encode.c

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/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: f1b1cd6985aff6a2f6ddc468743f8db327ba5d01 $
 *
 * @file protocols/dhcpv6/encode.c
 * @brief Functions to encode DHCP options.
 *
 * @author Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 *
 * @copyright 2018 The freeradius server project
 * @copyright 2018 NetworkRADIUS SARL (legal@networkradius.com)
 */
#include <stdint.h>
#include <stddef.h>
#include <freeradius-devel/io/test_point.h>
#include <freeradius-devel/util/dbuff.h>
#include <freeradius-devel/util/dns.h>
#include <freeradius-devel/util/proto.h>
#include <freeradius-devel/util/struct.h>
#include <freeradius-devel/util/encode.h>
 
#include "dhcpv6.h"
#include "attrs.h"
 
static ssize_t encode_value(fr_dbuff_t *dbuff,
                            fr_da_stack_t *da_stack, unsigned int depth,
                            fr_dcursor_t *cursor, void *encode_ctx);
 
static ssize_t encode_rfc(fr_dbuff_t *dbuff,
                              fr_da_stack_t *da_stack, unsigned int depth,
                              fr_dcursor_t *cursor, void *encode_ctx);
 
static ssize_t encode_tlv(fr_dbuff_t *dbuff,
                              fr_da_stack_t *da_stack, unsigned int depth,
                              fr_dcursor_t *cursor, void *encode_ctx);
 
static ssize_t encode_child(fr_dbuff_t *dbuff,
                                  fr_da_stack_t *da_stack, unsigned int depth,
                                  fr_dcursor_t *cursor, void *encode_ctx);
 
/** Macro-like function for encoding an option header
 *
 *    0                   1                   2                   3
 *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *   |          option-code          |           option-len          |
 *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * @param[out] m                Where to write the 4 byte option header.
 * @param[in] option            The option number (host byte order).
 * @param[in] data_len          The length of the option (host byte order).
 * @return
 *      - <0    How much data would have been required as a negative value.
 *      - 4     The length of data written.
 */
static inline ssize_t encode_option_hdr(fr_dbuff_marker_t *m, uint16_t option, size_t data_len)
{
        FR_DBUFF_IN_RETURN(m, option);
        FR_DBUFF_IN_RETURN(m, (uint16_t) data_len);
 
        return sizeof(option) + sizeof(uint16_t);
}
 
 
static ssize_t encode_value(fr_dbuff_t *dbuff,
                            fr_da_stack_t *da_stack, unsigned int depth,
                            fr_dcursor_t *cursor, void *encode_ctx)
{
        ssize_t                 slen;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_pair_t const         *vp = fr_dcursor_current(cursor);
        fr_dict_attr_t const    *da = da_stack->da[depth];
 
        PAIR_VERIFY(vp);
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        /*
         *      Pack multiple attributes into into a single option
         */
        if ((vp->vp_type == FR_TYPE_STRUCT) || (da->type == FR_TYPE_STRUCT)) {
                slen = fr_struct_to_network(&work_dbuff, da_stack, depth, cursor, encode_ctx, encode_value, encode_child);
                if (slen <= 0) return slen;
 
                vp = fr_dcursor_current(cursor);
                fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
                return fr_dbuff_set(dbuff, &work_dbuff);
        }
 
        /*
         *      If it's not a TLV, it should be a value type RFC
         *      attribute make sure that it is.
         */
        if (da_stack->da[depth + 1] != NULL) {
                fr_strerror_printf("%s: Encoding value but not at top of stack", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        if (vp->da != da) {
                fr_strerror_printf("%s: Top of stack does not match vp->da", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        switch (vp->vp_type) {
        case FR_TYPE_ATTR:
                FR_DBUFF_IN_RETURN(&work_dbuff, (uint16_t) vp->vp_attr->attr);
                break;
 
        case FR_TYPE_TLV:
        case FR_TYPE_VENDOR:
        case FR_TYPE_VSA:
                fr_strerror_printf("%s: Called with structural type %s", __FUNCTION__,
                                   fr_type_to_str(da->type));
                return PAIR_ENCODE_FATAL_ERROR;
 
