Refactored client binary.

crates/route_client/Cargo.toml

@@ -0,0 +1,37 @@
+[package]
+name = "route_client"
+
+edition.workspace      = true
+homepage.workspace     = true
+license.workspace      = true
+repository.workspace   = true
+rust-version.workspace = true
+version.workspace      = true
+
+[lints]
+workspace = true
+
+[dependencies]
+async-trait.workspace                      = true
+bgp_packet.workspace                       = true
+byteorder                                  = "1.4.3"
+bytes.workspace                            = true
+eyre.workspace                             = true
+futures.workspace                          = true
+ip_network_table-deps-treebitmap.workspace = true
+log.workspace                              = true
+netlink-packet-route.workspace             = true
+netlink-packet-utils.workspace             = true
+nom                                        = "7.1"
+prost.workspace                            = true
+rtnetlink.workspace                        = true
+serde.workspace                            = true
+tokio-stream                               = "0.1.14"
+tokio-util                                 = { version = "0.7.10", features = ["codec"] }
+tokio.workspace                            = true
+tonic.workspace                            = true
+tracing.workspace                          = true
+warp.workspace                             = true
+
+[build-dependencies]
+tonic-build = { version = "0.5.1", features = ["compression", "prost"] }

crates/route_client/build.rs

@@ -0,0 +1,19 @@
+// Copyright 2021 Rayhaan Jaufeerally.
+//
+// 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.
+
+fn main() {
+    tonic_build::configure()
+        .compile(&["proto/route_service.proto"], &["proto"])
+        .unwrap();
+}

crates/route_client/proto/route_service.proto

@@ -0,0 +1,83 @@
+// Copyright 2021 Rayhaan Jaufeerally.
+//
+// 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.
+
+syntax = "proto3";
+
+package bgpd.grpc;
+
+enum AddressFamily {
+  UNKNOWN = 0;
+  IPv4 = 1;
+  IPv6 = 2;
+}
+
+message Prefix {
+  bytes ip_prefix = 1;
+  int32 prefix_len = 2;
+  AddressFamily address_family = 3;
+}
+
+// Path represents the metadata associated with the route to a particular
+// prefix.
+message Path {
+  bytes nexthop = 1;
+  string peer_name = 2;
+  uint32 local_pref = 3;
+  uint32 med = 4;
+  repeated uint32 as_path = 5;
+  // TODO: Path attributes. Not yet supported because we need to generate proto
+  // definitions for all of them.
+}
+
+message PathSet {
+  uint64 epoch = 1;
+  Prefix prefix = 2;
+  repeated Path paths = 3;
+}
+
+message StreamPathsRequest { AddressFamily address_family = 1; }
+
+message DumpPathsRequest { AddressFamily address_family = 1; };
+
+message DumpPathsResponse {
+  uint64 epoch = 1;
+  repeated PathSet path_sets = 2;
+};
+
+service RouteService {
+  // DumpPaths returns all the paths currently in the RIB.
+  rpc DumpPaths(DumpPathsRequest) returns (DumpPathsResponse);
+  // StreamPaths dumps the existing routes and starts streaming updates to the
+  // RIB.
+  rpc StreamPaths(StreamPathsRequest) returns (stream PathSet);
+}
+
+message PeerStatusRequest {}
+
+message PeerStatus {
+  string peer_name = 1;
+  string state = 2;
+  uint64 session_established_time = 3;
+  uint64 last_messaage_time = 4;
+  uint64 route_updates_in = 5;
+  uint64 route_updates_out = 6;
+}
+
+message PeerStatusResponse { repeated PeerStatus peer_status = 1; }
+
+// BGPServerAdminService implements an administrative interface to
+// view the status and control the operation of this BGP server.
+service BGPServerAdminService {
+  rpc PeerStatus(PeerStatusRequest) returns (PeerStatusResponse);
+}

