/usr/include/libknot/packet/compr.h is in libknot-dev 2.6.5-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 | /* Copyright (C) 2013 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*!
* \file
*
* \brief Name compression API.
*
* \addtogroup libknot
* @{
*/
#pragma once
#include "libknot/dname.h"
#include "libknot/rrset.h"
#include "libknot/packet/wire.h"
/*! \brief Compression hint type. */
enum knot_compr_hint {
KNOT_COMPR_HINT_NONE = 0, /* No hint. */
KNOT_COMPR_HINT_NOCOMP = 1, /* Don't compress. */
KNOT_COMPR_HINT_QNAME = KNOT_WIRE_HEADER_SIZE /* Name is QNAME. */
};
/*! \brief Compression hint array offsets. */
enum knot_compr_offset {
KNOT_COMPR_HINT_OWNER = 0, /* First element in the array is RR owner. */
KNOT_COMPR_HINT_RDATA = 1, /* First name in RDATA is at offset 1. */
KNOT_COMPR_HINT_COUNT = 16 /* Maximum number of stored hints per-RR. */
};
/*
* \note A little bit about how compression hints work.
*
* We're storing a RRSet say 'abcd. CNAME [0]net. [1]com.' (owner=abcd. 2 RRs).
* The owner 'abcd.' is same for both RRs, we put it at the offset 0 in rrinfo.compress_ptr
* The names 'net.' and 'com.' are in the RDATA, therefore go to offsets 1 and 2.
* Now this is useful when solving additionals for example, because we can scan
* rrinfo for this RRSet and we know that 'net.' name is at the hint 1 and that leads
* to packet position N. With that, we just put the pointer in without any calculation.
* This is also useful for positive answers, where we know the RRSet owner is always QNAME.
* All in all, we just remember the positions of written domain names.
*/
/*! \brief Additional information about RRSet position and compression hints. */
typedef struct {
uint16_t pos; /* RRSet position in the packet. */
uint16_t flags; /* RRSet flags. */
uint16_t compress_ptr[KNOT_COMPR_HINT_COUNT]; /* Array of compr. ptr hints. */
} knot_rrinfo_t;
/*!
* \brief Name compression context.
*/
typedef struct knot_compr {
uint8_t *wire; /* Packet wireformat. */
knot_rrinfo_t *rrinfo; /* Hints for current RRSet. */
struct {
uint16_t pos; /* Position of current suffix. */
uint8_t labels; /* Label count of the suffix. */
} suffix;
} knot_compr_t;
/*!
* \brief Write compressed domain name to the destination wire.
*
* \param dname Name to be written.
* \param dst Destination wire.
* \param max Maximum number of bytes available.
* \param compr Compression context (NULL for no compression)
* \return Number of written bytes or an error.
*/
int knot_compr_put_dname(const knot_dname_t *dname, uint8_t *dst, uint16_t max,
knot_compr_t *compr);
/*! \brief Retrieve compression hint from given offset.
* \todo More detailed documentation.
*/
static inline uint16_t knot_pkt_compr_hint(const knot_rrinfo_t *info, uint16_t hint_id)
{
if (hint_id < KNOT_COMPR_HINT_COUNT) {
return info->compress_ptr[hint_id];
} else {
return KNOT_COMPR_HINT_NONE;
}
}
/*! \brief Store compression hint for given offset.
* \todo More detailed documentation.
*/
static inline void knot_pkt_compr_hint_set(knot_rrinfo_t *info, uint16_t hint_id,
uint16_t val, uint16_t len)
{
if ((hint_id < KNOT_COMPR_HINT_COUNT) && (val + len < KNOT_WIRE_PTR_MAX)) {
info->compress_ptr[hint_id] = val;
}
}
/*! @} */
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