tun: remove unnecessary tun_xdp_hdr structure

With f95f0f95cfb7("net, xdp: Introduce xdp_init_buff utility routine"),
buffer length could be stored as frame size so there's no need to have
a dedicated tun_xdp_hdr structure. We can simply store virtio net
header instead.

Acked-by: Willem de Bruijn <[e-mail]>
Signed-off-by: Jason Wang <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/tap.c

···
 
 static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
 {
-	struct tun_xdp_hdr *hdr = xdp->data_hard_start;
-	struct virtio_net_hdr *gso = &hdr->gso;
-	int buflen = hdr->buflen;
+	struct virtio_net_hdr *gso = xdp->data_hard_start;
+	int buflen = xdp->frame_sz;
 	int vnet_hdr_len = 0;
 	struct tap_dev *tap;
 	struct sk_buff *skb;

drivers/net/tun.c

···
 		       struct tun_page *tpage)
 {
 	unsigned int datasize = xdp->data_end - xdp->data;
-	struct tun_xdp_hdr *hdr = xdp->data_hard_start;
-	struct virtio_net_hdr *gso = &hdr->gso;
+	struct virtio_net_hdr *gso = xdp->data_hard_start;
 	struct bpf_prog *xdp_prog;
 	struct sk_buff *skb = NULL;
 	struct sk_buff_head *queue;
 	u32 rxhash = 0, act;
-	int buflen = hdr->buflen;
+	int buflen = xdp->frame_sz;
 	int metasize = 0;
 	int ret = 0;
 	bool skb_xdp = false;

drivers/vhost/net.c

···
 	struct socket *sock = vhost_vq_get_backend(vq);
 	struct virtio_net_hdr *gso;
 	struct xdp_buff *xdp = &nvq->xdp[nvq->batched_xdp];
-	struct tun_xdp_hdr *hdr;
 	size_t len = iov_iter_count(from);
 	int headroom = vhost_sock_xdp(sock) ? XDP_PACKET_HEADROOM : 0;
 	int buflen = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
···
 	if (unlikely(!buf))
 		return -ENOMEM;
 
-	copied = copy_from_iter(buf + offsetof(struct tun_xdp_hdr, gso),
-				sock_hlen, from);
+	copied = copy_from_iter(buf, sock_hlen, from);
 	if (copied != sock_hlen) {
 		ret = -EFAULT;
 		goto err;
 	}
 
-	hdr = buf;
-	gso = &hdr->gso;
+	gso = buf;
 
 	if (!sock_hlen)
 		memset(buf, 0, pad);
···
 
 	xdp_init_buff(xdp, buflen, NULL);
 	xdp_prepare_buff(xdp, buf, pad, len, true);
-	hdr->buflen = buflen;
 
 	++nvq->batched_xdp;
 

include/linux/if_tun.h

···
 	void *ptr;
 };
 
-struct tun_xdp_hdr {
-	int buflen;
-	struct virtio_net_hdr gso;
-};
-
 #if defined(CONFIG_TUN) || defined(CONFIG_TUN_MODULE)
 struct socket *tun_get_socket(struct file *);
 struct ptr_ring *tun_get_tx_ring(struct file *file);