unix/caif: sk_socket can disappear when state is unlocked

[mirror_ubuntu-bionic-kernel.git] / net / caif / caif_socket.c

/*
 * Copyright (C) ST-Ericsson AB 2010
 * Author:      Sjur Brendeland
 * License terms: GNU General Public License (GPL) version 2
 */

#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/wait.h>
#include <linux/poll.h>
#include <linux/tcp.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/caif/caif_socket.h>
#include <linux/pkt_sched.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <net/caif/caif_layer.h>
#include <net/caif/caif_dev.h>
#include <net/caif/cfpkt.h>

MODULE_LICENSE("GPL");
MODULE_ALIAS_NETPROTO(AF_CAIF);

/*
 * CAIF state is re-using the TCP socket states.
 * caif_states stored in sk_state reflect the state as reported by
 * the CAIF stack, while sk_socket->state is the state of the socket.
 */
enum caif_states {
        CAIF_CONNECTED          = TCP_ESTABLISHED,
        CAIF_CONNECTING = TCP_SYN_SENT,
        CAIF_DISCONNECTED       = TCP_CLOSE
};

#define TX_FLOW_ON_BIT  1
#define RX_FLOW_ON_BIT  2

struct caifsock {
        struct sock sk; /* must be first member */
        struct cflayer layer;
        u32 flow_state;
        struct caif_connect_request conn_req;
        struct mutex readlock;
        struct dentry *debugfs_socket_dir;
        int headroom, tailroom, maxframe;
};

static int rx_flow_is_on(struct caifsock *cf_sk)
{
        return test_bit(RX_FLOW_ON_BIT,
                        (void *) &cf_sk->flow_state);
}

static int tx_flow_is_on(struct caifsock *cf_sk)
{
        return test_bit(TX_FLOW_ON_BIT,
                        (void *) &cf_sk->flow_state);
}

static void set_rx_flow_off(struct caifsock *cf_sk)
{
         clear_bit(RX_FLOW_ON_BIT,
                 (void *) &cf_sk->flow_state);
}

static void set_rx_flow_on(struct caifsock *cf_sk)
{
         set_bit(RX_FLOW_ON_BIT,
                        (void *) &cf_sk->flow_state);
}

static void set_tx_flow_off(struct caifsock *cf_sk)
{
         clear_bit(TX_FLOW_ON_BIT,
                (void *) &cf_sk->flow_state);
}

static void set_tx_flow_on(struct caifsock *cf_sk)
{
         set_bit(TX_FLOW_ON_BIT,
                (void *) &cf_sk->flow_state);
}

static void caif_read_lock(struct sock *sk)
{
        struct caifsock *cf_sk;
        cf_sk = container_of(sk, struct caifsock, sk);
        mutex_lock(&cf_sk->readlock);
}

static void caif_read_unlock(struct sock *sk)
{
        struct caifsock *cf_sk;
        cf_sk = container_of(sk, struct caifsock, sk);
        mutex_unlock(&cf_sk->readlock);
}

static int sk_rcvbuf_lowwater(struct caifsock *cf_sk)
{
        /* A quarter of full buffer is used a low water mark */
        return cf_sk->sk.sk_rcvbuf / 4;
}

static void caif_flow_ctrl(struct sock *sk, int mode)
{
        struct caifsock *cf_sk;
        cf_sk = container_of(sk, struct caifsock, sk);
        if (cf_sk->layer.dn && cf_sk->layer.dn->modemcmd)
                cf_sk->layer.dn->modemcmd(cf_sk->layer.dn, mode);
}

/*
 * Copied from sock.c:sock_queue_rcv_skb(), but changed so packets are
 * not dropped, but CAIF is sending flow off instead.
 */
static int caif_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{
        int err;
        unsigned long flags;
        struct sk_buff_head *list = &sk->sk_receive_queue;
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);

        if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=
                (unsigned int)sk->sk_rcvbuf && rx_flow_is_on(cf_sk)) {
                net_dbg_ratelimited("sending flow OFF (queue len = %d %d)\n",
                                    atomic_read(&cf_sk->sk.sk_rmem_alloc),
                                    sk_rcvbuf_lowwater(cf_sk));
                set_rx_flow_off(cf_sk);
                caif_flow_ctrl(sk, CAIF_MODEMCMD_FLOW_OFF_REQ);
        }

