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// Copyright 2024 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.
//! Common traits and types for dealing with abstracted frames.
use net_types::ethernet::Mac;
use net_types::ip::{Ip, IpVersionMarker};
use net_types::{BroadcastAddr, MulticastAddr};
use core::convert::Infallible as Never;
use core::fmt::Debug;
use packet::{BufferMut, SerializeError, Serializer};
use thiserror::Error;
use crate::error::ErrorAndSerializer;
/// A context for receiving frames.
///
/// Note: Use this trait as trait bounds, but always implement
/// [`ReceivableFrameMeta`] instead, which generates a `RecvFrameContext`
/// implementation.
pub trait RecvFrameContext<Meta, BC> {
/// Receive a frame.
///
/// `receive_frame` receives a frame with the given metadata.
fn receive_frame<B: BufferMut + Debug>(
&mut self,
bindings_ctx: &mut BC,
metadata: Meta,
frame: B,
);
}
impl<CC, BC> ReceivableFrameMeta<CC, BC> for Never {
fn receive_meta<B: BufferMut + Debug>(
self,
_core_ctx: &mut CC,
_bindings_ctx: &mut BC,
_frame: B,
) {
match self {}
}
}
/// A trait providing the receive implementation for some frame identified by a
/// metadata type.
///
/// This trait sidesteps orphan rules by allowing [`RecvFrameContext`] to be
/// implemented by the multiple core crates, given it can always be implemented
/// for a local metadata type. `ReceivableFrameMeta` should always be used for
/// trait implementations, while [`RecvFrameContext`] is used for trait bounds.
pub trait ReceivableFrameMeta<CC, BC> {
/// Receives this frame using the provided contexts.
fn receive_meta<B: BufferMut + Debug>(self, core_ctx: &mut CC, bindings_ctx: &mut BC, frame: B);
}
impl<CC, BC, Meta> RecvFrameContext<Meta, BC> for CC
where
Meta: ReceivableFrameMeta<CC, BC>,
{
fn receive_frame<B: BufferMut + Debug>(
&mut self,
bindings_ctx: &mut BC,
metadata: Meta,
frame: B,
) {
metadata.receive_meta(self, bindings_ctx, frame)
}
}
/// The error type for [`SendFrameError`].
#[derive(Error, Debug, PartialEq)]
pub enum SendFrameErrorReason {
/// Serialization failed due to failed size constraints.
#[error("size constraints violated")]
SizeConstraintsViolation,
/// Couldn't allocate space to serialize the frame.
#[error("failed to allocate")]
Alloc,
/// The transmit queue is full.
#[error("transmit queue is full")]
QueueFull,
}
impl<A> From<SerializeError<A>> for SendFrameErrorReason {
fn from(e: SerializeError<A>) -> Self {
match e {
SerializeError::Alloc(_) => Self::Alloc,
SerializeError::SizeLimitExceeded => Self::SizeConstraintsViolation,
}
}
}
/// Errors returned by [`SendFrameContext::send_frame`].
pub type SendFrameError<S> = ErrorAndSerializer<SendFrameErrorReason, S>;
/// A context for sending frames.
pub trait SendFrameContext<BC, Meta> {
/// Send a frame.
///
/// `send_frame` sends a frame with the given metadata. The frame itself is
/// passed as a [`Serializer`] which `send_frame` is responsible for
/// serializing. If serialization fails for any reason, the original,
/// unmodified `Serializer` is returned.
///
/// [`Serializer`]: packet::Serializer
fn send_frame<S>(
&mut self,
bindings_ctx: &mut BC,
metadata: Meta,
frame: S,
) -> Result<(), SendFrameError<S>>
where
S: Serializer,
S::Buffer: BufferMut;
}
/// A trait providing the send implementation for some frame identified by a
/// metadata type.
///
/// This trait sidesteps orphan rules by allowing [`SendFrameContext`] to be
/// implemented by the multiple core crates, given it can always be implemented
/// for a local metadata type. `SendableFrameMeta` should always be used for
/// trait implementations, while [`SendFrameContext`] is used for trait bounds.
pub trait SendableFrameMeta<CC, BC> {
/// Sends this frame metadata to the provided contexts.
fn send_meta<S>(
self,
core_ctx: &mut CC,
bindings_ctx: &mut BC,
frame: S,
) -> Result<(), SendFrameError<S>>
where
S: Serializer,
S::Buffer: BufferMut;
}
impl<CC, BC, Meta> SendFrameContext<BC, Meta> for CC
where
Meta: SendableFrameMeta<CC, BC>,
{
fn send_frame<S>(
&mut self,
bindings_ctx: &mut BC,
metadata: Meta,
frame: S,
) -> Result<(), SendFrameError<S>>
where
S: Serializer,
S::Buffer: BufferMut,
{
metadata.send_meta(self, bindings_ctx, frame)
}
}
/// The type of address used as the destination address in a device-layer frame.
///
/// `FrameDestination` is used to implement RFC 1122 section 3.2.2 and RFC 4443
/// section 2.4.e, which govern when to avoid sending an ICMP error message for
/// ICMP and ICMPv6 respectively.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum FrameDestination {
/// A unicast address - one which is neither multicast nor broadcast.
Individual {
/// Whether the frame's destination address belongs to the receiver.
local: bool,
},
/// A multicast address; if the addressing scheme supports overlap between
/// multicast and broadcast, then broadcast addresses should use the
/// `Broadcast` variant.
Multicast,
/// A broadcast address; if the addressing scheme supports overlap between
/// multicast and broadcast, then broadcast addresses should use the
/// `Broadcast` variant.
