Return validation options and fix gas validator (#553)

src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumChainSpecific.kt

@@ -155,15 +155,18 @@ object EthereumChainSpecific : AbstractPollChainSpecific() {
     ): List<SingleValidator<ValidateUpstreamSettingsResult>> {
         val limitValidator = callLimitValidatorFactory(upstream, options, config, chain)
 
-        return listOf(
+        val validators = mutableListOf(
             ChainIdValidator(upstream, chain),
             OldBlockValidator(upstream),
-            GasPriceValidator(upstream, config),
-        ) + if (limitValidator.isEnabled()) {
-            listOf(limitValidator)
-        } else {
-            emptyList()
+        )
+        if (limitValidator.isEnabled()) {
+            validators.add(limitValidator)
         }
+        if (options.validateGasPrice) {
+            validators.add(GasPriceValidator(upstream, config))
+        }
+
+        return validators
     }
 
     override fun chainSettingsValidator(

src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumUpstreamValidator.kt

@@ -267,6 +267,9 @@ class GasPriceValidator(
         val log: Logger = LoggerFactory.getLogger(GasPriceValidator::class.java)
     }
     override fun validate(onError: ValidateUpstreamSettingsResult): Mono<ValidateUpstreamSettingsResult> {
+        if (!upstream.getMethods().isCallable("eth_gasPrice")) {
+            return Mono.just(ValidateUpstreamSettingsResult.UPSTREAM_VALID)
+        }
         return upstream.getIngressReader()
             .read(ChainRequest("eth_gasPrice", ListParams()))
             .flatMap(ChainResponse::requireStringResult)