/*
 * VMware vSockets Driver
 *
 * Copyright (C) 2007-2013 VMware, Inc. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation version 2 and no later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */

/* Implementation notes:
 *
 * - There are two kinds of sockets: those created by user action (such as
 * calling socket(2)) and those created by incoming connection request packets.
 *
 * - There are two "global" tables, one for bound sockets (sockets that have
 * specified an address that they are responsible for) and one for connected
 * sockets (sockets that have established a connection with another socket).
 * These tables are "global" in that all sockets on the system are placed
 * within them. - Note, though, that the bound table contains an extra entry
 * for a list of unbound sockets and SOCK_DGRAM sockets will always remain in
 * that list. The bound table is used solely for lookup of sockets when packets
 * are received and that's not necessary for SOCK_DGRAM sockets since we create
 * a datagram handle for each and need not perform a lookup.  Keeping SOCK_DGRAM
 * sockets out of the bound hash buckets will reduce the chance of collisions
 * when looking for SOCK_STREAM sockets and prevents us from having to check the
 * socket type in the hash table lookups.
 *
 * - Sockets created by user action will either be "client" sockets that
 * initiate a connection or "server" sockets that listen for connections; we do
 * not support simultaneous connects (two "client" sockets connecting).
 *
 * - "Server" sockets are referred to as listener sockets throughout this
 * implementation because they are in the SS_LISTEN state.  When a connection
 * request is received (the second kind of socket mentioned above), we create a
 * new socket and refer to it as a pending socket.  These pending sockets are
 * placed on the pending connection list of the listener socket.  When future
 * packets are received for the address the listener socket is bound to, we
 * check if the source of the packet is from one that has an existing pending
 * connection.  If it does, we process the packet for the pending socket.  When
 * that socket reaches the connected state, it is removed from the listener
 * socket's pending list and enqueued in the listener socket's accept queue.
 * Callers of accept(2) will accept connected sockets from the listener socket's
 * accept queue.  If the socket cannot be accepted for some reason then it is
 * marked rejected.  Once the connection is accepted, it is owned by the user
 * process and the responsibility for cleanup falls with that user process.
 *
 * - It is possible that these pending sockets will never reach the connected
 * state; in fact, we may never receive another packet after the connection
 * request.  Because of this, we must schedule a cleanup function to run in the
 * future, after some amount of time passes where a connection should have been
 * established.  This function ensures that the socket is off all lists so it
 * cannot be retrieved, then drops all references to the socket so it is cleaned
 * up (sock_put() -> sk_free() -> our sk_destruct implementation).  Note this
 * function will also cleanup rejected sockets, those that reach the connected
 * state but leave it before they have been accepted.
 *
 * - Sockets created by user action will be cleaned up when the user process
 * calls close(2), causing our release implementation to be called. Our release
 * implementation will perform some cleanup then drop the last reference so our
 * sk_destruct implementation is invoked.  Our sk_destruct implementation will
 * perform additional cleanup that's common for both types of sockets.
 *
 * - A socket's reference count is what ensures that the structure won't be
 * freed.  Each entry in a list (such as the "global" bound and connected tables
 * and the listener socket's pending list and connected queue) ensures a
 * reference.  When we defer work until process context and pass a socket as our
 * argument, we must ensure the reference count is increased to ensure the
 * socket isn't freed before the function is run; the deferred function will
 * then drop the reference.
 */

#include <linux/types.h>
#include <linux/bitops.h>
#include <linux/cred.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/list.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/net.h>
#include <linux/poll.h>
#include <linux/skbuff.h>
#include <linux/smp.h>
#include <linux/socket.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <net/sock.h>
#include <net/af_vsock.h>

static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
static void vsock_sk_destruct(struct sock *sk);
static int vsock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);

/* Protocol family. */
static struct proto vsock_proto = {
        .name = "AF_VSOCK",
        .owner = THIS_MODULE,
        .obj_size = sizeof(struct vsock_sock),
};

/* The default peer timeout indicates how long we will wait for a peer response
 * to a control message.
 */
#define VSOCK_DEFAULT_CONNECT_TIMEOUT (2 * HZ)

#define SS_LISTEN 255

static const struct vsock_transport *transport;
static DEFINE_MUTEX(vsock_register_mutex);

/**** EXPORTS ****/

/* Get the ID of the local context.  This is transport dependent. */

int vm_sockets_get_local_cid(void)
{
        return transport->get_local_cid();
}
EXPORT_SYMBOL_GPL(vm_sockets_get_local_cid);

/**** UTILS ****/

/* Each bound VSocket is stored in the bind hash table and each connected
 * VSocket is stored in the connected hash table.
 *
 * Unbound sockets are all put on the same list attached to the end of the hash
 * table (vsock_unbound_sockets).  Bound sockets are added to the hash table in
 * the bucket that their local address hashes to (vsock_bound_sockets(addr)
 * represents the list that addr hashes to).
 *
 * Specifically, we initialize the vsock_bind_table array to a size of
 * VSOCK_HASH_SIZE + 1 so that vsock_bind_table[0] through
 * vsock_bind_table[VSOCK_HASH_SIZE - 1] are for bound sockets and
 * vsock_bind_table[VSOCK_HASH_SIZE] is for unbound sockets.  The hash function
 * mods with VSOCK_HASH_SIZE to ensure this.
 */
#define VSOCK_HASH_SIZE         251
#define MAX_PORT_RETRIES        24

#define VSOCK_HASH(addr)        ((addr)->svm_port % VSOCK_HASH_SIZE)
#define vsock_bound_sockets(addr) (&vsock_bind_table[VSOCK_HASH(addr)])
#define vsock_unbound_sockets     (&vsock_bind_table[VSOCK_HASH_SIZE])

/* XXX This can probably be implemented in a better way. */
#define VSOCK_CONN_HASH(src, dst)                               \
        (((src)->svm_cid ^ (dst)->svm_port) % VSOCK_HASH_SIZE)
#define vsock_connected_sockets(src, dst)               \
        (&vsock_connected_table[VSOCK_CONN_HASH(src, dst)])
#define vsock_connected_sockets_vsk(vsk)                                \
        vsock_connected_sockets(&(vsk)->remote_addr, &(vsk)->local_addr)

static struct list_head vsock_bind_table[VSOCK_HASH_SIZE + 1];
static struct list_head vsock_connected_table[VSOCK_HASH_SIZE];
static DEFINE_SPINLOCK(vsock_table_lock);

