Merge bitcoin/bitcoin#28428: Hard-code version number value for CBlockLocator and CDiskBlockIndex

e73d2a8018def940afadb5d699b18f39e882c1fc refactor: remove clientversion include from dbwrapper.h (Cory Fields)
4240a082b81d8ceb7615b1b4ca0d2857382f317b refactor: Use DataStream now that version/type are unused (Cory Fields)
f15f790618d328abd207d55e6291229eb2a8643f Remove version/hashing options from CBlockLocator/CDiskBlockIndex (Cory Fields)

Pull request description:

  This is also a much simpler replacement for #28327.

  There are version fields in `CBlockLocator` and `CDiskBlockIndex` that have always been written but discarded when read.

  I intended to convert them to use SerParams as introduced by #25284, which [ended up looking like this](https://github.com/theuni/bitcoin/commit/3e3af451652322c92e8e41cf918e69d608ec7c77). However because we don't currently have any definition of what a hash value would mean for either one of those, and we've never assigned the version field any meaning, I think it's better to just not worry about them.

  If we ever need to assign meaning in the future, we can introduce `SerParams` as was done for `CAddress`.

  As for the dummy values chosen:

  `CDiskBlockIndex::DUMMY_VERSION` was easy as the highest ever client version, and I don't expect any objection there.

  `CBlockLocator::DUMMY_VERSION` is hard-coded to the higest _PROTOCOL_ version ever used. This is to avoid a sudden bump that would be visible on the network if CLIENT_VERSION were used instead. In the future, if we ever need to use the value, we can discard anything in the CLIENT_VERSION range (for a few years as needed), as it's quite a bit higher.

  While reviewing, I suggest looking at the throwaway `SerParams` commit above as it shows where the call-sites are. I believe that should be enough to convince one's self that hashing is never used.

ACKs for top commit:
  TheCharlatan:
    Re-ACK e73d2a8018def940afadb5d699b18f39e882c1fc
  ajtowns:
    reACK e73d2a8018def940afadb5d699b18f39e882c1fc

Tree-SHA512: 45b0dd7c2e918493e2ee92a8e35320ad17991cb8908cb811150a96c5fd584ce177c775baeeb8675a602c90b9ba9203b8cefc0a2a0c6a71078b1d9c2b41e1f3ba

1 files changed, 11 insertions, 3 deletions

diff --git a/src/primitives/block.h b/src/primitives/block.h
index 861d362414..99accfc7dd 100644
--- a/src/primitives/block.h
+++ b/src/primitives/block.h
@@ -118,6 +118,15 @@ public:
  */
 struct CBlockLocator
 {
+    /** Historically CBlockLocator's version field has been written to network
+     * streams as the negotiated protocol version and to disk streams as the
+     * client version, but the value has never been used.
+     *
+     * Hard-code to the highest protocol version ever written to a network stream.
+     * SerParams can be used if the field requires any meaning in the future,
+     **/
+    static constexpr int DUMMY_VERSION = 70016;
+
     std::vector<uint256> vHave;
 
     CBlockLocator() {}
@@ -126,9 +135,8 @@ struct CBlockLocator
 
     SERIALIZE_METHODS(CBlockLocator, obj)
     {
-        int nVersion = s.GetVersion();
-        if (!(s.GetType() & SER_GETHASH))
-            READWRITE(nVersion);
+        int nVersion = DUMMY_VERSION;
+        READWRITE(nVersion);
         READWRITE(obj.vHave);
     }