// SPDX-License-Identifier: GPL-2.0-only
/*
 * common code for virtio vsock
 *
 * Copyright (C) 2013-2015 Red Hat, Inc.
 * Author: Asias He <asias@redhat.com>
 *         Stefan Hajnoczi <stefanha@redhat.com>
 */
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/sched/signal.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/virtio_vsock.h>
#include <uapi/linux/vsockmon.h>

#include <net/sock.h>
#include <net/af_vsock.h>

#define CREATE_TRACE_POINTS
#include <trace/events/vsock_virtio_transport_common.h>

/* How long to wait for graceful shutdown of a connection */
#define VSOCK_CLOSE_TIMEOUT (8 * HZ)

/* Threshold for detecting small packets to copy */
#define GOOD_COPY_LEN  128

static void virtio_transport_cancel_close_work(struct vsock_sock *vsk,
                                               bool cancel_timeout);
static s64 virtio_transport_has_space(struct virtio_vsock_sock *vvs);

static const struct virtio_transport *
virtio_transport_get_ops(struct vsock_sock *vsk)
{
        const struct vsock_transport *t = vsock_core_get_transport(vsk);

        if (WARN_ON(!t))
                return NULL;

        return container_of(t, struct virtio_transport, transport);
}

static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
                                       struct virtio_vsock_pkt_info *info,
                                       size_t pkt_len)
{
        struct iov_iter *iov_iter;

        if (!info->msg)
                return false;

        iov_iter = &info->msg->msg_iter;

        if (iov_iter->iov_offset)
                return false;

        /* We can't send whole iov. */
        if (iov_iter->count > pkt_len)
                return false;

        /* Check that transport can send data in zerocopy mode. */
        t_ops = virtio_transport_get_ops(info->vsk);

        if (t_ops->can_msgzerocopy) {
                int pages_to_send = iov_iter_npages(iov_iter, MAX_SKB_FRAGS);

                /* +1 is for packet header. */
                return t_ops->can_msgzerocopy(pages_to_send + 1);
        }

        return true;
}

static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk,
                                           struct sk_buff *skb,
                                           struct msghdr *msg,
                                           bool zerocopy)
{
        struct ubuf_info *uarg;

        if (msg->msg_ubuf) {
                uarg = msg->msg_ubuf;
                net_zcopy_get(uarg);
        } else {
                struct iov_iter *iter = &msg->msg_iter;
                struct ubuf_info_msgzc *uarg_zc;

                uarg = msg_zerocopy_realloc(sk_vsock(vsk),
                                            iter->count,
                                            NULL, false);
                if (!uarg)
                        return -1;

                uarg_zc = uarg_to_msgzc(uarg);
                uarg_zc->zerocopy = zerocopy ? 1 : 0;
        }

        skb_zcopy_init(skb, uarg);

        return 0;
}

static int virtio_transport_fill_skb(struct sk_buff *skb,
                                     struct virtio_vsock_pkt_info *info,
                                     size_t len,
                                     bool zcopy)
{
        struct msghdr *msg = info->msg;

        if (zcopy)
                return __zerocopy_sg_from_iter(msg, NULL, skb,
                                               &msg->msg_iter, len, NULL);

        virtio_vsock_skb_put(skb, len);
        return skb_copy_datagram_from_iter_full(skb, 0, &msg->msg_iter, len);
}

static void virtio_transport_init_hdr(struct sk_buff *skb,
                                      struct virtio_vsock_pkt_info *info,
                                      size_t payload_len,
                                      u32 src_cid,
                                      u32 src_port,
                                      u32 dst_cid,
                                      u32 dst_port)
{
        struct virtio_vsock_hdr *hdr;

        hdr = virtio_vsock_hdr(skb);
        hdr->type       = cpu_to_le16(info->type);
        hdr->op         = cpu_to_le16(info->op);
        hdr->src_cid    = cpu_to_le64(src_cid);
        hdr->dst_cid    = cpu_to_le64(dst_cid);
        hdr->src_port   = cpu_to_le32(src_port);
        hdr->dst_port   = cpu_to_le32(dst_port);
        hdr->flags      = cpu_to_le32(info->flags);
        hdr->len        = cpu_to_le32(payload_len);
        hdr->buf_alloc  = cpu_to_le32(0);
        hdr->fwd_cnt    = cpu_to_le32(0);
}

static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb,
                                                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)->offset,
                               &iov_iter, to_copy);
}

/* Packet capture */
static struct sk_buff *virtio_transport_build_skb(void *opaque)
{
        struct virtio_vsock_hdr *pkt_hdr;
        struct sk_buff *pkt = opaque;
        struct af_vsockmon_hdr *hdr;
        struct sk_buff *skb;
        size_t payload_len;

        /* 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
         * care of the offset in the original packet.
         */
        pkt_hdr = virtio_vsock_hdr(pkt);
        payload_len = pkt->len;

        skb = alloc_skb(sizeof(*hdr) + sizeof(*pkt_hdr) + payload_len,
                        GFP_ATOMIC);
        if (!skb)
                return NULL;

        hdr = skb_put(skb, sizeof(*hdr));

        /* pkt->hdr is little-endian so no need to byteswap here */
        hdr->src_cid = pkt_hdr->src_cid;
        hdr->src_port = pkt_hdr->src_port;
        hdr->dst_cid = pkt_hdr->dst_cid;
        hdr->dst_port = pkt_hdr->dst_port;

        hdr->transport = cpu_to_le16(AF_VSOCK_TRANSPORT_VIRTIO);
        hdr->len = cpu_to_le16(sizeof(*pkt_hdr));
        memset(hdr->reserved, 0, sizeof(hdr->reserved));

        switch (le16_to_cpu(pkt_hdr->op)) {
        case VIRTIO_VSOCK_OP_REQUEST:
        case VIRTIO_VSOCK_OP_RESPONSE:
                hdr->op = cpu_to_le16(AF_VSOCK_OP_CONNECT);
                break;
        case VIRTIO_VSOCK_OP_RST:
        case VIRTIO_VSOCK_OP_SHUTDOWN:
                hdr->op = cpu_to_le16(AF_VSOCK_OP_DISCONNECT);
                break;
        case VIRTIO_VSOCK_OP_RW:
                hdr->op = cpu_to_le16(AF_VSOCK_OP_PAYLOAD);
                break;
        case VIRTIO_VSOCK_OP_CREDIT_UPDATE:
        case VIRTIO_VSOCK_OP_CREDIT_REQUEST:
                hdr->op = cpu_to_le16(AF_VSOCK_OP_CONTROL);
                break;
        default:
                hdr->op = cpu_to_le16(AF_VSOCK_OP_UNKNOWN);
                break;
        }

        skb_put_data(skb, pkt_hdr, sizeof(*pkt_hdr));

        if (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;
}

void virtio_transport_deliver_tap_pkt(struct sk_buff *skb)
{
        if (virtio_vsock_skb_tap_delivered(skb))
                return;

        vsock_deliver_tap(virtio_transport_build_skb, skb);
        virtio_vsock_skb_set_tap_delivered(skb);
}
EXPORT_SYMBOL_GPL(virtio_transport_deliver_tap_pkt);

static u16 virtio_transport_get_type(struct sock *sk)
{
        if (sk->sk_type == SOCK_STREAM)
                return VIRTIO_VSOCK_TYPE_STREAM;
        else
                return VIRTIO_VSOCK_TYPE_SEQPACKET;
}

