From patchwork Mon May 16 19:36:35 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 573770 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 A11A3C433F5 for ; Mon, 16 May 2022 20:04:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346701AbiEPUEV (ORCPT ); Mon, 16 May 2022 16:04:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41372 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348344AbiEPT6f (ORCPT ); Mon, 16 May 2022 15:58:35 -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 EED8843ACF; Mon, 16 May 2022 12:50:32 -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 8E3CA60C6F; Mon, 16 May 2022 19:50:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B9B2C36AE9; Mon, 16 May 2022 19:50:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1652730632; bh=2OX837V48LPWy+fohNmbgAQwoavPUJVKqMpgPMB4Acg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LSZLhBAton9UfQV6N9mHqMRJZgc1e4W+Z4o/gvd0LZalcLlBekcCAjAh+3qVEIMu5 IopFJqpR7On5f+bpmdt4IwwjCaEijAR0wkSj/bf6U3P7QRhLpbQaFcck2DdFFTjhuM VU3q0l0fm4iQPBlckhXIRE04UyU2LnyEYjRj/bnQ= 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 , Sasha Levin Subject: [PATCH 5.15 061/102] tcp: drop the hash_32() part from the index calculation Date: Mon, 16 May 2022 21:36:35 +0200 Message-Id: <20220516193625.747686026@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220516193623.989270214@linuxfoundation.org> References: <20220516193623.989270214@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Willy Tarreau [ Upstream commit e8161345ddbb66e449abde10d2fdce93f867eba9 ] 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 Signed-off-by: Sasha Levin --- 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 f76e4ac1ba3a..ee9c587031b4 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;