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Merge pull request #16669 from miri64/sock_dns/enh/factor-out-msg-parsing

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sock_dns: factor out message parsing and composition
This commit is contained in:
Martine Lenders 2021-08-11 12:43:26 +02:00 committed by GitHub
commit 6da2f0fab3
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GPG Key ID: 4AEE18F83AFDEB23
10 changed files with 269 additions and 110 deletions
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1
makefiles/pseudomodules.inc.mk
View File

@ -27,6 +27,7 @@ PSEUDOMODULES += dhcpv6_%
PSEUDOMODULES += dhcpv6_client_dns
PSEUDOMODULES += dhcpv6_client_ia_pd
PSEUDOMODULES += dhcpv6_client_mud_url
PSEUDOMODULES += dns_msg
PSEUDOMODULES += ecc_%
PSEUDOMODULES += event_%
PSEUDOMODULES += event_timeout_ztimer

5
sys/Makefile
View File

@ -38,6 +38,9 @@ endif
ifneq (,$(filter dhcpv6,$(USEMODULE)))
DIRS += net/application_layer/dhcpv6
endif
ifneq (,$(filter dns,$(USEMODULE)))
DIRS += net/application_layer/dns
endif
ifneq (,$(filter dsm,$(USEMODULE)))
DIRS += net/dsm
endif
@ -132,7 +135,7 @@ ifneq (,$(filter sock_async_event,$(USEMODULE)))
DIRS += net/sock/async/event
endif
ifneq (,$(filter sock_dns,$(USEMODULE)))
DIRS += net/application_layer/dns
DIRS += net/application_layer/sock_dns
endif
ifneq (,$(filter sock_util,$(USEMODULE)))
DIRS += net/sock

5
sys/Makefile.dep
View File

@ -110,6 +110,10 @@ ifneq (,$(filter dhcpv6_client,$(USEMODULE)))
endif
endif
ifneq (,$(filter dns_%,$(USEMODULE)))
USEMODULE += dns
endif
ifneq (,$(filter fuzzing,$(USEMODULE)))
USEMODULE += netdev_test
USEMODULE += gnrc_netif
@ -474,6 +478,7 @@ ifneq (,$(filter sock_async,$(USEMODULE)))
endif
ifneq (,$(filter sock_dns,$(USEMODULE)))
USEMODULE += dns_msg
USEMODULE += sock_udp
USEMODULE += sock_util
USEMODULE += posix_headers

9
sys/include/net/dns.h
View File

@ -24,6 +24,15 @@
extern "C" {
#endif
/**
* @name DNS defines
* @{
*/
#define DNS_TYPE_A (1)
#define DNS_TYPE_AAAA (28)
#define DNS_CLASS_IN (1)
/** @} */
/**
* @name Field lengths
* @{