        /*
         *    0                   1                   2                   3
         *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |          option-code          |          option-len           |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   .                            String                             .
         *   |                              ...                              |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_STRING:
                /*
                 *      DNS labels get a special encoder.  DNS labels
                 *      MUST NOT be compressed in DHCP.
                 *
                 *      https://tools.ietf.org/html/rfc8415#section-10
                 */
                if (fr_dhcpv6_flag_any_dns_label(da)) {
                        fr_dbuff_marker_t       last_byte, src;
 
                        fr_dbuff_marker(&last_byte, &work_dbuff);
                        fr_dbuff_marker(&src, &work_dbuff);
                        slen = fr_dns_label_from_value_box_dbuff(&work_dbuff, false, &vp->data, NULL);
                        if (slen < 0) return slen;
 
                        /*
                         *      RFC 4704 says "FQDN", unless it's a
                         *      single label, in which case it's a
                         *      partial name, and we omit the trailing
                         *      zero.
                         */
                        if (fr_dhcpv6_flag_partial_dns_label(da) && slen > 0) {
                                uint8_t c = 0;
 
                                fr_dbuff_advance(&last_byte, (size_t)(slen - 1));
                                fr_dbuff_set(&src, &last_byte);
                                fr_dbuff_out(&c, &src);
                                if (!c) fr_dbuff_set(&work_dbuff, &last_byte);
                        }
                        break;
                }
                goto to_network;
 
        /*
         * Common encoder might add scope byte, so we just copy the address portion
         *
         *    0                   1                   2                   3
         *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |          option-code          |           option-len          |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |                                                               |
         *   |                         ipv6-address                          |
         *   |                                                               |
         *   |                                                               |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_IPV6_ADDR:
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, vp->vp_ipv6addr, sizeof(vp->vp_ipv6addr));
                break;
 
        /*
         *      Common encoder doesn't add a reserved byte after prefix, but it also
         *      doesn't do the variable length encoding required.
         *
         *      0                   1                   2                   3
         *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *     |          option-code          |         option-length         |
         *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *     |  prefix6len   |              ipv6-prefix                      |
         *     +-+-+-+-+-+-+-+-+           (variable length)                   |
         *     .                                                               .
         *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_IPV6_PREFIX:
        {
                size_t  prefix_len;
 
                /*
                 *      Structs have fixed length value fields.
                 */
                if (da->parent->type == FR_TYPE_STRUCT) {
                        prefix_len = sizeof(vp->vp_ipv6addr);
                } else {
                        prefix_len = fr_bytes_from_bits(vp->vp_ip.prefix);
                }
 
                FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, vp->vp_ip.prefix);
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, (uint8_t const *)&vp->vp_ipv6addr, prefix_len); /* Only copy the minimum address bytes required */
        }
                break;
 
        /*
         *      Not actually specified by the DHCPv6 RFC, but will probably come
         *      in handy at some point if we need to have the DHCPv6 server
         *      hand out v4 prefixes.
         */
        case FR_TYPE_IPV4_PREFIX:
        {
                size_t prefix_len;
 
                /*
                 *      Structs have fixed length value fields.
                 */
                if (da->parent->type == FR_TYPE_STRUCT) {
                        prefix_len = sizeof(vp->vp_ipv4addr);
                } else {
                        prefix_len = fr_bytes_from_bits(vp->vp_ip.prefix);
                }
 
                FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, vp->vp_ip.prefix);
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, (uint8_t const *)&vp->vp_ipv4addr, prefix_len);  /* Only copy the minimum address bytes required */
        }
                break;
 
        /*
         *    0                   1                   2                   3
         *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |          option-code          |           option-len          |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_BOOL:
                /*
                 *      Don't encode anything!  The mere existence of
                 *      the attribute signifies a "true" value.
                 */
                break;
 
        /*
         *      A standard 32bit integer, but unlike normal UNIX timestamps
         *      starts from the 1st of January 2000.
         *
         *      In the decoder we add 30 years to any values, so here
         *      we need to subtract that time, or if the value is less
         *      than that time, just encode a 0x0000000000
         *      value.
         */
        case FR_TYPE_DATE:
        {
                uint64_t date = fr_unix_time_to_sec(vp->vp_date);
 
                if (date < DHCPV6_DATE_OFFSET) {        /* 30 years */
                        FR_DBUFF_IN_RETURN(&work_dbuff, (uint32_t) 0);
                        break;
                }
 
