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osmo-hlr/src/mslookup/mdns.c

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/* mslookup specific functions for encoding and decoding mslookup queries/results into mDNS packets, using the high
* level functions from mdns_msg.c and mdns_record.c to build the request/answer messages. */
/* 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 <osmocom/hlr/logging.h>
#include <osmocom/core/msgb.h>
#include <osmocom/mslookup/mslookup.h>
#include <osmocom/mslookup/mdns_msg.h>
#include <osmocom/mslookup/mdns_rfc.h>
#include <errno.h>
#include <inttypes.h>
static struct msgb *osmo_mdns_msgb_alloc(const char *label)
{
return msgb_alloc(1024, label);
}
/*! Combine the mslookup query service, ID and ID type into a domain string.
* \param[in] domain_suffix is appended to each domain in the queries to avoid colliding with the top-level domains
* administrated by IANA. Example: "mdns.osmocom.org"
* \returns allocated buffer with the resulting domain (i.e. "sip.voice.123.msisdn.mdns.osmocom.org") on success,
* NULL on failure.
*/
static char *domain_from_query(void *ctx, const struct osmo_mslookup_query *query, const char *domain_suffix)
{
const char *id;
/* Get id from query */
switch (query->id.type) {
case OSMO_MSLOOKUP_ID_IMSI:
id = query->id.imsi;
break;
case OSMO_MSLOOKUP_ID_MSISDN:
id = query->id.msisdn;
break;
default:
LOGP(DMSLOOKUP, LOGL_ERROR, "can't encode mslookup query id type %i", query->id.type);
return NULL;
}
return talloc_asprintf(ctx, "%s.%s.%s.%s", query->service, id, osmo_mslookup_id_type_name(query->id.type),
domain_suffix);
}
/*! Split up query service, ID and ID type from a domain string into a mslookup query.
* \param[in] domain with domain_suffix, e.g. "sip.voice.123.msisdn.mdns.osmocom.org"
* \param[in] domain_suffix is appended to each domain in the queries to avoid colliding with the top-level domains
* administrated by IANA. It is not part of the resulting struct osmo_mslookup_query, so we
* remove it in this function. Example: "mdns.osmocom.org"
*/
int query_from_domain(struct osmo_mslookup_query *query, const char *domain, const char *domain_suffix)
{
int domain_len = strlen(domain) - strlen(domain_suffix) - 1;
char domain_buf[OSMO_MDNS_RFC_MAX_NAME_LEN];
if (domain_len <= 0 || domain_len >= sizeof(domain_buf))
return -EINVAL;
if (domain[domain_len] != '.' || strcmp(domain + domain_len + 1, domain_suffix) != 0)
return -EINVAL;
memcpy(domain_buf, domain, domain_len);
domain_buf[domain_len] = '\0';
return osmo_mslookup_query_init_from_domain_str(query, domain_buf);
}
/*! Encode a mslookup query into a mDNS packet.
* \param[in] domain_suffix is appended to each domain in the queries to avoid colliding with the top-level domains
* administrated by IANA. Example: "mdns.osmocom.org"
* \returns msgb, or NULL on error.
*/
struct msgb *osmo_mdns_query_encode(void *ctx, uint16_t packet_id, const struct osmo_mslookup_query *query,
const char *domain_suffix)
{
struct osmo_mdns_msg_request req = {0};
struct msgb *msg = osmo_mdns_msgb_alloc(__func__);
req.id = packet_id;
req.type = OSMO_MDNS_RFC_RECORD_TYPE_ALL;
req.domain = domain_from_query(ctx, query, domain_suffix);
if (!req.domain)
goto error;
if (osmo_mdns_msg_request_encode(ctx, msg, &req))
goto error;
talloc_free(req.domain);
return msg;
error:
msgb_free(msg);
talloc_free(req.domain);
return NULL;
}
/*! Decode a mDNS request packet into a mslookup query.
* \param[out] packet_id the result must be sent with the same packet_id.
* \param[in] domain_suffix is appended to each domain in the queries to avoid colliding with the top-level domains
* administrated by IANA. Example: "mdns.osmocom.org"
* \returns allocated mslookup query on success, NULL on error.
