From bd3277e4fdfe9d8059effd18e885c36f0f9b68d9 Mon Sep 17 00:00:00 2001
From: nrybowski <nicolas.rybowski@uclouvain.be>
Date: Thu, 8 Aug 2024 10:05:21 +0200
Subject: [PATCH] bier: Update BIRT from OSPFv3

Signed-off-by: Nicolas Rybowski <nicolas.rybowski@uclouvain.be>
---
 holo-ospf/src/ospfv2/spf.rs                   |   4 +
 holo-ospf/src/ospfv3/lsdb.rs                  |  36 +++--
 holo-ospf/src/ospfv3/packet/lsa.rs            |   1 +
 holo-ospf/src/ospfv3/spf.rs                   |   1 +
 holo-ospf/src/packet/tlv.rs                   |   1 -
 holo-ospf/src/route.rs                        |  46 ++++++-
 holo-ospf/src/southbound/tx.rs                |  17 ++-
 holo-ospf/src/spf.rs                          |   3 +-
 holo-ospf/tests/packet/ospfv3.rs              |   2 +
 holo-routing/src/ibus.rs                      |   3 +
 holo-routing/src/lib.rs                       |   5 +-
 holo-routing/src/northbound/mod.rs            |   1 +
 holo-routing/src/northbound/state.rs          |  57 +++++++-
 holo-routing/src/rib.rs                       |  31 ++++-
 holo-utils/src/bier.rs                        | 126 ++++++++++++++----
 holo-utils/src/ibus.rs                        |   8 +-
 holo-utils/src/southbound.rs                  |   9 ++
 .../modules/augmentations/holo-routing.yang   |  70 ++++++++++
 holo-yang/src/lib.rs                          |   3 +
 19 files changed, 365 insertions(+), 59 deletions(-)
 create mode 100644 holo-yang/modules/augmentations/holo-routing.yang

diff --git a/holo-ospf/src/ospfv2/spf.rs b/holo-ospf/src/ospfv2/spf.rs
index e350dc8c..c73a28e5 100644
--- a/holo-ospf/src/ospfv2/spf.rs
+++ b/holo-ospf/src/ospfv2/spf.rs
@@ -491,6 +491,8 @@ impl SpfVersion<Self> for Ospfv2 {
                         prefix_options: Default::default(),
                         metric: 0,
                         prefix_sids,
+                        // FIXME: BIER not supported yet for OSPFv2
+                        bier: Default::default(),
                     });
                 }
                 VertexLsa::Router(lsa) => {
@@ -523,6 +525,8 @@ impl SpfVersion<Self> for Ospfv2 {
                                     prefix_options: Default::default(),
                                     metric,
                                     prefix_sids,
+                                    // FIXME: BIER not supported yet for OSPFv2
+                                    bier: Default::default(),
                                 }
                             }),
                     )
diff --git a/holo-ospf/src/ospfv3/lsdb.rs b/holo-ospf/src/ospfv3/lsdb.rs
index c7ab8d49..4c644412 100644
--- a/holo-ospf/src/ospfv3/lsdb.rs
+++ b/holo-ospf/src/ospfv3/lsdb.rs
@@ -820,8 +820,8 @@ fn lsa_orig_intra_area_prefix(
             }
         }
 
-        // Add BIER Sub-TLV(s)
-        if instance.config.bier.enabled {
+        // Add BIER Sub-TLV(s) if BIER is enabled and allowed to advertise
+        if instance.config.bier.enabled && instance.config.bier.advertise {
             bier_config
                 .sd_cfg
                 .iter()
@@ -835,35 +835,29 @@ fn lsa_orig_intra_area_prefix(
                         .encap
                         .iter()
                         .filter_map(|((bsl, encap_type), encap)| {
-                            if let Some(id) = match encap_type {
+                            match encap_type {
                                 BierEncapsulationType::Mpls => {
                                     // TODO: where is the label defined?
                                     Some(BierEncapId::Mpls(Label::new(0)))
                                 }
-                                _ => {
-                                    if let Some(id) = match encap.in_bift_id {
-                                        BierInBiftId::Base(id) => Some(id),
-                                        BierInBiftId::Encoding(true) => Some(0),
-                                        _ => None,
-                                    } {
-                                        Some(BierEncapId::NonMpls(BiftId::new(
-                                            id,
-                                        )))
-                                    } else {
-                                        None
-                                    }
+                                _ => match encap.in_bift_id {
+                                    BierInBiftId::Base(id) => Some(id),
+                                    BierInBiftId::Encoding(true) => Some(0),
+                                    _ => None,
                                 }
-                            } {
-                                Some(BierSubSubTlv::BierEncapSubSubTlv(
+                                .map(|id| {
+                                    BierEncapId::NonMpls(BiftId::new(id))
+                                }),
+                            }
+                            .map(|id| {
+                                BierSubSubTlv::BierEncapSubSubTlv(
                                     BierEncapSubSubTlv::new(
                                         encap.max_si,
                                         id,
                                         (*bsl).into(),
                                     ),
-                                ))
-                            } else {
-                                None
-                            }
+                                )
+                            })
                         })
                         .collect::<Vec<BierSubSubTlv>>();
 
