snap_dataplane/tunnel_gateway/
dispatcher.rs

1// Copyright 2026 Anapaya Systems
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//   http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14//! Dispatcher implementation for the tunnel gateway
15
16use std::net::SocketAddr;
17
18use ana_gotatun::packet::Packet;
19use sciparse::{core::view::View, packet::view::ScionPacketView};
20use tokio::sync::mpsc::{Receiver, Sender, channel, error::TrySendError};
21
22use crate::{
23    dispatcher::Dispatcher,
24    tunnel_gateway::{gateway::PacketPool, metrics::TunnelGatewayDispatcherMetrics},
25};
26
27const OUTBOUND_QUEUE_SIZE: usize = 1024;
28const BUFFER_POOL_INIT_SIZE: usize = 1024;
29
30/// The implementation of the tunnel gateway dispatcher.
31#[derive(Clone)]
32pub struct TunnelGatewayDispatcher {
33    metrics: TunnelGatewayDispatcherMetrics,
34    pool: PacketPool,
35    // The outbound queue contains the packets coming from the SCION network
36    // headed towards the endhosts. The socket address is parsed out from the
37    // packet and is redundant with the one indicated by the packet.
38    outbound_queue: Sender<(SocketAddr, Packet)>,
39}
40
41impl TunnelGatewayDispatcher {
42    /// Creates a pair of [TunnelGatewayDispatcher] and
43    /// [TunnelGatewayDispatcherReceiver]. The [TunnelGatewayDispatcher] is the
44    /// object that dispatches SCION packets coming from the SCION network
45    /// towards the endhosts. The second object of type
46    /// [TunnelGatewayDispatcherReceiver] is the receiving end which is given to
47    /// the actual tunnel gateway.
48    ///
49    /// The separation is done due to the circular dependency between the
50    /// different dispatchers.
51    pub fn new(metrics: TunnelGatewayDispatcherMetrics) -> (Self, TunnelGatewayDispatcherReceiver) {
52        let pool = ana_gotatun::packet::PacketBufPool::new(BUFFER_POOL_INIT_SIZE);
53        let (tx, rx) = channel(OUTBOUND_QUEUE_SIZE);
54        let myself = Self {
55            metrics,
56            pool: pool.clone(),
57            outbound_queue: tx,
58        };
59
60        let rx = TunnelGatewayDispatcherReceiver {
61            outbound_queue: rx,
62            pool,
63        };
64        (myself, rx)
65    }
66}
67
68impl Dispatcher for TunnelGatewayDispatcher {
69    fn try_dispatch(&self, packet: &ScionPacketView) {
70        let classification = match packet.classify() {
71            Ok(c) => c,
72            Err(e) => {
73                self.metrics.invalid_packets_errors.inc();
74                tracing::debug!(error=%e, "Failed to classify packet");
75                return;
76            }
77        };
78
79        let sock_addr = match classification
80            .dst_socket_addr()
81            .and_then(|a| a.socket_addr())
82        {
83            Some(addr) => addr,
84            None => {
85                self.metrics.invalid_packets_errors.inc();
86                tracing::debug!("Could not deduce destination socket address from packet");
87                return;
88            }
89        };
90
91        let raw_bytes = packet.as_bytes();
92        let mut pooled_packet = self.pool.get();
93        pooled_packet.as_mut()[..raw_bytes.len()].copy_from_slice(raw_bytes);
94        pooled_packet.truncate(raw_bytes.len());
95
96        match self.outbound_queue.try_send((sock_addr, pooled_packet)) {
97            Ok(_) => self.metrics.dispatch_queue_size.inc(),
98            Err(TrySendError::Closed(_)) => self.metrics.closed_dispatch_queue_errors.inc(),
99            Err(TrySendError::Full(_)) => self.metrics.full_dispatch_queue_errors.inc(),
100        }
101    }
102}
103
104/// This is the type that is plugged into the TunnelGateway.
105pub struct TunnelGatewayDispatcherReceiver {
106    pub(crate) pool: PacketPool,
107    pub(crate) outbound_queue: Receiver<(SocketAddr, Packet)>,
108}
snap_dataplane/tunnel_gateway/dispatcher.rs

snap_dataplane/tunnel_gateway/
dispatcher.rs
