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: 529b9bec99702e96ad0e185a2d87a4d54714faf0 $
 *
 * @file protocols/dhcpv4/encode.c
 * @brief Functions to encode DHCP options.
 *
 * @copyright 2008,2017 The FreeRADIUS server project
 * @copyright 2008 Alan DeKok (aland@deployingradius.com)
 * @copyright 2015,2017 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 */
#include <freeradius-devel/io/test_point.h>
#include <freeradius-devel/util/dbuff.h>
#include <freeradius-devel/util/proto.h>
#include <freeradius-devel/util/struct.h>
#include <freeradius-devel/util/dns.h>
#include <freeradius-devel/util/encode.h>
 
#include "dhcpv4.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_child(fr_dbuff_t *dbuff,
                                  fr_da_stack_t *da_stack, unsigned int depth,
                                  fr_dcursor_t *cursor, void *encode_ctx);
 
/** Write DHCP option value into buffer
 *
 * Does not include DHCP option length or number.
 *
 * @param[out] dbuff            buffer to write the option to.
 * @param[in] da_stack          Describing nesting of options.
 * @param[in] depth             in da_stack.
 * @param[in,out] cursor        Current attribute we're encoding.
 * @param[in] encode_ctx        Containing DHCPv4 dictionary.
 * @return
 *      - The length of data written, may return 0 for bools
 *      < 0 if there's not enough space or option type is unsupported
 */
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)
{
        fr_pair_t       *vp = fr_dcursor_current(cursor);
        fr_dbuff_t      work_dbuff = FR_DBUFF(dbuff);
        fr_dict_attr_t const    *da = da_stack->da[depth];
        ssize_t         slen;
 
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
        FR_PROTO_TRACE("%zu byte(s) available for value", fr_dbuff_remaining(dbuff));
 
        /*
         *      Structures are special.
         */
        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;
 
                /*
                 *      Rebuild the da_stack for the next option.
                 */
                vp = fr_dcursor_current(cursor);
                fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
                return fr_dbuff_set(dbuff, &work_dbuff);
        }
 
        switch (da_stack->da[depth]->type) {
        case FR_TYPE_ATTR:
                FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, (uint8_t) vp->vp_attr->attr);
                break;
 
        case FR_TYPE_IPV6_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, sizeof(vp->vp_ipv6addr));
                break;
 
        case FR_TYPE_IPV6_ADDR:
                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, (uint8_t const *)&vp->vp_ipv6addr, sizeof(vp->vp_ipv6addr));
                break;
 
                /*
                 *      "option exists" == true.
                 *      "option does not exist" == false
                 *
                 *      fr_dhcpv4_next_encodable() takes care of skipping bools which are false.
                 *
                 *      Rapid-Commit does this.  Options 19/20 require encoding as one byte of 0/1.
                 */
        case FR_TYPE_BOOL:
                if (fr_dhcpv4_flag_exists(vp->da)) {
                        break;
                }
                FR_DBUFF_IN_RETURN(&work_dbuff, (uint8_t) (vp->vp_bool == true));
                break;
 
        case FR_TYPE_IPV4_PREFIX:
                if (fr_dhcpv4_flag_prefix_split(vp->da)) {
                        uint32_t mask;
 
                        mask = ~((~(uint32_t) 0) >> vp->vp_ip.prefix);
 
                        FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff,
                                                  (uint8_t const *)&vp->vp_ipv4addr,
                                                  sizeof(vp->vp_ipv4addr));
                        FR_DBUFF_IN_RETURN(&work_dbuff, mask);
                        break;
                }
 
                if (fr_dhcpv4_flag_prefix_bits(vp->da)) {
                        size_t num_bytes = (vp->vp_ip.prefix + 0x07) >> 3;
 
                        FR_DBUFF_IN_RETURN(&work_dbuff, (uint8_t) vp->vp_ip.prefix);
 