        err = sk_filter(sk, skb);
        if (err)
                return err;
        if (!sk_rmem_schedule(sk, skb, skb->truesize) && rx_flow_is_on(cf_sk)) {
                set_rx_flow_off(cf_sk);
                net_dbg_ratelimited("sending flow OFF due to rmem_schedule\n");
                caif_flow_ctrl(sk, CAIF_MODEMCMD_FLOW_OFF_REQ);
        }
        skb->dev = NULL;
        skb_set_owner_r(skb, sk);
        /* Cache the SKB length before we tack it onto the receive
         * queue. Once it is added it no longer belongs to us and
         * may be freed by other threads of control pulling packets
         * from the queue.
         */
        spin_lock_irqsave(&list->lock, flags);
        if (!sock_flag(sk, SOCK_DEAD))
                __skb_queue_tail(list, skb);
        spin_unlock_irqrestore(&list->lock, flags);

        if (!sock_flag(sk, SOCK_DEAD))
                sk->sk_data_ready(sk);
        else
                kfree_skb(skb);
        return 0;
}

/* Packet Receive Callback function called from CAIF Stack */
static int caif_sktrecv_cb(struct cflayer *layr, struct cfpkt *pkt)
{
        struct caifsock *cf_sk;
        struct sk_buff *skb;

        cf_sk = container_of(layr, struct caifsock, layer);
        skb = cfpkt_tonative(pkt);

        if (unlikely(cf_sk->sk.sk_state != CAIF_CONNECTED)) {
                kfree_skb(skb);
                return 0;
        }
        caif_queue_rcv_skb(&cf_sk->sk, skb);
        return 0;
}

static void cfsk_hold(struct cflayer *layr)
{
        struct caifsock *cf_sk = container_of(layr, struct caifsock, layer);
        sock_hold(&cf_sk->sk);
}

static void cfsk_put(struct cflayer *layr)
{
        struct caifsock *cf_sk = container_of(layr, struct caifsock, layer);
        sock_put(&cf_sk->sk);
}

/* Packet Control Callback function called from CAIF */
static void caif_ctrl_cb(struct cflayer *layr,
                         enum caif_ctrlcmd flow,
                         int phyid)
{
        struct caifsock *cf_sk = container_of(layr, struct caifsock, layer);
        switch (flow) {
        case CAIF_CTRLCMD_FLOW_ON_IND:
                /* OK from modem to start sending again */
                set_tx_flow_on(cf_sk);
                cf_sk->sk.sk_state_change(&cf_sk->sk);
                break;

        case CAIF_CTRLCMD_FLOW_OFF_IND:
                /* Modem asks us to shut up */
                set_tx_flow_off(cf_sk);
                cf_sk->sk.sk_state_change(&cf_sk->sk);
                break;

        case CAIF_CTRLCMD_INIT_RSP:
                /* We're now connected */
                caif_client_register_refcnt(&cf_sk->layer,
                                                cfsk_hold, cfsk_put);
                cf_sk->sk.sk_state = CAIF_CONNECTED;
                set_tx_flow_on(cf_sk);
                cf_sk->sk.sk_shutdown = 0;
                cf_sk->sk.sk_state_change(&cf_sk->sk);
                break;

        case CAIF_CTRLCMD_DEINIT_RSP:
                /* We're now disconnected */
                cf_sk->sk.sk_state = CAIF_DISCONNECTED;
                cf_sk->sk.sk_state_change(&cf_sk->sk);
                break;

        case CAIF_CTRLCMD_INIT_FAIL_RSP:
                /* Connect request failed */
                cf_sk->sk.sk_err = ECONNREFUSED;
                cf_sk->sk.sk_state = CAIF_DISCONNECTED;
                cf_sk->sk.sk_shutdown = SHUTDOWN_MASK;
                /*
                 * Socket "standards" seems to require POLLOUT to
                 * be set at connect failure.
                 */
                set_tx_flow_on(cf_sk);
                cf_sk->sk.sk_state_change(&cf_sk->sk);
                break;

        case CAIF_CTRLCMD_REMOTE_SHUTDOWN_IND:
                /* Modem has closed this connection, or device is down. */
                cf_sk->sk.sk_shutdown = SHUTDOWN_MASK;
                cf_sk->sk.sk_err = ECONNRESET;
                set_rx_flow_on(cf_sk);
                cf_sk->sk.sk_error_report(&cf_sk->sk);
                break;

        default:
                pr_debug("Unexpected flow command %d\n", flow);
        }
}

static void caif_check_flow_release(struct sock *sk)
{
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);

        if (rx_flow_is_on(cf_sk))
                return;

        if (atomic_read(&sk->sk_rmem_alloc) <= sk_rcvbuf_lowwater(cf_sk)) {
                        set_rx_flow_on(cf_sk);
                        caif_flow_ctrl(sk, CAIF_MODEMCMD_FLOW_ON_REQ);
        }
}

