feature: Implement open message and tests

README.md

@@ -1,6 +1,6 @@
 # BGP
 
-This project is an implementation of the Border Gateway Protocol and associated functionality required to run an Autonomous System.
+The `bgp` crate is an implementation of the Border Gateway Protocol, which is used to exchange routing and control plane information between Autonomous Systms.
 
 The aim of this project is to provide a modern, high performance, secure and programatic and customizable software package that can be useful to network operators, researchers, and people interested in Internet.
 
@@ -8,4 +8,19 @@ The aim of this project is to provide a modern, high performance, secure and pro
 
 The project is currently being rewritten from scratch to be more modular and maintainable, as well as to fix deeper issues with the previous implementation.
 
-Warning: This is currently a work in progress and not ready for use.
+⚠️ Warning: This is currently a work in progress and not ready for use.
+
+### 🛣️ Roadmap to v1.0
+
+We aim for the 1.0 release to be functional and stable to operate peering sessions, and to install routes in the Linux Kernel.
+
+* ☐ Implement basic parsers for the fundamental types required
+  * ✅ Path Attributes from RFC4271
+  * ☐ Open message
+    * ☐ Capabilities from RFC4271
+  * ☐ Update message
+  * ☐ Notification message
+* ☐ Implement connection logic to establish sessions with peers
+* ☐ Implement an efficient data structure for storing prefixes (e.g. Poptrie)
+* ☐ Filtering for peer RIB in / out
+* ☐ Main / auxillary RIBs for exchanging routes between peers

crates/packet/src/constants.rs

@@ -4,7 +4,7 @@ use eyre::bail;
 use serde_repr::{Deserialize_repr, Serialize_repr};
 
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, Serialize_repr, Deserialize_repr)]
-#[repr(u8)]
+#[repr(u16)]
 pub enum AddressFamilyId {
     Ipv4 = 1,
     Ipv6 = 2,
@@ -57,6 +57,16 @@ impl TryFrom<u8> for SubsequentAfi {
     }
 }
 
+/// The implementation try_from for u16 just reuses the u8 implementation since
+/// we don't have any cases where the SAFI is longer than u8::MAX yet.
+impl TryFrom<u16> for SubsequentAfi {
+    type Error = eyre::Error;
+
+    fn try_from(value: u16) -> Result<Self, Self::Error> {
+        TryFrom::<u8>::try_from(value as u8)
+    }
+}
+
 impl Display for SubsequentAfi {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {

crates/packet/src/lib.rs

@@ -2,4 +2,5 @@ pub mod constants;
 pub mod errors;
 pub mod ip_prefix;
 pub mod message;
+pub mod open;
 pub mod parser;

crates/packet/src/message.rs

@@ -21,6 +21,7 @@ use strum::EnumDiscriminants;
 use crate::constants::AddressFamilyId;
 use crate::constants::SubsequentAfi;
 use crate::ip_prefix::IpPrefix;
+use crate::open::OpenMessage;
 use crate::parser::BgpParserError;
 use crate::parser::ParserContext;
 
@@ -32,82 +33,43 @@ pub const AS_TRANS: u16 = 23456;
 pub const BGP4_VERSION: u8 = 4;
 
 /// Message represents the top-level messages in the BGP protocol.
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Serialize, Deserialize, EnumDiscriminants)]
+#[repr(u8)]
 pub enum Message {
-    Open(OpenMessage),
-    Update(UpdateMessage),
-    Notification(NotificationMessage),
-    KeepAlive,
-    // RouteRefresh(RouteRefreshMessage),
-}
-
-impl Message {}
-
-#[derive(Debug, Serialize, Deserialize)]
-pub enum MessageType {
-    /// BGP Open message (RFC 4271).
-    Open = 1,
-    /// BGP Update message (RFC 4271).
-    Update = 2,
-    /// BGP Notification message (RFC 4275).
-    Notification = 3,
-    /// BGP KeepAlive message (RFC 4271).
+    Open(OpenMessage) = 1,
+    Update(UpdateMessage) = 2,
+    Notification(NotificationMessage) = 3,
     KeepAlive = 4,
     /// BGP Route Refresh message (RFC 2918).
     RouteRefresh = 5,
 }
 
-#[derive(Debug, Serialize, Deserialize)]
-pub struct OpenMessage {
-    /// Version of the BGP protocol in use.
-    pub version: u8,
-    /// AS Number of the BGP speaker, or AS_TRANS if using 4 byte ASN.
-    pub asn: u16,
-    /// Hold time parameter in seconds.
-    pub hold_time: u16,
-    /// Global identifier of the BGP speaker.
-    pub identifier: Ipv4Addr,
-    /// Options.
-    pub options: Vec<OpenOption>,
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-pub enum OpenOption {
-    Capabilities(Vec<Capability>),
-    /// BGP extended open options length (RFC 9072).
-    ExtendedLength(u32),
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-pub enum Capability {
-    /// MultiProtocol Extension (RFC 2858).
-    MultiProtocol { afi: u16, safi: u8 },
-    /// Route Refresh capability (RFC 2918).
-    RouteRefresh {},
-    /// Outbound Route Filtering (RFC 5291).
-    /// https://datatracker.ietf.org/doc/html/rfc5291
-    OutboundRouteFilter {},
-    /// Extended Next Hop encoding (RFC 8950).
-    ExtendedNextHop {},
-    /// Extended Message (RFC 8654).
-    ExtendedMessage {},
-    /// BGPSec (RFC 8205).
-    BgpSec {},
-    /// Multiple labels compatibility (RFC 8277).
-    MultiLabelCompat {},
-    /// Graceful restart capability (RFC 4724).
-    GracefulRestart {},
-    /// Four Byte ASN (RFC 4274).
-    FourByteAsn { asn: u32 },
-    /// Additional Path (RFC 7911).
-    AddPath {},
-    /// Enhanced Route Refresh (RFC 7313).
-    EnhancedRouteRefresh {},
-}
+impl Message {}
 