                        if (num_bytes) {
                                FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff,
                                                          (uint8_t const *)&vp->vp_ipv4addr,
                                                          num_bytes);
                        }
 
                        break;
                }
 
                goto from_network;
 
        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_dhcpv4_flag_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;
                        break;
                }
                FALL_THROUGH;
 
        default:
        from_network:
                slen = fr_value_box_to_network(&work_dbuff, &vp->data);
                if (slen < 0) return slen;
                break;
        }
 
        vp = fr_dcursor_next(cursor);   /* We encoded a leaf, advance the cursor */
        fr_proto_da_stack_build(da_stack, vp ? vp->da : NULL);
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
        FR_PROTO_HEX_DUMP(dbuff->p, fr_dbuff_used(&work_dbuff), "Value");
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
 
/** Extend an encoded option in-place.
 *
 * @param[in] dbuff     buffer containing the option
 * @param[in] hdr       marker (with dbuff as parent) set to where the option starts
 * @param[in] len        length of the data being written
 * @return
 *      - <0 if we can't extend the option
 *      - >0  if we can, with hdr set to where the next option should start
 * @note        The option starts with a two-byte (type, length) header, where
 *              the length does *not* include the two bytes for the header.
 *              The starting length may be non-zero, hence its counting towards
 *              the header_byte calculation and its inclusion in sublen calculation.
 *              (All those following start out empty, hence the initialization
 *              of their lengths to zero.)
 */
static ssize_t extend_option(fr_dbuff_t *dbuff, fr_dbuff_marker_t *hdr, size_t len)
{
        size_t                  header_bytes;
        uint8_t                 type = 0, option_len = 0;
        fr_dbuff_marker_t       dst, tmp;
 
        /*
         *      This can't follow the convention of operating on
         *      a chlld dbuff because it must work on and amidst
         *      already-written data.
         */
 
        fr_dbuff_marker(&dst, dbuff);
        fr_dbuff_marker(&tmp, dbuff);
 
        fr_dbuff_set(&tmp, hdr);
 
        /*
         *      Read the current header.
         */
        if (fr_dbuff_out(&type, &tmp) < 0 || fr_dbuff_out(&option_len, &tmp) < 0) {
        error:
                fr_dbuff_marker_release(&dst);
                fr_dbuff_marker_release(&tmp);
                return -1;
        }
 
        len += option_len;
 
        /*
         *      How many bytes we will need to add for all headers.
         */
        header_bytes = (option_len / 255) * 2;
 
        /*
         *      No room for the new headers and data, we're done.
         */
        if (fr_dbuff_extend_lowat(NULL, dbuff, header_bytes) < header_bytes) goto error;
 
        /*
         *      Moving the same data repeatedly in a loop is simpler
         *      and less error-prone than anything smarter.
         */
        while (true) {
                uint8_t sublen;
 
                sublen = (len > 255) ? 255 : len;
 
                /*
                 *      Write the new header, including the (possibly partial) length.
                 */
                fr_dbuff_set(&tmp, fr_dbuff_current(hdr));
                FR_DBUFF_IN_BYTES_RETURN(&tmp, type, sublen);
 
                /*
                 *      The data is already where it's supposed to be, and the length is in the header, and
                 *      the length is small.  We're done.
                 */
                len -= sublen;
                if (!len) {
                        fr_dbuff_set(dbuff, fr_dbuff_current(hdr) + sublen + 2);
                        len = sublen;
                        break;
                }
 
                /*
                 *      Take the current header, skip it, and then skip the data we just encoded.  That is the
                 *      location of the "next" header.
                 */
                fr_dbuff_set(&tmp, fr_dbuff_current(hdr) + 2 + 255);
                fr_dbuff_set(hdr, &tmp);
 
