bgp: handle well-known communities during the route dissemination phase

For now, NO_EXPORT and NO_EXPORT_SUBCONFED are treated the same
since RFC 3065 isn't supported yet ("Autonomous System Confederations
for BGP").

Signed-off-by: Renato Westphal <[email protected]>

holo-bgp/src/events.rs

@@ -9,7 +9,7 @@ use std::net::IpAddr;
 
 use chrono::Utc;
 use holo_protocol::InstanceShared;
-use holo_utils::bgp::RouteType;
+use holo_utils::bgp::{RouteType, WellKnownCommunities};
 use holo_utils::ip::{IpAddrKind, IpNetworkKind};
 use holo_utils::policy::{PolicyResult, PolicyType};
 use holo_utils::socket::{TcpConnInfo, TcpStream};
@@ -728,6 +728,28 @@ pub(crate) fn advertise_routes<A>(
             return false;
         }
 
+        // Handle well-known communities.
+        if let Some(comm) = &route.attrs.comm {
+            for comm in comm
+                .value
+                .iter()
+                .filter_map(|comm| WellKnownCommunities::from_u32(comm.0))
+            {
+                // Do not advertise to any other peer.
+                if comm == WellKnownCommunities::NoAdvertise {
+                    return false;
+                }
+
+                // Do not advertise to external peers.
+                if nbr.peer_type == PeerType::External
+                    && (comm == WellKnownCommunities::NoExport
+                        || comm == WellKnownCommunities::NoExportSubconfed)
+                {
+                    return false;
+                }
+            }
+        }
+
         true
     });
 

holo-bgp/src/packet/attribute.rs

@@ -1400,6 +1400,10 @@ impl<T: CommType> CommList<T> {
     fn length(&self) -> u16 {
         ATTR_MIN_LEN_EXT + (self.0.len() * T::LENGTH) as u16
     }
+
+    pub(crate) fn iter(&self) -> impl Iterator<Item = &T> {
+        self.0.iter()
+    }
 }
 
 // ===== helper functions =====