/* Returns new sk_buff on success, otherwise returns NULL. */
static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
                                                  size_t payload_len,
                                                  bool zcopy,
                                                  u32 src_cid,
                                                  u32 src_port,
                                                  u32 dst_cid,
                                                  u32 dst_port)
{
        struct vsock_sock *vsk;
        struct sk_buff *skb;
        size_t skb_len;

        skb_len = VIRTIO_VSOCK_SKB_HEADROOM;

        if (!zcopy)
                skb_len += payload_len;

        skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
        if (!skb)
                return NULL;

        virtio_transport_init_hdr(skb, info, payload_len, src_cid, src_port,
                                  dst_cid, dst_port);

        vsk = info->vsk;

        /* If 'vsk' != NULL then payload is always present, so we
         * will never call '__zerocopy_sg_from_iter()' below without
         * setting skb owner in 'skb_set_owner_w()'. The only case
         * when 'vsk' == NULL is VIRTIO_VSOCK_OP_RST control message
         * without payload.
         */
        WARN_ON_ONCE(!(vsk && (info->msg && payload_len)) && zcopy);

        /* Set owner here, because '__zerocopy_sg_from_iter()' uses
         * owner of skb without check to update 'sk_wmem_alloc'.
         */
        if (vsk)
                skb_set_owner_w(skb, sk_vsock(vsk));

        if (info->msg && payload_len > 0) {
                int err;

                err = virtio_transport_fill_skb(skb, info, payload_len, zcopy);
                if (err)
                        goto out;

                if (msg_data_left(info->msg) == 0 &&
                    info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) {
                        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);

                        hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);

                        if (info->msg->msg_flags & MSG_EOR)
                                hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
                }
        }

        if (info->reply)
                virtio_vsock_skb_set_reply(skb);

        trace_virtio_transport_alloc_pkt(src_cid, src_port,
                                         dst_cid, dst_port,
                                         payload_len,
                                         info->type,
                                         info->op,
                                         info->flags,
                                         zcopy);

        return skb;
out:
        kfree_skb(skb);
        return NULL;
}

/* This function can only be used on connecting/connected sockets,
 * since a socket assigned to a transport is required.
 *
 * Do not use on listener sockets!
 */
static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
                                          struct virtio_vsock_pkt_info *info)
{
        u32 max_skb_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
        u32 src_cid, src_port, dst_cid, dst_port;
        const struct virtio_transport *t_ops;
        struct virtio_vsock_sock *vvs;
        u32 pkt_len = info->pkt_len;
        bool can_zcopy = false;
        u32 rest_len;
        int ret;

        info->type = virtio_transport_get_type(sk_vsock(vsk));

        t_ops = virtio_transport_get_ops(vsk);
        if (unlikely(!t_ops))
                return -EFAULT;

        src_cid = t_ops->transport.get_local_cid();
        src_port = vsk->local_addr.svm_port;
        if (!info->remote_cid) {
                dst_cid = vsk->remote_addr.svm_cid;
                dst_port = vsk->remote_addr.svm_port;
        } else {
                dst_cid = info->remote_cid;
                dst_port = info->remote_port;
        }

        vvs = vsk->trans;

        /* virtio_transport_get_credit might return less than pkt_len credit */
        pkt_len = virtio_transport_get_credit(vvs, pkt_len);

        /* Do not send zero length OP_RW pkt */
        if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
                return pkt_len;

        if (info->msg) {
                /* If zerocopy is not enabled by 'setsockopt()', we behave as
                 * there is no MSG_ZEROCOPY flag set.
                 */
                if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY))
                        info->msg->msg_flags &= ~MSG_ZEROCOPY;

                if (info->msg->msg_flags & MSG_ZEROCOPY)
                        can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len);

                if (can_zcopy)
                        max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE,
                                            (MAX_SKB_FRAGS * PAGE_SIZE));
        }

        rest_len = pkt_len;

        do {
                struct sk_buff *skb;
                size_t skb_len;

                skb_len = min(max_skb_len, rest_len);

                skb = virtio_transport_alloc_skb(info, skb_len, can_zcopy,
                                                 src_cid, src_port,
                                                 dst_cid, dst_port);
                if (!skb) {
                        ret = -ENOMEM;
                        break;
                }

                /* We process buffer part by part, allocating skb on
                 * each iteration. If this is last skb for this buffer
                 * and MSG_ZEROCOPY mode is in use - we must allocate
                 * completion for the current syscall.
                 */
                if (info->msg && info->msg->msg_flags & MSG_ZEROCOPY &&
                    skb_len == rest_len && info->op == VIRTIO_VSOCK_OP_RW) {
                        if (virtio_transport_init_zcopy_skb(vsk, skb,
                                                            info->msg,
                                                            can_zcopy)) {
                                kfree_skb(skb);
                                ret = -ENOMEM;
                                break;
                        }
                }

                virtio_transport_inc_tx_pkt(vvs, skb);

                ret = t_ops->send_pkt(skb, info->net);
                if (ret < 0)
                        break;

                /* Both virtio and vhost 'send_pkt()' returns 'skb_len',
                 * but for reliability use 'ret' instead of 'skb_len'.
                 * Also if partial send happens (e.g. 'ret' != 'skb_len')
                 * somehow, we break this loop, but account such returned
                 * value in 'virtio_transport_put_credit()'.
                 */
                rest_len -= ret;

                if (WARN_ONCE(ret != skb_len,
                              "'send_pkt()' returns %i, but %zu expected\n",
                              ret, skb_len))
                        break;
        } while (rest_len);

        virtio_transport_put_credit(vvs, rest_len);