                /*
                 *      The data is currently overlapping with the next header.  We have to move it two bytes forward to
                 *      make room for the header.
                 */
                fr_dbuff_set(&dst, fr_dbuff_current(&tmp) + 2);
                fr_dbuff_move(&dst, &tmp, len);
        }
 
        fr_dbuff_marker_release(&dst);
        fr_dbuff_marker_release(&tmp);
        return len;
}
 
#define DHCPV4_OPT_HDR_LEN (2)
 
/** Write out an RFC option header and option data
 *
 * @note May coalesce options with fixed width values
 *
 * @param[out] dbuff            buffer to write the TLV to.
 * @param[in] da_stack          Describing nesting of options.
 * @param[in] depth             in the da_stack.
 * @param[in,out] cursor        Current attribute we're encoding.
 * @param[in] encode_ctx        Containing DHCPv4 dictionary.
 * @return
 *      - >0 length of data encoded.
 *      - 0 if we ran out of space.
 *      - < 0 on error.
 */
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)
{
        ssize_t                 len;
        fr_dbuff_marker_t       hdr;
        fr_dict_attr_t const    *da = da_stack->da[depth];
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        /*
         *      Write out the option number and length (which, unlike RADIUS,
         *      is just the length of the value and hence starts out as zero).
         */
        fr_dbuff_marker(&hdr, &work_dbuff);
        FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, (uint8_t)da->attr, (uint8_t) 0);
 
        /*
         *      Write out the option's value
         */
        if (da->flags.array) {
                len = fr_pair_array_to_network(&work_dbuff, da_stack, depth, cursor, encode_ctx, encode_value);
                if (len < 0) return -1;
 
        } else if (da->parent && (da->parent->type != FR_TYPE_VENDOR)) {
                fr_pair_t *vp;
 
                do {
                        len = encode_value(&work_dbuff, da_stack, depth, cursor, encode_ctx);
                        if (len < 0) return len; /* @todo return the correct offset, but whatever */
 
                        vp = fr_dcursor_current(cursor);
                } while (vp && (vp->da == da));
 
        } else {
                /*
                 *      For VSAs, each vendor value is prefixed by an 8-bit length, so we don't loop over the
                 *      input pairs.
                 */
                len = encode_value(&work_dbuff, da_stack, depth, cursor, encode_ctx);
                if (len < 0) return len; /* @todo return the correct offset, but whatever */
        }
 
        len = fr_dbuff_used(&work_dbuff) - 2;
 
        if (len <= UINT8_MAX) {
                fr_dbuff_advance(&hdr, 1);
                FR_DBUFF_IN_RETURN(&hdr, (uint8_t) len);
 
        } else if (extend_option(&work_dbuff, &hdr, len) < 0) {
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        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_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_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)
{
        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);
 
                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);
}
 
 
 
/** Write out a TLV header (and any sub TLVs or values)
 *
 * @param[out] dbuff            buffer to write the TLV to.
 * @param[in] da_stack          Describing nesting of options.
 * @param[in] depth             in the da_stack.
 * @param[in,out] cursor        Current attribute we're encoding.
 * @param[in] encode_ctx        Containing DHCPv4 dictionary.
 * @return
 *      - >0 length of data encoded.
 *      - 0 if we ran out of space.
 *      - < 0 on error.
 */
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)
{
        ssize_t                 len, option_len;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_marker_t       hdr, dst, tmp;
        fr_pair_t const         *vp = fr_dcursor_current(cursor);
        fr_dict_attr_t const    *da = da_stack->da[depth];
        uint8_t                 option_number;
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        /*
         *      Where the TLV header starts.
         */
        fr_dbuff_marker(&hdr, &work_dbuff);
 
        /*
         *      These are set before use; their initial value doesn't matter.
         */
        fr_dbuff_marker(&dst, &work_dbuff);
        fr_dbuff_marker(&tmp, &work_dbuff);
 
        /*
         *      Write out the option number and length (which, unlike RADIUS,
         *      is just the length of the value and hence starts out as zero).
         */
        option_number = (uint8_t)da->attr;
        option_len = 0;
        FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, option_number, option_len);
 