 /// Represents a BGP Update message.
 #[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct UpdateMessage {}
+pub struct UpdateMessage {
+    pub withdrawn_routes: Vec<IpPrefix>,
+    pub path_attributes: Vec<PathAttribute>,
+    pub announced_routes: Vec<IpPrefix>,
+}
+
+impl UpdateMessage {
+    pub fn from_wire<'a>(
+        _ctx: &ParserContext,
+        _buf: &'a [u8],
+    ) -> IResult<&'a [u8], Self, BgpParserError<&'a [u8]>> {
+        todo!();
+    }
+
+    pub fn to_wire(&self, _ctx: &ParserContext, _out: &mut BytesMut) -> Result<()> {
+        todo!()
+    }
+
+    pub fn wire_len(&self, _ctx: &ParserContext) -> Result<u16> {
+        todo!()
+    }
+}
 
 bitfield! {
     #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]

crates/packet/src/open.rs

@@ -0,0 +1,980 @@
+use std::net::Ipv4Addr;
+
+use bitfield::bitfield;
+use bytes::{BufMut, BytesMut};
+use eyre::{Result, bail, eyre};
+use nom::{
+    Err::Failure,
+    IResult, Parser,
+    combinator::peek,
+    number::complete::{be_u8, be_u16, be_u24, be_u32},
+};
+use serde::{Deserialize, Serialize};
+use strum::EnumDiscriminants;
+
+use crate::{
+    constants::{AddressFamilyId, SubsequentAfi},
+    parser::{BgpParserError, ParserContext, ProtocolErrorValues},
+};
+
+macro_rules! fail {
+    ( $($arg:expr),* $(,)? ) => {
+        Failure(BgpParserError::Eyre(eyre!($($arg),*)))
+    };
+}
+
+/// Contains messages related to the BGP Open message,
+/// i.e. the Open message itself and options / capabilities.
+#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
+pub struct OpenMessage {
+    /// Version of the BGP protocol in use.
+    pub version: u8,
+    /// AS Number of the BGP speaker, or AS_TRANS if using 4 byte ASN.
+    pub asn: u16,
+    /// Hold time parameter in seconds.
+    pub hold_time: u16,
+    /// Global identifier of the BGP speaker.
+    pub identifier: Ipv4Addr,
+    /// Options.
+    pub options: Vec<OpenOption>,
+}
+
+impl OpenMessage {
+    /// The from_wire implementation parses a BGP Open message from a buffer
+    /// containing the payload of the open message (i.e. without the BGP header / type / length)
+    /// and the buf passed in must contain only the open message.
+    pub fn from_wire<'a>(
+        ctx: &ParserContext,
+        buf: &'a [u8],
+    ) -> IResult<&'a [u8], Self, BgpParserError<&'a [u8]>> {
+        let (buf, version) = be_u8(buf)?;
+        if version != 4 {
+            return Err(Failure(BgpParserError::ProtocolError(
+                ProtocolErrorValues::UnknownOpenOption(version),
+            )));
+        }
+
+        let (buf, asn) = be_u16(buf)?;
+        let (buf, hold_time) = be_u16(buf)?;
+        let (buf, identifier) = be_u32(buf)?;
+
+        // RFC 9072: Extended Open Options length.
+        // To encode a capabilities length greater than 255 the packet structure
+        // is prefixed with the extended length option (255), a length of 255,
+        // and then a u16 containing the payload option.
+        let (buf, opt_len) = be_u8(buf)?;
+        let (_, inner) = peek(be_u8).parse(buf)?;
+
+        let (buf, opt_len) = if inner == 255 {
+            let (buf, _) = be_u8(buf)?; // Skip past the inner type.
+            be_u16(buf)?
+        } else {
+            (buf, opt_len as u16)
+        };
+
+        let (buf, opt_buf) = nom::bytes::take(opt_len).parse(buf)?;
+        let (opt_buf, options) =
+            nom::multi::many0(|buf| OpenOption::from_wire(ctx, buf)).parse(opt_buf)?;
+
+        if !opt_buf.is_empty() {
+            return Err(fail!(
+                "Leftover bytes after parsing open options: {:x?}",
+                opt_buf
+            ));
+        }
+
+        Ok((
+            buf,
+            Self {
+                version,
+                asn,
+                hold_time,
+                identifier: Ipv4Addr::from(identifier),
+                options,
+            },
+        ))
+    }
+
+    pub fn to_wire(&self, ctx: &ParserContext, out: &mut BytesMut) -> Result<()> {
+        out.put_u8(self.version);
+        out.put_u16(self.asn);
+        out.put_u16(self.hold_time);
+        out.put_u32(self.identifier.into());
+
+        // RFC 9072: Depending on whether the options fit in < 255 bytes
+        // we encode the length accordingly.
+        let opt_len = self
+            .options
+            .iter()
+            .map(|o| o.wire_len(ctx))
+            .sum::<Result<u16>>()?;
+        if opt_len > u8::MAX as u16 {
+            out.put_u8(0xff); // Set length to 255 as per RFC 9072.
+            out.put_u8(0xff); // Open option type for Ext length.
+            out.put_u16(opt_len);
+        } else {
+            out.put_u8(opt_len as u8);
+        }
+
+        for option in &self.options {
+            option.to_wire(ctx, out)?;
+        }
+
+        Ok(())
+    }
+
+    pub fn wire_len(&self, ctx: &ParserContext) -> Result<u16> {
+        let mut total = 10;
+        let opt_len = self
+            .options
+            .iter()
+            .map(|o| o.wire_len(ctx))
+            .sum::<Result<u16>>()?;
+        if opt_len > u8::MAX as u16 {
+            total += opt_len + 3; // 1+2 bytes extra for the type + extended length.
+        } else {
+            total += opt_len;
+        }
+        Ok(total)
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize, EnumDiscriminants, PartialEq, Eq)]
+#[repr(u8)]
+pub enum OpenOption {
+    Capabilities(Vec<Capability>) = 2,
+}
+
+impl OpenOption {
+    pub fn from_wire<'a>(
+        ctx: &ParserContext,
+        buf: &'a [u8],
+    ) -> IResult<&'a [u8], Self, BgpParserError<&'a [u8]>> {
+        let (buf, type_code) = be_u8(buf)?;
+        let (buf, length) = be_u8(buf)?;
+
