Since we don't change the tuple in the original direction, we can save it
in ct->tuplehash[IP_CT_DIR_REPLY].hnode.pprev for __nf_conntrack_confirm()
use.
__hash_conntrack() is split into two steps: hash_conntrack_raw() is used
to get the raw hash, and __hash_bucket() is used to get the bucket id.
In SYN-flood case, early_drop() doesn't need to recompute the hash again.
Signed-off-by: Changli Gao <xiaosuo@xxxxxxxxx>
---
v6: some advices from Patrick.
v5: respin it due to the change of 1/2.
v4: init rnd when allocating conntrack.
v3: define static variable rnd out of the function ____hash_conntrack(),
and call get_random_bytes() until we get a non-zero random int.
v2: use cmpxchg() to save 2 variables.
net/netfilter/nf_conntrack_core.c | 112 ++++++++++++++++++++++++++------------
1 file changed, 78 insertions(+), 34 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 4c0ad9b..1eacf8d 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -67,29 +67,40 @@ EXPORT_PER_CPU_SYMBOL(nf_conntrack_untracked);
static unsigned int nf_conntrack_hash_rnd __read_mostly;
-static u_int32_t __hash_conntrack(const struct nf_conntrack_tuple *tuple,
- u16 zone, unsigned int size, unsigned int rnd)
+static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple, u16 zone)
{
unsigned int n;
- u_int32_t h;
/* The direction must be ignored, so we hash everything up to the
* destination ports (which is a multiple of 4) and treat the last
* three bytes manually.
*/
n = (sizeof(tuple->src) + sizeof(tuple->dst.u3)) / sizeof(u32);
- h = jhash2((u32 *)tuple, n,
- zone ^ rnd ^ (((__force __u16)tuple->dst.u.all << 16) |
- tuple->dst.protonum));
+ return jhash2((u32 *)tuple, n, zone ^ nf_conntrack_hash_rnd ^
+ (((__force __u16)tuple->dst.u.all << 16) |
+ tuple->dst.protonum));
+}
+
+static u32 __hash_bucket(u32 hash, unsigned int size)
+{
+ return ((u64)hash * size) >> 32;
+}
+
+static u32 hash_bucket(u32 hash, const struct net *net)
+{
+ return __hash_bucket(hash, net->ct.htable_size);
+}
- return ((u64)h * size) >> 32;
+static u_int32_t __hash_conntrack(const struct nf_conntrack_tuple *tuple,
+ u16 zone, unsigned int size)
+{
+ return __hash_bucket(hash_conntrack_raw(tuple, zone), size);
}
static inline u_int32_t hash_conntrack(const struct net *net, u16 zone,
const struct nf_conntrack_tuple *tuple)
{
- return __hash_conntrack(tuple, zone, net->ct.htable_size,
- nf_conntrack_hash_rnd);
+ return __hash_conntrack(tuple, zone, net->ct.htable_size);
}
bool
@@ -291,20 +302,20 @@ static void death_by_timeout(unsigned long ul_conntrack)
* OR
* - Caller must lock nf_conntrack_lock before calling this function
*/
-struct nf_conntrack_tuple_hash *
-__nf_conntrack_find(struct net *net, u16 zone,
- const struct nf_conntrack_tuple *tuple)
+static struct nf_conntrack_tuple_hash *
+____nf_conntrack_find(struct net *net, u16 zone,
+ const struct nf_conntrack_tuple *tuple, u32 hash)
{
struct nf_conntrack_tuple_hash *h;
struct hlist_nulls_node *n;
- unsigned int hash = hash_conntrack(net, zone, tuple);
+ unsigned int bucket = hash_bucket(hash, net);
/* Disable BHs the entire time since we normally need to disable them
* at least once for the stats anyway.
