tipc: add second source address to recvmsg()/recvfrom()

With group communication, it becomes important for a message receiver to
identify not only from which socket (identfied by a node:port tuple) the
message was sent, but also the logical identity (type:instance) of the
sending member.

We fix this by adding a second instance of struct sockaddr_tipc to the
source address area when a message is read. The extra address struct
is filled in with data found in the received message header (type,) and
in the local member representation struct (instance.)

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/msg.h

@@ -100,6 +100,7 @@ struct plist;
 
 struct tipc_skb_cb {
 	u32 bytes_read;
+	u32 orig_member;
 	struct sk_buff *tail;
 	bool validated;
 	u16 chain_imp;