sdk/fidl/fuchsia.net.routes/routes.fidl

// Copyright 2020 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.
@available(added=7)
library fuchsia.net.routes;

using fuchsia.net;
using zx;

/// A placeholder for empty values.
@available(added=HEAD)
type Empty = struct {};

/// The properties of the route that were explicitly specified at the time the
/// route was created.
@available(added=HEAD)
type SpecifiedRouteProperties = table {
    /// The route's effective metric will be determined by whichever value is
    /// specified below.
    1: metric @generated_name("SpecifiedMetric") strict union {
        /// The route's metric will be this explicitly specified value.
        1: explicit_metric fuchsia.net.RouteMetric;
        /// The route's metric is inherited from its outbound interface, and
        /// will track this value as it changes throughout the route's lifetime.
        /// Clients may prefer this approach if they wish to offload the
        /// responsibility of "which route is best" to the system.
        2: inherited_from_interface Empty;
    };
};

/// The effective properties of a route installed in the system.
@available(added=HEAD)
type EffectiveRouteProperties = table {
    /// The route's effective metric, dependent on the value of the route's
    /// [`SpecifiedRouteProperties`]. If the `specified_metric` is
    /// `explicit_metric`, this value will be identical to the provided value;
    /// if the `specified_metric` is `inherited_from_interface` this value will
    /// be the interface's routing metric.
    1: metric fuchsia.net.RouteMetric;
};

/// The maximum number of events that can be returned by one call to `Watch()`.
// Rationale for the current value:
// Prefer an "as large as possible" value for `MAX_EVENTS`, because FIDL
// `vectors` are variable length, meaning a `vector` of one event won't waste
// space on the wire. Both [`InstalledRouteV4`] and [`InstalledRouteV6`] are
// less than 64 bytes, and the maximum FIDL message size is 64K. While we could
// probably squeeze in 1024 events, 512 is a nice compromise that allows the
// the types to grow as more fields are added.
@available(added=HEAD)
const MAX_EVENTS uint16 = 512;

/// Collection of addresses and identifiers describing a network destination.
///
/// A `Destination` is the "next-hop" for a routed packet.
type Destination = table {
    /// The IP address of the destination.
    1: address fuchsia.net.IpAddress;
    /// The MAC address of the destination. Only set if the destination is on a
    /// link that requires a MAC address.
    2: mac fuchsia.net.MacAddress;
    /// The interface identifier over which the destination can be reached.
    3: interface_id fuchsia.net.InterfaceId;
    /// The preferred local IP address used to communicate with the destination.
    4: source_address fuchsia.net.IpAddress;
};

/// Provides access to the system's routing state.
@discoverable
closed protocol State {
    /// Resolves the route to a destination.
    ///
    /// + request `destination` the IP address to resolve a route to. If the
    ///     unspecified address (all zeroes) is provided, the default route will
    ///     be returned. The variant of `destination` determines variant of
    ///     [`fuchsia.net/IpAddress`] fields in the resolved route.
    /// - response `result` contains the resolved route to `destination`.
    /// * error `ZX_ERR_ADDRESS_UNREACHABLE` if `destination` can't be resolved.
    // TODO(brunodalbo) In the future we may have multiple tables and we may
    // want to let the caller specify which table to use. Alternatively, if
    // multiple tables are accessed through scoped objects, a `Resolve` call in
    // a table would have the same effect.
    strict Resolve(struct {
        destination fuchsia.net.IpAddress;
    }) -> (struct {
        /// A resolved route.
        ///
        /// Contains the information for the "next-hop" or immediate-destination
        /// that is the result of a route resolution. A resolved route is only
        /// meaningful in the context of a requested destination.
        result @generated_name("Resolved") strict union {
            /// The requested destination is directly reachable.
            1: direct Destination;
            /// The requested destination is reachable through a gateway, thus
            /// the next hop is the gateway.
            2: gateway Destination;
        };
    }) error zx.Status;
};