From faa3ce31998cdbdcb888132b0d38ee7a1e743682 Mon Sep 17 00:00:00 2001
From: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>
Date: Wed, 9 Apr 2025 17:58:20 +0200
Subject: [PATCH] fuzz: Avoid influence on the global RNG from peerman m_rng

This should avoid the remaining non-determistic code coverage paths.

Without this patch, the tool would report a diff (only when running
without libFuzzer):

cargo run --manifest-path ./contrib/devtools/deterministic-fuzz-coverage/Cargo.toml -- $PWD/bld-cmake/ $PWD/../qa-assets/fuzz_corpora/ p2p_headers_presync 32
---
 src/test/fuzz/p2p_headers_presync.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/test/fuzz/p2p_headers_presync.cpp b/src/test/fuzz/p2p_headers_presync.cpp
index 3a7146df8fe..b31b74ee4fe 100644
--- a/src/test/fuzz/p2p_headers_presync.cpp
+++ b/src/test/fuzz/p2p_headers_presync.cpp
@@ -32,6 +32,12 @@ public:
         PeerManager::Options peerman_opts;
         node::ApplyArgsManOptions(*m_node.args, peerman_opts);
         peerman_opts.max_headers_result = FUZZ_MAX_HEADERS_RESULTS;
+        // The peerman's rng is a global that is re-used, so it will be re-used
+        // and may cause non-determinism between runs. This may even influence
+        // the global RNG, because seeding may be done from the gloabl one. For
+        // now, avoid it influencing the global RNG, and initialize it with a
+        // constant instead.
+        peerman_opts.deterministic_rng = true;
         // No txs are relayed. Disable irrelevant and possibly
         // non-deterministic code paths.
         peerman_opts.ignore_incoming_txs = true;