                FR_DBUFF_IN_RETURN(&work_dbuff, (uint32_t)(date - DHCPV6_DATE_OFFSET));
        }
                break;
 
        case FR_TYPE_GROUP:
        {
                fr_dcursor_t child_cursor;
                fr_dict_attr_t const *ref = fr_dict_attr_ref(vp->da);
 
                if (ref && (ref->dict != dict_dhcpv6)) {
                        slen = fr_pair_ref_to_network(&work_dbuff, da_stack, depth, cursor);
                        if (slen < 0) return PAIR_ENCODE_FATAL_ERROR;
                        break;
                }
 
                /*
                 *      Encode the child options.
                 */
                if (!fr_pair_list_empty(&vp->vp_group)) {
                        (void) fr_pair_dcursor_child_iter_init(&child_cursor, &vp->vp_group, cursor);
 
                        /*
                         *      @todo - encode from "ref" and not from the root?  But that's hard,
                         *      due to the whole proto stack thing, which we largely don't need
                         *      any more.
                         */
                        while (fr_dcursor_current(&child_cursor) != NULL) {
                                slen = fr_dhcpv6_encode_option(&work_dbuff, &child_cursor, encode_ctx);
 
                                if (slen < 0) return PAIR_ENCODE_FATAL_ERROR;
                        }
                }
        }
                break;
 
        /*
         *      The value_box functions will take care of fixed-width
         *      "string" and "octets" options.
         */
        to_network:
        case FR_TYPE_OCTETS:
                /*
                 *      Hack until we find all places that don't set data.enumv
                 */
                if (vp->da->flags.length && (vp->data.enumv != vp->da)) {
                        fr_dict_attr_t const * const *c = &vp->data.enumv;
                        fr_dict_attr_t **u;
 
                        memcpy(&u, &c, sizeof(c)); /* const issues */
                        memcpy(u, &vp->da, sizeof(vp->da));
                }
                FALL_THROUGH;
 
        /*
         *    0                   1                   2                   3
         *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |          option-code          |          option-len           |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   | 8-bit-integer |
         *   +-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_UINT8:
 
        /*
         *    0                   1                   2                   3
         *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |          option-code          |           option-len          |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |         16-bit-integer        |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_UINT16:
        /*
         *    0                   1                   2                   3
         *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *    |          option-code          |           option-len          |
         *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *    |                         32-bit-integer                        |
         *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        case FR_TYPE_UINT32:
        default:
                slen = fr_value_box_to_network(&work_dbuff, &vp->data);
                if (slen < 0) return PAIR_ENCODE_FATAL_ERROR;
                break;
        }
 
        /*
         *      Rebuilds the TLV stack for encoding the next attribute
         */
        vp = fr_dcursor_next(cursor);
        fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
 
static ssize_t encode_vsio(fr_dbuff_t *dbuff,
                               fr_da_stack_t *da_stack, unsigned int depth,
                               fr_dcursor_t *cursor, void *encode_ctx);
 
static ssize_t encode_child(fr_dbuff_t *dbuff,
                                  fr_da_stack_t *da_stack, unsigned int depth,
                                  fr_dcursor_t *cursor, void *encode_ctx)
{
        ssize_t len;
        fr_pair_t *vp = fr_dcursor_current(cursor);
        fr_dcursor_t child_cursor;
        fr_dbuff_t work_dbuff;
 
        if (da_stack->da[depth]) {
                /*
                 *      Determine the nested type and call the appropriate encoder
                 */
                switch (da_stack->da[depth]->type) {
                case FR_TYPE_TLV:
                        if (!da_stack->da[depth + 1]) break;
 
                        return encode_tlv(dbuff, da_stack, depth, cursor, encode_ctx);
 
                case FR_TYPE_VSA:
                        if (!da_stack->da[depth + 1]) break;
 
