[PATCH net v6 0/2] virtio-net: fix for VIRTIO_NET_F_GUEST_HDRLEN

[PATCH net v6 0/2] virtio-net: fix for VIRTIO_NET_F_GUEST_HDRLEN

[Xuan Zhuo]

v6:
  1. rename to guest_hdrlen
  2. introduce a function virtio_net_set_hdrlen to set the hdrlen

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 path set fixes that issue.

As discussed in [0], this version checks the VIRTIO_NET_F_GUEST_HDRLEN is
negotiated.


[0]: http://lore.kernel.org/all/20251029030913.20423-1-xuanzhuo@linux.alibaba.com


Xuan Zhuo (2):
  virtio-net: correct hdr_len handling for VIRTIO_NET_F_GUEST_HDRLEN
  virtio-net: correct hdr_len handling for tunnel gso

 drivers/net/tun_vnet.h     |  2 +-
 drivers/net/virtio_net.c   |  8 +++--
 include/linux/virtio_net.h | 71 ++++++++++++++++++++++++++++++--------
 3 files changed, 64 insertions(+), 17 deletions(-)

--
2.32.0.3.g01195cf9f

[PATCH net v6 1/2] virtio-net: correct hdr_len handling for VIRTIO_NET_F_GUEST_HDRLEN

[Xuan Zhuo]

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>
---
 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);
+}
+
+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

Re: [PATCH net v6 1/2] virtio-net: correct hdr_len handling for VIRTIO_NET_F_GUEST_HDRLEN

[Michael S. Tsirkin]

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 <xuanzhuo@linux.alibaba.com>
> ---
>  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

[PATCH net v6 2/2] virtio-net: correct hdr_len handling for tunnel gso

[Xuan Zhuo]

The commit a2fb4bc4e2a6a03 ("net: implement virtio helpers to handle UDP
GSO tunneling.") introduces support for the UDP GSO tunnel feature in
virtio-net.

The virtio spec says:

    If the \field{gso_type} has the VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV4 bit or
    VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV6 bit set, \field{hdr_len} accounts for
    all the headers up to and including the inner transport.

The commit did not update the hdr_len to include the inner transport.

I observed that the "hdr_len" is 116 for this packet:

    17:36:18.241105 52:55:00:d1:27:0a > 2e:2c:df:46:a9:e1, ethertype IPv4 (0x0800), length 2912: (tos 0x0, ttl 64, id 45197, offset 0, flags [none], proto UDP (17), length 2898)
        192.168.122.100.50613 > 192.168.122.1.4789: [bad udp cksum 0x8106 -> 0x26a0!] VXLAN, flags [I] (0x08), vni 1
    fa:c3:ba:82:05:ee > ce:85:0c:31:77:e5, ethertype IPv4 (0x0800), length 2862: (tos 0x0, ttl 64, id 14678, offset 0, flags [DF], proto TCP (6), length 2848)
        192.168.3.1.49880 > 192.168.3.2.9898: Flags [P.], cksum 0x9266 (incorrect -> 0xaa20), seq 515667:518463, ack 1, win 64, options [nop,nop,TS val 2990048824 ecr 2798801412], length 2796

116 = 14(mac) + 20(ip) + 8(udp) + 8(vxlan) + 14(inner mac) + 20(inner ip) + 32(innner tcp)

Fixes: a2fb4bc4e2a6a03 ("net: implement virtio helpers to handle UDP GSO tunneling.")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 include/linux/virtio_net.h | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index ee960ec9a35e..ee8231eb759b 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -215,12 +215,22 @@ static inline void virtio_net_set_hdrlen(const struct sk_buff *skb,
 	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);
+		if (sinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
+				       SKB_GSO_UDP_TUNNEL_CSUM)) {
+			hdr_len = skb_inner_transport_offset(skb);
+
+			if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4)
+				hdr_len += sizeof(struct udphdr);
+			else
+				hdr_len += inner_tcp_hdrlen(skb);
+		} else {
+			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);
@@ -441,11 +451,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb,
         vhdr->hash_hdr.hash_report = 0;
         vhdr->hash_hdr.padding = 0;
 