/*
 * Copied from unix_dgram_recvmsg, but removed credit checks,
 * changed locking, address handling and added MSG_TRUNC.
 */
static int caif_seqpkt_recvmsg(struct socket *sock, struct msghdr *m,
                               size_t len, int flags)

{
        struct sock *sk = sock->sk;
        struct sk_buff *skb;
        int ret;
        int copylen;

        ret = -EOPNOTSUPP;
        if (flags & MSG_OOB)
                goto read_error;

        skb = skb_recv_datagram(sk, flags, 0 , &ret);
        if (!skb)
                goto read_error;
        copylen = skb->len;
        if (len < copylen) {
                m->msg_flags |= MSG_TRUNC;
                copylen = len;
        }

        ret = skb_copy_datagram_msg(skb, 0, m, copylen);
        if (ret)
                goto out_free;

        ret = (flags & MSG_TRUNC) ? skb->len : copylen;
out_free:
        skb_free_datagram(sk, skb);
        caif_check_flow_release(sk);
        return ret;

read_error:
        return ret;
}


/* Copied from unix_stream_wait_data, identical except for lock call. */
static long caif_stream_data_wait(struct sock *sk, long timeo)
{
        DEFINE_WAIT(wait);
        lock_sock(sk);

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

                if (!skb_queue_empty(&sk->sk_receive_queue) ||
                        sk->sk_err ||
                        sk->sk_state != CAIF_CONNECTED ||
                        sock_flag(sk, SOCK_DEAD) ||
                        (sk->sk_shutdown & RCV_SHUTDOWN) ||
                        signal_pending(current) ||
                        !timeo)
                        break;

                set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
                release_sock(sk);
                timeo = schedule_timeout(timeo);
                lock_sock(sk);

                if (sock_flag(sk, SOCK_DEAD))
                        break;

                clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
        }

        finish_wait(sk_sleep(sk), &wait);
        release_sock(sk);
        return timeo;
}


/*
 * Copied from unix_stream_recvmsg, but removed credit checks,
 * changed locking calls, changed address handling.
 */
static int caif_stream_recvmsg(struct socket *sock, struct msghdr *msg,
                               size_t size, int flags)
{
        struct sock *sk = sock->sk;
        int copied = 0;
        int target;
        int err = 0;
        long timeo;

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

        /*
         * Lock the socket to prevent queue disordering
         * while sleeps in memcpy_tomsg
         */
        err = -EAGAIN;
        if (sk->sk_state == CAIF_CONNECTING)
                goto out;

        caif_read_lock(sk);
        target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);
        timeo = sock_rcvtimeo(sk, flags&MSG_DONTWAIT);

        do {
                int chunk;
                struct sk_buff *skb;

                lock_sock(sk);
                if (sock_flag(sk, SOCK_DEAD)) {
                        err = -ECONNRESET;
                        goto unlock;
                }
                skb = skb_dequeue(&sk->sk_receive_queue);
                caif_check_flow_release(sk);

                if (skb == NULL) {
                        if (copied >= target)
                                goto unlock;
                        /*
                         *      POSIX 1003.1g mandates this order.
                         */
                        err = sock_error(sk);
                        if (err)
                                goto unlock;
                        err = -ECONNRESET;
                        if (sk->sk_shutdown & RCV_SHUTDOWN)
                                goto unlock;

                        err = -EPIPE;
                        if (sk->sk_state != CAIF_CONNECTED)
                                goto unlock;
                        if (sock_flag(sk, SOCK_DEAD))
                                goto unlock;

                        release_sock(sk);

                        err = -EAGAIN;
                        if (!timeo)
                                break;

                        caif_read_unlock(sk);

                        timeo = caif_stream_data_wait(sk, timeo);

                        if (signal_pending(current)) {
                                err = sock_intr_errno(timeo);
                                goto out;
                        }
                        caif_read_lock(sk);
                        continue;
unlock:
                        release_sock(sk);
                        break;
                }
                release_sock(sk);
                chunk = min_t(unsigned int, skb->len, size);
                if (memcpy_to_msg(msg, skb->data, chunk)) {
                        skb_queue_head(&sk->sk_receive_queue, skb);
                        if (copied == 0)
                                copied = -EFAULT;
                        break;
                }
                copied += chunk;
                size -= chunk;

                /* Mark read part of skb as used */
                if (!(flags & MSG_PEEK)) {
                        skb_pull(skb, chunk);