*/
local_bh_disable();
begin:
- hlist_nulls_for_each_entry_rcu(h, n, &net->ct.hash[hash], hnnode) {
+ hlist_nulls_for_each_entry_rcu(h, n, &net->ct.hash[bucket], hnnode) {
if (nf_ct_tuple_equal(tuple, &h->tuple) &&
nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)) == zone) {
NF_CT_STAT_INC(net, found);
@@ -318,7 +329,7 @@ begin:
* not the expected one, we must restart lookup.
* We probably met an item that was moved to another chain.
*/
- if (get_nulls_value(n) != hash) {
+ if (get_nulls_value(n) != bucket) {
NF_CT_STAT_INC(net, search_restart);
goto begin;
}
@@ -326,19 +337,27 @@ begin:
return NULL;
}
+
+struct nf_conntrack_tuple_hash *
+__nf_conntrack_find(struct net *net, u16 zone,
+ const struct nf_conntrack_tuple *tuple)
+{
+ return ____nf_conntrack_find(net, zone, tuple,
+ hash_conntrack_raw(tuple, zone));
+}
EXPORT_SYMBOL_GPL(__nf_conntrack_find);
/* Find a connection corresponding to a tuple. */
-struct nf_conntrack_tuple_hash *
-nf_conntrack_find_get(struct net *net, u16 zone,
- const struct nf_conntrack_tuple *tuple)
+static struct nf_conntrack_tuple_hash *
+__nf_conntrack_find_get(struct net *net, u16 zone,
+ const struct nf_conntrack_tuple *tuple, u32 hash)
{
struct nf_conntrack_tuple_hash *h;
struct nf_conn *ct;
rcu_read_lock();
begin:
- h = __nf_conntrack_find(net, zone, tuple);
+ h = ____nf_conntrack_find(net, zone, tuple, hash);
if (h) {
ct = nf_ct_tuplehash_to_ctrack(h);
if (unlikely(nf_ct_is_dying(ct) ||
@@ -356,6 +375,14 @@ begin:
return h;
}
+
+struct nf_conntrack_tuple_hash *
+nf_conntrack_find_get(struct net *net, u16 zone,
+ const struct nf_conntrack_tuple *tuple)
+{
+ return __nf_conntrack_find_get(net, zone, tuple,
+ hash_conntrack_raw(tuple, zone));
+}
EXPORT_SYMBOL_GPL(nf_conntrack_find_get);
static void __nf_conntrack_hash_insert(struct nf_conn *ct,
@@ -408,8 +435,11 @@ __nf_conntrack_confirm(struct sk_buff *skb)
return NF_ACCEPT;
zone = nf_ct_zone(ct);
- hash = hash_conntrack(net, zone, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
- repl_hash = hash_conntrack(net, zone, &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
+ /* reuse the hash saved before */
+ hash = *(unsigned long *)&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev;
+ hash = hash_bucket(hash, net);
+ repl_hash = hash_conntrack(net, zone,
+ &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
/* We're not in hash table, and we refuse to set up related
connections for unconfirmed conns. But packet copies and
@@ -566,10 +596,11 @@ static noinline int early_drop(struct net *net, unsigned int hash)
return dropped;
}
-struct nf_conn *nf_conntrack_alloc(struct net *net, u16 zone,
- const struct nf_conntrack_tuple *orig,
- const struct nf_conntrack_tuple *repl,
- gfp_t gfp)
+static struct nf_conn *
+__nf_conntrack_alloc(struct net *net, u16 zone,
+ const struct nf_conntrack_tuple *orig,
+ const struct nf_conntrack_tuple *repl,
+ gfp_t gfp, u32 hash)
{
struct nf_conn *ct;
@@ -585,6 +616,9 @@ struct nf_conn *nf_conntrack_alloc(struct net *net, u16 zone,
get_random_bytes(&rand, sizeof(rand));
} while (!rand);
cmpxchg(&nf_conntrack_hash_rnd, 0, rand);
+
+ /* recompute the hash as nf_conntrack_hash_rnd is initialized */
