From 2358ca7789f151c7ccdac61e647043cba275c825 Mon Sep 17 00:00:00 2001
From: Atishyy27 <sethatishayjain@gmail.com>
Date: Fri, 20 Mar 2026 02:44:22 +0530
Subject: [PATCH] fuzz: Add upgrade/downgrade simulation to chanmon_consistency
 and fix chacha20 build

---
 fuzz/src/chanmon_consistency.rs  | 16 +++++++++++++++-
 lightning/src/crypto/chacha20.rs |  2 ++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/fuzz/src/chanmon_consistency.rs b/fuzz/src/chanmon_consistency.rs
index 96104162db7..8871825d303 100644
--- a/fuzz/src/chanmon_consistency.rs
+++ b/fuzz/src/chanmon_consistency.rs
@@ -953,6 +953,15 @@ pub fn do_test<Out: Output + MaybeSend + MaybeSync>(
 		}};
 	}
 
+	let append_dummy_tlv = |ser: Vec<u8>, dummy_type: u64| -> Vec<u8> {
+		use lightning::util::ser::BigSize;
+		let mut writer = VecWriter(ser);
+		BigSize(dummy_type).write(&mut writer).unwrap();
+		BigSize(4).write(&mut writer).unwrap();
+		writer.0.extend_from_slice(&[0xde, 0xad, 0xbe, 0xef]);
+		writer.0
+	};
+
 	let reload_node = |ser: &Vec<u8>,
 	                   node_id: u8,
 	                   old_monitors: &TestChainMonitor,
@@ -1034,8 +1043,13 @@ pub fn do_test<Out: Output + MaybeSend + MaybeSync>(
 			channel_monitors: monitor_refs,
 		};
 
+		let mut modified_ser = ser.clone();
+		if use_old_mons % 2 == 0 {
+			modified_ser = append_dummy_tlv(modified_ser, 0xBADF00D1);
+		}
+
 		let manager =
-			<(BlockHash, ChanMan)>::read(&mut &ser[..], read_args).expect("Failed to read manager");
+			<(BlockHash, ChanMan)>::read(&mut &modified_ser[..], read_args).expect("Failed to read manager");
 		let res = (manager.1, chain_monitor.clone());
 		for (channel_id, mon) in monitors.drain() {
 			assert_eq!(
diff --git a/lightning/src/crypto/chacha20.rs b/lightning/src/crypto/chacha20.rs
index 67f9e93c480..ae4132a6194 100644
--- a/lightning/src/crypto/chacha20.rs
+++ b/lightning/src/crypto/chacha20.rs
@@ -334,6 +334,8 @@ mod fuzzy_chacha {
 		}
 
 		pub fn process_in_place(&mut self, _input_output: &mut [u8]) {}
+
+		pub fn seek_to_block(&mut self, _block_offset: u32) {}
 	}
 }
 #[cfg(fuzzing)]