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Add wire representations for SRv6 header as part of IPv6 Routing header #610

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Add wire representations for SRv6 header as part of IPv6 Routing header #610

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bc671b2
Add SRv6 header to IPv6 Routing header and repr structs
ngc0202 May 9, 2022
732cdf5
Merge branch 'master' into add-srv6-wire-repr
Nov 30, 2022
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222 changes: 219 additions & 3 deletions src/wire/ipv6routing.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use super::{Error, Result};
use core::fmt;
use core::{convert::TryInto, fmt};

use crate::wire::IpProtocol as Protocol;
use crate::wire::Ipv6Address as Address;
Expand All @@ -21,6 +21,10 @@ enum_with_unknown! {
///
/// See https://tools.ietf.org/html/rfc6554 for details.
Rpl = 3,
/// IPv6 Segment Routing Header (SRH)
///
/// See https://tools.ietf.org/html/rfc8754 for details.
Srh = 4,
/// RFC3692-style Experiment 1
///
/// See https://tools.ietf.org/html/rfc4727 for details.
Expand All @@ -41,6 +45,7 @@ impl fmt::Display for Type {
Type::Nimrod => write!(f, "Nimrod"),
Type::Type2 => write!(f, "Type2"),
Type::Rpl => write!(f, "Rpl"),
Type::Srh => write!(f, "Srh"),
Type::Experiment1 => write!(f, "Experiment1"),
Type::Experiment2 => write!(f, "Experiment2"),
Type::Reserved => write!(f, "Reserved"),
Expand Down Expand Up @@ -138,6 +143,56 @@ mod field {
let data = DATA(length_field);
8..data.end
}

// The SRv6 Segment Routing Header has the following format:
//
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Next Header | Hdr Ext Len | Routing Type | Segments Left |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Last Entry | Flags | Tag |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// | Segment List[0] (128-bit IPv6 address) |
// | |
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// | |
// | ... |
// | |
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// | Segment List[n] (128-bit IPv6 address) |
// | |
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// // //
// // Optional Type Length Value objects (variable) //
// // //
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

/// 8-bit field containing the Last Entry value
pub const LAST_ENTRY: usize = 4;

/// 8-bit field containing the Flags value
pub const FLAGS: usize = 5;

/// 16-bit field containing the Tag value
pub const TAG: Field = 6..8;

/// Variable-length field containing the segment list
pub const fn SEGMENTS(last_entry_field: u8) -> Field {
let bytes = 16 * (last_entry_field as usize) + 8;
8..bytes
}

/// Variable-length field containing the TLVs
pub const fn TLV(length_field: u8, last_entry_field: u8) -> Field {
let start = SEGMENTS(last_entry_field).end;
let end = DATA(length_field).end;
start..end
}
}

/// Core getter methods relevant to any routing type.
Expand Down Expand Up @@ -269,6 +324,55 @@ impl<T: AsRef<[u8]>> Header<T> {
}
}

/// Getter methods for the SRv6 Segment Routing Header type.
impl<T: AsRef<[u8]>> Header<T> {
/// Return the index of the last entry in the Segment List.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn last_entry(&self) -> u8 {
let data = self.buffer.as_ref();
data[field::LAST_ENTRY]
}

/// Return the 8-bit Segment Routing Header flags.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn flags(&self) -> u8 {
let data = self.buffer.as_ref();
data[field::FLAGS]
}

/// Return the segment routing tag.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn tag(&self) -> u16 {
let data = self.buffer.as_ref();
let slice = &data[field::TAG];
u16::from_be_bytes(slice.try_into().unwrap())
}

/// Return the SRv6 segment list.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn segment_list(&self) -> &[u8] {
let data = self.buffer.as_ref();
&data[field::SEGMENTS(self.last_entry())]
}

/// Return the type length value fields.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn tlv(&self) -> &[u8] {
let data = self.buffer.as_ref();
&data[field::TLV(self.header_len(), self.last_entry())]
}
}

/// Core setter methods relevant to any routing type.
impl<T: AsRef<[u8]> + AsMut<[u8]>> Header<T> {
/// Set the next header field.
Expand Down Expand Up @@ -382,6 +486,57 @@ impl<T: AsRef<[u8]> + AsMut<[u8]>> Header<T> {
}
}

