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use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
use crate::routes::{EndpointBytes, RouteTable};
pub const IPV4_HEADER_MIN: usize = 20;
pub const IPV6_HEADER_LEN: usize = 40;
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum DropReason {
Malformed,
UnknownDestination,
SourceOutsideOwnPodCidr,
UnknownPeer,
SourceOutsidePeerPodCidr,
DestinationOutsideOwnPodCidr,
}
impl DropReason {
pub const ALL: [DropReason; 6] = [
DropReason::Malformed,
DropReason::UnknownDestination,
DropReason::SourceOutsideOwnPodCidr,
DropReason::UnknownPeer,
DropReason::SourceOutsidePeerPodCidr,
DropReason::DestinationOutsideOwnPodCidr,
];
pub fn label(self) -> &'static str {
match self {
DropReason::Malformed => "malformed",
DropReason::UnknownDestination => "unknown_destination",
DropReason::SourceOutsideOwnPodCidr => "source_outside_own_pod_cidr",
DropReason::UnknownPeer => "unknown_peer",
DropReason::SourceOutsidePeerPodCidr => "source_outside_peer_pod_cidr",
DropReason::DestinationOutsideOwnPodCidr => "destination_outside_own_pod_cidr",
}
}
pub fn index(self) -> usize {
DropReason::ALL
.iter()
.position(|reason| *reason == self)
.unwrap_or(0)
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Addresses {
pub src: IpAddr,
pub dst: IpAddr,
}
pub fn addresses(packet: &[u8]) -> Option<Addresses> {
let first = *packet.first()?;
match first >> 4 {
4 => {
if packet.len() < IPV4_HEADER_MIN {
return None;
}
let header_len = usize::from(first & 0x0f) * 4;
if header_len < IPV4_HEADER_MIN || packet.len() < header_len {
return None;
}
let src = Ipv4Addr::new(packet[12], packet[13], packet[14], packet[15]);
let dst = Ipv4Addr::new(packet[16], packet[17], packet[18], packet[19]);
Some(Addresses {
src: IpAddr::V4(src),
dst: IpAddr::V4(dst),
})
}
6 => {
if packet.len() < IPV6_HEADER_LEN {
return None;
}
let mut src = [0u8; 16];
let mut dst = [0u8; 16];
src.copy_from_slice(&packet[8..24]);
dst.copy_from_slice(&packet[24..40]);
Some(Addresses {
src: IpAddr::V6(Ipv6Addr::from(src)),
dst: IpAddr::V6(Ipv6Addr::from(dst)),
})
}
_ => None,
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Outbound {
Send(EndpointBytes),
Drop(DropReason),
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Inbound {
Deliver,
Drop(DropReason),
}
pub fn outbound(table: &RouteTable, packet: &[u8]) -> Outbound {
let Some(addrs) = addresses(packet) else {
return Outbound::Drop(DropReason::Malformed);
};
let Some(route) = table.lookup(addrs.dst) else {
return Outbound::Drop(DropReason::UnknownDestination);
};
if !table.owns(addrs.src) {
return Outbound::Drop(DropReason::SourceOutsideOwnPodCidr);
}
Outbound::Send(route.endpoint)
}
pub fn inbound(table: &RouteTable, from: &EndpointBytes, packet: &[u8]) -> Inbound {
let Some(addrs) = addresses(packet) else {
return Inbound::Drop(DropReason::Malformed);
};
if !table.knows_endpoint(from) {
return Inbound::Drop(DropReason::UnknownPeer);
}
if !table.endpoint_owns(from, addrs.src) {
return Inbound::Drop(DropReason::SourceOutsidePeerPodCidr);
}
if !table.owns(addrs.dst) {
return Inbound::Drop(DropReason::DestinationOutsideOwnPodCidr);
}
Inbound::Deliver
}
#[cfg(test)]
pub mod tests {
use super::*;
use crate::routes::RouteTable;
use crate::routes::tests::{identity, node};
pub fn ipv4_packet(src: [u8; 4], dst: [u8; 4]) -> Vec<u8> {
let mut packet = vec![0u8; 28];
packet[0] = 0x45;
packet[2..4].copy_from_slice(&28u16.to_be_bytes());
packet[8] = 64;
packet[9] = 1;
packet[12..16].copy_from_slice(&src);
packet[16..20].copy_from_slice(&dst);
packet
}
fn ipv6_packet(src: &str, dst: &str) -> Vec<u8> {
let mut packet = vec![0u8; 48];
