Gate chanmon splice fuzz ops on cfg

Restore cfg(splicing) to the fuzz check-cfg allow list and gate
chanmon consistency splice opcodes on that cfg again. Without the
cfg, those inputs stop before executing splice-specific operations.

Author: joostjager

fuzz/Cargo.toml

@@ -43,5 +43,6 @@ check-cfg = [
     "cfg(fuzzing)",
     "cfg(secp256k1_fuzz)",
     "cfg(hashes_fuzz)",
+    "cfg(splicing)",
     "cfg(chacha20_poly1305_fuzz)"
 ]

fuzz/src/chanmon_consistency.rs

@@ -3610,35 +3610,59 @@ pub fn do_test<Out: Output + MaybeSend + MaybeSync>(data: &[u8], out: Out) {
 			},
 
 			0xa0 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[1].get_our_node_id();
 				harness.nodes[0].splice_in(&cp_node_id, &harness.chan_a_id());
 			},
 			0xa1 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[0].get_our_node_id();
 				harness.nodes[1].splice_in(&cp_node_id, &harness.chan_a_id());
 			},
 			0xa2 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[2].get_our_node_id();
 				harness.nodes[1].splice_in(&cp_node_id, &harness.chan_b_id());
 			},
 			0xa3 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[1].get_our_node_id();
 				harness.nodes[2].splice_in(&cp_node_id, &harness.chan_b_id());
 			},
 
 			0xa4 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[1].get_our_node_id();
 				harness.nodes[0].splice_out(&cp_node_id, &harness.chan_a_id());
 			},
 			0xa5 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[0].get_our_node_id();
 				harness.nodes[1].splice_out(&cp_node_id, &harness.chan_a_id());
 			},
 			0xa6 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[2].get_our_node_id();
 				harness.nodes[1].splice_out(&cp_node_id, &harness.chan_b_id());
 			},
 			0xa7 => {
+				if !cfg!(splicing) {
+					break 'fuzz_loop;
+				}
 				let cp_node_id = harness.nodes[1].get_our_node_id();
 				harness.nodes[2].splice_out(&cp_node_id, &harness.chan_b_id());
 			},