Broadcast,
}
impl FrameDestination {
/// Is this `FrameDestination::Broadcast`?
pub fn is_broadcast(self) -> bool {
self == FrameDestination::Broadcast
}
/// Creates a `FrameDestination` from a `mac` and `local_mac` destination.
pub fn from_dest(destination: Mac, local_mac: Mac) -> Self {
BroadcastAddr::new(destination)
.map(Into::into)
.or_else(|| MulticastAddr::new(destination).map(Into::into))
.unwrap_or_else(|| FrameDestination::Individual { local: destination == local_mac })
}
}
impl From<BroadcastAddr<Mac>> for FrameDestination {
fn from(_value: BroadcastAddr<Mac>) -> Self {
Self::Broadcast
}
}
impl From<MulticastAddr<Mac>> for FrameDestination {
fn from(_value: MulticastAddr<Mac>) -> Self {
Self::Multicast
}
}
/// The metadata required for a packet to get into the IP layer.
pub struct RecvIpFrameMeta<D, I: Ip> {
/// The device on which the IP frame was received.
pub device: D,
/// The link-layer destination address from the link-layer frame, if any.
/// `None` if the IP frame originated above the link-layer (e.g. pure IP
/// devices).
// NB: In the future, this field may also be `None` to represent link-layer
// protocols without destination addresses (i.e. PPP), but at the moment no
// such protocols are supported.
pub frame_dst: Option<FrameDestination>,
/// A marker for the Ip version in this frame.
pub marker: IpVersionMarker<I>,
}
impl<D, I: Ip> RecvIpFrameMeta<D, I> {
/// Creates a new `RecvIpFrameMeta` originating from `device` and `frame_dst`
/// option.
pub fn new(device: D, frame_dst: Option<FrameDestination>) -> RecvIpFrameMeta<D, I> {
RecvIpFrameMeta { device, frame_dst, marker: IpVersionMarker::new() }
}
}
#[cfg(any(test, feature = "testutils"))]
pub(crate) mod testutil {
use super::*;
use alloc::boxed::Box;
use alloc::vec::Vec;
/// A fake [`FrameContext`].
pub struct FakeFrameCtx<Meta> {
frames: Vec<(Meta, Vec<u8>)>,
should_error_for_frame:
Option<Box<dyn FnMut(&Meta) -> Option<SendFrameErrorReason> + Send>>,
}
impl<Meta> FakeFrameCtx<Meta> {
/// Closure which can decide to cause an error to be thrown when
/// handling a frame, based on the metadata.
pub fn set_should_error_for_frame<
F: Fn(&Meta) -> Option<SendFrameErrorReason> + Send + 'static,
>(
&mut self,
f: F,
) {
self.should_error_for_frame = Some(Box::new(f));
}
}
impl<Meta> Default for FakeFrameCtx<Meta> {
fn default() -> FakeFrameCtx<Meta> {
FakeFrameCtx { frames: Vec::new(), should_error_for_frame: None }
}
}
impl<Meta> FakeFrameCtx<Meta> {
/// Take all frames sent so far.
pub fn take_frames(&mut self) -> Vec<(Meta, Vec<u8>)> {
core::mem::take(&mut self.frames)
}
/// Get the frames sent so far.
pub fn frames(&self) -> &[(Meta, Vec<u8>)] {
self.frames.as_slice()
}
/// Pushes a frame to the context.
pub fn push(&mut self, meta: Meta, frame: Vec<u8>) {
self.frames.push((meta, frame))
}
}
impl<Meta, BC> SendableFrameMeta<FakeFrameCtx<Meta>, BC> for Meta {
fn send_meta<S>(
self,
core_ctx: &mut FakeFrameCtx<Meta>,
_bindings_ctx: &mut BC,
frame: S,
) -> Result<(), SendFrameError<S>>
where
S: Serializer,
S::Buffer: BufferMut,
{
if let Some(error) = core_ctx.should_error_for_frame.as_mut().and_then(|f| f(&self)) {
return Err(SendFrameError { serializer: frame, error });
}
let buffer = frame
.serialize_vec_outer()
.map_err(|(e, serializer)| SendFrameError { error: e.into(), serializer })?;
core_ctx.push(self, buffer.as_ref().to_vec());
Ok(())
}
}
/// A trait for abstracting contexts that may contain a [`FakeFrameCtx`].
pub trait WithFakeFrameContext<SendMeta> {
/// Calls the callback with a mutable reference to the [`FakeFrameCtx`].
fn with_fake_frame_ctx_mut<O, F: FnOnce(&mut FakeFrameCtx<SendMeta>) -> O>(
&mut self,
f: F,
) -> O;
}
impl<SendMeta> WithFakeFrameContext<SendMeta> for FakeFrameCtx<SendMeta> {
fn with_fake_frame_ctx_mut<O, F: FnOnce(&mut FakeFrameCtx<SendMeta>) -> O>(
&mut self,
f: F,
) -> O {
f(self)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use net_declare::net_mac;
use net_types::{UnicastAddr, Witness as _};
#[test]
fn frame_destination_from_dest() {
const LOCAL_ADDR: Mac = net_mac!("88:88:88:88:88:88");
assert_eq!(
FrameDestination::from_dest(
UnicastAddr::new(net_mac!("00:11:22:33:44:55")).unwrap().get(),
LOCAL_ADDR
),
FrameDestination::Individual { local: false }
);
assert_eq!(
FrameDestination::from_dest(LOCAL_ADDR, LOCAL_ADDR),
FrameDestination::Individual { local: true }
);
assert_eq!(
FrameDestination::from_dest(Mac::BROADCAST, LOCAL_ADDR),
FrameDestination::Broadcast,
);
assert_eq!(
FrameDestination::from_dest(
MulticastAddr::new(net_mac!("11:11:11:11:11:11")).unwrap().get(),
LOCAL_ADDR
),
FrameDestination::Multicast
);
}
}