/* Autobind this socket to the local address if necessary. */
static int vsock_auto_bind(struct vsock_sock *vsk)
{
        struct sock *sk = sk_vsock(vsk);
        struct sockaddr_vm local_addr;

        if (vsock_addr_bound(&vsk->local_addr))
                return 0;
        vsock_addr_init(&local_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
        return __vsock_bind(sk, &local_addr);
}

static void vsock_init_tables(void)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(vsock_bind_table); i++)
                INIT_LIST_HEAD(&vsock_bind_table[i]);

        for (i = 0; i < ARRAY_SIZE(vsock_connected_table); i++)
                INIT_LIST_HEAD(&vsock_connected_table[i]);
}

static void __vsock_insert_bound(struct list_head *list,
                                 struct vsock_sock *vsk)
{
        sock_hold(&vsk->sk);
        list_add(&vsk->bound_table, list);
}

static void __vsock_insert_connected(struct list_head *list,
                                     struct vsock_sock *vsk)
{
        sock_hold(&vsk->sk);
        list_add(&vsk->connected_table, list);
}

static void __vsock_remove_bound(struct vsock_sock *vsk)
{
        list_del_init(&vsk->bound_table);
        sock_put(&vsk->sk);
}

static void __vsock_remove_connected(struct vsock_sock *vsk)
{
        list_del_init(&vsk->connected_table);
        sock_put(&vsk->sk);
}

static struct sock *__vsock_find_bound_socket(struct sockaddr_vm *addr)
{
        struct vsock_sock *vsk;

        list_for_each_entry(vsk, vsock_bound_sockets(addr), bound_table)
                if (addr->svm_port == vsk->local_addr.svm_port)
                        return sk_vsock(vsk);

        return NULL;
}

static struct sock *__vsock_find_connected_socket(struct sockaddr_vm *src,
                                                  struct sockaddr_vm *dst)
{
        struct vsock_sock *vsk;

        list_for_each_entry(vsk, vsock_connected_sockets(src, dst),
                            connected_table) {
                if (vsock_addr_equals_addr(src, &vsk->remote_addr) &&
                    dst->svm_port == vsk->local_addr.svm_port) {
                        return sk_vsock(vsk);
                }
        }

        return NULL;
}

static bool __vsock_in_bound_table(struct vsock_sock *vsk)
{
        return !list_empty(&vsk->bound_table);
}

static bool __vsock_in_connected_table(struct vsock_sock *vsk)
{
        return !list_empty(&vsk->connected_table);
}

static void vsock_insert_unbound(struct vsock_sock *vsk)
{
        spin_lock_bh(&vsock_table_lock);
        __vsock_insert_bound(vsock_unbound_sockets, vsk);
        spin_unlock_bh(&vsock_table_lock);
}

void vsock_insert_connected(struct vsock_sock *vsk)
{
        struct list_head *list = vsock_connected_sockets(
                &vsk->remote_addr, &vsk->local_addr);

        spin_lock_bh(&vsock_table_lock);
        __vsock_insert_connected(list, vsk);
        spin_unlock_bh(&vsock_table_lock);
}
EXPORT_SYMBOL_GPL(vsock_insert_connected);

void vsock_remove_bound(struct vsock_sock *vsk)
{
        spin_lock_bh(&vsock_table_lock);
        __vsock_remove_bound(vsk);
        spin_unlock_bh(&vsock_table_lock);
}
EXPORT_SYMBOL_GPL(vsock_remove_bound);

void vsock_remove_connected(struct vsock_sock *vsk)
{
        spin_lock_bh(&vsock_table_lock);
        __vsock_remove_connected(vsk);
        spin_unlock_bh(&vsock_table_lock);
}
EXPORT_SYMBOL_GPL(vsock_remove_connected);

struct sock *vsock_find_bound_socket(struct sockaddr_vm *addr)
{
        struct sock *sk;

        spin_lock_bh(&vsock_table_lock);
        sk = __vsock_find_bound_socket(addr);
        if (sk)
                sock_hold(sk);

        spin_unlock_bh(&vsock_table_lock);

        return sk;
}
EXPORT_SYMBOL_GPL(vsock_find_bound_socket);

struct sock *vsock_find_connected_socket(struct sockaddr_vm *src,
                                         struct sockaddr_vm *dst)
{
        struct sock *sk;

        spin_lock_bh(&vsock_table_lock);
        sk = __vsock_find_connected_socket(src, dst);
        if (sk)
                sock_hold(sk);

        spin_unlock_bh(&vsock_table_lock);

        return sk;
}
EXPORT_SYMBOL_GPL(vsock_find_connected_socket);

static bool vsock_in_bound_table(struct vsock_sock *vsk)
{
        bool ret;

        spin_lock_bh(&vsock_table_lock);
        ret = __vsock_in_bound_table(vsk);
        spin_unlock_bh(&vsock_table_lock);

        return ret;
}

static bool vsock_in_connected_table(struct vsock_sock *vsk)
{
        bool ret;

        spin_lock_bh(&vsock_table_lock);
        ret = __vsock_in_connected_table(vsk);
        spin_unlock_bh(&vsock_table_lock);

        return ret;
}

void vsock_for_each_connected_socket(void (*fn)(struct sock *sk))
{
        int i;

        spin_lock_bh(&vsock_table_lock);

        for (i = 0; i < ARRAY_SIZE(vsock_connected_table); i++) {
                struct vsock_sock *vsk;
                list_for_each_entry(vsk, &vsock_connected_table[i],
                                    connected_table)
                        fn(sk_vsock(vsk));
        }

        spin_unlock_bh(&vsock_table_lock);
}
EXPORT_SYMBOL_GPL(vsock_for_each_connected_socket);

void vsock_add_pending(struct sock *listener, struct sock *pending)
{
        struct vsock_sock *vlistener;
        struct vsock_sock *vpending;

        vlistener = vsock_sk(listener);
        vpending = vsock_sk(pending);

        sock_hold(pending);
        sock_hold(listener);
        list_add_tail(&vpending->pending_links, &vlistener->pending_links);
}
EXPORT_SYMBOL_GPL(vsock_add_pending);

void vsock_remove_pending(struct sock *listener, struct sock *pending)
{
        struct vsock_sock *vpending = vsock_sk(pending);

        list_del_init(&vpending->pending_links);
        sock_put(listener);
        sock_put(pending);
}
EXPORT_SYMBOL_GPL(vsock_remove_pending);

void vsock_enqueue_accept(struct sock *listener, struct sock *connected)
{
        struct vsock_sock *vlistener;
        struct vsock_sock *vconnected;

        vlistener = vsock_sk(listener);
        vconnected = vsock_sk(connected);

        sock_hold(connected);
        sock_hold(listener);
        list_add_tail(&vconnected->accept_queue, &vlistener->accept_queue);
}
EXPORT_SYMBOL_GPL(vsock_enqueue_accept);

static struct sock *vsock_dequeue_accept(struct sock *listener)
{
        struct vsock_sock *vlistener;
        struct vsock_sock *vconnected;

        vlistener = vsock_sk(listener);

        if (list_empty(&vlistener->accept_queue))
                return NULL;

        vconnected = list_entry(vlistener->accept_queue.next,
                                struct vsock_sock, accept_queue);

        list_del_init(&vconnected->accept_queue);
        sock_put(listener);
        /* The caller will need a reference on the connected socket so we let
         * it call sock_put().
         */

        return sk_vsock(vconnected);
}

static bool vsock_is_accept_queue_empty(struct sock *sk)
{
        struct vsock_sock *vsk = vsock_sk(sk);
        return list_empty(&vsk->accept_queue);
}

static bool vsock_is_pending(struct sock *sk)
{
        struct vsock_sock *vsk = vsock_sk(sk);
        return !list_empty(&vsk->pending_links);
}

static int vsock_send_shutdown(struct sock *sk, int mode)
{
        return transport->shutdown(vsock_sk(sk), mode);
}

void vsock_pending_work(struct work_struct *work)
{
        struct sock *sk;
        struct sock *listener;
        struct vsock_sock *vsk;
        bool cleanup;

        vsk = container_of(work, struct vsock_sock, dwork.work);
        sk = sk_vsock(vsk);
        listener = vsk->listener;
        cleanup = true;

        lock_sock(listener);
        lock_sock(sk);

        if (vsock_is_pending(sk)) {
                vsock_remove_pending(listener, sk);
        } else if (!vsk->rejected) {
                /* We are not on the pending list and accept() did not reject
                 * us, so we must have been accepted by our user process.  We
                 * just need to drop our references to the sockets and be on
                 * our way.
                 */
                cleanup = false;
                goto out;
        }

        listener->sk_ack_backlog--;