        /* Return number of bytes, if any data has been sent. */
        if (rest_len != pkt_len)
                ret = pkt_len - rest_len;

        return ret;
}

static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs,
                                        u32 len)
{
        if (vvs->buf_used + len > vvs->buf_alloc)
                return false;

        vvs->rx_bytes += len;
        vvs->buf_used += len;
        return true;
}

static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
                                        u32 bytes_read, u32 bytes_dequeued)
{
        vvs->rx_bytes -= bytes_read;
        vvs->buf_used -= bytes_dequeued;
        vvs->fwd_cnt += bytes_dequeued;
}

void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct sk_buff *skb)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);

        spin_lock_bh(&vvs->rx_lock);
        vvs->last_fwd_cnt = vvs->fwd_cnt;
        hdr->fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
        hdr->buf_alloc = cpu_to_le32(vvs->buf_alloc);
        spin_unlock_bh(&vvs->rx_lock);
}
EXPORT_SYMBOL_GPL(virtio_transport_inc_tx_pkt);

void virtio_transport_consume_skb_sent(struct sk_buff *skb, bool consume)
{
        struct sock *s = skb->sk;

        if (s && skb->len) {
                struct vsock_sock *vs = vsock_sk(s);
                struct virtio_vsock_sock *vvs;

                vvs = vs->trans;

                spin_lock_bh(&vvs->tx_lock);
                vvs->bytes_unsent -= skb->len;
                spin_unlock_bh(&vvs->tx_lock);
        }

        if (consume)
                consume_skb(skb);
}
EXPORT_SYMBOL_GPL(virtio_transport_consume_skb_sent);

u32 virtio_transport_get_credit(struct virtio_vsock_sock *vvs, u32 credit)
{
        u32 ret;

        if (!credit)
                return 0;

        spin_lock_bh(&vvs->tx_lock);
        ret = min_t(u32, credit, virtio_transport_has_space(vvs));
        vvs->tx_cnt += ret;
        vvs->bytes_unsent += ret;
        spin_unlock_bh(&vvs->tx_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(virtio_transport_get_credit);

void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit)
{
        if (!credit)
                return;

        spin_lock_bh(&vvs->tx_lock);
        vvs->tx_cnt -= credit;
        vvs->bytes_unsent -= credit;
        spin_unlock_bh(&vvs->tx_lock);
}
EXPORT_SYMBOL_GPL(virtio_transport_put_credit);

static int virtio_transport_send_credit_update(struct vsock_sock *vsk)
{
        struct virtio_vsock_pkt_info info = {
                .op = VIRTIO_VSOCK_OP_CREDIT_UPDATE,
                .vsk = vsk,
                .net = sock_net(sk_vsock(vsk)),
        };

        return virtio_transport_send_pkt_info(vsk, &info);
}

static ssize_t
virtio_transport_stream_do_peek(struct vsock_sock *vsk,
                                struct msghdr *msg,
                                size_t len)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        struct sk_buff *skb;
        size_t total = 0;
        int err;

        spin_lock_bh(&vvs->rx_lock);

        skb_queue_walk(&vvs->rx_queue, skb) {
                size_t bytes;

                bytes = len - total;
                if (bytes > skb->len)
                        bytes = skb->len;

                spin_unlock_bh(&vvs->rx_lock);

                /* sk_lock is held by caller so no one else can dequeue.
                 * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
                 */
                err = skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
                                             &msg->msg_iter, bytes);
                if (err)
                        goto out;

                total += bytes;

                spin_lock_bh(&vvs->rx_lock);

                if (total == len)
                        break;
        }

        spin_unlock_bh(&vvs->rx_lock);

        return total;

out:
        if (total)
                err = total;
        return err;
}

static ssize_t
virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
                                   struct msghdr *msg,
                                   size_t len)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        struct sk_buff *skb;
        u32 fwd_cnt_delta;
        bool low_rx_bytes;
        int err = -EFAULT;
        size_t total = 0;
        u32 free_space;

        spin_lock_bh(&vvs->rx_lock);

        if (WARN_ONCE(skb_queue_empty(&vvs->rx_queue) && vvs->rx_bytes,
                      "rx_queue is empty, but rx_bytes is non-zero\n")) {
                spin_unlock_bh(&vvs->rx_lock);
                return err;
        }

        while (total < len && !skb_queue_empty(&vvs->rx_queue)) {
                size_t bytes, dequeued = 0;

                skb = skb_peek(&vvs->rx_queue);

                bytes = min_t(size_t, len - total,
                              skb->len - VIRTIO_VSOCK_SKB_CB(skb)->offset);

                /* sk_lock is held by caller so no one else can dequeue.
                 * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
                 */
                spin_unlock_bh(&vvs->rx_lock);

                err = skb_copy_datagram_iter(skb,
                                             VIRTIO_VSOCK_SKB_CB(skb)->offset,
                                             &msg->msg_iter, bytes);
                if (err)
                        goto out;

                spin_lock_bh(&vvs->rx_lock);

                total += bytes;

                VIRTIO_VSOCK_SKB_CB(skb)->offset += bytes;

                if (skb->len == VIRTIO_VSOCK_SKB_CB(skb)->offset) {
                        dequeued = le32_to_cpu(virtio_vsock_hdr(skb)->len);
                        __skb_unlink(skb, &vvs->rx_queue);
                        consume_skb(skb);
                }

                virtio_transport_dec_rx_pkt(vvs, bytes, dequeued);
        }

        fwd_cnt_delta = vvs->fwd_cnt - vvs->last_fwd_cnt;
        free_space = vvs->buf_alloc - fwd_cnt_delta;
        low_rx_bytes = (vvs->rx_bytes <
                        sock_rcvlowat(sk_vsock(vsk), 0, INT_MAX));

        spin_unlock_bh(&vvs->rx_lock);

        /* To reduce the number of credit update messages,
         * don't update credits as long as lots of space is available.
         * Note: the limit chosen here is arbitrary. Setting the limit
         * too high causes extra messages. Too low causes transmitter
         * stalls. As stalls are in theory more expensive than extra
         * messages, we set the limit to a high value. TODO: experiment
         * with different values. Also send credit update message when
         * number of bytes in rx queue is not enough to wake up reader.
         */
        if (fwd_cnt_delta &&
            (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE || low_rx_bytes))
                virtio_transport_send_credit_update(vsk);

        return total;

out:
        if (total)
                err = total;
        return err;
}

static ssize_t
virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
                                   struct msghdr *msg)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        struct sk_buff *skb;
        size_t total, len;

        spin_lock_bh(&vvs->rx_lock);

        if (!vvs->msg_count) {
                spin_unlock_bh(&vvs->rx_lock);
                return 0;
        }

        total = 0;
        len = msg_data_left(msg);

        skb_queue_walk(&vvs->rx_queue, skb) {
                struct virtio_vsock_hdr *hdr;

                if (total < len) {
                        size_t bytes;
                        int err;

                        bytes = len - total;
                        if (bytes > skb->len)
                                bytes = skb->len;

                        spin_unlock_bh(&vvs->rx_lock);

                        /* sk_lock is held by caller so no one else can dequeue.
                         * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
                         */
                        err = skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset,
                                                     &msg->msg_iter, bytes);
                        if (err)
                                return err;

                        spin_lock_bh(&vvs->rx_lock);
                }

                total += skb->len;
                hdr = virtio_vsock_hdr(skb);

                if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
                        if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR)
                                msg->msg_flags |= MSG_EOR;