                        /* put the skb back if we didn't use it up. */
                        if (skb->len) {
                                skb_queue_head(&sk->sk_receive_queue, skb);
                                break;
                        }
                        kfree_skb(skb);

                } else {
                        /*
                         * It is questionable, see note in unix_dgram_recvmsg.
                         */
                        /* put message back and return */
                        skb_queue_head(&sk->sk_receive_queue, skb);
                        break;
                }
        } while (size);
        caif_read_unlock(sk);

out:
        return copied ? : err;
}

/*
 * Copied from sock.c:sock_wait_for_wmem, but change to wait for
 * CAIF flow-on and sock_writable.
 */
static long caif_wait_for_flow_on(struct caifsock *cf_sk,
                                  int wait_writeable, long timeo, int *err)
{
        struct sock *sk = &cf_sk->sk;
        DEFINE_WAIT(wait);
        for (;;) {
                *err = 0;
                if (tx_flow_is_on(cf_sk) &&
                        (!wait_writeable || sock_writeable(&cf_sk->sk)))
                        break;
                *err = -ETIMEDOUT;
                if (!timeo)
                        break;
                *err = -ERESTARTSYS;
                if (signal_pending(current))
                        break;
                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
                *err = -ECONNRESET;
                if (sk->sk_shutdown & SHUTDOWN_MASK)
                        break;
                *err = -sk->sk_err;
                if (sk->sk_err)
                        break;
                *err = -EPIPE;
                if (cf_sk->sk.sk_state != CAIF_CONNECTED)
                        break;
                timeo = schedule_timeout(timeo);
        }
        finish_wait(sk_sleep(sk), &wait);
        return timeo;
}

/*
 * Transmit a SKB. The device may temporarily request re-transmission
 * by returning EAGAIN.
 */
static int transmit_skb(struct sk_buff *skb, struct caifsock *cf_sk,
                        int noblock, long timeo)
{
        struct cfpkt *pkt;

        pkt = cfpkt_fromnative(CAIF_DIR_OUT, skb);
        memset(skb->cb, 0, sizeof(struct caif_payload_info));
        cfpkt_set_prio(pkt, cf_sk->sk.sk_priority);

        if (cf_sk->layer.dn == NULL) {
                kfree_skb(skb);
                return -EINVAL;
        }

        return cf_sk->layer.dn->transmit(cf_sk->layer.dn, pkt);
}

/* Copied from af_unix:unix_dgram_sendmsg, and adapted to CAIF */
static int caif_seqpkt_sendmsg(struct socket *sock, struct msghdr *msg,
                               size_t len)
{
        struct sock *sk = sock->sk;
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);
        int buffer_size;
        int ret = 0;
        struct sk_buff *skb = NULL;
        int noblock;
        long timeo;
        caif_assert(cf_sk);
        ret = sock_error(sk);
        if (ret)
                goto err;

        ret = -EOPNOTSUPP;
        if (msg->msg_flags&MSG_OOB)
                goto err;

        ret = -EOPNOTSUPP;
        if (msg->msg_namelen)
                goto err;

        ret = -EINVAL;
        if (unlikely(msg->msg_iter.iov->iov_base == NULL))
                goto err;
        noblock = msg->msg_flags & MSG_DONTWAIT;

        timeo = sock_sndtimeo(sk, noblock);
        timeo = caif_wait_for_flow_on(container_of(sk, struct caifsock, sk),
                                1, timeo, &ret);

        if (ret)
                goto err;
        ret = -EPIPE;
        if (cf_sk->sk.sk_state != CAIF_CONNECTED ||
                sock_flag(sk, SOCK_DEAD) ||
                (sk->sk_shutdown & RCV_SHUTDOWN))
                goto err;

        /* Error if trying to write more than maximum frame size. */
        ret = -EMSGSIZE;
        if (len > cf_sk->maxframe && cf_sk->sk.sk_protocol != CAIFPROTO_RFM)
                goto err;

        buffer_size = len + cf_sk->headroom + cf_sk->tailroom;

        ret = -ENOMEM;
        skb = sock_alloc_send_skb(sk, buffer_size, noblock, &ret);

        if (!skb || skb_tailroom(skb) < buffer_size)
                goto err;

        skb_reserve(skb, cf_sk->headroom);

        ret = memcpy_from_msg(skb_put(skb, len), msg, len);

        if (ret)
                goto err;
        ret = transmit_skb(skb, cf_sk, noblock, timeo);
        if (ret < 0)
                /* skb is already freed */
                return ret;

