generate deterministic seeds for shreds (#17950)

* generate shred seed from leader pubkey

* clippy

* clippy

* review

* review 2

* fmt

* review

* check

* review

* cleanup

* fmt

ledger/src/shred.rs

@@ -65,15 +65,17 @@ use serde::{Deserialize, Serialize};
 use solana_measure::measure::Measure;
 use solana_perf::packet::{limited_deserialize, Packet};
 use solana_rayon_threadlimit::get_thread_count;
+use solana_runtime::bank::Bank;
 use solana_sdk::{
     clock::Slot,
+    feature_set,
+    hash::hashv,
     hash::Hash,
     packet::PACKET_DATA_SIZE,
     pubkey::Pubkey,
     signature::{Keypair, Signature, Signer},
 };
 use std::mem::size_of;
-
 use thiserror::Error;
 
 #[derive(Default, Clone)]
@@ -467,7 +469,18 @@ impl Shred {
         self.common_header.signature
     }
 
-    pub fn seed(&self) -> [u8; 32] {
+    pub fn seed(&self, leader_pubkey: Option<Pubkey>, root_bank: &Bank) -> [u8; 32] {
+        if let Some(leader_pubkey) = leader_pubkey {
+            if enable_deterministic_seed(self.slot(), root_bank) {
+                let h = hashv(&[
+                    &self.slot().to_le_bytes(),
+                    &self.index().to_le_bytes(),
+                    &leader_pubkey.to_bytes(),
+                ]);
+                return h.to_bytes();
+            }
+        }
+
         let mut seed = [0; 32];
         let seed_len = seed.len();
         let sig = self.common_header.signature.as_ref();
@@ -557,6 +570,21 @@ impl Shred {
     }
 }
 
+fn enable_deterministic_seed(shred_slot: Slot, bank: &Bank) -> bool {
+    let feature_slot = bank
+        .feature_set
+        .activated_slot(&feature_set::deterministic_shred_seed_enabled::id());
+    match feature_slot {
+        None => false,
+        Some(feature_slot) => {
+            let epoch_schedule = bank.epoch_schedule();
+            let feature_epoch = epoch_schedule.get_epoch(feature_slot);
+            let shred_epoch = epoch_schedule.get_epoch(shred_slot);
+            feature_epoch < shred_epoch
+        }
+    }
+}
+
 #[derive(Debug)]
 pub struct Shredder {
     pub slot: Slot,