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[PATCH] netfilter/ipvs: queue delayed work to expire no destination conn

To: unlisted-recipients:; (no To-header on input)
Subject: [PATCH] netfilter/ipvs: queue delayed work to expire no destination connections if expire_nodest_conn=1
Cc: Julian Anastasov <ja@xxxxxx>, Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx, Andrew Sy Kim <kim.andrewsy@xxxxxxxxx>
From: Andrew Sy Kim <kim.andrewsy@xxxxxxxxx>
Date: Mon, 8 Jun 2020 16:20:24 -0400
When expire_nodest_conn=1 and a destination is deleted, IPVS does not
expire the existing connections until the next matching incoming packet.
If there are many connection entries from a single client to a single
destination, many packets may get dropped before all the connections are
expired (more likely with lots of UDP traffic). An optimization can be
made where upon deletion of a destination, IPVS queues up delayed work
to immediately expire any connections with a deleted destination. This
ensures any reused source ports from a client (within the IPVS timeouts)
are scheduled to new real servers instead of silently dropped.

Signed-off-by: Andrew Sy Kim <kim.andrewsy@xxxxxxxxx>
---
 include/net/ip_vs.h             | 29 +++++++++++++++++++++
 net/netfilter/ipvs/ip_vs_conn.c | 43 +++++++++++++++++++++++++++++++
 net/netfilter/ipvs/ip_vs_core.c | 45 +++++++++++++--------------------
 net/netfilter/ipvs/ip_vs_ctl.c  | 22 ++++++++++++++++
 4 files changed, 112 insertions(+), 27 deletions(-)

diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 83be2d93b407..49ca61765298 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -14,6 +14,7 @@
 #include <linux/spinlock.h>             /* for struct rwlock_t */
 #include <linux/atomic.h>               /* for struct atomic_t */
 #include <linux/refcount.h>             /* for struct refcount_t */
+#include <linux/workqueue.h>
 
 #include <linux/compiler.h>
 #include <linux/timer.h>
@@ -885,6 +886,8 @@ struct netns_ipvs {
        atomic_t                conn_out_counter;
 
 #ifdef CONFIG_SYSCTL
+       /* delayed work for expiring no dest connections */
+       struct delayed_work     expire_nodest_conn_work;
        /* 1/rate drop and drop-entry variables */
        struct delayed_work     defense_work;   /* Work handler */
        int                     drop_rate;
@@ -1049,6 +1052,11 @@ static inline int sysctl_conn_reuse_mode(struct 
netns_ipvs *ipvs)
        return ipvs->sysctl_conn_reuse_mode;
 }
 
+static inline int sysctl_expire_nodest_conn(struct netns_ipvs *ipvs)
+{
+       return ipvs->sysctl_expire_nodest_conn;
+}
+
 static inline int sysctl_schedule_icmp(struct netns_ipvs *ipvs)
 {
        return ipvs->sysctl_schedule_icmp;
@@ -1136,6 +1144,11 @@ static inline int sysctl_conn_reuse_mode(struct 
netns_ipvs *ipvs)
        return 1;
 }
 
+static inline int sysctl_expire_nodest_conn(struct netns_ipvs *ipvs)
+{
+       return 0;
+}
+
 static inline int sysctl_schedule_icmp(struct netns_ipvs *ipvs)
 {
        return 0;
@@ -1505,6 +1518,22 @@ static inline int ip_vs_todrop(struct netns_ipvs *ipvs)
 static inline int ip_vs_todrop(struct netns_ipvs *ipvs) { return 0; }
 #endif
 
+#ifdef CONFIG_SYSCTL
+/* Enqueue delayed work for expiring no dest connections
+ * Only run when sysctl_expire_nodest=1
+ */
+static inline void ip_vs_enqueue_expire_nodest_conns(struct netns_ipvs *ipvs)
+{
+       if (sysctl_expire_nodest_conn(ipvs))
+               queue_delayed_work(system_long_wq,
+                                  &ipvs->expire_nodest_conn_work, 1);
+}
+
+void ip_vs_expire_nodest_conn_flush(struct netns_ipvs *ipvs);
+#else
+static inline void ip_vs_enqueue_expire_nodest_conns(struct netns_ipvs) {}
+#endif
+
 #define IP_VS_DFWD_METHOD(dest) (atomic_read(&(dest)->conn_flags) & \
                                 IP_VS_CONN_F_FWD_MASK)
 
diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index 02f2f636798d..f0d744e8c716 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -1366,6 +1366,49 @@ static void ip_vs_conn_flush(struct netns_ipvs *ipvs)
                goto flush_again;
        }
 }
+
+#ifdef CONFIG_SYSCTL
+void ip_vs_expire_nodest_conn_flush(struct netns_ipvs *ipvs)
+{
+       int idx;
+       struct ip_vs_conn *cp, *cp_c;
+       struct ip_vs_dest *dest;
+
+       rcu_read_lock();
+       for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
+               hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
+                       if (cp->ipvs != ipvs)
+                               continue;
+
+                       dest = cp->dest;
+                       if (!dest || (dest->flags & IP_VS_DEST_F_AVAILABLE))
+                               continue;
+
+                       /* As timers are expired in LIFO order, restart
+                        * the timer of controlling connection first, so
+                        * that it is expired after us.
+                        */
+                       cp_c = cp->control;
+                       /* cp->control is valid only with reference to cp */
+                       if (cp_c && __ip_vs_conn_get(cp)) {
+                               IP_VS_DBG(4, "del controlling connection\n");
+                               ip_vs_conn_expire_now(cp_c);
+                               __ip_vs_conn_put(cp);
+                       }
+
+                       IP_VS_DBG(4, "del connection\n");
+                       ip_vs_conn_expire_now(cp);
+               }
+               cond_resched_rcu();
+
+               /* netns clean up started, abort delayed work */
+               if (!ipvs->enable)
+                       return;
+       }
+       rcu_read_unlock();
+}
+#endif
+
 /*
  * per netns init and exit
  */
diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index aa6a603a2425..2508a9caeae8 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -694,16 +694,10 @@ static int sysctl_nat_icmp_send(struct netns_ipvs *ipvs)
        return ipvs->sysctl_nat_icmp_send;
 }
 