120
sys/include/net/dns/msg.h Normal file
View File

@ -0,0 +1,120 @@
/*
* Copyright (C) 2021 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @defgroup net_dns_msg DNS message parser and composer
* @ingroup net_dns
* @brief Parsing and composition of DNS messages
* @{
*
* @file
* @brief Definitions for parsing and composition of DNS messages
*
* @author Martine Lenders <m.lenders@fu-berlin.de>
*/
#ifndef NET_DNS_MSG_H
#define NET_DNS_MSG_H
#include <stdint.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @defgroup net_dns_msg_conf DNS message parsing and composition configuration
* @ingroup config
* @{
*/
/**
* @brief maximum DNS message length
*/
#ifndef CONFIG_DNS_MSG_LEN
#define CONFIG_DNS_MSG_LEN (128U)
#endif /* CONFIG_DNS_MSG_LEN */
/** @} */
/**
* @brief DNS internal structure
*
* @see [RFC 1035, section 4.1.1](https://tools.ietf.org/html/rfc1035#section-4.1.1)
*/
typedef struct {
uint16_t id; /**< identifier */
/**
* @brief flags
*
* +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
* |QR| Opcode |AA|TC|RD|RA|Z |AD|CD| RCODE |
* +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*
* - QR: Query (0) or Response (1)
* - Opcode: Kind of query
* - AA: Authoritative Answer
* - TC: Truncated
* - RD: Recursion Desired
* - RA: Recursion Available
* - Z: Reserved
* - AD: Authentic Data (see [RFC 4035](https://tools.ietf.org/html/4035))
* - CD: Checking Disabled (see [RFC 4035](https://tools.ietf.org/html/4035))
* - RCODE: Response Code
*/
uint16_t flags;
uint16_t qdcount; /**< number of question entries */
uint16_t ancount; /**< number of answer resource records */
uint16_t nscount; /**< number of name server resource records */
uint16_t arcount; /**< number of additional records */
uint8_t payload[]; /**< payload */
} dns_hdr_t;
/**
* @brief Composes a DNS query message
*
* The query will request an A or AAAA IN record for @p domain_name depending on
* @p family:
*
* - When @p family is `AF_INET` or `AF_UNSPEC` a query for an A record will be
* added
* - When @p family is `AF_INET6` or `AF_UNSPEC` a query for an AAAA record will
* be added
*
* @param[out] dns_buf A buffer of length @ref CONFIG_DNS_MSG_LEN
* @param[in] domain_name The domain name to query.
* @param[in] id The ID for the query.
* @param[in] family Either `AF_UNSPEC`, `AF_INET`, or `AF_INET6`.
* Determines the address records for @p domain_name
* queried.
*
* @return Size of the composed query in bytes.
*/
size_t dns_msg_compose_query(void *dns_buf, const char *domain_name,
uint16_t id, int family);
/**
* @brief Parses a DNS response message
*
* @param[in] buf The message to parse.
* @param[in] len Length of @p buf.
* @param[in] family The address family used to compose the query for
* this response (see @ref dns_msg_compose_query())
* @param[out] addr_out The IP address returned by the response.
*
* @return Length of the @p addr_out on success.
* @return -EBADMSG, when an address corresponding to @p family can not be found
* in @p buf.
*/
int dns_msg_parse_reply(const uint8_t *buf, size_t len, int family,
void *addr_out);
#ifdef __cplusplus
}
#endif
#endif /* NET_DNS_MSG_H */
/** @} */

22
sys/include/net/sock/dns.h
View File

@ -27,38 +27,22 @@
#include <stdint.h>
#include <unistd.h>
#include "net/dns/msg.h"
#include "net/sock/udp.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief DNS internal structure
*/
typedef struct {
uint16_t id; /**< read */
uint16_t flags; /**< DNS */
uint16_t qdcount; /**< RFC */
uint16_t ancount; /**< for */
uint16_t nscount; /**< detailed */
uint16_t arcount; /**< explanations */
uint8_t payload[]; /**< !! */
} sock_dns_hdr_t;
/**
* @name DNS defines
* @{
*/
#define DNS_TYPE_A (1)
#define DNS_TYPE_AAAA (28)
#define DNS_CLASS_IN (1)
#define SOCK_DNS_PORT (53)
#define SOCK_DNS_RETRIES (2)
#define SOCK_DNS_BUF_LEN (128) /* we're in embedded context. */
#define SOCK_DNS_MAX_NAME_LEN (SOCK_DNS_BUF_LEN - sizeof(sock_dns_hdr_t) - 4)
#define SOCK_DNS_MAX_NAME_LEN (CONFIG_DNS_MSG_LEN - sizeof(dns_hdr_t) - 4)
/** @} */
/**

5
sys/net/application_layer/dns/Makefile
View File

@ -1,2 +1,5 @@
MODULE=sock_dns
SRC :=
SUBMODULE := 1
include $(RIOTBASE)/Makefile.base

136
sys/net/application_layer/dns/dns.c → sys/net/application_layer/dns/msg.c
View File

