fuzz-tests: Add a wire test for wireaddr functions

Changelog-None: `towire_wireaddr()` and `fromwire_wireaddr()` in
`common/wireaddr.h` are responsible for marshalling/unmarshalling
BOLT #7 address descriptors.

Since these aren't tested by the existing wire fuzz tests, add a
roundtrip test for them. This has the added benefit of testing
`parse_wireaddr()` as well.

Author: Chandra Pratap

tests/fuzz/fuzz-wireaddr.c

@@ -0,0 +1,42 @@
+#include "config.h"
+#include <assert.h>
+#include <bitcoin/chainparams.h>
+#include <ccan/ccan/tal/str/str.h>
+#include <common/setup.h>
+#include <common/utils.h>
+#include <common/wireaddr.h>
+#include <tests/fuzz/libfuzz.h>
+
+#define DEFAULT_PORT 9735
+
+void init(int *argc, char ***argv)
+{
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
+	chainparams = chainparams_for_network("bitcoin");
+}
+
+void run(const uint8_t *data, size_t size)
+{
+	char *addr = to_string(tmpctx, data, size);
+
+	struct wireaddr wa, decoded_wa;
+	const char *err;
+
+	err = parse_wireaddr(tmpctx, addr, DEFAULT_PORT, NULL, &wa);
+
+	if (!err) {
+		assert(fmt_wireaddr(tmpctx, &wa));
+
+		u8 *output_buffer = tal_arr(tmpctx, u8, 0);
+		towire_wireaddr(&output_buffer, &wa);
+		size_t len = tal_bytelen(output_buffer);
+
+		assert(fromwire_wireaddr((const u8 **)&output_buffer, &len,
+					 &decoded_wa));
+		assert(wireaddr_eq(&wa, &decoded_wa));
+	}
+
+	clean_tmpctx();
+}