Commit bcbde4c0 authored by Julian Anastasov's avatar Julian Anastasov Committed by Simon Horman
Browse files

ipvs: make the service replacement more robust 



commit 578bc3ef ("ipvs: reorganize dest trash") added
IP_VS_DEST_STATE_REMOVING flag and RCU callback named
ip_vs_dest_wait_readers() to keep dests and services after
removal for at least a RCU grace period. But we have the
following corner cases:

- we can not reuse the same dest if its service is removed
while IP_VS_DEST_STATE_REMOVING is still set because another dest
removal in the first grace period can not extend this period.
It can happen when ipvsadm -C && ipvsadm -R is used.

- dest->svc can be replaced but ip_vs_in_stats() and
ip_vs_out_stats() have no explicit read memory barriers
when accessing dest->svc. It can happen that dest->svc
was just freed (replaced) while we use it to update
the stats.

We solve the problems as follows:

- IP_VS_DEST_STATE_REMOVING is removed and we ensure a fixed
idle period for the dest (IP_VS_DEST_TRASH_PERIOD). idle_start
will remember when for first time after deletion we noticed
dest->refcnt=0. Later, the connections can grab a reference
while in RCU grace period but if refcnt becomes 0 we can
safely free the dest and its svc.

- dest->svc becomes RCU pointer. As result, we add explicit
RCU locking in ip_vs_in_stats() and ip_vs_out_stats().

- __ip_vs_unbind_svc is renamed to __ip_vs_svc_put(), it
now can free the service immediately or after a RCU grace
period. dest->svc is not set to NULL anymore.

	As result, unlinked dests and their services are
freed always after IP_VS_DEST_TRASH_PERIOD period, unused
services are freed after a RCU grace period.

Signed-off-by: default avatarJulian Anastasov <ja@ssi.bg>
Signed-off-by: default avatarSimon Horman <horms@verge.net.au>
parent c16526a7

include/net/ip_vs.h

+2 −5
Original line number Diff line number Diff line
@@ -723,8 +723,6 @@ struct ip_vs_dest_dst { 
	struct rcu_head		rcu_head;

};



/* In grace period after removing */

#define IP_VS_DEST_STATE_REMOVING	0x01

/*

 *	The real server destination forwarding entry

 *	with ip address, port number, and so on.
@@ -742,7 +740,7 @@ struct ip_vs_dest { 


	atomic_t		refcnt;		/* reference counter */

	struct ip_vs_stats      stats;          /* statistics */

	unsigned long		state;		/* state flags */

	unsigned long		idle_start;	/* start time, jiffies */



	/* connection counters and thresholds */

	atomic_t		activeconns;	/* active connections */
@@ -756,14 +754,13 @@ struct ip_vs_dest { 
	struct ip_vs_dest_dst __rcu *dest_dst;	/* cached dst info */



	/* for virtual service */

	struct ip_vs_service	*svc;		/* service it belongs to */

	struct ip_vs_service __rcu *svc;	/* service it belongs to */

	__u16			protocol;	/* which protocol (TCP/UDP) */

	__be16			vport;		/* virtual port number */

	union nf_inet_addr	vaddr;		/* virtual IP address */

	__u32			vfwmark;	/* firewall mark of service */



	struct list_head	t_list;		/* in dest_trash */

	struct rcu_head		rcu_head;

	unsigned int		in_rs_table:1;	/* we are in rs_table */

};

net/netfilter/ipvs/ip_vs_core.c

+10 −2
Original line number Diff line number Diff line
@@ -116,6 +116,7 @@ ip_vs_in_stats(struct ip_vs_conn *cp, struct sk_buff *skb) 


	if (dest && (dest->flags & IP_VS_DEST_F_AVAILABLE)) {

		struct ip_vs_cpu_stats *s;

		struct ip_vs_service *svc;



		s = this_cpu_ptr(dest->stats.cpustats);

		s->ustats.inpkts++;
@@ -123,11 +124,14 @@ ip_vs_in_stats(struct ip_vs_conn *cp, struct sk_buff *skb) 
		s->ustats.inbytes += skb->len;

		u64_stats_update_end(&s->syncp);



		s = this_cpu_ptr(dest->svc->stats.cpustats);

		rcu_read_lock();

		svc = rcu_dereference(dest->svc);

		s = this_cpu_ptr(svc->stats.cpustats);

		s->ustats.inpkts++;

		u64_stats_update_begin(&s->syncp);

		s->ustats.inbytes += skb->len;

		u64_stats_update_end(&s->syncp);

		rcu_read_unlock();



		s = this_cpu_ptr(ipvs->tot_stats.cpustats);

