Merge #13915: [qa] Add test for max number of entries in locator

fa85c985ed qa: Add p2p_invalid_locator test (MarcoFalke)

Pull request description:

  Should not be merged *before* #13907

Tree-SHA512: a67ca407854c421ed20a184d0b0dc90085aed3e3431d9652a107fa3022244767e67f67e50449b7e95721f56906836b134615875f28a21e8a012eb22cfe6a66a5

test/functional/test_framework/messages.py

@@ -32,6 +32,7 @@ MY_SUBVERSION = b"/python-mininode-tester:0.0.3/"
 MY_RELAY = 1 # from version 70001 onwards, fRelay should be appended to version messages (BIP37)
 
 MAX_INV_SZ = 50000
+MAX_LOCATOR_SZ = 101
 MAX_BLOCK_BASE_SIZE = 1000000
 
 COIN = 100000000  # 1 btc in satoshis

test/functional/test_framework/mininode.py

@@ -332,6 +332,15 @@ class P2PInterface(P2PConnection):
         test_function = lambda: self.last_message.get("block") and self.last_message["block"].block.rehash() == blockhash
         wait_until(test_function, timeout=timeout, lock=mininode_lock)
 
+    def wait_for_header(self, blockhash, timeout=60):
+        def test_function():
+            last_headers = self.last_message.get('headers')
+            if not last_headers:
+                return False
+            return last_headers.headers[0].rehash() == blockhash
+
+        wait_until(test_function, timeout=timeout, lock=mininode_lock)
+
     def wait_for_getdata(self, timeout=60):
         """Waits for a getdata message.