        /* We need to remove ourself from the global connected sockets list so
         * incoming packets can't find this socket, and to reduce the reference
         * count.
         */
        if (vsock_in_connected_table(vsk))
                vsock_remove_connected(vsk);

        sk->sk_state = SS_FREE;

out:
        release_sock(sk);
        release_sock(listener);
        if (cleanup)
                sock_put(sk);

        sock_put(sk);
        sock_put(listener);
}
EXPORT_SYMBOL_GPL(vsock_pending_work);

/**** SOCKET OPERATIONS ****/

static int __vsock_bind_stream(struct vsock_sock *vsk,
                               struct sockaddr_vm *addr)
{
        static u32 port = LAST_RESERVED_PORT + 1;
        struct sockaddr_vm new_addr;

        vsock_addr_init(&new_addr, addr->svm_cid, addr->svm_port);

        if (addr->svm_port == VMADDR_PORT_ANY) {
                bool found = false;
                unsigned int i;

                for (i = 0; i < MAX_PORT_RETRIES; i++) {
                        if (port <= LAST_RESERVED_PORT)
                                port = LAST_RESERVED_PORT + 1;

                        new_addr.svm_port = port++;

                        if (!__vsock_find_bound_socket(&new_addr)) {
                                found = true;
                                break;
                        }
                }

                if (!found)
                        return -EADDRNOTAVAIL;
        } else {
                /* If port is in reserved range, ensure caller
                 * has necessary privileges.
                 */
                if (addr->svm_port <= LAST_RESERVED_PORT &&
                    !capable(CAP_NET_BIND_SERVICE)) {
                        return -EACCES;
                }

                if (__vsock_find_bound_socket(&new_addr))
                        return -EADDRINUSE;
        }

        vsock_addr_init(&vsk->local_addr, new_addr.svm_cid, new_addr.svm_port);

        /* Remove stream sockets from the unbound list and add them to the hash
         * table for easy lookup by its address.  The unbound list is simply an
         * extra entry at the end of the hash table, a trick used by AF_UNIX.
         */
        __vsock_remove_bound(vsk);
        __vsock_insert_bound(vsock_bound_sockets(&vsk->local_addr), vsk);

        return 0;
}

static int __vsock_bind_dgram(struct vsock_sock *vsk,
                              struct sockaddr_vm *addr)
{
        return transport->dgram_bind(vsk, addr);
}

static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr)
{
        struct vsock_sock *vsk = vsock_sk(sk);
        u32 cid;
        int retval;

        /* First ensure this socket isn't already bound. */
        if (vsock_addr_bound(&vsk->local_addr))
                return -EINVAL;

        /* Now bind to the provided address or select appropriate values if
         * none are provided (VMADDR_CID_ANY and VMADDR_PORT_ANY).  Note that
         * like AF_INET prevents binding to a non-local IP address (in most
         * cases), we only allow binding to the local CID.
         */
        cid = transport->get_local_cid();
        if (addr->svm_cid != cid && addr->svm_cid != VMADDR_CID_ANY)
                return -EADDRNOTAVAIL;

        switch (sk->sk_socket->type) {
        case SOCK_STREAM:
                spin_lock_bh(&vsock_table_lock);
                retval = __vsock_bind_stream(vsk, addr);
                spin_unlock_bh(&vsock_table_lock);
                break;

        case SOCK_DGRAM:
                retval = __vsock_bind_dgram(vsk, addr);
                break;

        default:
                retval = -EINVAL;
                break;
        }

        return retval;
}

struct sock *__vsock_create(struct net *net,
                            struct socket *sock,
                            struct sock *parent,
                            gfp_t priority,
                            unsigned short type)
{
        struct sock *sk;
        struct vsock_sock *psk;
        struct vsock_sock *vsk;

        sk = sk_alloc(net, AF_VSOCK, priority, &vsock_proto);
        if (!sk)
                return NULL;

        sock_init_data(sock, sk);

        /* sk->sk_type is normally set in sock_init_data, but only if sock is
         * non-NULL. We make sure that our sockets always have a type by
         * setting it here if needed.
         */
        if (!sock)
                sk->sk_type = type;

        vsk = vsock_sk(sk);
        vsock_addr_init(&vsk->local_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
        vsock_addr_init(&vsk->remote_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);

        sk->sk_destruct = vsock_sk_destruct;
        sk->sk_backlog_rcv = vsock_queue_rcv_skb;
        sk->sk_state = 0;
        sock_reset_flag(sk, SOCK_DONE);

        INIT_LIST_HEAD(&vsk->bound_table);
        INIT_LIST_HEAD(&vsk->connected_table);
        vsk->listener = NULL;
        INIT_LIST_HEAD(&vsk->pending_links);
        INIT_LIST_HEAD(&vsk->accept_queue);
        vsk->rejected = false;
        vsk->sent_request = false;
        vsk->ignore_connecting_rst = false;
        vsk->peer_shutdown = 0;

        psk = parent ? vsock_sk(parent) : NULL;
        if (parent) {
                vsk->trusted = psk->trusted;
                vsk->owner = get_cred(psk->owner);
                vsk->connect_timeout = psk->connect_timeout;
        } else {
                vsk->trusted = capable(CAP_NET_ADMIN);
                vsk->owner = get_current_cred();
                vsk->connect_timeout = VSOCK_DEFAULT_CONNECT_TIMEOUT;
        }

        if (transport->init(vsk, psk) < 0) {
                sk_free(sk);
                return NULL;
        }

        if (sock)
                vsock_insert_unbound(vsk);

        return sk;
}
EXPORT_SYMBOL_GPL(__vsock_create);

static void __vsock_release(struct sock *sk)
{
        if (sk) {
                struct sk_buff *skb;
                struct sock *pending;
                struct vsock_sock *vsk;

                vsk = vsock_sk(sk);
                pending = NULL; /* Compiler warning. */

                if (vsock_in_bound_table(vsk))
                        vsock_remove_bound(vsk);

                if (vsock_in_connected_table(vsk))
                        vsock_remove_connected(vsk);

                transport->release(vsk);

                lock_sock(sk);
                sock_orphan(sk);
                sk->sk_shutdown = SHUTDOWN_MASK;

                while ((skb = skb_dequeue(&sk->sk_receive_queue)))
                        kfree_skb(skb);

                /* Clean up any sockets that never were accepted. */
                while ((pending = vsock_dequeue_accept(sk)) != NULL) {
                        __vsock_release(pending);
                        sock_put(pending);
                }

                release_sock(sk);
                sock_put(sk);
        }
}

static void vsock_sk_destruct(struct sock *sk)
{
        struct vsock_sock *vsk = vsock_sk(sk);

        transport->destruct(vsk);