                        break;
                }
        }

        spin_unlock_bh(&vvs->rx_lock);

        return total;
}

static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
                                                 struct msghdr *msg,
                                                 int flags)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        int dequeued_len = 0;
        size_t user_buf_len = msg_data_left(msg);
        bool msg_ready = false;
        struct sk_buff *skb;

        spin_lock_bh(&vvs->rx_lock);

        if (vvs->msg_count == 0) {
                spin_unlock_bh(&vvs->rx_lock);
                return 0;
        }

        while (!msg_ready) {
                struct virtio_vsock_hdr *hdr;
                size_t pkt_len;

                skb = __skb_dequeue(&vvs->rx_queue);
                if (!skb)
                        break;
                hdr = virtio_vsock_hdr(skb);
                pkt_len = (size_t)le32_to_cpu(hdr->len);

                if (dequeued_len >= 0) {
                        size_t bytes_to_copy;

                        bytes_to_copy = min(user_buf_len, pkt_len);

                        if (bytes_to_copy) {
                                int err;

                                /* sk_lock is held by caller so no one else can dequeue.
                                 * Unlock rx_lock since skb_copy_datagram_iter() may sleep.
                                 */
                                spin_unlock_bh(&vvs->rx_lock);

                                err = skb_copy_datagram_iter(skb, 0,
                                                             &msg->msg_iter,
                                                             bytes_to_copy);
                                if (err) {
                                        /* Copy of message failed. Rest of
                                         * fragments will be freed without copy.
                                         */
                                        dequeued_len = err;
                                } else {
                                        user_buf_len -= bytes_to_copy;
                                }

                                spin_lock_bh(&vvs->rx_lock);
                        }

                        if (dequeued_len >= 0)
                                dequeued_len += pkt_len;
                }

                if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
                        msg_ready = true;
                        vvs->msg_count--;

                        if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR)
                                msg->msg_flags |= MSG_EOR;
                }

                virtio_transport_dec_rx_pkt(vvs, pkt_len, pkt_len);
                kfree_skb(skb);
        }

        spin_unlock_bh(&vvs->rx_lock);

        virtio_transport_send_credit_update(vsk);

        return dequeued_len;
}

ssize_t
virtio_transport_stream_dequeue(struct vsock_sock *vsk,
                                struct msghdr *msg,
                                size_t len, int flags)
{
        if (flags & MSG_PEEK)
                return virtio_transport_stream_do_peek(vsk, msg, len);
        else
                return virtio_transport_stream_do_dequeue(vsk, msg, len);
}
EXPORT_SYMBOL_GPL(virtio_transport_stream_dequeue);

ssize_t
virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
                                   struct msghdr *msg,
                                   int flags)
{
        if (flags & MSG_PEEK)
                return virtio_transport_seqpacket_do_peek(vsk, msg);
        else
                return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
}
EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);

static u32 virtio_transport_tx_buf_size(struct virtio_vsock_sock *vvs)
{
        /* The peer advertises its receive buffer via peer_buf_alloc, but we
         * cap it to our local buf_alloc so a remote peer cannot force us to
         * queue more data than our own buffer configuration allows.
         */
        return min(vvs->peer_buf_alloc, vvs->buf_alloc);
}

int
virtio_transport_seqpacket_enqueue(struct vsock_sock *vsk,
                                   struct msghdr *msg,
                                   size_t len)
{
        struct virtio_vsock_sock *vvs = vsk->trans;

        spin_lock_bh(&vvs->tx_lock);

        if (len > virtio_transport_tx_buf_size(vvs)) {
                spin_unlock_bh(&vvs->tx_lock);
                return -EMSGSIZE;
        }

        spin_unlock_bh(&vvs->tx_lock);

        return virtio_transport_stream_enqueue(vsk, msg, len);
}
EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_enqueue);

int
virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
                               struct msghdr *msg,
                               size_t len, int flags)
{
        return -EOPNOTSUPP;
}
EXPORT_SYMBOL_GPL(virtio_transport_dgram_dequeue);

s64 virtio_transport_stream_has_data(struct vsock_sock *vsk)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        s64 bytes;

        spin_lock_bh(&vvs->rx_lock);
        bytes = vvs->rx_bytes;
        spin_unlock_bh(&vvs->rx_lock);

        return bytes;
}
EXPORT_SYMBOL_GPL(virtio_transport_stream_has_data);

u32 virtio_transport_seqpacket_has_data(struct vsock_sock *vsk)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        u32 msg_count;

        spin_lock_bh(&vvs->rx_lock);
        msg_count = vvs->msg_count;
        spin_unlock_bh(&vvs->rx_lock);

        return msg_count;
}
EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_has_data);

static s64 virtio_transport_has_space(struct virtio_vsock_sock *vvs)
{
        s64 bytes;

        /* Use s64 arithmetic so if the peer shrinks peer_buf_alloc while
         * we have bytes in flight (tx_cnt - peer_fwd_cnt), the subtraction
         * does not underflow.
         */
        bytes = (s64)virtio_transport_tx_buf_size(vvs) -
                (vvs->tx_cnt - vvs->peer_fwd_cnt);
        if (bytes < 0)
                bytes = 0;

        return bytes;
}

s64 virtio_transport_stream_has_space(struct vsock_sock *vsk)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        s64 bytes;

        spin_lock_bh(&vvs->tx_lock);
        bytes = virtio_transport_has_space(vvs);
        spin_unlock_bh(&vvs->tx_lock);

        return bytes;
}
EXPORT_SYMBOL_GPL(virtio_transport_stream_has_space);

int virtio_transport_do_socket_init(struct vsock_sock *vsk,
                                    struct vsock_sock *psk)
{
        struct virtio_vsock_sock *vvs;

        vvs = kzalloc_obj(*vvs);
        if (!vvs)
                return -ENOMEM;

        vsk->trans = vvs;
        vvs->vsk = vsk;
        if (psk && psk->trans) {
                struct virtio_vsock_sock *ptrans = psk->trans;

                vvs->peer_buf_alloc = ptrans->peer_buf_alloc;
        }

        if (vsk->buffer_size > VIRTIO_VSOCK_MAX_BUF_SIZE)
                vsk->buffer_size = VIRTIO_VSOCK_MAX_BUF_SIZE;

        vvs->buf_alloc = vsk->buffer_size;

        spin_lock_init(&vvs->rx_lock);
        spin_lock_init(&vvs->tx_lock);
        skb_queue_head_init(&vvs->rx_queue);

        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_do_socket_init);

