socket.c

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/*
 * net/tipc/socket.c: TIPC socket API
 *
 * Copyright (c) 2001-2007, Ericsson AB
 * Copyright (c) 2004-2008, 2010-2011, Wind River Systems
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the names of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "core.h"
#include "port.h"

#include <linux/export.h>
#include <net/sock.h>

#define SS_LISTENING    -1  /* socket is listening */
#define SS_READY    -2  /* socket is connectionless */

#define OVERLOAD_LIMIT_BASE 5000
#define CONN_TIMEOUT_DEFAULT    8000    /* default connect timeout = 8s */

struct tipc_sock {
    struct sock sk;
    struct tipc_port *p;
    struct tipc_portid peer_name;
    unsigned int conn_timeout;
};

#define tipc_sk(sk) ((struct tipc_sock *)(sk))
#define tipc_sk_port(sk) (tipc_sk(sk)->p)

#define tipc_rx_ready(sock) (!skb_queue_empty(&sock->sk->sk_receive_queue) || \
            (sock->state == SS_DISCONNECTING))

static int backlog_rcv(struct sock *sk, struct sk_buff *skb);
static u32 dispatch(struct tipc_port *tport, struct sk_buff *buf);
static void wakeupdispatch(struct tipc_port *tport);

static const struct proto_ops packet_ops;
static const struct proto_ops stream_ops;
static const struct proto_ops msg_ops;

static struct proto tipc_proto;

static int sockets_enabled;

static atomic_t tipc_queue_size = ATOMIC_INIT(0);

/*
 * Revised TIPC socket locking policy:
 *
 * Most socket operations take the standard socket lock when they start
 * and hold it until they finish (or until they need to sleep).  Acquiring
 * this lock grants the owner exclusive access to the fields of the socket
 * data structures, with the exception of the backlog queue.  A few socket
 * operations can be done without taking the socket lock because they only
 * read socket information that never changes during the life of the socket.
 *
 * Socket operations may acquire the lock for the associated TIPC port if they
 * need to perform an operation on the port.  If any routine needs to acquire
 * both the socket lock and the port lock it must take the socket lock first
 * to avoid the risk of deadlock.
 *
 * The dispatcher handling incoming messages cannot grab the socket lock in
 * the standard fashion, since invoked it runs at the BH level and cannot block.
 * Instead, it checks to see if the socket lock is currently owned by someone,
 * and either handles the message itself or adds it to the socket's backlog
 * queue; in the latter case the queued message is processed once the process
 * owning the socket lock releases it.
 *
 * NOTE: Releasing the socket lock while an operation is sleeping overcomes
 * the problem of a blocked socket operation preventing any other operations
 * from occurring.  However, applications must be careful if they have
 * multiple threads trying to send (or receive) on the same socket, as these
 * operations might interfere with each other.  For example, doing a connect
 * and a receive at the same time might allow the receive to consume the
 * ACK message meant for the connect.  While additional work could be done
 * to try and overcome this, it doesn't seem to be worthwhile at the present.
 *
 * NOTE: Releasing the socket lock while an operation is sleeping also ensures
 * that another operation that must be performed in a non-blocking manner is
 * not delayed for very long because the lock has already been taken.
 *
 * NOTE: This code assumes that certain fields of a port/socket pair are
 * constant over its lifetime; such fields can be examined without taking
 * the socket lock and/or port lock, and do not need to be re-read even
 * after resuming processing after waiting.  These fields include:
 *   - socket type
 *   - pointer to socket sk structure (aka tipc_sock structure)
 *   - pointer to port structure
 *   - port reference
 */

static void advance_rx_queue(struct sock *sk)
{
    kfree_skb(__skb_dequeue(&sk->sk_receive_queue));
    atomic_dec(&tipc_queue_size);
}

static void discard_rx_queue(struct sock *sk)
{
    struct sk_buff *buf;

    while ((buf = __skb_dequeue(&sk->sk_receive_queue))) {
        atomic_dec(&tipc_queue_size);
        kfree_skb(buf);
    }
}

static void reject_rx_queue(struct sock *sk)
{
    struct sk_buff *buf;

    while ((buf = __skb_dequeue(&sk->sk_receive_queue))) {
        tipc_reject_msg(buf, TIPC_ERR_NO_PORT);
        atomic_dec(&tipc_queue_size);
    }
}

static int tipc_create(struct net *net, struct socket *sock, int protocol,
               int kern)
{
    const struct proto_ops *ops;
    socket_state state;
    struct sock *sk;
    struct tipc_port *tp_ptr;

    /* Validate arguments */
    if (unlikely(protocol != 0))
        return -EPROTONOSUPPORT;

    switch (sock->type) {
    case SOCK_STREAM:
        ops = &stream_ops;
        state = SS_UNCONNECTED;
        break;
    case SOCK_SEQPACKET:
        ops = &packet_ops;
        state = SS_UNCONNECTED;
        break;
    case SOCK_DGRAM:
    case SOCK_RDM:
        ops = &msg_ops;
        state = SS_READY;
        break;
    default:
        return -EPROTOTYPE;
    }

    /* Allocate socket's protocol area */
    sk = sk_alloc(net, AF_TIPC, GFP_KERNEL, &tipc_proto);
    if (sk == NULL)
        return -ENOMEM;

    /* Allocate TIPC port for socket to use */
    tp_ptr = tipc_createport_raw(sk, &dispatch, &wakeupdispatch,
                     TIPC_LOW_IMPORTANCE);
    if (unlikely(!tp_ptr)) {
        sk_free(sk);
        return -ENOMEM;
    }