@ -7,31 +7,24 @@
*/
/**
* @ingroup net_sock_dns
* @{
*
* @file
* @brief sock DNS client implementation
* @author Kaspar Schleiser <kaspar@schleiser.de>
* @}
* @author Martine Lenders <m.lenders@fu-berlin.de>
*/
#include <arpa/inet.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include "net/dns.h"
#include "net/sock/udp.h"
#include "net/sock/dns.h"
#ifdef RIOT_VERSION
#include "byteorder.h"
#endif
/* min domain name length is 1, so minimum record length is 7 */
#define DNS_MIN_REPLY_LEN (unsigned)(sizeof(sock_dns_hdr_t ) + 7)
/* global DNS server UDP endpoint */
sock_udp_ep_t sock_dns_server;
#include "net/dns/msg.h"
static ssize_t _enc_domain_name(uint8_t *out, const char *domain_name)
{
@ -68,14 +61,15 @@ static unsigned _put_short(uint8_t *out, uint16_t val)
return 2;
}
static unsigned _get_short(uint8_t *buf)
static unsigned _get_short(const uint8_t *buf)
{
uint16_t _tmp;
memcpy(&_tmp, buf, 2);
return _tmp;
}
static ssize_t _skip_hostname(const uint8_t *buf, size_t len, uint8_t *bufpos)
static ssize_t _skip_hostname(const uint8_t *buf, size_t len,
const uint8_t *bufpos)
{
const uint8_t *buflim = buf + len;
unsigned res = 0;
@ -102,11 +96,46 @@ static ssize_t _skip_hostname(const uint8_t *buf, size_t len, uint8_t *bufpos)
return res + 1;
}
static int _parse_dns_reply(uint8_t *buf, size_t len, void* addr_out, int family)
size_t dns_msg_compose_query(void *dns_buf, const char *domain_name,
uint16_t id, int family)
{
uint8_t *buf = dns_buf;
dns_hdr_t *hdr = (dns_hdr_t*) buf;
memset(hdr, 0, sizeof(*hdr));
hdr->id = id;
hdr->flags = htons(0x0120);
hdr->qdcount = htons(1 + (family == AF_UNSPEC));
uint8_t *bufpos = buf + sizeof(*hdr);
unsigned _name_ptr;
if ((family == AF_INET6) || (family == AF_UNSPEC)) {
_name_ptr = (bufpos - buf);
bufpos += _enc_domain_name(bufpos, domain_name);
bufpos += _put_short(bufpos, htons(DNS_TYPE_AAAA));
bufpos += _put_short(bufpos, htons(DNS_CLASS_IN));
}
if ((family == AF_INET) || (family == AF_UNSPEC)) {
if (family == AF_UNSPEC) {
bufpos += _put_short(bufpos, htons((0xc000) | (_name_ptr)));
}
else {
bufpos += _enc_domain_name(bufpos, domain_name);
}
bufpos += _put_short(bufpos, htons(DNS_TYPE_A));
bufpos += _put_short(bufpos, htons(DNS_CLASS_IN));
}
return bufpos - buf;
}
int dns_msg_parse_reply(const uint8_t *buf, size_t len, int family,
void *addr_out)
{
const uint8_t *buflim = buf + len;
sock_dns_hdr_t *hdr = (sock_dns_hdr_t*) buf;
uint8_t *bufpos = buf + sizeof(*hdr);
const dns_hdr_t *hdr = (dns_hdr_t *)buf;
const uint8_t *bufpos = buf + sizeof(*hdr);
/* skip all queries that are part of the reply */
for (unsigned n = 0; n < ntohs(hdr->qdcount); n++) {
@ -166,78 +195,7 @@ static int _parse_dns_reply(uint8_t *buf, size_t len, void* addr_out, int family
return addrlen;
}
return -1;
return -EBADMSG;
}
int sock_dns_query(const char *domain_name, void *addr_out, int family)
{
static uint8_t dns_buf[SOCK_DNS_BUF_LEN];
if (sock_dns_server.port == 0) {
return -ECONNREFUSED;
}
if (strlen(domain_name) > SOCK_DNS_MAX_NAME_LEN) {
return -ENOSPC;
}
sock_udp_t sock_dns;
ssize_t res = sock_udp_create(&sock_dns, NULL, &sock_dns_server, 0);
if (res) {
goto out;
}
uint16_t id = 0; /* random? */
for (int i = 0; i < SOCK_DNS_RETRIES; i++) {
uint8_t *buf = dns_buf;
sock_dns_hdr_t *hdr = (sock_dns_hdr_t*) buf;
memset(hdr, 0, sizeof(*hdr));
hdr->id = id;
hdr->flags = htons(0x0120);
hdr->qdcount = htons(1 + (family == AF_UNSPEC));
uint8_t *bufpos = buf + sizeof(*hdr);
unsigned _name_ptr;
if ((family == AF_INET6) || (family == AF_UNSPEC)) {
_name_ptr = (bufpos - buf);
bufpos += _enc_domain_name(bufpos, domain_name);
bufpos += _put_short(bufpos, htons(DNS_TYPE_AAAA));
bufpos += _put_short(bufpos, htons(DNS_CLASS_IN));
}
if ((family == AF_INET) || (family == AF_UNSPEC)) {
if (family == AF_UNSPEC) {
bufpos += _put_short(bufpos, htons((0xc000) | (_name_ptr)));
}
else {
bufpos += _enc_domain_name(bufpos, domain_name);
}
bufpos += _put_short(bufpos, htons(DNS_TYPE_A));
bufpos += _put_short(bufpos, htons(DNS_CLASS_IN));
}
res = sock_udp_send(&sock_dns, buf, (bufpos-buf), NULL);
if (res <= 0) {
continue;
}
res = sock_udp_recv(&sock_dns, dns_buf, sizeof(dns_buf), 1000000LU, NULL);
if (res > 0) {
if (res > (int)DNS_MIN_REPLY_LEN) {
if ((res = _parse_dns_reply(dns_buf, res, addr_out,
family)) > 0) {
goto out;
}
}
else {
res = -EBADMSG;
}
}
}
out:
sock_udp_close(&sock_dns);
return res;
}
/** @} */