        /* When clearing these addresses, there's no need to set the family and
         * possibly register the address family with the kernel.
         */
        vsock_addr_init(&vsk->local_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
        vsock_addr_init(&vsk->remote_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);

        put_cred(vsk->owner);
}

static int vsock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{
        int err;

        err = sock_queue_rcv_skb(sk, skb);
        if (err)
                kfree_skb(skb);

        return err;
}

s64 vsock_stream_has_data(struct vsock_sock *vsk)
{
        return transport->stream_has_data(vsk);
}
EXPORT_SYMBOL_GPL(vsock_stream_has_data);

s64 vsock_stream_has_space(struct vsock_sock *vsk)
{
        return transport->stream_has_space(vsk);
}
EXPORT_SYMBOL_GPL(vsock_stream_has_space);

static int vsock_release(struct socket *sock)
{
        __vsock_release(sock->sk);
        sock->sk = NULL;
        sock->state = SS_FREE;

        return 0;
}

static int
vsock_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
{
        int err;
        struct sock *sk;
        struct sockaddr_vm *vm_addr;

        sk = sock->sk;

        if (vsock_addr_cast(addr, addr_len, &vm_addr) != 0)
                return -EINVAL;

        lock_sock(sk);
        err = __vsock_bind(sk, vm_addr);
        release_sock(sk);

        return err;
}

static int vsock_getname(struct socket *sock,
                         struct sockaddr *addr, int *addr_len, int peer)
{
        int err;
        struct sock *sk;
        struct vsock_sock *vsk;
        struct sockaddr_vm *vm_addr;

        sk = sock->sk;
        vsk = vsock_sk(sk);
        err = 0;

        lock_sock(sk);

        if (peer) {
                if (sock->state != SS_CONNECTED) {
                        err = -ENOTCONN;
                        goto out;
                }
                vm_addr = &vsk->remote_addr;
        } else {
                vm_addr = &vsk->local_addr;
        }

        if (!vm_addr) {
                err = -EINVAL;
                goto out;
        }

        /* sys_getsockname() and sys_getpeername() pass us a
         * MAX_SOCK_ADDR-sized buffer and don't set addr_len.  Unfortunately
         * that macro is defined in socket.c instead of .h, so we hardcode its
         * value here.
         */
        BUILD_BUG_ON(sizeof(*vm_addr) > 128);
        memcpy(addr, vm_addr, sizeof(*vm_addr));
        *addr_len = sizeof(*vm_addr);

out:
        release_sock(sk);
        return err;
}

static int vsock_shutdown(struct socket *sock, int mode)
{
        int err;
        struct sock *sk;

        /* User level uses SHUT_RD (0) and SHUT_WR (1), but the kernel uses
         * RCV_SHUTDOWN (1) and SEND_SHUTDOWN (2), so we must increment mode
         * here like the other address families do.  Note also that the
         * increment makes SHUT_RDWR (2) into RCV_SHUTDOWN | SEND_SHUTDOWN (3),
         * which is what we want.
         */
        mode++;

        if ((mode & ~SHUTDOWN_MASK) || !mode)
                return -EINVAL;

        /* If this is a STREAM socket and it is not connected then bail out
         * immediately.  If it is a DGRAM socket then we must first kick the
         * socket so that it wakes up from any sleeping calls, for example
         * recv(), and then afterwards return the error.
         */

        sk = sock->sk;
        if (sock->state == SS_UNCONNECTED) {
                err = -ENOTCONN;
                if (sk->sk_type == SOCK_STREAM)
                        return err;
        } else {
                sock->state = SS_DISCONNECTING;
                err = 0;
        }

        /* Receive and send shutdowns are treated alike. */
        mode = mode & (RCV_SHUTDOWN | SEND_SHUTDOWN);
        if (mode) {
                lock_sock(sk);
                sk->sk_shutdown |= mode;
                sk->sk_state_change(sk);
                release_sock(sk);

                if (sk->sk_type == SOCK_STREAM) {
                        sock_reset_flag(sk, SOCK_DONE);
                        vsock_send_shutdown(sk, mode);
                }
        }

        return err;
}

static unsigned int vsock_poll(struct file *file, struct socket *sock,
                               poll_table *wait)
{
        struct sock *sk;
        unsigned int mask;
        struct vsock_sock *vsk;

        sk = sock->sk;
        vsk = vsock_sk(sk);

        poll_wait(file, sk_sleep(sk), wait);
        mask = 0;

        if (sk->sk_err)
                /* Signify that there has been an error on this socket. */
                mask |= POLLERR;

        /* INET sockets treat local write shutdown and peer write shutdown as a
         * case of POLLHUP set.
         */
        if ((sk->sk_shutdown == SHUTDOWN_MASK) ||
            ((sk->sk_shutdown & SEND_SHUTDOWN) &&
             (vsk->peer_shutdown & SEND_SHUTDOWN))) {
                mask |= POLLHUP;
        }

        if (sk->sk_shutdown & RCV_SHUTDOWN ||
            vsk->peer_shutdown & SEND_SHUTDOWN) {
                mask |= POLLRDHUP;
        }

        if (sock->type == SOCK_DGRAM) {
                /* For datagram sockets we can read if there is something in
                 * the queue and write as long as the socket isn't shutdown for
                 * sending.
                 */
                if (!skb_queue_empty(&sk->sk_receive_queue) ||
                    (sk->sk_shutdown & RCV_SHUTDOWN)) {
                        mask |= POLLIN | POLLRDNORM;
                }

                if (!(sk->sk_shutdown & SEND_SHUTDOWN))
                        mask |= POLLOUT | POLLWRNORM | POLLWRBAND;

        } else if (sock->type == SOCK_STREAM) {
                lock_sock(sk);

                /* Listening sockets that have connections in their accept
                 * queue can be read.
                 */
                if (sk->sk_state == SS_LISTEN
                    && !vsock_is_accept_queue_empty(sk))
                        mask |= POLLIN | POLLRDNORM;

                /* If there is something in the queue then we can read. */
                if (transport->stream_is_active(vsk) &&
                    !(sk->sk_shutdown & RCV_SHUTDOWN)) {
                        bool data_ready_now = false;
                        int ret = transport->notify_poll_in(
                                        vsk, 1, &data_ready_now);
                        if (ret < 0) {
                                mask |= POLLERR;
                        } else {
                                if (data_ready_now)
                                        mask |= POLLIN | POLLRDNORM;

                        }
                }

                /* Sockets whose connections have been closed, reset, or
                 * terminated should also be considered read, and we check the
                 * shutdown flag for that.
                 */
                if (sk->sk_shutdown & RCV_SHUTDOWN ||
                    vsk->peer_shutdown & SEND_SHUTDOWN) {
                        mask |= POLLIN | POLLRDNORM;
                }

                /* Connected sockets that can produce data can be written. */
                if (sk->sk_state == SS_CONNECTED) {
                        if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
                                bool space_avail_now = false;
                                int ret = transport->notify_poll_out(
                                                vsk, 1, &space_avail_now);
                                if (ret < 0) {
                                        mask |= POLLERR;
                                } else {
                                        if (space_avail_now)
                                                /* Remove POLLWRBAND since INET
                                                 * sockets are not setting it.
                                                 */
                                                mask |= POLLOUT | POLLWRNORM;