crates/route_client/src/fib_state.rs

@@ -0,0 +1,180 @@
+// Copyright 2021 Rayhaan Jaufeerally.
+//
+// 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.
+
+use futures::lock::Mutex;
+use ip_network_table_deps_treebitmap::address::Address;
+use ip_network_table_deps_treebitmap::IpLookupTable;
+use std::convert::{TryFrom, TryInto};
+use std::fmt::Formatter;
+use std::net::Ipv6Addr;
+use std::net::{IpAddr, Ipv4Addr};
+use std::sync::Arc;
+use tracing::{trace, warn};
+
+use bgp_packet::constants::AddressFamilyIdentifier;
+use bgp_packet::nlri::NLRI;
+
+use crate::southbound_interface::SouthboundInterface;
+
+/// fib_state implements the logic to maintain forwarding routes in the FIB.
+/// This for now means the Linux Kernel via Netlink, but in the future can
+/// be extended to include other targets such as OpenFlow or even program
+/// a router using BGP.
+
+#[derive(Debug)]
+pub struct FibEntry {
+    nexthop: IpAddr,
+}
+
+pub struct FibState<A: Address, S: SouthboundInterface> {
+    pub fib: IpLookupTable<A, Arc<Mutex<FibEntry>>>,
+    pub southbound: S,
+    pub af: AddressFamilyIdentifier,
+    pub table: u32,
+}
+
+impl<A: Address, S: SouthboundInterface> std::fmt::Debug for FibState<A, S> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> {
+        write!(f, "FibState af: {:?}, table: {}", self.af, self.table)
+    }
+}
+
+/// to_octets provides an interface for accessing an address as a vector of bytes.
+/// This is implemented for IPv4Addr and IPv6Addr to be able to use them interchangably
+/// to send updates to the kernel.
+pub trait ToOctets {
+    fn octets(&self) -> Vec<u8>;
+}
+
+impl ToOctets for Ipv4Addr {
+    fn octets(&self) -> Vec<u8> {
+        self.octets().into()
+    }
+}
+
+impl ToOctets for Ipv6Addr {
+    fn octets(&self) -> Vec<u8> {
+        self.octets().into()
+    }
+}
+
+impl<
+        A: Address
+            + std::convert::TryFrom<NLRI>
+            + ToOctets
+            + std::cmp::PartialEq
+            + std::fmt::Display
+            + std::fmt::Debug,
+        S: SouthboundInterface,
+    > FibState<A, S>
+where
+    String: From<<A as TryFrom<NLRI>>::Error>,
+{
+    /// route_add requests updating the nexthop to a particular path if it is not already
+    /// the best path.
+    pub async fn route_add(&mut self, nlri: &NLRI, nexthop: IpAddr) -> Result<(), String> {
+        // Lookup the path in the Fib, there are three possible outcomes:
+        // 1. The route is not yet known, we add it to the FibState and inject it into the kernel,
+        // 2. The route is known and has a prior nexthop that needs to be updated
+        // 3. The route is known and has the same nexthop: no-op.
+        let prefix_addr: A = nlri.clone().try_into()?;
+        match self
+            .fib
+            .exact_match(prefix_addr, nlri.prefixlen.into())
+            .as_mut()
+        {
+            Some(entry_wrapped) => {
+                let mut entry = entry_wrapped.lock().await;
+                if entry.nexthop == nexthop {
+                    // Nothing to do, route already in kernel.
+                    trace!("Skipping route that already exists in kernel");
+                } else {
+                    // Remove old route
+                    trace!("Remove old route: {:?}", entry);
+                    if let Err(e) = self.southbound.route_del(nlri.clone(), entry.nexthop).await {
+                        warn!(
+                                "Southbound interface returned error when trying to remove route: {} via {}, error: {}",
+                                nlri, entry.nexthop, e
+                            );
+                        return Err("Netlink remove error".to_string());
+                    }
+
+                    // Add new route
+                    trace!(
+                        "Add new route: prefix: {:?}, nexthop: {}",
+                        nlri.prefix,
+                        nexthop
+                    );
+                    if let Err(e) = self
+                        .southbound
+                        .route_add(self.af, nlri.clone(), nexthop)
+                        .await
+                    {
+                        warn!(
+                            "Netlink returned error when trying to add route: {} via {}, error: {}",
+                            nlri, nexthop, e
+                        );
+                        return Err("Netlink add error".to_string());
+                    }
+
+                    entry.nexthop = nexthop;
+                }
+            }
+            None => {
+                // Need to insert a new entry for this route
+                let entry = FibEntry {
+                    nexthop: nexthop.clone(),
+                };
+
+                if let Err(e) = self
+                    .southbound
+                    .route_add(self.af, nlri.clone(), nexthop)
+                    .await
+                {
+                    warn!(
+                        "Netlink returned error when trying to add route: {} via {}, error: {}",
+                        nlri, nexthop, e
+                    );
+                    return Err("Netlink add error".to_string());
+                }
+
+                let addr: A = nlri.clone().try_into()?;
+                self.fib
+                    .insert(addr, nlri.prefixlen.into(), Arc::new(Mutex::new(entry)));
+            }
+        };
+        Ok(())
+    }
+
+    /// route_del removes a route from the FibState and kernel.
+    pub async fn route_del(&mut self, nlri: NLRI) -> Result<(), String> {
+        let prefix_addr: A = nlri.clone().try_into()?;
+        if let Some(entry_wrapped) = self.fib.exact_match(prefix_addr, nlri.prefixlen.into()) {
+            {
+                let entry = entry_wrapped.lock().await;
+                if let Err(e) = self.southbound.route_del(nlri.clone(), entry.nexthop).await {
+                    warn!(
+                        "Failed to apply route mutation to remove NLRI: {}, error: {}",
+                        nlri, e
+                    );
+                }
+            }
+            self.fib.remove(prefix_addr, nlri.prefixlen.into());
+        } else {
+            warn!("Failed to find prefix to remove from FIB: {}", nlri);
+        }
+
+        Ok(())
+    }
+}