/// Setter methods for the SRv6 Segment Routing Header type.
impl<T: AsRef<[u8]> + AsMut<[u8]>> Header<T> {
/// Set the index of the last entry in the Segment List.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn set_last_entry(&mut self, value: u8) {
let data = self.buffer.as_mut();
data[field::LAST_ENTRY] = value;
}

/// Set the 8-bit Segment Routing Header flags.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn set_flags(&mut self, value: u8) {
let data = self.buffer.as_mut();
data[field::FLAGS] = value;
}

/// Set the segment routing tag.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn set_tag(&mut self, value: u16) {
let data = self.buffer.as_mut();
let bytes = value.to_be_bytes();
data[field::TAG].copy_from_slice(&bytes);
}

/// Set the SRv6 segment list.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn set_segment_list(&mut self, value: &[u8]) {
let seg_field = field::SEGMENTS(self.last_entry());
let data = self.buffer.as_mut();
data[seg_field].copy_from_slice(value);
}

/// Set the type length value fields.
///
/// # Panics
/// This function may panic if this header is not the SRv6 Segment Routing Header type.
pub fn set_tlv(&mut self, value: &[u8]) {
let tlv_field = field::TLV(self.header_len(), self.last_entry());
let data = self.buffer.as_mut();
data[tlv_field].copy_from_slice(value);
}
}

impl<'a, T: AsRef<[u8]> + ?Sized> fmt::Display for Header<&'a T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match Repr::parse(self) {
Expand Down Expand Up @@ -426,6 +581,24 @@ pub enum Repr<'a> {
/// Vector of addresses, numbered 1 to `n`.
addresses: &'a [u8],
},
Srh {
/// The type of header immediately following the Routing header.
next_header: Protocol,
/// Length of the Routing header in 8-octet units, not including the first 8 octets.
length: u8,
/// Number of route segments remaining.
segments_left: u8,
/// Contains the index (zero based) of the last element of the Segment List
last_entry: u8,
/// Header flags (unused currently)
flags: u8,
/// Tag a packet as part of a class or group of packets
tag: u16,
/// 128-bit IPv6 addresses representing the nth segment in the Segment List
segment_list: &'a [u8],
/// Type Length Value fields
tlv: &'a [u8],
},
}

impl<'a> Repr<'a> {
Expand All @@ -450,7 +623,16 @@ impl<'a> Repr<'a> {
pad: header.pad(),
addresses: header.addresses(),
}),

Type::Srh => Ok(Repr::Srh {
next_header: header.next_header(),
length: header.header_len(),
segments_left: header.segments_left(),
last_entry: header.last_entry(),
flags: header.flags(),
tag: header.tag(),
segment_list: header.segment_list(),
tlv: header.tlv(),
}),
_ => Err(Error),
}
}
Expand All @@ -459,7 +641,9 @@ impl<'a> Repr<'a> {
/// representation.
pub const fn buffer_len(&self) -> usize {
match self {
&Repr::Rpl { length, .. } | &Repr::Type2 { length, .. } => field::DATA(length).end,
&Repr::Rpl { length, .. } | &Repr::Type2 { length, .. } | &Repr::Srh { length, .. } => {
field::DATA(length).end
}
}
}

Expand Down Expand Up @@ -498,6 +682,26 @@ impl<'a> Repr<'a> {
header.clear_reserved();
header.set_addresses(addresses);
}
Repr::Srh {
next_header,
length,
segments_left,
last_entry,
flags,
tag,
segment_list,
tlv,
} => {
header.set_next_header(next_header);
header.set_header_len(length);
header.set_routing_type(Type::Srh);
header.set_segments_left(segments_left);
header.set_last_entry(last_entry);
header.set_flags(flags);
header.set_tag(tag);
header.set_segment_list(segment_list);
header.set_tlv(tlv);
}
}
}
}
Expand Down Expand Up @@ -533,6 +737,18 @@ impl<'a> fmt::Display for Repr<'a> {
write!(f, "IPv6 Routing next_hdr={} length={} type={} seg_left={} cmpr_i={} cmpr_e={} pad={}",
next_header, length, Type::Rpl, segments_left, cmpr_i, cmpr_e, pad)
}
Repr::Srh {
next_header,
length,
segments_left,
last_entry,
flags,
tag,
..
} => {
write!(f, "IPv6 Routing next_hdr={} length={} type={} seg_left={} last_entry={} flags={} tag={}",
next_header, length, Type::Srh, segments_left, last_entry, flags, tag)
}
}
}
}
Expand Down