*/
struct osmo_mslookup_query *osmo_mdns_query_decode(void *ctx, const uint8_t *data, size_t data_len,
uint16_t *packet_id, const char *domain_suffix)
{
struct osmo_mdns_msg_request *req = NULL;
struct osmo_mslookup_query *query = NULL;
req = osmo_mdns_msg_request_decode(ctx, data, data_len);
if (!req)
return NULL;
query = talloc_zero(ctx, struct osmo_mslookup_query);
OSMO_ASSERT(query);
if (query_from_domain(query, req->domain, domain_suffix) < 0)
goto error_free;
*packet_id = req->id;
talloc_free(req);
return query;
error_free:
talloc_free(req);
talloc_free(query);
return NULL;
}
/*! Parse sockaddr_str from mDNS record, so the mslookup result can be filled with it.
* \param[out] sockaddr_str resulting IPv4 or IPv6 sockaddr_str.
* \param[in] rec single record of the abstracted list of mDNS records
* \returns 0 on success, -EINVAL on error.
*/
static int sockaddr_str_from_mdns_record(struct osmo_sockaddr_str *sockaddr_str, struct osmo_mdns_record *rec)
{
switch (rec->type) {
case OSMO_MDNS_RFC_RECORD_TYPE_A:
if (rec->length != 4) {
LOGP(DMSLOOKUP, LOGL_ERROR, "unexpected length of A record\n");
return -EINVAL;
}
osmo_sockaddr_str_from_32(sockaddr_str, *(uint32_t *)rec->data, 0);
break;
case OSMO_MDNS_RFC_RECORD_TYPE_AAAA:
if (rec->length != 16) {
LOGP(DMSLOOKUP, LOGL_ERROR, "unexpected length of AAAA record\n");
return -EINVAL;
}
osmo_sockaddr_str_from_in6_addr(sockaddr_str, (struct in6_addr*)rec->data, 0);
break;
default:
LOGP(DMSLOOKUP, LOGL_ERROR, "unexpected record type\n");
return -EINVAL;
}
return 0;
}
/*! Encode a successful mslookup result, along with the original query and packet_id into one mDNS answer packet.
*
* The records in the packet are ordered as follows:
* 1) "age", ip_v4/v6, "port" (only IPv4 or IPv6 present) or
* 2) "age", ip_v4, "port", ip_v6, "port" (both IPv4 and v6 present).
* "age" and "port" are TXT records, ip_v4 is an A record, ip_v6 is an AAAA record.
*
* \param[in] packet_id as received in osmo_mdns_query_decode().
* \param[in] query the original query, so we can send the domain back in the answer (i.e. "sip.voice.1234.msisdn").
* \param[in] result holds the age, IPs and ports of the queried service.
* \param[in] domain_suffix is appended to each domain in the queries to avoid colliding with the top-level domains
* administrated by IANA. Example: "mdns.osmocom.org"
* \returns msg on success, NULL on error.
*/
struct msgb *osmo_mdns_result_encode(void *ctx, uint16_t packet_id, const struct osmo_mslookup_query *query,
const struct osmo_mslookup_result *result, const char *domain_suffix)
{
struct osmo_mdns_msg_answer ans = {};
struct osmo_mdns_record *rec_age = NULL;
struct osmo_mdns_record rec_ip_v4 = {0};
struct osmo_mdns_record rec_ip_v6 = {0};
struct osmo_mdns_record *rec_ip_v4_port = NULL;
struct osmo_mdns_record *rec_ip_v6_port = NULL;
struct in_addr rec_ip_v4_in;
struct in6_addr rec_ip_v6_in;
struct msgb *msg = osmo_mdns_msgb_alloc(__func__);
