From patchwork Thu Jul 27 15:25:11 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Gobert X-Patchwork-Id: 13330283 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C41D317AC7 for ; Thu, 27 Jul 2023 15:25:38 +0000 (UTC) Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EE832109; Thu, 27 Jul 2023 08:25:36 -0700 (PDT) Received: by mail-wm1-x329.google.com with SMTP id 5b1f17b1804b1-3fdfd4c749dso6668375e9.3; Thu, 27 Jul 2023 08:25:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690471535; x=1691076335; h=user-agent:content-disposition:mime-version:message-id:subject:to :from:date:from:to:cc:subject:date:message-id:reply-to; bh=9HoTtUL2U0F8o9w8gLl2KsDdaZrr/V4+iLv0Ml6w3sE=; b=LlFVC0KQ2PYUt+lVm/JZTmUyvFrp1+yS41YYHy3Q4P8vRdt1lYKNwmI8rmymBGx7AC NQgbOsxPtdmHvtmNLMUp3Zs5ymjkO2tJ2YUo8p9XrUWozwehrNk4ytGOms/wDdN0wCJr 8jXVHMJ7PwAn/MhbNpuOSvHt1OaSYUVr3jEtPVRAt7wzlH5lbh/tiyklpr0JgGYsGYPe DZuLm7TIrzthfombrd4O+dV+MSl0yDHsue04iZbJ0Td6pP0M60yTclwT+tDh6QIGXWrG xssn5OL3hEQr0SZKnr7OUtXX0kk4TiawL3EfuYwiXv9ayrVYZMCUosYc1T+dS3SZTAzg g+KA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690471535; x=1691076335; h=user-agent:content-disposition:mime-version:message-id:subject:to :from:date:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=9HoTtUL2U0F8o9w8gLl2KsDdaZrr/V4+iLv0Ml6w3sE=; b=YeQVvNQqlw+Lpia0omFVqKoX6rkjTb6CyUlq2CrPF8FA/lWVV6b/EQfjMMb+a4Y2/1 z7YtUi1Fo44fAfnPmGec/5OY1ilqz7eOIdXAGx03jwlWqHi9XEx6Sw99R0QPArClAQc3 EnBGqgs/+rcB1qIv/S1xb0Rf9qmv4pcUES4x92a8e6i03OQDnziVaxrygUAAAsW8ZD7X e4u6ZROs8tWemuV6u2UAwQL4P+mS1tJYkDENpbWaagq9O/uLbUpMOHpI6flpb6ooaoz2 QxSDVOpCh3xSsyQN5SoX949+Rif3OXvSOIvZy9zS5fcJ8W2mFCLV94D+9gZq+qMEHGuP zMhg== X-Gm-Message-State: ABy/qLbBvIPi/XROYfQTBaMUkzGgVnWPoitmXALIZIIi+SCft5mAkBGU +SOESuZHkVP5C1p+TxPY++o= X-Google-Smtp-Source: APBJJlEZjvknLN6rnzSYDeqINRAD16bO1ZVoVhxgYKe4qK/Z15Wln9t3o7ki7Ev/F6QioQMzKRPaMA== X-Received: by 2002:adf:e8c5:0:b0:313:e971:53af with SMTP id k5-20020adfe8c5000000b00313e97153afmr1952783wrn.32.1690471534575; Thu, 27 Jul 2023 08:25:34 -0700 (PDT) Received: from debian ([89.238.191.199]) by smtp.gmail.com with ESMTPSA id k8-20020a056000004800b003141a3c4353sm2385404wrx.30.2023.07.27.08.25.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jul 2023 08:25:34 -0700 (PDT) Date: Thu, 27 Jul 2023 17:25:11 +0200 From: Richard Gobert To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, willemdebruijn.kernel@gmail.com, dsahern@kernel.org, tom@herbertland.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, gal@nvidia.com Subject: [PATCH v3 0/1] net: gro: fix misuse of CB in udp socket lookup Message-ID: <20230727152503.GA32010@debian> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net GRO stack uses `udp_lib_lookup_skb` which relies on IP/IPv6 CB's info, and at the GRO stage, CB holds `napi_gro_cb` info. Specifically, `udp_lib_lookup_skb` tries to fetch `iff` and `flags` information from the CB, to find the relevant udp tunnel socket (GENEVE/VXLAN/..). Up until a patch I submitted recently [0], it worked merely by luck, due to the layouts of `napi_gro_cb` and IP6CB. AFAIU it worked because: `IP6CB(skb)->flags` is at offset 16 inside IP6CB: - Before the patch: `flags` was mapped to `flush`. - After the patch: `flags` was mapped to `data_offset`. `IP6CB(skb)->iff` is at offset 0 inside IP6CB: - Before the patch: `iif` was mapped to `frag0`. - After the patch: `iif` was mapped to a union of `frag0` and `last`. After my patch, on the receive phase, while `data_offset` is 40 (since IPv6 header is 40 bytes), `inet_iif` calls `ipv6_l3mdev_skb`, which checks whether `IP6CB(skb)->flags`'s `IP6SKB_L3SLAVE` bit is on or off (in our case its off). If it is off, `inet_iif` returns `IP6CB(skb)->iif`, which is mapped to `napi_gro_cb->frag0`, making `inet_iif` return 0 most of the times. `inet_sdif` returns zero due to a similar reason caused by `data_offset` being equal to 40 (and less than 64). On the other hand, the complete phase behaves differently. `data_offset` is usually greater than 64 and less than 128 so the `IP6SKB_L3SLAVE` flag is on. Thus, `inet_sdif` returns `IP6CB(skb)->iif`, which is mapped to `last` which contains a pointer. This causes `udp_sk_bound_dev_eq` to fail, which leads to `udp6_lib_lookup2` failing and not returning a socket. This leads the receive phase of GRO to find the right socket, and on the complete phase, it fails to find it and makes the throughput go down to nearly zero. Before [0] `flags` was mapped to `flush`. `flush`'s possible values were 1 and 0, making `inet6_iff` always returning `skb->skb_iif` and `inet6_sdif` returning 0, and leading to `udp_sk_bound_dev_eq` returning true. A fix is to not rely on CB, and get `iff` and `sdif` using skb->dev. l3mdev case requires special attention since it has a master and a slave device. [0] https://lore.kernel.org/netdev/20230601160924.GA9194@debian/ Changelog: v2 -> v3: * change functions to static inline in the header file v1 -> v2: * make functions inline * fix logical bug * add a comment when we can use the new functions * checkpatch fixes Richard Gobert (1): net: gro: fix misuse of CB in udp socket lookup include/net/gro.h | 43 ++++++++++++++++++++++++++++++++++++++++++ net/ipv4/udp.c | 8 ++++++-- net/ipv4/udp_offload.c | 7 +++++-- net/ipv6/udp.c | 8 ++++++-- net/ipv6/udp_offload.c | 7 +++++-- 5 files changed, 65 insertions(+), 8 deletions(-)