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    Subject[RFC PATCH v6 12/22] virtio/vsock: fetch length for SEQPACKET record
    Date
    This adds transport callback which tries to fetch record begin marker
    from socket's rx queue. It is called from af_vsock.c before reading data
    packets of record.

    Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
    ---
    include/linux/virtio_vsock.h | 1 +
    net/vmw_vsock/virtio_transport_common.c | 53 +++++++++++++++++++++++++
    2 files changed, 54 insertions(+)

    diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
    index 466a5832d2f5..d7edcfeb4cd2 100644
    --- a/include/linux/virtio_vsock.h
    +++ b/include/linux/virtio_vsock.h
    @@ -88,6 +88,7 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
    struct msghdr *msg,
    size_t len, int flags);

    +size_t virtio_transport_seqpacket_seq_get_len(struct vsock_sock *vsk);
    int
    virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
    struct msghdr *msg,
    diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
    index 5f1e283e43f3..6fc78fec41c0 100644
    --- a/net/vmw_vsock/virtio_transport_common.c
    +++ b/net/vmw_vsock/virtio_transport_common.c
    @@ -399,6 +399,59 @@ static inline void virtio_transport_remove_pkt(struct virtio_vsock_pkt *pkt)
    virtio_transport_free_pkt(pkt);
    }

    +static size_t virtio_transport_drop_until_seq_begin(struct virtio_vsock_sock *vvs)
    +{
    + struct virtio_vsock_pkt *pkt, *n;
    + size_t bytes_dropped = 0;
    +
    + list_for_each_entry_safe(pkt, n, &vvs->rx_queue, list) {
    + if (le16_to_cpu(pkt->hdr.op) == VIRTIO_VSOCK_OP_SEQ_BEGIN)
    + break;
    +
    + bytes_dropped += le32_to_cpu(pkt->hdr.len);
    + virtio_transport_dec_rx_pkt(vvs, pkt);
    + virtio_transport_remove_pkt(pkt);
    + }
    +
    + return bytes_dropped;
    +}
    +
    +size_t virtio_transport_seqpacket_seq_get_len(struct vsock_sock *vsk)
    +{
    + struct virtio_vsock_seq_hdr *seq_hdr;
    + struct virtio_vsock_sock *vvs;
    + struct virtio_vsock_pkt *pkt;
    + size_t bytes_dropped;
    +
    + vvs = vsk->trans;
    +
    + spin_lock_bh(&vvs->rx_lock);
    +
    + /* Fetch all orphaned 'RW' packets and send credit update. */
    + bytes_dropped = virtio_transport_drop_until_seq_begin(vvs);
    +
    + if (list_empty(&vvs->rx_queue))
    + goto out;
    +
    + pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list);
    +
    + vvs->seqpacket_state.user_read_copied = 0;
    +
    + seq_hdr = (struct virtio_vsock_seq_hdr *)pkt->buf;
    + vvs->seqpacket_state.user_read_seq_len = le32_to_cpu(seq_hdr->msg_len);
    + vvs->seqpacket_state.curr_rx_msg_id = le32_to_cpu(seq_hdr->msg_id);
    + virtio_transport_dec_rx_pkt(vvs, pkt);
    + virtio_transport_remove_pkt(pkt);
    +out:
    + spin_unlock_bh(&vvs->rx_lock);
    +
    + if (bytes_dropped)
    + virtio_transport_send_credit_update(vsk);
    +
    + return vvs->seqpacket_state.user_read_seq_len;
    +}
    +EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_seq_get_len);
    +
    static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
    struct msghdr *msg,
    bool *msg_ready)
    --
    2.25.1
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