                        return encode_vsio(dbuff, da_stack, depth, cursor, encode_ctx);
 
                case FR_TYPE_GROUP:
                        if (!da_stack->da[depth + 1]) break;
                        FALL_THROUGH;
 
                default:
                        return encode_rfc(dbuff, da_stack, depth, cursor, encode_ctx);
                }
        }
 
        fr_assert(fr_type_is_structural(vp->vp_type));
 
        fr_pair_dcursor_child_iter_init(&child_cursor, &vp->vp_group, cursor);
        work_dbuff = FR_DBUFF(dbuff);
 
        while ((vp = fr_dcursor_current(&child_cursor)) != NULL) {
                fr_proto_da_stack_build(da_stack, vp->da);
 
                switch (da_stack->da[depth]->type) {
                case FR_TYPE_VSA:
                        len = encode_vsio(&work_dbuff, da_stack, depth, &child_cursor, encode_ctx);
                        break;
 
                case FR_TYPE_TLV:
                        len = encode_tlv(&work_dbuff, da_stack, depth, &child_cursor, encode_ctx);
                        break;
 
                default:
                        len = encode_rfc(&work_dbuff, da_stack, depth, &child_cursor, encode_ctx);
                        break;
                }
 
                if (len <= 0) return len;
        }
 
        /*
         *      Skip over the attribute we just encoded.
         */
        vp = fr_dcursor_next(cursor);
        fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Encode an RFC format TLV.
 *
 * This could be a standard attribute, or a TLV data type.
 * If it's a standard attribute, then vp->da->attr == attribute.
 * Otherwise, attribute may be something else.
 */
static ssize_t encode_rfc(fr_dbuff_t *dbuff,
                              fr_da_stack_t *da_stack, unsigned int depth,
                              fr_dcursor_t *cursor, void *encode_ctx)
{
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_marker_t       hdr;
        fr_dict_attr_t const    *da = da_stack->da[depth];
        ssize_t                 slen;
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
        fr_dbuff_marker(&hdr, &work_dbuff);
 
        /*
         *      Make space for the header...
         */
        FR_DBUFF_EXTEND_LOWAT_OR_RETURN(&work_dbuff, DHCPV6_OPT_HDR_LEN);
        fr_dbuff_advance(&work_dbuff, DHCPV6_OPT_HDR_LEN);
 
        /*
         *      Write out the option's value
         */
        if (da->flags.array) {
                slen = fr_pair_array_to_network(&work_dbuff, da_stack, depth, cursor, encode_ctx, encode_value);
        } else {
                slen = encode_value(&work_dbuff, da_stack, depth, cursor, encode_ctx);
        }
        if (slen < 0) return slen;
 
        /*
         *      Write out the option number and length (before the value we just wrote)
         */
        (void) encode_option_hdr(&hdr, (uint16_t)da->attr, (uint16_t) (fr_dbuff_used(&work_dbuff) - DHCPV6_OPT_HDR_LEN));
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Done RFC header");
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
static ssize_t encode_tlv(fr_dbuff_t *dbuff,
                              fr_da_stack_t *da_stack, unsigned int depth,
                              fr_dcursor_t *cursor, void *encode_ctx)
{
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_marker_t       hdr;
        fr_dict_attr_t const    *da = da_stack->da[depth];
        ssize_t                 len;
 
        fr_dbuff_marker(&hdr, &work_dbuff);
        PAIR_VERIFY(fr_dcursor_current(cursor));
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        if (da_stack->da[depth]->type != FR_TYPE_TLV) {
                fr_strerror_printf("%s: Expected type \"tlv\" got \"%s\"", __FUNCTION__,
                                   fr_type_to_str(da_stack->da[depth]->type));
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        if (!da_stack->da[depth + 1]) {
                fr_strerror_printf("%s: Can't encode empty TLV", __FUNCTION__);
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        FR_DBUFF_ADVANCE_RETURN(&work_dbuff, DHCPV6_OPT_HDR_LEN);       /* Make room for option header */
 
        len = fr_pair_cursor_to_network(&work_dbuff, da_stack, depth, cursor, encode_ctx, encode_child);
        if (len < 0) return len;
 
        /*
         *    0                   1                   2                   3
         *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *   |          option-code          |           option-len          |
         *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        (void) encode_option_hdr(&hdr, (uint16_t)da->attr, (uint16_t) (fr_dbuff_used(&work_dbuff) - DHCPV6_OPT_HDR_LEN));
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Done TLV header");
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Encode a Vendor-Specific Information Option
 *
 *     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |      OPTION_VENDOR_OPTS       |           option-len          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       enterprise-number                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     .                                                               .
 *     .                          option-data                          .
 *     .                                                               .
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 */
static ssize_t encode_vsio(fr_dbuff_t *dbuff,
                               fr_da_stack_t *da_stack, unsigned int depth,
                               fr_dcursor_t *cursor, void *encode_ctx)
{
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_marker_t       hdr;
        fr_dict_attr_t const    *da = da_stack->da[depth];
        fr_dict_attr_t const    *dv;
        ssize_t                 len;
 
