[PATCH net 2/2] virtio-net: correct hdr_len handling for VIRTIO_NET_F_GUEST_HDRLEN
From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: 2025-09-25 02:25:47
Also in:
virtualization
Subsystem:
the rest, virtio core, virtio net driver · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang
The commit be50da3e9d4a ("net: virtio_net: implement exact header length
guest feature") introduces support for the VIRTIO_NET_F_GUEST_HDRLEN
feature in virtio-net.
This feature requires virtio-net to set hdr_len to the actual header
length of the packet when transmitting, the number of
bytes from the start of the packet to the beginning of the
transport-layer payload.
However, in practice, hdr_len was being set using skb_headlen(skb),
which is clearly incorrect. This commit fixes that issue.
Fixes: be50da3e9d4a ("net: virtio_net: implement exact header length guest feature")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
include/linux/virtio_net.h | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 20e0584db1dd..4273420a9ff9 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h@@ -217,20 +217,25 @@ 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); + u16 hdr_len; - /* This is a hint as to how much should be linear. */ - hdr->hdr_len = __cpu_to_virtio16(little_endian, - skb_headlen(skb)); + hdr_len = skb_transport_offset(skb); hdr->gso_size = __cpu_to_virtio16(little_endian, sinfo->gso_size); - if (sinfo->gso_type & SKB_GSO_TCPV4) + if (sinfo->gso_type & SKB_GSO_TCPV4) { hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4; - else if (sinfo->gso_type & SKB_GSO_TCPV6) + hdr_len += tcp_hdrlen(skb); + } else if (sinfo->gso_type & SKB_GSO_TCPV6) { hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6; - else if (sinfo->gso_type & SKB_GSO_UDP_L4) + hdr_len += tcp_hdrlen(skb); + } else if (sinfo->gso_type & SKB_GSO_UDP_L4) { hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP_L4; - else + hdr_len += sizeof(struct udphdr); + } else { return -EINVAL; + } + + hdr->hdr_len = __cpu_to_virtio16(little_endian, hdr_len); if (sinfo->gso_type & SKB_GSO_TCP_ECN) hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN; } else
--
2.32.0.3.g01195cf9f