tipc: standardize sendmsg routine of connected socket

[linux-2.6/btrfs-unstable.git] / net / tipc / socket.c

/*
 * net/tipc/socket.c: TIPC socket API
 *
 * Copyright (c) 2001-2007, 2012 Ericsson AB
 * Copyright (c) 2004-2008, 2010-2013, 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 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 void tipc_data_ready(struct sock *sk, int len);
static void tipc_write_space(struct sock *sk);
static int release(struct socket *sock);
static int accept(struct socket *sock, struct socket *new_sock, int flags);

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 struct proto tipc_proto_kern;

static int sockets_enabled;

/*
 * 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
 */

/**
 * advance_rx_queue - discard first buffer in socket receive queue
 *
 * Caller must hold socket lock
 */
static void advance_rx_queue(struct sock *sk)
{
        kfree_skb(__skb_dequeue(&sk->sk_receive_queue));
}

/**
 * reject_rx_queue - reject all buffers in socket receive queue
 *
 * Caller must hold socket lock
 */
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);
}

/**
 * tipc_sk_create - create a TIPC socket
 * @net: network namespace (must be default network)
 * @sock: pre-allocated socket structure
 * @protocol: protocol indicator (must be 0)
 * @kern: caused by kernel or by userspace?
 *
 * This routine creates additional data structures used by the TIPC socket,
 * initializes them, and links them together.
 *
 * Returns 0 on success, errno otherwise
 */
static int tipc_sk_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 */
        if (!kern)
                sk = sk_alloc(net, AF_TIPC, GFP_KERNEL, &tipc_proto);
        else
                sk = sk_alloc(net, AF_TIPC, GFP_KERNEL, &tipc_proto_kern);

        if (sk == NULL)
                return -ENOMEM;

        /* Allocate TIPC port for socket to use */
        tp_ptr = tipc_createport(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 = sysctl_tipc_rmem[1];
        sk->sk_data_ready = tipc_data_ready;
        sk->sk_write_space = tipc_write_space;
        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;
}

/**
 * tipc_sock_create_local - create TIPC socket from inside TIPC module
 * @type: socket type - SOCK_RDM or SOCK_SEQPACKET
 *
 * We cannot use sock_creat_kern here because it bumps module user count.
 * Since socket owner and creator is the same module we must make sure
 * that module count remains zero for module local sockets, otherwise
 * we cannot do rmmod.
 *
 * Returns 0 on success, errno otherwise
 */
int tipc_sock_create_local(int type, struct socket **res)
{
        int rc;

        rc = sock_create_lite(AF_TIPC, type, 0, res);
        if (rc < 0) {
                pr_err("Failed to create kernel socket\n");
                return rc;
        }
        tipc_sk_create(&init_net, *res, 0, 1);

        return 0;
}

/**
 * tipc_sock_release_local - release socket created by tipc_sock_create_local
 * @sock: the socket to be released.
 *
 * Module reference count is not incremented when such sockets are created,
 * so we must keep it from being decremented when they are released.
 */
void tipc_sock_release_local(struct socket *sock)
{
        release(sock);
        sock->ops = NULL;
        sock_release(sock);
}

/**
 * tipc_sock_accept_local - accept a connection on a socket created
 * with tipc_sock_create_local. Use this function to avoid that
 * module reference count is inadvertently incremented.
 *
 * @sock:    the accepting socket
 * @newsock: reference to the new socket to be created
 * @flags:   socket flags
 */

int tipc_sock_accept_local(struct socket *sock, struct socket **newsock,
                           int flags)
{
        struct sock *sk = sock->sk;
        int ret;

        ret = sock_create_lite(sk->sk_family, sk->sk_type,
                               sk->sk_protocol, newsock);
        if (ret < 0)
                return ret;

        ret = accept(sock, *newsock, flags);
        if (ret < 0) {
                sock_release(*newsock);
                return ret;
        }
        (*newsock)->ops = sock->ops;
        return ret;
}

/**
 * release - destroy a TIPC socket
 * @sock: socket to destroy
 *
 * This routine cleans up any messages that are still queued on the socket.
 * For DGRAM and RDM socket types, all queued messages are rejected.
 * For SEQPACKET and STREAM socket types, the first message is rejected
 * and any others are discarded.  (If the first message on a STREAM socket
 * is partially-read, it is discarded and the next one is rejected instead.)
 *
 * NOTE: Rejected messages are not necessarily returned to the sender!  They
 * are returned or discarded according to the "destination droppable" setting
 * specified for the message by the sender.
 *
 * Returns 0 on success, errno otherwise
 */
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;
                if (TIPC_SKB_CB(buf)->handle != NULL)
                        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);

        /* Discard any remaining (connection-based) messages in receive queue */
        __skb_queue_purge(&sk->sk_receive_queue);