crates/route_client/src/lib.rs

@@ -0,0 +1,205 @@
+// Copyright 2021 Rayhaan Jaufeerally.
+//
+// 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.
+
+pub mod fib_state;
+pub mod netlink;
+pub mod southbound_interface;
+
+use log::trace;
+use std::convert::TryInto;
+use std::net::IpAddr;
+use std::net::Ipv4Addr;
+
+use std::net::Ipv6Addr;
+use std::str::FromStr;
+use std::time::Duration;
+
+use bgp_packet::constants::AddressFamilyIdentifier;
+use bgp_packet::nlri::NLRI;
+
+use eyre::{anyhow, Result};
+use ip_network_table_deps_treebitmap::IpLookupTable;
+use tonic::transport::Endpoint;
+use tonic::transport::Uri;
+use tracing::{info, warn};
+
+use crate::fib_state::FibState;
+use crate::netlink::NetlinkConnector;
+use crate::proto::route_service_client::RouteServiceClient;
+use crate::southbound_interface::SouthboundInterface;
+
+pub mod proto {
+    tonic::include_proto!("bgpd.grpc");
+}
+
+fn vec_to_array<T, const N: usize>(v: Vec<T>) -> Result<[T; N]> {
+    v.try_into()
+        .map_err(|_| eyre::Error::msg("Wrong size of Vec".to_string()))
+}
+
+/// Temporary hack to select the route to install to the FIB.
+/// TODO: Implement proper route selection logic.
+fn select_best_route(ps: &proto::PathSet) -> Option<proto::Path> {
+    let mut selected: Option<proto::Path> = None;
+    for path in &ps.paths {
+        if let Some(current) = selected.as_ref() {
+            if path.local_pref < current.local_pref {
+                selected = Some(path.clone());
+            }
+        } else {
+            selected = Some(path.clone());
+        }
+    }
+    selected
+}
+
+pub async fn run_connector_v4<S: SouthboundInterface>(
+    route_server: String,
+    rt_table: u32,
+    dry_run: bool,
+    southbound: S,
+) -> Result<()> {
+    // Create netlink socket.
+    let mut fib_state = FibState::<Ipv4Addr, S> {
+        fib: IpLookupTable::new(),
+        southbound,
+        af: AddressFamilyIdentifier::Ipv4,
+        table: rt_table,
+    };
+
+    let uri = Uri::from_str(route_server.as_str()).unwrap();
+    let endpoint = Endpoint::from(uri).keep_alive_timeout(Duration::from_secs(10));
+    let mut client = RouteServiceClient::connect(endpoint).await?;
+    let request = proto::StreamPathsRequest {
+        address_family: proto::AddressFamily::IPv4.into(),
+    };
+
+    let mut stream = client.stream_paths(request).await?.into_inner();
+    let mut msg_ctr: u64 = 0;
+    while let Some(route) = stream.message().await? {
+        let nlri = NLRI {
+            afi: AddressFamilyIdentifier::Ipv4,
+            prefixlen: route.prefix.as_ref().unwrap().prefix_len as u8,
+            prefix: route.prefix.as_ref().unwrap().ip_prefix.clone(),
+        };
+
+        trace!("IPv4 Update {} for: {} ", msg_ctr, nlri);
+        msg_ctr += 1;
+
+        if !dry_run {
+            if !route.paths.is_empty() {
+                if let Some(best) = select_best_route(&route) {
+                    // Hack to convert the nexthop into a v4 addr
+                    let nh_bytes: [u8; 4] = vec_to_array(best.nexthop.clone())?;
+                    let nh_addr: Ipv4Addr = Ipv4Addr::from(nh_bytes);
+                    if let Err(e) = fib_state.route_add(&nlri, IpAddr::V4(nh_addr)).await {
+                        return Err(anyhow!("Failed to add route {}: {}", nlri, e));
+                    }
+                }
+            } else {
+                // No more paths, delete
