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/* Low level mDNS encoding and decoding functions of the qname IE, header/question sections and resource records,
* as described in these RFCs:
* - RFC 1035 (Domain names - implementation and specification)
* - RFC 3596 (DNS Extensions to Support IP Version 6) */
/* Copyright 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
*
* All Rights Reserved
*
* 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 2 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/>.
*/
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <osmocom/core/msgb.h>
#include <osmocom/core/bitvec.h>
#include <osmocom/core/logging.h>
#include <osmocom/gsm/apn.h>
#include <osmocom/mslookup/mdns_rfc.h>
/*
* Encode/decode message sections
*/
/*! Encode header section (RFC 1035 4.1.1).
* \param[in] msgb mesage buffer to which the encoded data will be appended.
*/
void osmo_mdns_rfc_header_encode(struct msgb *msg, const struct osmo_mdns_rfc_header *hdr)
{
struct osmo_mdns_rfc_header *buf = (struct osmo_mdns_rfc_header *) msgb_put(msg, sizeof(*hdr));
memcpy(buf, hdr, sizeof(*hdr));
osmo_store16be(buf->id, &buf->id);
osmo_store16be(buf->qdcount, &buf->qdcount);
osmo_store16be(buf->ancount, &buf->ancount);
osmo_store16be(buf->nscount, &buf->nscount);
osmo_store16be(buf->arcount, &buf->arcount);
}
/*! Decode header section (RFC 1035 4.1.1). */
int osmo_mdns_rfc_header_decode(const uint8_t *data, size_t data_len, struct osmo_mdns_rfc_header *hdr)
{
if (data_len != sizeof(*hdr))
return -EINVAL;
memcpy(hdr, data, data_len);
hdr->id = osmo_load16be(&hdr->id);
hdr->qdcount = osmo_load16be(&hdr->qdcount);
hdr->ancount = osmo_load16be(&hdr->ancount);
hdr->nscount = osmo_load16be(&hdr->nscount);
hdr->arcount = osmo_load16be(&hdr->arcount);
return 0;
}
/*! Encode question section (RFC 1035 4.1.2).
* \param[in] msgb mesage buffer to which the encoded data will be appended.
*/
int osmo_mdns_rfc_question_encode(struct msgb *msg, const struct osmo_mdns_rfc_question *qst)
{
uint8_t *buf;
size_t buf_len;
/* qname */
buf_len = strlen(qst->domain) + 1;
buf = msgb_put(msg, buf_len);
if (osmo_apn_from_str(buf, buf_len, qst->domain) < 0)
return -EINVAL;
msgb_put_u8(msg, 0x00);
/* qtype and qclass */
msgb_put_u16(msg, qst->qtype);
msgb_put_u16(msg, qst->qclass);
return 0;
}
/*! Decode question section (RFC 1035 4.1.2). */
struct osmo_mdns_rfc_question *osmo_mdns_rfc_question_decode(void *ctx, const uint8_t *data, size_t data_len)
{
struct osmo_mdns_rfc_question *ret;
size_t qname_len = data_len - 4;
if (data_len < 6)
return NULL;
ret = talloc_zero(ctx, struct osmo_mdns_rfc_question);
if (!ret)
return NULL;
/* qname */
ret->domain = talloc_size(ret, qname_len - 1);
if (!ret->domain)
goto error;
if (!osmo_apn_to_str(ret->domain, data, qname_len - 1))
goto error;
/* qtype and qclass */
ret->qtype = osmo_load16be(data + qname_len);
ret->qclass = osmo_load16be(data + qname_len + 2);
return ret;
error:
talloc_free(ret);
return NULL;
}
/*
* Encode/decode resource records
*/
/*! Encode one resource record (RFC 1035 4.1.3).
* \param[in] msgb mesage buffer to which the encoded data will be appended.
*/
int osmo_mdns_rfc_record_encode(struct msgb *msg, const struct osmo_mdns_rfc_record *rec)
{
uint8_t *buf;
size_t buf_len;
/* name */
buf_len = strlen(rec->domain) + 1;
buf = msgb_put(msg, buf_len);
if (osmo_apn_from_str(buf, buf_len, rec->domain) < 0)
return -EINVAL;
msgb_put_u8(msg, 0x00);
/* type, class, ttl, rdlength */
msgb_put_u16(msg, rec->type);
msgb_put_u16(msg, rec->class);
msgb_put_u32(msg, rec->ttl);
msgb_put_u16(msg, rec->rdlength);
/* rdata */
buf = msgb_put(msg, rec->rdlength);
memcpy(buf, rec->rdata, rec->rdlength);
return 0;
}
/*! Decode one resource record (RFC 1035 4.1.3). */
struct osmo_mdns_rfc_record *osmo_mdns_rfc_record_decode(void *ctx, const uint8_t *data, size_t data_len,
size_t *record_len)
{
struct osmo_mdns_rfc_record *ret;
size_t name_len;
/* name length: represented as a series of labels, and terminated by a
* label with zero length (RFC 1035 3.3). A label with zero length is a
* NUL byte. */
name_len = strnlen((const char *)data, data_len - 10) + 1;
if (data[name_len])
return NULL;
/* allocate ret + ret->domain */
ret = talloc_zero(ctx, struct osmo_mdns_rfc_record);
if (!ret)
return NULL;
ret->domain = talloc_size(ctx, name_len - 1);
if (!ret->domain)
goto error;
/* name */
if (!osmo_apn_to_str(ret->domain, data, name_len - 1))
goto error;
/* type, class, ttl, rdlength */
ret->type = osmo_load16be(data + name_len);
ret->class = osmo_load16be(data + name_len + 2);
ret->ttl = osmo_load32be(data + name_len + 4);
ret->rdlength = osmo_load16be(data + name_len + 8);
if (name_len + 10 + ret->rdlength > data_len)
goto error;
/* rdata */
ret->rdata = talloc_memdup(ret, data + name_len + 10, ret->rdlength);
if (!ret->rdata)
goto error;
*record_len = name_len + 10 + ret->rdlength;
return ret;
error:
talloc_free(ret);
return NULL;
}
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