    /* Finish initializing socket data structures */
    sock->ops = ops;
    sock->state = state;

    sock_init_data(sock, sk);
    sk->sk_backlog_rcv = backlog_rcv;
    sk->sk_rcvbuf = TIPC_FLOW_CONTROL_WIN * 2 * TIPC_MAX_USER_MSG_SIZE * 2;
    tipc_sk(sk)->p = tp_ptr;
    tipc_sk(sk)->conn_timeout = CONN_TIMEOUT_DEFAULT;

    spin_unlock_bh(tp_ptr->lock);

    if (sock->state == SS_READY) {
        tipc_set_portunreturnable(tp_ptr->ref, 1);
        if (sock->type == SOCK_DGRAM)
            tipc_set_portunreliable(tp_ptr->ref, 1);
    }

    return 0;
}

static int release(struct socket *sock)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport;
    struct sk_buff *buf;
    int res;

    /*
     * Exit if socket isn't fully initialized (occurs when a failed accept()
     * releases a pre-allocated child socket that was never used)
     */
    if (sk == NULL)
        return 0;

    tport = tipc_sk_port(sk);
    lock_sock(sk);

    /*
     * Reject all unreceived messages, except on an active connection
     * (which disconnects locally & sends a 'FIN+' to peer)
     */
    while (sock->state != SS_DISCONNECTING) {
        buf = __skb_dequeue(&sk->sk_receive_queue);
        if (buf == NULL)
            break;
        atomic_dec(&tipc_queue_size);
        if (TIPC_SKB_CB(buf)->handle != 0)
            kfree_skb(buf);
        else {
            if ((sock->state == SS_CONNECTING) ||
                (sock->state == SS_CONNECTED)) {
                sock->state = SS_DISCONNECTING;
                tipc_disconnect(tport->ref);
            }
            tipc_reject_msg(buf, TIPC_ERR_NO_PORT);
        }
    }

    /*
     * Delete TIPC port; this ensures no more messages are queued
     * (also disconnects an active connection & sends a 'FIN-' to peer)
     */
    res = tipc_deleteport(tport->ref);

    /* Discard any remaining (connection-based) messages in receive queue */
    discard_rx_queue(sk);

    /* Reject any messages that accumulated in backlog queue */
    sock->state = SS_DISCONNECTING;
    release_sock(sk);

    sock_put(sk);
    sock->sk = NULL;

    return res;
}

static int bind(struct socket *sock, struct sockaddr *uaddr, int uaddr_len)
{
    struct sockaddr_tipc *addr = (struct sockaddr_tipc *)uaddr;
    u32 portref = tipc_sk_port(sock->sk)->ref;

    if (unlikely(!uaddr_len))
        return tipc_withdraw(portref, 0, NULL);

    if (uaddr_len < sizeof(struct sockaddr_tipc))
        return -EINVAL;
    if (addr->family != AF_TIPC)
        return -EAFNOSUPPORT;

    if (addr->addrtype == TIPC_ADDR_NAME)
        addr->addr.nameseq.upper = addr->addr.nameseq.lower;
    else if (addr->addrtype != TIPC_ADDR_NAMESEQ)
        return -EAFNOSUPPORT;

    if (addr->addr.nameseq.type < TIPC_RESERVED_TYPES)
        return -EACCES;

    return (addr->scope > 0) ?
        tipc_publish(portref, addr->scope, &addr->addr.nameseq) :
        tipc_withdraw(portref, -addr->scope, &addr->addr.nameseq);
}

static int get_name(struct socket *sock, struct sockaddr *uaddr,
            int *uaddr_len, int peer)
{
    struct sockaddr_tipc *addr = (struct sockaddr_tipc *)uaddr;
    struct tipc_sock *tsock = tipc_sk(sock->sk);

    memset(addr, 0, sizeof(*addr));
    if (peer) {
        if ((sock->state != SS_CONNECTED) &&
            ((peer != 2) || (sock->state != SS_DISCONNECTING)))
            return -ENOTCONN;
        addr->addr.id.ref = tsock->peer_name.ref;
        addr->addr.id.node = tsock->peer_name.node;
    } else {
        addr->addr.id.ref = tsock->p->ref;
        addr->addr.id.node = tipc_own_addr;
    }

    *uaddr_len = sizeof(*addr);
    addr->addrtype = TIPC_ADDR_ID;
    addr->family = AF_TIPC;
    addr->scope = 0;
    addr->addr.name.domain = 0;

    return 0;
}

static unsigned int poll(struct file *file, struct socket *sock,
             poll_table *wait)
{
    struct sock *sk = sock->sk;
    u32 mask = 0;

    poll_wait(file, sk_sleep(sk), wait);

    switch ((int)sock->state) {
    case SS_READY:
    case SS_CONNECTED:
        if (!tipc_sk_port(sk)->congested)
            mask |= POLLOUT;
        /* fall thru' */
    case SS_CONNECTING:
    case SS_LISTENING:
        if (!skb_queue_empty(&sk->sk_receive_queue))
            mask |= (POLLIN | POLLRDNORM);
        break;
    case SS_DISCONNECTING:
        mask = (POLLIN | POLLRDNORM | POLLHUP);
        break;
    }

    return mask;
}

static int dest_name_check(struct sockaddr_tipc *dest, struct msghdr *m)
{
    struct tipc_cfg_msg_hdr hdr;

    if (likely(dest->addr.name.name.type >= TIPC_RESERVED_TYPES))
        return 0;
    if (likely(dest->addr.name.name.type == TIPC_TOP_SRV))
        return 0;
    if (likely(dest->addr.name.name.type != TIPC_CFG_SRV))
        return -EACCES;

    if (!m->msg_iovlen || (m->msg_iov[0].iov_len < sizeof(hdr)))
        return -EMSGSIZE;
    if (copy_from_user(&hdr, m->msg_iov[0].iov_base, sizeof(hdr)))
        return -EFAULT;
    if ((ntohs(hdr.tcm_type) & 0xC000) && (!capable(CAP_NET_ADMIN)))
        return -EACCES;

