        }

    }

    if (sum == 0)

    {

        /*

         *  If checksum is zero, by default libnet will compute a checksum

         *  for the user.  The programmer can override this by calling

         *  libnet_toggle_checksum(l, ptag, 1);

         */

        libnet_pblock_setflags(p, LIBNET_PBLOCK_DO_CHECKSUM);

    }

    return (ptag);

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_autobuild_ipv4(uint16_t len, uint8_t prot, uint32_t dst, libnet_t *l)

{

    uint32_t n, i, j, src;

    uint16_t h;

    libnet_pblock_t *p;

    libnet_ptag_t ptag;

    struct libnet_ipv4_hdr ip_hdr;

    if (l == NULL)

    { 

        return (-1);

    } 

    n = LIBNET_IPV4_H;                                /* size of memory block */

    h = len;                                          /* header length */

    ptag = LIBNET_PTAG_INITIALIZER;

    src = libnet_get_ipaddr4(l);

    if (src == -1)

    {

        /* err msg set in libnet_get_ipaddr() */ 

        return (-1);

    }

    /*

     *  Create a new pblock.

     */

    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_IPV4_H);

    if (p == NULL)

    {

        return (-1);

    }

    memset(&ip_hdr, 0, sizeof(ip_hdr));

    ip_hdr.ip_v          = 4;                         /* version 4 */

    ip_hdr.ip_hl         = 5;                         /* 20 byte header */

    /* check to see if there are IP options to include */

    if (p->prev)

    {

        if (p->prev->type == LIBNET_PBLOCK_IPO_H)

        {

            /*

             *  Count up number of 32-bit words in options list, padding if

             *  neccessary.

             */

            for (i = 0, j = 0; i < p->prev->b_len; i++)

            {

                (i % 4) ? j : j++;

            }

            ip_hdr.ip_hl += j;

        }

    }

    ip_hdr.ip_tos        = 0;                         /* IP tos */

    ip_hdr.ip_len        = htons(h);                  /* total length */

    ip_hdr.ip_id         = htons((l->ptag_state) & 0x0000ffff); /* IP ID */

    ip_hdr.ip_off        = 0;                         /* fragmentation flags */

    ip_hdr.ip_ttl        = 64;                        /* time to live */

    ip_hdr.ip_p          = prot;                      /* transport protocol */

    ip_hdr.ip_sum        = 0;                         /* checksum */

    ip_hdr.ip_src.s_addr = src;                       /* source ip */

    ip_hdr.ip_dst.s_addr = dst;                       /* destination ip */

    n = libnet_pblock_append(l, p, (uint8_t *)&ip_hdr, LIBNET_IPV4_H);

    if (n == -1)

    {

        goto bad;

    }

    libnet_pblock_setflags(p, LIBNET_PBLOCK_DO_CHECKSUM);

    ptag = libnet_pblock_update(l, p, LIBNET_IPV4_H, LIBNET_PBLOCK_IPV4_H);

    return (ptag);

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_build_ipv4_options(const uint8_t *options, uint32_t options_s, libnet_t *l, 

libnet_ptag_t ptag)

{

    int options_size_increase = 0; /* increase will be negative if it's a decrease */

    uint32_t n, adj_size;

    libnet_pblock_t *p, *p_temp;

    struct libnet_ipv4_hdr *ip_hdr;

    if (l == NULL)

    { 

        return (-1);

    }

    /* check options list size */

    if (options_s > LIBNET_MAXOPTION_SIZE)

    {

        snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

            "%s(): options list is too large %d\n", __func__, options_s);

        return (-1);

    }

    adj_size = options_s;

    if (adj_size % 4)

    {

        /* size of memory block with padding */

        adj_size += 4 - (options_s % 4);

    }

    /* if this pblock already exists, determine if there is a size diff */

    if (ptag)

    {

        p_temp = libnet_pblock_find(l, ptag);

        if (p_temp)

        {

            options_size_increase = adj_size - p_temp->b_len;

        }

    }

    /* If we aren't modifying an options block, we are pushing a new one, and

     * since it must be pushed before the IPv4 block is pushed, there is no

     * need to remember that options size has "increased".

