net: dns: dns-sd: support dns service discovery (e7e58439) · Commits · Wenxi XU / zephyr

CODEOWNERS

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		@@ -532,7 +532,7 @@
		/subsys/net/buf.c @jukkar @jhedberg @tbursztyka @pfalcon
		/subsys/net/ip/ @jukkar @tbursztyka @pfalcon
		/subsys/net/lib/ @jukkar @tbursztyka @pfalcon
		/subsys/net/lib/dns/ @jukkar @tbursztyka @pfalcon
		/subsys/net/lib/dns/ @jukkar @tbursztyka @pfalcon @cfriedt
		/subsys/net/lib/lwm2m/ @rlubos
		/subsys/net/lib/config/ @jukkar @tbursztyka @pfalcon
		/subsys/net/lib/mqtt/ @jukkar @tbursztyka @rlubos

include/linker/common-rom.ld

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		@@ -134,6 +134,10 @@
		} GROUP_LINK_IN(ROMABLE_REGION)
		#endif /* CONFIG_EMUL */

		#if defined(CONFIG_DNS_SD)
		Z_ITERABLE_SECTION_ROM(dns_sd_rec, 4)
		#endif

		SECTION_DATA_PROLOGUE(log_const_sections,,)
		{
		__log_const_start = .;

include/net/dns_sd.h

0 → 100644

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		/** @file
		* @brief DNS Service Discovery
		*/

		/*
		* Copyright (c) 2020 Friedt Professional Engineering Services, Inc
		*
		* SPDX-License-Identifier: Apache-2.0
		*/

		#ifndef ZEPHYR_INCLUDE_NET_DNS_SD_H_
		#define ZEPHYR_INCLUDE_NET_DNS_SD_H_

		#include <stdint.h>
		#include <sys/byteorder.h>

		#ifdef __cplusplus
		extern "C" {
		#endif

		/**
		* @brief DNS Service Discovery
		*
		* @details This API enables services to be advertised via DNS. To
		* advvertise a service, system or application code should use
		* @ref DNS_SD_REGISTER_TCP_SERVICE or
		* @ref DNS_SD_REGISTER_UDP_SERVICE.
		*
		* @see <a href="https://tools.ietf.org/html/rfc6763">RFC 6763</a>
		*
		* @defgroup dns_sd DNS Service Discovery
		* @ingroup networking
		* @{
		*/

		/** RFC 1034 Section 3.1 */
		#define DNS_SD_INSTANCE_MIN_SIZE 1
		/** RFC 1034 Section 3.1, RFC 6763 Section 7.2 */
		#define DNS_SD_INSTANCE_MAX_SIZE 63
		/** RFC 6763 Section 7.2 - inclusive of underscore */
		#define DNS_SD_SERVICE_MIN_SIZE 2
		/** RFC 6763 Section 7.2 - inclusive of underscore */
		#define DNS_SD_SERVICE_MAX_SIZE 16
		/** RFC 6763 Section 4.1.2 */
		#define DNS_SD_SERVICE_PREFIX '_'
		/** RFC 6763 Section 4.1.2 - either _tcp or _udp (case insensitive) */
		#define DNS_SD_PROTO_SIZE 4
		/** ICANN Rules for TLD naming */
		#define DNS_SD_DOMAIN_MIN_SIZE 2
		/** RFC 1034 Section 3.1, RFC 6763 Section 7.2 */
		#define DNS_SD_DOMAIN_MAX_SIZE 63

		/**
		* @brief Register a service for DNS Service Discovery
		*
		* This macro should be used for advanced use cases. Two simple use cases are
		* when a custom @p domain or a custom (non-standard) @p proto is required.
		*
		* Another use case is when the port number is not preassigned. That could
		* be for a number of reasons, but the most common use case would be for
		* ephemeral port usage - i.e. when the service is bound using port number 0.
		* In that case, Zephyr (like other OS's) will simply choose an unused port.
		* When using ephemeral ports, it can be helpful to assign @p port to the
		* @ref sockaddr_in.sin_port field of an IPv4 @ref sockaddr_in, or to the
		* @ref sockaddr_in6.sin6_port field of an IPv6 @ref sockaddr_in6.
		*
		* The service can be referenced using the @p id variable.
		*
		* @param id variable name for the DNS-SD service record
		* @param instance name of the service instance such as "My HTTP Server"
		* @param service name of the service, such as "_http"
		* @param proto protocol used by the service - either "_tcp" or "_udp"
		* @param domain the domain of the service, such as "local"
		* @param text information for the DNS TXT record
		* @param port a pointer to the port number that this service will use
		*/
		#define DNS_SD_REGISTER_SERVICE(id, instance, service, proto, domain, \
		text, port) \
		static const Z_STRUCT_SECTION_ITERABLE(dns_sd_rec, id) = { \
		instance, \
		service, \
		proto, \
		domain, \
		(const char *)text, \
		sizeof(text) - 1, \
		port \
		}

		/**
		* @brief Register a TCP service for DNS Service Discovery
		*
		* This macro can be used for service advertisement using DNS-SD.
		*
		* The service can be referenced using the @p id variable.
		*
		* Example (with TXT):
		* @code{c}
		* #include <net/dns_sd.h>
		* static const bar_txt[] = {
		* "\x06" "path=/"
		* "\x0f" "this=is the way"
		* "\x0e" "foo or=foo not"
		* "\x17" "this=has\0embedded\0nulls"
		* "\x04" "true"
		* };
		* // Possibly use an ephemeral port
		* // Possibly only assign bar_port when the service is running
		* static uint16_t bar_port;
		* DNS_SD_REGISTER_TCP_SERVICE(bar, CONFIG_NET_HOSTNAME,
		* "_bar", "local", bar_txt, &bar_port);
		* @endcode{c}
		*
		* TXT records begin with a single length byte (hex-encoded)
		* and contain key=value pairs. Thus, the length of the key-value pair
		* must not exceed 255 bytes. Care must be taken to ensure that the
		* encoded length value is correct.
		*
		* For additional rules on TXT encoding, see RFC 6763, Section 6.

