4 files changed, 34 insertions, 4 deletions

diff --git a/Documentation/networking/ipvs-sysctl.txt b/Documentation/networking/ipvs-sysctl.txt
index f2a2488f1bf3..9573d0c48c6e 100644
--- a/Documentation/networking/ipvs-sysctl.txt
+++ b/Documentation/networking/ipvs-sysctl.txt
@@ -15,6 +15,13 @@ amemthresh - INTEGER
         enabled and the variable is automatically set to 2, otherwise
         the strategy is disabled and the variable is  set  to 1.
 
+backup_only - BOOLEAN
+        0 - disabled (default)
+        not 0 - enabled
+
+        If set, disable the director function while the server is
+        in backup mode to avoid packet loops for DR/TUN methods.
+
 conntrack - BOOLEAN
         0 - disabled (default)
         not 0 - enabled
diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 68c69d54d392..fce8e6b66d55 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -976,6 +976,7 @@ struct netns_ipvs {
         int                     sysctl_sync_retries;
         int                     sysctl_nat_icmp_send;
         int                     sysctl_pmtu_disc;
+        int                     sysctl_backup_only;
 
         /* ip_vs_lblc */
         int                     sysctl_lblc_expiration;
@@ -1067,6 +1068,12 @@ static inline int sysctl_pmtu_disc(struct netns_ipvs *ipvs)
         return ipvs->sysctl_pmtu_disc;
 }
 
+static inline int sysctl_backup_only(struct netns_ipvs *ipvs)
+{
+        return ipvs->sync_state & IP_VS_STATE_BACKUP &&
+               ipvs->sysctl_backup_only;
+}
+
 #else
 
 static inline int sysctl_sync_threshold(struct netns_ipvs *ipvs)
@@ -1114,6 +1121,11 @@ static inline int sysctl_pmtu_disc(struct netns_ipvs *ipvs)
         return 1;
 }
 
+static inline int sysctl_backup_only(struct netns_ipvs *ipvs)
+{
+        return 0;
+}
+
 #endif
 
 /*
diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index 47edf5a40a59..18b4bc55fa3d 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -1577,7 +1577,8 @@ ip_vs_in(unsigned int hooknum, struct sk_buff *skb, int af)
         }
         /* ipvs enabled in this netns ? */
         net = skb_net(skb);
-        if (!net_ipvs(net)->enable)
+        ipvs = net_ipvs(net);
+        if (unlikely(sysctl_backup_only(ipvs) || !ipvs->enable))
                 return NF_ACCEPT;
 
         ip_vs_fill_iph_skb(af, skb, &iph);
@@ -1654,7 +1655,6 @@ ip_vs_in(unsigned int hooknum, struct sk_buff *skb, int af)
         }
 
         IP_VS_DBG_PKT(11, af, pp, skb, 0, "Incoming packet");
-        ipvs = net_ipvs(net);
         /* Check the server status */
         if (cp->dest && !(cp->dest->flags & IP_VS_DEST_F_AVAILABLE)) {
                 /* the destination server is not available */
@@ -1815,13 +1815,15 @@ ip_vs_forward_icmp(unsigned int hooknum, struct sk_buff *skb,
 {
         int r;
         struct net *net;
+        struct netns_ipvs *ipvs;
 
         if (ip_hdr(skb)->protocol != IPPROTO_ICMP)
                 return NF_ACCEPT;
 
         /* ipvs enabled in this netns ? */
         net = skb_net(skb);
-        if (!net_ipvs(net)->enable)
+        ipvs = net_ipvs(net);
+        if (unlikely(sysctl_backup_only(ipvs) || !ipvs->enable))
                 return NF_ACCEPT;
 
         return ip_vs_in_icmp(skb, &r, hooknum);
@@ -1835,6 +1837,7 @@ ip_vs_forward_icmp_v6(unsigned int hooknum, struct sk_buff *skb,
 {
         int r;
         struct net *net;
+        struct netns_ipvs *ipvs;
         struct ip_vs_iphdr iphdr;
 
         ip_vs_fill_iph_skb(AF_INET6, skb, &iphdr);
@@ -1843,7 +1846,8 @@ ip_vs_forward_icmp_v6(unsigned int hooknum, struct sk_buff *skb,
 
         /* ipvs enabled in this netns ? */
         net = skb_net(skb);
-        if (!net_ipvs(net)->enable)
+        ipvs = net_ipvs(net);
+        if (unlikely(sysctl_backup_only(ipvs) || !ipvs->enable))
                 return NF_ACCEPT;
 
         return ip_vs_in_icmp_v6(skb, &r, hooknum, &iphdr);
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index c68198bf9128..9e2d1cccd1eb 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1808,6 +1808,12 @@ static struct ctl_table vs_vars[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
         },
+        {
+                .procname       = "backup_only",
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec,
+        },
 #ifdef CONFIG_IP_VS_DEBUG
         {
                 .procname       = "debug_level",
@@ -3741,6 +3747,7 @@ static int __net_init ip_vs_control_net_init_sysctl(struct net *net)
         tbl[idx++].data = &ipvs->sysctl_nat_icmp_send;
         ipvs->sysctl_pmtu_disc = 1;
         tbl[idx++].data = &ipvs->sysctl_pmtu_disc;
+        tbl[idx++].data = &ipvs->sysctl_backup_only;
 
 
         ipvs->sysctl_hdr = register_net_sysctl(net, "net/ipv4/vs", tbl);