                                }
                        }
                }

                /* Simulate INET socket poll behaviors, which sets
                 * POLLOUT|POLLWRNORM when peer is closed and nothing to read,
                 * but local send is not shutdown.
                 */
                if (sk->sk_state == SS_UNCONNECTED) {
                        if (!(sk->sk_shutdown & SEND_SHUTDOWN))
                                mask |= POLLOUT | POLLWRNORM;

                }

                release_sock(sk);
        }

        return mask;
}

static int vsock_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
                               struct msghdr *msg, size_t len)
{
        int err;
        struct sock *sk;
        struct vsock_sock *vsk;
        struct sockaddr_vm *remote_addr;

        if (msg->msg_flags & MSG_OOB)
                return -EOPNOTSUPP;

        /* For now, MSG_DONTWAIT is always assumed... */
        err = 0;
        sk = sock->sk;
        vsk = vsock_sk(sk);

        lock_sock(sk);

        err = vsock_auto_bind(vsk);
        if (err)
                goto out;


        /* If the provided message contains an address, use that.  Otherwise
         * fall back on the socket's remote handle (if it has been connected).
         */
        if (msg->msg_name &&
            vsock_addr_cast(msg->msg_name, msg->msg_namelen,
                            &remote_addr) == 0) {
                /* Ensure this address is of the right type and is a valid
                 * destination.
                 */

                if (remote_addr->svm_cid == VMADDR_CID_ANY)
                        remote_addr->svm_cid = transport->get_local_cid();

                if (!vsock_addr_bound(remote_addr)) {
                        err = -EINVAL;
                        goto out;
                }
        } else if (sock->state == SS_CONNECTED) {
                remote_addr = &vsk->remote_addr;

                if (remote_addr->svm_cid == VMADDR_CID_ANY)
                        remote_addr->svm_cid = transport->get_local_cid();

                /* XXX Should connect() or this function ensure remote_addr is
                 * bound?
                 */

                if (!vsock_addr_bound(&vsk->remote_addr)) {
                        err = -EINVAL;
                        goto out;
                }
        } else {
                err = -EINVAL;
                goto out;
        }

        if (!transport->dgram_allow(remote_addr->svm_cid,
                                    remote_addr->svm_port)) {
                err = -EINVAL;
                goto out;
        }

        err = transport->dgram_enqueue(vsk, remote_addr, msg->msg_iov, len);

out:
        release_sock(sk);
        return err;
}

static int vsock_dgram_connect(struct socket *sock,
                               struct sockaddr *addr, int addr_len, int flags)
{
        int err;
        struct sock *sk;
        struct vsock_sock *vsk;
        struct sockaddr_vm *remote_addr;

        sk = sock->sk;
        vsk = vsock_sk(sk);

        err = vsock_addr_cast(addr, addr_len, &remote_addr);
        if (err == -EAFNOSUPPORT && remote_addr->svm_family == AF_UNSPEC) {
                lock_sock(sk);
                vsock_addr_init(&vsk->remote_addr, VMADDR_CID_ANY,
                                VMADDR_PORT_ANY);
                sock->state = SS_UNCONNECTED;
                release_sock(sk);
                return 0;
        } else if (err != 0)
                return -EINVAL;

        lock_sock(sk);

        err = vsock_auto_bind(vsk);
        if (err)
                goto out;

        if (!transport->dgram_allow(remote_addr->svm_cid,
                                    remote_addr->svm_port)) {
                err = -EINVAL;
                goto out;
        }

        memcpy(&vsk->remote_addr, remote_addr, sizeof(vsk->remote_addr));
        sock->state = SS_CONNECTED;

out:
        release_sock(sk);
        return err;
}

static int vsock_dgram_recvmsg(struct kiocb *kiocb, struct socket *sock,
                               struct msghdr *msg, size_t len, int flags)
{
        return transport->dgram_dequeue(kiocb, vsock_sk(sock->sk), msg, len,
                                        flags);
}

static const struct proto_ops vsock_dgram_ops = {
        .family = PF_VSOCK,
        .owner = THIS_MODULE,
        .release = vsock_release,
        .bind = vsock_bind,
        .connect = vsock_dgram_connect,
        .socketpair = sock_no_socketpair,
        .accept = sock_no_accept,
        .getname = vsock_getname,
        .poll = vsock_poll,
        .ioctl = sock_no_ioctl,
        .listen = sock_no_listen,
        .shutdown = vsock_shutdown,
        .setsockopt = sock_no_setsockopt,
        .getsockopt = sock_no_getsockopt,
        .sendmsg = vsock_dgram_sendmsg,
        .recvmsg = vsock_dgram_recvmsg,
        .mmap = sock_no_mmap,
        .sendpage = sock_no_sendpage,
};

static void vsock_connect_timeout(struct work_struct *work)
{
        struct sock *sk;
        struct vsock_sock *vsk;

        vsk = container_of(work, struct vsock_sock, dwork.work);
        sk = sk_vsock(vsk);

        lock_sock(sk);
        if (sk->sk_state == SS_CONNECTING &&
            (sk->sk_shutdown != SHUTDOWN_MASK)) {
                sk->sk_state = SS_UNCONNECTED;
                sk->sk_err = ETIMEDOUT;
                sk->sk_error_report(sk);
        }
        release_sock(sk);

        sock_put(sk);
}

static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr,
                                int addr_len, int flags)
{
        int err;
        struct sock *sk;
        struct vsock_sock *vsk;
        struct sockaddr_vm *remote_addr;
        long timeout;
        DEFINE_WAIT(wait);

        err = 0;
        sk = sock->sk;
        vsk = vsock_sk(sk);

        lock_sock(sk);

        /* XXX AF_UNSPEC should make us disconnect like AF_INET. */
        switch (sock->state) {
        case SS_CONNECTED:
                err = -EISCONN;
                goto out;
        case SS_DISCONNECTING:
                err = -EINVAL;
                goto out;
        case SS_CONNECTING:
                /* This continues on so we can move sock into the SS_CONNECTED
                 * state once the connection has completed (at which point err
                 * will be set to zero also).  Otherwise, we will either wait
                 * for the connection or return -EALREADY should this be a
                 * non-blocking call.
                 */
                err = -EALREADY;
                break;
        default:
                if ((sk->sk_state == SS_LISTEN) ||
                    vsock_addr_cast(addr, addr_len, &remote_addr) != 0) {
                        err = -EINVAL;
                        goto out;
                }

                /* The hypervisor and well-known contexts do not have socket
                 * endpoints.
                 */
                if (!transport->stream_allow(remote_addr->svm_cid,
                                             remote_addr->svm_port)) {
                        err = -ENETUNREACH;
                        goto out;
                }

                /* Set the remote address that we are connecting to. */
                memcpy(&vsk->remote_addr, remote_addr,
                       sizeof(vsk->remote_addr));

                err = vsock_auto_bind(vsk);
                if (err)
                        goto out;

                sk->sk_state = SS_CONNECTING;

                err = transport->connect(vsk);
                if (err < 0)
                        goto out;

                /* Mark sock as connecting and set the error code to in
                 * progress in case this is a non-blocking connect.
                 */
                sock->state = SS_CONNECTING;
                err = -EINPROGRESS;
        }