char buf[256];
ctx = talloc_named(ctx, 0, "osmo_mdns_result_encode");
/* Prepare answer (ans) */
ans.domain = domain_from_query(ctx, query, domain_suffix);
if (!ans.domain)
goto error;
ans.id = packet_id;
INIT_LLIST_HEAD(&ans.records);
/* Record for age */
rec_age = osmo_mdns_record_txt_keyval_encode(ctx, "age", "%"PRIu32, result->age);
OSMO_ASSERT(rec_age);
llist_add_tail(&rec_age->list, &ans.records);
/* Records for IPv4 */
if (osmo_sockaddr_str_is_set(&result->host_v4)) {
if (osmo_sockaddr_str_to_in_addr(&result->host_v4, &rec_ip_v4_in) < 0) {
LOGP(DMSLOOKUP, LOGL_ERROR, "failed to encode ipv4: %s\n",
osmo_mslookup_result_name_b(buf, sizeof(buf), query, result));
goto error;
}
rec_ip_v4.type = OSMO_MDNS_RFC_RECORD_TYPE_A;
rec_ip_v4.data = (uint8_t *)&rec_ip_v4_in;
rec_ip_v4.length = sizeof(rec_ip_v4_in);
llist_add_tail(&rec_ip_v4.list, &ans.records);
rec_ip_v4_port = osmo_mdns_record_txt_keyval_encode(ctx, "port", "%"PRIu16, result->host_v4.port);
OSMO_ASSERT(rec_ip_v4_port);
llist_add_tail(&rec_ip_v4_port->list, &ans.records);
}
/* Records for IPv6 */
if (osmo_sockaddr_str_is_set(&result->host_v6)) {
if (osmo_sockaddr_str_to_in6_addr(&result->host_v6, &rec_ip_v6_in) < 0) {
LOGP(DMSLOOKUP, LOGL_ERROR, "failed to encode ipv6: %s\n",
osmo_mslookup_result_name_b(buf, sizeof(buf), query, result));
goto error;
}
rec_ip_v6.type = OSMO_MDNS_RFC_RECORD_TYPE_AAAA;
rec_ip_v6.data = (uint8_t *)&rec_ip_v6_in;
rec_ip_v6.length = sizeof(rec_ip_v6_in);
llist_add_tail(&rec_ip_v6.list, &ans.records);
rec_ip_v6_port = osmo_mdns_record_txt_keyval_encode(ctx, "port", "%"PRIu16, result->host_v6.port);
OSMO_ASSERT(rec_ip_v6_port);
llist_add_tail(&rec_ip_v6_port->list, &ans.records);
}
if (osmo_mdns_msg_answer_encode(ctx, msg, &ans)) {
LOGP(DMSLOOKUP, LOGL_ERROR, "failed to encode mDNS answer: %s\n",
osmo_mslookup_result_name_b(buf, sizeof(buf), query, result));
goto error;
}
talloc_free(ctx);
return msg;
error:
msgb_free(msg);
talloc_free(ctx);
return NULL;
}
static int decode_uint32_t(const char *str, uint32_t *val)
{
long long int lld;
char *endptr = NULL;
*val = 0;
errno = 0;
lld = strtoll(str, &endptr, 10);
if (errno || !endptr || *endptr)
return -EINVAL;
if (lld < 0 || lld > UINT32_MAX)
return -EINVAL;
*val = lld;
return 0;
}
static int decode_port(const char *str, uint16_t *port)
{
uint32_t val;
if (decode_uint32_t(str, &val))
return -EINVAL;
if (val > 65535)
return -EINVAL;
*port = val;
return 0;
}
/*! Read expected mDNS records into mslookup result.
*
* The records in the packet must be ordered as follows:
* 1) "age", ip_v4/v6, "port" (only IPv4 or IPv6 present) or
* 2) "age", ip_v4, "port", ip_v6, "port" (both IPv4 and v6 present).
* "age" and "port" are TXT records, ip_v4 is an A record, ip_v6 is an AAAA record.
*
* \param[out] result holds the age, IPs and ports of the queried service.
* \param[in] ans abstracted mDNS answer with a list of resource records.
* \returns 0 on success, -EINVAL on error.