+        let (buf, payload) = nom::bytes::take(length).parse(buf)?;
+
+        match type_code {
+            v if v == OpenOptionDiscriminants::Capabilities as u8 => {
+                let (payload_consumed, (capabilities, _eof)) = nom::multi::many_till(
+                    |buf| Capability::from_wire(ctx, buf),
+                    nom::combinator::eof,
+                )
+                .parse(payload)?;
+
+                if !payload_consumed.is_empty() {
+                    return Err(fail!(
+                        "Leftover bytes when parsing BGP capabilities: {:x?}",
+                        payload_consumed
+                    ));
+                }
+                Ok((buf, Self::Capabilities(capabilities)))
+            }
+            other => {
+                return Err(Failure(BgpParserError::ProtocolError(
+                    ProtocolErrorValues::UnknownOpenOption(other),
+                )));
+            }
+        }
+    }
+
+    pub fn to_wire(&self, ctx: &ParserContext, out: &mut BytesMut) -> Result<()> {
+        match self {
+            OpenOption::Capabilities(items) => {
+                let cap_len = items.iter().map(|i| i.wire_len(ctx)).sum::<Result<u16>>()?;
+                if cap_len > u8::MAX as u16 {
+                    bail!("Cannot write Capabilities with more than u8::MAX length");
+                }
+                out.put_u8(OpenOptionDiscriminants::Capabilities as u8);
+                out.put_u8(cap_len as u8);
+                for item in items {
+                    item.to_wire(ctx, out)?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    pub fn wire_len(&self, ctx: &ParserContext) -> Result<u16> {
+        match self {
+            OpenOption::Capabilities(items) => items
+                .iter()
+                .map(|i| i.wire_len(ctx))
+                .sum::<Result<u16>>()
+                .map(|v| v + 2),
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize, EnumDiscriminants, PartialEq, Eq)]
+#[repr(u8)]
+pub enum Capability {
+    /// MultiProtocol Extension (RFC 2858).
+    MultiProtocol {
+        afi: AddressFamilyId,
+        safi: SubsequentAfi,
+    } = 1,
+    /// Route Refresh capability (RFC 2918).
+    RouteRefresh = 2,
+    /// Outbound Route Filtering (RFC 5291).
+    /// https://datatracker.ietf.org/doc/html/rfc5291
+    OutboundRouteFilter {
+        afi: AddressFamilyId,
+        safi: SubsequentAfi,
+        orfs: Vec<OutboundRouteFilterEntry>,
+    } = 3,
+    /// Extended Next Hop encoding (RFC 8950).
+    ExtendedNextHop {
+        entries: Vec<ExtendedNextHop>,
+    } = 5,
+    /// Extended Message (RFC 8654).
+    ExtendedMessage = 6,
+    /// BGPSec (RFC 8205).
+    BgpSec {
+        header: BgpSecHeader,
+        afi: AddressFamilyId,
+    } = 7,
+    /// Multiple labels compatibility (RFC 8277).
+    MultiLabelCompat {} = 8,
+    BgpRole {
+        role: BgpRole,
+    } = 9,
+    /// Graceful restart capability (RFC 4724).
+    GracefulRestart {
+        /// When set to true it means that the BGP speaker has just restarted
+        /// and the peer must not wait for the End of RIB marker from the
+        /// speaker before advertising routing information to the speaker.
+        restart_state: bool,
+        /// This is the estimated time (in seconds) it will take for the
+        /// BGP session to be re-established after a restart.  This can be
+        /// used to speed up routing convergence by its peer in case that
+        /// the BGP speaker does not come back after a restart.
+        restart_time: u16,
+        /// The AFI and SAFI, taken in combination, indicate that Graceful
+        /// Restart is supported for routes that are advertised with the
+        /// same AFI and SAFI.  Routes may be explicitly associated with a
+        /// particular AFI and SAFI using the encoding of [BGP-MP] or
+        /// implicitly associated with <AFI=IPv4, SAFI=Unicast> if using
+        /// the encoding of [BGP-4].
+        entries: Vec<GracefulRestartEntry>,
+    } = 64,
+    /// Four Byte ASN (RFC 4274).
+    FourByteAsn {
+        asn: u32,
+    } = 65,
+    /// Additional Path (RFC 7911).
+    AddPath {
+        afi: AddressFamilyId,
+        safi: SubsequentAfi,
+        send_recv: AddPathSendRecv,
+    } = 69,
+    /// Enhanced Route Refresh (RFC 7313).
+    EnhancedRouteRefresh = 70,
+    /// Long Lived Graceful Restart (RFC 9494).
+    LongLivedGracefulRestart(Vec<LongLivedGracefulRestart>) = 71,
+    /// Unknown Capability encapsulates any capabilities that we don't know about.
+    UnknownCapability {
+        type_code: u8,
+        length: u8,
+        value: Vec<u8>,
+    },
+}
+
+impl Capability {
+    fn discriminant(&self) -> u8 {
+        match self {
+            Capability::MultiProtocol { .. } => CapabilityDiscriminants::MultiProtocol as u8,
+            Capability::RouteRefresh => CapabilityDiscriminants::RouteRefresh as u8,
+            Capability::OutboundRouteFilter { .. } => {
+                CapabilityDiscriminants::OutboundRouteFilter as u8
+            }
+            Capability::ExtendedNextHop { .. } => CapabilityDiscriminants::ExtendedNextHop as u8,
+            Capability::ExtendedMessage => CapabilityDiscriminants::ExtendedMessage as u8,
+            Capability::BgpSec { .. } => CapabilityDiscriminants::BgpSec as u8,
+            Capability::MultiLabelCompat {} => CapabilityDiscriminants::MultiLabelCompat as u8,
+            Capability::BgpRole { .. } => CapabilityDiscriminants::BgpRole as u8,
+            Capability::GracefulRestart { .. } => CapabilityDiscriminants::GracefulRestart as u8,
+            Capability::FourByteAsn { .. } => CapabilityDiscriminants::FourByteAsn as u8,
+            Capability::AddPath { .. } => CapabilityDiscriminants::AddPath as u8,