1
sys/net/application_layer/sock_dns/Makefile Normal file
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@ -0,0 +1 @@
include $(RIOTBASE)/Makefile.base

75
sys/net/application_layer/sock_dns/dns.c Normal file
View File

@ -0,0 +1,75 @@
/*
* Copyright (C) 2017 Kaspar Schleiser <kaspar@schleiser.de>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup net_sock_dns
* @{
* @file
* @brief sock DNS client implementation
* @author Kaspar Schleiser <kaspar@schleiser.de>
* @}
*/
#include <errno.h>
#include "net/dns.h"
#include "net/dns/msg.h"
#include "net/sock/udp.h"
#include "net/sock/dns.h"
/* min domain name length is 1, so minimum record length is 7 */
#define DNS_MIN_REPLY_LEN (unsigned)(sizeof(dns_hdr_t ) + 7)
/* global DNS server UDP endpoint */
sock_udp_ep_t sock_dns_server;
int sock_dns_query(const char *domain_name, void *addr_out, int family)
{
static uint8_t dns_buf[CONFIG_DNS_MSG_LEN];
if (sock_dns_server.port == 0) {
return -ECONNREFUSED;
}
if (strlen(domain_name) > SOCK_DNS_MAX_NAME_LEN) {
return -ENOSPC;
}
sock_udp_t sock_dns;
ssize_t res = sock_udp_create(&sock_dns, NULL, &sock_dns_server, 0);
if (res) {
goto out;
}
uint16_t id = 0;
for (int i = 0; i < SOCK_DNS_RETRIES; i++) {
size_t buflen = dns_msg_compose_query(dns_buf, domain_name, id, family);
res = sock_udp_send(&sock_dns, dns_buf, buflen, NULL);
if (res <= 0) {
continue;
}
res = sock_udp_recv(&sock_dns, dns_buf, sizeof(dns_buf), 1000000LU, NULL);
if (res > 0) {
if (res > (int)DNS_MIN_REPLY_LEN) {
if ((res = dns_msg_parse_reply(dns_buf, res, family,
addr_out)) > 0) {
goto out;
}
}
else {
res = -EBADMSG;
}
}
}
out:
sock_udp_close(&sock_dns);
return res;
}