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SubjectRe: [RFC PATCH v4 04/17] vsock/virtio: non-linear skb handling for tap
On Sat, Jun 03, 2023 at 11:49:26PM +0300, 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 | 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,

`const struct sk_buff *skb` should be better also to understand that
the function copy data from *skb to *dst.

>+ 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
>

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