        return len;
err:
        kfree_skb(skb);
        return ret;
}

/*
 * Copied from unix_stream_sendmsg and adapted to CAIF:
 * Changed removed permission handling and added waiting for flow on
 * and other minor adaptations.
 */
static int caif_stream_sendmsg(struct socket *sock, struct msghdr *msg,
                               size_t len)
{
        struct sock *sk = sock->sk;
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);
        int err, size;
        struct sk_buff *skb;
        int sent = 0;
        long timeo;

        err = -EOPNOTSUPP;
        if (unlikely(msg->msg_flags&MSG_OOB))
                goto out_err;

        if (unlikely(msg->msg_namelen))
                goto out_err;

        timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
        timeo = caif_wait_for_flow_on(cf_sk, 1, timeo, &err);

        if (unlikely(sk->sk_shutdown & SEND_SHUTDOWN))
                goto pipe_err;

        while (sent < len) {

                size = len-sent;

                if (size > cf_sk->maxframe)
                        size = cf_sk->maxframe;

                /* If size is more than half of sndbuf, chop up message */
                if (size > ((sk->sk_sndbuf >> 1) - 64))
                        size = (sk->sk_sndbuf >> 1) - 64;

                if (size > SKB_MAX_ALLOC)
                        size = SKB_MAX_ALLOC;

                skb = sock_alloc_send_skb(sk,
                                        size + cf_sk->headroom +
                                        cf_sk->tailroom,
                                        msg->msg_flags&MSG_DONTWAIT,
                                        &err);
                if (skb == NULL)
                        goto out_err;

                skb_reserve(skb, cf_sk->headroom);
                /*
                 *      If you pass two values to the sock_alloc_send_skb
                 *      it tries to grab the large buffer with GFP_NOFS
                 *      (which can fail easily), and if it fails grab the
                 *      fallback size buffer which is under a page and will
                 *      succeed. [Alan]
                 */
                size = min_t(int, size, skb_tailroom(skb));

                err = memcpy_from_msg(skb_put(skb, size), msg, size);
                if (err) {
                        kfree_skb(skb);
                        goto out_err;
                }
                err = transmit_skb(skb, cf_sk,
                                msg->msg_flags&MSG_DONTWAIT, timeo);
                if (err < 0)
                        /* skb is already freed */
                        goto pipe_err;

                sent += size;
        }

        return sent;

pipe_err:
        if (sent == 0 && !(msg->msg_flags&MSG_NOSIGNAL))
                send_sig(SIGPIPE, current, 0);
        err = -EPIPE;
out_err:
        return sent ? : err;
}

static int setsockopt(struct socket *sock,
                      int lvl, int opt, char __user *ov, unsigned int ol)
{
        struct sock *sk = sock->sk;
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);
        int linksel;

        if (cf_sk->sk.sk_socket->state != SS_UNCONNECTED)
                return -ENOPROTOOPT;

        switch (opt) {
        case CAIFSO_LINK_SELECT:
                if (ol < sizeof(int))
                        return -EINVAL;
                if (lvl != SOL_CAIF)
                        goto bad_sol;
                if (copy_from_user(&linksel, ov, sizeof(int)))
                        return -EINVAL;
                lock_sock(&(cf_sk->sk));
                cf_sk->conn_req.link_selector = linksel;
                release_sock(&cf_sk->sk);
                return 0;

        case CAIFSO_REQ_PARAM:
                if (lvl != SOL_CAIF)
                        goto bad_sol;
                if (cf_sk->sk.sk_protocol != CAIFPROTO_UTIL)
                        return -ENOPROTOOPT;
                lock_sock(&(cf_sk->sk));
                if (ol > sizeof(cf_sk->conn_req.param.data) ||
                        copy_from_user(&cf_sk->conn_req.param.data, ov, ol)) {
                        release_sock(&cf_sk->sk);
                        return -EINVAL;
                }
                cf_sk->conn_req.param.size = ol;
                release_sock(&cf_sk->sk);
                return 0;

        default:
                return -ENOPROTOOPT;
        }

        return 0;
bad_sol:
        return -ENOPROTOOPT;