+                if let Err(e) = fib_state.route_del(nlri).await {
+                    return Err(anyhow!("Failed to delete route: {}", e));
+                }
+            }
+        }
+
+        trace!("Number of paths: {}", route.paths.len());
+        for path in &route.paths {
+            // TODO: have a proper error here not unwrap.
+            let nexthop_bytes: [u8; 4] = path.nexthop.clone().try_into().unwrap();
+            let nexthop: Ipv4Addr = nexthop_bytes.into();
+            trace!(
+                "nexthop: {}, peer: {}, local_pref: {}, med: {}, as_path: {:?}",
+                nexthop,
+                path.peer_name,
+                path.local_pref,
+                path.med,
+                path.as_path
+            );
+        }
+    }
+
+    unreachable!()
+}
+
+pub async fn run_connector_v6<S: SouthboundInterface>(
+    route_server: String,
+    rt_table: u32,
+    dry_run: bool,
+    southbound: S,
+) -> Result<()> {
+    let mut fib_state = FibState::<Ipv6Addr, S> {
+        fib: IpLookupTable::new(),
+        southbound,
+        af: AddressFamilyIdentifier::Ipv6,
+        table: rt_table,
+    };
+
+    let uri = Uri::from_str(route_server.as_str()).unwrap();
+    let endpoint = Endpoint::from(uri).keep_alive_timeout(Duration::from_secs(10));
+    let mut client = RouteServiceClient::connect(endpoint).await?;
+    let request = proto::StreamPathsRequest {
+        address_family: proto::AddressFamily::IPv6.into(),
+    };
+    info!("Request: {:?}", request);
+
+    let mut stream = client.stream_paths(request).await?.into_inner();
+    let mut msg_ctr: u64 = 0;
+    while let Some(route) = stream.message().await? {
+        let nlri = NLRI {
+            afi: AddressFamilyIdentifier::Ipv6,
+            prefixlen: route.prefix.as_ref().unwrap().prefix_len as u8,
+            prefix: route.prefix.as_ref().unwrap().ip_prefix.clone(),
+        };
+
+        trace!("IPv6 Update {} for: {} ", msg_ctr, nlri);
+        msg_ctr += 1;
+
+        if !dry_run {
+            if !route.paths.is_empty() {
+                if let Some(best) = select_best_route(&route) {
+                    // Hack to convert the nexthop into a v6 addr
+                    let nh_bytes: [u8; 16] = vec_to_array(best.nexthop.clone())?;
+                    let nh_addr: Ipv6Addr = Ipv6Addr::from(nh_bytes);
+                    if let Err(e) = fib_state.route_add(&nlri, IpAddr::V6(nh_addr)).await {
+                        return Err(anyhow!("Failed to add route {}: {}", nlri, e));
+                    }
+                }
+            } else {
+                // No more paths, delete
+                if let Err(e) = fib_state.route_del(nlri).await {
+                    return Err(anyhow!("Failed to delete route: {}", e));
+                }
+            }
+        }
+
+        trace!("Number of paths: {}", route.paths.len());
+        for path in &route.paths {
+            // TODO: have a proper error here not unwrap.
+            let nexthop_bytes: [u8; 16] = path.nexthop.clone().try_into().unwrap();
+            let nexthop: Ipv6Addr = nexthop_bytes.into();
+            trace!(
+                "nexthop: {}, peer: {}, local_pref: {}, med: {}, as_path: {:?}",
+                nexthop,
+                path.peer_name,
+                path.local_pref,
+                path.med,
+                path.as_path
+            );
+        }
+    }
+
+    unreachable!()
+}