-	/* 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,
 					guest_hdrlen, vlan_hlen);
-	skb_shinfo(skb)->gso_type |= tnl_gso_type;
 	if (ret)
 		return ret;
 
-- 
2.32.0.3.g01195cf9f

Re: [PATCH net v6 2/2] virtio-net: correct hdr_len handling for tunnel gso

[Michael S. Tsirkin]

On Wed, Nov 19, 2025 at 01:55:22PM +0800, Xuan Zhuo wrote:
> The commit a2fb4bc4e2a6a03 ("net: implement virtio helpers to handle UDP
> GSO tunneling.") introduces support for the UDP GSO tunnel feature in
> virtio-net.
> 
> The virtio spec says:
> 
>     If the \field{gso_type} has the VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV4 bit or
>     VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV6 bit set, \field{hdr_len} accounts for
>     all the headers up to and including the inner transport.
> 
> The commit did not update the hdr_len to include the inner transport.
> 
> I observed that the "hdr_len" is 116 for this packet:
>     17:36:18.241105 52:55:00:d1:27:0a > 2e:2c:df:46:a9:e1, ethertype IPv4 (0x0800), length 2912: (tos 0x0, ttl 64, id 45197, offset 0, flags [none], proto UDP (17), length 2898)
>         192.168.122.100.50613 > 192.168.122.1.4789: [bad udp cksum 0x8106 -> 0x26a0!] VXLAN, flags [I] (0x08), vni 1
>     fa:c3:ba:82:05:ee > ce:85:0c:31:77:e5, ethertype IPv4 (0x0800), length 2862: (tos 0x0, ttl 64, id 14678, offset 0, flags [DF], proto TCP (6), length 2848)
>         192.168.3.1.49880 > 192.168.3.2.9898: Flags [P.], cksum 0x9266 (incorrect -> 0xaa20), seq 515667:518463, ack 1, win 64, options [nop,nop,TS val 2990048824 ecr 2798801412], length 2796
> 
> 116 = 14(mac) + 20(ip) + 8(udp) + 8(vxlan) + 14(inner mac) + 20(inner ip) + 32(innner tcp)
> 
> Fixes: a2fb4bc4e2a6a03 ("net: implement virtio helpers to handle UDP GSO tunneling.")
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>  include/linux/virtio_net.h | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index ee960ec9a35e..ee8231eb759b 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -215,12 +215,22 @@ static inline void virtio_net_set_hdrlen(const struct sk_buff *skb,
>  	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);
> +		if (sinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
> +				       SKB_GSO_UDP_TUNNEL_CSUM)) {
> +			hdr_len = skb_inner_transport_offset(skb);
> +
> +			if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4)
> +				hdr_len += sizeof(struct udphdr);
> +			else
> +				hdr_len += inner_tcp_hdrlen(skb);
> +		} else {
> +			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);

BTW  I noticed that include/linux/virtio_net.h really should include
linux/tcp.h for tcp_hdrlen and uapi/linux/udp.h for struct udphdr


Not a new issue so you do not have to resolve it in this patchset,
though.



> @@ -441,11 +451,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb,
>          vhdr->hash_hdr.hash_report = 0;
>          vhdr->hash_hdr.padding = 0;
>  
> -	/* 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,
>  					guest_hdrlen, vlan_hlen);
> -	skb_shinfo(skb)->gso_type |= tnl_gso_type;
>  	if (ret)
>  		return ret;
>  
> -- 
> 2.32.0.3.g01195cf9f

Re: [PATCH net v6 2/2] virtio-net: correct hdr_len handling for tunnel gso

[kernel test robot]

Hi Xuan,

kernel test robot noticed the following build errors:

