On Mon, Feb 06, 2023 at 06:59:21AM +0000, Arseniy Krasnov wrote:
>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 <AVKrasnov@sberdevices.ru>
>---
> 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);
>+ }
Ehm I'm a bit confused. Maybe we need to rename the sk_buffs involved in
this function (pre-existing).
We have `pkt` that is the original sk_buff, and `skb` that it is
allocated in this function, so IIUC we should check if `pkt` is
nonlinear and copy its payload into `skb`, so we should do this
(untested) chage:
@@ -367,10 +367,10 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
skb_put_data(skb, pkt_hdr, sizeof(*pkt_hdr));
if (payload_len) {
- if (skb_is_nonlinear(skb)) {
+ if (skb_is_nonlinear(pkt)) {
void *data = skb_put(skb, payload_len);
- virtio_transport_copy_nonlinear_skb(skb, data, payload_len);
+ virtio_transport_copy_nonlinear_skb(pkt, data, payload_len);
} else {
skb_put_data(skb, pkt->data, payload_len);
}
Thanks,
Stefano
> }
>
> return skb;
>--
>2.25.1