FAB-1018 Gossip multi-channel support API design

https://jira.hyperledger.org/browse/FAB-1018

This commit contains code that should be implemented
by layers that use the gossip component.
This code enables the gossip component to determine to which peers
it may forward a certain block according to the channel

Change-Id: I01d274ef91837b5d5b4e8bc0d78a49df90957185
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>

gossip/api/api.go

@@ -16,18 +16,12 @@ limitations under the License.
 
 package api
 
-
 // GossipService is used to publish new blocks to the gossip network
 type GossipService interface {
 	// payload: Holds the block's content, hash and seqNum
 	Publish(payload Payload) error
 }
 
-type BindAddress struct {
-	Host string
-	Port int16
-}
-
 // Payload defines an object that contains a ledger block
 type Payload struct {
 	Data   []byte // The content of the message, possibly encrypted or signed
@@ -54,12 +48,12 @@ type ReplicationProvider interface {
 	LastBlockSeq() uint64
 }
 
-// MessageCryptoVerifier verifies the message's authenticity,
+// MessageCryptoService verifies the message's authenticity,
 // if messages are cryptographically signed
 type MessageCryptoService interface {
 	// Verify returns nil whether the message and its identifier are authentic,
 	// otherwise returns an error
-	VerifyBlock(seqNum uint64, pkiId []byte, payload Payload) error
+	VerifyBlock(seqNum uint64, pkiID []byte, payload Payload) error
 
 	// Sign signs msg with this peer's signing key and outputs
 	// the signature if no error occurred.

gossip/api/channel.go

@@ -0,0 +1,62 @@
+/*
+Copyright IBM Corp. 2016 All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+		 http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package api
+
+import "time"
+
+// SecurityAdvisor defines an external auxiliary object
+// that provides security and identity related capabilities
+type SecurityAdvisor interface {
+	// IsInMyOrg returns whether the given peer's certificate represents
+	// a peer in the invoker's organization
+	IsInMyOrg(PeerCert) bool
+
+	// Verify verifies a JoinChannelMessage, returns nil on success,
+	// and an error on failure
+	Verify(JoinChannelMessage) error
+}
+
+// ChannelNotifier is implemented by the gossip component and is used for the peer
+// layer to notify the gossip component of a JoinChannel event
+type ChannelNotifier interface {
+	JoinChannel(joinMsg JoinChannelMessage, chainID ChainID)
+}
+
+// JoinChannelMessage is the message that asserts a creation or mutation
+// of a channel's membership list, and is the message that is gossipped
+// among the peers
+type JoinChannelMessage interface {
+
+	// GetTimestamp returns the timestamp of the message's creation
+	GetTimestamp() time.Time
+
+	// PeerList returns all the peers that are in the channel
+	PeerList() []RemotePeer
+}
+
+// ChainID defines the identity representation of a chain
+type ChainID []byte
+
+// RemotePeer is a peer's certificate and endpoint (host:port)
+type RemotePeer struct {
+	cert PeerCert
+	host string
+	port int
+}
+
+// PeerCert defines the cryptographic identity of a peer
+type PeerCert []byte