ipvs: prevent mixing heterogeneous pools and synchronization

The synchronization protocol is not compatible with heterogeneous pools, so
we need to verify that we're not turning both on at the same time.
Signed-off-by: Alex Gartrell <agartrell@fb.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

include/net/ip_vs.h

@@ -990,6 +990,10 @@ struct netns_ipvs {
 	char			backup_mcast_ifn[IP_VS_IFNAME_MAXLEN];
 	/* net name space ptr */
 	struct net		*net;            /* Needed by timer routines */
+	/* Number of heterogeneous destinations, needed because
+	 * heterogeneous are not supported when synchronization is
+	 * enabled */
+	unsigned int		mixed_address_family_dests;
 };
 
 #define DEFAULT_SYNC_THRESHOLD	3

net/netfilter/ipvs/ip_vs_ctl.c

@@ -779,6 +779,12 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest,
 	struct ip_vs_scheduler *sched;
 	int conn_flags;
 
+	/* We cannot modify an address and change the address family */
+	BUG_ON(!add && udest->af != dest->af);
+
+	if (add && udest->af != svc->af)
+		ipvs->mixed_address_family_dests++;
+
 	/* set the weight and the flags */
 	atomic_set(&dest->weight, udest->weight);
 	conn_flags = udest->conn_flags & IP_VS_CONN_F_DEST_MASK;
@@ -1061,6 +1067,9 @@ static void __ip_vs_unlink_dest(struct ip_vs_service *svc,
 	list_del_rcu(&dest->n_list);
 	svc->num_dests--;
 
+	if (dest->af != svc->af)
+		net_ipvs(svc->net)->mixed_address_family_dests--;
+
 	if (svcupd) {
 		struct ip_vs_scheduler *sched;
 
@@ -3256,6 +3265,12 @@ static int ip_vs_genl_new_daemon(struct net *net, struct nlattr **attrs)
 	      attrs[IPVS_DAEMON_ATTR_SYNC_ID]))
 		return -EINVAL;
 
+	/* The synchronization protocol is incompatible with mixed family
+	 * services
+	 */
+	if (net_ipvs(net)->mixed_address_family_dests > 0)
+		return -EINVAL;
+
 	return start_sync_thread(net,
 				 nla_get_u32(attrs[IPVS_DAEMON_ATTR_STATE]),
 				 nla_data(attrs[IPVS_DAEMON_ATTR_MCAST_IFN]),