caif_socket.c

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/*
 * Copyright (C) ST-Ericsson AB 2010
 * Author:  Sjur Brendeland [email protected]
 * 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;
    int skb_len;
    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.
     */
    skb_len = skb->len;
    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, skb_len);
    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 kiocb *iocb, 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 (m->msg_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_iovec(skb, 0, m->msg_iov, 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);
        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 kiocb *iocb, 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;

    msg->msg_namelen = 0;

    /*
     * 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);
        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_toiovec(msg->msg_iov, 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 kiocb *kiocb, 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_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_fromiovec(skb_put(skb, len), msg->msg_iov, 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 kiocb *kiocb, 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_fromiovec(skb_put(skb, size), msg->msg_iov, 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));
    if (cf_sk->debugfs_socket_dir != NULL)
        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);