        fr_dbuff_marker(&hdr, &work_dbuff);
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        /*
         *      DA should be a VSA type with the value of OPTION_VENDOR_OPTS.
         */
        if (da->type != FR_TYPE_VSA) {
                fr_strerror_printf("%s: Expected type \"vsa\" got \"%s\"", __FUNCTION__,
                                   fr_type_to_str(da->type));
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        /*
         *      Now process the vendor ID part (which is one attribute deeper)
         */
        dv = da_stack->da[++depth];
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        if (dv->type != FR_TYPE_VENDOR) {
                fr_strerror_printf("%s: Expected type \"vsa\" got \"%s\"", __FUNCTION__,
                                   fr_type_to_str(dv->type));
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        FR_DBUFF_EXTEND_LOWAT_OR_RETURN(&work_dbuff, DHCPV6_OPT_HDR_LEN);
        fr_dbuff_advance(&work_dbuff, DHCPV6_OPT_HDR_LEN);
        FR_DBUFF_IN_RETURN(&work_dbuff, dv->attr);
 
        /*
         *      https://tools.ietf.org/html/rfc8415#section-21.17 says:
         *
         *   The vendor-option-data field MUST be encoded as a sequence of
         *   code/length/value fields of format identical to the DHCP options (see
         *   Section 21.1).  The sub-option codes are defined by the vendor
         *   identified in the enterprise-number field and are not managed by
         *   IANA.  Each of the sub-options is formatted as follows:
         *
         *       0                   1                   2                   3
         *       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      |          sub-opt-code         |         sub-option-len        |
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *      .                                                               .
         *      .                        sub-option-data                        .
         *      .                                                               .
         *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
 
        /*
         *      Encode the different data types
         */
        len = encode_child(&work_dbuff, da_stack, depth + 1, cursor, encode_ctx);
        if (len < 0) return len;
 
        (void) encode_option_hdr(&hdr, da->attr, fr_dbuff_used(&work_dbuff) - DHCPV6_OPT_HDR_LEN);
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Done VSIO header");
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Encode a Relay-Message
 *
 *      Header + stuff
 */
static ssize_t encode_relay_message(fr_dbuff_t *dbuff,
                                    fr_da_stack_t *da_stack, unsigned int depth,
                                    fr_dcursor_t *cursor, UNUSED void *encode_ctx)
{
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_marker_t       len_m;
        ssize_t                 slen;
 
        fr_dict_attr_t const    *da = da_stack->da[depth];
        fr_pair_t               *vp;
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        /*
         *      Skip empty relay messages...
         *      This shouldn't really happen.
         */
        vp = fr_dcursor_current(cursor);
        if (fr_pair_list_empty(&vp->vp_group)) {
                vp = fr_dcursor_next(cursor);
                fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
                return 0;
        }
 
        /*
         *      Write out the header
         */
        FR_DBUFF_IN_RETURN(&work_dbuff, (uint16_t)da->attr);    /* Write out the option header */
        fr_dbuff_marker(&len_m, &work_dbuff);                   /* Mark where we'll need to put the length field */
        FR_DBUFF_ADVANCE_RETURN(&work_dbuff, 2);                /* Advanced past the length field */
 
        vp = fr_dcursor_current(cursor);
        slen = fr_dhcpv6_encode(&work_dbuff, NULL, 0, 0, &vp->vp_group);
        if (slen <= 0) return slen;
 
        fr_dbuff_in(&len_m, (uint16_t)slen);            /* Write out the length value */
 
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "Done Relay-Message header");
 
        vp = fr_dcursor_next(cursor);
        fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Encode a DHCPv6 option and any sub-options.
 *
 * @param[out] dbuff            Where to write encoded DHCP attributes.
 * @param[in] cursor            with current VP set to the option to be encoded.
 *                              Will be advanced to the next option to encode.
 * @param[in] encode_ctx        containing parameters for the encoder.
 * @return
 *      - > 0 length of data written.
 *      - < 0 error.
 */
ssize_t fr_dhcpv6_encode_option(fr_dbuff_t *dbuff, fr_dcursor_t *cursor, void * encode_ctx)
{
        fr_pair_t               *vp;
        unsigned int            depth = 0;
        fr_da_stack_t           da_stack;
        fr_dbuff_t              work_dbuff = FR_DBUFF_MAX(dbuff, DHCPV6_OPT_HDR_LEN + UINT16_MAX);
        ssize_t                 slen;
 
        vp = fr_dcursor_current(cursor);
        if (!vp) return 0;
 