		s->ustats.inpkts++;
@@ -146,6 +150,7 @@ ip_vs_out_stats(struct ip_vs_conn *cp, struct sk_buff *skb) 


	if (dest && (dest->flags & IP_VS_DEST_F_AVAILABLE)) {

		struct ip_vs_cpu_stats *s;

		struct ip_vs_service *svc;



		s = this_cpu_ptr(dest->stats.cpustats);

		s->ustats.outpkts++;
@@ -153,11 +158,14 @@ ip_vs_out_stats(struct ip_vs_conn *cp, struct sk_buff *skb) 
		s->ustats.outbytes += skb->len;

		u64_stats_update_end(&s->syncp);



		s = this_cpu_ptr(dest->svc->stats.cpustats);

		rcu_read_lock();

		svc = rcu_dereference(dest->svc);

		s = this_cpu_ptr(svc->stats.cpustats);

		s->ustats.outpkts++;

		u64_stats_update_begin(&s->syncp);

		s->ustats.outbytes += skb->len;

		u64_stats_update_end(&s->syncp);

		rcu_read_unlock();



		s = this_cpu_ptr(ipvs->tot_stats.cpustats);

		s->ustats.outpkts++;

net/netfilter/ipvs/ip_vs_ctl.c

+35 −51
Original line number Diff line number Diff line
@@ -460,7 +460,7 @@ static inline void 
__ip_vs_bind_svc(struct ip_vs_dest *dest, struct ip_vs_service *svc)

{

	atomic_inc(&svc->refcnt);

	dest->svc = svc;

	rcu_assign_pointer(dest->svc, svc);

}



static void ip_vs_service_free(struct ip_vs_service *svc)
@@ -470,17 +470,24 @@ static void ip_vs_service_free(struct ip_vs_service *svc) 
	kfree(svc);

}



static void

__ip_vs_unbind_svc(struct ip_vs_dest *dest)

static void ip_vs_service_rcu_free(struct rcu_head *head)

{

	struct ip_vs_service *svc = dest->svc;

	struct ip_vs_service *svc;



	dest->svc = NULL;

	svc = container_of(head, struct ip_vs_service, rcu_head);

	ip_vs_service_free(svc);

}



static void __ip_vs_svc_put(struct ip_vs_service *svc, bool do_delay)

{

	if (atomic_dec_and_test(&svc->refcnt)) {

		IP_VS_DBG_BUF(3, "Removing service %u/%s:%u\n",

			      svc->fwmark,

			      IP_VS_DBG_ADDR(svc->af, &svc->addr),

			      ntohs(svc->port));

		if (do_delay)

			call_rcu(&svc->rcu_head, ip_vs_service_rcu_free);

		else

			ip_vs_service_free(svc);

	}

}
@@ -667,11 +674,6 @@ ip_vs_trash_get_dest(struct ip_vs_service *svc, const union nf_inet_addr *daddr, 
			      IP_VS_DBG_ADDR(svc->af, &dest->addr),

			      ntohs(dest->port),

			      atomic_read(&dest->refcnt));

		/* We can not reuse dest while in grace period

		 * because conns still can use dest->svc

		 */

		if (test_bit(IP_VS_DEST_STATE_REMOVING, &dest->state))

			continue;

		if (dest->af == svc->af &&

		    ip_vs_addr_equal(svc->af, &dest->addr, daddr) &&

		    dest->port == dport &&
@@ -697,8 +699,10 @@ out: 


static void ip_vs_dest_free(struct ip_vs_dest *dest)

{

	struct ip_vs_service *svc = rcu_dereference_protected(dest->svc, 1);



	__ip_vs_dst_cache_reset(dest);

	__ip_vs_unbind_svc(dest);

	__ip_vs_svc_put(svc, false);

	free_percpu(dest->stats.cpustats);

	kfree(dest);

}
@@ -771,6 +775,7 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest, 
		    struct ip_vs_dest_user_kern *udest, int add)

{

	struct netns_ipvs *ipvs = net_ipvs(svc->net);

	struct ip_vs_service *old_svc;

	struct ip_vs_scheduler *sched;

	int conn_flags;
@@ -792,13 +797,14 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest, 
	atomic_set(&dest->conn_flags, conn_flags);



	/* bind the service */

	if (!dest->svc) {

	old_svc = rcu_dereference_protected(dest->svc, 1);

	if (!old_svc) {

		__ip_vs_bind_svc(dest, svc);

	} else {

		if (dest->svc != svc) {

			__ip_vs_unbind_svc(dest);

		if (old_svc != svc) {

			ip_vs_zero_stats(&dest->stats);