/* sk_lock held by the caller */
void virtio_transport_notify_buffer_size(struct vsock_sock *vsk, u64 *val)
{
        struct virtio_vsock_sock *vvs = vsk->trans;

        if (*val > VIRTIO_VSOCK_MAX_BUF_SIZE)
                *val = VIRTIO_VSOCK_MAX_BUF_SIZE;

        vvs->buf_alloc = *val;

        virtio_transport_send_credit_update(vsk);
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_buffer_size);

int
virtio_transport_notify_poll_in(struct vsock_sock *vsk,
                                size_t target,
                                bool *data_ready_now)
{
        *data_ready_now = vsock_stream_has_data(vsk) >= target;

        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_poll_in);

int
virtio_transport_notify_poll_out(struct vsock_sock *vsk,
                                 size_t target,
                                 bool *space_avail_now)
{
        s64 free_space;

        free_space = vsock_stream_has_space(vsk);
        if (free_space > 0)
                *space_avail_now = true;
        else if (free_space == 0)
                *space_avail_now = false;

        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_poll_out);

int virtio_transport_notify_recv_init(struct vsock_sock *vsk,
        size_t target, struct vsock_transport_recv_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_recv_init);

int virtio_transport_notify_recv_pre_block(struct vsock_sock *vsk,
        size_t target, struct vsock_transport_recv_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_recv_pre_block);

int virtio_transport_notify_recv_pre_dequeue(struct vsock_sock *vsk,
        size_t target, struct vsock_transport_recv_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_recv_pre_dequeue);

int virtio_transport_notify_recv_post_dequeue(struct vsock_sock *vsk,
        size_t target, ssize_t copied, bool data_read,
        struct vsock_transport_recv_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_recv_post_dequeue);

int virtio_transport_notify_send_init(struct vsock_sock *vsk,
        struct vsock_transport_send_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_send_init);

int virtio_transport_notify_send_pre_block(struct vsock_sock *vsk,
        struct vsock_transport_send_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_send_pre_block);

int virtio_transport_notify_send_pre_enqueue(struct vsock_sock *vsk,
        struct vsock_transport_send_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_send_pre_enqueue);

int virtio_transport_notify_send_post_enqueue(struct vsock_sock *vsk,
        ssize_t written, struct vsock_transport_send_notify_data *data)
{
        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_send_post_enqueue);

u64 virtio_transport_stream_rcvhiwat(struct vsock_sock *vsk)
{
        return vsk->buffer_size;
}
EXPORT_SYMBOL_GPL(virtio_transport_stream_rcvhiwat);

bool virtio_transport_stream_is_active(struct vsock_sock *vsk)
{
        return true;
}
EXPORT_SYMBOL_GPL(virtio_transport_stream_is_active);

int virtio_transport_dgram_bind(struct vsock_sock *vsk,
                                struct sockaddr_vm *addr)
{
        return -EOPNOTSUPP;
}
EXPORT_SYMBOL_GPL(virtio_transport_dgram_bind);

bool virtio_transport_dgram_allow(struct vsock_sock *vsk, u32 cid, u32 port)
{
        return false;
}
EXPORT_SYMBOL_GPL(virtio_transport_dgram_allow);

int virtio_transport_connect(struct vsock_sock *vsk)
{
        struct virtio_vsock_pkt_info info = {
                .op = VIRTIO_VSOCK_OP_REQUEST,
                .vsk = vsk,
                .net = sock_net(sk_vsock(vsk)),
        };

        return virtio_transport_send_pkt_info(vsk, &info);
}
EXPORT_SYMBOL_GPL(virtio_transport_connect);

int virtio_transport_shutdown(struct vsock_sock *vsk, int mode)
{
        struct virtio_vsock_pkt_info info = {
                .op = VIRTIO_VSOCK_OP_SHUTDOWN,
                .flags = (mode & RCV_SHUTDOWN ?
                          VIRTIO_VSOCK_SHUTDOWN_RCV : 0) |
                         (mode & SEND_SHUTDOWN ?
                          VIRTIO_VSOCK_SHUTDOWN_SEND : 0),
                .vsk = vsk,
                .net = sock_net(sk_vsock(vsk)),
        };

        return virtio_transport_send_pkt_info(vsk, &info);
}
EXPORT_SYMBOL_GPL(virtio_transport_shutdown);

int
virtio_transport_dgram_enqueue(struct vsock_sock *vsk,
                               struct sockaddr_vm *remote_addr,
                               struct msghdr *msg,
                               size_t dgram_len)
{
        return -EOPNOTSUPP;
}
EXPORT_SYMBOL_GPL(virtio_transport_dgram_enqueue);

ssize_t
virtio_transport_stream_enqueue(struct vsock_sock *vsk,
                                struct msghdr *msg,
                                size_t len)
{
        struct virtio_vsock_pkt_info info = {
                .op = VIRTIO_VSOCK_OP_RW,
                .msg = msg,
                .pkt_len = len,
                .vsk = vsk,
                .net = sock_net(sk_vsock(vsk)),
        };

        return virtio_transport_send_pkt_info(vsk, &info);
}
EXPORT_SYMBOL_GPL(virtio_transport_stream_enqueue);

void virtio_transport_destruct(struct vsock_sock *vsk)
{
        struct virtio_vsock_sock *vvs = vsk->trans;

        virtio_transport_cancel_close_work(vsk, true);

        kfree(vvs);
        vsk->trans = NULL;
}
EXPORT_SYMBOL_GPL(virtio_transport_destruct);

ssize_t virtio_transport_unsent_bytes(struct vsock_sock *vsk)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        size_t ret;

        spin_lock_bh(&vvs->tx_lock);
        ret = vvs->bytes_unsent;
        spin_unlock_bh(&vvs->tx_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(virtio_transport_unsent_bytes);

static int virtio_transport_reset(struct vsock_sock *vsk,
                                  struct sk_buff *skb)
{
        struct virtio_vsock_pkt_info info = {
                .op = VIRTIO_VSOCK_OP_RST,
                .reply = !!skb,
                .vsk = vsk,
                .net = sock_net(sk_vsock(vsk)),
        };

        /* Send RST only if the original pkt is not a RST pkt */
        if (skb && le16_to_cpu(virtio_vsock_hdr(skb)->op) == VIRTIO_VSOCK_OP_RST)
                return 0;

        return virtio_transport_send_pkt_info(vsk, &info);
}

/* Normally packets are associated with a socket.  There may be no socket if an
 * attempt was made to connect to a socket that does not exist.
 *
 * net refers to the namespace of whoever sent the invalid message. For
 * loopback, this is the namespace of the socket. For vhost, this is the
 * namespace of the VM (i.e., vhost_vsock).
 */
static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
                                          struct sk_buff *skb, struct net *net)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct virtio_vsock_pkt_info info = {
                .op = VIRTIO_VSOCK_OP_RST,
                .type = le16_to_cpu(hdr->type),
                .reply = true,

                /* Set sk owner to socket we are replying to (may be NULL for
                 * non-loopback). This keeps a reference to the sock and
                 * sock_net(sk) until the reply skb is freed.
                 */
                .vsk = vsock_sk(skb->sk),

