fuzz-tests: Add a wire test for wireaddr_internal

Changelog-None: Wire functions in `common/wireaddr.{c, h}` consume
untrusted input. Since no tests exist for these functions, add one
for the wire operations of `wireaddr_internal`.

Author: Chandra Pratap

tests/fuzz/fuzz-wire-wireaddr_internal.c

@@ -0,0 +1,42 @@
+#include "config.h"
+#include <assert.h>
+#include <ccan/ccan/tal/str/str.h>
+#include <common/utils.h>
+#include <common/setup.h>
+#include <common/wireaddr.h>
+#include <bitcoin/chainparams.h>
+#include <tests/fuzz/libfuzz.h>
+
+#define DEFAULT_PORT 9735
+
+void init(int *argc, char ***argv)
+{
+	common_setup("fuzzer");
+	chainparams = chainparams_for_network("bitcoin");
+}
+
+void run(const uint8_t *data, size_t size)
+{
+	char *addr = tal_arr(tmpctx, char, size + 1);
+	if (!addr)
+		return;
+	memcpy(addr, data, size);
+	addr[size] = '\0';
+
+	struct wireaddr_internal *wa = tal(tmpctx, struct wireaddr_internal);
+	const char *err;
+
+	err = parse_wireaddr_internal(tmpctx, addr, DEFAULT_PORT, NULL, wa);
+
+	if (!err) {
+		u8 *output_buffer = tal_arr(tmpctx, u8, 0);
+		towire_wireaddr_internal(&output_buffer, wa);
+		size_t len = tal_bytelen(output_buffer);
+
+		struct wireaddr_internal *decoded_wa = tal(tmpctx, struct wireaddr_internal);
+		assert(fromwire_wireaddr_internal((const u8 **) &output_buffer, &len, decoded_wa));
+		assert(wireaddr_internal_eq(wa, decoded_wa));
+	}
+
+	clean_tmpctx();
+}