crates/route_client/src/netlink.rs

@@ -0,0 +1,161 @@
+use async_trait::async_trait;
+use bgp_packet::{constants::AddressFamilyIdentifier, nlri::NLRI};
+use eyre::{eyre, Result};
+use futures::TryStreamExt;
+use netlink_packet_route::route::RouteAddress;
+use netlink_packet_route::route::RouteAttribute;
+use netlink_packet_route::route::RouteHeader;
+use netlink_packet_route::route::RouteMessage;
+use netlink_packet_route::route::RouteProtocol;
+use netlink_packet_route::route::RouteType;
+use netlink_packet_route::AddressFamily as NetlinkAddressFamily;
+use netlink_packet_utils::nla::Nla;
+use rtnetlink::IpVersion;
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
+use std::{convert::TryInto, io::ErrorKind};
+
+use super::southbound_interface::SouthboundInterface;
+
+/// NetlinkConnector implements methods to read/update Linux networking stuff including
+/// routes and link level info.
+pub struct NetlinkConnector {
+    handle: rtnetlink::Handle,
+    table: Option<u32>,
+}
+
+#[async_trait]
+impl SouthboundInterface for NetlinkConnector {
+    async fn route_add(
+        &mut self,
+        address_family: AddressFamilyIdentifier,
+        prefix: NLRI,
+        nexthop: IpAddr,
+    ) -> Result<()> {
+        let route = self.handle.route();
+        match address_family {
+            AddressFamilyIdentifier::Ipv6 => {
+                let prefix_len = prefix.prefixlen;
+                let addr: Ipv6Addr = match prefix.try_into()? {
+                    IpAddr::V6(addr) => addr,
+                    _ => {
+                        return Err(eyre::Error::from(std::io::Error::new(
+                            ErrorKind::InvalidInput,
+                            "Got non-IPv6 address from NLRI",
+                        )))
+                    }
+                };
+                let gw_addr: Ipv6Addr = match nexthop.clone().try_into()? {
+                    IpAddr::V6(addr) => addr,
+                    _ => {
+                        return Err(eyre::Error::from(std::io::Error::new(
+                            ErrorKind::InvalidInput,
+                            "Got non-IPv6 gateway for IPv6 NLRI",
+                        )))
+                    }
+                };
+                let mut mutation = route
+                    .add()
+                    .v6()
+                    .destination_prefix(addr, prefix_len)
+                    .gateway(gw_addr);
+                if let Some(table_id) = self.table {
+                    mutation = mutation.table(table_id.try_into().unwrap());
+                }
+                mutation.execute().await.map_err(|e| eyre::Error::from(e))
+            }
+            AddressFamilyIdentifier::Ipv4 => {
+                let prefix_len = prefix.prefixlen;
+                let addr: Ipv4Addr = match prefix.clone().try_into()? {
+                    IpAddr::V4(addr) => addr,
+                    _ => {
+                        return Err(eyre::Error::from(std::io::Error::new(
+                            ErrorKind::InvalidInput,
+                            "Got non-IPv4 address from NLRI",
+                        )))
+                    }
+                };
+                let gw_addr = match nexthop.clone().try_into()? {
+                    IpAddr::V4(addr) => addr,
+                    _ => {
+                        return Err(eyre::Error::from(std::io::Error::new(
+                            ErrorKind::InvalidInput,
+                            "Got non-IPv4 gateway for IPv4 NLRI",
+                        )))
+                    }
+                };
+                let mut mutation = route
+                    .add()
+                    .v4()
+                    .destination_prefix(addr, prefix_len)
+                    .gateway(gw_addr);
+                if let Some(table_id) = self.table {
+                    mutation = mutation.table(table_id.try_into().unwrap());
+                }
+                mutation.execute().await.map_err(|e| eyre::Error::from(e))
+            }
+        }
+    }
+
+    async fn route_del(&mut self, prefix: NLRI, nexthop: IpAddr) -> Result<()> {
+        let rt_handle = self.handle.route();
+        let destination = match prefix.afi {
+            AddressFamilyIdentifier::Ipv4 => {
+                RouteAddress::Inet(prefix.clone().try_into().map_err(|e: String| eyre!(e))?)
+            }
+            AddressFamilyIdentifier::Ipv6 => {
+                RouteAddress::Inet6(prefix.clone().try_into().map_err(|e: String| eyre!(e))?)
+            }
+        };
+        let nexthop = match nexthop {
+            IpAddr::V4(ipv4) => RouteAddress::Inet(ipv4),
+            IpAddr::V6(ipv6) => RouteAddress::Inet6(ipv6),
+        };
+        let header = RouteHeader {
+            address_family: match prefix.afi {
+                AddressFamilyIdentifier::Ipv4 => NetlinkAddressFamily::Inet,
+                AddressFamilyIdentifier::Ipv6 => NetlinkAddressFamily::Inet6,
+            },
+            destination_prefix_length: prefix.prefixlen,
+            table: self.table.unwrap_or(0) as u8,
+            protocol: RouteProtocol::Bgp,
+            kind: RouteType::Unicast,
+            ..Default::default()
+        };
+        let mut rt_msg: RouteMessage = Default::default();
+        rt_msg.header = header;
+        rt_msg.attributes = vec![
+            RouteAttribute::Destination(destination),
+            RouteAttribute::Gateway(nexthop),
+        ];
+        rt_handle
+            .del(rt_msg)
+            .execute()
+            .await
+            .map_err(|e| eyre::Error::from(e))
+    }
+}
+
+impl NetlinkConnector {
+    pub async fn new(table: Option<u32>) -> Result<Self> {
+        let (connection, handle, _) = rtnetlink::new_connection()?;
+        tokio::spawn(connection);
+        Ok(NetlinkConnector { handle, table })
+    }
+
+    pub async fn dump_routes(
+        &mut self,
+        address_family: AddressFamilyIdentifier,
+        table: Option<u32>,
+    ) -> Result<Vec<RouteMessage>, rtnetlink::Error> {
+        let mut req = self.handle.route().get(match address_family {
+            AddressFamilyIdentifier::Ipv4 => IpVersion::V4,
+            AddressFamilyIdentifier::Ipv6 => IpVersion::V6,
+        });
+        if let Some(table_id) = table {
+            req.message_mut()
+                .attributes
+                .push(RouteAttribute::Table(table_id));
+        }
+        req.execute().try_collect().await
+    }
+}