+            Capability::EnhancedRouteRefresh => CapabilityDiscriminants::EnhancedRouteRefresh as u8,
+            Capability::LongLivedGracefulRestart(_) => {
+                CapabilityDiscriminants::LongLivedGracefulRestart as u8
+            }
+            Capability::UnknownCapability { type_code, .. } => *type_code,
+        }
+    }
+    /// `from_wire` parses a Capability message.
+    pub fn from_wire<'a>(
+        _ctx: &ParserContext,
+        buf: &'a [u8],
+    ) -> IResult<&'a [u8], Self, BgpParserError<&'a [u8]>> {
+        let (buf, typ) = be_u8(buf)?;
+        let (buf, len) = be_u8(buf)?;
+        let (buf, cap_buf) = nom::bytes::take(len).parse(buf)?;
+        macro_rules! require_empty {
+            ($buf:expr, $cap_type:expr) => {
+                if !buf.is_empty() {
+                    return Err(nom::Err::Failure(BgpParserError::Eyre(eyre!(
+                        "Unexpected leftover bytes {:x?} while parsing {} capability",
+                        $buf,
+                        $cap_type
+                    ))));
+                }
+            };
+        }
+        match typ {
+            v if v == CapabilityDiscriminants::MultiProtocol as u8 => {
+                // MultiProtocol capability consists of an (AFI, SAFI).
+                let (cap_buf, afi) = be_u16(cap_buf)?;
+                let (cap_buf, _) = be_u8(cap_buf)?;
+                let (cap_buf, safi) = be_u8(cap_buf)?;
+                require_empty!(cap_buf, "MultiProtocol");
+                let afi = AddressFamilyId::try_from(afi).map_err(|e| fail!("{}", e))?;
+                let safi = SubsequentAfi::try_from(safi).map_err(|e| fail!("{}", e))?;
+                Ok((buf, Self::MultiProtocol { afi, safi }))
+            }
+            v if v == CapabilityDiscriminants::RouteRefresh as u8 => {
+                require_empty!(cap_buf, "RouteRefresh");
+                Ok((buf, Self::RouteRefresh))
+            }
+            v if v == CapabilityDiscriminants::OutboundRouteFilter as u8 => {
+                let (cap_buf, afi) = be_u16(cap_buf)?;
+                let (cap_buf, _) = be_u8(cap_buf)?; // Move past reverved byte.
+                let (cap_buf, safi) = be_u8(cap_buf)?;
+                let afi = AddressFamilyId::try_from(afi).map_err(|e| fail!("{}", e))?;
+                let safi = SubsequentAfi::try_from(safi).map_err(|e| fail!("{}", e))?;
+
+                let (cap_buf, _num_orfs) = be_u8(cap_buf)?;
+
+                let parse_orf = |buf: &'a [u8]| -> IResult<
+                    &'a [u8],
+                    OutboundRouteFilterEntry,
+                    BgpParserError<&'a [u8]>,
+                > {
+                    let (buf, orf_type) = be_u8(buf)?;
+                    let (buf, send_recv) = be_u8(buf)?;
+                    let orf_type = OrfType::from(orf_type);
+                    let send_recv = OrfSendRecv::try_from(send_recv)
+                        .map_err(|e| fail!("Failed to parse ORF send/recv: {}", e))?;
+
+                    Ok((
+                        buf,
+                        OutboundRouteFilterEntry {
+                            r#type: orf_type,
+                            send_recv,
+                        },
+                    ))
+                };
+
+                let (cap_buf, orfs) = nom::multi::many0(parse_orf).parse(cap_buf)?;
+                require_empty!(cap_buf, "OutboundRouteFilter");
+
+                Ok((buf, Self::OutboundRouteFilter { afi, safi, orfs }))
+            }
+            v if v == CapabilityDiscriminants::ExtendedNextHop as u8 => {
+                // parse_enh parses a single extended nexthop entry.
+                let parse_enh = |buf: &'a [u8]| -> IResult<
+                    &'a [u8],
+                    ExtendedNextHop,
+                    BgpParserError<&'a [u8]>,
+                > {
+                    let (buf, afi) = be_u16(buf)?;
+                    let (buf, safi) = be_u16(buf)?;
+                    let (buf, nh_afi) = be_u16(buf)?;
+                    let afi = AddressFamilyId::try_from(afi).map_err(|e| fail!("{}", e))?;
+                    let safi = SubsequentAfi::try_from(safi).map_err(|e| fail!("{}", e))?;
+                    let nh_afi = AddressFamilyId::try_from(nh_afi).map_err(|e| fail!("{}", e))?;
+                    Ok((buf, ExtendedNextHop { afi, safi, nh_afi }))
+                };
+                let (cap_buf, entries) = nom::multi::many1(parse_enh).parse(cap_buf)?;
+                require_empty!(cap_buf, "ExtendedNextHop");
+
+                Ok((cap_buf, Self::ExtendedNextHop { entries }))
+            }
+            v if v == CapabilityDiscriminants::ExtendedMessage as u8 => {
+                require_empty!(cap_buf, "ExtendedMessage");
+                Ok((cap_buf, Self::ExtendedMessage))
+            }
+            v if v == CapabilityDiscriminants::BgpSec as u8 => {
+                let (cap_buf, header) = be_u8(cap_buf)?;
+                let (cap_buf, afi) = be_u16(cap_buf)?;
+                let afi = AddressFamilyId::try_from(afi).map_err(|e| fail!("{}", e))?;
+                require_empty!(cap_buf, "BgpSec");
+                Ok((
+                    cap_buf,
+                    Self::BgpSec {
+                        header: BgpSecHeader(header),
+                        afi,
+                    },
+                ))
+            }
+            v if v == CapabilityDiscriminants::MultiLabelCompat as u8 => {
+                todo!()
+            }
+            v if v == CapabilityDiscriminants::BgpRole as u8 => {
+                let (cap_buf, role) = be_u8(cap_buf)?;
+                let role = BgpRole::try_from(role).map_err(|e| fail!("{}", e))?;