diff --git a/holo-ospf/src/ospfv3/packet/lsa.rs b/holo-ospf/src/ospfv3/packet/lsa.rs
index f204d563..5e45a7e2 100644
--- a/holo-ospf/src/ospfv3/packet/lsa.rs
+++ b/holo-ospf/src/ospfv3/packet/lsa.rs
@@ -2372,6 +2372,7 @@ impl LsaIntraAreaPrefix {
                     // Parse Sub-TLVs.
                     let stlvs = ExtLsaSubTlvs::decode(&mut buf_tlv)?;
                     prefix.prefix_sids = stlvs.prefix_sids;
+                    prefix.bier = stlvs.bier;
                     prefix.unknown_stlvs = stlvs.unknown;
 
                     iap.prefixes.push(prefix);
diff --git a/holo-ospf/src/ospfv3/spf.rs b/holo-ospf/src/ospfv3/spf.rs
index ae935184..4dd1cf5d 100644
--- a/holo-ospf/src/ospfv3/spf.rs
+++ b/holo-ospf/src/ospfv3/spf.rs
@@ -473,6 +473,7 @@ impl SpfVersion<Self> for Ospfv3 {
                         prefix_options: prefix.options,
                         metric: prefix.metric,
                         prefix_sids: prefix.prefix_sids,
+                        bier: prefix.bier,
                     })
             })
     }
diff --git a/holo-ospf/src/packet/tlv.rs b/holo-ospf/src/packet/tlv.rs
index 7e741810..cc70f1f1 100644
--- a/holo-ospf/src/packet/tlv.rs
+++ b/holo-ospf/src/packet/tlv.rs
@@ -458,7 +458,6 @@ impl BierSubTlv {
                     buf.put_u24(0);
                     tlv_encode_end(buf, start_pos);
                 }
-                _ => {}
             }
         }
         tlv_encode_end(buf, start_pos);
diff --git a/holo-ospf/src/route.rs b/holo-ospf/src/route.rs
index 99bd9ef0..17b70f3c 100644
--- a/holo-ospf/src/route.rs
+++ b/holo-ospf/src/route.rs
@@ -10,7 +10,8 @@ use std::net::Ipv4Addr;
 
 use bitflags::bitflags;
 use derive_new::new;
-use holo_utils::ip::IpAddrKind;
+use holo_utils::bier::{BierInfo, Bsl, UnderlayProtocolType};
+use holo_utils::ip::{IpAddrKind, IpNetworkKind};
 use holo_utils::mpls::Label;
 use holo_utils::southbound::OspfRouteType;
 use holo_utils::sr::IgpAlgoType;
@@ -23,6 +24,7 @@ use crate::interface::Interface;
 use crate::lsdb::{LsaEntry, LSA_INFINITY};
 use crate::northbound::configuration::InstanceCfg;
 use crate::packet::lsa::{LsaKey, LsaRouterFlagsVersion};
+use crate::packet::tlv::BierSubSubTlv;
 use crate::spf::{SpfPartialComputation, VertexLsaVersion};
 use crate::version::Version;
 use crate::{southbound, sr};
@@ -41,6 +43,7 @@ pub struct RouteNet<V: Version> {
     pub sr_label: Option<Label>,
     pub nexthops: Nexthops<V::IpAddr>,
     pub flags: RouteNetFlags,
+    pub bier_info: Option<BierInfo>,
 }
 
 bitflags! {
@@ -396,6 +399,7 @@ fn update_rib_intra_area<V>(
             sr_label: None,
             nexthops: stub.vertex.nexthops.clone(),
             flags,
+            bier_info: None,
         };
 