    return 0;
}

static int send_msg(struct kiocb *iocb, struct socket *sock,
            struct msghdr *m, size_t total_len)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    struct sockaddr_tipc *dest = (struct sockaddr_tipc *)m->msg_name;
    int needs_conn;
    long timeout_val;
    int res = -EINVAL;

    if (unlikely(!dest))
        return -EDESTADDRREQ;
    if (unlikely((m->msg_namelen < sizeof(*dest)) ||
             (dest->family != AF_TIPC)))
        return -EINVAL;
    if ((total_len > TIPC_MAX_USER_MSG_SIZE) ||
        (m->msg_iovlen > (unsigned int)INT_MAX))
        return -EMSGSIZE;

    if (iocb)
        lock_sock(sk);

    needs_conn = (sock->state != SS_READY);
    if (unlikely(needs_conn)) {
        if (sock->state == SS_LISTENING) {
            res = -EPIPE;
            goto exit;
        }
        if (sock->state != SS_UNCONNECTED) {
            res = -EISCONN;
            goto exit;
        }
        if ((tport->published) ||
            ((sock->type == SOCK_STREAM) && (total_len != 0))) {
            res = -EOPNOTSUPP;
            goto exit;
        }
        if (dest->addrtype == TIPC_ADDR_NAME) {
            tport->conn_type = dest->addr.name.name.type;
            tport->conn_instance = dest->addr.name.name.instance;
        }

        /* Abort any pending connection attempts (very unlikely) */
        reject_rx_queue(sk);
    }

    timeout_val = sock_sndtimeo(sk, m->msg_flags & MSG_DONTWAIT);

    do {
        if (dest->addrtype == TIPC_ADDR_NAME) {
            res = dest_name_check(dest, m);
            if (res)
                break;
            res = tipc_send2name(tport->ref,
                         &dest->addr.name.name,
                         dest->addr.name.domain,
                         m->msg_iovlen,
                         m->msg_iov,
                         total_len);
        } else if (dest->addrtype == TIPC_ADDR_ID) {
            res = tipc_send2port(tport->ref,
                         &dest->addr.id,
                         m->msg_iovlen,
                         m->msg_iov,
                         total_len);
        } else if (dest->addrtype == TIPC_ADDR_MCAST) {
            if (needs_conn) {
                res = -EOPNOTSUPP;
                break;
            }
            res = dest_name_check(dest, m);
            if (res)
                break;
            res = tipc_multicast(tport->ref,
                         &dest->addr.nameseq,
                         m->msg_iovlen,
                         m->msg_iov,
                         total_len);
        }
        if (likely(res != -ELINKCONG)) {
            if (needs_conn && (res >= 0))
                sock->state = SS_CONNECTING;
            break;
        }
        if (timeout_val <= 0L) {
            res = timeout_val ? timeout_val : -EWOULDBLOCK;
            break;
        }
        release_sock(sk);
        timeout_val = wait_event_interruptible_timeout(*sk_sleep(sk),
                           !tport->congested, timeout_val);
        lock_sock(sk);
    } while (1);

exit:
    if (iocb)
        release_sock(sk);
    return res;
}

static int send_packet(struct kiocb *iocb, struct socket *sock,
               struct msghdr *m, size_t total_len)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    struct sockaddr_tipc *dest = (struct sockaddr_tipc *)m->msg_name;
    long timeout_val;
    int res;

    /* Handle implied connection establishment */
    if (unlikely(dest))
        return send_msg(iocb, sock, m, total_len);

    if ((total_len > TIPC_MAX_USER_MSG_SIZE) ||
        (m->msg_iovlen > (unsigned int)INT_MAX))
        return -EMSGSIZE;

    if (iocb)
        lock_sock(sk);

    timeout_val = sock_sndtimeo(sk, m->msg_flags & MSG_DONTWAIT);

    do {
        if (unlikely(sock->state != SS_CONNECTED)) {
            if (sock->state == SS_DISCONNECTING)
                res = -EPIPE;
            else
                res = -ENOTCONN;
            break;
        }

        res = tipc_send(tport->ref, m->msg_iovlen, m->msg_iov,
                total_len);
        if (likely(res != -ELINKCONG))
            break;
        if (timeout_val <= 0L) {
            res = timeout_val ? timeout_val : -EWOULDBLOCK;
            break;
        }
        release_sock(sk);
        timeout_val = wait_event_interruptible_timeout(*sk_sleep(sk),
            (!tport->congested || !tport->connected), timeout_val);
        lock_sock(sk);
    } while (1);

    if (iocb)
        release_sock(sk);
    return res;
}

static int send_stream(struct kiocb *iocb, struct socket *sock,
               struct msghdr *m, size_t total_len)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    struct msghdr my_msg;
    struct iovec my_iov;
    struct iovec *curr_iov;
    int curr_iovlen;
    char __user *curr_start;
    u32 hdr_size;
    int curr_left;
    int bytes_to_send;
    int bytes_sent;
    int res;

    lock_sock(sk);

    /* Handle special cases where there is no connection */
    if (unlikely(sock->state != SS_CONNECTED)) {
        if (sock->state == SS_UNCONNECTED) {
            res = send_packet(NULL, sock, m, total_len);
            goto exit;
        } else if (sock->state == SS_DISCONNECTING) {
            res = -EPIPE;
            goto exit;
        } else {
            res = -ENOTCONN;
            goto exit;
        }
    }

    if (unlikely(m->msg_name)) {
        res = -EISCONN;
        goto exit;
    }

    if ((total_len > (unsigned int)INT_MAX) ||
        (m->msg_iovlen > (unsigned int)INT_MAX)) {
        res = -EMSGSIZE;
        goto exit;
    }