-static int sysctl_expire_nodest_conn(struct netns_ipvs *ipvs)
-{
-       return ipvs->sysctl_expire_nodest_conn;
-}
-
 #else
 
 static int sysctl_snat_reroute(struct netns_ipvs *ipvs) { return 0; }
 static int sysctl_nat_icmp_send(struct netns_ipvs *ipvs) { return 0; }
-static int sysctl_expire_nodest_conn(struct netns_ipvs *ipvs) { return 0; }
 
 #endif
 
@@ -2095,36 +2089,33 @@ ip_vs_in(struct netns_ipvs *ipvs, unsigned int hooknum, 
struct sk_buff *skb, int
                }
        }
 
-       if (unlikely(!cp)) {
-               int v;
-
-               if (!ip_vs_try_to_schedule(ipvs, af, skb, pd, &v, &cp, &iph))
-                       return v;
-       }
-
-       IP_VS_DBG_PKT(11, af, pp, skb, iph.off, "Incoming packet");
-
        /* Check the server status */
-       if (cp->dest && !(cp->dest->flags & IP_VS_DEST_F_AVAILABLE)) {
+       if (cp && cp->dest && !(cp->dest->flags & IP_VS_DEST_F_AVAILABLE)) {
                /* the destination server is not available */
 
-               __u32 flags = cp->flags;
-
-               /* when timer already started, silently drop the packet.*/
-               if (timer_pending(&cp->timer))
-                       __ip_vs_conn_put(cp);
-               else
-                       ip_vs_conn_put(cp);
+               if (sysctl_expire_nodest_conn(ipvs)) {
+                       bool uses_ct = ip_vs_conn_uses_conntrack(cp, skb);
 
-               if (sysctl_expire_nodest_conn(ipvs) &&
-                   !(flags & IP_VS_CONN_F_ONE_PACKET)) {
-                       /* try to expire the connection immediately */
                        ip_vs_conn_expire_now(cp);
+                       __ip_vs_conn_put(cp);
+                       if (uses_ct)
+                               return NF_DROP;
+                       cp = NULL;
+               } else {
+                       __ip_vs_conn_put(cp);
+                       return NF_DROP;
                }
+       }
 
-               return NF_DROP;
+       if (unlikely(!cp)) {
+               int v;
+
+               if (!ip_vs_try_to_schedule(ipvs, af, skb, pd, &v, &cp, &iph))
+                       return v;
        }
 
+       IP_VS_DBG_PKT(11, af, pp, skb, iph.off, "Incoming packet");
+
        ip_vs_in_stats(cp, skb);
        ip_vs_set_state(cp, IP_VS_DIR_INPUT, skb, pd);
        if (cp->packet_xmit)
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 8d14a1acbc37..9e53f517f138 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -210,6 +210,17 @@ static void update_defense_level(struct netns_ipvs *ipvs)
        local_bh_enable();
 }
 
+/* Handler for delayed work for expiring no
+ * destination connections
+ */
+static void expire_nodest_conn_handler(struct work_struct *work)
+{
+       struct netns_ipvs *ipvs;
+
+       ipvs = container_of(work, struct netns_ipvs,
+                           expire_nodest_conn_work.work);
+       ip_vs_expire_nodest_conn_flush(ipvs);
+}
 
 /*
  *     Timer for checking the defense
@@ -1163,6 +1174,12 @@ static void __ip_vs_del_dest(struct netns_ipvs *ipvs, 
struct ip_vs_dest *dest,
        list_add(&dest->t_list, &ipvs->dest_trash);
        dest->idle_start = 0;
        spin_unlock_bh(&ipvs->dest_trash_lock);
+
+       /* Queue up delayed work to expire all no estination connections.
+        * No-op when CONFIG_SYSCTL is disabled.
+        */
+       if (!cleanup)
+               ip_vs_enqueue_expire_nodest_conns(ipvs);
 }
 
 
@@ -4065,6 +4082,10 @@ static int __net_init 
ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
        INIT_DELAYED_WORK(&ipvs->defense_work, defense_work_handler);
        schedule_delayed_work(&ipvs->defense_work, DEFENSE_TIMER_PERIOD);
 
+       /* Init delayed work for expiring no dest conn */
+       INIT_DELAYED_WORK(&ipvs->expire_nodest_conn_work,
+                         expire_nodest_conn_handler);
+
        return 0;
 }
 
@@ -4072,6 +4093,7 @@ static void __net_exit 
ip_vs_control_net_cleanup_sysctl(struct netns_ipvs *ipvs)
 {
        struct net *net = ipvs->net;
 
+       cancel_delayed_work_sync(&ipvs->expire_nodest_conn_work);
        cancel_delayed_work_sync(&ipvs->defense_work);
        cancel_work_sync(&ipvs->defense_work.work);
        unregister_net_sysctl_table(ipvs->sysctl_hdr);
-- 
2.20.1


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