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 | 43 +++++++++++++++++++++++--
1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index a1581c77cf84..05ce97b967ad 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c

@@ -101,6 +101,39 @@ 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)
+{
+	size_t rest_len = len;
+
+	while (rest_len && virtio_vsock_skb_has_frags(skb)) {
+		struct bio_vec *curr_vec;
+		size_t curr_vec_end;
+		size_t to_copy;
+		int curr_frag;
+		int curr_offs;
+
+		curr_frag = VIRTIO_VSOCK_SKB_CB(skb)->curr_frag;
+		curr_offs = VIRTIO_VSOCK_SKB_CB(skb)->frag_off;
+		curr_vec = &skb_shinfo(skb)->frags[curr_frag];
+
+		curr_vec_end = curr_vec->bv_offset + curr_vec->bv_len;
+		to_copy = min(rest_len, (size_t)(curr_vec_end - curr_offs));
+
+		memcpy(dst, page_to_virt(curr_vec->bv_page) + curr_offs,
+		       to_copy);
+
+		rest_len -= to_copy;
+		VIRTIO_VSOCK_SKB_CB(skb)->frag_off += to_copy;
+
+		if (VIRTIO_VSOCK_SKB_CB(skb)->frag_off == (curr_vec_end)) {
+			VIRTIO_VSOCK_SKB_CB(skb)->curr_frag++;
+			VIRTIO_VSOCK_SKB_CB(skb)->frag_off = 0;
+		}
+	}
+}
+
/* Packet capture */
static struct sk_buff *virtio_transport_build_skb(void *opaque)
{

@@ -109,7 +142,6 @@ 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

@@ -117,7 +149,6 @@ 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);

@@ -160,7 +191,13 @@ 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(skb)) {
+			void *data = skb_put(skb, payload_len);
+
+			virtio_transport_copy_nonlinear_skb(skb, data, payload_len);
+		} else {
+			skb_put_data(skb, pkt->data, payload_len);
+		}