        /* The receive path will handle all communication until we are able to
         * enter the connected state.  Here we wait for the connection to be
         * completed or a notification of an error.
         */
        timeout = vsk->connect_timeout;
        prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

        while (sk->sk_state != SS_CONNECTED && sk->sk_err == 0) {
                if (flags & O_NONBLOCK) {
                        /* If we're not going to block, we schedule a timeout
                         * function to generate a timeout on the connection
                         * attempt, in case the peer doesn't respond in a
                         * timely manner. We hold on to the socket until the
                         * timeout fires.
                         */
                        sock_hold(sk);
                        INIT_DELAYED_WORK(&vsk->dwork,
                                          vsock_connect_timeout);
                        schedule_delayed_work(&vsk->dwork, timeout);

                        /* Skip ahead to preserve error code set above. */
                        goto out_wait;
                }

                release_sock(sk);
                timeout = schedule_timeout(timeout);
                lock_sock(sk);

                if (signal_pending(current)) {
                        err = sock_intr_errno(timeout);
                        goto out_wait_error;
                } else if (timeout == 0) {
                        err = -ETIMEDOUT;
                        goto out_wait_error;
                }

                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
        }

        if (sk->sk_err) {
                err = -sk->sk_err;
                goto out_wait_error;
        } else
                err = 0;

out_wait:
        finish_wait(sk_sleep(sk), &wait);
out:
        release_sock(sk);
        return err;

out_wait_error:
        sk->sk_state = SS_UNCONNECTED;
        sock->state = SS_UNCONNECTED;
        goto out_wait;
}

static int vsock_accept(struct socket *sock, struct socket *newsock, int flags)
{
        struct sock *listener;
        int err;
        struct sock *connected;
        struct vsock_sock *vconnected;
        long timeout;
        DEFINE_WAIT(wait);

        err = 0;
        listener = sock->sk;

        lock_sock(listener);

        if (sock->type != SOCK_STREAM) {
                err = -EOPNOTSUPP;
                goto out;
        }

        if (listener->sk_state != SS_LISTEN) {
                err = -EINVAL;
                goto out;
        }

        /* Wait for children sockets to appear; these are the new sockets
         * created upon connection establishment.
         */
        timeout = sock_sndtimeo(listener, flags & O_NONBLOCK);
        prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);

        while ((connected = vsock_dequeue_accept(listener)) == NULL &&
               listener->sk_err == 0) {
                release_sock(listener);
                timeout = schedule_timeout(timeout);
                lock_sock(listener);

                if (signal_pending(current)) {
                        err = sock_intr_errno(timeout);
                        goto out_wait;
                } else if (timeout == 0) {
                        err = -EAGAIN;
                        goto out_wait;
                }

                prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);
        }

        if (listener->sk_err)
                err = -listener->sk_err;

        if (connected) {
                listener->sk_ack_backlog--;

                lock_sock(connected);
                vconnected = vsock_sk(connected);

                /* If the listener socket has received an error, then we should
                 * reject this socket and return.  Note that we simply mark the
                 * socket rejected, drop our reference, and let the cleanup
                 * function handle the cleanup; the fact that we found it in
                 * the listener's accept queue guarantees that the cleanup
                 * function hasn't run yet.
                 */
                if (err) {
                        vconnected->rejected = true;
                        release_sock(connected);
                        sock_put(connected);
                        goto out_wait;
                }

                newsock->state = SS_CONNECTED;
                sock_graft(connected, newsock);
                release_sock(connected);
                sock_put(connected);
        }

out_wait:
        finish_wait(sk_sleep(listener), &wait);
out:
        release_sock(listener);
        return err;
}

static int vsock_listen(struct socket *sock, int backlog)
{
        int err;
        struct sock *sk;
        struct vsock_sock *vsk;

        sk = sock->sk;

        lock_sock(sk);

        if (sock->type != SOCK_STREAM) {
                err = -EOPNOTSUPP;
                goto out;
        }

        if (sock->state != SS_UNCONNECTED) {
                err = -EINVAL;
                goto out;
        }

        vsk = vsock_sk(sk);

        if (!vsock_addr_bound(&vsk->local_addr)) {
                err = -EINVAL;
                goto out;
        }

        sk->sk_max_ack_backlog = backlog;
        sk->sk_state = SS_LISTEN;

        err = 0;

out:
        release_sock(sk);
        return err;
}

static int vsock_stream_setsockopt(struct socket *sock,
                                   int level,
                                   int optname,
                                   char __user *optval,
                                   unsigned int optlen)
{
        int err;
        struct sock *sk;
        struct vsock_sock *vsk;
        u64 val;

        if (level != AF_VSOCK)
                return -ENOPROTOOPT;

#define COPY_IN(_v)                                       \
        do {                                              \
                if (optlen < sizeof(_v)) {                \
                        err = -EINVAL;                    \
                        goto exit;                        \
                }                                         \
                if (copy_from_user(&_v, optval, sizeof(_v)) != 0) {     \
                        err = -EFAULT;                                  \
                        goto exit;                                      \
                }                                                       \
        } while (0)

        err = 0;
        sk = sock->sk;
        vsk = vsock_sk(sk);

        lock_sock(sk);

        switch (optname) {
        case SO_VM_SOCKETS_BUFFER_SIZE:
                COPY_IN(val);
                transport->set_buffer_size(vsk, val);
                break;

        case SO_VM_SOCKETS_BUFFER_MAX_SIZE:
                COPY_IN(val);
                transport->set_max_buffer_size(vsk, val);
                break;

        case SO_VM_SOCKETS_BUFFER_MIN_SIZE:
                COPY_IN(val);
                transport->set_min_buffer_size(vsk, val);
                break;

        case SO_VM_SOCKETS_CONNECT_TIMEOUT: {
                struct timeval tv;
                COPY_IN(tv);
                if (tv.tv_sec >= 0 && tv.tv_usec < USEC_PER_SEC &&
                    tv.tv_sec < (MAX_SCHEDULE_TIMEOUT / HZ - 1)) {
                        vsk->connect_timeout = tv.tv_sec * HZ +
                            DIV_ROUND_UP(tv.tv_usec, (1000000 / HZ));
                        if (vsk->connect_timeout == 0)
                                vsk->connect_timeout =
                                    VSOCK_DEFAULT_CONNECT_TIMEOUT;

                } else {
                        err = -ERANGE;
                }
                break;
        }

        default:
                err = -ENOPROTOOPT;
                break;
        }

#undef COPY_IN

exit:
        release_sock(sk);
        return err;
}

static int vsock_stream_getsockopt(struct socket *sock,
                                   int level, int optname,
                                   char __user *optval,
                                   int __user *optlen)
{
        int err;
        int len;
        struct sock *sk;
        struct vsock_sock *vsk;
        u64 val;

        if (level != AF_VSOCK)
                return -ENOPROTOOPT;

        err = get_user(len, optlen);
        if (err != 0)
                return err;