}

/*
 * caif_connect() - Connect a CAIF Socket
 * Copied and modified af_irda.c:irda_connect().
 *
 * Note : by consulting "errno", the user space caller may learn the cause
 * of the failure. Most of them are visible in the function, others may come
 * from subroutines called and are listed here :
 *  o -EAFNOSUPPORT: bad socket family or type.
 *  o -ESOCKTNOSUPPORT: bad socket type or protocol
 *  o -EINVAL: bad socket address, or CAIF link type
 *  o -ECONNREFUSED: remote end refused the connection.
 *  o -EINPROGRESS: connect request sent but timed out (or non-blocking)
 *  o -EISCONN: already connected.
 *  o -ETIMEDOUT: Connection timed out (send timeout)
 *  o -ENODEV: No link layer to send request
 *  o -ECONNRESET: Received Shutdown indication or lost link layer
 *  o -ENOMEM: Out of memory
 *
 *  State Strategy:
 *  o sk_state: holds the CAIF_* protocol state, it's updated by
 *      caif_ctrl_cb.
 *  o sock->state: holds the SS_* socket state and is updated by connect and
 *      disconnect.
 */
static int caif_connect(struct socket *sock, struct sockaddr *uaddr,
                        int addr_len, int flags)
{
        struct sock *sk = sock->sk;
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);
        long timeo;
        int err;
        int ifindex, headroom, tailroom;
        unsigned int mtu;
        struct net_device *dev;

        lock_sock(sk);

        err = -EAFNOSUPPORT;
        if (uaddr->sa_family != AF_CAIF)
                goto out;

        switch (sock->state) {
        case SS_UNCONNECTED:
                /* Normal case, a fresh connect */
                caif_assert(sk->sk_state == CAIF_DISCONNECTED);
                break;
        case SS_CONNECTING:
                switch (sk->sk_state) {
                case CAIF_CONNECTED:
                        sock->state = SS_CONNECTED;
                        err = -EISCONN;
                        goto out;
                case CAIF_DISCONNECTED:
                        /* Reconnect allowed */
                        break;
                case CAIF_CONNECTING:
                        err = -EALREADY;
                        if (flags & O_NONBLOCK)
                                goto out;
                        goto wait_connect;
                }
                break;
        case SS_CONNECTED:
                caif_assert(sk->sk_state == CAIF_CONNECTED ||
                                sk->sk_state == CAIF_DISCONNECTED);
                if (sk->sk_shutdown & SHUTDOWN_MASK) {
                        /* Allow re-connect after SHUTDOWN_IND */
                        caif_disconnect_client(sock_net(sk), &cf_sk->layer);
                        caif_free_client(&cf_sk->layer);
                        break;
                }
                /* No reconnect on a seqpacket socket */
                err = -EISCONN;
                goto out;
        case SS_DISCONNECTING:
        case SS_FREE:
                caif_assert(1); /*Should never happen */
                break;
        }
        sk->sk_state = CAIF_DISCONNECTED;
        sock->state = SS_UNCONNECTED;
        sk_stream_kill_queues(&cf_sk->sk);

        err = -EINVAL;
        if (addr_len != sizeof(struct sockaddr_caif))
                goto out;

        memcpy(&cf_sk->conn_req.sockaddr, uaddr,
                sizeof(struct sockaddr_caif));

        /* Move to connecting socket, start sending Connect Requests */
        sock->state = SS_CONNECTING;
        sk->sk_state = CAIF_CONNECTING;

        /* Check priority value comming from socket */
        /* if priority value is out of range it will be ajusted */
        if (cf_sk->sk.sk_priority > CAIF_PRIO_MAX)
                cf_sk->conn_req.priority = CAIF_PRIO_MAX;
        else if (cf_sk->sk.sk_priority < CAIF_PRIO_MIN)
                cf_sk->conn_req.priority = CAIF_PRIO_MIN;
        else
                cf_sk->conn_req.priority = cf_sk->sk.sk_priority;

        /*ifindex = id of the interface.*/
        cf_sk->conn_req.ifindex = cf_sk->sk.sk_bound_dev_if;

        cf_sk->layer.receive = caif_sktrecv_cb;

        err = caif_connect_client(sock_net(sk), &cf_sk->conn_req,
                                &cf_sk->layer, &ifindex, &headroom, &tailroom);

        if (err < 0) {
                cf_sk->sk.sk_socket->state = SS_UNCONNECTED;
                cf_sk->sk.sk_state = CAIF_DISCONNECTED;
                goto out;
        }

        err = -ENODEV;
        rcu_read_lock();
        dev = dev_get_by_index_rcu(sock_net(sk), ifindex);
        if (!dev) {
                rcu_read_unlock();
                goto out;
        }
        cf_sk->headroom = LL_RESERVED_SPACE_EXTRA(dev, headroom);
        mtu = dev->mtu;
        rcu_read_unlock();

