From: Willy Tarreau <w@1wt.eu>
To: netdev@vger.kernel.org
Cc: David Miller <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Eric Dumazet <edumazet@google.com>,
Moshe Kol <moshe.kol@mail.huji.ac.il>,
Yossi Gilad <yossi.gilad@mail.huji.ac.il>,
Amit Klein <aksecurity@gmail.com>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
linux-kernel@vger.kernel.org, Willy Tarreau <w@1wt.eu>
Subject: [PATCH v3 net 7/7] tcp: drop the hash_32() part from the index calculation
Date: Mon, 2 May 2022 10:46:14 +0200 [thread overview]
Message-ID: <20220502084614.24123-8-w@1wt.eu> (raw)
In-Reply-To: <20220502084614.24123-1-w@1wt.eu>
In commit 190cc82489f4 ("tcp: change source port randomizarion at
connect() time"), the table_perturb[] array was introduced and an
index was taken from the port_offset via hash_32(). But it turns
out that hash_32() performs a multiplication while the input here
comes from the output of SipHash in secure_seq, that is well
distributed enough to avoid the need for yet another hash.
Suggested-by: Amit Klein <aksecurity@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
net/ipv4/inet_hashtables.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index cc5f66328b47..a5d57fa679ca 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -778,7 +778,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
net_get_random_once(table_perturb,
INET_TABLE_PERTURB_SIZE * sizeof(*table_perturb));
- index = hash_32(port_offset, INET_TABLE_PERTURB_SHIFT);
+ index = port_offset & (INET_TABLE_PERTURB_SIZE - 1);
offset = READ_ONCE(table_perturb[index]) + (port_offset >> 32);
offset %= remaining;
--
2.17.5
next prev parent reply other threads:[~2022-05-02 8:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-02 8:46 [PATCH v3 net 0/7] insufficient TCP source port randomness Willy Tarreau
2022-05-02 8:46 ` [PATCH v3 net 1/7] secure_seq: use the 64 bits of the siphash for port offset calculation Willy Tarreau
2022-05-02 8:46 ` [PATCH v3 net 2/7] tcp: use different parts of the port_offset for index and offset Willy Tarreau
2022-05-02 8:46 ` [PATCH v3 net 3/7] tcp: resalt the secret every 10 seconds Willy Tarreau
2022-05-02 8:46 ` [PATCH v3 net 4/7] tcp: add small random increments to the source port Willy Tarreau
2022-05-02 8:46 ` [PATCH v3 net 5/7] tcp: dynamically allocate the perturb table used by source ports Willy Tarreau
2022-05-02 8:46 ` [PATCH v3 net 6/7] tcp: increase source port perturb table to 2^16 Willy Tarreau
2022-05-02 8:46 ` Willy Tarreau [this message]
2022-05-05 2:50 ` [PATCH v3 net 0/7] insufficient TCP source port randomness patchwork-bot+netdevbpf
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