From patchwork Tue Feb 2 18:30:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Phil Sutter X-Patchwork-Id: 12062605 X-Patchwork-Delegate: stephen@networkplumber.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23C88C433DB for ; Tue, 2 Feb 2021 18:33:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0EB264F72 for ; Tue, 2 Feb 2021 18:33:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238694AbhBBSdX (ORCPT ); Tue, 2 Feb 2021 13:33:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238522AbhBBSbo (ORCPT ); Tue, 2 Feb 2021 13:31:44 -0500 Received: from orbyte.nwl.cc (orbyte.nwl.cc [IPv6:2001:41d0:e:133a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9228CC061788 for ; Tue, 2 Feb 2021 10:31:03 -0800 (PST) Received: from localhost ([::1]:36592 helo=tatos) by orbyte.nwl.cc with esmtp (Exim 4.94) (envelope-from ) id 1l70S4-0001CD-Ek; Tue, 02 Feb 2021 19:31:00 +0100 From: Phil Sutter To: Stephen Hemminger Cc: netdev@vger.kernel.org, Jamal Hadi Salim Subject: [iproute PATCH] tc: u32: Fix key folding in sample option Date: Tue, 2 Feb 2021 19:30:51 +0100 Message-Id: <20210202183051.21022-1-phil@nwl.cc> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In between Linux kernel 2.4 and 2.6, key folding for hash tables changed in kernel space. When iproute2 dropped support for the older algorithm, the wrong code was removed and kernel 2.4 folding method remained in place. To get things functional for recent kernels again, restoring the old code alone was not sufficient - additional byteorder fixes were needed. While being at it, make use of ffs() and thereby align the code with how kernel determines the shift width. Fixes: 267480f55383c ("Backout the 2.4 utsname hash patch.") Signed-off-by: Phil Sutter Acked-by: Jamal Hadi Salim --- Initially I considered changing the kernel's key folding instead as the old method didn't just ignore key bits beyond the first byte. Yet I am not sure if this would cause problems with hardware offloading. And given the fact that this simplified key folding is in place since the dawn of 2.6, it is probably not such a big problem anyway. --- tc/f_u32.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/tc/f_u32.c b/tc/f_u32.c index 2ed5254a40d5f..a5747f671e1ea 100644 --- a/tc/f_u32.c +++ b/tc/f_u32.c @@ -978,6 +978,13 @@ show_k: goto show_k; } +static __u32 u32_hash_fold(struct tc_u32_key *key) +{ + __u8 fshift = key->mask ? ffs(ntohl(key->mask)) - 1 : 0; + + return ntohl(key->val & key->mask) >> fshift; +} + static int u32_parse_opt(struct filter_util *qu, char *handle, int argc, char **argv, struct nlmsghdr *n) { @@ -1110,9 +1117,7 @@ static int u32_parse_opt(struct filter_util *qu, char *handle, } NEXT_ARG(); } - hash = sel2.keys[0].val & sel2.keys[0].mask; - hash ^= hash >> 16; - hash ^= hash >> 8; + hash = u32_hash_fold(&sel2.keys[0]); htid = ((hash % divisor) << 12) | (htid & 0xFFF00000); sample_ok = 1; continue;