Add the fixEnforceNFTokenTrustline amendment:

src/ripple/app/tx/impl/NFTokenAcceptOffer.cpp

@@ -270,6 +270,28 @@ NFTokenAcceptOffer::preclaim(PreclaimContext const& ctx)
  }
  }
 
+ // Fix a bug where the transfer of an NFToken with a transfer fee could
+ // give the NFToken issuer an undesired trust line.
+ if (ctx.view.rules().enabled(fixEnforceNFTokenTrustline))
+ {
+ std::shared_ptr<SLE const> const& offer = bo ? bo : so;
+ if (!offer)
+ // Should be caught in preflight.
+ return tecINTERNAL;
+
+ uint256 const& tokenID = offer->at(sfNFTokenID);
+ STAmount const& amount = offer->at(sfAmount);
+ if (nft::getTransferFee(tokenID) != 0 &&
+ (nft::getFlags(tokenID) & nft::flagCreateTrustLines) == 0 &&
+ !amount.native())
+ {
+ auto const issuer = nft::getIssuer(tokenID);
+ // Issuer doesn't need a trust line to accept their own currency.
+ if (issuer != amount.getIssuer() &&
+ !ctx.view.read(keylet::line(issuer, amount.issue())))
+ return tecNO_LINE;
+ }
+ }
  return tesSUCCESS;
 }
 

src/ripple/app/tx/impl/NFTokenCreateOffer.cpp

@@ -123,8 +123,19 @@ NFTokenCreateOffer::preclaim(PreclaimContext const& ctx)
  if (!ctx.view.exists(keylet::account(issuer)))
  return tecNO_ISSUER;
 
- if (!ctx.view.exists(keylet::line(issuer, amount.issue())))
+ // There was a bug in a corner case that fixEnforceNFTokenTrustline
+ // addresses. If the IOU issuer and the NFToken issuer are the same,
+ // then that issuer does not need a trust line to accept their fee.
+ if (ctx.view.rules().enabled(fixEnforceNFTokenTrustline))
+ {
+ if (issuer != amount.getIssuer() &&
+ !ctx.view.read(keylet::line(issuer, amount.issue())))
+ return tecNO_LINE;
+ }
+ else if (!ctx.view.exists(keylet::line(issuer, amount.issue())))
+ {
  return tecNO_LINE;
+ }
 
  if (isFrozen(
  ctx.view, issuer, amount.getCurrency(), amount.getIssuer()))

src/ripple/protocol/Feature.h

@@ -74,7 +74,7 @@ namespace detail {
 // Feature.cpp. Because it's only used to reserve storage, and determine how
 // large to make the FeatureBitset, it MAY be larger. It MUST NOT be less than
 // the actual number of amendments. A LogicError on startup will verify this.
-static constexpr std::size_t numFeatures = 68;
+static constexpr std::size_t numFeatures = 69;
 
 /** Amendments that this server supports and the default voting behavior.
  Whether they are enabled depends on the Rules defined in the validated
@@ -355,6 +355,7 @@ extern uint256 const fixFillOrKill;
 extern uint256 const fixNFTokenReserve;
 extern uint256 const fixInnerObjTemplate;
 extern uint256 const featurePriceOracle;
+extern uint256 const fixEnforceNFTokenTrustline;
 
 } // namespace ripple
 

src/ripple/protocol/impl/Feature.cpp

@@ -458,10 +458,11 @@ REGISTER_FEATURE(AMM, Supported::yes, VoteBehavior::De
 REGISTER_FEATURE(XChainBridge, Supported::yes, VoteBehavior::DefaultNo);
 REGISTER_FIX (fixDisallowIncomingV1, Supported::yes, VoteBehavior::DefaultNo);
 REGISTER_FEATURE(DID, Supported::yes, VoteBehavior::DefaultNo);
-REGISTER_FIX(fixFillOrKill, Supported::yes, VoteBehavior::DefaultNo);
+REGISTER_FIX (fixFillOrKill, Supported::yes, VoteBehavior::DefaultNo);
 REGISTER_FIX (fixNFTokenReserve, Supported::yes, VoteBehavior::DefaultNo);
-REGISTER_FIX(fixInnerObjTemplate, Supported::yes, VoteBehavior::DefaultNo);
+REGISTER_FIX (fixInnerObjTemplate, Supported::yes, VoteBehavior::DefaultNo);
 REGISTER_FEATURE(PriceOracle, Supported::yes, VoteBehavior::DefaultNo);
+REGISTER_FIX (fixEnforceNFTokenTrustline, Supported::yes, VoteBehavior::DefaultNo);
 
 // The following amendments are obsolete, but must remain supported
 // because they could potentially get enabled.