uses enum for shred type (backport #21333) (#22147)

* uses enum for shred type

Current code is using u8 which does not have any type-safety and can
contain invalid values:
https://github.com/solana-labs/solana/blob/66fa062f1/ledger/src/shred.rs#L167

Checks for invalid shred-types are scattered through the code:
https://github.com/solana-labs/solana/blob/66fa062f1/ledger/src/blockstore.rs#L849-L851
https://github.com/solana-labs/solana/blob/66fa062f1/ledger/src/shred.rs#L346-L348

The commit uses enum for shred type with #[repr(u8)]. Backward
compatibility is maintained by implementing Serialize and Deserialize
compatible with u8, and adding a test to assert that.

(cherry picked from commit 57057f8d39)

# Conflicts:
#	core/src/retransmit_stage.rs
#	gossip/src/cluster_info.rs
#	ledger/Cargo.toml
#	ledger/src/blockstore.rs
#	ledger/src/shred.rs

* changes Blockstore::is_shred_duplicate arg type to ShredType

(cherry picked from commit 48dfdfb4d5)

# Conflicts:
#	ledger/src/blockstore.rs

* removes backport merge conflicts

Co-authored-by: behzad nouri <behzadnouri@gmail.com>

core/src/retransmit_stage.rs

@@ -18,7 +18,9 @@ use {
     solana_client::rpc_response::SlotUpdate,
     solana_gossip::cluster_info::{ClusterInfo, DATA_PLANE_FANOUT},
     solana_ledger::{
-        blockstore::Blockstore, leader_schedule_cache::LeaderScheduleCache, shred::Shred,
+        blockstore::Blockstore,
+        leader_schedule_cache::LeaderScheduleCache,
+        shred::{Shred, ShredType},
     },
     solana_measure::measure::Measure,
     solana_perf::packet::PacketBatch,
@@ -137,14 +139,14 @@ impl RetransmitStats {
     }
 }
 
-// Map of shred (slot, index, is_data) => list of hash values seen for that key.
-type ShredFilter = LruCache<(Slot, u32, bool), Vec<u64>>;
+// Map of shred (slot, index, type) => list of hash values seen for that key.
+type ShredFilter = LruCache<(Slot, u32, ShredType), Vec<u64>>;
 
 type ShredFilterAndHasher = (ShredFilter, PacketHasher);
 
 // Returns true if shred is already received and should skip retransmit.
 fn should_skip_retransmit(shred: &Shred, shreds_received: &Mutex<ShredFilterAndHasher>) -> bool {
-    let key = (shred.slot(), shred.index(), shred.is_data());
+    let key = (shred.slot(), shred.index(), shred.shred_type());
     let mut shreds_received = shreds_received.lock().unwrap();
     let (cache, hasher) = shreds_received.deref_mut();
     match cache.get_mut(&key) {

core/src/window_service.rs

@@ -18,7 +18,7 @@ use {
     solana_ledger::{
         blockstore::{self, Blockstore, BlockstoreInsertionMetrics, MAX_DATA_SHREDS_PER_SLOT},
         leader_schedule_cache::LeaderScheduleCache,
-        shred::{Nonce, Shred},
+        shred::{Nonce, Shred, ShredType},
     },
     solana_measure::measure::Measure,
     solana_metrics::{inc_new_counter_debug, inc_new_counter_error},
@@ -161,12 +161,11 @@ impl ReceiveWindowStats {
 }
 
 fn verify_shred_slot(shred: &Shred, root: u64) -> bool {
-    if shred.is_data() {
+    match shred.shred_type() {
         // Only data shreds have parent information
-        blockstore::verify_shred_slots(shred.slot(), shred.parent(), root)
-    } else {
+        ShredType::Data => blockstore::verify_shred_slots(shred.slot(), shred.parent(), root),
         // Filter out outdated coding shreds
-        shred.slot() >= root
+        ShredType::Code => shred.slot() >= root,
     }
 }
 
@@ -218,8 +217,8 @@ fn run_check_duplicate(
             if let Some(existing_shred_payload) = blockstore.is_shred_duplicate(
                 shred_slot,
                 shred.index(),
-                &shred.payload,
-                shred.is_data(),
+                shred.payload.clone(),
+                shred.shred_type(),
             ) {
                 cluster_info.push_duplicate_shred(&shred, &existing_shred_payload)?;
                 blockstore.store_duplicate_slot(