+                require_empty!(cap_buf, "BgpRole");
+                Ok((cap_buf, Self::BgpRole { role }))
+            }
+            v if v == CapabilityDiscriminants::GracefulRestart as u8 => {
+                // flags_restart_time is: (4 bits: restart flags, 12 bits: restart time (s)).
+                let (cap_buf, flags_restart_time) = be_u16(cap_buf)?;
+                let restart_state = ((1 << 15) & flags_restart_time) != 0;
+                let restart_time = flags_restart_time & 0xfff;
+                let parse_entry = |buf: &'a [u8]| -> IResult<
+                    &'a [u8],
+                    GracefulRestartEntry,
+                    BgpParserError<&'a [u8]>,
+                > {
+                    let (buf, afi) = be_u16(buf)?;
+                    let (buf, safi) = be_u8(buf)?;
+                    let (buf, flags) = be_u8(buf)?;
+                    let afi = AddressFamilyId::try_from(afi).map_err(|e| fail!("{}", e))?;
+                    let safi = SubsequentAfi::try_from(safi).map_err(|e| fail!("{}", e))?;
+                    Ok((
+                        buf,
+                        GracefulRestartEntry {
+                            afi,
+                            safi,
+                            preserve_forwarding: (flags & (1 << 7)) != 0,
+                        },
+                    ))
+                };
+                let (cap_buf, entries) = nom::multi::many0(parse_entry).parse(cap_buf)?;
+                require_empty!(cap_buf, "GracefulRestart");
+                Ok((
+                    cap_buf,
+                    Self::GracefulRestart {
+                        restart_state,
+                        restart_time,
+                        entries,
+                    },
+                ))
+            }
+            v if v == CapabilityDiscriminants::FourByteAsn as u8 => {
+                let (cap_buf, asn) = be_u32(cap_buf)?;
+                require_empty!(cap_buf, "FourByteAsn");
+                Ok((cap_buf, Self::FourByteAsn { asn }))
+            }
+            v if v == CapabilityDiscriminants::AddPath as u8 => {
+                let (cap_buf, afi) = be_u16(cap_buf)?;
+                let (cap_buf, safi) = be_u8(cap_buf)?;
+                let (cap_buf, send_recv) = be_u8(cap_buf)?;
+                let afi = AddressFamilyId::try_from(afi).map_err(|e| fail!("{}", e))?;
+                let safi = SubsequentAfi::try_from(safi).map_err(|e| fail!("{}", e))?;
+                let send_recv = AddPathSendRecv::try_from(send_recv).map_err(|e| fail!("{}", e))?;
+                require_empty!(cap_buf, "AddPath");
+                Ok((
+                    cap_buf,
+                    Self::AddPath {
+                        afi,
+                        safi,
+                        send_recv,
+                    },
+                ))
+            }
+            v if v == CapabilityDiscriminants::EnhancedRouteRefresh as u8 => {
+                require_empty!(cap_buf, "EnhancedRouteRefresh");
+                Ok((cap_buf, Self::EnhancedRouteRefresh))
+            }
+            v if v == CapabilityDiscriminants::LongLivedGracefulRestart as u8 => {
+                let parse_llgr = |buf: &'a [u8]| -> IResult<
+                    &'a [u8],
+                    LongLivedGracefulRestart,
+                    BgpParserError<&'a [u8]>,
+                > {
+                    let (buf, afi) = be_u16(buf)?;
+                    let (buf, safi) = be_u8(buf)?;
+                    let (buf, flags) = be_u8(buf)?;
+                    let (buf, stale_time) = be_u24(buf)?;
+                    let afi = AddressFamilyId::try_from(afi).map_err(|e| fail!("{}", e))?;
+                    let safi = SubsequentAfi::try_from(safi).map_err(|e| fail!("{}", e))?;
+                    Ok((
+                        buf,
+                        LongLivedGracefulRestart {
+                            afi,
+                            safi,
+                            flags,
+                            stale_time,
+                        },
+                    ))
+                };
+                let (cap_buf, entries) = nom::multi::many0(parse_llgr).parse(cap_buf)?;
+                require_empty!(cap_buf, "LongLivedGracefulRestart");
+                Ok((cap_buf, Self::LongLivedGracefulRestart(entries)))
+            }
+            type_code => {
+                // Handling an unknown capability, so just parse it out and store the value
+                // as bytes.
+                Ok((
+                    &[],
+                    Self::UnknownCapability {
+                        type_code,
+                        length: cap_buf.len() as u8,
+                        value: cap_buf.to_vec(),
+                    },
+                ))
+            }
+        }
+    }
+
+    pub fn to_wire(&self, _ctx: &ParserContext, out: &mut BytesMut) -> Result<()> {
+        out.put_u8(self.discriminant());
+        out.put_u8(self.payload_len());
+        match self {
+            Capability::MultiProtocol { afi, safi } => {
+                out.put_u16(*afi as u16);
+                out.put_u8(0); // Reserved byte.
+                out.put_u8(*safi as u8);
+            }
+            Capability::RouteRefresh => {}
+            Capability::OutboundRouteFilter { afi, safi, orfs } => {
+                out.put_u16(*afi as u16);
+                out.put_u8(0); // Reserved byte.
+                out.put_u8(*safi as u8);
+                for orf in orfs {
+                    out.put_u8(orf.r#type.clone().into());
+                    out.put_u8(orf.send_recv.clone() as u8);
+                }
+            }
+            Capability::ExtendedNextHop { entries } => {
