[PATCH v3 2/5] net: tun: don't assume IFF_VNET_HDR in tun_xdp_one() tx path

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

Sometimes it's just a data packet. The virtio_net_hdr processing should be
conditional on IFF_VNET_HDR, just as it is in tun_get_user().

Fixes: 043d222f93ab ("tuntap: accept an array of XDP buffs through sendmsg()")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 drivers/net/tun.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 67b406fa0881..9acd448e6dfc 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2331,7 +2331,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 {
 	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 = NULL;
 	struct bpf_prog *xdp_prog;
 	struct sk_buff *skb = NULL;
 	u32 rxhash = 0, act;
@@ -2340,9 +2340,12 @@ static int tun_xdp_one(struct tun_struct *tun,
 	bool skb_xdp = false;
 	struct page *page;
 
+	if (tun->flags & IFF_VNET_HDR)
+		gso = &hdr->gso;
+
 	xdp_prog = rcu_dereference(tun->xdp_prog);
 	if (xdp_prog) {
-		if (gso->gso_type) {
+		if (gso && gso->gso_type) {
 			skb_xdp = true;
 			goto build;
 		}
@@ -2388,7 +2391,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 	skb_reserve(skb, xdp->data - xdp->data_hard_start);
 	skb_put(skb, xdp->data_end - xdp->data);
 
-	if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
+	if (gso && virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
 		atomic_long_inc(&tun->rx_frame_errors);
 		kfree_skb(skb);
 		err = -EINVAL;
-- 
2.31.1