[PATCH net-next] netfilter: x_table: speedup compat operations

Eric Dumazet
2010-12-18T17:35:15Z

One iptables invocation with 135000 rules takes 35 seconds of cpu time
on a recent server, using a 32bit distro and a 64bit kernel.

We eventually trigger NMI/RCU watchdog.

INFO: rcu_sched_state detected stall on CPU 3 (t=6000 jiffies)

COMPAT mode has quadratic behavior and consume 16 bytes of memory per
rule.

Switch the xt_compat algos to use an array instead of list, and use a
binary search to locate an offset in the sorted array.

This halves memory need (8 bytes per rule), and removes quadratic
behavior [ O(N*N) -> O(N*log2(N)) ]

Time of iptables goes from 35 s to 150 ms.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
include/linux/netfilter/x_tables.h | 3
net/bridge/netfilter/ebtables.c | 1
net/ipv4/netfilter/arp_tables.c | 2
net/ipv4/netfilter/ip_tables.c | 2
net/ipv6/netfilter/ip6_tables.c | 2
net/netfilter/x_tables.c | 82 +++++++++++++++------------
6 files changed, 57 insertions(+), 35 deletions(-)

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index 742bec0..0f04d98 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -611,8 +611,9 @@ struct _compat_xt_align {
extern void xt_compat_lock(u_int8_t af);
extern void xt_compat_unlock(u_int8_t af);

-extern int xt_compat_add_offset(u_int8_t af, unsigned int offset, short delta);
+extern int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta);
extern void xt_compat_flush_offsets(u_int8_t af);
+extern void xt_compat_init_offsets(u_int8_t af, unsigned int number);
extern int xt_compat_calc_jump(u_int8_t af, unsigned int offset);

extern int xt_compat_match_offset(const struct xt_match *match);
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index cbc9f39..2bf2fb2 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1764,6 +1764,7 @@ static int compat_table_info(const struct ebt_table_info *info,

newinfo->entries_size = size;

+ xt_compat_init_offsets(AF_INET, info->nentries);
return EBT_ENTRY_ITERATE(entries, size, compat_calc_entry, info,
entries, newinfo);
}
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 3fac340..47e5178 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -883,6 +883,7 @@ static int compat_table_info(const struct xt_table_info *info,
memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
newinfo->initial_entries = 0;
loc_cpu_entry = info->entries[raw_smp_processor_id()];
+ xt_compat_init_offsets(NFPROTO_ARP, info->number);
xt_entry_foreach(iter, loc_cpu_entry, info->size) {
ret = compat_calc_entry(iter, info, loc_cpu_entry, newinfo);
if (ret != 0)
@@ -1350,6 +1351,7 @@ static int translate_compat_table(const char *name,
duprintf("translate_compat_table: size %u\n", info->size);
j = 0;
xt_compat_lock(NFPROTO_ARP);
+ xt_compat_init_offsets(NFPROTO_ARP, number);
/* Walk through entries, checking offsets. */
xt_entry_foreach(iter0, entry0, total_size) {
ret = check_compat_entry_size_and_hooks(iter0, info, &size,
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index a846d63..c5a75d7 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1080,6 +1080,7 @@ static int compat_table_info(const struct xt_table_info *info,
memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
newinfo->initial_entries = 0;
loc_cpu_entry = info->entries[raw_smp_processor_id()];
+ xt_compat_init_offsets(AF_INET, info->number);
xt_entry_foreach(iter, loc_cpu_entry, info->size) {
ret = compat_calc_entry(iter, info, loc_cpu_entry, newinfo);
if (ret != 0)
@@ -1681,6 +1682,7 @@ translate_compat_table(struct net *net,
duprintf("translate_compat_table: size %u\n", info->size);
j = 0;
xt_compat_lock(AF_INET);
+ xt_compat_init_offsets(AF_INET, number);
/* Walk through entries, checking offsets. */
xt_entry_foreach(iter0, entry0, total_size) {
ret = check_compat_entry_size_and_hooks(iter0, info, &size,
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 4555823..0c9973a 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1093,6 +1093,7 @@ static int compat_table_info(const struct xt_table_info *info,
memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
newinfo->initial_entries = 0;
loc_cpu_entry = info->entries[raw_smp_processor_id()];
+ xt_compat_init_offsets(AF_INET6, info->number);
xt_entry_foreach(iter, loc_cpu_entry, info->size) {
ret = compat_calc_entry(iter, info, loc_cpu_entry, newinfo);
if (ret != 0)
@@ -1696,6 +1697,7 @@ translate_compat_table(struct net *net,
duprintf("translate_compat_table: size %u\n", info->size);
j = 0;
xt_compat_lock(AF_INET6);
+ xt_compat_init_offsets(AF_INET6, number);
/* Walk through entries, checking offsets. */
xt_entry_foreach(iter0, entry0, total_size) {
ret = check_compat_entry_size_and_hooks(iter0, info, &size,
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 8046350..75182ed 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -38,9 +38,8 @@ MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");
#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))