                /* net is not defined here because we pass it directly to
                 * t->send_pkt(), instead of relying on
                 * virtio_transport_send_pkt_info() to pass it. It is not needed
                 * by virtio_transport_alloc_skb().
                 */
        };
        struct sk_buff *reply;

        /* Send RST only if the original pkt is not a RST pkt */
        if (le16_to_cpu(hdr->op) == VIRTIO_VSOCK_OP_RST)
                return 0;

        if (!t)
                return -ENOTCONN;

        reply = virtio_transport_alloc_skb(&info, 0, false,
                                           le64_to_cpu(hdr->dst_cid),
                                           le32_to_cpu(hdr->dst_port),
                                           le64_to_cpu(hdr->src_cid),
                                           le32_to_cpu(hdr->src_port));
        if (!reply)
                return -ENOMEM;

        return t->send_pkt(reply, net);
}

/* This function should be called with sk_lock held and SOCK_DONE set */
static void virtio_transport_remove_sock(struct vsock_sock *vsk)
{
        struct virtio_vsock_sock *vvs = vsk->trans;

        /* We don't need to take rx_lock, as the socket is closing and we are
         * removing it.
         */
        __skb_queue_purge(&vvs->rx_queue);
        vsock_remove_sock(vsk);
}

static void virtio_transport_cancel_close_work(struct vsock_sock *vsk,
                                               bool cancel_timeout)
{
        struct sock *sk = sk_vsock(vsk);

        if (vsk->close_work_scheduled &&
            (!cancel_timeout || cancel_delayed_work(&vsk->close_work))) {
                vsk->close_work_scheduled = false;

                virtio_transport_remove_sock(vsk);

                /* Release refcnt obtained when we scheduled the timeout */
                sock_put(sk);
        }
}

static void virtio_transport_do_close(struct vsock_sock *vsk,
                                      bool cancel_timeout)
{
        struct sock *sk = sk_vsock(vsk);

        sock_set_flag(sk, SOCK_DONE);
        vsk->peer_shutdown = SHUTDOWN_MASK;
        if (vsock_stream_has_data(vsk) <= 0)
                sk->sk_state = TCP_CLOSING;
        sk->sk_state_change(sk);

        virtio_transport_cancel_close_work(vsk, cancel_timeout);
}

static void virtio_transport_close_timeout(struct work_struct *work)
{
        struct vsock_sock *vsk =
                container_of(work, struct vsock_sock, close_work.work);
        struct sock *sk = sk_vsock(vsk);

        sock_hold(sk);
        lock_sock(sk);

        if (!sock_flag(sk, SOCK_DONE)) {
                (void)virtio_transport_reset(vsk, NULL);

                virtio_transport_do_close(vsk, false);
        }

        vsk->close_work_scheduled = false;

        release_sock(sk);
        sock_put(sk);
}

/* User context, vsk->sk is locked */
static bool virtio_transport_close(struct vsock_sock *vsk)
{
        struct sock *sk = &vsk->sk;

        if (!(sk->sk_state == TCP_ESTABLISHED ||
              sk->sk_state == TCP_CLOSING))
                return true;

        /* Already received SHUTDOWN from peer, reply with RST */
        if ((vsk->peer_shutdown & SHUTDOWN_MASK) == SHUTDOWN_MASK) {
                (void)virtio_transport_reset(vsk, NULL);
                return true;
        }

        if ((sk->sk_shutdown & SHUTDOWN_MASK) != SHUTDOWN_MASK)
                (void)virtio_transport_shutdown(vsk, SHUTDOWN_MASK);

        if (!(current->flags & PF_EXITING))
                vsock_linger(sk);

        if (sock_flag(sk, SOCK_DONE)) {
                return true;
        }

        sock_hold(sk);
        INIT_DELAYED_WORK(&vsk->close_work,
                          virtio_transport_close_timeout);
        vsk->close_work_scheduled = true;
        schedule_delayed_work(&vsk->close_work, VSOCK_CLOSE_TIMEOUT);
        return false;
}

void virtio_transport_release(struct vsock_sock *vsk)
{
        struct sock *sk = &vsk->sk;
        bool remove_sock = true;

        if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
                remove_sock = virtio_transport_close(vsk);

        if (remove_sock) {
                sock_set_flag(sk, SOCK_DONE);
                virtio_transport_remove_sock(vsk);
        }
}
EXPORT_SYMBOL_GPL(virtio_transport_release);

static int
virtio_transport_recv_connecting(struct sock *sk,
                                 struct sk_buff *skb)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct vsock_sock *vsk = vsock_sk(sk);
        int skerr;
        int err;

        switch (le16_to_cpu(hdr->op)) {
        case VIRTIO_VSOCK_OP_RESPONSE:
                sk->sk_state = TCP_ESTABLISHED;
                sk->sk_socket->state = SS_CONNECTED;
                vsock_insert_connected(vsk);
                sk->sk_state_change(sk);
                break;
        case VIRTIO_VSOCK_OP_INVALID:
                break;
        case VIRTIO_VSOCK_OP_RST:
                skerr = ECONNRESET;
                err = 0;
                goto destroy;
        default:
                skerr = EPROTO;
                err = -EINVAL;
                goto destroy;
        }
        return 0;

destroy:
        virtio_transport_reset(vsk, skb);
        sk->sk_state = TCP_CLOSE;
        sk->sk_err = skerr;
        sk_error_report(sk);
        return err;
}

static void
virtio_transport_recv_enqueue(struct vsock_sock *vsk,
                              struct sk_buff *skb)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        bool can_enqueue, free_pkt = false;
        struct virtio_vsock_hdr *hdr;
        u32 len;

        hdr = virtio_vsock_hdr(skb);
        len = le32_to_cpu(hdr->len);

        spin_lock_bh(&vvs->rx_lock);

        can_enqueue = virtio_transport_inc_rx_pkt(vvs, len);
        if (!can_enqueue) {
                free_pkt = true;
                goto out;
        }

        if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM)
                vvs->msg_count++;

        /* Try to copy small packets into the buffer of last packet queued,
         * to avoid wasting memory queueing the entire buffer with a small
         * payload. Skip non-linear (e.g. zerocopy) skbs; these carry payload
         * in skb_shinfo.
         */
        if (len <= GOOD_COPY_LEN && !skb_queue_empty(&vvs->rx_queue) &&
            !skb_is_nonlinear(skb)) {
                struct virtio_vsock_hdr *last_hdr;
                struct sk_buff *last_skb;

                last_skb = skb_peek_tail(&vvs->rx_queue);
                last_hdr = virtio_vsock_hdr(last_skb);

