From: "Michael S. Tsirkin" <mst@redhat•com>
To: Xuan Zhuo <xuanzhuo@linux•alibaba.com>
Cc: netdev@vger•kernel.org, "Jason Wang" <jasowang@redhat•com>,
"Eugenio Pérez" <eperezma@redhat•com>,
"Andrew Lunn" <andrew+netdev@lunn•ch>,
"David S. Miller" <davem@davemloft•net>,
"Eric Dumazet" <edumazet@google•com>,
"Jakub Kicinski" <kuba@kernel•org>,
"Paolo Abeni" <pabeni@redhat•com>,
"Heng Qi" <hengqi@linux•alibaba.com>,
"Willem de Bruijn" <willemb@google•com>,
"Jiri Pirko" <jiri@resnulli•us>,
"Alvaro Karsz" <alvaro.karsz@solid-run•com>,
virtualization@lists•linux.dev
Subject: Re: [PATCH net v4 2/4] virtio-net: Ensure hdr_len is not set unless the header is forwarded to the device.
Date: Sun, 9 Nov 2025 16:37:50 -0500 [thread overview]
Message-ID: <20251109163644-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20251029030913.20423-3-xuanzhuo@linux.alibaba.com>
On Wed, Oct 29, 2025 at 11:09:11AM +0800, Xuan Zhuo wrote:
> Although `virtio_net_hdr_from_skb` is used in several places outside of
> `virtio-net.c`, the `hdr_len` field is only utilized by the device
> according to the specification. Therefore, we do not need to set
> `hdr_len` unless the header is actually passed to the device.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux•alibaba.com>
maybe ... but what is this patch trying to achieve?
it does not seem harmful to set it ...
> ---
> include/linux/virtio_net.h | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index 4d1780848d0e..710ae0d2d336 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -218,9 +218,14 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
> if (skb_is_gso(skb)) {
> struct skb_shared_info *sinfo = skb_shinfo(skb);
>
> - /* This is a hint as to how much should be linear. */
> - hdr->hdr_len = __cpu_to_virtio16(little_endian,
> - skb_headlen(skb));
> + /* In certain code paths (such as the af_packet.c receive path),
> + * this function may be called without a transport header.
> + * In this case, we do not need to set the hdr_len.
> + */
> + if (skb_transport_header_was_set(skb))
> + hdr->hdr_len = __cpu_to_virtio16(little_endian,
> + skb_headlen(skb));
> +
> hdr->gso_size = __cpu_to_virtio16(little_endian,
> sinfo->gso_size);
> if (sinfo->gso_type & SKB_GSO_TCPV4)
> --
> 2.32.0.3.g01195cf9f
next prev parent reply other threads:[~2025-11-09 21:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-29 3:09 [PATCH net v4 0/4] fixes two virtio-net related bugs Xuan Zhuo
2025-10-29 3:09 ` [PATCH net v4 1/4] virtio-net: fix incorrect flags recording in big mode Xuan Zhuo
2025-11-09 17:04 ` Alyssa Ross
2025-11-09 21:34 ` Michael S. Tsirkin
2025-10-29 3:09 ` [PATCH net v4 2/4] virtio-net: Ensure hdr_len is not set unless the header is forwarded to the device Xuan Zhuo
2025-10-30 2:42 ` Jason Wang
2025-11-09 21:37 ` Michael S. Tsirkin [this message]
2025-10-29 3:09 ` [PATCH net v4 3/4] virtio-net: correct hdr_len handling for VIRTIO_NET_F_GUEST_HDRLEN Xuan Zhuo
2025-10-30 2:53 ` Jason Wang
2025-11-09 21:41 ` Michael S. Tsirkin
2025-11-10 7:16 ` Jason Wang
2025-11-10 7:26 ` Michael S. Tsirkin
2025-11-10 7:39 ` Jason Wang
2025-11-10 16:10 ` Michael S. Tsirkin
2025-11-11 0:45 ` Jason Wang
2025-11-09 21:42 ` Michael S. Tsirkin
2025-10-29 3:09 ` [PATCH net v4 4/4] virtio-net: correct hdr_len handling for tunnel gso Xuan Zhuo
2025-10-29 9:51 ` Paolo Abeni
2025-10-30 8:02 ` [PATCH net v4 0/4] fixes two virtio-net related bugs Michael S. Tsirkin
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