        cf_sk->tailroom = tailroom;
        cf_sk->maxframe = mtu - (headroom + tailroom);
        if (cf_sk->maxframe < 1) {
                pr_warn("CAIF Interface MTU too small (%d)\n", dev->mtu);
                err = -ENODEV;
                goto out;
        }

        err = -EINPROGRESS;
wait_connect:

        if (sk->sk_state != CAIF_CONNECTED && (flags & O_NONBLOCK))
                goto out;

        timeo = sock_sndtimeo(sk, flags & O_NONBLOCK);

        release_sock(sk);
        err = -ERESTARTSYS;
        timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
                        sk->sk_state != CAIF_CONNECTING,
                        timeo);
        lock_sock(sk);
        if (timeo < 0)
                goto out; /* -ERESTARTSYS */

        err = -ETIMEDOUT;
        if (timeo == 0 && sk->sk_state != CAIF_CONNECTED)
                goto out;
        if (sk->sk_state != CAIF_CONNECTED) {
                sock->state = SS_UNCONNECTED;
                err = sock_error(sk);
                if (!err)
                        err = -ECONNREFUSED;
                goto out;
        }
        sock->state = SS_CONNECTED;
        err = 0;
out:
        release_sock(sk);
        return err;
}

/*
 * caif_release() - Disconnect a CAIF Socket
 * Copied and modified af_irda.c:irda_release().
 */
static int caif_release(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);

        if (!sk)
                return 0;

        set_tx_flow_off(cf_sk);

        /*
         * Ensure that packets are not queued after this point in time.
         * caif_queue_rcv_skb checks SOCK_DEAD holding the queue lock,
         * this ensures no packets when sock is dead.
         */
        spin_lock_bh(&sk->sk_receive_queue.lock);
        sock_set_flag(sk, SOCK_DEAD);
        spin_unlock_bh(&sk->sk_receive_queue.lock);
        sock->sk = NULL;

        WARN_ON(IS_ERR(cf_sk->debugfs_socket_dir));
        debugfs_remove_recursive(cf_sk->debugfs_socket_dir);

        lock_sock(&(cf_sk->sk));
        sk->sk_state = CAIF_DISCONNECTED;
        sk->sk_shutdown = SHUTDOWN_MASK;

        caif_disconnect_client(sock_net(sk), &cf_sk->layer);
        cf_sk->sk.sk_socket->state = SS_DISCONNECTING;
        wake_up_interruptible_poll(sk_sleep(sk), POLLERR|POLLHUP);

        sock_orphan(sk);
        sk_stream_kill_queues(&cf_sk->sk);
        release_sock(sk);
        sock_put(sk);
        return 0;
}

/* Copied from af_unix.c:unix_poll(), added CAIF tx_flow handling */
static unsigned int caif_poll(struct file *file,
                              struct socket *sock, poll_table *wait)
{
        struct sock *sk = sock->sk;
        unsigned int mask;
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);

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

        /* exceptional events? */
        if (sk->sk_err)
                mask |= POLLERR;
        if (sk->sk_shutdown == SHUTDOWN_MASK)
                mask |= POLLHUP;
        if (sk->sk_shutdown & RCV_SHUTDOWN)
                mask |= POLLRDHUP;

        /* readable? */
        if (!skb_queue_empty(&sk->sk_receive_queue) ||
                (sk->sk_shutdown & RCV_SHUTDOWN))
                mask |= POLLIN | POLLRDNORM;

        /*
         * we set writable also when the other side has shut down the
         * connection. This prevents stuck sockets.
         */
        if (sock_writeable(sk) && tx_flow_is_on(cf_sk))
                mask |= POLLOUT | POLLWRNORM | POLLWRBAND;

        return mask;
}

static const struct proto_ops caif_seqpacket_ops = {
        .family = PF_CAIF,
        .owner = THIS_MODULE,
        .release = caif_release,
        .bind = sock_no_bind,
        .connect = caif_connect,
        .socketpair = sock_no_socketpair,
        .accept = sock_no_accept,
        .getname = sock_no_getname,
        .poll = caif_poll,
        .ioctl = sock_no_ioctl,
        .listen = sock_no_listen,
        .shutdown = sock_no_shutdown,
        .setsockopt = setsockopt,
        .getsockopt = sock_no_getsockopt,
        .sendmsg = caif_seqpkt_sendmsg,
        .recvmsg = caif_seqpkt_recvmsg,
        .mmap = sock_no_mmap,
        .sendpage = sock_no_sendpage,
};

static const struct proto_ops caif_stream_ops = {
        .family = PF_CAIF,
        .owner = THIS_MODULE,
        .release = caif_release,
        .bind = sock_no_bind,
        .connect = caif_connect,
        .socketpair = sock_no_socketpair,
        .accept = sock_no_accept,
        .getname = sock_no_getname,
        .poll = caif_poll,
        .ioctl = sock_no_ioctl,
        .listen = sock_no_listen,
        .shutdown = sock_no_shutdown,
        .setsockopt = setsockopt,
        .getsockopt = sock_no_getsockopt,
        .sendmsg = caif_stream_sendmsg,
        .recvmsg = caif_stream_recvmsg,
        .mmap = sock_no_mmap,
        .sendpage = sock_no_sendpage,
};