                /* If there is space in the last packet queued, we copy the
                 * new packet in its buffer. We avoid this if the last packet
                 * queued has VIRTIO_VSOCK_SEQ_EOM set, because this is
                 * delimiter of SEQPACKET message, so 'pkt' is the first packet
                 * of a new message.
                 */
                if (skb->len < skb_tailroom(last_skb) &&
                    !(le32_to_cpu(last_hdr->flags) & VIRTIO_VSOCK_SEQ_EOM)) {
                        memcpy(skb_put(last_skb, skb->len), skb->data, skb->len);
                        free_pkt = true;
                        last_hdr->flags |= hdr->flags;
                        le32_add_cpu(&last_hdr->len, len);
                        goto out;
                }
        }

        __skb_queue_tail(&vvs->rx_queue, skb);

out:
        spin_unlock_bh(&vvs->rx_lock);
        if (free_pkt)
                kfree_skb(skb);
}

static int
virtio_transport_recv_connected(struct sock *sk,
                                struct sk_buff *skb)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct vsock_sock *vsk = vsock_sk(sk);
        int err = 0;

        switch (le16_to_cpu(hdr->op)) {
        case VIRTIO_VSOCK_OP_RW:
                virtio_transport_recv_enqueue(vsk, skb);
                vsock_data_ready(sk);
                return err;
        case VIRTIO_VSOCK_OP_CREDIT_REQUEST:
                virtio_transport_send_credit_update(vsk);
                break;
        case VIRTIO_VSOCK_OP_CREDIT_UPDATE:
                sk->sk_write_space(sk);
                break;
        case VIRTIO_VSOCK_OP_SHUTDOWN:
                if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SHUTDOWN_RCV)
                        vsk->peer_shutdown |= RCV_SHUTDOWN;
                if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SHUTDOWN_SEND)
                        vsk->peer_shutdown |= SEND_SHUTDOWN;
                if (vsk->peer_shutdown == SHUTDOWN_MASK) {
                        if (vsock_stream_has_data(vsk) <= 0 && !sock_flag(sk, SOCK_DONE)) {
                                (void)virtio_transport_reset(vsk, NULL);
                                virtio_transport_do_close(vsk, true);
                        }
                        /* Remove this socket anyway because the remote peer sent
                         * the shutdown. This way a new connection will succeed
                         * if the remote peer uses the same source port,
                         * even if the old socket is still unreleased, but now disconnected.
                         */
                        vsock_remove_sock(vsk);
                }
                if (le32_to_cpu(virtio_vsock_hdr(skb)->flags))
                        sk->sk_state_change(sk);
                break;
        case VIRTIO_VSOCK_OP_RST:
                virtio_transport_do_close(vsk, true);
                break;
        default:
                err = -EINVAL;
                break;
        }

        kfree_skb(skb);
        return err;
}

static void
virtio_transport_recv_disconnecting(struct sock *sk,
                                    struct sk_buff *skb)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct vsock_sock *vsk = vsock_sk(sk);

        if (le16_to_cpu(hdr->op) == VIRTIO_VSOCK_OP_RST)
                virtio_transport_do_close(vsk, true);
}

static int
virtio_transport_send_response(struct vsock_sock *vsk,
                               struct sk_buff *skb)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct virtio_vsock_pkt_info info = {
                .op = VIRTIO_VSOCK_OP_RESPONSE,
                .remote_cid = le64_to_cpu(hdr->src_cid),
                .remote_port = le32_to_cpu(hdr->src_port),
                .reply = true,
                .vsk = vsk,
                .net = sock_net(sk_vsock(vsk)),
        };

        return virtio_transport_send_pkt_info(vsk, &info);
}

static bool virtio_transport_space_update(struct sock *sk,
                                          struct sk_buff *skb)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct vsock_sock *vsk = vsock_sk(sk);
        struct virtio_vsock_sock *vvs = vsk->trans;
        bool space_available;

        /* Listener sockets are not associated with any transport, so we are
         * not able to take the state to see if there is space available in the
         * remote peer, but since they are only used to receive requests, we
         * can assume that there is always space available in the other peer.
         */
        if (!vvs)
                return true;

        /* buf_alloc and fwd_cnt is always included in the hdr */
        spin_lock_bh(&vvs->tx_lock);
        vvs->peer_buf_alloc = le32_to_cpu(hdr->buf_alloc);
        vvs->peer_fwd_cnt = le32_to_cpu(hdr->fwd_cnt);
        space_available = virtio_transport_has_space(vvs);
        spin_unlock_bh(&vvs->tx_lock);
        return space_available;
}

/* Handle server socket */
static int
virtio_transport_recv_listen(struct sock *sk, struct sk_buff *skb,
                             struct virtio_transport *t)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct vsock_sock *vsk = vsock_sk(sk);
        struct vsock_sock *vchild;
        struct sock *child;
        int ret;

        if (le16_to_cpu(hdr->op) != VIRTIO_VSOCK_OP_REQUEST) {
                virtio_transport_reset_no_sock(t, skb, sock_net(sk));
                return -EINVAL;
        }

        if (sk_acceptq_is_full(sk)) {
                virtio_transport_reset_no_sock(t, skb, sock_net(sk));
                return -ENOMEM;
        }

        /* __vsock_release() might have already flushed accept_queue.
         * Subsequent enqueues would lead to a memory leak.
         */
        if (sk->sk_shutdown == SHUTDOWN_MASK) {
                virtio_transport_reset_no_sock(t, skb, sock_net(sk));
                return -ESHUTDOWN;
        }

        child = vsock_create_connected(sk);
        if (!child) {
                virtio_transport_reset_no_sock(t, skb, sock_net(sk));
                return -ENOMEM;
        }

        sk_acceptq_added(sk);

        lock_sock_nested(child, SINGLE_DEPTH_NESTING);

        child->sk_state = TCP_ESTABLISHED;

        vchild = vsock_sk(child);
        vsock_addr_init(&vchild->local_addr, le64_to_cpu(hdr->dst_cid),
                        le32_to_cpu(hdr->dst_port));
        vsock_addr_init(&vchild->remote_addr, le64_to_cpu(hdr->src_cid),
                        le32_to_cpu(hdr->src_port));

        ret = vsock_assign_transport(vchild, vsk);
        /* Transport assigned (looking at remote_addr) must be the same
         * where we received the request.
         */
        if (ret || vchild->transport != &t->transport) {
                release_sock(child);
                virtio_transport_reset_no_sock(t, skb, sock_net(sk));
                sock_put(child);
                return ret;
        }

        if (virtio_transport_space_update(child, skb))
                child->sk_write_space(child);

        vsock_insert_connected(vchild);
        vsock_enqueue_accept(sk, child);
        virtio_transport_send_response(vchild, skb);

        release_sock(child);

        sk->sk_data_ready(sk);
        return 0;
}

static bool virtio_transport_valid_type(u16 type)
{
        return (type == VIRTIO_VSOCK_TYPE_STREAM) ||
               (type == VIRTIO_VSOCK_TYPE_SEQPACKET);
}

