From: Anton Ivanov <[email protected]>

Some of the locally generated frames marked as GSO which
arrive at virtio_net_hdr_from_skb() have no GSO_TYPE, no
fragments (data_len = 0) and length significantly shorter
than the MTU (752 in my experiments).

This is observed on raw sockets reading off vEth interfaces
in all 4.x and 5.x kernels I tested.

These frames are reported as invalid while they are in fact
gso-less frames.

This patch marks the vnet header as no-GSO for them instead
of reporting it as invalid.

Signed-off-by: Anton Ivanov <[email protected]>
---
 include/linux/virtio_net.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 0d1fe9297ac6..94fb78c3a2ab 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -100,8 +100,8 @@ static inline int virtio_net_hdr_from_skb(const struct 
sk_buff *skb,
 {
        memset(hdr, 0, sizeof(*hdr));   /* no info leak */
 
-       if (skb_is_gso(skb)) {
-               struct skb_shared_info *sinfo = skb_shinfo(skb);
+       struct skb_shared_info *sinfo = skb_shinfo(skb);
+       if (skb_is_gso(skb) && sinfo->gso_type) {
 
                /* This is a hint as to how much should be linear. */
                hdr->hdr_len = __cpu_to_virtio16(little_endian,
-- 
2.20.1

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