         // Update route's Prefix-SID (if any).
@@ -416,6 +420,44 @@ fn update_rib_intra_area<V>(
             }
         }
 
+        // Update BIER Routing Table (BIRT)
+        if instance.config.bier.enabled && instance.config.bier.receive {
+            let bier_cfg = &instance.shared.bier_config;
+
+            // 1. Does the BFR match a locally configured BIER sub-domain?
+            stub.bier.iter().for_each(|tlv| {
+                if instance.config.bier.mt_id == tlv.mt_id
+                    && let Some(sd_cfg) = bier_cfg
+                        .sd_cfg
+                        .get(&(tlv.sub_domain_id, stub.prefix.address_family()))
+                    && sd_cfg.underlay_protocol == UnderlayProtocolType::Ospf
+                {
+                    // 2. Register entry in BIRT for each supported bitstring length by the BFR prefix
+                    // TODO: Use BAR and IPA
+
+                    // TODO: Sanity check on bitstring lengths upon LSA reception
+
+                    let bfr_bss: Vec<Bsl> = tlv
+                        .subtlvs
+                        .iter()
+                        .filter_map(|stlv| match stlv {
+                            BierSubSubTlv::BierEncapSubSubTlv(encap) => {
+                                Bsl::try_from(encap.bs_len).ok()
+                            }
+                        })
+                        .collect();
+
+                    if !bfr_bss.is_empty() {
+                        new_route.bier_info = Some(BierInfo {
+                            bfr_bss,
+                            sd_id: tlv.sub_domain_id,
+                            bfr_id: tlv.bfr_id,
+                        })
+                    }
+                }
+            });
+        }
+
         // Try to add or update stub route in the RIB.
         route_update(rib, stub.prefix, new_route, instance.config.max_paths);
     }
@@ -483,6 +525,7 @@ fn update_rib_inter_area_networks<V>(
             sr_label: None,
             nexthops: route_br.nexthops.clone(),
             flags: RouteNetFlags::empty(),
+            bier_info: None,
         };
 
         // Update route's Prefix-SID (if any).
@@ -677,6 +720,7 @@ fn update_rib_external<V>(
             sr_label: None,
             nexthops: route_asbr.nexthops.clone(),
             flags: RouteNetFlags::empty(),
+            bier_info: None,
         };
 
         // Try to add or update external route in the RIB.
diff --git a/holo-ospf/src/southbound/tx.rs b/holo-ospf/src/southbound/tx.rs
index f2e4d0dd..5dc4b5bd 100644
--- a/holo-ospf/src/southbound/tx.rs
+++ b/holo-ospf/src/southbound/tx.rs
@@ -10,8 +10,8 @@ use std::net::IpAddr;
 use holo_utils::ibus::{IbusMsg, IbusSender};
 use holo_utils::mpls::Label;
 use holo_utils::southbound::{
-    LabelInstallMsg, LabelUninstallMsg, Nexthop, RouteKeyMsg, RouteMsg,
-    RouteOpaqueAttrs,
+    BierNbrInstallMsg, LabelInstallMsg, LabelUninstallMsg, Nexthop,
+    RouteKeyMsg, RouteMsg, RouteOpaqueAttrs,
 };
 
 use crate::collections::Arena;
@@ -94,13 +94,24 @@ pub(crate) fn route_install<V>(
         let msg = LabelInstallMsg {
             protocol: V::PROTOCOL,
             label: *sr_label,
-            nexthops,
+            nexthops: nexthops.clone(),
             route: None,
             replace: true,
         };
         let msg = IbusMsg::RouteMplsAdd(msg);
         let _ = ibus_tx.send(msg);
     }
+
+    // Install BIER neighbor entry
+    if let Some(bier_info) = &route.bier_info {
+        let msg = BierNbrInstallMsg {
+            bier_info: bier_info.clone(),
+            nexthops,
+            prefix: (*destination).into(),
+        };
+        let msg = IbusMsg::RouteBierAdd(msg);
+        let _ = ibus_tx.send(msg);
+    }
 }
 
