netfilter 04/62: xtables: obtain random bytes earlier, in checkentry

Patrick McHardy
2010-02-16T14:55:26Z

commit 294188ae32f984a072c64c959354b2f6f52f80a7
Author: Jan Engelhardt <jengelh@medozas.de>
Date: Mon Jan 4 16:28:38 2010 +0100

netfilter: xtables: obtain random bytes earlier, in checkentry

We can initialize the random hash bytes on checkentry. This is
preferable since it is outside the hot path.

Reference: http://bugzilla.netfilter.org/show_bug.cgi?id=621
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c
index 38f03f7..8103bef 100644
--- a/net/netfilter/xt_connlimit.c
+++ b/net/netfilter/xt_connlimit.c
@@ -40,15 +40,11 @@ struct xt_connlimit_data {
spinlock_t lock;
};

-static u_int32_t connlimit_rnd;
-static bool connlimit_rnd_inited;
+static u_int32_t connlimit_rnd __read_mostly;
+static bool connlimit_rnd_inited __read_mostly;

static inline unsigned int connlimit_iphash(__be32 addr)
{
- if (unlikely(!connlimit_rnd_inited)) {
- get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
- connlimit_rnd_inited = true;
- }
return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
}

@@ -59,11 +55,6 @@ connlimit_iphash6(const union nf_inet_addr *addr,
union nf_inet_addr res;
unsigned int i;

- if (unlikely(!connlimit_rnd_inited)) {
- get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
- connlimit_rnd_inited = true;
- }
-
for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
res.ip6[i] = addr->ip6[i] & mask->ip6[i];

@@ -226,6 +217,10 @@ static bool connlimit_mt_check(const struct xt_mtchk_param *par)
struct xt_connlimit_info *info = par->matchinfo;
unsigned int i;

+ if (unlikely(!connlimit_rnd_inited)) {
+ get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
+ connlimit_rnd_inited = true;
+ }
if (nf_ct_l3proto_try_module_get(par->family) < 0) {
printk(KERN_WARNING "cannot load conntrack support for "
"address family %u\n", par->family);
diff --git a/net/netfilter/xt_recent.c b/net/netfilter/xt_recent.c
index fc70a49..768d01f 100644
--- a/net/netfilter/xt_recent.c
+++ b/net/netfilter/xt_recent.c
@@ -90,25 +90,17 @@ static struct proc_dir_entry *recent_proc_dir;
static const struct file_operations recent_old_fops, recent_mt_fops;
#endif

-static u_int32_t hash_rnd;
-static bool hash_rnd_initted;
+static u_int32_t hash_rnd __read_mostly;
+static bool hash_rnd_inited __read_mostly;

-static unsigned int recent_entry_hash4(const union nf_inet_addr *addr)
+static inline unsigned int recent_entry_hash4(const union nf_inet_addr *addr)
{
- if (!hash_rnd_initted) {
- get_random_bytes(&hash_rnd, sizeof(hash_rnd));
- hash_rnd_initted = true;
- }
return jhash_1word((__force u32)addr->ip, hash_rnd) &
(ip_list_hash_size - 1);
}

-static unsigned int recent_entry_hash6(const union nf_inet_addr *addr)
+static inline unsigned int recent_entry_hash6(const union nf_inet_addr *addr)
{
- if (!hash_rnd_initted) {
- get_random_bytes(&hash_rnd, sizeof(hash_rnd));
- hash_rnd_initted = true;
- }
return jhash2((u32 *)addr->ip6, ARRAY_SIZE(addr->ip6), hash_rnd) &
(ip_list_hash_size - 1);
}
@@ -287,6 +279,10 @@ static bool recent_mt_check(const struct xt_mtchk_param *par)
unsigned i;
bool ret = false;

+ if (unlikely(!hash_rnd_inited)) {
+ get_random_bytes(&hash_rnd, sizeof(hash_rnd));
+ hash_rnd_inited = true;
+ }
if (hweight8(info->check_set &
(XT_RECENT_SET | XT_RECENT_REMOVE |
XT_RECENT_CHECK | XT_RECENT_UPDATE)) != 1)