For tap device new skb is created and data from the current skb is
copied to it. This adds copying data from non-linear skb to new
the skb.

Signed-off-by: Arseniy Krasnov <redacted>
---
net/vmw_vsock/virtio_transport_common.c | 31 ++++++++++++++++++++++---
1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 5819a9cd4515..0de562c1dc4b 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c

@@ -106,6 +106,27 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,

	return NULL;
}

+static void virtio_transport_copy_nonlinear_skb(struct sk_buff *skb,

+						void *dst,
+						size_t len)
+{
+	struct iov_iter iov_iter = { 0 };
+	struct kvec kvec;
+	size_t to_copy;
+
+	kvec.iov_base = dst;
+	kvec.iov_len = len;
+
+	iov_iter.iter_type = ITER_KVEC;
+	iov_iter.kvec = &kvec;
+	iov_iter.nr_segs = 1;
+
+	to_copy = min_t(size_t, len, skb->len);
+
+	skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->frag_off,
+			       &iov_iter, to_copy);
+}
+
/* Packet capture */
static struct sk_buff *virtio_transport_build_skb(void *opaque)
{

@@ -114,7 +135,6 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)

	struct af_vsockmon_hdr *hdr;
	struct sk_buff *skb;
	size_t payload_len;
-	void *payload_buf;

	/* A packet could be split to fit the RX buffer, so we can retrieve
	 * the payload length from the header and the buffer pointer taking

@@ -122,7 +142,6 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)

	 */
	pkt_hdr = virtio_vsock_hdr(pkt);
	payload_len = pkt->len;
-	payload_buf = pkt->data;

	skb = alloc_skb(sizeof(*hdr) + sizeof(*pkt_hdr) + payload_len,
			GFP_ATOMIC);

@@ -165,7 +184,13 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)

	skb_put_data(skb, pkt_hdr, sizeof(*pkt_hdr));

	if (payload_len) {
-		skb_put_data(skb, payload_buf, payload_len);
+		if (skb_is_nonlinear(pkt)) {
+			void *data = skb_put(skb, payload_len);
+
+			virtio_transport_copy_nonlinear_skb(pkt, data, 
payload_len);
+		} else {
+			skb_put_data(skb, pkt->data, payload_len);
+		}
	}

	return skb;
-- 
2.25.1