+                for entry in entries {
+                    out.put_u16(entry.afi as u16);
+                    out.put_u16(entry.safi as u16);
+                    out.put_u16(entry.nh_afi as u16);
+                }
+            }
+            Capability::ExtendedMessage => {}
+            Capability::BgpSec { header, afi } => {
+                out.put_u8(header.0);
+                out.put_u16(*afi as u16);
+            }
+            Capability::MultiLabelCompat {} => todo!(),
+            Capability::BgpRole { role } => {
+                out.put_u8(role.into());
+            }
+            Capability::GracefulRestart {
+                restart_state,
+                restart_time,
+                entries,
+            } => {
+                let mut flags_restart_time = 0;
+                if *restart_state {
+                    flags_restart_time |= 1 << 15;
+                }
+                if *restart_time > 0xfff {
+                    bail!("Restart time too large to be encoded: {}", restart_time);
+                }
+                flags_restart_time |= restart_time;
+                out.put_u16(flags_restart_time);
+                for entry in entries {
+                    out.put_u16(entry.afi as u16);
+                    out.put_u8(entry.safi as u8);
+                    let mut flags = 0;
+                    if entry.preserve_forwarding {
+                        flags |= 1 << 7;
+                    }
+                    out.put_u8(flags);
+                }
+            }
+            Capability::FourByteAsn { asn } => {
+                out.put_u32(*asn);
+            }
+            Capability::AddPath {
+                afi,
+                safi,
+                send_recv,
+            } => {
+                out.put_u16(*afi as u16);
+                out.put_u8(*safi as u8);
+                out.put_u8(send_recv.into());
+            }
+            Capability::EnhancedRouteRefresh => {}
+            Capability::LongLivedGracefulRestart(llgrs) => {
+                for llgr in llgrs {
+                    out.put_u16(llgr.afi as u16);
+                    out.put_u8(llgr.safi as u8);
+                    out.put_u8(llgr.flags as u8);
+                    out.put(&llgr.stale_time.to_be_bytes()[1..]);
+                }
+            }
+            Capability::UnknownCapability { value, .. } => out.put(value.as_slice()),
+        }
+        Ok(())
+    }
+
+    pub fn wire_len(&self, _ctx: &ParserContext) -> Result<u16> {
+        Ok(2 + self.payload_len() as u16)
+    }
+
+    fn payload_len(&self) -> u8 {
+        match self {
+            Capability::MultiProtocol { .. } => 4,
+            Capability::RouteRefresh => 0,
+            Capability::OutboundRouteFilter { orfs, .. } => 4 + 2 * orfs.len() as u8,
+            Capability::ExtendedNextHop { entries } => 6 * entries.len() as u8,
+            Capability::ExtendedMessage => 0,
+            Capability::BgpSec { .. } => 3,
+            Capability::MultiLabelCompat {} => todo!(),
+            Capability::BgpRole { .. } => 1,
+            Capability::GracefulRestart { entries, .. } => 2 + 4 * entries.len() as u8,
+            Capability::FourByteAsn { .. } => 4,
+            Capability::AddPath { .. } => 4,
+            Capability::EnhancedRouteRefresh => 0,
+            Capability::LongLivedGracefulRestart(long_lived_graceful_restarts) => {
+                8 * long_lived_graceful_restarts.len() as u8
+            }
+            Capability::UnknownCapability { value, .. } => value.len() as u8,
+        }
+    }
+}
+
+/// Represents an entry for the OutboundRouteFilter capability.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct OutboundRouteFilterEntry {
+    pub r#type: OrfType,
+    pub send_recv: OrfSendRecv,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, EnumDiscriminants, PartialEq, Eq)]
+#[repr(u8)]
+pub enum OrfType {
+    Reserved = 0,
+    Unassigned(u8),
+    AddressPrefix = 64,
+    CoveringPrefix = 65,
+    VpnPrefix = 66,
+    VendorSpecific(u8),
+}
+
+impl From<u8> for OrfType {
+    fn from(value: u8) -> Self {
+        match value {
+            v if v == OrfTypeDiscriminants::Reserved as u8 => Self::Reserved,
+            v if (1..64).contains(&v) => Self::Unassigned(v),
+            v if v == OrfTypeDiscriminants::AddressPrefix as u8 => Self::AddressPrefix,
+            v if v == OrfTypeDiscriminants::CoveringPrefix as u8 => Self::CoveringPrefix,
+            v if v == OrfTypeDiscriminants::VpnPrefix as u8 => Self::VpnPrefix,
+            other => Self::VendorSpecific(other),
+        }
+    }
+}
+
+impl From<OrfType> for u8 {
+    fn from(value: OrfType) -> Self {
+        match value {
+            OrfType::Reserved => OrfTypeDiscriminants::Reserved as u8,
+            OrfType::Unassigned(inner) => inner,
+            OrfType::AddressPrefix => OrfTypeDiscriminants::AddressPrefix as u8,
+            OrfType::CoveringPrefix => OrfTypeDiscriminants::CoveringPrefix as u8,
+            OrfType::VpnPrefix => OrfTypeDiscriminants::VpnPrefix as u8,
+            OrfType::VendorSpecific(inner) => inner,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, EnumDiscriminants, PartialEq, Eq)]
+#[repr(u8)]
+pub enum OrfSendRecv {
+    Receive = 1,
+    Send = 2,
+    Both = 3,
+}
+
+impl TryFrom<u8> for OrfSendRecv {
+    type Error = eyre::ErrReport;
+
+    fn try_from(value: u8) -> Result<Self> {
+        Ok(match value {
+            value if value == OrfSendRecv::Receive as u8 => OrfSendRecv::Receive,
+            value if value == OrfSendRecv::Send as u8 => OrfSendRecv::Send,
+            value if value == OrfSendRecv::Both as u8 => OrfSendRecv::Both,
+            other => bail!("Invalid ORF send/recv value: {}", other),