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

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

        return res;
}

/**
 * bind - associate or disassocate TIPC name(s) with a socket
 * @sock: socket structure
 * @uaddr: socket address describing name(s) and desired operation
 * @uaddr_len: size of socket address data structure
 *
 * Name and name sequence binding is indicated using a positive scope value;
 * a negative scope value unbinds the specified name.  Specifying no name
 * (i.e. a socket address length of 0) unbinds all names from the socket.
 *
 * Returns 0 on success, errno otherwise
 *
 * NOTE: This routine doesn't need to take the socket lock since it doesn't
 *       access any non-constant socket information.
 */
static int bind(struct socket *sock, struct sockaddr *uaddr, int uaddr_len)
{
        struct sock *sk = sock->sk;
        struct sockaddr_tipc *addr = (struct sockaddr_tipc *)uaddr;
        struct tipc_port *tport = tipc_sk_port(sock->sk);
        int res = -EINVAL;

        lock_sock(sk);
        if (unlikely(!uaddr_len)) {
                res = tipc_withdraw(tport, 0, NULL);
                goto exit;
        }

        if (uaddr_len < sizeof(struct sockaddr_tipc)) {
                res = -EINVAL;
                goto exit;
        }
        if (addr->family != AF_TIPC) {
                res = -EAFNOSUPPORT;
                goto exit;
        }

        if (addr->addrtype == TIPC_ADDR_NAME)
                addr->addr.nameseq.upper = addr->addr.nameseq.lower;
        else if (addr->addrtype != TIPC_ADDR_NAMESEQ) {
                res = -EAFNOSUPPORT;
                goto exit;
        }

        if ((addr->addr.nameseq.type < TIPC_RESERVED_TYPES) &&
            (addr->addr.nameseq.type != TIPC_TOP_SRV) &&
            (addr->addr.nameseq.type != TIPC_CFG_SRV)) {
                res = -EACCES;
                goto exit;
        }

        res = (addr->scope > 0) ?
                tipc_publish(tport, addr->scope, &addr->addr.nameseq) :
                tipc_withdraw(tport, -addr->scope, &addr->addr.nameseq);
exit:
        release_sock(sk);
        return res;
}

/**
 * get_name - get port ID of socket or peer socket
 * @sock: socket structure
 * @uaddr: area for returned socket address
 * @uaddr_len: area for returned length of socket address
 * @peer: 0 = own ID, 1 = current peer ID, 2 = current/former peer ID
 *
 * Returns 0 on success, errno otherwise
 *
 * NOTE: This routine doesn't need to take the socket lock since it only
 *       accesses socket information that is unchanging (or which changes in
 *       a completely predictable manner).
 */
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;
}

/**
 * poll - read and possibly block on pollmask
 * @file: file structure associated with the socket
 * @sock: socket for which to calculate the poll bits
 * @wait: ???
 *
 * Returns pollmask value
 *
 * COMMENTARY:
 * It appears that the usual socket locking mechanisms are not useful here
 * since the pollmask info is potentially out-of-date the moment this routine
 * exits.  TCP and other protocols seem to rely on higher level poll routines
 * to handle any preventable race conditions, so TIPC will do the same ...
 *
 * TIPC sets the returned events as follows:
 *
 * socket state         flags set
 * ------------         ---------
 * unconnected          no read flags
 *                      POLLOUT if port is not congested
 *
 * connecting           POLLIN/POLLRDNORM if ACK/NACK in rx queue
 *                      no write flags
 *
 * connected            POLLIN/POLLRDNORM if data in rx queue
 *                      POLLOUT if port is not congested
 *
 * disconnecting        POLLIN/POLLRDNORM/POLLHUP
 *                      no write flags
 *
 * listening            POLLIN if SYN in rx queue
 *                      no write flags
 *
 * ready                POLLIN/POLLRDNORM if data in rx queue
 * [connectionless]     POLLOUT (since port cannot be congested)
 *
 * IMPORTANT: The fact that a read or write operation is indicated does NOT
 * imply that the operation will succeed, merely that it should be performed
 * and will not block.
 */
static unsigned int poll(struct file *file, struct socket *sock,
                         poll_table *wait)
{
        struct sock *sk = sock->sk;
        u32 mask = 0;

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

        switch ((int)sock->state) {
        case SS_UNCONNECTED:
                if (!tipc_sk_port(sk)->congested)
                        mask |= POLLOUT;
                break;
        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;
}

