netfilter: x_table: speedup compat operations
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>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 80463507..ee5de3a 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -38,9 +38,8 @@
#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 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 @@
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;
-
- tmp->offset = offset;
- tmp->delta = delta;
-
- 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->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;
}
+
+ if (xp->cur >= xp->number)
+ return -EINVAL;
+
+ 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;
+ struct compat_delta *tmp = xt[af].compat_tab;
+ int mid, left = 0, right = xt[af].cur - 1;
- for (tmp = xt[af].compat_offsets, delta = 0; tmp; tmp = tmp->next)
- if (tmp->offset < offset)
- delta += tmp->delta;
- return delta;
+ 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 @@
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);
