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[80.230.39.63]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477afb54774sm26915625e9.3.2025.11.19.07.27.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Nov 2025 07:27:49 -0800 (PST) Date: Wed, 19 Nov 2025 10:27:46 -0500 From: "Michael S. Tsirkin" To: Xuan Zhuo Cc: netdev@vger.kernel.org, Willem de Bruijn , Jason Wang , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Eugenio =?iso-8859-1?Q?P=E9rez?= , Jiri Pirko , Alvaro Karsz , virtualization@lists.linux.dev Subject: Re: [PATCH net v6 1/2] virtio-net: correct hdr_len handling for VIRTIO_NET_F_GUEST_HDRLEN Message-ID: <20251119102708-mutt-send-email-mst@kernel.org> References: <20251119055522.617-1-xuanzhuo@linux.alibaba.com> <20251119055522.617-2-xuanzhuo@linux.alibaba.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251119055522.617-2-xuanzhuo@linux.alibaba.com> On Wed, Nov 19, 2025 at 01:55:21PM +0800, Xuan Zhuo wrote: > 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 > --- > drivers/net/tun_vnet.h | 2 +- > drivers/net/virtio_net.c | 8 ++++-- > include/linux/virtio_net.h | 58 ++++++++++++++++++++++++++++++-------- > 3 files changed, 54 insertions(+), 14 deletions(-) > > diff --git a/drivers/net/tun_vnet.h b/drivers/net/tun_vnet.h > index 81662328b2c7..b06aa6f2aade 100644 > --- a/drivers/net/tun_vnet.h > +++ b/drivers/net/tun_vnet.h > @@ -244,7 +244,7 @@ tun_vnet_hdr_tnl_from_skb(unsigned int flags, > > if (virtio_net_hdr_tnl_from_skb(skb, tnl_hdr, has_tnl_offload, > tun_vnet_is_little_endian(flags), > - vlan_hlen)) { > + false, vlan_hlen)) { > struct virtio_net_hdr_v1 *hdr = &tnl_hdr->hash_hdr.hdr; > struct skb_shared_info *sinfo = skb_shinfo(skb); > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 0369dda5ed60..a62acfaf631b 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -3317,9 +3317,12 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb, bool orphan) > const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest; > struct virtnet_info *vi = sq->vq->vdev->priv; > struct virtio_net_hdr_v1_hash_tunnel *hdr; > - int num_sg; > unsigned hdr_len = vi->hdr_len; > + bool guest_hdrlen; > bool can_push; > + int num_sg; > + > + guest_hdrlen = virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_HDRLEN); > > pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest); > > @@ -3339,7 +3342,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb, bool orphan) > hdr = &skb_vnet_common_hdr(skb)->tnl_hdr; > > if (virtio_net_hdr_tnl_from_skb(skb, hdr, vi->tx_tnl, > - virtio_is_little_endian(vi->vdev), 0)) > + virtio_is_little_endian(vi->vdev), > + guest_hdrlen, 0)) > return -EPROTO; > > if (vi->mergeable_rx_bufs) > diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h > index b673c31569f3..ee960ec9a35e 100644 > --- a/include/linux/virtio_net.h > +++ b/include/linux/virtio_net.h > @@ -207,20 +207,40 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, > return __virtio_net_hdr_to_skb(skb, hdr, little_endian, hdr->gso_type); > } > > -static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb, > - struct virtio_net_hdr *hdr, > - bool little_endian, > - bool has_data_valid, > - int vlan_hlen) > +static inline void virtio_net_set_hdrlen(const struct sk_buff *skb, > + struct virtio_net_hdr *hdr, > + bool little_endian, > + bool guest_hdrlen) > +{ > + u16 hdr_len; > + > + if (guest_hdrlen) { > + hdr_len = skb_transport_offset(skb); > + > + if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4) > + hdr_len += sizeof(struct udphdr); > + else > + hdr_len += tcp_hdrlen(skb); > + } else { > + /* This is a hint as to how much should be linear. */ > + hdr_len = skb_headlen(skb); > + } > + > + hdr->hdr_len = __cpu_to_virtio16(little_endian, hdr_len); > +} So this adds code that is broken for tunnels, then the follow up patch fixes it up. I don't feel it's worth it, just squash the two patches together please. > + > +static inline int __virtio_net_hdr_from_skb(const struct sk_buff *skb, > + struct virtio_net_hdr *hdr, > + bool little_endian, > + bool has_data_valid, > + bool guest_hdrlen, > + int vlan_hlen) > { > memset(hdr, 0, sizeof(*hdr)); /* no info leak */ > > 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)); > hdr->gso_size = __cpu_to_virtio16(little_endian, > sinfo->gso_size); > if (sinfo->gso_type & SKB_GSO_TCPV4) > @@ -231,6 +251,10 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb, > hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP_L4; > else > return -EINVAL; > + > + virtio_net_set_hdrlen(skb, hdr, little_endian, > + guest_hdrlen); > + > if (sinfo->gso_type & SKB_GSO_TCP_ECN) > hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN; > } else > @@ -250,6 +274,16 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb, > return 0; > } > > +static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb, > + struct virtio_net_hdr *hdr, > + bool little_endian, > + bool has_data_valid, > + int vlan_hlen) > +{ > + return __virtio_net_hdr_from_skb(skb, hdr, little_endian, > + has_data_valid, false, vlan_hlen); > +} > + > static inline unsigned int virtio_l3min(bool is_ipv6) > { > return is_ipv6 ? sizeof(struct ipv6hdr) : sizeof(struct iphdr); > @@ -384,6 +418,7 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb, > struct virtio_net_hdr_v1_hash_tunnel *vhdr, > bool tnl_hdr_negotiated, > bool little_endian, > + bool guest_hdrlen, > int vlan_hlen) > { > struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)vhdr; > @@ -394,8 +429,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb, > tnl_gso_type = skb_shinfo(skb)->gso_type & (SKB_GSO_UDP_TUNNEL | > SKB_GSO_UDP_TUNNEL_CSUM); > if (!tnl_gso_type) > - return virtio_net_hdr_from_skb(skb, hdr, little_endian, false, > - vlan_hlen); > + return __virtio_net_hdr_from_skb(skb, hdr, little_endian, false, > + guest_hdrlen, vlan_hlen); > > /* Tunnel support not negotiated but skb ask for it. */ > if (!tnl_hdr_negotiated) > @@ -408,7 +443,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb, > > /* Let the basic parsing deal with plain GSO features. */ > skb_shinfo(skb)->gso_type &= ~tnl_gso_type; > - ret = virtio_net_hdr_from_skb(skb, hdr, true, false, vlan_hlen); > + ret = __virtio_net_hdr_from_skb(skb, hdr, true, false, > + guest_hdrlen, vlan_hlen); > skb_shinfo(skb)->gso_type |= tnl_gso_type; > if (ret) > return ret; > -- > 2.32.0.3.g01195cf9f