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 925C3C433EF for ; Tue, 10 May 2022 15:55:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346834AbiEJP6X (ORCPT ); Tue, 10 May 2022 11:58:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34722 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346367AbiEJPu7 (ORCPT ); Tue, 10 May 2022 11:50:59 -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 F3BB828ABAA; Tue, 10 May 2022 08:45:09 -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 80706614AF; Tue, 10 May 2022 15:45:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8B63C385CB; Tue, 10 May 2022 15:45:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1652197508; bh=2OX837V48LPWy+fohNmbgAQwoavPUJVKqMpgPMB4Acg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ePpNm/iiAm5IsIQnmP9iykSNAPrmCbCsv6rmrFRooSwffD3bIjErVEsfaoh3V9YIT HdX7XNWBxL/cupuzxBcbMJWxs+pvyyfpSl9G31a1ce0500JgUW1+ofS6EQpmGWMAH8 71kRmGIl5yQDgVdsyL4kBdkymux1hGgc1SWphZApXxqTMIuzcqgPV7lpsXgWmc8+np edQi7QMVINLZsb8imsPY4Mr/NW7GBwmQ4007z5tgQRudT4c8GwQFtYBI2J9WRIKEK8 FAhil2PhKbe+2iR8JdHveZOX3d4XsKXC+Zi8bxlZjf//HI1TyQiXgfkeVOj1p3YmKW xYY4pIDtJpoJQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Willy Tarreau , Amit Klein , Eric Dumazet , Jakub Kicinski , Sasha Levin , davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 18/19] tcp: drop the hash_32() part from the index calculation Date: Tue, 10 May 2022 11:44:28 -0400 Message-Id: <20220510154429.153677-18-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220510154429.153677-1-sashal@kernel.org> References: <20220510154429.153677-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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; -- 2.35.1