    /*
     * Send each iovec entry using one or more messages
     *
     * Note: This algorithm is good for the most likely case
     * (i.e. one large iovec entry), but could be improved to pass sets
     * of small iovec entries into send_packet().
     */
    curr_iov = m->msg_iov;
    curr_iovlen = m->msg_iovlen;
    my_msg.msg_iov = &my_iov;
    my_msg.msg_iovlen = 1;
    my_msg.msg_flags = m->msg_flags;
    my_msg.msg_name = NULL;
    bytes_sent = 0;

    hdr_size = msg_hdr_sz(&tport->phdr);

    while (curr_iovlen--) {
        curr_start = curr_iov->iov_base;
        curr_left = curr_iov->iov_len;

        while (curr_left) {
            bytes_to_send = tport->max_pkt - hdr_size;
            if (bytes_to_send > TIPC_MAX_USER_MSG_SIZE)
                bytes_to_send = TIPC_MAX_USER_MSG_SIZE;
            if (curr_left < bytes_to_send)
                bytes_to_send = curr_left;
            my_iov.iov_base = curr_start;
            my_iov.iov_len = bytes_to_send;
            res = send_packet(NULL, sock, &my_msg, bytes_to_send);
            if (res < 0) {
                if (bytes_sent)
                    res = bytes_sent;
                goto exit;
            }
            curr_left -= bytes_to_send;
            curr_start += bytes_to_send;
            bytes_sent += bytes_to_send;
        }

        curr_iov++;
    }
    res = bytes_sent;
exit:
    release_sock(sk);
    return res;
}

static int auto_connect(struct socket *sock, struct tipc_msg *msg)
{
    struct tipc_sock *tsock = tipc_sk(sock->sk);

    if (msg_errcode(msg)) {
        sock->state = SS_DISCONNECTING;
        return -ECONNREFUSED;
    }

    tsock->peer_name.ref = msg_origport(msg);
    tsock->peer_name.node = msg_orignode(msg);
    tipc_connect2port(tsock->p->ref, &tsock->peer_name);
    tipc_set_portimportance(tsock->p->ref, msg_importance(msg));
    sock->state = SS_CONNECTED;
    return 0;
}

static void set_orig_addr(struct msghdr *m, struct tipc_msg *msg)
{
    struct sockaddr_tipc *addr = (struct sockaddr_tipc *)m->msg_name;

    if (addr) {
        addr->family = AF_TIPC;
        addr->addrtype = TIPC_ADDR_ID;
        addr->addr.id.ref = msg_origport(msg);
        addr->addr.id.node = msg_orignode(msg);
        addr->addr.name.domain = 0; /* could leave uninitialized */
        addr->scope = 0;        /* could leave uninitialized */
        m->msg_namelen = sizeof(struct sockaddr_tipc);
    }
}

static int anc_data_recv(struct msghdr *m, struct tipc_msg *msg,
                struct tipc_port *tport)
{
    u32 anc_data[3];
    u32 err;
    u32 dest_type;
    int has_name;
    int res;

    if (likely(m->msg_controllen == 0))
        return 0;

    /* Optionally capture errored message object(s) */
    err = msg ? msg_errcode(msg) : 0;
    if (unlikely(err)) {
        anc_data[0] = err;
        anc_data[1] = msg_data_sz(msg);
        res = put_cmsg(m, SOL_TIPC, TIPC_ERRINFO, 8, anc_data);
        if (res)
            return res;
        if (anc_data[1]) {
            res = put_cmsg(m, SOL_TIPC, TIPC_RETDATA, anc_data[1],
                       msg_data(msg));
            if (res)
                return res;
        }
    }

    /* Optionally capture message destination object */
    dest_type = msg ? msg_type(msg) : TIPC_DIRECT_MSG;
    switch (dest_type) {
    case TIPC_NAMED_MSG:
        has_name = 1;
        anc_data[0] = msg_nametype(msg);
        anc_data[1] = msg_namelower(msg);
        anc_data[2] = msg_namelower(msg);
        break;
    case TIPC_MCAST_MSG:
        has_name = 1;
        anc_data[0] = msg_nametype(msg);
        anc_data[1] = msg_namelower(msg);
        anc_data[2] = msg_nameupper(msg);
        break;
    case TIPC_CONN_MSG:
        has_name = (tport->conn_type != 0);
        anc_data[0] = tport->conn_type;
        anc_data[1] = tport->conn_instance;
        anc_data[2] = tport->conn_instance;
        break;
    default:
        has_name = 0;
    }
    if (has_name) {
        res = put_cmsg(m, SOL_TIPC, TIPC_DESTNAME, 12, anc_data);
        if (res)
            return res;
    }

    return 0;
}

static int recv_msg(struct kiocb *iocb, struct socket *sock,
            struct msghdr *m, size_t buf_len, int flags)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    struct sk_buff *buf;
    struct tipc_msg *msg;
    long timeout;
    unsigned int sz;
    u32 err;
    int res;

    /* Catch invalid receive requests */
    if (unlikely(!buf_len))
        return -EINVAL;

    lock_sock(sk);

    if (unlikely(sock->state == SS_UNCONNECTED)) {
        res = -ENOTCONN;
        goto exit;
    }

    timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
restart:

    /* Look for a message in receive queue; wait if necessary */
    while (skb_queue_empty(&sk->sk_receive_queue)) {
        if (sock->state == SS_DISCONNECTING) {
            res = -ENOTCONN;
            goto exit;
        }
        if (timeout <= 0L) {
            res = timeout ? timeout : -EWOULDBLOCK;
            goto exit;
        }
        release_sock(sk);
        timeout = wait_event_interruptible_timeout(*sk_sleep(sk),
                               tipc_rx_ready(sock),
                               timeout);
        lock_sock(sk);
    }