        /*
         *      Encode any sub TLVs or values
         */
        while (fr_dbuff_extend_lowat(NULL, &work_dbuff, 3) >= 3) {
                len = encode_child(&work_dbuff, da_stack, depth + 1, cursor, encode_ctx);
                if (len < 0) return len;
                if (len == 0) break;            /* Insufficient space */
 
                /*
                 *      If the newly added data fits within the current option, then
                 *      update the header, and go to the next option.
                 */
                if ((option_len + len) <= 255) {
                        option_len += len;
 
                        fr_dbuff_set(&tmp, fr_dbuff_current(&hdr) + 1);
                        FR_DBUFF_IN_BYTES_RETURN(&tmp, (uint8_t) option_len);
 
                } else if ((len = extend_option(&work_dbuff, &hdr, len)) < 0) {
                        return PAIR_ENCODE_FATAL_ERROR;
 
                } else {
                        option_len = len;
                }
 
                FR_PROTO_STACK_PRINT(da_stack, depth);
                FR_PROTO_HEX_DUMP(fr_dbuff_start(&work_dbuff), fr_dbuff_used(&work_dbuff), "TLV header and sub TLVs");
 
                /*
                 *      If nothing updated the attribute, stop
                 */
                if (!fr_dcursor_current(cursor) || (vp == fr_dcursor_current(cursor))) break;
 
                /*
                 *      We can encode multiple sub TLVs, if after
                 *      rebuilding the TLV Stack, the attribute
                 *      at this depth is the same.
                 */
                if ((da != da_stack->da[depth]) || (da_stack->depth < da->depth)) break;
                vp = fr_dcursor_current(cursor);
        }
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
static ssize_t encode_vsio_data(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_MAX(dbuff, 255 - 4 - 1 - 2);
        fr_dbuff_marker_t       hdr;
        fr_dict_attr_t const    *da;
        fr_dict_attr_t const    *dv = da_stack->da[depth - 1];
        ssize_t                 len;
        fr_pair_t               *vp;
 
        FR_PROTO_STACK_PRINT(da_stack, depth);
 
        if (dv->type != FR_TYPE_VENDOR) {
                fr_strerror_printf("%s: Expected type \"vendor\" got \"%s\"", __FUNCTION__,
                                   fr_type_to_str(dv->type));
                return PAIR_ENCODE_FATAL_ERROR;
        }
 
        /*
         *      Check if we have enough the enterprise-number,
         *      plus the data length, plus at least one option header.
         */
        FR_DBUFF_REMAINING_RETURN(&work_dbuff, sizeof(uint32_t) + 3);
 
        fr_dbuff_marker(&hdr, &work_dbuff);
 
        /*
         *      Copy in the 32bit PEN (Private Enterprise Number)
         *
         *      And leave room for data-len1
         */
        FR_DBUFF_IN_RETURN(&work_dbuff, dv->attr);
        FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, (uint8_t) 0x00);
 
        /*
         *      https://tools.ietf.org/html/rfc3925#section-4
         *
         *                         1 1 1 1 1 1
         *     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
         *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *    |  option-code  |  option-len   |
         *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *    |      enterprise-number1       |
         *    |                               |
         *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *    |   data-len1   |               |
         *    +-+-+-+-+-+-+-+-+ option-data1  |
         *    /                               /
         *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         */
        da = da_stack->da[depth];
 
        /*
         *      RFC 3925 Section 4 says:
         *
         *      Multiple instances of this option may be present and MUST be concatenated in accordance with
         *      RFC 3396.
         *
         *      @todo - we don't currently allow encoding more data as per extend_option() or encode_tlv().
         *      We probably want to do that.  We probably also want to update the decoder so that it
         *      concatenates options before decoding, too.
         */
        while (true) {
                len = encode_child(&work_dbuff, da_stack, depth, cursor, encode_ctx);
                if (len == 0) break; /* insufficient space */
                if (len < 0) return len;
 
                vp = fr_dcursor_current(cursor);
                if (!vp) break;
 