crates/route_client/src/southbound_interface.rs

@@ -0,0 +1,102 @@
+// Copyright 2021 Rayhaan Jaufeerally.
+//
+// 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.
+
+use std::{collections::HashMap, net::IpAddr};
+
+use async_trait::async_trait;
+use eyre::{eyre, Result};
+use log::info;
+
+use bgp_packet::{constants::AddressFamilyIdentifier, nlri::NLRI};
+
+/// SouthboundInterface provides a uniform API to network forwarding elements
+/// These are devices or targets that perform packet routing and are the end
+/// consumers of packet routing data.
+#[async_trait]
+pub trait SouthboundInterface {
+    /// route_add adds a route towards a particular address_family/NLRI via the given nexthop.
+    async fn route_add(
+        &mut self,
+        address_family: AddressFamilyIdentifier,
+        prefix: NLRI,
+        nexthop: IpAddr,
+    ) -> Result<()>;
+    /// route_del removes the route towards a particular prefix via a given nexthop.
+    async fn route_del(&mut self, prefix: NLRI, nexthop: IpAddr) -> Result<()>;
+}
+
+/// DummyVerifier is a SouthboundInterface that checks that routes are not added more than
+/// once and not removed when there are none.
+pub struct DummyVerifier {
+    route_state: HashMap<NLRI, IpAddr>,
+}
+
+impl std::default::Default for DummyVerifier {
+    fn default() -> DummyVerifier {
+        DummyVerifier {
+            route_state: HashMap::default(),
+        }
+    }
+}
+
+#[async_trait]
+impl SouthboundInterface for DummyVerifier {
+    async fn route_add(
+        &mut self,
+        _: AddressFamilyIdentifier,
+        prefix: NLRI,
+        nexthop: IpAddr,
+    ) -> Result<()> {
+        // Check that the route is not already present.
+        match self.route_state.get(&prefix) {
+            Some(value) => {
+                return Err(eyre!(
+                    "Prefix {} with nexthop {} already contained in route_state! when trying to add {} -> {}",
+                    prefix, value, prefix, nexthop,
+                ));
+            }
+            _ => {}
+        }
+        if self.route_state.get(&prefix).is_some() {}
+        // Insert route into in memory state.
+        self.route_state.insert(prefix, nexthop);
+
+        info!("Route add ok in verifier ({})", self.route_state.len());
+
+        Ok(())
+    }
+
+    async fn route_del(&mut self, prefix: NLRI, nexthop: IpAddr) -> Result<()> {
+        match self.route_state.remove(&prefix) {
+            Some(entry) => {
+                if entry != nexthop {
+                    return Err(eyre!(
+                        "Removed entry's nexthop did not match: {} vs requested {}",
+                        entry,
+                        nexthop
+                    ));
+                }
+            }
+            None => {
+                return Err(eyre!(
+                    "Requested removal of route {} that was not in route_state",
+                    prefix
+                ));
+            }
+        }
+
+        info!("Route del ok in verifier ({})", self.route_state.len());
+        Ok(())
+    }
+}