ipvs: add sync_persist_mode flag

Add sync_persist_mode flag to reduce sync traffic
by syncing only persistent templates.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Tested-by: Aleksey Chudov <aleksey.chudov@gmail.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

Documentation/networking/ipvs-sysctl.txt

@@ -181,6 +181,19 @@ snat_reroute - BOOLEAN
 	always be the same as the original route so it is an optimisation
 	to disable snat_reroute and avoid the recalculation.
 
+sync_persist_mode - INTEGER
+	default 0
+
+	Controls the synchronisation of connections when using persistence
+
+	0: All types of connections are synchronised
+	1: Attempt to reduce the synchronisation traffic depending on
+	the connection type. For persistent services avoid synchronisation
+	for normal connections, do it only for persistence templates.
+	In such case, for TCP and SCTP it may need enabling sloppy_tcp and
+	sloppy_sctp flags on backup servers. For non-persistent services
+	such optimization is not applied, mode 0 is assumed.
+
 sync_version - INTEGER
 	default 1
 

include/net/ip_vs.h

@@ -975,6 +975,7 @@ struct netns_ipvs {
 	int			sysctl_snat_reroute;
 	int			sysctl_sync_ver;
 	int			sysctl_sync_ports;
+	int			sysctl_sync_persist_mode;
 	unsigned long		sysctl_sync_qlen_max;
 	int			sysctl_sync_sock_size;
 	int			sysctl_cache_bypass;
@@ -1076,6 +1077,11 @@ static inline int sysctl_sync_ports(struct netns_ipvs *ipvs)
 	return ACCESS_ONCE(ipvs->sysctl_sync_ports);
 }
 
+static inline int sysctl_sync_persist_mode(struct netns_ipvs *ipvs)
+{
+	return ipvs->sysctl_sync_persist_mode;
+}
+
 static inline unsigned long sysctl_sync_qlen_max(struct netns_ipvs *ipvs)
 {
 	return ipvs->sysctl_sync_qlen_max;
@@ -1139,6 +1145,11 @@ static inline int sysctl_sync_ports(struct netns_ipvs *ipvs)
 	return 1;
 }
 
+static inline int sysctl_sync_persist_mode(struct netns_ipvs *ipvs)
+{
+	return 0;
+}
+
 static inline unsigned long sysctl_sync_qlen_max(struct netns_ipvs *ipvs)
 {
 	return IPVS_SYNC_QLEN_MAX;

net/netfilter/ipvs/ip_vs_ctl.c

@@ -1714,6 +1714,12 @@ static struct ctl_table vs_vars[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_do_sync_ports,
 	},
+	{
+		.procname	= "sync_persist_mode",
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
 	{
 		.procname	= "sync_qlen_max",
 		.maxlen		= sizeof(unsigned long),
@@ -3729,6 +3735,7 @@ static int __net_init ip_vs_control_net_init_sysctl(struct net *net)
 	tbl[idx++].data = &ipvs->sysctl_sync_ver;
 	ipvs->sysctl_sync_ports = 1;
 	tbl[idx++].data = &ipvs->sysctl_sync_ports;
+	tbl[idx++].data = &ipvs->sysctl_sync_persist_mode;
 	ipvs->sysctl_sync_qlen_max = nr_free_buffer_pages() / 32;
 	tbl[idx++].data = &ipvs->sysctl_sync_qlen_max;
 	ipvs->sysctl_sync_sock_size = 0;

net/netfilter/ipvs/ip_vs_sync.c

@@ -425,6 +425,16 @@ ip_vs_sync_buff_create_v0(struct netns_ipvs *ipvs)
 	return sb;
 }
 
+/* Check if connection is controlled by persistence */
+static inline bool in_persistence(struct ip_vs_conn *cp)
+{
+	for (cp = cp->control; cp; cp = cp->control) {
+		if (cp->flags & IP_VS_CONN_F_TEMPLATE)
+			return true;
+	}
+	return false;
+}
+
 /* Check if conn should be synced.
  * pkts: conn packets, use sysctl_sync_threshold to avoid packet check
  * - (1) sync_refresh_period: reduce sync rate. Additionally, retry
@@ -447,6 +457,8 @@ static int ip_vs_sync_conn_needed(struct netns_ipvs *ipvs,
 	/* Check if we sync in current state */
 	if (unlikely(cp->flags & IP_VS_CONN_F_TEMPLATE))
 		force = 0;
+	else if (unlikely(sysctl_sync_persist_mode(ipvs) && in_persistence(cp)))
+		return 0;
 	else if (likely(cp->protocol == IPPROTO_TCP)) {
 		if (!((1 << cp->state) &
 		      ((1 << IP_VS_TCP_S_ESTABLISHED) |