     */

    /*

     *  Find the existing protocol block if a ptag is specified, or create

     *  a new one.

     */

    p = libnet_pblock_probe(l, ptag, adj_size, LIBNET_PBLOCK_IPO_H);

    if (p == NULL)

    {

        return (-1);

    }

    /* append options */

    n = libnet_pblock_append(l, p, options, options_s);

    if (n == -1)

    {

        goto bad;

    }

    /* append padding */

    n = libnet_pblock_append(l, p, (uint8_t*)"\0\0\0", adj_size - options_s);

    if (n == -1)

    {

        goto bad;

    }

    if (ptag && p->next)

    {

        p_temp = p->next;

        /* fix the IP header sizes */

        if (p_temp->type == LIBNET_PBLOCK_IPV4_H)

        {

            ip_hdr = (struct libnet_ipv4_hdr *) p_temp->buf;

            ip_hdr->ip_hl = 5 + adj_size / 4; /* 4 bits wide, so no byte order concerns */

            ip_hdr->ip_len = htons(ntohs(ip_hdr->ip_len) + options_size_increase);

            p_temp->h_len = ip_hdr->ip_hl * 4; /* Dead code, h_len isn't used for IPv4 block */

        }

    }

    return (ptag ? ptag : libnet_pblock_update(l, p, adj_size,

            LIBNET_PBLOCK_IPO_H));

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_build_ipv6(uint8_t tc, uint32_t fl, uint16_t len, uint8_t nh,

uint8_t hl, struct libnet_in6_addr src, struct libnet_in6_addr dst, 

const uint8_t *payload, uint32_t payload_s, libnet_t *l, libnet_ptag_t ptag)

{   

    uint32_t n;

    libnet_pblock_t *p;

    struct libnet_ipv6_hdr ip_hdr;

    if (l == NULL)

    {

        return (-1);

    }

    n = LIBNET_IPV6_H + payload_s;          /* size of memory block */

    if (LIBNET_IPV6_H + payload_s > IP_MAXPACKET)

    {  

         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

                 "%s(): IP packet too large\n", __func__);

        return (-1);

    }  

    /*

     *  Find the existing protocol block if a ptag is specified, or create

     *  a new one.

     */

    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_IPV6_H);

    if (p == NULL)

    {   

        return (-1);

    }  

    memset(&ip_hdr, 0, sizeof(ip_hdr));

    ip_hdr.ip_flags[0] = (0x06 << 4) | ((tc & 0xF0) >> 4);

    ip_hdr.ip_flags[1] = ((tc & 0x0F) << 4) | ((fl & 0xF0000) >> 16);

    ip_hdr.ip_flags[2] = fl & 0x0FF00 >> 8;

    ip_hdr.ip_flags[3] = fl & 0x000FF;

    ip_hdr.ip_len      = htons(len);

    ip_hdr.ip_nh       = nh;

    ip_hdr.ip_hl       = hl;

    ip_hdr.ip_src      = src;

    ip_hdr.ip_dst      = dst;

    n = libnet_pblock_append(l, p, (uint8_t *)&ip_hdr, LIBNET_IPV6_H);

    if (n == -1)

    {

        goto bad;

    }

    /* boilerplate payload sanity check / append macro */

    LIBNET_DO_PAYLOAD(l, p);

    /* no checksum for IPv6 */

    ptag = ptag ? ptag : libnet_pblock_update(l, p, LIBNET_IPV6_H,

            LIBNET_PBLOCK_IPV6_H);

    return ptag;

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_build_ipv6_frag(uint8_t nh, uint8_t reserved, uint16_t frag,

uint32_t id, const uint8_t *payload, uint32_t payload_s, libnet_t *l,

libnet_ptag_t ptag)

{

    uint32_t n;

    uint16_t h;

    libnet_pblock_t *p;

    struct libnet_ipv6_frag_hdr ipv6_frag_hdr;

    if (l == NULL)

    { 

        return (-1);

    }

    n = LIBNET_IPV6_FRAG_H + payload_s;

    h = 0; 

    if (LIBNET_IPV6_FRAG_H + payload_s > IP_MAXPACKET)

    {

         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

                 "%s(): IP packet too large\n", __func__);

        return (-1);

    }

    /*

     *  Find the existing protocol block if a ptag is specified, or create

     *  a new one.