[auto build test ERROR on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Xuan-Zhuo/virtio-net-correct-hdr_len-handling-for-VIRTIO_NET_F_GUEST_HDRLEN/20251119-135650
base:   net/main
patch link:    https://lore.kernel.org/r/20251119055522.617-3-xuanzhuo%40linux.alibaba.com
patch subject: [PATCH net v6 2/2] virtio-net: correct hdr_len handling for tunnel gso
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20251120/202511200846.lqEgKwk3-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251120/202511200846.lqEgKwk3-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511200846.lqEgKwk3-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/net/tun.c:59:
>> include/linux/virtio_net.h:218:7: error: use of undeclared identifier 'sinfo'
     218 |                 if (sinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
         |                     ^
   1 error generated.


vim +/sinfo +218 include/linux/virtio_net.h

   209	
   210	static inline void virtio_net_set_hdrlen(const struct sk_buff *skb,
   211						 struct virtio_net_hdr *hdr,
   212						 bool little_endian,
   213						 bool guest_hdrlen)
   214	{
   215		u16 hdr_len;
   216	
   217		if (guest_hdrlen) {
 > 218			if (sinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
   219					       SKB_GSO_UDP_TUNNEL_CSUM)) {
   220				hdr_len = skb_inner_transport_offset(skb);
   221	
   222				if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4)
   223					hdr_len += sizeof(struct udphdr);
   224				else
   225					hdr_len += inner_tcp_hdrlen(skb);
   226			} else {
   227				hdr_len = skb_transport_offset(skb);
   228	
   229				if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4)
   230					hdr_len += sizeof(struct udphdr);
   231				else
   232					hdr_len += tcp_hdrlen(skb);
   233			}
   234		} else {
   235			/* This is a hint as to how much should be linear. */
   236			hdr_len = skb_headlen(skb);
   237		}
   238	
   239		hdr->hdr_len = __cpu_to_virtio16(little_endian, hdr_len);
   240	}
   241	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH net v6 2/2] virtio-net: correct hdr_len handling for tunnel gso

[kernel test robot]

Hi Xuan,

kernel test robot noticed the following build errors:

[auto build test ERROR on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Xuan-Zhuo/virtio-net-correct-hdr_len-handling-for-VIRTIO_NET_F_GUEST_HDRLEN/20251119-135650
base:   net/main
patch link:    https://lore.kernel.org/r/20251119055522.617-3-xuanzhuo%40linux.alibaba.com
patch subject: [PATCH net v6 2/2] virtio-net: correct hdr_len handling for tunnel gso
config: arm-jornada720_defconfig (https://download.01.org/0day-ci/archive/20251120/202511200817.29vdvG8S-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 0bba1e76581bad04e7d7f09f5115ae5e2989e0d9)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251120/202511200817.29vdvG8S-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511200817.29vdvG8S-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from net/packet/af_packet.c:86:
>> include/linux/virtio_net.h:218:7: error: use of undeclared identifier 'sinfo'
     218 |                 if (sinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
         |                     ^~~~~
   1 error generated.


vim +/sinfo +218 include/linux/virtio_net.h

   209	
   210	static inline void virtio_net_set_hdrlen(const struct sk_buff *skb,
   211						 struct virtio_net_hdr *hdr,
   212						 bool little_endian,
   213						 bool guest_hdrlen)
   214	{
   215		u16 hdr_len;
   216	
   217		if (guest_hdrlen) {
 > 218			if (sinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
   219					       SKB_GSO_UDP_TUNNEL_CSUM)) {
   220				hdr_len = skb_inner_transport_offset(skb);
   221	
   222				if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4)
   223					hdr_len += sizeof(struct udphdr);
   224				else
   225					hdr_len += inner_tcp_hdrlen(skb);
   226			} else {
   227				hdr_len = skb_transport_offset(skb);
   228	
   229				if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4)
   230					hdr_len += sizeof(struct udphdr);
   231				else
   232					hdr_len += tcp_hdrlen(skb);
   233			}
   234		} else {
   235			/* This is a hint as to how much should be linear. */
   236			hdr_len = skb_headlen(skb);
   237		}
   238	
   239		hdr->hdr_len = __cpu_to_virtio16(little_endian, hdr_len);
   240	}
   241	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki