R3NET-546: Improve the way CheckMembership operation is performed (#140)

samples/business-network-demo/src/main/kotlin/net/corda/sample/businessnetwork/Flow.kt

@@ -10,6 +10,8 @@ import net.corda.core.transactions.SignedTransaction
 import net.corda.core.transactions.TransactionBuilder
 import net.corda.core.utilities.ProgressTracker
 import net.corda.sample.businessnetwork.membership.MembershipAware
+import net.corda.sample.businessnetwork.membership.CheckMembershipFlow
+import net.corda.sample.businessnetwork.membership.CheckMembershipResult
 import kotlin.reflect.jvm.jvmName
 
 @InitiatingFlow
@@ -28,15 +30,12 @@ class IOUFlow(val iouValue: Int,
     /** The flow logic is encapsulated within the call() method. */
     @Suspendable
     override fun call(): SignedTransaction {
-
-        // Check whether the other party belongs to the membership list important for us.
-        otherParty.checkMembership(allowedMembershipName, this)
-
-        // Prior to creating any state - obtain consent from [otherParty] to borrow from us.
+        // Prior to creating any state, check on our side whether [otherParty] belongs to desired membership list.
+        // Also obtain consent from [otherParty] to borrow from us.
         // This is done early enough in the flow such that if the other party rejects - do not do any unnecessary processing in this flow.
         // Even if this is not done, later on upon signatures collection phase membership will be checked on the other side and
         // transaction rejected if this doesn't hold. See [IOUFlowResponder] for more information.
-        otherParty.checkSharesSameMembershipWithUs(allowedMembershipName, this)
+        check(subFlow(CheckMembershipFlow(otherParty, allowedMembershipName)) == CheckMembershipResult.PASS)
 
         // We retrieve the notary identity from the network map.
         val notary = serviceHub.networkMapCache.notaryIdentities[0]

samples/business-network-demo/src/main/kotlin/net/corda/sample/businessnetwork/FlowResponder.kt

@@ -7,13 +7,14 @@ import net.corda.core.flows.FlowSession
 import net.corda.core.flows.InitiatedBy
 import net.corda.core.flows.SignTransactionFlow
 import net.corda.core.transactions.SignedTransaction
-import net.corda.sample.businessnetwork.membership.CheckMembershipFlow
+import net.corda.sample.businessnetwork.membership.MembershipAware
 
 @InitiatedBy(IOUFlow::class)
-class IOUFlowResponder(val otherPartySession: FlowSession) : FlowLogic<Unit>() {
+class IOUFlowResponder(val otherPartySession: FlowSession) : FlowLogic<Unit>(), MembershipAware {
     @Suspendable
     override fun call() {
-        subFlow(CheckMembershipFlow(IOUFlow.allowedMembershipName, otherPartySession.counterparty))
+
+        otherPartySession.counterparty.checkMembership(IOUFlow.allowedMembershipName, this)
 
         subFlow(object : SignTransactionFlow(otherPartySession, SignTransactionFlow.tracker()) {
             override fun checkTransaction(stx: SignedTransaction) = requireThat {

samples/business-network-demo/src/main/kotlin/net/corda/sample/businessnetwork/membership/CheckMembershipFlow.kt

@@ -1,11 +1,38 @@
 package net.corda.sample.businessnetwork.membership
 
+import co.paralleluniverse.fibers.Suspendable
 import net.corda.core.flows.FlowLogic
-import net.corda.core.identity.AbstractParty
+import net.corda.core.flows.FlowSession
+import net.corda.core.flows.InitiatedBy
+import net.corda.core.flows.InitiatingFlow
 import net.corda.core.identity.CordaX500Name
+import net.corda.core.identity.Party
+import net.corda.core.serialization.CordaSerializable
+import net.corda.core.utilities.unwrap
 
-class CheckMembershipFlow(private val membershipName: CordaX500Name, private val counterParty: AbstractParty) : FlowLogic<Unit>(), MembershipAware {
-    override fun call() {
-        counterParty.checkMembership(membershipName, this)
+@CordaSerializable
+enum class CheckMembershipResult {
+    PASS,
+    FAIL
+}
+
+@InitiatingFlow
+class CheckMembershipFlow(private val otherParty: Party, private val membershipName: CordaX500Name) : FlowLogic<CheckMembershipResult>(), MembershipAware {
+    @Suspendable
+    override fun call(): CheckMembershipResult {
+        otherParty.checkMembership(membershipName, this)
+        // This will trigger CounterpartyCheckMembershipFlow
+        val untrustworthyData = initiateFlow(otherParty).sendAndReceive<CheckMembershipResult>(membershipName)
+        return untrustworthyData.unwrap { it }
+    }
+}
+
+@InitiatedBy(CheckMembershipFlow::class)
+class CounterpartyCheckMembershipFlow(private val otherPartySession: FlowSession) : FlowLogic<Unit>(), MembershipAware {
+    @Suspendable
+    override fun call() {
+        val membershipName = otherPartySession.receive<CordaX500Name>().unwrap { it }
+        otherPartySession.counterparty.checkMembership(membershipName, this)
+        otherPartySession.send(CheckMembershipResult.PASS)
     }
 }

samples/business-network-demo/src/main/kotlin/net/corda/sample/businessnetwork/membership/MembershipAware.kt

@@ -4,7 +4,6 @@ import net.corda.core.flows.FlowException
 import net.corda.core.flows.FlowLogic
 import net.corda.core.identity.AbstractParty
 import net.corda.core.identity.CordaX500Name
-import net.corda.core.identity.Party
 import net.corda.core.node.ServiceHub
 import net.corda.sample.businessnetwork.membership.internal.MembershipListProvider
 
@@ -22,10 +21,6 @@ interface MembershipAware {
     }
 
     fun getMembershipList(listName: CordaX500Name, serviceHub: ServiceHub): MembershipList = MembershipListProvider.obtainMembershipList(listName, serviceHub.networkMapCache)
-
-    fun <T> Party.checkSharesSameMembershipWithUs(membershipName: CordaX500Name, initiatorFlow: FlowLogic<T>) {
-        initiatorFlow.stateMachine.initiateFlow(this, CheckMembershipFlow(membershipName, initiatorFlow.ourIdentity))
-    }
 }
 
 class MembershipViolationException(msg: String) : FlowException(msg)