Switch to hashbrown in fuzzing

hashbrown by default uses ahash, which may be a bit faster, but
more importantly, if we upgrade to hashbrown 0.13/ahash 0.8 we can
make it use a constant randomization factor, making fuzzers happier.

Author: TheBlueMatt

fuzz/Cargo.toml

@@ -18,11 +18,13 @@ libfuzzer_fuzz = ["libfuzzer-sys"]
 stdin_fuzz = []
 
 [dependencies]
-afl = { version = "0.12", optional = true }
-lightning = { path = "../lightning", features = ["regex"] }
+lightning = { path = "../lightning", features = ["regex", "hashbrown"] }
 lightning-rapid-gossip-sync = { path = "../lightning-rapid-gossip-sync" }
 bitcoin = { version = "0.29.0", features = ["secp-lowmemory"] }
 hex = "0.3"
+hashbrown = "0.8"
+
+afl = { version = "0.12", optional = true }
 honggfuzz = { version = "0.5", optional = true, default-features = false }
 libfuzzer-sys = { version = "0.4", optional = true }
 

fuzz/src/chanmon_consistency.rs

@@ -61,7 +61,7 @@ use bitcoin::secp256k1::Secp256k1;
 
 use std::mem;
 use std::cmp::{self, Ordering};
-use std::collections::{HashSet, hash_map, HashMap};
+use hashbrown::{HashSet, hash_map, HashMap};
 use std::sync::{Arc,Mutex};
 use std::sync::atomic;
 use std::io::Cursor;

fuzz/src/full_stack.rs

@@ -58,7 +58,7 @@ use bitcoin::secp256k1::ecdsa::RecoverableSignature;
 use bitcoin::secp256k1::Secp256k1;
 
 use std::cell::RefCell;
-use std::collections::{HashMap, hash_map};
+use hashbrown::{HashMap, hash_map};
 use std::convert::TryInto;
 use std::cmp;
 use std::sync::{Arc, Mutex};

fuzz/src/router.rs

@@ -29,7 +29,7 @@ use bitcoin::blockdata::constants::genesis_block;
 use crate::utils::test_logger;
 
 use std::convert::TryInto;
-use std::collections::HashSet;
+use hashbrown::HashSet;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};