    /* Look at first message in receive queue */
    buf = skb_peek(&sk->sk_receive_queue);
    msg = buf_msg(buf);
    sz = msg_data_sz(msg);
    err = msg_errcode(msg);

    /* Complete connection setup for an implied connect */
    if (unlikely(sock->state == SS_CONNECTING)) {
        res = auto_connect(sock, msg);
        if (res)
            goto exit;
    }

    /* Discard an empty non-errored message & try again */
    if ((!sz) && (!err)) {
        advance_rx_queue(sk);
        goto restart;
    }

    /* Capture sender's address (optional) */
    set_orig_addr(m, msg);

    /* Capture ancillary data (optional) */
    res = anc_data_recv(m, msg, tport);
    if (res)
        goto exit;

    /* Capture message data (if valid) & compute return value (always) */
    if (!err) {
        if (unlikely(buf_len < sz)) {
            sz = buf_len;
            m->msg_flags |= MSG_TRUNC;
        }
        res = skb_copy_datagram_iovec(buf, msg_hdr_sz(msg),
                          m->msg_iov, sz);
        if (res)
            goto exit;
        res = sz;
    } else {
        if ((sock->state == SS_READY) ||
            ((err == TIPC_CONN_SHUTDOWN) || m->msg_control))
            res = 0;
        else
            res = -ECONNRESET;
    }

    /* Consume received message (optional) */
    if (likely(!(flags & MSG_PEEK))) {
        if ((sock->state != SS_READY) &&
            (++tport->conn_unacked >= TIPC_FLOW_CONTROL_WIN))
            tipc_acknowledge(tport->ref, tport->conn_unacked);
        advance_rx_queue(sk);
    }
exit:
    release_sock(sk);
    return res;
}

static int recv_stream(struct kiocb *iocb, struct socket *sock,
               struct msghdr *m, size_t buf_len, int flags)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    struct sk_buff *buf;
    struct tipc_msg *msg;
    long timeout;
    unsigned int sz;
    int sz_to_copy, target, needed;
    int sz_copied = 0;
    u32 err;
    int res = 0;

    /* Catch invalid receive attempts */
    if (unlikely(!buf_len))
        return -EINVAL;

    lock_sock(sk);

    if (unlikely((sock->state == SS_UNCONNECTED) ||
             (sock->state == SS_CONNECTING))) {
        res = -ENOTCONN;
        goto exit;
    }

    target = sock_rcvlowat(sk, flags & MSG_WAITALL, buf_len);
    timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);

restart:
    /* Look for a message in receive queue; wait if necessary */
    while (skb_queue_empty(&sk->sk_receive_queue)) {
        if (sock->state == SS_DISCONNECTING) {
            res = -ENOTCONN;
            goto exit;
        }
        if (timeout <= 0L) {
            res = timeout ? timeout : -EWOULDBLOCK;
            goto exit;
        }
        release_sock(sk);
        timeout = wait_event_interruptible_timeout(*sk_sleep(sk),
                               tipc_rx_ready(sock),
                               timeout);
        lock_sock(sk);
    }

    /* Look at first message in receive queue */
    buf = skb_peek(&sk->sk_receive_queue);
    msg = buf_msg(buf);
    sz = msg_data_sz(msg);
    err = msg_errcode(msg);

    /* Discard an empty non-errored message & try again */
    if ((!sz) && (!err)) {
        advance_rx_queue(sk);
        goto restart;
    }

    /* Optionally capture sender's address & ancillary data of first msg */
    if (sz_copied == 0) {
        set_orig_addr(m, msg);
        res = anc_data_recv(m, msg, tport);
        if (res)
            goto exit;
    }

    /* Capture message data (if valid) & compute return value (always) */
    if (!err) {
        u32 offset = (u32)(unsigned long)(TIPC_SKB_CB(buf)->handle);

        sz -= offset;
        needed = (buf_len - sz_copied);
        sz_to_copy = (sz <= needed) ? sz : needed;

        res = skb_copy_datagram_iovec(buf, msg_hdr_sz(msg) + offset,
                          m->msg_iov, sz_to_copy);
        if (res)
            goto exit;

        sz_copied += sz_to_copy;

        if (sz_to_copy < sz) {
            if (!(flags & MSG_PEEK))
                TIPC_SKB_CB(buf)->handle =
                (void *)(unsigned long)(offset + sz_to_copy);
            goto exit;
        }
    } else {
        if (sz_copied != 0)
            goto exit; /* can't add error msg to valid data */

        if ((err == TIPC_CONN_SHUTDOWN) || m->msg_control)
            res = 0;
        else
            res = -ECONNRESET;
    }

    /* Consume received message (optional) */
    if (likely(!(flags & MSG_PEEK))) {
        if (unlikely(++tport->conn_unacked >= TIPC_FLOW_CONTROL_WIN))
            tipc_acknowledge(tport->ref, tport->conn_unacked);
        advance_rx_queue(sk);
    }

    /* Loop around if more data is required */
    if ((sz_copied < buf_len) &&    /* didn't get all requested data */
        (!skb_queue_empty(&sk->sk_receive_queue) ||
        (sz_copied < target)) &&    /* and more is ready or required */
        (!(flags & MSG_PEEK)) &&    /* and aren't just peeking at data */
        (!err))         /* and haven't reached a FIN */
        goto restart;

exit:
    release_sock(sk);
    return sz_copied ? sz_copied : res;
}

static int rx_queue_full(struct tipc_msg *msg, u32 queue_size, u32 base)
{
    u32 threshold;
    u32 imp = msg_importance(msg);

    if (imp == TIPC_LOW_IMPORTANCE)
        threshold = base;
    else if (imp == TIPC_MEDIUM_IMPORTANCE)
        threshold = base * 2;
    else if (imp == TIPC_HIGH_IMPORTANCE)
        threshold = base * 100;
    else
        return 0;

    if (msg_connected(msg))
        threshold *= 4;

    return queue_size >= threshold;
}

static u32 filter_rcv(struct sock *sk, struct sk_buff *buf)
{
    struct socket *sock = sk->sk_socket;
    struct tipc_msg *msg = buf_msg(buf);
    u32 recv_q_len;