/* We are under the virtio-vsock's vsock->rx_lock or vhost-vsock's vq->mutex
 * lock.
 */
void virtio_transport_recv_pkt(struct virtio_transport *t,
                               struct sk_buff *skb, struct net *net)
{
        struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
        struct sockaddr_vm src, dst;
        struct vsock_sock *vsk;
        struct sock *sk;
        bool space_available;

        vsock_addr_init(&src, le64_to_cpu(hdr->src_cid),
                        le32_to_cpu(hdr->src_port));
        vsock_addr_init(&dst, le64_to_cpu(hdr->dst_cid),
                        le32_to_cpu(hdr->dst_port));

        trace_virtio_transport_recv_pkt(src.svm_cid, src.svm_port,
                                        dst.svm_cid, dst.svm_port,
                                        le32_to_cpu(hdr->len),
                                        le16_to_cpu(hdr->type),
                                        le16_to_cpu(hdr->op),
                                        le32_to_cpu(hdr->flags),
                                        le32_to_cpu(hdr->buf_alloc),
                                        le32_to_cpu(hdr->fwd_cnt));

        if (!virtio_transport_valid_type(le16_to_cpu(hdr->type))) {
                (void)virtio_transport_reset_no_sock(t, skb, net);
                goto free_pkt;
        }

        /* The socket must be in connected or bound table
         * otherwise send reset back
         */
        sk = vsock_find_connected_socket_net(&src, &dst, net);
        if (!sk) {
                sk = vsock_find_bound_socket_net(&dst, net);
                if (!sk) {
                        (void)virtio_transport_reset_no_sock(t, skb, net);
                        goto free_pkt;
                }
        }

        if (virtio_transport_get_type(sk) != le16_to_cpu(hdr->type)) {
                (void)virtio_transport_reset_no_sock(t, skb, net);
                sock_put(sk);
                goto free_pkt;
        }

        if (!skb_set_owner_sk_safe(skb, sk)) {
                WARN_ONCE(1, "receiving vsock socket has sk_refcnt == 0\n");
                goto free_pkt;
        }

        vsk = vsock_sk(sk);

        lock_sock(sk);

        /* Check if sk has been closed or assigned to another transport before
         * lock_sock (note: listener sockets are not assigned to any transport)
         */
        if (sock_flag(sk, SOCK_DONE) ||
            (sk->sk_state != TCP_LISTEN && vsk->transport != &t->transport)) {
                (void)virtio_transport_reset_no_sock(t, skb, net);
                release_sock(sk);
                sock_put(sk);
                goto free_pkt;
        }

        space_available = virtio_transport_space_update(sk, skb);

        /* Update CID in case it has changed after a transport reset event */
        if (vsk->local_addr.svm_cid != VMADDR_CID_ANY)
                vsk->local_addr.svm_cid = dst.svm_cid;

        if (space_available)
                sk->sk_write_space(sk);

        switch (sk->sk_state) {
        case TCP_LISTEN:
                virtio_transport_recv_listen(sk, skb, t);
                kfree_skb(skb);
                break;
        case TCP_SYN_SENT:
                virtio_transport_recv_connecting(sk, skb);
                kfree_skb(skb);
                break;
        case TCP_ESTABLISHED:
                virtio_transport_recv_connected(sk, skb);
                break;
        case TCP_CLOSING:
                virtio_transport_recv_disconnecting(sk, skb);
                kfree_skb(skb);
                break;
        default:
                (void)virtio_transport_reset_no_sock(t, skb, net);
                kfree_skb(skb);
                break;
        }

        release_sock(sk);

        /* Release refcnt obtained when we fetched this socket out of the
         * bound or connected list.
         */
        sock_put(sk);
        return;

free_pkt:
        kfree_skb(skb);
}
EXPORT_SYMBOL_GPL(virtio_transport_recv_pkt);

/* Remove skbs found in a queue that have a vsk that matches.
 *
 * Each skb is freed.
 *
 * Returns the count of skbs that were reply packets.
 */
int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *queue)
{
        struct sk_buff_head freeme;
        struct sk_buff *skb, *tmp;
        int cnt = 0;

        skb_queue_head_init(&freeme);

        spin_lock_bh(&queue->lock);
        skb_queue_walk_safe(queue, skb, tmp) {
                if (vsock_sk(skb->sk) != vsk)
                        continue;

                __skb_unlink(skb, queue);
                __skb_queue_tail(&freeme, skb);

                if (virtio_vsock_skb_reply(skb))
                        cnt++;
        }
        spin_unlock_bh(&queue->lock);

        __skb_queue_purge(&freeme);

        return cnt;
}
EXPORT_SYMBOL_GPL(virtio_transport_purge_skbs);

int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_actor)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        struct sock *sk = sk_vsock(vsk);
        struct virtio_vsock_hdr *hdr;
        struct sk_buff *skb;
        u32 pkt_len;
        int off = 0;
        int err;

        spin_lock_bh(&vvs->rx_lock);
        /* Use __skb_recv_datagram() for race-free handling of the receive. It
         * works for types other than dgrams.
         */
        skb = __skb_recv_datagram(sk, &vvs->rx_queue, MSG_DONTWAIT, &off, &err);
        if (!skb) {
                spin_unlock_bh(&vvs->rx_lock);
                return err;
        }

        hdr = virtio_vsock_hdr(skb);
        if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM)
                vvs->msg_count--;

        pkt_len = le32_to_cpu(hdr->len);
        virtio_transport_dec_rx_pkt(vvs, pkt_len, pkt_len);
        spin_unlock_bh(&vvs->rx_lock);

        virtio_transport_send_credit_update(vsk);

        return recv_actor(sk, skb);
}
EXPORT_SYMBOL_GPL(virtio_transport_read_skb);

int virtio_transport_notify_set_rcvlowat(struct vsock_sock *vsk, int val)
{
        struct virtio_vsock_sock *vvs = vsk->trans;
        bool send_update;

        spin_lock_bh(&vvs->rx_lock);

        /* If number of available bytes is less than new SO_RCVLOWAT value,
         * kick sender to send more data, because sender may sleep in its
         * 'send()' syscall waiting for enough space at our side. Also
         * don't send credit update when peer already knows actual value -
         * such transmission will be useless.
         */
        send_update = (vvs->rx_bytes < val) &&
                      (vvs->fwd_cnt != vvs->last_fwd_cnt);

        spin_unlock_bh(&vvs->rx_lock);

        if (send_update) {
                int err;

                err = virtio_transport_send_credit_update(vsk);
                if (err < 0)
                        return err;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(virtio_transport_notify_set_rcvlowat);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Asias He");
MODULE_DESCRIPTION("common code for virtio vsock");