#define COPY_OUT(_v)                            \
        do {                                    \
                if (len < sizeof(_v))           \
                        return -EINVAL;         \
                                                \
                len = sizeof(_v);               \
                if (copy_to_user(optval, &_v, len) != 0)        \
                        return -EFAULT;                         \
                                                                \
        } while (0)

        err = 0;
        sk = sock->sk;
        vsk = vsock_sk(sk);

        switch (optname) {
        case SO_VM_SOCKETS_BUFFER_SIZE:
                val = transport->get_buffer_size(vsk);
                COPY_OUT(val);
                break;

        case SO_VM_SOCKETS_BUFFER_MAX_SIZE:
                val = transport->get_max_buffer_size(vsk);
                COPY_OUT(val);
                break;

        case SO_VM_SOCKETS_BUFFER_MIN_SIZE:
                val = transport->get_min_buffer_size(vsk);
                COPY_OUT(val);
                break;

        case SO_VM_SOCKETS_CONNECT_TIMEOUT: {
                struct timeval tv;
                tv.tv_sec = vsk->connect_timeout / HZ;
                tv.tv_usec =
                    (vsk->connect_timeout -
                     tv.tv_sec * HZ) * (1000000 / HZ);
                COPY_OUT(tv);
                break;
        }
        default:
                return -ENOPROTOOPT;
        }

        err = put_user(len, optlen);
        if (err != 0)
                return -EFAULT;

#undef COPY_OUT

        return 0;
}

static int vsock_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                                struct msghdr *msg, size_t len)
{
        struct sock *sk;
        struct vsock_sock *vsk;
        ssize_t total_written;
        long timeout;
        int err;
        struct vsock_transport_send_notify_data send_data;

        DEFINE_WAIT(wait);

        sk = sock->sk;
        vsk = vsock_sk(sk);
        total_written = 0;
        err = 0;

        if (msg->msg_flags & MSG_OOB)
                return -EOPNOTSUPP;

        lock_sock(sk);

        /* Callers should not provide a destination with stream sockets. */
        if (msg->msg_namelen) {
                err = sk->sk_state == SS_CONNECTED ? -EISCONN : -EOPNOTSUPP;
                goto out;
        }

        /* Send data only if both sides are not shutdown in the direction. */
        if (sk->sk_shutdown & SEND_SHUTDOWN ||
            vsk->peer_shutdown & RCV_SHUTDOWN) {
                err = -EPIPE;
                goto out;
        }

        if (sk->sk_state != SS_CONNECTED ||
            !vsock_addr_bound(&vsk->local_addr)) {
                err = -ENOTCONN;
                goto out;
        }

        if (!vsock_addr_bound(&vsk->remote_addr)) {
                err = -EDESTADDRREQ;
                goto out;
        }

        /* Wait for room in the produce queue to enqueue our user's data. */
        timeout = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);

        err = transport->notify_send_init(vsk, &send_data);
        if (err < 0)
                goto out;

        prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

        while (total_written < len) {
                ssize_t written;

                while (vsock_stream_has_space(vsk) == 0 &&
                       sk->sk_err == 0 &&
                       !(sk->sk_shutdown & SEND_SHUTDOWN) &&
                       !(vsk->peer_shutdown & RCV_SHUTDOWN)) {

                        /* Don't wait for non-blocking sockets. */
                        if (timeout == 0) {
                                err = -EAGAIN;
                                goto out_wait;
                        }

                        err = transport->notify_send_pre_block(vsk, &send_data);
                        if (err < 0)
                                goto out_wait;

                        release_sock(sk);
                        timeout = schedule_timeout(timeout);
                        lock_sock(sk);
                        if (signal_pending(current)) {
                                err = sock_intr_errno(timeout);
                                goto out_wait;
                        } else if (timeout == 0) {
                                err = -EAGAIN;
                                goto out_wait;
                        }

                        prepare_to_wait(sk_sleep(sk), &wait,
                                        TASK_INTERRUPTIBLE);
                }

                /* These checks occur both as part of and after the loop
                 * conditional since we need to check before and after
                 * sleeping.
                 */
                if (sk->sk_err) {
                        err = -sk->sk_err;
                        goto out_wait;
                } else if ((sk->sk_shutdown & SEND_SHUTDOWN) ||
                           (vsk->peer_shutdown & RCV_SHUTDOWN)) {
                        err = -EPIPE;
                        goto out_wait;
                }

                err = transport->notify_send_pre_enqueue(vsk, &send_data);
                if (err < 0)
                        goto out_wait;

                /* Note that enqueue will only write as many bytes as are free
                 * in the produce queue, so we don't need to ensure len is
                 * smaller than the queue size.  It is the caller's
                 * responsibility to check how many bytes we were able to send.
                 */

                written = transport->stream_enqueue(
                                vsk, msg->msg_iov,
                                len - total_written);
                if (written < 0) {
                        err = -ENOMEM;
                        goto out_wait;
                }

                total_written += written;

                err = transport->notify_send_post_enqueue(
                                vsk, written, &send_data);
                if (err < 0)
                        goto out_wait;

        }

out_wait:
        if (total_written > 0)
                err = total_written;
        finish_wait(sk_sleep(sk), &wait);
out:
        release_sock(sk);
        return err;
}


static int
vsock_stream_recvmsg(struct kiocb *kiocb,
                     struct socket *sock,
                     struct msghdr *msg, size_t len, int flags)
{
        struct sock *sk;
        struct vsock_sock *vsk;
        int err;
        size_t target;
        ssize_t copied;
        long timeout;
        struct vsock_transport_recv_notify_data recv_data;

        DEFINE_WAIT(wait);

        sk = sock->sk;
        vsk = vsock_sk(sk);
        err = 0;

        lock_sock(sk);

        if (sk->sk_state != SS_CONNECTED) {
                /* Recvmsg is supposed to return 0 if a peer performs an
                 * orderly shutdown. Differentiate between that case and when a
                 * peer has not connected or a local shutdown occured with the
                 * SOCK_DONE flag.
                 */
                if (sock_flag(sk, SOCK_DONE))
                        err = 0;
                else
                        err = -ENOTCONN;

                goto out;
        }

        if (flags & MSG_OOB) {
                err = -EOPNOTSUPP;
                goto out;
        }

        /* We don't check peer_shutdown flag here since peer may actually shut
         * down, but there can be data in the queue that a local socket can
         * receive.
         */
        if (sk->sk_shutdown & RCV_SHUTDOWN) {
                err = 0;
                goto out;
        }

        /* It is valid on Linux to pass in a zero-length receive buffer.  This
         * is not an error.  We may as well bail out now.
         */
        if (!len) {
                err = 0;
                goto out;
        }

        /* We must not copy less than target bytes into the user's buffer
         * before returning successfully, so we wait for the consume queue to
         * have that much data to consume before dequeueing.  Note that this
         * makes it impossible to handle cases where target is greater than the
         * queue size.
         */
        target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
        if (target >= transport->stream_rcvhiwat(vsk)) {
                err = -ENOMEM;
                goto out;
        }
        timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
        copied = 0;

        err = transport->notify_recv_init(vsk, target, &recv_data);
        if (err < 0)
                goto out;

        prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

        while (1) {
                s64 ready = vsock_stream_has_data(vsk);

                if (ready < 0) {
                        /* Invalid queue pair content. XXX This should be
                         * changed to a connection reset in a later change.
                         */

                        err = -ENOMEM;
                        goto out_wait;
                } else if (ready > 0) {
                        ssize_t read;

                        err = transport->notify_recv_pre_dequeue(
                                        vsk, target, &recv_data);
                        if (err < 0)
                                break;