+        })
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, EnumDiscriminants, PartialEq, Eq)]
+#[repr(u8)]
+pub enum AddPathSendRecv {
+    Receive = 1,
+    Send = 2,
+    Both = 3,
+}
+
+impl TryFrom<u8> for AddPathSendRecv {
+    type Error = eyre::ErrReport;
+
+    fn try_from(value: u8) -> Result<Self> {
+        Ok(match value {
+            value if value == AddPathSendRecv::Receive as u8 => AddPathSendRecv::Receive,
+            value if value == AddPathSendRecv::Send as u8 => AddPathSendRecv::Send,
+            value if value == AddPathSendRecv::Both as u8 => AddPathSendRecv::Both,
+            other => bail!("Invalid AddPathSendRecv send/recv value: {}", other),
+        })
+    }
+}
+
+impl From<&AddPathSendRecv> for u8 {
+    fn from(value: &AddPathSendRecv) -> Self {
+        match value {
+            AddPathSendRecv::Receive => AddPathSendRecv::Receive as u8,
+            AddPathSendRecv::Send => AddPathSendRecv::Send as u8,
+            AddPathSendRecv::Both => AddPathSendRecv::Both as u8,
+        }
+    }
+}
+
+/// `ExtendedNextHop` allows for the nexthop to be for a different address family
+/// than the one being used to advertise prefixes for. E.g. it allows for sending
+/// IPv4 prefixes with an IPv6 nexthop.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct ExtendedNextHop {
+    /// The Address Family to update the nexthop format for.
+    pub afi: AddressFamilyId,
+    /// The Subsequent Address Family to update the nexthop format for.
+    pub safi: SubsequentAfi,
+    /// The Address Family that nexthops will be encoded as.
+    pub nh_afi: AddressFamilyId,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, EnumDiscriminants, PartialEq, Eq)]
+#[repr(u8)]
+pub enum BgpRole {
+    Provider = 0,
+    RouteServer = 1,
+    RouteServerClient = 2,
+    Customer = 3,
+    Peer = 4,
+    Unknown(u8),
+}
+
+impl From<u8> for BgpRole {
+    fn from(value: u8) -> Self {
+        match value {
+            v if v == BgpRoleDiscriminants::Provider as u8 => Self::Provider,
+            v if v == BgpRoleDiscriminants::RouteServer as u8 => Self::RouteServer,
+            v if v == BgpRoleDiscriminants::RouteServerClient as u8 => Self::RouteServerClient,
+            v if v == BgpRoleDiscriminants::Customer as u8 => Self::Customer,
+            v if v == BgpRoleDiscriminants::Peer as u8 => Self::Peer,
+            other => Self::Unknown(other),
+        }
+    }
+}
+
+impl From<&BgpRole> for u8 {
+    fn from(value: &BgpRole) -> Self {
+        match value {
+            BgpRole::Provider => BgpRoleDiscriminants::Provider as u8,
+            BgpRole::RouteServer => BgpRoleDiscriminants::RouteServer as u8,
+            BgpRole::RouteServerClient => BgpRoleDiscriminants::RouteServerClient as u8,
+            BgpRole::Customer => BgpRoleDiscriminants::Customer as u8,
+            BgpRole::Peer => BgpRoleDiscriminants::Peer as u8,
+            BgpRole::Unknown(other) => *other,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct LongLivedGracefulRestart {
+    pub afi: AddressFamilyId,
+    pub safi: SubsequentAfi,
+    pub flags: u8,
+    /// stale_time is the time in seconds after which routes are considered stale.
+    /// Note that this is represented as a u24 on the wire.
+    pub stale_time: u32,
+}
+
+bitfield! {
+    #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
+    pub struct BgpSecHeader(u8);
+    impl new;
+    u8,   version, set_version   : 3, 0;   // 4 bits
+    bool, dir,     set_dir       : 4;      // single bit (hi==lo)
+    u8,   unassigned, set_unassigned : 7, 5; // 3 bits
+}
+
+/// Represents an entry in the BGP Graceful Restart capability.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct GracefulRestartEntry {
+    afi: AddressFamilyId,
+    safi: SubsequentAfi,
+    /// Forwarding State (F) bit, which can be used to indicate whether the
+    /// forwarding state for routes that were advertised with the given AFI
+    /// and SAFI has indeed been preserved during the previous BGP restart.
+    preserve_forwarding: bool,
+}
+
+#[cfg(test)]
+mod tests {
+    use std::net::Ipv4Addr;
+
+    use bytes::BytesMut;
+    use eyre::Result;
+
+    use crate::{
+        constants::{AddressFamilyId, SubsequentAfi},
+        open::{Capability, ExtendedNextHop, GracefulRestartEntry, OpenMessage, OpenOption},
+        parser::ParserContext,
+    };
+
+    macro_rules! test_capability_roundtrip {
+        ($name:ident, $input_bytes: expr, $expected: expr) => {
+            #[test]
+            fn $name() -> Result<()> {
+                let ctx = &default_v6_context();
+                let (buf, parsed) = Capability::from_wire(ctx, $input_bytes)?;
+                assert_eq!(parsed, $expected);
+                assert!(buf.is_empty());
+                let mut out = BytesMut::with_capacity(u16::MAX as usize);
+                parsed.to_wire(ctx, &mut out)?;
+                assert_eq!(out.to_vec(), $input_bytes);
+                Ok(())
+            }
+        };
+    }
+    /// Creates a default context for evaluating the test cases below.
+    /// This uses `four_octet_asn` set to true and address_family to IPv6.
+    fn default_v6_context() -> ParserContext {
+        ParserContext {
+            four_octet_asn: Some(true),
+            address_family: Some(AddressFamilyId::Ipv6),
+        }
+    }
+
+    test_capability_roundtrip!(
+        test_multiptotocol,
+        &[0x01, 0x04, 0x00, 0x01, 0x00, 0x01],
+        Capability::MultiProtocol {
+            afi: AddressFamilyId::Ipv4,
+            safi: SubsequentAfi::Unicast
+        }
+    );
+
+    test_capability_roundtrip!(test_route_refresh, &[0x02, 0x00], Capability::RouteRefresh);
+
+    test_capability_roundtrip!(
