sdk/fidl/fuchsia.net.mdns/service_instance_publisher.fidl

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.net.mdns;

using fuchsia.net;
using zx;

/// Discoverable protocol for publishing service instances.
@available(added=9)
@discoverable
protocol ServiceInstancePublisher {
    /// Publishes a service instance. `publication_responder` is consulted via its
    /// `OnPublication` method for initial announcements and to answer queries.
    /// The service is published until the `publication_responder` channel closes. In
    /// addition to announcements and queries for the service type, all queries
    /// for subtypes are answered subject to filtering through the responder.
    ///
    /// + request `service` name of the type of service to be published. For example, cast uses
    ///   '_googlecast._tcp.'.
    /// + request `instance` name of the instance to be published. This is often a descriptive name
    ///   such as `Office Printer` or a name containing a large random number.
    /// + request `options` options to be applied to the publication.
    /// + request `publication_responder` client end of the `ServiceInstancePublicationResponder`
    ///   channel consulted when formulating service instance announcements and query responses.
    /// * error reason the requested operation failed.
    ///
    /// If a service with the same service and instance names is already published, the
    /// old publication will be terminated, and the responder channel for the old
    /// publication will be closed.
    PublishServiceInstance(resource struct {
        service service_name;
        instance instance_name;
        options ServiceInstancePublicationOptions;
        publication_responder client_end:ServiceInstancePublicationResponder;
    }) -> () error PublishServiceInstanceError;
};

/// Options for `ServiceInstancePublisher.PublishServiceInstance`.
@available(added=9)
type ServiceInstancePublicationOptions = table {
    /// The media (wired, wireless, both) of the interfaces on which the service instance should
    /// be published. The default `media` value depends on whether the `ServiceInstancePublisher`
    /// is associated with a proxy host. If so, the default matches the `media` value of the
    /// `ProxyHostPublicationOptions` for the proxy host. If not, the default is both wired and
    /// wireless media.
    1: media Media;

    /// The IP versions (V4, V6, both) with which the service instance should
    /// be published. The default `ip_versions` value depends on whether the
    /// `ServiceInstancePublisher` is associated with a proxy host. If so, the default matches the
    /// `ip_versions` value of the `ProxyHostPublicationOptions` for the proxy host. If not, the
    /// default value is both IPv4 and IPv6.
    2: ip_versions IpVersions;

    /// Whether a probe for conflicting instances should be performed prior to publishing the
    /// instance. If this value is not supplied, probing is performed.
    3: perform_probe bool;
};

/// Error values for `ServiceInstancePublisher.PublishServiceInstance`.
@available(added=9)
type PublishServiceInstanceError = strict enum : uint32 {
    /// The specified service instance is already being published by the mDNS local implementation.
    ALREADY_PUBLISHED_LOCALLY = 1;

    /// The specified service instance is already being published by another host on the subnet.
    /// This result occurs when an initial probe discovers a conflicting service instance.
    ALREADY_PUBLISHED_ON_SUBNET = 2;
};

/// Client-supplied publication responder interface.
@available(added=9)
protocol ServiceInstancePublicationResponder {
    /// Provides instance information for initial announcements and query
    /// responses relating to the service instance specified in
    /// `ServiceInstancePublisher.PublishServiceInstance`.
    ///
    /// + request `publication_cause` the action that motivates this publication.
    /// + request `subtype` the subtype if the publication relates to a subtype of the service,
    ///   otherwise null.
    /// + request `source_addresses` addresses from which queries arrived, if applicable.
    /// - response `publication` the desired publication. Strings in `publication.text` are sent
    ///   in the TXT resource.
    /// * error indicates the publication should not be sent.
    ///
    /// If no publication should be sent, this method should return a `DO_NOT_RESPOND` error.
    OnPublication(struct {
        publication_cause ServiceInstancePublicationCause;
        subtype subtype_name:optional;
        source_addresses vector<fuchsia.net.IpAddress>:MAX_ADDRESSES;
    }) -> (struct {
        publication ServiceInstancePublication;
    }) error OnPublicationError;

    /// Sets the subtypes for the service instance. The specified subtypes will
    /// be announced subject to filtering through the responder. The initial
    /// subtype collection is empty.
    -> SetSubtypes(struct {
        subtypes vector<subtype_name>:MAX_SUBTYPES;
    });

    /// Initiates reannouncement of the service instance due to a change in the
    /// instance's port number or text strings. All announcements are filtered
    /// through `OnPublication`, which replies with the new port and text
    /// values.
    -> Reannounce();
};

/// Error values for `ServiceInstancePublicationResponder.OnPublication`.
@available(added=9)
type OnPublicationError = strict enum : uint32 {
    /// Indicates the publisher should not respond to this publication request.
    DO_NOT_RESPOND = 1;
};

/// Describes the cause of a publication.
@available(added=9)
type ServiceInstancePublicationCause = strict enum : uint32 {
    /// Indicates the publication is part of an initial announcement.
    ANNOUNCEMENT = 1;

    /// Indicates the publication is in response to a question that requests a
    /// multicast response.
    QUERY_MULTICAST_RESPONSE = 2;

    /// Indicates the publication is in response to a question that requests a
    /// unicast response.
    QUERY_UNICAST_RESPONSE = 3;
};

/// Describes an initial instance announcement or query response. In typical
/// use, the default SRV priority, SRV weight and TTL values should be used. TTL
/// values are rounded down to the nearest second. TTL values less than one
/// second are not permitted and will result in the `ServiceInstancePublicationResponder`
/// channel being closed.
@available(added=9)
type ServiceInstancePublication = table {
    /// The port at which the service instance is addressable. This value is required.
    1: port uint16;

    /// Text strings describing the instance. If this value is not supplied, no text strings are
    /// associated with the instance in this publication.
    2: text vector<txt_character_string>:MAX_TEXT_STRINGS;

    /// The priority of the SRV resource record for this publication. See
    /// [RFC6763](https://tools.ietf.org/html/rfc6763) for details. If this value is not supplied,
    /// the default SRV priority of 0 is used.
    3: srv_priority uint16;

    /// The weight of the SRV resource record for this publication. See
    /// [RFC6763](https://tools.ietf.org/html/rfc6763) for details. If this value is not supplied,
    /// the default SRV weight of 0 is used.
    4: srv_weight uint16;

    /// Time-to-live for PTR resource records. If this value is not supplied, the default PTR TTL
    /// of 2 minutes is used. This value is rounded down to the nearest second.
    5: ptr_ttl zx.Duration;

    /// Time-to-live for SRV resource records. If this value is not supplied, the default SRV TTL
    /// of 2 minutes is used. This value is rounded down to the nearest second.
    6: srv_ttl zx.Duration;

    /// Time-to-live for TXT resource records. If this value is not supplied, the default TXT TTL
    /// of 75 minutes is used. This value is rounded down to the nearest second.
    7: txt_ttl zx.Duration;
};