/* This function is called when a socket is finally destroyed. */
static void caif_sock_destructor(struct sock *sk)
{
        struct caifsock *cf_sk = container_of(sk, struct caifsock, sk);
        caif_assert(!atomic_read(&sk->sk_wmem_alloc));
        caif_assert(sk_unhashed(sk));
        caif_assert(!sk->sk_socket);
        if (!sock_flag(sk, SOCK_DEAD)) {
                pr_debug("Attempt to release alive CAIF socket: %p\n", sk);
                return;
        }
        sk_stream_kill_queues(&cf_sk->sk);
        caif_free_client(&cf_sk->layer);
}

static int caif_create(struct net *net, struct socket *sock, int protocol,
                       int kern)
{
        struct sock *sk = NULL;
        struct caifsock *cf_sk = NULL;
        static struct proto prot = {.name = "PF_CAIF",
                .owner = THIS_MODULE,
                .obj_size = sizeof(struct caifsock),
        };

        if (!capable(CAP_SYS_ADMIN) && !capable(CAP_NET_ADMIN))
                return -EPERM;
        /*
         * The sock->type specifies the socket type to use.
         * The CAIF socket is a packet stream in the sense
         * that it is packet based. CAIF trusts the reliability
         * of the link, no resending is implemented.
         */
        if (sock->type == SOCK_SEQPACKET)
                sock->ops = &caif_seqpacket_ops;
        else if (sock->type == SOCK_STREAM)
                sock->ops = &caif_stream_ops;
        else
                return -ESOCKTNOSUPPORT;

        if (protocol < 0 || protocol >= CAIFPROTO_MAX)
                return -EPROTONOSUPPORT;
        /*
         * Set the socket state to unconnected.  The socket state
         * is really not used at all in the net/core or socket.c but the
         * initialization makes sure that sock->state is not uninitialized.
         */
        sk = sk_alloc(net, PF_CAIF, GFP_KERNEL, &prot);
        if (!sk)
                return -ENOMEM;

        cf_sk = container_of(sk, struct caifsock, sk);

        /* Store the protocol */
        sk->sk_protocol = (unsigned char) protocol;

        /* Initialize default priority for well-known cases */
        switch (protocol) {
        case CAIFPROTO_AT:
                sk->sk_priority = TC_PRIO_CONTROL;
                break;
        case CAIFPROTO_RFM:
                sk->sk_priority = TC_PRIO_INTERACTIVE_BULK;
                break;
        default:
                sk->sk_priority = TC_PRIO_BESTEFFORT;
        }

        /*
         * Lock in order to try to stop someone from opening the socket
         * too early.
         */
        lock_sock(&(cf_sk->sk));

        /* Initialize the nozero default sock structure data. */
        sock_init_data(sock, sk);
        sk->sk_destruct = caif_sock_destructor;

        mutex_init(&cf_sk->readlock); /* single task reading lock */
        cf_sk->layer.ctrlcmd = caif_ctrl_cb;
        cf_sk->sk.sk_socket->state = SS_UNCONNECTED;
        cf_sk->sk.sk_state = CAIF_DISCONNECTED;

        set_tx_flow_off(cf_sk);
        set_rx_flow_on(cf_sk);

        /* Set default options on configuration */
        cf_sk->conn_req.link_selector = CAIF_LINK_LOW_LATENCY;
        cf_sk->conn_req.protocol = protocol;
        release_sock(&cf_sk->sk);
        return 0;
}


static struct net_proto_family caif_family_ops = {
        .family = PF_CAIF,
        .create = caif_create,
        .owner = THIS_MODULE,
};

static int __init caif_sktinit_module(void)
{
        int err = sock_register(&caif_family_ops);
        if (!err)
                return err;
        return 0;
}

static void __exit caif_sktexit_module(void)
{
        sock_unregister(PF_CAIF);
}
module_init(caif_sktinit_module);
module_exit(caif_sktexit_module);