 pub(crate) fn route_uninstall<V>(
diff --git a/holo-ospf/src/spf.rs b/holo-ospf/src/spf.rs
index 52a2a5bc..482f0051 100644
--- a/holo-ospf/src/spf.rs
+++ b/holo-ospf/src/spf.rs
@@ -24,7 +24,7 @@ use crate::interface::Interface;
 use crate::lsdb::{LsaEntry, LsaLogId};
 use crate::neighbor::Neighbor;
 use crate::packet::lsa::{Lsa, LsaKey};
-use crate::packet::tlv::{SidLabelRangeTlv, SrAlgoTlv};
+use crate::packet::tlv::{BierSubTlv, SidLabelRangeTlv, SrAlgoTlv};
 use crate::route::{Nexthops, PathType, RouteRtr};
 use crate::version::Version;
 use crate::{area, route, tasks};
@@ -73,6 +73,7 @@ pub struct SpfIntraAreaNetwork<'a, V: Version> {
     pub prefix_options: V::PrefixOptions,
     pub metric: u16,
     pub prefix_sids: BTreeMap<IgpAlgoType, V::PrefixSid>,
+    pub bier: Vec<BierSubTlv>,
 }
 
 #[derive(Debug)]
diff --git a/holo-ospf/tests/packet/ospfv3.rs b/holo-ospf/tests/packet/ospfv3.rs
index 3ab312e0..c8ff1f3c 100644
--- a/holo-ospf/tests/packet/ospfv3.rs
+++ b/holo-ospf/tests/packet/ospfv3.rs
@@ -610,6 +610,7 @@ static LSA2: Lazy<(Vec<u8>, Lsa<Ospfv3>)> = Lazy::new(|| {
                     value: IpNetwork::from_str("2.2.2.2/32").unwrap(),
                     metric: 0,
                     prefix_sids: Default::default(),
+                    bier: vec![],
                     unknown_stlvs: vec![],
                 }],
                 unknown_tlvs: vec![],
@@ -892,6 +893,7 @@ static EXT_INTRA_AREA_PREFIX_LSA1: Lazy<(Vec<u8>, Lsa<Ospfv3>)> =
                                 }
                             }
                         },
+                        bier: vec![],
                         unknown_stlvs: vec![],
                     }],
                     unknown_tlvs: vec![],
diff --git a/holo-routing/src/ibus.rs b/holo-routing/src/ibus.rs
index 68da25ad..b589f2aa 100644
--- a/holo-routing/src/ibus.rs
+++ b/holo-routing/src/ibus.rs
@@ -95,6 +95,9 @@ pub(crate) fn process_msg(master: &mut Master, msg: IbusMsg) {
                 .rib
                 .redistribute_request(protocol, af, &master.ibus_tx);
         }
+        IbusMsg::RouteBierAdd(msg) => {
+            master.birt.bier_nbr_add(msg);
+        }
         // Ignore other events.
         _ => {}
     }
diff --git a/holo-routing/src/lib.rs b/holo-routing/src/lib.rs
index b7d769b3..31f0bbb2 100644
--- a/holo-routing/src/lib.rs
+++ b/holo-routing/src/lib.rs
@@ -30,7 +30,7 @@ use tokio::sync::mpsc;
 use tracing::Instrument;
 
 use crate::northbound::configuration::StaticRoute;
-use crate::rib::Rib;
+use crate::rib::{Birt, Rib};
 
 pub struct Master {
     // Northbound Tx channel.
@@ -53,6 +53,8 @@ pub struct Master {
     pub bier_config: BierCfg,
     // Protocol instances.
     pub instances: BTreeMap<InstanceId, NbDaemonSender>,
+    // BIER Routing Table (BIRT)
+    pub birt: Birt,
 }
 
 #[derive(Debug, Eq, Hash, PartialEq, PartialOrd, new, Ord)]
@@ -134,6 +136,7 @@ pub fn start(
             sr_config: Default::default(),
             bier_config: Default::default(),
             instances: Default::default(),
+            birt: Default::default(),
         };
 