    /* Reject message if it is wrong sort of message for socket */
    if (msg_type(msg) > TIPC_DIRECT_MSG)
        return TIPC_ERR_NO_PORT;

    if (sock->state == SS_READY) {
        if (msg_connected(msg))
            return TIPC_ERR_NO_PORT;
    } else {
        if (msg_mcast(msg))
            return TIPC_ERR_NO_PORT;
        if (sock->state == SS_CONNECTED) {
            if (!msg_connected(msg) ||
                !tipc_port_peer_msg(tipc_sk_port(sk), msg))
                return TIPC_ERR_NO_PORT;
        } else if (sock->state == SS_CONNECTING) {
            if (!msg_connected(msg) && (msg_errcode(msg) == 0))
                return TIPC_ERR_NO_PORT;
        } else if (sock->state == SS_LISTENING) {
            if (msg_connected(msg) || msg_errcode(msg))
                return TIPC_ERR_NO_PORT;
        } else if (sock->state == SS_DISCONNECTING) {
            return TIPC_ERR_NO_PORT;
        } else /* (sock->state == SS_UNCONNECTED) */ {
            if (msg_connected(msg) || msg_errcode(msg))
                return TIPC_ERR_NO_PORT;
        }
    }

    /* Reject message if there isn't room to queue it */
    recv_q_len = (u32)atomic_read(&tipc_queue_size);
    if (unlikely(recv_q_len >= OVERLOAD_LIMIT_BASE)) {
        if (rx_queue_full(msg, recv_q_len, OVERLOAD_LIMIT_BASE))
            return TIPC_ERR_OVERLOAD;
    }
    recv_q_len = skb_queue_len(&sk->sk_receive_queue);
    if (unlikely(recv_q_len >= (OVERLOAD_LIMIT_BASE / 2))) {
        if (rx_queue_full(msg, recv_q_len, OVERLOAD_LIMIT_BASE / 2))
            return TIPC_ERR_OVERLOAD;
    }

    /* Enqueue message (finally!) */
    TIPC_SKB_CB(buf)->handle = 0;
    atomic_inc(&tipc_queue_size);
    __skb_queue_tail(&sk->sk_receive_queue, buf);

    /* Initiate connection termination for an incoming 'FIN' */
    if (unlikely(msg_errcode(msg) && (sock->state == SS_CONNECTED))) {
        sock->state = SS_DISCONNECTING;
        tipc_disconnect_port(tipc_sk_port(sk));
    }

    if (waitqueue_active(sk_sleep(sk)))
        wake_up_interruptible(sk_sleep(sk));
    return TIPC_OK;
}

static int backlog_rcv(struct sock *sk, struct sk_buff *buf)
{
    u32 res;

    res = filter_rcv(sk, buf);
    if (res)
        tipc_reject_msg(buf, res);
    return 0;
}

static u32 dispatch(struct tipc_port *tport, struct sk_buff *buf)
{
    struct sock *sk = (struct sock *)tport->usr_handle;
    u32 res;

    /*
     * Process message if socket is unlocked; otherwise add to backlog queue
     *
     * This code is based on sk_receive_skb(), but must be distinct from it
     * since a TIPC-specific filter/reject mechanism is utilized
     */
    bh_lock_sock(sk);
    if (!sock_owned_by_user(sk)) {
        res = filter_rcv(sk, buf);
    } else {
        if (sk_add_backlog(sk, buf, sk->sk_rcvbuf))
            res = TIPC_ERR_OVERLOAD;
        else
            res = TIPC_OK;
    }
    bh_unlock_sock(sk);

    return res;
}

static void wakeupdispatch(struct tipc_port *tport)
{
    struct sock *sk = (struct sock *)tport->usr_handle;

    if (waitqueue_active(sk_sleep(sk)))
        wake_up_interruptible(sk_sleep(sk));
}

static int connect(struct socket *sock, struct sockaddr *dest, int destlen,
           int flags)
{
    struct sock *sk = sock->sk;
    struct sockaddr_tipc *dst = (struct sockaddr_tipc *)dest;
    struct msghdr m = {NULL,};
    struct sk_buff *buf;
    struct tipc_msg *msg;
    unsigned int timeout;
    int res;

    lock_sock(sk);

    /* For now, TIPC does not allow use of connect() with DGRAM/RDM types */
    if (sock->state == SS_READY) {
        res = -EOPNOTSUPP;
        goto exit;
    }

    /* For now, TIPC does not support the non-blocking form of connect() */
    if (flags & O_NONBLOCK) {
        res = -EOPNOTSUPP;
        goto exit;
    }

    /* Issue Posix-compliant error code if socket is in the wrong state */
    if (sock->state == SS_LISTENING) {
        res = -EOPNOTSUPP;
        goto exit;
    }
    if (sock->state == SS_CONNECTING) {
        res = -EALREADY;
        goto exit;
    }
    if (sock->state != SS_UNCONNECTED) {
        res = -EISCONN;
        goto exit;
    }

    /*
     * Reject connection attempt using multicast address
     *
     * Note: send_msg() validates the rest of the address fields,
     *       so there's no need to do it here
     */
    if (dst->addrtype == TIPC_ADDR_MCAST) {
        res = -EINVAL;
        goto exit;
    }