*/
int osmo_mdns_result_from_answer(struct osmo_mslookup_result *result, const struct osmo_mdns_msg_answer *ans)
{
struct osmo_mdns_record *rec;
char txt_key[64];
char txt_value[64];
bool found_age = false;
bool found_ip_v4 = false;
bool found_ip_v6 = false;
struct osmo_sockaddr_str *expect_port_for = NULL;
*result = (struct osmo_mslookup_result){};
result->rc = OSMO_MSLOOKUP_RC_NONE;
llist_for_each_entry(rec, &ans->records, list) {
switch (rec->type) {
case OSMO_MDNS_RFC_RECORD_TYPE_A:
if (expect_port_for) {
LOGP(DMSLOOKUP, LOGL_ERROR,
"'A' record found, but still expecting a 'port' value first\n");
return -EINVAL;
}
if (found_ip_v4) {
LOGP(DMSLOOKUP, LOGL_ERROR, "'A' record found twice in mDNS answer\n");
return -EINVAL;
}
found_ip_v4 = true;
expect_port_for = &result->host_v4;
if (sockaddr_str_from_mdns_record(expect_port_for, rec)) {
LOGP(DMSLOOKUP, LOGL_ERROR, "'A' record with invalid address data\n");
return -EINVAL;
}
break;
case OSMO_MDNS_RFC_RECORD_TYPE_AAAA:
if (expect_port_for) {
LOGP(DMSLOOKUP, LOGL_ERROR,
"'AAAA' record found, but still expecting a 'port' value first\n");
return -EINVAL;
}
if (found_ip_v6) {
LOGP(DMSLOOKUP, LOGL_ERROR, "'AAAA' record found twice in mDNS answer\n");
return -EINVAL;
}
found_ip_v6 = true;
expect_port_for = &result->host_v6;
if (sockaddr_str_from_mdns_record(expect_port_for, rec) != 0) {
LOGP(DMSLOOKUP, LOGL_ERROR, "'AAAA' record with invalid address data\n");
return -EINVAL;
}
break;
case OSMO_MDNS_RFC_RECORD_TYPE_TXT:
if (osmo_mdns_record_txt_keyval_decode(rec, txt_key, sizeof(txt_key),
txt_value, sizeof(txt_value)) != 0) {
LOGP(DMSLOOKUP, LOGL_ERROR, "failed to decode txt record\n");
return -EINVAL;
}
if (strcmp(txt_key, "age") == 0) {
if (found_age) {
LOGP(DMSLOOKUP, LOGL_ERROR, "duplicate 'TXT' record for 'age'\n");
return -EINVAL;
}
found_age = true;
if (decode_uint32_t(txt_value, &result->age)) {
LOGP(DMSLOOKUP, LOGL_ERROR,
"'TXT' record: invalid 'age' value ('age=%s')\n", txt_value);
return -EINVAL;
}
} else if (strcmp(txt_key, "port") == 0) {
if (!expect_port_for) {
LOGP(DMSLOOKUP, LOGL_ERROR,
"'TXT' record for 'port' without previous 'A' or 'AAAA' record\n");
return -EINVAL;
}
if (decode_port(txt_value, &expect_port_for->port)) {
LOGP(DMSLOOKUP, LOGL_ERROR,
"'TXT' record: invalid 'port' value ('port=%s')\n", txt_value);
return -EINVAL;
}
expect_port_for = NULL;
} else {
LOGP(DMSLOOKUP, LOGL_ERROR, "unexpected key '%s' in TXT record\n", txt_key);
return -EINVAL;
}
break;
default:
LOGP(DMSLOOKUP, LOGL_ERROR, "unexpected record type\n");
return -EINVAL;
}
}
/* Check if everything was found */
if (!found_age || !(found_ip_v4 || found_ip_v6) || expect_port_for) {
LOGP(DMSLOOKUP, LOGL_ERROR, "missing resource records in mDNS answer\n");
return -EINVAL;
}
result->rc = OSMO_MSLOOKUP_RC_RESULT;
return 0;
}
/*! Decode a mDNS answer packet into a mslookup result, query and packet_id.
* \param[out] packet_id same ID as sent in the request packet.
* \param[out] query the original query (service, ID, ID type).
* \param[out] result holds the age, IPs and ports of the queried service.
* \param[in] domain_suffix is appended to each domain in the queries to avoid colliding with the top-level domains
* administrated by IANA. Example: "mdns.osmocom.org"
* \returns 0 on success, -EINVAL on error.
*/
int osmo_mdns_result_decode(void *ctx, const uint8_t *data, size_t data_len, uint16_t *packet_id,
struct osmo_mslookup_query *query, struct osmo_mslookup_result *result,
const char *domain_suffix)
{
int rc = -EINVAL;
struct osmo_mdns_msg_answer *ans;
ans = osmo_mdns_msg_answer_decode(ctx, data, data_len);
if (!ans)
goto exit_free;
if (query_from_domain(query, ans->domain, domain_suffix) < 0)
goto exit_free;
if (osmo_mdns_result_from_answer(result, ans) < 0)
goto exit_free;
*packet_id = ans->id;
rc = 0;
exit_free:
talloc_free(ans);
return rc;
}
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