         // Request information about all interfaces addresses.
diff --git a/holo-routing/src/northbound/mod.rs b/holo-routing/src/northbound/mod.rs
index dee0f4bd..c8b6ef88 100644
--- a/holo-routing/src/northbound/mod.rs
+++ b/holo-routing/src/northbound/mod.rs
@@ -30,6 +30,7 @@ impl ProviderBase for Master {
             "ietf-segment-routing-common",
             "ietf-segment-routing-mpls",
             "ietf-bier",
+            "holo-routing",
         ]
     }
 
diff --git a/holo-routing/src/northbound/state.rs b/holo-routing/src/northbound/state.rs
index 68cfd1be..753b4958 100644
--- a/holo-routing/src/northbound/state.rs
+++ b/holo-routing/src/northbound/state.rs
@@ -14,8 +14,9 @@ use holo_northbound::state::{
     Callbacks, CallbacksBuilder, ListEntryKind, Provider,
 };
 use holo_northbound::yang::control_plane_protocol;
-use holo_northbound::yang::routing::ribs;
+use holo_northbound::yang::routing::{birts, ribs};
 use holo_northbound::{CallbackKey, NbDaemonSender};
+use holo_utils::bier::{BfrId, Bsl};
 use holo_utils::mpls::Label;
 use holo_utils::protocol::Protocol;
 use holo_utils::southbound::{Nexthop, RouteOpaqueAttrs};
@@ -37,6 +38,12 @@ pub enum ListEntry<'a> {
     Route(RouteDestination<'a>, &'a Route),
     Nexthop(&'a Nexthop),
     Label((usize, &'a Label)),
+    SubDomainId(u8),
+    BfrId(BfrId),
+    // FIXME: Should be Bsl but issue with yang-rs
+    Bsl(u8),
+    BirtEntry((u8, IpAddr, IpAddr)),
+    BirtKey((u8, u16, Bsl)),
 }
 
 #[derive(Debug)]
@@ -279,6 +286,54 @@ fn load_callbacks() -> Callbacks<Master> {
                 label: Some(label.to_yang()),
             })
         })
+        .path(birts::birt::PATH)
+        .get_iterate(|master, _args| {
+            let iter = master.birt.entries.keys().map(|(sd_id, _bfr_id, _bsl)| ListEntry::SubDomainId(*sd_id));
+            Some(Box::new(iter))
+        })
+        .get_object(|_master, args| {
+            use birts::birt::Birt;
+            let sub_domain_id = args.list_entry.as_sub_domain_id().unwrap();
+            Box::new(Birt{sub_domain_id: *sub_domain_id})
+        })
+        .path(birts::birt::bfr_id::PATH)
+        .get_iterate(|master, args| {
+            let sd_id_arg = *args.parent_list_entry.as_sub_domain_id().unwrap();
+            let iter = master.birt.entries.keys().filter_map(move |(sd_id, bfr_id, _bsl)| {
+                if *sd_id == sd_id_arg {
+                    Some(ListEntry::BfrId(*bfr_id))
+                } else {
+                    None
+                }
+            });
+            Some(Box::new(iter))
+        })
+        .get_object(|_master, args| {
+            use birts::birt::bfr_id::BfrId;
+            let bfr_id = args.list_entry.as_bfr_id().unwrap();
+            Box::new(BfrId{bfr_id: *bfr_id})
+        })
+        .path(birts::birt::bfr_id::birt_entry::PATH)
+        .get_iterate(|master, args| {
+            let bfr_id_arg = *args.parent_list_entry.as_bfr_id().unwrap();
+            let iter = master.birt.entries.keys().filter_map(move |(sd_id, bfr_id, bsl)| {
+                if *bfr_id == bfr_id_arg {
+                    Some(ListEntry::BirtKey((*sd_id, *bfr_id, *bsl)))
+                } else {
+                    None
+                }
+            });
+            Some(Box::new(iter))
+        })
+        .get_object(|master, args| {
+            use birts::birt::bfr_id::birt_entry::BirtEntry;
+            let birt_key = args.list_entry.as_birt_key().unwrap();
+            let birt_entry = master.birt.entries.get(birt_key).unwrap();
+            let bsl = birt_key.2;
+            let bfr_prefix = Some(Cow::Borrowed(&birt_entry.bfr_prefix));
+            let bfr_nbr = Some(Cow::Borrowed(&birt_entry.bfr_nbr));
+            Box::new(BirtEntry{bsl: bsl.into(), bfr_prefix, bfr_nbr})
+        })
         .build()
 }
 
