Impl mod destination_unreachable (#128)

Co-authored-by: Adenylatcyclase <[email protected]>
Co-authored-by: Karthik Ravikanti <[email protected]>

Author: plumenator

core/src/packets/icmp/v6/destination_unreachable.rs

@@ -0,0 +1,218 @@
+/*
+* Copyright 2019 Comcast Cable Communications Management, LLC
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*
+* SPDX-License-Identifier: Apache-2.0
+*/
+
+use crate::packets::icmp::v6::{Icmpv6, Icmpv6Message, Icmpv6Packet, Icmpv6Type, Icmpv6Types};
+use crate::packets::ip::v6::{Ipv6Packet, IPV6_MIN_MTU};
+use crate::packets::types::u32be;
+use crate::packets::{Internal, Packet};
+use crate::SizeOf;
+use anyhow::Result;
+use std::fmt;
+use std::ptr::NonNull;
+
+/// Destination Unreachable Message defined in [IETF RFC 4443].
+///
+/// ```
+/// 0                   1                   2                   3
+/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+/// |     Type      |     Code      |          Checksum             |
+/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+/// |                             Unused                            |
+/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+/// |                    As much of invoking packet                 |
+/// +               as possible without the ICMPv6 packet           +
+/// |               exceeding the minimum IPv6 MTU [IPv6]           |
+/// ```
+///
+/// [IETF RFC 4443]: https://tools.ietf.org/html/rfc4443#section-3.1
+#[derive(Icmpv6Packet)]
+pub struct DestinationUnreachable<E: Ipv6Packet> {
+    icmp: Icmpv6<E>,
+    body: NonNull<DestinationUnreachableBody>,
+}
+
+impl<E: Ipv6Packet> DestinationUnreachable<E> {
+    /// Returns the invoking packet as a `u8` slice.
+    #[inline]
+    pub fn data(&self) -> &[u8] {
+        let offset = self.payload_offset() + DestinationUnreachableBody::size_of();
+        let len = self.payload_len() - DestinationUnreachableBody::size_of();
+
+        if let Ok(data) = self.icmp().mbuf().read_data_slice(offset, len) {
+            unsafe { &*data.as_ptr() }
+        } else {
+            &[]
+        }
+    }
+}
+
+impl<E: Ipv6Packet> fmt::Debug for DestinationUnreachable<E> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("DestinationUnreachable")
+            .field("type", &format!("{}", self.msg_type()))
+            .field("code", &self.code())
+            .field("checksum", &format!("0x{:04x}", self.checksum()))
+            .field("$offset", &self.offset())
+            .field("$len", &self.len())
+            .field("$header_len", &self.header_len())
+            .finish()
+    }
+}
+
+impl<E: Ipv6Packet> Icmpv6Message for DestinationUnreachable<E> {
+    type Envelope = E;
+
+    #[inline]
+    fn msg_type() -> Icmpv6Type {
+        Icmpv6Types::DestinationUnreachable
+    }
+
+    #[inline]
+    fn icmp(&self) -> &Icmpv6<Self::Envelope> {
+        &self.icmp
+    }
+
+    #[inline]
+    fn icmp_mut(&mut self) -> &mut Icmpv6<Self::Envelope> {
+        &mut self.icmp
+    }
+
+    #[inline]
+    fn into_icmp(self) -> Icmpv6<Self::Envelope> {
+        self.icmp
+    }
+
+    #[inline]
+    unsafe fn clone(&self, internal: Internal) -> Self {
+        DestinationUnreachable {
+            icmp: self.icmp.clone(internal),
+            body: self.body,
+        }
+    }
+
+    /// Parses the ICMPv6 packet's payload as destination unreachable.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the payload does not have sufficient data for
+    /// the destination unreachable message body.
+    #[inline]
+    fn try_parse(icmp: Icmpv6<Self::Envelope>, _internal: Internal) -> Result<Self> {
+        let mbuf = icmp.mbuf();
+        let offset = icmp.payload_offset();
+        let body = mbuf.read_data(offset)?;
+
+        Ok(DestinationUnreachable { icmp, body })
+    }
+
+    /// Prepends a new destination unreachable message to the beginning of the ICMPv6's
