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>

2 files changed, 14 insertions, 23 deletions

diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c
index 38f03f75a636..8103bef78e44 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 fc70a49c0afd..768d01ff1fea 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)