Merge #21357: test: Unconditionally check for fRelay field in test framework

39a9ec579f Unconditionally check for fRelay field in test framework (Troy Giorshev)

Pull request description:

  picking up #20411 (rebased onto master)

  There is a discrepancy in the implementation of our p2p protocol between
  bitcoind and the testing framework.  The fRelay field is an optional
  field at the end of a version message as of protocol version 70001.
  However, when deserializing a message in bitcoind, we don't check the
  version to see if it should have an fRelay field or not.  Instead, we
  unconditionally attempt to deserialize into the field.

  This commit brings the testing framework in line with the implementation
  in core.

  This matters for a version message with the following fields:

  Version = 60000
  fRelay = 1

  Bitcoind would deserialize this into a version message with
  Version=60000 and fRelay=1, whereas (before this commit) our testing
  framework would deserialize this into a version message with
  Version=60000 and fRelay=0.

ACKs for top commit:
  jnewbery:
    utACK 39a9ec579f

Tree-SHA512: 13a23f1180b7121ba41cb85baa38094b41f4607a7c88b3384775177cb116e76faf5514760624f98a4e8a830767407c46753a7e0285158c33e0c6ce395de8f15c

test/functional/test_framework/messages.py

@@ -1045,13 +1045,11 @@ class msg_version:
 
         self.nStartingHeight = struct.unpack("<i", f.read(4))[0]
 
-        if self.nVersion >= 70001:
         # Relay field is optional for version 70001 onwards
+        # But, unconditionally check it to match behaviour in bitcoind
         try:
             self.relay = struct.unpack("<b", f.read(1))[0]
-            except:
-                self.relay = 0
-        else:
+        except struct.error:
             self.relay = 0
 
     def serialize(self):