     */

    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_IPV6_FRAG_H);

    if (p == NULL)

    {

        return (-1);

    }

    memset(&ipv6_frag_hdr, 0 , sizeof(ipv6_frag_hdr));

    ipv6_frag_hdr.ip_nh       = nh;

    ipv6_frag_hdr.ip_reserved = reserved;

    ipv6_frag_hdr.ip_frag     = frag;

    ipv6_frag_hdr.ip_id       = id;

    /*

     *  Appened the protocol unit to the list.

     */

    n = libnet_pblock_append(l, p, (uint8_t *)&ipv6_frag_hdr,

        LIBNET_IPV6_FRAG_H);

    if (n == -1)

    {

        goto bad;

    }

    /* boilerplate payload sanity check / append macro */

    LIBNET_DO_PAYLOAD(l, p);

    /*

     *  Update the protocol block's meta information and return the protocol

     *  tag id of this pblock.  This tag will be used to locate the pblock

     *  in order to modify the protocol header in subsequent calls.

     */

    return (ptag ? ptag : libnet_pblock_update(l, p, h, 

            LIBNET_PBLOCK_IPV6_FRAG_H));

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_build_ipv6_routing(uint8_t nh, uint8_t len, uint8_t rtype, 

uint8_t segments, const uint8_t *payload, uint32_t payload_s, libnet_t *l,

libnet_ptag_t ptag)

{

    uint32_t n;

    uint16_t h;

    libnet_pblock_t *p;

    struct libnet_ipv6_routing_hdr ipv6_routing_hdr;

    if (l == NULL)

    { 

        return (-1);

    }

    /* Important: IPv6 routing header routes are specified using the payload

     * interface!

     */

    n = LIBNET_IPV6_ROUTING_H + payload_s;

    h = 0;

    if (LIBNET_IPV6_ROUTING_H + payload_s > IP_MAXPACKET)

    {

         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

                 "%s(): IP packet too large\n", __func__);

        return (-1);

    }

    /*

     *  Find the existing protocol block if a ptag is specified, or create

     *  a new one.

     */

    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_IPV6_ROUTING_H);

    if (p == NULL)

    {

        return (-1);

    }

    memset(&ipv6_routing_hdr, 0 , sizeof(ipv6_routing_hdr));

    ipv6_routing_hdr.ip_nh       = nh;

    ipv6_routing_hdr.ip_len      = len;

    ipv6_routing_hdr.ip_rtype    = rtype;

    ipv6_routing_hdr.ip_segments = segments;

    /*

     *  Appened the protocol unit to the list.

     */

    n = libnet_pblock_append(l, p, (uint8_t *)&ipv6_routing_hdr,

        LIBNET_IPV6_ROUTING_H);

    if (n == -1)

    {

        goto bad;

    }

    /* boilerplate payload sanity check / append macro */

    LIBNET_DO_PAYLOAD(l, p);

    /*

     *  Update the protocol block's meta information and return the protocol

     *  tag id of this pblock.  This tag will be used to locate the pblock

     *  in order to modify the protocol header in subsequent calls.

     */

    return (ptag ? ptag : libnet_pblock_update(l, p, h, 

            LIBNET_PBLOCK_IPV6_ROUTING_H));

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_build_ipv6_destopts(uint8_t nh, uint8_t len, const uint8_t *payload,

uint32_t payload_s, libnet_t *l, libnet_ptag_t ptag)

{

    uint32_t n;

    uint16_t h;

    libnet_pblock_t *p;

    struct libnet_ipv6_destopts_hdr ipv6_destopts_hdr;

    if (l == NULL)

    { 

        return (-1);

    }

    /* Important: IPv6 dest opts information is specified using the payload

     * interface!