diff --git a/holo-routing/src/rib.rs b/holo-routing/src/rib.rs
index 6ae9e15a..14d7c1aa 100644
--- a/holo-routing/src/rib.rs
+++ b/holo-routing/src/rib.rs
@@ -10,13 +10,14 @@ use std::net::IpAddr;
 use bitflags::bitflags;
 use chrono::{DateTime, Utc};
 use derive_new::new;
+use holo_utils::bier::{BfrId, BirtEntry, Bsl, SubDomainId};
 use holo_utils::ibus::IbusSender;
 use holo_utils::ip::{AddressFamily, IpNetworkExt, Ipv4AddrExt, Ipv6AddrExt};
 use holo_utils::mpls::Label;
 use holo_utils::protocol::Protocol;
 use holo_utils::southbound::{
-    AddressFlags, AddressMsg, LabelInstallMsg, LabelUninstallMsg, Nexthop,
-    RouteKeyMsg, RouteMsg, RouteOpaqueAttrs,
+    AddressFlags, AddressMsg, BierNbrInstallMsg, LabelInstallMsg,
+    LabelUninstallMsg, Nexthop, RouteKeyMsg, RouteMsg, RouteOpaqueAttrs,
 };
 use holo_utils::{UnboundedReceiver, UnboundedSender};
 use ipnetwork::{IpNetwork, Ipv4Network, Ipv6Network};
@@ -38,6 +39,11 @@ pub struct Rib {
     pub update_queue_rx: UnboundedReceiver<()>,
 }
 
+#[derive(Debug, Default)]
+pub struct Birt {
+    pub entries: BTreeMap<(SubDomainId, BfrId, Bsl), BirtEntry>,
+}
+
 #[derive(Clone, Debug, new)]
 pub struct Route {
     pub protocol: Protocol,
@@ -58,6 +64,27 @@ bitflags! {
     }
 }
 
+// ===== impl Birt =====
+
+impl Birt {
+    pub(crate) fn bier_nbr_add(&mut self, msg: BierNbrInstallMsg) {
+        let bfr_id = msg.bier_info.bfr_id;
+        msg.bier_info.bfr_bss.iter().for_each(|bsl| {
+            if let Some(nexthop) = msg.nexthops.first()
+                && let Nexthop::Address { addr, .. } = nexthop
+            {
+                self.entries
+                    .entry((msg.bier_info.sd_id, bfr_id, *bsl))
+                    .and_modify(|be| be.bfr_nbr = *addr)
+                    .or_insert(BirtEntry {
+                        bfr_prefix: msg.prefix.ip(),
+                        bfr_nbr: (*addr),
+                    });
+            }
+        });
+    }
+}
+
 // ===== impl Rib =====
 
 impl Rib {
diff --git a/holo-utils/src/bier.rs b/holo-utils/src/bier.rs
index 4ae33fac..7420a767 100644
--- a/holo-utils/src/bier.rs
+++ b/holo-utils/src/bier.rs
@@ -6,7 +6,9 @@
 
 use std::borrow::Cow;
 use std::collections::{BTreeMap, HashMap};
+use std::net::IpAddr;
 
+use bytes::BytesMut;
 use derive_new::new;
 use holo_yang::{ToYang, TryFromYang};
 use ipnetwork::IpNetwork;
@@ -17,6 +19,20 @@ use crate::ip::AddressFamily;
 pub type SubDomainId = u8;
 pub type BfrId = u16;
 
+#[derive(Clone, Debug, Default, Eq, PartialEq)]
+#[derive(Deserialize, Serialize)]
+pub struct BierInfo {
+    pub sd_id: SubDomainId,
+    pub bfr_id: BfrId,
+    pub bfr_bss: Vec<Bsl>,
+}
+
+#[derive(Debug)]
+pub struct BirtEntry {
+    pub bfr_prefix: IpAddr,
+    pub bfr_nbr: IpAddr,
+}
+
 #[derive(Clone, Debug, Default, Eq, PartialEq)]
 #[derive(Deserialize, Serialize)]
 pub struct BiftId(u32);
@@ -113,6 +129,81 @@ pub enum Bsl {
     _4096,
 }
 