                /*
                 *      Encode all attributes which match this vendor.
                 */
                if (vp->da->parent != da->parent) break;
        }
 
        /*
         *      Write out "data-len1" for this vendor
         */
        fr_dbuff_advance(&hdr, 4);
        FR_DBUFF_IN_RETURN(&hdr, (uint8_t)(fr_dbuff_used(&work_dbuff) - 4 - 1));
 
#ifndef NDEBUG
        FR_PROTO_HEX_DUMP(dbuff->p, fr_dbuff_used(&work_dbuff), "Done VSIO Data");
#endif
 
        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)
{
        fr_dict_attr_t const    *da = da_stack->da[depth];
        fr_pair_t               *vp;
        fr_dcursor_t            vendor_cursor;
        fr_dbuff_t              work_dbuff;
        fr_dbuff_marker_t       hdr;
 
        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;
        }
 
        work_dbuff = FR_DBUFF(dbuff);
        fr_dbuff_marker(&hdr, &work_dbuff);
 
        /*
         *      Copy in the option code
         *      And leave room for data-len1
         */
        FR_DBUFF_IN_BYTES_RETURN(&work_dbuff, (uint8_t) da->attr, 0x00);
 
        /*
         *      We are at the VSA.  The next entry in the stack is the vendor.  The entry after that is the vendor data.
         */
        if (da_stack->da[depth + 1]) {
                ssize_t len;
                fr_dcursor_t vsa_cursor;
 
                if (da_stack->da[depth + 2]) {
                        len = encode_vsio_data(&work_dbuff, da_stack, depth + 2, cursor, encode_ctx);
                        if (len <= 0) return len;
                        goto done;
                }
 
                vp = fr_dcursor_current(cursor);
                fr_assert(vp->vp_type == FR_TYPE_VENDOR);
 
                /*
                 *      Copied from below.
                 */
                fr_pair_dcursor_init(&vsa_cursor, &vp->vp_group);
                work_dbuff = FR_DBUFF(dbuff);
 
                while ((vp = fr_dcursor_current(&vsa_cursor)) != NULL) {
                        fr_proto_da_stack_build(da_stack, vp->da);
                        len = encode_vsio_data(&work_dbuff, da_stack, depth + 2, &vsa_cursor, encode_ctx);
                        if (len <= 0) return len;
                }
                goto done;
        }
 
        vp = fr_dcursor_current(cursor);
        fr_assert(vp->da == da);
 
        fr_pair_dcursor_init(&vendor_cursor, &vp->vp_group);
 
        /*
         *      Loop over all vendors, and inside of that, loop over all VSA attributes.
         */
        while ((vp = fr_dcursor_current(&vendor_cursor)) != NULL) {
                ssize_t len;
                fr_dcursor_t vsa_cursor;
 
                if (vp->vp_type != FR_TYPE_VENDOR) continue;
 
                fr_pair_dcursor_init(&vsa_cursor, &vp->vp_group);
 
                while ((vp = fr_dcursor_current(&vsa_cursor)) != NULL) {
                        /*
                         *      RFC 3925 Section 4 says:
                         *
                         *      "An Enterprise Number SHOULD only occur once
                         *      among all instances of this option.  Behavior
                         *      is undefined if an Enterprise Number occurs
                         *      multiple times."
                         *
                         *      The function encode_vsio_data() builds
                         *      one header, and then loops over all
                         *      children of the vsa_cursor.
                         */
                        fr_proto_da_stack_build(da_stack, vp->da);
                        len = encode_vsio_data(&work_dbuff, da_stack, depth + 2, &vsa_cursor, encode_ctx);
                        if (len <= 0) return len;
                }
 
