// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Tap functions for AF_VSOCK sockets.
 *
 * Code based on net/netlink/af_netlink.c tap functions.
 */

#include <linux/module.h>
#include <net/sock.h>
#include <net/af_vsock.h>
#include <linux/if_arp.h>

static DEFINE_SPINLOCK(vsock_tap_lock);
static struct list_head vsock_tap_all __read_mostly =
                                LIST_HEAD_INIT(vsock_tap_all);

int vsock_add_tap(struct vsock_tap *vt)
{
        if (unlikely(vt->dev->type != ARPHRD_VSOCKMON))
                return -EINVAL;

        __module_get(vt->module);

        spin_lock(&vsock_tap_lock);
        list_add_rcu(&vt->list, &vsock_tap_all);
        spin_unlock(&vsock_tap_lock);

        return 0;
}
EXPORT_SYMBOL_GPL(vsock_add_tap);

int vsock_remove_tap(struct vsock_tap *vt)
{
        struct vsock_tap *tmp;
        bool found = false;

        spin_lock(&vsock_tap_lock);

        list_for_each_entry(tmp, &vsock_tap_all, list) {
                if (vt == tmp) {
                        list_del_rcu(&vt->list);
                        found = true;
                        goto out;
                }
        }

        pr_warn("vsock_remove_tap: %p not found\n", vt);
out:
        spin_unlock(&vsock_tap_lock);

        synchronize_net();

        if (found)
                module_put(vt->module);

        return found ? 0 : -ENODEV;
}
EXPORT_SYMBOL_GPL(vsock_remove_tap);

static int __vsock_deliver_tap_skb(struct sk_buff *skb,
                                   struct net_device *dev)
{
        int ret = 0;
        struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);

        if (nskb) {
                dev_hold(dev);

                nskb->dev = dev;
                ret = dev_queue_xmit(nskb);
                if (unlikely(ret > 0))
                        ret = net_xmit_errno(ret);

                dev_put(dev);
        }

        return ret;
}

static void __vsock_deliver_tap(struct sk_buff *skb)
{
        int ret;
        struct vsock_tap *tmp;

        list_for_each_entry_rcu(tmp, &vsock_tap_all, list) {
                ret = __vsock_deliver_tap_skb(skb, tmp->dev);
                if (unlikely(ret))
                        break;
        }
}

void vsock_deliver_tap(struct sk_buff *build_skb(void *opaque), void *opaque)
{
        struct sk_buff *skb;

        rcu_read_lock();

        if (likely(list_empty(&vsock_tap_all)))
                goto out;

        skb = build_skb(opaque);
        if (skb) {
                __vsock_deliver_tap(skb);
                consume_skb(skb);
        }

out:
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(vsock_deliver_tap);