        FR_PROTO_TRACE("encoding option %s", vp->da->name);
 
        if (vp->da->flags.internal) {
                fr_strerror_printf("Attribute \"%s\" is not a DHCPv6 option", vp->da->name);
                fr_dcursor_next(cursor);
                return 0;
        }
 
        fr_proto_da_stack_build(&da_stack, vp->da);
 
        FR_PROTO_STACK_PRINT(&da_stack, depth);
 
        /*
         *      Deal with nested options
         */
        switch (da_stack.da[depth]->type) {
        case FR_TYPE_GROUP:
                /*
                 *      Relay-Message has a special format, it's an entire packet. :(
                 */
                if (da_stack.da[depth] == attr_relay_message) {
                        slen = encode_relay_message(&work_dbuff, &da_stack, depth, cursor, encode_ctx);
                        break;
                }
 
                slen = encode_rfc(&work_dbuff, &da_stack, depth, cursor, encode_ctx);
                break;
 
        default:
                slen = encode_child(&work_dbuff, &da_stack, depth, cursor, encode_ctx);
                break;
        }
        if (slen < 0) return slen;
 
        FR_PROTO_TRACE("Complete option is %zu byte(s)", fr_dbuff_used(&work_dbuff));
        FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), NULL);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
ssize_t fr_dhcpv6_encode_foreign(fr_dbuff_t *dbuff, fr_pair_list_t const *list)
{
        ssize_t         slen;
        fr_dcursor_t    cursor;
        fr_dbuff_t      work_dbuff = FR_DBUFF(dbuff);
 
        fr_assert(dict_dhcpv6 != NULL);
 
        fr_pair_dcursor_iter_init(&cursor, list, fr_dhcpv6_next_encodable, dict_dhcpv6);
 
        while (fr_dcursor_current(&cursor) != NULL) {
                slen = fr_dhcpv6_encode_option(&work_dbuff, &cursor, &(fr_dhcpv6_encode_ctx_t){ .root = fr_dict_root(dict_dhcpv6) });
                if (slen < 0) return slen;
        }
 
        FR_PROTO_TRACE("Foreign option is %zu byte(s)", fr_dbuff_used(&work_dbuff));
        FR_PROTO_HEX_DUMP(dbuff->p, fr_dbuff_used(&work_dbuff), NULL);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
 
static int encode_test_ctx(void **out, TALLOC_CTX *ctx, UNUSED fr_dict_t const *dict)
{
        fr_dhcpv6_encode_ctx_t  *test_ctx;
 
        test_ctx = talloc_zero(ctx, fr_dhcpv6_encode_ctx_t);
        if (!test_ctx) return -1;
 
        test_ctx->root = fr_dict_root(dict_dhcpv6);
 
        *out = test_ctx;
 
        return 0;
}
 
static ssize_t fr_dhcpv6_encode_proto(UNUSED TALLOC_CTX *ctx, fr_pair_list_t *vps, uint8_t *data, size_t data_len, UNUSED void *proto_ctx)
{
        ssize_t slen;
 
        slen = fr_dhcpv6_encode(&FR_DBUFF_TMP(data, data_len), NULL, 0, 0, vps);
 
#ifndef NDEBUG
        if (slen <= 0) return slen;
 
        if (fr_debug_lvl > 2) {
                fr_dhcpv6_print_hex(stdout, data, slen);
        }
#endif
 
        return slen;
}
 
/*
 *      Test points
 */
extern fr_test_point_pair_encode_t dhcpv6_tp_encode_pair;
fr_test_point_pair_encode_t dhcpv6_tp_encode_pair = {
        .test_ctx       = encode_test_ctx,
        .func           = fr_dhcpv6_encode_option,
        .next_encodable = fr_dhcpv6_next_encodable,
};
 
extern fr_test_point_proto_encode_t dhcpv6_tp_encode_proto;
fr_test_point_proto_encode_t dhcpv6_tp_encode_proto = {
        .test_ctx       = encode_test_ctx,
        .func           = fr_dhcpv6_encode_proto
};