struct compat_delta {
- struct compat_delta *next;
- unsigned int offset;
- int delta;
+ unsigned int offset; /* offset in kernel */
+ int delta; /* delta in 32bit user land */
};

struct xt_af {
@@ -49,7 +48,9 @@ struct xt_af {
struct list_head target;
#ifdef CONFIG_COMPAT
struct mutex compat_mutex;
- struct compat_delta *compat_offsets;
+ struct compat_delta *compat_tab;
+ unsigned int number; /* number of slots in compat_tab[] */
+ unsigned int cur; /* number of used slots in compat_tab[] */
#endif
};

@@ -414,54 +415,67 @@ int xt_check_match(struct xt_mtchk_param *par,
EXPORT_SYMBOL_GPL(xt_check_match);

#ifdef CONFIG_COMPAT
-int xt_compat_add_offset(u_int8_t af, unsigned int offset, short delta)
+int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta)
{
- struct compat_delta *tmp;
+ struct xt_af *xp = &xt[af];

- tmp = kmalloc(sizeof(struct compat_delta), GFP_KERNEL);
- if (!tmp)
- return -ENOMEM;
+ if (!xp->compat_tab) {
+ if (!xp->number)
+ return -EINVAL;
+ xp->compat_tab = vmalloc(sizeof(struct compat_delta) * xp->number);
+ if (!xp->compat_tab)
+ return -ENOMEM;
+ xp->cur = 0;
+ }

- tmp->offset = offset;
- tmp->delta = delta;
+ if (xp->cur >= xp->number)
+ return -EINVAL;

- if (xt[af].compat_offsets) {
- tmp->next = xt[af].compat_offsets->next;
- xt[af].compat_offsets->next = tmp;
- } else {
- xt[af].compat_offsets = tmp;
- tmp->next = NULL;
- }
+ if (xp->cur)
+ delta += xp->compat_tab[xp->cur - 1].delta;
+ xp->compat_tab[xp->cur].offset = offset;
+ xp->compat_tab[xp->cur].delta = delta;
+ xp->cur++;
return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_add_offset);

void xt_compat_flush_offsets(u_int8_t af)
{
- struct compat_delta *tmp, *next;
-
- if (xt[af].compat_offsets) {
- for (tmp = xt[af].compat_offsets; tmp; tmp = next) {
- next = tmp->next;
- kfree(tmp);
- }
- xt[af].compat_offsets = NULL;
+ if (xt[af].compat_tab) {
+ vfree(xt[af].compat_tab);
+ xt[af].compat_tab = NULL;
+ xt[af].number = 0;
}
}
EXPORT_SYMBOL_GPL(xt_compat_flush_offsets);

int xt_compat_calc_jump(u_int8_t af, unsigned int offset)
{
- struct compat_delta *tmp;
- int delta;
-
- for (tmp = xt[af].compat_offsets, delta = 0; tmp; tmp = tmp->next)
- if (tmp->offset < offset)
- delta += tmp->delta;
- return delta;
+ struct compat_delta *tmp = xt[af].compat_tab;
+ int mid, left = 0, right = xt[af].cur - 1;
+
+ while (left <= right) {
+ mid = (left + right) >> 1;
+ if (offset > tmp[mid].offset)
+ left = mid + 1;
+ else if (offset < tmp[mid].offset)
+ right = mid - 1;
+ else
+ return mid ? tmp[mid - 1].delta : 0;
+ }
+ WARN_ON_ONCE(1);
+ return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_calc_jump);

+void xt_compat_init_offsets(u_int8_t af, unsigned int number)
+{
+ xt[af].number = number;
+ xt[af].cur = 0;
+}
+EXPORT_SYMBOL(xt_compat_init_offsets);
+
int xt_compat_match_offset(const struct xt_match *match)
{
u_int16_t csize = match->compatsize ? : match->matchsize;
@@ -1337,7 +1351,7 @@ static int __init xt_init(void)
mutex_init(&xt[i].mutex);
#ifdef CONFIG_COMPAT
mutex_init(&xt[i].compat_mutex);
- xt[i].compat_offsets = NULL;
+ xt[i].compat_tab = NULL;
#endif
INIT_LIST_HEAD(&xt[i].target);
INIT_LIST_HEAD(&xt[i].match);