                        read = transport->stream_dequeue(
                                        vsk, msg->msg_iov,
                                        len - copied, flags);
                        if (read < 0) {
                                err = -ENOMEM;
                                break;
                        }

                        copied += read;

                        err = transport->notify_recv_post_dequeue(
                                        vsk, target, read,
                                        !(flags & MSG_PEEK), &recv_data);
                        if (err < 0)
                                goto out_wait;

                        if (read >= target || flags & MSG_PEEK)
                                break;

                        target -= read;
                } else {
                        if (sk->sk_err != 0 || (sk->sk_shutdown & RCV_SHUTDOWN)
                            || (vsk->peer_shutdown & SEND_SHUTDOWN)) {
                                break;
                        }
                        /* Don't wait for non-blocking sockets. */
                        if (timeout == 0) {
                                err = -EAGAIN;
                                break;
                        }

                        err = transport->notify_recv_pre_block(
                                        vsk, target, &recv_data);
                        if (err < 0)
                                break;

                        release_sock(sk);
                        timeout = schedule_timeout(timeout);
                        lock_sock(sk);

                        if (signal_pending(current)) {
                                err = sock_intr_errno(timeout);
                                break;
                        } else if (timeout == 0) {
                                err = -EAGAIN;
                                break;
                        }

                        prepare_to_wait(sk_sleep(sk), &wait,
                                        TASK_INTERRUPTIBLE);
                }
        }

        if (sk->sk_err)
                err = -sk->sk_err;
        else if (sk->sk_shutdown & RCV_SHUTDOWN)
                err = 0;

        if (copied > 0) {
                /* We only do these additional bookkeeping/notification steps
                 * if we actually copied something out of the queue pair
                 * instead of just peeking ahead.
                 */

                if (!(flags & MSG_PEEK)) {
                        /* If the other side has shutdown for sending and there
                         * is nothing more to read, then modify the socket
                         * state.
                         */
                        if (vsk->peer_shutdown & SEND_SHUTDOWN) {
                                if (vsock_stream_has_data(vsk) <= 0) {
                                        sk->sk_state = SS_UNCONNECTED;
                                        sock_set_flag(sk, SOCK_DONE);
                                        sk->sk_state_change(sk);
                                }
                        }
                }
                err = copied;
        }

out_wait:
        finish_wait(sk_sleep(sk), &wait);
out:
        release_sock(sk);
        return err;
}

static const struct proto_ops vsock_stream_ops = {
        .family = PF_VSOCK,
        .owner = THIS_MODULE,
        .release = vsock_release,
        .bind = vsock_bind,
        .connect = vsock_stream_connect,
        .socketpair = sock_no_socketpair,
        .accept = vsock_accept,
        .getname = vsock_getname,
        .poll = vsock_poll,
        .ioctl = sock_no_ioctl,
        .listen = vsock_listen,
        .shutdown = vsock_shutdown,
        .setsockopt = vsock_stream_setsockopt,
        .getsockopt = vsock_stream_getsockopt,
        .sendmsg = vsock_stream_sendmsg,
        .recvmsg = vsock_stream_recvmsg,
        .mmap = sock_no_mmap,
        .sendpage = sock_no_sendpage,
};

static int vsock_create(struct net *net, struct socket *sock,
                        int protocol, int kern)
{
        if (!sock)
                return -EINVAL;

        if (protocol && protocol != PF_VSOCK)
                return -EPROTONOSUPPORT;

        switch (sock->type) {
        case SOCK_DGRAM:
                sock->ops = &vsock_dgram_ops;
                break;
        case SOCK_STREAM:
                sock->ops = &vsock_stream_ops;
                break;
        default:
                return -ESOCKTNOSUPPORT;
        }

        sock->state = SS_UNCONNECTED;

        return __vsock_create(net, sock, NULL, GFP_KERNEL, 0) ? 0 : -ENOMEM;
}

static const struct net_proto_family vsock_family_ops = {
        .family = AF_VSOCK,
        .create = vsock_create,
        .owner = THIS_MODULE,
};

static long vsock_dev_do_ioctl(struct file *filp,
                               unsigned int cmd, void __user *ptr)
{
        u32 __user *p = ptr;
        int retval = 0;

        switch (cmd) {
        case IOCTL_VM_SOCKETS_GET_LOCAL_CID:
                if (put_user(transport->get_local_cid(), p) != 0)
                        retval = -EFAULT;
                break;

        default:
                pr_err("Unknown ioctl %d\n", cmd);
                retval = -EINVAL;
        }

        return retval;
}

static long vsock_dev_ioctl(struct file *filp,
                            unsigned int cmd, unsigned long arg)
{
        return vsock_dev_do_ioctl(filp, cmd, (void __user *)arg);
}

#ifdef CONFIG_COMPAT
static long vsock_dev_compat_ioctl(struct file *filp,
                                   unsigned int cmd, unsigned long arg)
{
        return vsock_dev_do_ioctl(filp, cmd, compat_ptr(arg));
}
#endif

static const struct file_operations vsock_device_ops = {
        .owner          = THIS_MODULE,
        .unlocked_ioctl = vsock_dev_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = vsock_dev_compat_ioctl,
#endif
        .open           = nonseekable_open,
};

static struct miscdevice vsock_device = {
        .name           = "vsock",
        .fops           = &vsock_device_ops,
};

int __vsock_core_init(const struct vsock_transport *t, struct module *owner)
{
        int err = mutex_lock_interruptible(&vsock_register_mutex);

        if (err)
                return err;

        if (transport) {
                err = -EBUSY;
                goto err_busy;
        }

        /* Transport must be the owner of the protocol so that it can't
         * unload while there are open sockets.
         */
        vsock_proto.owner = owner;
        transport = t;

        vsock_init_tables();

        vsock_device.minor = MISC_DYNAMIC_MINOR;
        err = misc_register(&vsock_device);
        if (err) {
                pr_err("Failed to register misc device\n");
                return -ENOENT;
        }

        err = proto_register(&vsock_proto, 1);  /* we want our slab */
        if (err) {
                pr_err("Cannot register vsock protocol\n");
                goto err_misc_deregister;
        }

        err = sock_register(&vsock_family_ops);
        if (err) {
                pr_err("could not register af_vsock (%d) address family: %d\n",
                       AF_VSOCK, err);
                goto err_unregister_proto;
        }

        mutex_unlock(&vsock_register_mutex);
        return 0;

err_unregister_proto:
        proto_unregister(&vsock_proto);
err_misc_deregister:
        misc_deregister(&vsock_device);
        transport = NULL;
err_busy:
        mutex_unlock(&vsock_register_mutex);
        return err;
}
EXPORT_SYMBOL_GPL(__vsock_core_init);

void vsock_core_exit(void)
{
        mutex_lock(&vsock_register_mutex);

        misc_deregister(&vsock_device);
        sock_unregister(AF_VSOCK);
        proto_unregister(&vsock_proto);

        /* We do not want the assignment below re-ordered. */
        mb();
        transport = NULL;

        mutex_unlock(&vsock_register_mutex);
}
EXPORT_SYMBOL_GPL(vsock_core_exit);

MODULE_AUTHOR("VMware, Inc.");
MODULE_DESCRIPTION("VMware Virtual Socket Family");
MODULE_VERSION("1.0.1.0-k");

MODULE_LICENSE("GPL v2");