rfq+taprpc: add 'public' oracle error flag

Adds a flag (defaulting to false) that indicates that the error returned
by a price oracle should be considered public, and can be safely
forwarded to peers. Updates proto definitions accordingly.

Author: jtobin

rfq/negotiator.go

@@ -556,6 +556,12 @@ func customRejectErr(err error) rfqmsg.RejectErr {
 		return rfqmsg.ErrUnknownReject
 	}
 
+	// If the price oracle has indicated that this error should not be
+	// forwarded to peers, then return an opaque rejection error.
+	if !oracleError.Public {
+		return rfqmsg.ErrUnknownReject
+	}
+
 	switch oracleError.Code {
 	// The price oracle has indicated that it doesn't support the asset,
 	// so return a rejection error indicating that.

rfq/oracle.go

@@ -89,6 +89,10 @@ type OracleError struct {
 	// Code is a code which uniquely identifies the error type.
 	Code OracleErrorCode
 
+	// Public is a flag that indicates the error can be relayed to
+	// peers.
+	Public bool
+
 	// Msg is a human-readable error message.
 	Msg string
 }
@@ -395,8 +399,9 @@ func (r *RpcPriceOracle) QuerySellPrice(ctx context.Context,
 
 		return &OracleResponse{
 			Err: &OracleError{
-				Msg:  result.Error.Message,
-				Code: marshallErrorCode(result.Error.Code),
+				Msg:    result.Error.Message,
+				Public: result.Error.Public,
+				Code:   marshallErrorCode(result.Error.Code),
 			},
 		}, nil
 

taprpc/priceoraclerpc/price_oracle.pb.go

@@ -238,8 +238,11 @@ message QueryAssetRatesErrResponse {
     // error is the error message.
     string message = 1;
 
+    // public is a flag indicating that the error can be forwarded to peers.
+    bool public = 2;
+
     // code is the error code.
-    ErrorCode code = 2;
+    ErrorCode code = 3;
 }
 
 // QueryAssetRatesResponse is the response from a QueryAssetRates RPC call.

taprpc/priceoraclerpc/price_oracle.proto

@@ -289,6 +289,10 @@
           "type": "string",
           "description": "error is the error message."
         },
+        "public": {
+          "type": "boolean",
+          "description": "public is a flag indicating that the error can be forwarded to peers."
+        },
         "code": {
           "$ref": "#/definitions/priceoraclerpcErrorCode",
           "description": "code is the error code."