net: dns: dns-sd: support dns service discovery

CODEOWNERS

@@ -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

@@ -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

@@ -0,0 +1,234 @@
+/** @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_ */

include/net/net_context.h

@@ -1125,6 +1125,22 @@ static inline void net_context_setup_pools(struct net_context *context,
 #define net_context_setup_pools(context, tx_pool, data_pool)
 #endif
 
+/**
+ * @brief Check if a port is in use (bound)
+ *
+ * This function checks if a port is bound with respect to the specified
+ * @p ip_proto and @p local_addr.
+ *
+ * @param ip_proto the IP protocol
+ * @param local_port the port to check
+ * @param local_addr the network address
+ *
+ * @return true if the port is bound
+ * @return false if the port is not bound
+ */
+bool net_context_port_in_use(enum net_ip_protocol ip_proto,
+	uint16_t local_port, const struct sockaddr *local_addr);
+
 #ifdef __cplusplus
 }
 #endif

samples/net/mdns_responder/README.rst

@@ -30,7 +30,7 @@ Build and run the mdns-responder sample application like this:
    :goals: build
    :compact:
 
-After the mdns-responder sample application is started, it will wait queries
+After the mdns-responder sample application is started, it will await queries
 from the network.
 
 Open a terminal window in your host and type:
@@ -56,3 +56,20 @@ If the query is successful, then following information is printed:
 .. code-block:: console
 
     zephyr.local	2001:db8::1
+
+Lastly, resolve services using DNS Service Discovery:
+
+.. code-block:: console
+
+    $ avahi-browse -t -r _zephyr._tcp
+
+If the query is successful, then the following information is printed:
+
+.. code-block:: console
+
+    +   zeth IPv6 zephyr                                        _zephyr._tcp         local
+    =   zeth IPv6 zephyr                                        _zephyr._tcp         local
+       hostname = [zephyr.local]
+       address = [192.0.2.1]
+       port = [4242]
+       txt = []

samples/net/mdns_responder/overlay-802154.conf

@@ -0,0 +1,11 @@
+CONFIG_NET_IPV4=n
+CONFIG_NET_CONFIG_NEED_IPV4=n
+CONFIG_NET_CONFIG_MY_IPV4_ADDR=""
+CONFIG_NET_CONFIG_PEER_IPV4_ADDR=""
+CONFIG_NET_CONFIG_MY_IPV4_GW=""
+
+CONFIG_NET_L2_IEEE802154=y
+CONFIG_NET_L2_IEEE802154_SHELL=y
+CONFIG_NET_L2_IEEE802154_LOG_LEVEL_INF=y
+
+CONFIG_NET_CONFIG_IEEE802154_CHANNEL=26

samples/net/mdns_responder/overlay-bt.conf

@@ -0,0 +1,17 @@
+CONFIG_BT=y
+CONFIG_BT_DEBUG_LOG=y
+CONFIG_BT_SMP=y
+CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_CENTRAL=y
+CONFIG_BT_L2CAP_DYNAMIC_CHANNEL=y
+CONFIG_BT_DEVICE_NAME="Zephyr Echo Server"
+CONFIG_NET_L2_BT=y
+CONFIG_NET_IPV4=n
+CONFIG_NET_IPV6=y
+CONFIG_NET_CONFIG_BT_NODE=y
+CONFIG_NET_CONFIG_NEED_IPV6=y
+CONFIG_NET_IPV4=n
+CONFIG_NET_CONFIG_NEED_IPV4=n
+CONFIG_NET_CONFIG_MY_IPV4_ADDR=""
+CONFIG_NET_CONFIG_PEER_IPV4_ADDR=""
+CONFIG_NET_CONFIG_MY_IPV4_GW=""

samples/net/mdns_responder/overlay-qemu_cortex_m3_eth.conf

@@ -0,0 +1,7 @@
+CONFIG_NET_L2_ETHERNET=y
+CONFIG_NET_QEMU_ETHERNET=y
+
+CONFIG_ETH_STELLARIS=y
+
+CONFIG_NET_SLIP_TAP=n
+CONFIG_SLIP=n

samples/net/mdns_responder/prj.conf

@@ -10,6 +10,8 @@ CONFIG_NET_HOSTNAME_UNIQUE=n
 CONFIG_NET_HOSTNAME="zephyr"
 
 CONFIG_MDNS_RESPONDER=y
+CONFIG_DNS_SD=y
+CONFIG_MDNS_RESPONDER_DNS_SD=y
 
 CONFIG_ENTROPY_GENERATOR=y
 CONFIG_TEST_RANDOM_GENERATOR=y
@@ -36,3 +38,6 @@ CONFIG_NET_CONFIG_PEER_IPV6_ADDR="2001:db8::2"
 CONFIG_NET_CONFIG_MY_IPV4_ADDR="192.0.2.1"
 CONFIG_NET_CONFIG_PEER_IPV4_ADDR="192.0.2.2"
 CONFIG_NET_CONFIG_MY_IPV4_GW="192.0.2.2"
+
+CONFIG_NET_SOCKETS=y
+CONFIG_NET_SOCKETS_POSIX_NAMES=y

samples/net/mdns_responder/src/main.c

@@ -12,10 +12,13 @@ LOG_MODULE_REGISTER(net_mdns_responder_sample, LOG_LEVEL_DBG);
 #include <zephyr.h>
 #include <net/net_core.h>
 
+extern void service(void);
+
 /* Note that this application does not do anything itself.
  * It is just a placeholder for waiting mDNS queries.
  */
 void main(void)
 {
 	LOG_INF("Waiting mDNS queries...");
+	service();
 }