+        test_route_refresh_cisco_unsupported,
+        &[0x80, 0x00],
+        Capability::UnknownCapability {
+            type_code: 0x80,
+            length: 0x00,
+            value: vec![]
+        }
+    );
+
+    test_capability_roundtrip!(
+        test_four_octet_asn,
+        &[0x41, 0x04, 0x00, 0x00, 0xfd, 0xe8],
+        Capability::FourByteAsn { asn: 65000 }
+    );
+
+    test_capability_roundtrip!(
+        test_graceful_restart,
+        &[0x40, 0x06, 0x01, 0x2c, 0x00, 0x01, 0x01, 0x00],
+        Capability::GracefulRestart {
+            restart_state: false,
+            restart_time: 300,
+            entries: vec![GracefulRestartEntry {
+                afi: AddressFamilyId::Ipv4,
+                safi: SubsequentAfi::Unicast,
+                preserve_forwarding: false,
+            }]
+        }
+    );
+
+    test_capability_roundtrip!(
+        test_extended_nexthop,
+        &[
+            0x05, 0x12, 0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x02, 0x00, 0x02,
+            0x00, 0x01, 0x00, 0x80, 0x00, 0x02
+        ],
+        Capability::ExtendedNextHop {
+            entries: vec![
+                ExtendedNextHop {
+                    afi: AddressFamilyId::Ipv4,
+                    safi: SubsequentAfi::Unicast,
+                    nh_afi: AddressFamilyId::Ipv6,
+                },
+                ExtendedNextHop {
+                    afi: AddressFamilyId::Ipv4,
+                    safi: SubsequentAfi::Multicast,
+                    nh_afi: AddressFamilyId::Ipv6,
+                },
+                ExtendedNextHop {
+                    afi: AddressFamilyId::Ipv4,
+                    safi: SubsequentAfi::MplsLabelledVpn,
+                    nh_afi: AddressFamilyId::Ipv6
+                }
+            ]
+        }
+    );
+
+    #[test]
+    fn test_open_roundtrip() -> Result<()> {
+        let buf = &[
+            0x04, 0xfd, 0xe8, 0x00, 0xb4, 0x0a, 0x00, 0x00, 0x01, 0x38, 0x02, 0x06, 0x01, 0x04,
+            0x00, 0x01, 0x00, 0x01, 0x02, 0x02, 0x80, 0x00, 0x02, 0x02, 0x02, 0x00, 0x02, 0x06,
+            0x41, 0x04, 0x00, 0x00, 0xfd, 0xe8, 0x02, 0x08, 0x40, 0x06, 0x01, 0x2c, 0x00, 0x01,
+            0x01, 0x00, 0x02, 0x14, 0x05, 0x12, 0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01,
+            0x00, 0x02, 0x00, 0x02, 0x00, 0x01, 0x00, 0x80, 0x00, 0x02,
+        ];
+        let expected = OpenMessage {
+            version: 4,
+            asn: 65000,
+            hold_time: 180,
+            identifier: Ipv4Addr::new(10, 0, 0, 1),
+            options: vec![
+                OpenOption::Capabilities(vec![Capability::MultiProtocol {
+                    afi: AddressFamilyId::Ipv4,
+                    safi: SubsequentAfi::Unicast,
+                }]),
+                OpenOption::Capabilities(vec![Capability::UnknownCapability {
+                    type_code: 0x80,
+                    length: 0x00,
+                    value: vec![],
+                }]),
+                OpenOption::Capabilities(vec![Capability::RouteRefresh]),
+                OpenOption::Capabilities(vec![Capability::FourByteAsn { asn: 65000 }]),
+                OpenOption::Capabilities(vec![Capability::GracefulRestart {
+                    restart_state: false,
+                    restart_time: 300,
+                    entries: vec![GracefulRestartEntry {
+                        afi: AddressFamilyId::Ipv4,
+                        safi: SubsequentAfi::Unicast,
+                        preserve_forwarding: false,
+                    }],
+                }]),
+                OpenOption::Capabilities(vec![Capability::ExtendedNextHop {
+                    entries: vec![
+                        ExtendedNextHop {
+                            afi: AddressFamilyId::Ipv4,
+                            safi: SubsequentAfi::Unicast,
+                            nh_afi: AddressFamilyId::Ipv6,
+                        },
+                        ExtendedNextHop {
+                            afi: AddressFamilyId::Ipv4,
+                            safi: SubsequentAfi::Multicast,
+                            nh_afi: AddressFamilyId::Ipv6,
+                        },
+                        ExtendedNextHop {
+                            afi: AddressFamilyId::Ipv4,
+                            safi: SubsequentAfi::MplsLabelledVpn,
+                            nh_afi: AddressFamilyId::Ipv6,
+                        },
+                    ],
+                }]),
+            ],
+        };
+
+        let ctx = default_v6_context();
+        let (_, parsed) = OpenMessage::from_wire(&ctx, buf)?;
+        assert_eq!(parsed, expected);
+        let mut out = BytesMut::with_capacity(u16::MAX as usize);
+        parsed.to_wire(&ctx, &mut out)?;
+        assert_eq!(buf.to_vec(), out.to_vec());
+        Ok(())
+    }
+}

crates/packet/src/parser.rs

@@ -34,6 +34,9 @@ impl std::error::Error for ToWireError {}
 // Custom error type for the parser.
 #[derive(Debug)]
 pub enum BgpParserError<I> {
+    /// ProtocolError encapsulates protocol level semantics problems that require
+    /// action from the caller of the parser.
+    ProtocolError(ProtocolErrorValues),
     CustomText(&'static str),
     Eyre(eyre::ErrReport),
     Nom(I, ErrorKind),
@@ -47,3 +50,12 @@ impl<I> ParseError<I> for BgpParserError<I> {
         other
     }
 }
+
+#[derive(Debug)]
+pub enum ProtocolErrorValues {
+    /// `UnsupportedVersion` is returned when the BGP Open message received is for a
+    /// version other than one we support. The unsupported version number is the value.
+    UnsupportedVersion(u8),
+    /// `UnknownOpenOption` is returned with the open option type code that is unknown.
+    UnknownOpenOption(u8),
+}