From: Florian Fainelli <f.fainelli@gmail.com>
To: Christian Eggers <ceggers@arri.de>, Andrew Lunn <andrew@lunn.ch>,
Vivien Didelot <vivien.didelot@gmail.com>,
Vladimir Oltean <olteanv@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
Kurt Kanzenbach <kurt@linutronix.de>
Cc: "David S . Miller" <davem@davemloft.net>,
Woojung Huh <woojung.huh@microchip.com>,
Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 1/3] net: dsa: don't pass cloned skb's to drivers xmit function
Date: Fri, 16 Oct 2020 19:35:58 -0700 [thread overview]
Message-ID: <3b14e77c-9307-356e-b1cf-d9e9e51716e5@gmail.com> (raw)
In-Reply-To: <20201016200226.23994-2-ceggers@arri.de>
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 <ceggers@arri.de>
> ---
[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
next prev parent reply other threads:[~2020-10-17 6:01 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-16 20:02 [PATCH 0/3] net: dsa: move skb reallocation to dsa_slave_xmit Christian Eggers
2020-10-16 20:02 ` [PATCH net-next 1/3] net: dsa: don't pass cloned skb's to drivers xmit function Christian Eggers
2020-10-17 0:48 ` Vladimir Oltean
2020-10-17 18:53 ` Christian Eggers
2020-10-17 19:12 ` Vladimir Oltean
2020-10-17 20:56 ` Christian Eggers
2020-10-17 21:35 ` Vladimir Oltean
2020-10-17 2:35 ` Florian Fainelli [this message]
2020-10-16 20:02 ` [PATCH net-next 2/3] net: dsa: tag_ksz: don't allocate additional memory for padding/tagging Christian Eggers
2020-10-16 20:02 ` [PATCH net-next 3/3] net: dsa: trailer: " Christian Eggers
2020-10-17 2:44 ` [PATCH 0/3] net: dsa: move skb reallocation to dsa_slave_xmit Florian Fainelli
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