    /* Reject any messages already in receive queue (very unlikely) */
    reject_rx_queue(sk);

    /* Send a 'SYN-' to destination */
    m.msg_name = dest;
    m.msg_namelen = destlen;
    res = send_msg(NULL, sock, &m, 0);
    if (res < 0)
        goto exit;

    /* Wait until an 'ACK' or 'RST' arrives, or a timeout occurs */
    timeout = tipc_sk(sk)->conn_timeout;
    release_sock(sk);
    res = wait_event_interruptible_timeout(*sk_sleep(sk),
            (!skb_queue_empty(&sk->sk_receive_queue) ||
            (sock->state != SS_CONNECTING)),
            timeout ? (long)msecs_to_jiffies(timeout)
                : MAX_SCHEDULE_TIMEOUT);
    lock_sock(sk);

    if (res > 0) {
        buf = skb_peek(&sk->sk_receive_queue);
        if (buf != NULL) {
            msg = buf_msg(buf);
            res = auto_connect(sock, msg);
            if (!res) {
                if (!msg_data_sz(msg))
                    advance_rx_queue(sk);
            }
        } else {
            if (sock->state == SS_CONNECTED)
                res = -EISCONN;
            else
                res = -ECONNREFUSED;
        }
    } else {
        if (res == 0)
            res = -ETIMEDOUT;
        else
            ; /* leave "res" unchanged */
        sock->state = SS_DISCONNECTING;
    }

exit:
    release_sock(sk);
    return res;
}

static int listen(struct socket *sock, int len)
{
    struct sock *sk = sock->sk;
    int res;

    lock_sock(sk);

    if (sock->state != SS_UNCONNECTED)
        res = -EINVAL;
    else {
        sock->state = SS_LISTENING;
        res = 0;
    }

    release_sock(sk);
    return res;
}

static int accept(struct socket *sock, struct socket *new_sock, int flags)
{
    struct sock *sk = sock->sk;
    struct sk_buff *buf;
    int res;

    lock_sock(sk);

    if (sock->state != SS_LISTENING) {
        res = -EINVAL;
        goto exit;
    }

    while (skb_queue_empty(&sk->sk_receive_queue)) {
        if (flags & O_NONBLOCK) {
            res = -EWOULDBLOCK;
            goto exit;
        }
        release_sock(sk);
        res = wait_event_interruptible(*sk_sleep(sk),
                (!skb_queue_empty(&sk->sk_receive_queue)));
        lock_sock(sk);
        if (res)
            goto exit;
    }

    buf = skb_peek(&sk->sk_receive_queue);

    res = tipc_create(sock_net(sock->sk), new_sock, 0, 0);
    if (!res) {
        struct sock *new_sk = new_sock->sk;
        struct tipc_sock *new_tsock = tipc_sk(new_sk);
        struct tipc_port *new_tport = new_tsock->p;
        u32 new_ref = new_tport->ref;
        struct tipc_msg *msg = buf_msg(buf);

        lock_sock(new_sk);

        /*
         * Reject any stray messages received by new socket
         * before the socket lock was taken (very, very unlikely)
         */
        reject_rx_queue(new_sk);

        /* Connect new socket to it's peer */
        new_tsock->peer_name.ref = msg_origport(msg);
        new_tsock->peer_name.node = msg_orignode(msg);
        tipc_connect2port(new_ref, &new_tsock->peer_name);
        new_sock->state = SS_CONNECTED;

        tipc_set_portimportance(new_ref, msg_importance(msg));
        if (msg_named(msg)) {
            new_tport->conn_type = msg_nametype(msg);
            new_tport->conn_instance = msg_nameinst(msg);
        }

        /*
         * Respond to 'SYN-' by discarding it & returning 'ACK'-.
         * Respond to 'SYN+' by queuing it on new socket.
         */
        if (!msg_data_sz(msg)) {
            struct msghdr m = {NULL,};

            advance_rx_queue(sk);
            send_packet(NULL, new_sock, &m, 0);
        } else {
            __skb_dequeue(&sk->sk_receive_queue);
            __skb_queue_head(&new_sk->sk_receive_queue, buf);
        }
        release_sock(new_sk);
    }
exit:
    release_sock(sk);
    return res;
}

static int shutdown(struct socket *sock, int how)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    struct sk_buff *buf;
    int res;

    if (how != SHUT_RDWR)
        return -EINVAL;

    lock_sock(sk);

    switch (sock->state) {
    case SS_CONNECTING:
    case SS_CONNECTED:

restart:
        /* Disconnect and send a 'FIN+' or 'FIN-' message to peer */
        buf = __skb_dequeue(&sk->sk_receive_queue);
        if (buf) {
            atomic_dec(&tipc_queue_size);
            if (TIPC_SKB_CB(buf)->handle != 0) {
                kfree_skb(buf);
                goto restart;
            }
            tipc_disconnect(tport->ref);
            tipc_reject_msg(buf, TIPC_CONN_SHUTDOWN);
        } else {
            tipc_shutdown(tport->ref);
        }

        sock->state = SS_DISCONNECTING;

        /* fall through */

    case SS_DISCONNECTING:

