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[68.111.84.250]) by smtp.gmail.com with ESMTPSA id r3sm4148271pfl.67.2020.10.16.19.35.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Oct 2020 19:36:00 -0700 (PDT) To: Christian Eggers , Andrew Lunn , Vivien Didelot , Vladimir Oltean , Jakub Kicinski , Kurt Kanzenbach Cc: "David S . Miller" , Woojung Huh , Microchip Linux Driver Support , netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20201016200226.23994-1-ceggers@arri.de> <20201016200226.23994-2-ceggers@arri.de> From: Florian Fainelli Subject: Re: [PATCH net-next 1/3] net: dsa: don't pass cloned skb's to drivers xmit function Message-ID: <3b14e77c-9307-356e-b1cf-d9e9e51716e5@gmail.com> Date: Fri, 16 Oct 2020 19:35:58 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.3.2 MIME-Version: 1.0 In-Reply-To: <20201016200226.23994-2-ceggers@arri.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 10/16/2020 1:02 PM, Christian Eggers wrote: > Ensure that the skb is not cloned and has enough tail room for the tail > tag. This code will be removed from the drivers in the next commits. > > Signed-off-by: Christian Eggers > --- [snip] > + /* We have to pad he packet to the minimum Ethernet frame size, > + * if necessary, before adding the trailer (tail tagging only). > + */ > + padlen = (skb->len >= ETH_ZLEN) ? 0 : ETH_ZLEN - skb->len; > + > + /* To keep the slave's xmit() methods simple, don't pass cloned skbs to > + * them. Additionally ensure, that suitable room for tail tagging is > + * available. > + */ > + if (skb_cloned(skb) || > + (p->tail_tag && skb_tailroom(skb) < (padlen + p->overhead))) { > + struct sk_buff *nskb; > + > + nskb = alloc_skb(NET_IP_ALIGN + skb->len + > + padlen + p->overhead, GFP_ATOMIC); > + if (!nskb) { > + kfree_skb(skb); > + return NETDEV_TX_OK; > + } > + skb_reserve(nskb, NET_IP_ALIGN); > + > + skb_reset_mac_header(nskb); > + skb_set_network_header(nskb, > + skb_network_header(skb) - skb->head); > + skb_set_transport_header(nskb, > + skb_transport_header(skb) - skb->head); > + skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len)); > + consume_skb(skb); > + > + if (padlen) > + skb_put_zero(nskb, padlen); > + > + skb = nskb; > + } Given the low number of tail taggers, maybe this should be a helper function that is used by them where applicable? If nothing else you may want to sprinkle unlikely() conditions to sort of hing the processor that these are unlikely conditions. -- Florian