+    /// payload.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the buffer does not have enough free space.
+    #[inline]
+    fn try_push(mut icmp: Icmpv6<Self::Envelope>, _internal: Internal) -> Result<Self> {
+        let offset = icmp.payload_offset();
+        let mbuf = icmp.mbuf_mut();
+
+        mbuf.extend(offset, DestinationUnreachableBody::size_of())?;
+        let body = mbuf.write_data(offset, &DestinationUnreachableBody::default())?;
+
+        Ok(DestinationUnreachable { icmp, body })
+    }
+
+    /// Reconciles the derivable header fields against the changes made to
+    /// the packet.
+    ///
+    /// * the whole packet is truncated so it doesn't exceed the [minimum
+    /// IPv6 MTU].
+    /// * [`checksum`] is computed based on the pseudo-header and the
+    /// `DestinationUnreachable` message.
+    ///
+    /// [minimum IPv6 MTU]: IPV6_MIN_MTU
+    /// [`checksum`]: Icmpv6::checksum
+    #[inline]
+    fn reconcile(&mut self) {
+        let _ = self.envelope_mut().truncate(IPV6_MIN_MTU);
+        self.icmp_mut().compute_checksum();
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default, SizeOf)]
+#[repr(C, packed)]
+struct DestinationUnreachableBody {
+    _unused: u32be,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::packets::ip::v6::Ipv6;
+    use crate::packets::Ethernet;
+    use crate::testils::byte_arrays::IPV6_TCP_PACKET;
+    use crate::Mbuf;
+
+    #[test]
+    fn size_of_destination_unreachable_body() {
+        assert_eq!(4, DestinationUnreachableBody::size_of());
+    }
+
+    #[capsule::test]
+    fn push_and_set_destination_unreachable() {
+        let packet = Mbuf::from_bytes(&IPV6_TCP_PACKET).unwrap();
+        let ethernet = packet.parse::<Ethernet>().unwrap();
+        let ipv6 = ethernet.parse::<Ipv6>().unwrap();
+        let tcp_len = ipv6.payload_len();
+
+        let mut unreachable = ipv6.push::<DestinationUnreachable<Ipv6>>().unwrap();
+
+        assert_eq!(4, unreachable.header_len());
+        assert_eq!(
+            DestinationUnreachableBody::size_of() + tcp_len,
+            unreachable.payload_len()
+        );
+        assert_eq!(Icmpv6Types::DestinationUnreachable, unreachable.msg_type());
+        assert_eq!(0, unreachable.code());
+        assert_eq!(tcp_len, unreachable.data().len());
+
+        unreachable.set_code(1);
+        assert_eq!(1, unreachable.code());
+
+        unreachable.reconcile_all();
+        assert!(unreachable.checksum() != 0);
+    }
+
+    #[capsule::test]
+    fn truncate_to_ipv6_min_mtu() {
+        // starts with a buffer larger than min MTU.
+        let packet = Mbuf::from_bytes(&[42; 1600]).unwrap();
+        let ethernet = packet.push::<Ethernet>().unwrap();
+        let ipv6 = ethernet.push::<Ipv6>().unwrap();
+
+        // the max packet len is MTU + Ethernet header
+        let max_len = IPV6_MIN_MTU + 14;
+
+        let mut unreachable = ipv6.push::<DestinationUnreachable<Ipv6>>().unwrap();
+        assert!(unreachable.mbuf().data_len() > max_len);
+
+        unreachable.reconcile_all();
+        assert_eq!(max_len, unreachable.mbuf().data_len());
+    }
+}

core/src/packets/icmp/v6/mod.rs

@@ -18,12 +18,14 @@
 
 //! Internet Control Message Protocol for IPv6.
 
+mod destination_unreachable;
 mod echo_reply;
 mod echo_request;
 pub mod ndp;
 mod time_exceeded;
 mod too_big;
 
+pub use self::destination_unreachable::*;
 pub use self::echo_reply::*;
 pub use self::echo_request::*;
 pub use self::time_exceeded::*;
@@ -293,6 +295,11 @@ pub mod Icmpv6Types {
     /// [Time Exceeded]: crate::packets::icmp::v6::TimeExceeded
     pub const TimeExceeded: Icmpv6Type = Icmpv6Type(3);
 
+    /// Message type for [Destination Unreachable].
+    ///
+    /// [Destination Unreachable]: crate::packets::icmp::v6::DestinationUnreachable
+    pub const DestinationUnreachable: Icmpv6Type = Icmpv6Type(1);
+
     /// Message type for [Echo Request].
     ///
     /// [Echo Request]: crate::packets::icmp::v6::EchoRequest