packet[0] = 0x60;
packet[6] = 58;
packet[7] = 64;
let src: Ipv6Addr = src.parse().unwrap();
let dst: Ipv6Addr = dst.parse().unwrap();
packet[8..24].copy_from_slice(&src.octets());
packet[24..40].copy_from_slice(&dst.octets());
packet
}
fn table() -> (RouteTable, [u8; 32], [u8; 32]) {
let (me, b, c) = (identity(1), identity(2), identity(3));
let nodes = vec![
node("node-a", &["10.42.1.0/24", "fd00:42:1::/64"], Some(&me)),
node("node-b", &["10.42.2.0/24", "fd00:42:2::/64"], Some(&b)),
node("node-c", &["10.42.3.0/24"], Some(&c)),
];
(
RouteTable::compute("node-a", &me.public(), &nodes),
b.public(),
c.public(),
)
}
#[test]
fn source_and_destination_are_read_from_ipv4_and_ipv6_headers() {
let v4 = addresses(&ipv4_packet([10, 42, 1, 5], [10, 42, 2, 6])).unwrap();
assert_eq!(v4.src, "10.42.1.5".parse::<IpAddr>().unwrap());
assert_eq!(v4.dst, "10.42.2.6".parse::<IpAddr>().unwrap());
let v6 = addresses(&ipv6_packet("fd00:42:1::5", "fd00:42:2::6")).unwrap();
assert_eq!(v6.dst, "fd00:42:2::6".parse::<IpAddr>().unwrap());
}
#[test]
fn a_truncated_or_unknown_version_packet_is_malformed() {
assert!(addresses(&[]).is_none());
assert!(addresses(&[0x45, 0, 0]).is_none());
assert!(addresses(&[0x46; 20]).is_none());
assert!(addresses(&[0x60; 39]).is_none());
assert!(addresses(&[0x20; 60]).is_none());
let (table, _, _) = table();
assert_eq!(
outbound(&table, &[0x45, 0, 0]),
Outbound::Drop(DropReason::Malformed)
);
}
#[test]
fn a_packet_to_a_peer_pod_goes_to_that_peers_endpoint() {
let (table, b, c) = table();
assert_eq!(
outbound(&table, &ipv4_packet([10, 42, 1, 5], [10, 42, 2, 6])),
Outbound::Send(b)
);
assert_eq!(
outbound(&table, &ipv4_packet([10, 42, 1, 0], [10, 42, 3, 9])),
Outbound::Send(c)
);
assert_eq!(
outbound(&table, &ipv6_packet("fd00:42:1::5", "fd00:42:2::6")),
Outbound::Send(b)
);
}
#[test]
fn a_packet_for_an_unknown_destination_is_dropped() {
let (table, _, _) = table();
assert_eq!(
outbound(&table, &ipv4_packet([10, 42, 1, 5], [10, 42, 9, 6])),
Outbound::Drop(DropReason::UnknownDestination)
);
assert_eq!(
outbound(&table, &ipv4_packet([10, 42, 1, 5], [10, 42, 1, 6])),
Outbound::Drop(DropReason::UnknownDestination)
);
}
#[test]
fn a_packet_whose_source_is_not_this_nodes_pod_cidr_is_not_sent() {
let (table, _, _) = table();
assert_eq!(
outbound(&table, &ipv4_packet([10, 0, 2, 15], [10, 42, 2, 6])),
Outbound::Drop(DropReason::SourceOutsideOwnPodCidr)
);
}
#[test]
fn a_received_packet_from_a_peer_pod_to_one_of_ours_is_delivered() {
let (table, b, _) = table();
assert_eq!(
inbound(&table, &b, &ipv4_packet([10, 42, 2, 6], [10, 42, 1, 5])),
Inbound::Deliver
);
assert_eq!(
inbound(&table, &b, &ipv6_packet("fd00:42:2::6", "fd00:42:1::5")),
Inbound::Deliver
);
}
#[test]
fn a_received_packet_spoofing_another_peers_pods_is_dropped() {
let (table, b, _) = table();
assert_eq!(
inbound(&table, &b, &ipv4_packet([10, 42, 3, 6], [10, 42, 1, 5])),
Inbound::Drop(DropReason::SourceOutsidePeerPodCidr)
);
}
#[test]
fn a_received_packet_for_somewhere_other_than_our_pods_is_dropped() {
let (table, b, _) = table();
assert_eq!(
inbound(&table, &b, &ipv4_packet([10, 42, 2, 6], [10, 42, 3, 5])),
Inbound::Drop(DropReason::DestinationOutsideOwnPodCidr)
);
assert_eq!(
inbound(
&table,
&b,
&ipv4_packet([10, 42, 2, 6], [169, 254, 169, 254])
),
Inbound::Drop(DropReason::DestinationOutsideOwnPodCidr)
);
}
#[test]
fn a_received_packet_from_an_endpoint_with_no_route_is_dropped() {
let (table, _, _) = table();
let stranger = identity(9).public();
assert_eq!(
inbound(
&table,
&stranger,
&ipv4_packet([10, 42, 2, 6], [10, 42, 1, 5])
),
Inbound::Drop(DropReason::UnknownPeer)
);
}
}