+impl From<Bsl> for usize {
+    fn from(val: Bsl) -> Self {
+        match val {
+            Bsl::_64 => 64,
+            Bsl::_128 => 128,
+            Bsl::_256 => 256,
+            Bsl::_512 => 512,
+            Bsl::_1024 => 1024,
+            Bsl::_2048 => 2048,
+            Bsl::_4096 => 4096,
+        }
+    }
+}
+
+impl From<Bsl> for u8 {
+    // Mapping defined in RFC8296, Section 2.1.2
+    fn from(val: Bsl) -> Self {
+        match val {
+            Bsl::_64 => 1,
+            Bsl::_128 => 2,
+            Bsl::_256 => 3,
+            Bsl::_512 => 4,
+            Bsl::_1024 => 5,
+            Bsl::_2048 => 6,
+            Bsl::_4096 => 7,
+        }
+    }
+}
+
+impl TryFrom<u8> for Bsl {
+    type Error = &'static str;
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        match value {
+            1 => Ok(Self::_64),
+            2 => Ok(Self::_128),
+            3 => Ok(Self::_256),
+            4 => Ok(Self::_512),
+            5 => Ok(Self::_1024),
+            6 => Ok(Self::_2048),
+            7 => Ok(Self::_4096),
+            _ => Err("Not Supported"),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, PartialOrd, Eq, Ord, Clone)]
+#[derive(Serialize, Deserialize)]
+pub struct Bitstring {
+    bsl: Bsl,
+    bs: BytesMut,
+}
+
+impl Bitstring {
+    pub fn new(bsl: Bsl) -> Self {
+        Self {
+            bsl,
+            bs: BytesMut::zeroed(bsl.into()),
+        }
+    }
+
+    pub fn from(id: BfrId, bsl: Bsl) -> Self {
+        // pub fn from(bfr: BfrId) -> Self {
+        // TODO: Ensure value fit in bitstring and use SI if required.
+        let byte = id / 8;
+        let idx = (id % 8) + 1;
+        let mut bs = Self::new(bsl);
+        bs.bs[byte as usize] |= 1 << idx;
+        bs
+    }
+
+    pub fn bsl(&self) -> Bsl {
+        self.bsl
+    }
+}
+
 // ===== YANG impl =====
 
 impl TryFromYang for UnderlayProtocolType {
@@ -141,33 +232,16 @@ impl TryFromYang for Bsl {
     }
 }
 
-impl Into<u8> for Bsl {
-    // Mapping defined in RFC8296, Section 2.1.2
-    fn into(self) -> u8 {
+impl ToYang for Bsl {
+    fn to_yang(&self) -> Cow<'static, str> {
         match self {
-            Self::_64 => 1,
-            Self::_128 => 2,
-            Self::_256 => 3,
-            Self::_512 => 4,
-            Self::_1024 => 5,
-            Self::_2048 => 6,
-            Self::_4096 => 7,
-        }
-    }
-}
-
-impl TryFrom<u8> for Bsl {
-    type Error = &'static str;
-    fn try_from(value: u8) -> Result<Self, Self::Error> {
-        match value {
-            1 => Ok(Self::_64),
-            2 => Ok(Self::_128),
-            3 => Ok(Self::_256),
-            4 => Ok(Self::_512),
-            5 => Ok(Self::_1024),
-            6 => Ok(Self::_2048),
-            7 => Ok(Self::_4096),
-            _ => Err("Not Supported"),
+            Bsl::_64 => "64-bit".into(),
+            Bsl::_128 => "128-bit".into(),
+            Bsl::_256 => "256-bit".into(),
+            Bsl::_512 => "512-bit".into(),
+            Bsl::_1024 => "1024-bit".into(),
+            Bsl::_2048 => "2048-bit".into(),
+            Bsl::_4096 => "4096-bit".into(),
         }
     }
 }
diff --git a/holo-utils/src/ibus.rs b/holo-utils/src/ibus.rs
index 986723c7..4c146157 100644
--- a/holo-utils/src/ibus.rs
+++ b/holo-utils/src/ibus.rs
@@ -17,8 +17,8 @@ use crate::keychain::Keychain;
 use crate::policy::{MatchSets, Policy};
 use crate::protocol::Protocol;
 use crate::southbound::{
-    AddressMsg, InterfaceUpdateMsg, LabelInstallMsg, LabelUninstallMsg,
-    RouteKeyMsg, RouteMsg,
+    AddressMsg, BierNbrInstallMsg, InterfaceUpdateMsg, LabelInstallMsg,
+    LabelUninstallMsg, RouteKeyMsg, RouteMsg,
 };
 use crate::sr::SrCfg;
 
@@ -112,6 +112,10 @@ pub enum IbusMsg {
     BierCfgUpd(Arc<BierCfg>),
     // BIER configuration event.
     BierCfgEvent(BierCfgEvent),
+    // Request to install an entry in the BIRT
+    RouteBierAdd(BierNbrInstallMsg),
+    // Request to uninstall an entry in the BIRT
+    RouteBierDel(),
 }
 
