netdev - [PATCH v1 net-next 1/3] net: implement virtio helper to handle outer nw offset

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Message-ID: <20250923202258.2738717-2-kshankar@marvell.com>
Date: Wed, 24 Sep 2025 01:52:56 +0530
From: Kommula Shiva Shankar <kshankar@...vell.com>
To: <netdev@...r.kernel.org>, <mst@...hat.com>, <jasowang@...hat.com>,
        <pabeni@...hat.com>, <xuanzhuo@...ux.alibaba.com>
CC: <virtualization@...ts.linux.dev>, <parav@...dia.com>, <jerinj@...vell.com>,
        <ndabilpuram@...vell.com>, <sburla@...vell.com>, <schalla@...vell.com>
Subject: [PATCH v1 net-next  1/3] net: implement virtio helper to handle outer nw offset

virtio specification introduced support for outer network
header offset broadcast.

This patch implements the needed defines and virtio header
parsing capabilities.

Signed-off-by: Kommula Shiva Shankar <kshankar@...vell.com>
---
 include/linux/virtio_net.h      | 40 +++++++++++++++++++++++++++++++++
 include/uapi/linux/virtio_net.h |  8 +++++++
 2 files changed, 48 insertions(+)

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 20e0584db1dd..e6153e9106d3 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -374,6 +374,46 @@ static inline int virtio_net_handle_csum_offload(struct sk_buff *skb,
 	return 0;
 }
 
+static inline int
+virtio_net_out_net_header_to_skb(struct sk_buff *skb,
+				 struct virtio_net_hdr_v1_hash_tunnel_out_net_hdr *vhdr,
+				 bool out_net_hdr_negotiated,
+				 bool little_endian)
+{
+	unsigned int out_net_hdr_off;
+
+	if (!out_net_hdr_negotiated)
+		return 0;
+
+	if (vhdr->outer_nh_offset) {
+		out_net_hdr_off = __virtio16_to_cpu(little_endian, vhdr->outer_nh_offset);
+		skb_set_network_header(skb, out_net_hdr_off);
+	}
+
+	return 0;
+}
+
+static inline int
+virtio_net_out_net_header_from_skb(const struct sk_buff *skb,
+				   struct virtio_net_hdr_v1_hash_tunnel_out_net_hdr *vhdr,
+				   bool out_net_hdr_negotiated,
+				   bool little_endian)
+{
+	unsigned int out_net_hdr_off;
+
+	if (!out_net_hdr_negotiated) {
+		vhdr->outer_nh_offset = 0;
+		return 0;
+	}
+
+	out_net_hdr_off = skb_network_offset(skb);
+	if (out_net_hdr_off && skb->protocol == htons(ETH_P_IP))
+		vhdr->outer_nh_offset = __cpu_to_virtio16(little_endian,
+							  out_net_hdr_off);
+
+	return 0;
+}
+
 /*
  * vlan_hlen always refers to the outermost MAC header. That also
  * means it refers to the only MAC header, if the packet does not carry
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index 8bf27ab8bcb4..6032b9e443bb 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -86,6 +86,7 @@
 						  * packets with partial csum
 						  * for the outer header
 						  */
+#define VIRTIO_NET_F_OUT_NET_HEADER 69	/* Outer network header offset */
 
 /* Offloads bits corresponding to VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO{,_CSUM}
  * features
@@ -214,6 +215,13 @@ struct virtio_net_hdr_v1_hash_tunnel {
 	__le16 inner_nh_offset;
 };
 
+/* outer network header */
+struct virtio_net_hdr_v1_hash_tunnel_out_net_hdr {
+	struct virtio_net_hdr_v1_hash_tunnel tnl_hdr;
+	__le16 outer_nh_offset;
+	__u8 padding_reserved_2[6];
+};
+
 #ifndef VIRTIO_NET_NO_LEGACY
 /* This header comes first in the scatter-gather list.
  * For legacy virtio, if VIRTIO_F_ANY_LAYOUT is not negotiated, it must
-- 
2.48.1