Make TX_WITNESS_STRIPPED its own rejection reason

Previously, TX_WITNESS_MUTATED could be returned during transaction validation
for either transactions that had a witness that was non-standard, or for
transactions that had no witness but were invalid due to segwit validation
rules.

However, for txid/wtxid-relay considerations, net_processing distinguishes the
witness stripped case separately, because it affects whether a wtxid should be
able to be added to the reject filter. It is safe to add the wtxid of a
witness-mutated transaction to the filter (as that wtxid shouldn't collide with
the txid, and hence it wouldn't interfere with transaction relay from
txid-relay peers), but it is not safe to add the wtxid (== txid) of a
witness-stripped transaction to the filter, because that would interfere with
relay of another transaction with the same txid (but different wtxid) when
relaying from txid-relay peers.

Also updates the comment explaining this logic, and explaining that we can get
rid of this complexity once there's a sufficient deployment of wtxid-relaying
peers on the network.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/consensus/validation.h b/src/consensus/validation.h
index a79e7b9d12..337ee244d3 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.