 // Type of Segment Routing configuration change.
diff --git a/holo-utils/src/southbound.rs b/holo-utils/src/southbound.rs
index 509a0b2c..2e56ca98 100644
--- a/holo-utils/src/southbound.rs
+++ b/holo-utils/src/southbound.rs
@@ -13,6 +13,7 @@ use holo_yang::{ToYang, TryFromYang};
 use ipnetwork::IpNetwork;
 use serde::{Deserialize, Serialize};
 
+use crate::bier::BierInfo;
 use crate::mpls::Label;
 use crate::protocol::Protocol;
 
@@ -101,6 +102,14 @@ pub struct RouteKeyMsg {
     pub prefix: IpNetwork,
 }
 
+#[derive(Clone, Debug)]
+#[derive(Deserialize, Serialize)]
+pub struct BierNbrInstallMsg {
+    pub bier_info: BierInfo,
+    pub nexthops: BTreeSet<Nexthop>,
+    pub prefix: IpNetwork,
+}
+
 #[derive(Clone, Debug)]
 #[derive(Deserialize, Serialize)]
 pub struct LabelInstallMsg {
diff --git a/holo-yang/modules/augmentations/holo-routing.yang b/holo-yang/modules/augmentations/holo-routing.yang
new file mode 100644
index 00000000..f0ef8049
--- /dev/null
+++ b/holo-yang/modules/augmentations/holo-routing.yang
@@ -0,0 +1,70 @@
+module holo-routing {
+  yang-version 1.1;
+  namespace "http://holo-routing.org/yang/holo-routing";
+  prefix holo-routing;
+
+  import ietf-inet-types {
+    prefix "inet";
+    reference "RFC 6991: Common YANG Data Types";
+  }
+
+  import ietf-routing {
+    prefix "rt";
+  }
+
+  import ietf-bier {
+    prefix "bier";
+  }
+
+  organization
+    "Holo Routing Stack";
+
+  description
+    "This module defines augment statements for the ietf-routing
+	module.";
+
+  augment "/rt:routing" {
+	container birts {
+		description "BIER routing tables";
+		list birt {
+			key "sub-domain-id";
+			description "BIER Routing table";
+			config false;
+			leaf sub-domain-id {
+				config false;
+				type uint8;
+				description "BIER sub-domain-id";
+			}
+			list bfr-id {
+				key "bfr-id";
+				config false;
+				leaf bfr-id {
+					config false;
+					type uint16;
+					description "BFR identifier";
+				}
+				list birt-entry {
+					key "bsl";
+					config false;
+					leaf bsl {
+						config false;
+						// FIXME: should be bier:bsl but got some issues with yang-rs
+						type uint8;
+						description "Bitstring length associated with the current entry";
+					}
+					leaf bfr-prefix {
+						config false;
+						type inet:ip-address;
+						description "BFR's prefix";
+					}
+					leaf bfr-nbr {
+						config false;
+						type inet:ip-address;
+						description "Neighbor BFR prefix";
+					}
+				}
+			}
+		}
+	}
+  }
+}
diff --git a/holo-yang/src/lib.rs b/holo-yang/src/lib.rs
index 49f837ef..cdddc8f9 100644
--- a/holo-yang/src/lib.rs
+++ b/holo-yang/src/lib.rs
@@ -132,6 +132,8 @@ pub static YANG_EMBEDDED_MODULES: Lazy<EmbeddedModules> = Lazy::new(|| {
             include_str!("../modules/augmentations/holo-ospf.yang"),
         EmbeddedModuleKey::new("holo-ospf-dev", None, None, None) =>
             include_str!("../modules/augmentations/holo-ospf-dev.yang"),
+        EmbeddedModuleKey::new("holo-routing", None, None, None) =>
+            include_str!("../modules/augmentations/holo-routing.yang"),
         // IETF Holo deviations
         EmbeddedModuleKey::new("holo-ietf-bgp-deviations", None, None, None) =>
             include_str!("../modules/deviations/holo-ietf-bgp-deviations.yang"),
@@ -218,6 +220,7 @@ pub static YANG_IMPLEMENTED_MODULES: Lazy<Vec<&'static str>> =
             "holo-bgp",
             "holo-ospf",
             "holo-ospf-dev",
+            "holo-routing",
         ]
     });