fix: send votes to the immediate next leader

core/src/next_leader.rs

@@ -1,10 +1,40 @@
 use {
+    itertools::Itertools,
     solana_gossip::{cluster_info::ClusterInfo, contact_info::ContactInfo},
     solana_poh::poh_recorder::PohRecorder,
     solana_sdk::{clock::FORWARD_TRANSACTIONS_TO_LEADER_AT_SLOT_OFFSET, pubkey::Pubkey},
     std::{net::SocketAddr, sync::RwLock},
 };
 
+/// Returns a list of tpu vote sockets for the leaders of the next N fanout
+/// slots. Leaders are deduped but the resulting list could have duplicate
+/// sockets if two different leaders share the same tpu vote socket.
+pub(crate) fn upcoming_leader_tpu_vote_sockets(
+    cluster_info: &ClusterInfo,
+    poh_recorder: &RwLock<PohRecorder>,
+    fanout_slots: usize,
+) -> Vec<SocketAddr> {
+    let upcoming_leaders = {
+        let mut upcoming_leaders = Vec::with_capacity(fanout_slots);
+        let poh_recorder = poh_recorder.read().unwrap();
+        for n_slots in 1..=fanout_slots {
+            upcoming_leaders.push(poh_recorder.leader_after_n_slots(n_slots as u64));
+        }
+        upcoming_leaders
+    };
+
+    upcoming_leaders
+        .into_iter()
+        .flatten()
+        .unique()
+        .filter_map(|leader_pubkey| {
+            cluster_info
+                .lookup_contact_info(&leader_pubkey, ContactInfo::tpu_vote)?
+                .ok()
+        })
+        .collect()
+}
+
 pub(crate) fn next_leader_tpu_vote(
     cluster_info: &ClusterInfo,
     poh_recorder: &RwLock<PohRecorder>,

core/src/voting_service.rs

@@ -1,7 +1,7 @@
 use {
     crate::{
         consensus::tower_storage::{SavedTowerVersions, TowerStorage},
-        next_leader::next_leader_tpu_vote,
+        next_leader::upcoming_leader_tpu_vote_sockets,
     },
     crossbeam_channel::Receiver,
     solana_gossip::cluster_info::ClusterInfo,
@@ -78,12 +78,23 @@ impl VotingService {
             trace!("{measure}");
         }
 
-        let _ = cluster_info.send_transaction(
-            vote_op.tx(),
-            next_leader_tpu_vote(cluster_info, poh_recorder)
-                .map(|(_pubkey, target_addr)| target_addr),
+        // Attempt to send our vote transaction to the leaders for the next few slots
+        const UPCOMING_LEADER_FANOUT_SLOTS: usize = 2;
+        let upcoming_leader_sockets = upcoming_leader_tpu_vote_sockets(
+            cluster_info,
+            poh_recorder,
+            UPCOMING_LEADER_FANOUT_SLOTS,
         );
 
+        if !upcoming_leader_sockets.is_empty() {
+            for tpu_vote_socket in upcoming_leader_sockets {
+                let _ = cluster_info.send_transaction(vote_op.tx(), Some(tpu_vote_socket));
+            }
+        } else {
+            // Send to our own tpu vote socket if we cannot find a leader to send to
+            let _ = cluster_info.send_transaction(vote_op.tx(), None);
+        }
+
         match vote_op {
             VoteOp::PushVote {
                 tx, tower_slots, ..