        /* Discard any unreceived messages; wake up sleeping tasks */
        discard_rx_queue(sk);
        if (waitqueue_active(sk_sleep(sk)))
            wake_up_interruptible(sk_sleep(sk));
        res = 0;
        break;

    default:
        res = -ENOTCONN;
    }

    release_sock(sk);
    return res;
}

static int setsockopt(struct socket *sock,
              int lvl, int opt, char __user *ov, unsigned int ol)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    u32 value;
    int res;

    if ((lvl == IPPROTO_TCP) && (sock->type == SOCK_STREAM))
        return 0;
    if (lvl != SOL_TIPC)
        return -ENOPROTOOPT;
    if (ol < sizeof(value))
        return -EINVAL;
    res = get_user(value, (u32 __user *)ov);
    if (res)
        return res;

    lock_sock(sk);

    switch (opt) {
    case TIPC_IMPORTANCE:
        res = tipc_set_portimportance(tport->ref, value);
        break;
    case TIPC_SRC_DROPPABLE:
        if (sock->type != SOCK_STREAM)
            res = tipc_set_portunreliable(tport->ref, value);
        else
            res = -ENOPROTOOPT;
        break;
    case TIPC_DEST_DROPPABLE:
        res = tipc_set_portunreturnable(tport->ref, value);
        break;
    case TIPC_CONN_TIMEOUT:
        tipc_sk(sk)->conn_timeout = value;
        /* no need to set "res", since already 0 at this point */
        break;
    default:
        res = -EINVAL;
    }

    release_sock(sk);

    return res;
}

static int getsockopt(struct socket *sock,
              int lvl, int opt, char __user *ov, int __user *ol)
{
    struct sock *sk = sock->sk;
    struct tipc_port *tport = tipc_sk_port(sk);
    int len;
    u32 value;
    int res;

    if ((lvl == IPPROTO_TCP) && (sock->type == SOCK_STREAM))
        return put_user(0, ol);
    if (lvl != SOL_TIPC)
        return -ENOPROTOOPT;
    res = get_user(len, ol);
    if (res)
        return res;

    lock_sock(sk);

    switch (opt) {
    case TIPC_IMPORTANCE:
        res = tipc_portimportance(tport->ref, &value);
        break;
    case TIPC_SRC_DROPPABLE:
        res = tipc_portunreliable(tport->ref, &value);
        break;
    case TIPC_DEST_DROPPABLE:
        res = tipc_portunreturnable(tport->ref, &value);
        break;
    case TIPC_CONN_TIMEOUT:
        value = tipc_sk(sk)->conn_timeout;
        /* no need to set "res", since already 0 at this point */
        break;
    case TIPC_NODE_RECVQ_DEPTH:
        value = (u32)atomic_read(&tipc_queue_size);
        break;
    case TIPC_SOCK_RECVQ_DEPTH:
        value = skb_queue_len(&sk->sk_receive_queue);
        break;
    default:
        res = -EINVAL;
    }

    release_sock(sk);

    if (res)
        return res; /* "get" failed */

    if (len < sizeof(value))
        return -EINVAL;

    if (copy_to_user(ov, &value, sizeof(value)))
        return -EFAULT;

    return put_user(sizeof(value), ol);
}

/* Protocol switches for the various types of TIPC sockets */

static const struct proto_ops msg_ops = {
    .owner      = THIS_MODULE,
    .family     = AF_TIPC,
    .release    = release,
    .bind       = bind,
    .connect    = connect,
    .socketpair = sock_no_socketpair,
    .accept     = sock_no_accept,
    .getname    = get_name,
    .poll       = poll,
    .ioctl      = sock_no_ioctl,
    .listen     = sock_no_listen,
    .shutdown   = shutdown,
    .setsockopt = setsockopt,
    .getsockopt = getsockopt,
    .sendmsg    = send_msg,
    .recvmsg    = recv_msg,
    .mmap       = sock_no_mmap,
    .sendpage   = sock_no_sendpage
};

static const struct proto_ops packet_ops = {
    .owner      = THIS_MODULE,
    .family     = AF_TIPC,
    .release    = release,
    .bind       = bind,
    .connect    = connect,
    .socketpair = sock_no_socketpair,
    .accept     = accept,
    .getname    = get_name,
    .poll       = poll,
    .ioctl      = sock_no_ioctl,
    .listen     = listen,
    .shutdown   = shutdown,
    .setsockopt = setsockopt,
    .getsockopt = getsockopt,
    .sendmsg    = send_packet,
    .recvmsg    = recv_msg,
    .mmap       = sock_no_mmap,
    .sendpage   = sock_no_sendpage
};

static const struct proto_ops stream_ops = {
    .owner      = THIS_MODULE,
    .family     = AF_TIPC,
    .release    = release,
    .bind       = bind,
    .connect    = connect,
    .socketpair = sock_no_socketpair,
    .accept     = accept,
    .getname    = get_name,
    .poll       = poll,
    .ioctl      = sock_no_ioctl,
    .listen     = listen,
    .shutdown   = shutdown,
    .setsockopt = setsockopt,
    .getsockopt = getsockopt,
    .sendmsg    = send_stream,
    .recvmsg    = recv_stream,
    .mmap       = sock_no_mmap,
    .sendpage   = sock_no_sendpage
};

static const struct net_proto_family tipc_family_ops = {
    .owner      = THIS_MODULE,
    .family     = AF_TIPC,
    .create     = tipc_create
};

static struct proto tipc_proto = {
    .name       = "TIPC",
    .owner      = THIS_MODULE,
    .obj_size   = sizeof(struct tipc_sock)
};

int tipc_socket_init(void)
{
    int res;

    res = proto_register(&tipc_proto, 1);
    if (res) {
        pr_err("Failed to register TIPC protocol type\n");
        goto out;
    }

    res = sock_register(&tipc_family_ops);
    if (res) {
        pr_err("Failed to register TIPC socket type\n");
        proto_unregister(&tipc_proto);
        goto out;
    }

    sockets_enabled = 1;
 out:
    return res;
}

void tipc_socket_stop(void)
{
    if (!sockets_enabled)
        return;

    sockets_enabled = 0;
    sock_unregister(tipc_family_ops.family);
    proto_unregister(&tipc_proto);
}