From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47497CCA483 for ; Thu, 23 Jun 2022 18:23:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237491AbiFWSWq (ORCPT ); Thu, 23 Jun 2022 14:22:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234131AbiFWSTG (ORCPT ); Thu, 23 Jun 2022 14:19:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 174226801D; Thu, 23 Jun 2022 10:25:04 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9CCC561F08; Thu, 23 Jun 2022 17:25:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B5C2C341C5; Thu, 23 Jun 2022 17:25:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656005102; bh=pKgidH1iBtYdAQlTT+9cdhSza1ynLiI3QaAdMB6TxqQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lJtkmTiaCg0Mj3ZvVFeqGniUWRYC/FYIgzuF1UWMKmtkS5tNXCsjHmMDHz+e2SJkr j1lBxCRqCQLUrwY6yP87CLHDdXoSUVDMPkfObvCVJez2mT432zht17o1SupTmfdKqL N0g55OTOLAD1c5H7RGI6VR8ZkYRA8NUTzY7X7tWE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Amit Klein , Eric Dumazet , Willy Tarreau , Jakub Kicinski , Ben Hutchings Subject: [PATCH 5.4 09/11] tcp: drop the hash_32() part from the index calculation Date: Thu, 23 Jun 2022 18:45:13 +0200 Message-Id: <20220623164321.470700805@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220623164321.195163701@linuxfoundation.org> References: <20220623164321.195163701@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Willy Tarreau commit e8161345ddbb66e449abde10d2fdce93f867eba9 upstream. 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 Reviewed-by: Eric Dumazet Signed-off-by: Willy Tarreau Signed-off-by: Jakub Kicinski Cc: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- net/ipv4/inet_hashtables.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -727,7 +727,7 @@ int __inet_hash_connect(struct inet_time 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;