+ hash = hash_conntrack_raw(orig, zone);
}
/* We don't want any race condition at early drop stage */
@@ -592,8 +626,7 @@ struct nf_conn *nf_conntrack_alloc(struct net *net, u16 zone,
if (nf_conntrack_max &&
unlikely(atomic_read(&net->ct.count) > nf_conntrack_max)) {
- unsigned int hash = hash_conntrack(net, zone, orig);
- if (!early_drop(net, hash)) {
+ if (!early_drop(net, hash_bucket(hash, net))) {
atomic_dec(&net->ct.count);
if (net_ratelimit())
printk(KERN_WARNING
@@ -623,7 +656,8 @@ struct nf_conn *nf_conntrack_alloc(struct net *net, u16 zone,
ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple = *orig;
ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode.pprev = NULL;
ct->tuplehash[IP_CT_DIR_REPLY].tuple = *repl;
- ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev = NULL;
+ /* save hash for reusing when confirming */
+ *(unsigned long *)(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev) = hash;
/* Don't set timer yet: wait for confirmation */
setup_timer(&ct->timeout, death_by_timeout, (unsigned long)ct);
write_pnet(&ct->ct_net, net);
@@ -650,6 +684,14 @@ out_free:
return ERR_PTR(-ENOMEM);
#endif
}
+
+struct nf_conn *nf_conntrack_alloc(struct net *net, u16 zone,
+ const struct nf_conntrack_tuple *orig,
+ const struct nf_conntrack_tuple *repl,
+ gfp_t gfp)
+{
+ return __nf_conntrack_alloc(net, zone, orig, repl, gfp, 0);
+}
EXPORT_SYMBOL_GPL(nf_conntrack_alloc);
void nf_conntrack_free(struct nf_conn *ct)
@@ -671,7 +713,7 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
struct nf_conntrack_l3proto *l3proto,
struct nf_conntrack_l4proto *l4proto,
struct sk_buff *skb,
- unsigned int dataoff)
+ unsigned int dataoff, u32 hash)
{
struct nf_conn *ct;
struct nf_conn_help *help;
@@ -685,7 +727,8 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
return NULL;
}
- ct = nf_conntrack_alloc(net, zone, tuple, &repl_tuple, GFP_ATOMIC);
+ ct = __nf_conntrack_alloc(net, zone, tuple, &repl_tuple, GFP_ATOMIC,
+ hash);
if (IS_ERR(ct)) {
pr_debug("Can't allocate conntrack.\n");
return (struct nf_conntrack_tuple_hash *)ct;
@@ -762,6 +805,7 @@ resolve_normal_ct(struct net *net, struct nf_conn *tmpl,
struct nf_conntrack_tuple_hash *h;
struct nf_conn *ct;
u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;
+ u32 hash;
if (!nf_ct_get_tuple(skb, skb_network_offset(skb),
dataoff, l3num, protonum, &tuple, l3proto,
@@ -771,10 +815,11 @@ resolve_normal_ct(struct net *net, struct nf_conn *tmpl,
}
/* look for tuple match */
- h = nf_conntrack_find_get(net, zone, &tuple);
+ hash = hash_conntrack_raw(&tuple, zone);
+ h = __nf_conntrack_find_get(net, zone, &tuple, hash);
if (!h) {
h = init_conntrack(net, tmpl, &tuple, l3proto, l4proto,
- skb, dataoff);
+ skb, dataoff, hash);
if (!h)
return NULL;
if (IS_ERR(h))
@@ -1314,8 +1359,7 @@ int nf_conntrack_set_hashsize(const char *val, struct kernel_param *kp)
ct = nf_ct_tuplehash_to_ctrack(h);
hlist_nulls_del_rcu(&h->hnnode);
bucket = __hash_conntrack(&h->tuple, nf_ct_zone(ct),
- hashsize,
- nf_conntrack_hash_rnd);
+ hashsize);
hlist_nulls_add_head_rcu(&h->hnnode, &hash[bucket]);
}
}
--
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