Merge #18044: Use wtxid for transaction relay

0a4f1422cd1c20e12a05d7ff1a2ef1d5e7c654bb Further improve comments around recentRejects (Suhas Daftuar)
0e20cfedb704c1f76bb727e2009867d3d503a03d Disconnect peers sending wtxidrelay message after VERACK (Suhas Daftuar)
cacd85209e20fc0fd08f86eed23b6ef93484ffcf test: Use wtxid relay generally in functional tests (Fabian Jahr)
8d8099e97ab8af2126f6fbd223fbd82c52f2e85e test: Add tests for wtxid tx relay in segwit test (Fabian Jahr)
9a5392fdf67f1c5c90f52d3cdb3dea4f35d1609f test: Update test framework p2p protocol version to 70016 (Fabian Jahr)
dd78d1d641178b473ab1156b71a837b9e686792b Rename AddInventoryKnown() to AddKnownTx() (Suhas Daftuar)
4eb515574e1012bc8ea5dafc3042dcdf4c766f26 Make TX_WITNESS_STRIPPED its own rejection reason (Suhas Daftuar)
97141ca442daea8fc9c307cf81a02b38dcc28fd8 Delay getdata requests from peers using txid-based relay (Suhas Daftuar)
46d78d47dea345329ba094310eec56ab00a02ddc Add p2p message "wtxidrelay" (Suhas Daftuar)
2d282e0cba9761574b6b43d134ca95f3052d7fd2 ignore non-wtxidrelay compliant invs (Anthony Towns)
ac88e2eb619821ad7ae1d45d4b40be69051d3999 Add support for tx-relay via wtxid (Suhas Daftuar)
8e68fc246d09f1e6c6dfa8c676969d97c2eb4334 Add wtxids to recentRejects instead of txids (Suhas Daftuar)
144c38582042c3b9ec53bb97ba0644fc0114f8fb Add wtxids of confirmed transactions to bloom filter (Suhas Daftuar)
85c78d54af462996a0bca6cf97f91e1aa8778ae8 Add wtxid-index to orphan map (Suhas Daftuar)
08b39955ec7f84e835ab0b1366f0dd28dfd6ce03 Add a wtxid-index to mapRelay (Suhas Daftuar)
60f0acda713e7b9dc188aef54ef93981a93f4e44 Just pass a hash to AddInventoryKnown (Suhas Daftuar)
c7eb6b4f1fe5bd76388a023529977674534334a7 Add wtxid to mempool unbroadcast tracking (Amiti Uttarwar)
2b4b90aa8f0440deacefb5997d7bd1f9f5c591b3 Add a wtxid-index to the mempool (Suhas Daftuar)

Pull request description:

  Using txids (a transaction's hash, without witness) for transaction relay is problematic, post-segwit -- if a peer gives us a segwit transaction that fails policy checks, it could be because the txid associated with the transaction is definitely unacceptable to our node (regardless of the witness), or it could be that the transaction was malleated and with a different witness, the txid could be accepted to our mempool.

  We have a bloom filter of recently rejected transactions, whose purpose is to help us avoid redownloading and revalidating transactions that fail to be accepted, but because of this potential for witness malleability to interfere with relay of valid transactions, we do not use the filter for segwit transactions.  This issue is discussed at some length in #8279.  The effect of this is that whenever a segwit transaction that fails policy checks is relayed, a node would download that transaction from every peer announcing it, because it has no way presently to cache failure.  Historically this hasn't been a big problem, but if/when policy for accepting segwit transactions were to change (eg taproot, or any other change), we could expect older nodes talking to newer nodes to be wasting bandwidth because of this.

  As discussed in that issue, switching to wtxid-based relay solves this problem -- by using an identifier for a transaction that commits to all the data in our relay protocol, we can be certain if a transaction that a peer is announcing is one that we've already tried to process, or if it's something new.  This PR introduces support for wtxid-based relay with peers that support it (and remains backwards compatible with peers that use txids for relay, of course).

  Apart from code correctness, one issue to be aware of is that by downloading from old and new peers alike, we should expect there to be some bandwidth wasted, because sometimes we might download the same transaction via txid-relay as well as wtxid-relay.  The last commit in this PR implements a heuristic I want to analyze, which is to just delay relay from txid-relay peers by 2 seconds, if we have at least 1 wtxid-based peer.  I've just started running a couple nodes with this heuristic so I can measure how well it works, but I'm open to other ideas for minimizing that issue.  In the long run, I think this will be essentially a non-issue, so I don't think it's too big a concern, we just need to bite the bullet and deal with it during upgrade.

  Finally, this proposal would need a simple BIP describing the changes, which I haven't yet drafted.  However, review and testing of this code in the interim would be welcome.

  To do items:
  - [x] Write BIP explaining the spec here (1 new p2p message for negotiating wtxid-based relay, along with a new INV type)
  - [ ] Measure and evaluate a heuristic for minimizing how often a node downloads the same transaction twice, when connected to old and new nodes.

ACKs for top commit:
  naumenkogs:
    utACK 0a4f1422cd1c20e12a05d7ff1a2ef1d5e7c654bb
  laanwj:
    utACK 0a4f1422cd1c20e12a05d7ff1a2ef1d5e7c654bb

Tree-SHA512: d8eb8f0688cf0cbe9507bf738e143edab1f595551fdfeddc2b6734686ea26e7f156b6bfde38bad8bbbe8bec1857c7223e1687f8f018de7463dde8ecaa8f450df

1 files changed, 5 insertions, 1 deletions

diff --git a/src/consensus/validation.h b/src/consensus/validation.h
index 74d6138041..8de7a8f2d8 100644
--- a/src/consensus/validation.h
+++ b/src/consensus/validation.h
@@ -30,12 +30,16 @@ enum class TxValidationResult {
     TX_MISSING_INPUTS,        //!< transaction was missing some of its inputs
     TX_PREMATURE_SPEND,       //!< transaction spends a coinbase too early, or violates locktime/sequence locks
     /**
-     * Transaction might be missing a witness, have a witness prior to SegWit
+     * Transaction might have a witness prior to SegWit
      * activation, or witness may have been malleated (which includes
      * non-standard witnesses).
      */
     TX_WITNESS_MUTATED,
     /**
+     * Transaction is missing a witness.
+     */
+    TX_WITNESS_STRIPPED,
+    /**
      * Tx already in mempool or conflicts with a tx in the chain
      * (if it conflicts with another tx in mempool, we use MEMPOOL_POLICY as it failed to reach the RBF threshold)
      * Currently this is only used if the transaction already exists in the mempool or on chain.