// SPDX-License-Identifier: GPL-2.0-only
/* loopback transport for vsock using virtio_transport_common APIs
 *
 * Copyright (C) 2013-2019 Red Hat, Inc.
 * Authors: Asias He <asias@redhat.com>
 *          Stefan Hajnoczi <stefanha@redhat.com>
 *          Stefano Garzarella <sgarzare@redhat.com>
 *
 */
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/virtio_vsock.h>

struct vsock_loopback {
        struct workqueue_struct *workqueue;

        struct sk_buff_head pkt_queue;
        struct work_struct pkt_work;
};

static struct vsock_loopback the_vsock_loopback;

static u32 vsock_loopback_get_local_cid(void)
{
        return VMADDR_CID_LOCAL;
}

static int vsock_loopback_send_pkt(struct sk_buff *skb, struct net *net)
{
        struct vsock_loopback *vsock = &the_vsock_loopback;
        int len = skb->len;

        virtio_vsock_skb_queue_tail(&vsock->pkt_queue, skb);
        queue_work(vsock->workqueue, &vsock->pkt_work);

        return len;
}

static int vsock_loopback_cancel_pkt(struct vsock_sock *vsk)
{
        struct vsock_loopback *vsock = &the_vsock_loopback;

        virtio_transport_purge_skbs(vsk, &vsock->pkt_queue);

        return 0;
}

static bool vsock_loopback_seqpacket_allow(struct vsock_sock *vsk,
                                           u32 remote_cid);

static bool vsock_loopback_stream_allow(struct vsock_sock *vsk, u32 cid,
                                        u32 port)
{
        return true;
}

static bool vsock_loopback_msgzerocopy_allow(void)
{
        return true;
}

static struct virtio_transport loopback_transport = {
        .transport = {
                .module                   = THIS_MODULE,

                .get_local_cid            = vsock_loopback_get_local_cid,

                .init                     = virtio_transport_do_socket_init,
                .destruct                 = virtio_transport_destruct,
                .release                  = virtio_transport_release,
                .connect                  = virtio_transport_connect,
                .shutdown                 = virtio_transport_shutdown,
                .cancel_pkt               = vsock_loopback_cancel_pkt,

                .dgram_bind               = virtio_transport_dgram_bind,
                .dgram_dequeue            = virtio_transport_dgram_dequeue,
                .dgram_enqueue            = virtio_transport_dgram_enqueue,
                .dgram_allow              = virtio_transport_dgram_allow,

                .stream_dequeue           = virtio_transport_stream_dequeue,
                .stream_enqueue           = virtio_transport_stream_enqueue,
                .stream_has_data          = virtio_transport_stream_has_data,
                .stream_has_space         = virtio_transport_stream_has_space,
                .stream_rcvhiwat          = virtio_transport_stream_rcvhiwat,
                .stream_is_active         = virtio_transport_stream_is_active,
                .stream_allow             = vsock_loopback_stream_allow,

                .seqpacket_dequeue        = virtio_transport_seqpacket_dequeue,
                .seqpacket_enqueue        = virtio_transport_seqpacket_enqueue,
                .seqpacket_allow          = vsock_loopback_seqpacket_allow,
                .seqpacket_has_data       = virtio_transport_seqpacket_has_data,

                .msgzerocopy_allow        = vsock_loopback_msgzerocopy_allow,

                .notify_poll_in           = virtio_transport_notify_poll_in,
                .notify_poll_out          = virtio_transport_notify_poll_out,
                .notify_recv_init         = virtio_transport_notify_recv_init,
                .notify_recv_pre_block    = virtio_transport_notify_recv_pre_block,
                .notify_recv_pre_dequeue  = virtio_transport_notify_recv_pre_dequeue,
                .notify_recv_post_dequeue = virtio_transport_notify_recv_post_dequeue,
                .notify_send_init         = virtio_transport_notify_send_init,
                .notify_send_pre_block    = virtio_transport_notify_send_pre_block,
                .notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
                .notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
                .notify_buffer_size       = virtio_transport_notify_buffer_size,
                .notify_set_rcvlowat      = virtio_transport_notify_set_rcvlowat,

                .unsent_bytes             = virtio_transport_unsent_bytes,

                .read_skb = virtio_transport_read_skb,
        },

        .send_pkt = vsock_loopback_send_pkt,
};

static bool
vsock_loopback_seqpacket_allow(struct vsock_sock *vsk, u32 remote_cid)
{
        return vsock_net_mode_global(vsk);
}

static void vsock_loopback_work(struct work_struct *work)
{
        struct vsock_loopback *vsock =
                container_of(work, struct vsock_loopback, pkt_work);
        struct sk_buff_head pkts;
        struct sk_buff *skb;

        skb_queue_head_init(&pkts);

        spin_lock_bh(&vsock->pkt_queue.lock);
        skb_queue_splice_init(&vsock->pkt_queue, &pkts);
        spin_unlock_bh(&vsock->pkt_queue.lock);

        while ((skb = __skb_dequeue(&pkts))) {
                /* Decrement the bytes_unsent counter without deallocating skb
                 * It is freed by the receiver.
                 */
                virtio_transport_consume_skb_sent(skb, false);
                virtio_transport_deliver_tap_pkt(skb);
                virtio_transport_recv_pkt(&loopback_transport, skb,
                                          sock_net(skb->sk));
        }
}

static int __init vsock_loopback_init(void)
{
        struct vsock_loopback *vsock = &the_vsock_loopback;
        int ret;

        vsock->workqueue = alloc_workqueue("vsock-loopback", WQ_PERCPU, 0);
        if (!vsock->workqueue)
                return -ENOMEM;

        skb_queue_head_init(&vsock->pkt_queue);
        INIT_WORK(&vsock->pkt_work, vsock_loopback_work);

        ret = vsock_core_register(&loopback_transport.transport,
                                  VSOCK_TRANSPORT_F_LOCAL);
        if (ret)
                goto out_wq;

        return 0;

out_wq:
        destroy_workqueue(vsock->workqueue);
        return ret;
}

static void __exit vsock_loopback_exit(void)
{
        struct vsock_loopback *vsock = &the_vsock_loopback;

        vsock_core_unregister(&loopback_transport.transport);

        flush_work(&vsock->pkt_work);

        virtio_vsock_skb_queue_purge(&vsock->pkt_queue);

        destroy_workqueue(vsock->workqueue);
}

module_init(vsock_loopback_init);
module_exit(vsock_loopback_exit);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Stefano Garzarella <sgarzare@redhat.com>");
MODULE_DESCRIPTION("loopback transport for vsock");
MODULE_ALIAS_NETPROTO(PF_VSOCK);