		* @param id variable name for the DNS-SD service record
		* @param instance name of the service instance such as "My HTTP Server"
		* @param service name of the service, such as "_http"
		* @param domain the domain of the service, such as "local"
		* @param text information for the DNS TXT record
		* @param port the port number that this service will use
		*
		* @see <a href="https://tools.ietf.org/html/rfc6763">RFC 6763</a>
		*/
		#define DNS_SD_REGISTER_TCP_SERVICE(id, instance, service, domain, text, \
		port) \
		static const uint16_t id ## _port = sys_cpu_to_be16(port); \
		DNS_SD_REGISTER_SERVICE(id, instance, service, "_tcp", domain, \
		text, &id ## _port)

		/**
		* @brief Register a UDP service for DNS Service Discovery
		*
		* This macro can be used for service advertisement using DNS-SD.
		*
		* The service can be referenced using the @p id variable.
		*
		* Example (no TXT):
		* @code{c}
		* #include <net/dns_sd.h>
		* #include <sys/byteorder.h>
		* static const foo_port = sys_cpu_to_be16(4242);
		* DNS_SD_REGISTER_UDP_SERVICE(foo, CONFIG_NET_HOSTNAME,
		* "_foo", DNS_SD_EMPTY_TXT, &foo_port);
		* @endcode{c}
		*
		* @param id variable name for the DNS-SD service record
		* @param instance name of the service instance such as "My TFTP Server"
		* @param service name of the service, such as "_tftp"
		* @param domain the domain of the service, such as "local" or "zephyrproject.org"
		* @param text information for the DNS TXT record
		* @param port a pointer to the port number that this service will use
		*
		* @see <a href="https://tools.ietf.org/html/rfc6763">RFC 6763</a>
		*/
		#define DNS_SD_REGISTER_UDP_SERVICE(id, instance, service, domain, text, \
		port) \
		static const uint16_t id ## _port = sys_cpu_to_be16(port); \
		DNS_SD_REGISTER_SERVICE(id, instance, service, "_udp", domain, \
		text, &id ## _port)

		/** Empty DNS-SD TXT specifier */
		#define DNS_SD_EMPTY_TXT dns_sd_empty_txt

		/** @cond INTERNAL_HIDDEN */

		/**
		* @brief DNS Service Discovery record
		*
		* This structure used in the implementation of RFC 6763 and should not
		* need to be accessed directly from application code.
		*
		* The @a port pointer must be non-NULL. When the value in @a port
		* is non-zero, the service is advertized as being on that particular
		* port. When the value in @a port is zero, then the service is not
		* advertised.
		*
		* Thus, it is possible for multiple services to advertise on a
		* particular port if they hard-code the port.
		*
		* @internal
		*
		* @see <a href="https://tools.ietf.org/html/rfc6763">RFC 6763</a>
		*/
		struct dns_sd_rec {
		/** <Instance> - e.g. "My HTTP Server" */
		const char *instance;
		/** Top half of the <Service> such as "_http" */
		const char *service;
		/** Bottom half of the <Service> "_tcp" or "_udp" */
		const char *proto;
		/** <Domain> such as "local" or "zephyrproject.org" */
		const char *domain;
		/** DNS TXT record */
		const char *text;
		/** Size (in bytes) of the DNS TXT record */
		size_t text_size;
		/** A pointer to the port number used by the service */
		const uint16_t *port;
		};

		/**
		* @brief Empty TXT specifier for DNS-SD
		*
		* @internal
		*/
		extern const char dns_sd_empty_txt[1];

		/** @endcond */

		/**
		* @brief Obtain the size of DNS-SD TXT data
		*
		* @param rec the record to in question
		* @return the size of the text field
		*/
		static inline size_t dns_sd_txt_size(const struct dns_sd_rec *rec)
		{
		return rec->text_size;
		}

		/**
		* @}
		*/

		#ifdef __cplusplus
		};
		#endif

		#endif /* ZEPHYR_INCLUDE_NET_DNS_SD_H_ */

subsys/net/lib/dns/CMakeLists.txt

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		@@ -6,6 +6,7 @@ zephyr_library()
		zephyr_library_sources(dns_pack.c)

		zephyr_library_sources_ifdef(CONFIG_DNS_RESOLVER resolve.c)
		zephyr_library_sources_ifdef(CONFIG_DNS_SD dns_sd.c)

		if(CONFIG_MDNS_RESPONDER)
		zephyr_library_sources(mdns_responder.c)

subsys/net/lib/dns/Kconfig

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		@@ -198,3 +198,21 @@ config LLMNR_RESOLVER_ADDITIONAL_BUF_CTR
		Number of additional buffers available for the LLMNR responder.

		endif # LLMNR_RESPONDER

		config DNS_SD
		bool "Enable DNS Service Discovery"
		help
		This option enables DNS Service Discovery for Zephyr. It can
		be enabled for virtually any network service with only a few
		lines of code and works for both Unicast and Multicast DNS.
		See RFC 6763 for more details about DNS-SD.

		if DNS_SD

		module = DNS_SD
		module-dep = NET_LOG
		module-str = Log level for DNS-SD
		module-help = Enables DNS Service Discovery code to output debug messages.
		source "subsys/net/Kconfig.template.log_config.net"

		endif # DNS_SD

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