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Date: Tue, 1 Sep 2009 11:59:12 +1000
From: Simon Horman <horms@...ge.net.au>
To: Patrick McHardy <kaber@...sh.net>
Cc: lvs-devel@...r.kernel.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org,
홍신 shin hong <hongshin@...il.com>,
David Miller <davem@...emloft.net>
Subject: Re: [patch] ipvs: Use atomic operations atomicly
On Mon, Aug 31, 2009 at 02:22:26PM +0200, Patrick McHardy wrote:
> Simon Horman wrote:
> > A pointed out by Shin Hong, IPVS doesn't always use atomic operations
> > in an atomic manner. While this seems unlikely to be manifest in
> > strange behaviour, it seems appropriate to clean this up.
> >
> > Cc: 홍신 shin hong <hongshin@...il.com>
> > Signed-off-by: Simon Horman <horms@...ge.net.au>
>
> Applied, thanks.
>
> > if (af == AF_INET &&
> > (ip_vs_sync_state & IP_VS_STATE_MASTER) &&
> > (((cp->protocol != IPPROTO_TCP ||
> > cp->state == IP_VS_TCP_S_ESTABLISHED) &&
> > - (atomic_read(&cp->in_pkts) % sysctl_ip_vs_sync_threshold[1]
> > + (pkts % sysctl_ip_vs_sync_threshold[1]
>
> It seems that proc_do_sync_threshold() should check whether this value
> is zero. The current checks also look racy since incorrect values are
> first updated, then overwritten again.
Hi,
I'm wondering if an approach along the lines of the following is valid.
The idea is that the value in the ctl_table is essentially a scratch
value that is used by the parser and then copied into ip_vs_sync_threshold
if it is valid. I'm concerned that there are atomicity issues
surrounding writing ip_vs_sync_threshold while there might be readers.
diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 98978e7..28d0c4f 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -774,8 +774,8 @@ extern int ip_vs_leave(struct ip_vs_service *svc, struct sk_buff *skb,
extern int sysctl_ip_vs_cache_bypass;
extern int sysctl_ip_vs_expire_nodest_conn;
extern int sysctl_ip_vs_expire_quiescent_template;
-extern int sysctl_ip_vs_sync_threshold[2];
extern int sysctl_ip_vs_nat_icmp_send;
+extern int ip_vs_sync_threshold[2];
extern struct ip_vs_stats ip_vs_stats;
extern const struct ctl_path net_vs_ctl_path[];
diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index b95699f..f3572b6 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -1362,8 +1362,7 @@ ip_vs_in(unsigned int hooknum, struct sk_buff *skb,
(ip_vs_sync_state & IP_VS_STATE_MASTER) &&
(((cp->protocol != IPPROTO_TCP ||
cp->state == IP_VS_TCP_S_ESTABLISHED) &&
- (pkts % sysctl_ip_vs_sync_threshold[1]
- == sysctl_ip_vs_sync_threshold[0])) ||
+ (pkts % ip_vs_sync_threshold[1] == ip_vs_sync_threshold[0])) ||
((cp->protocol == IPPROTO_TCP) && (cp->old_state != cp->state) &&
((cp->state == IP_VS_TCP_S_FIN_WAIT) ||
(cp->state == IP_VS_TCP_S_CLOSE_WAIT) ||
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index fba2892..8a9ff21 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -76,6 +76,11 @@ static atomic_t ip_vs_dropentry = ATOMIC_INIT(0);
/* number of virtual services */
static int ip_vs_num_services = 0;
+/* threshold handling */
+static int ip_vs_sync_threshold_min = 0;
+static int ip_vs_sync_threshold_max = INT_MAX;
+int ip_vs_sync_threshold[2] = { 3, 50 };
+
/* sysctl variables */
static int sysctl_ip_vs_drop_entry = 0;
static int sysctl_ip_vs_drop_packet = 0;
@@ -85,7 +90,7 @@ static int sysctl_ip_vs_am_droprate = 10;
int sysctl_ip_vs_cache_bypass = 0;
int sysctl_ip_vs_expire_nodest_conn = 0;
int sysctl_ip_vs_expire_quiescent_template = 0;
-int sysctl_ip_vs_sync_threshold[2] = { 3, 50 };
+static int sysctl_ip_vs_sync_threshold[2];
int sysctl_ip_vs_nat_icmp_send = 0;
@@ -1521,17 +1526,12 @@ proc_do_sync_threshold(ctl_table *table, int write, struct file *filp,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int *valp = table->data;
- int val[2];
int rc;
- /* backup the value first */
- memcpy(val, valp, sizeof(val));
-
- rc = proc_dointvec(table, write, filp, buffer, lenp, ppos);
- if (write && (valp[0] < 0 || valp[1] < 0 || valp[0] >= valp[1])) {
- /* Restore the correct value */
- memcpy(valp, val, sizeof(val));
- }
+ rc = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+ if (write && (valp[0] < valp[1]))
+ memcpy(ip_vs_sync_threshold, valp,
+ sizeof(ip_vs_sync_threshold));
return rc;
}
@@ -1698,6 +1698,8 @@ static struct ctl_table vs_vars[] = {
.maxlen = sizeof(sysctl_ip_vs_sync_threshold),
.mode = 0644,
.proc_handler = proc_do_sync_threshold,
+ .extra1 = &ip_vs_sync_threshold_min,
+ .extra2 = &ip_vs_sync_threshold_max,
},
{
.procname = "nat_icmp_send",
diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
index e177f0d..d3322fb 100644
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -438,7 +438,7 @@ static void ip_vs_process_message(const char *buffer, const size_t buflen)
if (opt)
memcpy(&cp->in_seq, opt, sizeof(*opt));
- atomic_set(&cp->in_pkts, sysctl_ip_vs_sync_threshold[0]);
+ atomic_set(&cp->in_pkts, ip_vs_sync_threshold[0]);
cp->state = state;
cp->old_state = cp->state;
/*
--
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