caches Merkle shreds signature verifications (solana-labs#230)

Merkle shreds sign the Merkle root of the erasure batch, so all shreds
within the same erasure batch have the same signature. The commit
improves shreds signature verification by adding an LRU cache.

Cargo.toml

@@ -238,6 +238,7 @@ jsonrpc-derive = "18.0.0"
 jsonrpc-http-server = "18.0.0"
 jsonrpc-ipc-server = "18.0.0"
 jsonrpc-pubsub = "18.0.0"
+lazy-lru = "0.1.2"
 lazy_static = "1.4.0"
 libc = "0.2.153"
 libloading = "0.7.4"

core/src/repair/repair_response.rs

@@ -55,7 +55,7 @@ mod test {
         super::*,
         solana_ledger::{
             shred::{Shred, ShredFlags},
-            sigverify_shreds::verify_shred_cpu,
+            sigverify_shreds::{verify_shred_cpu, LruCache},
         },
         solana_sdk::{
             packet::PacketFlags,
@@ -64,11 +64,13 @@ mod test {
         std::{
             collections::HashMap,
             net::{IpAddr, Ipv4Addr},
+            sync::RwLock,
         },
     };
 
     fn run_test_sigverify_shred_cpu_repair(slot: Slot) {
         solana_logger::setup();
+        let cache = RwLock::new(LruCache::new(/*capacity:*/ 128));
         let mut shred = Shred::new_from_data(
             slot,
             0xc0de,
@@ -93,14 +95,14 @@ mod test {
         packet.meta_mut().flags |= PacketFlags::REPAIR;
 
         let leader_slots = HashMap::from([(slot, keypair.pubkey())]);
-        assert!(verify_shred_cpu(&packet, &leader_slots));
+        assert!(verify_shred_cpu(&packet, &leader_slots, &cache));
 
         let wrong_keypair = Keypair::new();
         let leader_slots = HashMap::from([(slot, wrong_keypair.pubkey())]);
-        assert!(!verify_shred_cpu(&packet, &leader_slots));
+        assert!(!verify_shred_cpu(&packet, &leader_slots, &cache));
 
         let leader_slots = HashMap::new();
-        assert!(!verify_shred_cpu(&packet, &leader_slots));
+        assert!(!verify_shred_cpu(&packet, &leader_slots, &cache));
     }
 
     #[test]

ledger/Cargo.toml

@@ -22,6 +22,7 @@ eager = { workspace = true }
 fs_extra = { workspace = true }
 futures = { workspace = true }
 itertools = { workspace = true }
+lazy-lru = { workspace = true }
 lazy_static = { workspace = true }
 libc = { workspace = true }
 log = { workspace = true }