     */

    n = LIBNET_IPV6_DESTOPTS_H + payload_s;

    h = 0;

    if (LIBNET_IPV6_DESTOPTS_H + payload_s > IP_MAXPACKET)

    {

         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

                 "%s(): IP packet too large\n", __func__);

        return (-1);

    }

    /*

     *  Find the existing protocol block if a ptag is specified, or create

     *  a new one.

     */

    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_IPV6_DESTOPTS_H);

    if (p == NULL)

    {

        return (-1);

    }

    memset(&ipv6_destopts_hdr, 0 , sizeof(ipv6_destopts_hdr));

    ipv6_destopts_hdr.ip_nh  = nh;

    ipv6_destopts_hdr.ip_len = len;

    /*

     *  Appened the protocol unit to the list.

     */

    n = libnet_pblock_append(l, p, (uint8_t *)&ipv6_destopts_hdr,

        LIBNET_IPV6_DESTOPTS_H);

    if (n == -1)

    {

        goto bad;

    }

    /* boilerplate payload sanity check / append macro */

    LIBNET_DO_PAYLOAD(l, p);

    /*

     *  Update the protocol block's meta information and return the protocol

     *  tag id of this pblock.  This tag will be used to locate the pblock

     *  in order to modify the protocol header in subsequent calls.

     */

    return (ptag ? ptag : libnet_pblock_update(l, p, h, 

            LIBNET_PBLOCK_IPV6_DESTOPTS_H));

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_build_ipv6_hbhopts(uint8_t nh, uint8_t len, const uint8_t *payload,

uint32_t payload_s, libnet_t *l, libnet_ptag_t ptag)

{

    uint32_t n;

    uint16_t h;

    libnet_pblock_t *p;

    struct libnet_ipv6_hbhopts_hdr ipv6_hbhopts_hdr;

    if (l == NULL)

    { 

        return (-1);

    }

    /* Important: IPv6 hop by hop opts information is specified using the

     * payload interface!

     */

    n = LIBNET_IPV6_HBHOPTS_H + payload_s;

    h = 0;

    if (LIBNET_IPV6_HBHOPTS_H + payload_s > IP_MAXPACKET)

    {

         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,

                 "%s(): IP packet too large\n", __func__);

        return (-1);

    }

    /*

     *  Find the existing protocol block if a ptag is specified, or create

     *  a new one.

     */

    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_IPV6_HBHOPTS_H);

    if (p == NULL)

    {

        return (-1);

    }

    memset(&ipv6_hbhopts_hdr, 0 , sizeof(ipv6_hbhopts_hdr));

    ipv6_hbhopts_hdr.ip_nh  = nh;

    ipv6_hbhopts_hdr.ip_len = len;

    /*

     *  Appened the protocol unit to the list.

     */

    n = libnet_pblock_append(l, p, (uint8_t *)&ipv6_hbhopts_hdr,

        LIBNET_IPV6_HBHOPTS_H);

    if (n == -1)

    {

        goto bad;

    }

    /* boilerplate payload sanity check / append macro */

    LIBNET_DO_PAYLOAD(l, p);

    /*

     *  Update the protocol block's meta information and return the protocol

     *  tag id of this pblock.  This tag will be used to locate the pblock

     *  in order to modify the protocol header in subsequent calls.

     */

    return (ptag ? ptag : libnet_pblock_update(l, p, h, 

            LIBNET_PBLOCK_IPV6_HBHOPTS_H));

bad:

    libnet_pblock_delete(l, p);

    return (-1);

}

libnet_ptag_t

libnet_autobuild_ipv6(uint16_t len, uint8_t nh, struct libnet_in6_addr dst,

            libnet_t *l, libnet_ptag_t ptag)

{

    struct libnet_in6_addr src;

    src = libnet_get_ipaddr6(l);

    if (libnet_in6_is_error(src))

    {

        return (-1);

    }

    return libnet_build_ipv6(0, 0, len, nh, 64, src, dst, NULL, 0, l, ptag);

}