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Dmitry Akindinov is reporting for a problem where
SYNs are looping between the master and backup server
when the backup server is used as real server in DR mode
and has IPVS rules to function as director.
Even when the backup function is enabled we
continue to forward traffic and schedule new connections
when the current master is using the backup server as
real server. While this is not a problem for NAT, for
DR and TUN method the backup server can not determine
if a request comes from client or from director.
To avoid such loops add new sysctl flag
backup_only. It can be needed for DR/TUN setups that
do not need backup and director function at the
same time. When the backup function is enabled we
stop any forwarding and pass the traffic to the local
stack (real server mode). The flag disables the
director function when the backup function is enabled.
For setups that enable backup function for
some virtual services and director function for
other virtual services there should be another more
complex solution to support DR/TUN mode, may be to
assign per-virtual service syncid value, so that
we can differentiate the requests.
Reported-by: Dmitry Akindinov <dimak@xxxxxxxxxxx>
Tested-by: German Myzovsky <lawyer@xxxxxxxxx>
Signed-off-by: Julian Anastasov <ja@xxxxxx>
---
Documentation/networking/ipvs-sysctl.txt | 7 +++++++
include/net/ip_vs.h | 12 ++++++++++++
net/netfilter/ipvs/ip_vs_core.c | 12 ++++++++----
net/netfilter/ipvs/ip_vs_ctl.c | 7 +++++++
4 files changed, 34 insertions(+), 4 deletions(-)
diff --git a/Documentation/networking/ipvs-sysctl.txt
b/Documentation/networking/ipvs-sysctl.txt
index f2a2488..9573d0c 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 d1fb021..5ed8939 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -997,6 +997,7 @@ 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;
@@ -1088,6 +1089,12 @@ 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)
@@ -1135,6 +1142,11 @@ 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 2ea2862..15a051c 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -1579,7 +1579,8 @@ 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);
@@ -1656,7 +1657,6 @@ 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 */
@@ -1817,13 +1817,15 @@ 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);
@@ -1837,6 +1839,7 @@ 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);
@@ -1845,7 +1848,8 @@ 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 f4b53c4..11326db 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1806,6 +1806,12 @@ 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",
@@ -3739,6 +3745,7 @@ 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);
--
1.7.3.4
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