			__ip_vs_bind_svc(dest, svc);

			__ip_vs_svc_put(old_svc, true);

		}

	}
@@ -998,16 +1004,6 @@ ip_vs_edit_dest(struct ip_vs_service *svc, struct ip_vs_dest_user_kern *udest) 
	return 0;

}



static void ip_vs_dest_wait_readers(struct rcu_head *head)

{

	struct ip_vs_dest *dest = container_of(head, struct ip_vs_dest,

					       rcu_head);



	/* End of grace period after unlinking */

	clear_bit(IP_VS_DEST_STATE_REMOVING, &dest->state);

}





/*

 *	Delete a destination (must be already unlinked from the service)

 */
@@ -1023,20 +1019,16 @@ static void __ip_vs_del_dest(struct net *net, struct ip_vs_dest *dest, 
	 */

	ip_vs_rs_unhash(dest);



	if (!cleanup) {

		set_bit(IP_VS_DEST_STATE_REMOVING, &dest->state);

		call_rcu(&dest->rcu_head, ip_vs_dest_wait_readers);

	}



	spin_lock_bh(&ipvs->dest_trash_lock);

	IP_VS_DBG_BUF(3, "Moving dest %s:%u into trash, dest->refcnt=%d\n",

		      IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),

		      atomic_read(&dest->refcnt));

	if (list_empty(&ipvs->dest_trash) && !cleanup)

		mod_timer(&ipvs->dest_trash_timer,

			  jiffies + IP_VS_DEST_TRASH_PERIOD);

			  jiffies + (IP_VS_DEST_TRASH_PERIOD >> 1));

	/* dest lives in trash without reference */

	list_add(&dest->t_list, &ipvs->dest_trash);

	dest->idle_start = 0;

	spin_unlock_bh(&ipvs->dest_trash_lock);

	ip_vs_dest_put(dest);

}
@@ -1108,24 +1100,30 @@ static void ip_vs_dest_trash_expire(unsigned long data) 
	struct net *net = (struct net *) data;

	struct netns_ipvs *ipvs = net_ipvs(net);

	struct ip_vs_dest *dest, *next;

	unsigned long now = jiffies;



	spin_lock(&ipvs->dest_trash_lock);

	list_for_each_entry_safe(dest, next, &ipvs->dest_trash, t_list) {

		/* Skip if dest is in grace period */

		if (test_bit(IP_VS_DEST_STATE_REMOVING, &dest->state))

			continue;

		if (atomic_read(&dest->refcnt) > 0)

			continue;

		if (dest->idle_start) {

			if (time_before(now, dest->idle_start +

					     IP_VS_DEST_TRASH_PERIOD))

				continue;

		} else {

			dest->idle_start = max(1UL, now);

			continue;

		}

		IP_VS_DBG_BUF(3, "Removing destination %u/%s:%u from trash\n",

			      dest->vfwmark,

			      IP_VS_DBG_ADDR(dest->svc->af, &dest->addr),

			      IP_VS_DBG_ADDR(dest->af, &dest->addr),

			      ntohs(dest->port));

		list_del(&dest->t_list);

		ip_vs_dest_free(dest);

	}

	if (!list_empty(&ipvs->dest_trash))

		mod_timer(&ipvs->dest_trash_timer,

			  jiffies + IP_VS_DEST_TRASH_PERIOD);

			  jiffies + (IP_VS_DEST_TRASH_PERIOD >> 1));

	spin_unlock(&ipvs->dest_trash_lock);

}
@@ -1320,14 +1318,6 @@ out: 
	return ret;

}



static void ip_vs_service_rcu_free(struct rcu_head *head)

{

	struct ip_vs_service *svc;



	svc = container_of(head, struct ip_vs_service, rcu_head);

	ip_vs_service_free(svc);

}



/*

 *	Delete a service from the service list

 *	- The service must be unlinked, unlocked and not referenced!
@@ -1376,13 +1366,7 @@ static void __ip_vs_del_service(struct ip_vs_service *svc, bool cleanup) 
	/*

	 *    Free the service if nobody refers to it

	 */

	if (atomic_dec_and_test(&svc->refcnt)) {

		IP_VS_DBG_BUF(3, "Removing service %u/%s:%u\n",

			      svc->fwmark,

			      IP_VS_DBG_ADDR(svc->af, &svc->addr),

			      ntohs(svc->port));

		call_rcu(&svc->rcu_head, ip_vs_service_rcu_free);

	}

	__ip_vs_svc_put(svc, true);



	/* decrease the module use count */

	ip_vs_use_count_dec();

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