rxrpc: Clients must accept conn from any address

The find connection logic of Transarc's Rx was modified in the mid-1990s
to support multi-homed servers which might send a response packet from
an address other than the destination address in the received packet.
The rules for accepting a packet by an Rx initiator (RX_CLIENT_CONNECTION)
were altered to permit acceptance of a packet from any address provided
that the port number was unchanged and all of the connection identifiers
matched (Epoch, CID, SecurityClass, ...).

This change applies the same rules to the Linux implementation which makes
it consistent with IBM AFS 3.6, Arla, OpenAFS and AuriStorFS.

Fixes: 17926a7932 ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both")
Signed-off-by: Jeffrey Altman <jaltman@auristor.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Link: https://lore.kernel.org/r/20240419163057.4141728-1-marc.dionne@auristor.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/rxrpc/conn_object.c

@@ -119,18 +119,13 @@ struct rxrpc_connection *rxrpc_find_client_connection_rcu(struct rxrpc_local *lo
 	switch (srx->transport.family) {
 	case AF_INET:
 		if (peer->srx.transport.sin.sin_port !=
-		    srx->transport.sin.sin_port ||
-		    peer->srx.transport.sin.sin_addr.s_addr !=
-		    srx->transport.sin.sin_addr.s_addr)
+		    srx->transport.sin.sin_port)
 			goto not_found;
 		break;
 #ifdef CONFIG_AF_RXRPC_IPV6
 	case AF_INET6:
 		if (peer->srx.transport.sin6.sin6_port !=
-		    srx->transport.sin6.sin6_port ||
-		    memcmp(&peer->srx.transport.sin6.sin6_addr,
-			   &srx->transport.sin6.sin6_addr,
-			   sizeof(struct in6_addr)) != 0)
+		    srx->transport.sin6.sin6_port)
 			goto not_found;
 		break;
 #endif