                (void) fr_dcursor_next(&vendor_cursor);
        }
 
        /*
         *      Write out length for whole option
         */
done:
        fr_dbuff_advance(&hdr, 1);
        FR_DBUFF_IN_RETURN(&hdr, (uint8_t)(fr_dbuff_used(&work_dbuff) - DHCPV4_OPT_HDR_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 a DHCP 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 DHCPv4 dictionary.
 * @return
 *      - > 0 length of data written.
 *      - < 0 error.
 *      - 0 not valid option for DHCP (skipping).
 */
ssize_t fr_dhcpv4_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;
        ssize_t                 len;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
 
        vp = fr_dcursor_current(cursor);
        if (!vp) return -1;
 
        if (vp->da == attr_dhcp_message_type) goto next; /* already done */
        if (vp->da->attr > 255) {
                fr_strerror_printf("Attribute \"%s\" is not a DHCP option", vp->da->name);
        next:
                (void)fr_dcursor_next(cursor);
                return 0;
        }
 
        fr_proto_da_stack_build(&da_stack, vp->da);
 
        FR_PROTO_STACK_PRINT(&da_stack, depth);
 
        /*
         *      We only have two types of options in DHCPv4
         */
        switch (da_stack.da[depth]->type) {
        case FR_TYPE_VSA:
                len = encode_vsio(&work_dbuff, &da_stack, depth, cursor, encode_ctx);
                break;
 
        case FR_TYPE_TLV:
                len = encode_tlv(&work_dbuff, &da_stack, depth, cursor, encode_ctx);
                break;
 
        default:
                len = encode_rfc(&work_dbuff, &da_stack, depth, cursor, encode_ctx);
                break;
        }
 
        if (len <= 0) return len;
 
        FR_PROTO_TRACE("Complete 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);
}
 
ssize_t fr_dhcpv4_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_dhcpv4 != NULL);
 
        fr_pair_dcursor_iter_init(&cursor, list, fr_dhcpv4_next_encodable, dict_dhcpv4);
 
        /*
         *      Loop over all DHCPv4 options.
         *
         *      Unlike fr_dhcpv4_encode_dbuff(), we don't sort the options.  If that causes problems, we will
         *      deal with it later.
         */
        while (fr_dcursor_current(&cursor) != NULL) {
                slen = fr_dhcpv4_encode_option(&work_dbuff, &cursor, &(fr_dhcpv4_ctx_t){ .root = fr_dict_root(dict_dhcpv4) });
                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 ssize_t fr_dhcpv4_encode_proto(UNUSED TALLOC_CTX *ctx, fr_pair_list_t *vps, uint8_t *data, size_t data_len, UNUSED void *proto_ctx)
{
        return fr_dhcpv4_encode_dbuff(&FR_DBUFF_TMP(data, data_len), NULL, 0, 0, vps);
}
 
static int encode_test_ctx(void **out, TALLOC_CTX *ctx, UNUSED fr_dict_t const *dict)
{
        fr_dhcpv4_ctx_t *test_ctx;
 
        test_ctx = talloc_zero(ctx, fr_dhcpv4_ctx_t);
        if (!test_ctx) return -1;
        test_ctx->root = fr_dict_root(dict_dhcpv4);
 
        *out = test_ctx;
 
        return 0;
}
 
/*
 *      Test points
 */
extern fr_test_point_pair_encode_t dhcpv4_tp_encode_pair;
fr_test_point_pair_encode_t dhcpv4_tp_encode_pair = {
        .test_ctx       = encode_test_ctx,
        .func           = fr_dhcpv4_encode_option,
        .next_encodable = fr_dhcpv4_next_encodable,
};
 
 
 
extern fr_test_point_proto_encode_t dhcpv4_tp_encode_proto;
fr_test_point_proto_encode_t dhcpv4_tp_encode_proto = {
        .test_ctx       = encode_test_ctx,
        .func           = fr_dhcpv4_encode_proto
};