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Message-Id: <20210924221113.348767-5-pablo@netfilter.org>
Date: Sat, 25 Sep 2021 00:11:02 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org
Subject: [PATCH net 04/15] netfilter: conntrack: make max chain length random
From: Florian Westphal <fw@...len.de>
Similar to commit 67d6d681e15b
("ipv4: make exception cache less predictible"):
Use a random drop length to make it harder to detect when entries were
hashed to same bucket list.
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
net/netfilter/nf_conntrack_core.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 94e18fb9690d..91b7edaa635c 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -77,7 +77,8 @@ static __read_mostly bool nf_conntrack_locks_all;
#define GC_SCAN_INTERVAL (120u * HZ)
#define GC_SCAN_MAX_DURATION msecs_to_jiffies(10)
-#define MAX_CHAINLEN 64u
+#define MIN_CHAINLEN 8u
+#define MAX_CHAINLEN (32u - MIN_CHAINLEN)
static struct conntrack_gc_work conntrack_gc_work;
@@ -842,6 +843,7 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
unsigned int hash, reply_hash;
struct nf_conntrack_tuple_hash *h;
struct hlist_nulls_node *n;
+ unsigned int max_chainlen;
unsigned int chainlen = 0;
unsigned int sequence;
int err = -EEXIST;
@@ -857,13 +859,15 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
} while (nf_conntrack_double_lock(net, hash, reply_hash, sequence));
+ max_chainlen = MIN_CHAINLEN + prandom_u32_max(MAX_CHAINLEN);
+
/* See if there's one in the list already, including reverse */
hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[hash], hnnode) {
if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
zone, net))
goto out;
- if (chainlen++ > MAX_CHAINLEN)
+ if (chainlen++ > max_chainlen)
goto chaintoolong;
}
@@ -873,7 +877,7 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,
zone, net))
goto out;
- if (chainlen++ > MAX_CHAINLEN)
+ if (chainlen++ > max_chainlen)
goto chaintoolong;
}
@@ -1103,8 +1107,8 @@ nf_ct_resolve_clash(struct sk_buff *skb, struct nf_conntrack_tuple_hash *h,
int
__nf_conntrack_confirm(struct sk_buff *skb)
{
+ unsigned int chainlen = 0, sequence, max_chainlen;
const struct nf_conntrack_zone *zone;
- unsigned int chainlen = 0, sequence;
unsigned int hash, reply_hash;
struct nf_conntrack_tuple_hash *h;
struct nf_conn *ct;
@@ -1168,6 +1172,7 @@ __nf_conntrack_confirm(struct sk_buff *skb)
goto dying;
}
+ max_chainlen = MIN_CHAINLEN + prandom_u32_max(MAX_CHAINLEN);
/* See if there's one in the list already, including reverse:
NAT could have grabbed it without realizing, since we're
not in the hash. If there is, we lost race. */
@@ -1175,7 +1180,7 @@ __nf_conntrack_confirm(struct sk_buff *skb)
if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
zone, net))
goto out;
- if (chainlen++ > MAX_CHAINLEN)
+ if (chainlen++ > max_chainlen)
goto chaintoolong;
}
@@ -1184,7 +1189,7 @@ __nf_conntrack_confirm(struct sk_buff *skb)
if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,
zone, net))
goto out;
- if (chainlen++ > MAX_CHAINLEN) {
+ if (chainlen++ > max_chainlen) {
chaintoolong:
nf_ct_add_to_dying_list(ct);
NF_CT_STAT_INC(net, chaintoolong);
--
2.30.2
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