/**
 * dest_name_check - verify user is permitted to send to specified port name
 * @dest: destination address
 * @m: descriptor for message to be sent
 *
 * Prevents restricted configuration commands from being issued by
 * unauthorized users.
 *
 * Returns 0 if permission is granted, otherwise errno
 */
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 tipc_wait_for_sndmsg(struct socket *sock, long *timeo_p)
{
        struct sock *sk = sock->sk;
        struct tipc_port *tport = tipc_sk_port(sk);
        DEFINE_WAIT(wait);
        int done;

        do {
                int err = sock_error(sk);
                if (err)
                        return err;
                if (sock->state == SS_DISCONNECTING)
                        return -EPIPE;
                if (!*timeo_p)
                        return -EAGAIN;
                if (signal_pending(current))
                        return sock_intr_errno(*timeo_p);

                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
                done = sk_wait_event(sk, timeo_p, !tport->congested);
                finish_wait(sk_sleep(sk), &wait);
        } while (!done);
        return 0;
}

/**
 * send_msg - send message in connectionless manner
 * @iocb: if NULL, indicates that socket lock is already held
 * @sock: socket structure
 * @m: message to send
 * @total_len: length of message
 *
 * Message must have an destination specified explicitly.
 * Used for SOCK_RDM and SOCK_DGRAM messages,
 * and for 'SYN' messages on SOCK_SEQPACKET and SOCK_STREAM connections.
 * (Note: 'SYN+' is prohibited on SOCK_STREAM.)
 *
 * Returns the number of bytes sent on success, or errno otherwise
 */
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 timeo;
        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)
                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) {
                        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);
        }

        timeo = 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_iov,
                                             total_len);
                } else if (dest->addrtype == TIPC_ADDR_ID) {
                        res = tipc_send2port(tport->ref,
                                             &dest->addr.id,
                                             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_iov,
                                             total_len);
                }
                if (likely(res != -ELINKCONG)) {
                        if (needs_conn && (res >= 0))
                                sock->state = SS_CONNECTING;
                        break;
                }
                res = tipc_wait_for_sndmsg(sock, &timeo);
                if (res)
                        break;
        } while (1);

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

static int tipc_wait_for_sndpkt(struct socket *sock, long *timeo_p)
{
        struct sock *sk = sock->sk;
        struct tipc_port *tport = tipc_sk_port(sk);
        DEFINE_WAIT(wait);
        int done;

        do {
                int err = sock_error(sk);
                if (err)
                        return err;
                if (sock->state == SS_DISCONNECTING)
                        return -EPIPE;
                else if (sock->state != SS_CONNECTED)
                        return -ENOTCONN;
                if (!*timeo_p)
                        return -EAGAIN;
                if (signal_pending(current))
                        return sock_intr_errno(*timeo_p);

                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
                done = sk_wait_event(sk, timeo_p,
                                     (!tport->congested || !tport->connected));
                finish_wait(sk_sleep(sk), &wait);
        } while (!done);
        return 0;
}

/**
 * send_packet - send a connection-oriented message
 * @iocb: if NULL, indicates that socket lock is already held
 * @sock: socket structure
 * @m: message to send
 * @total_len: length of message
 *
 * Used for SOCK_SEQPACKET messages and SOCK_STREAM data.
 *
 * Returns the number of bytes sent on success, or errno otherwise
 */
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;
        int res = -EINVAL;
        long timeo;

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

        if (total_len > TIPC_MAX_USER_MSG_SIZE)
                return -EMSGSIZE;

        if (iocb)
                lock_sock(sk);

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

        timeo = sock_sndtimeo(sk, m->msg_flags & MSG_DONTWAIT);
        do {
                res = tipc_send(tport->ref, m->msg_iov, total_len);
                if (likely(res != -ELINKCONG))
                        break;
                res = tipc_wait_for_sndpkt(sock, &timeo);
                if (res)
                        break;
        } while (1);
exit:
        if (iocb)
                release_sock(sk);
        return res;
}

/**
 * send_stream - send stream-oriented data
 * @iocb: (unused)
 * @sock: socket structure
 * @m: data to send
 * @total_len: total length of data to be sent
 *
 * Used for SOCK_STREAM data.
 *
 * Returns the number of bytes sent on success (or partial success),
 * or errno if no data sent
 */
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);
                else
                        res = sock->state == SS_DISCONNECTING ? -EPIPE : -ENOTCONN;
                goto exit;
        }

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

        if (total_len > (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;
}

/**
 * auto_connect - complete connection setup to a remote port
 * @sock: socket structure
 * @msg: peer's response message
 *
 * Returns 0 on success, errno otherwise
 */
static int auto_connect(struct socket *sock, struct tipc_msg *msg)
{
        struct tipc_sock *tsock = tipc_sk(sock->sk);
        struct tipc_port *p_ptr;

        tsock->peer_name.ref = msg_origport(msg);
        tsock->peer_name.node = msg_orignode(msg);
        p_ptr = tipc_port_deref(tsock->p->ref);
        if (!p_ptr)
                return -EINVAL;

        __tipc_connect(tsock->p->ref, p_ptr, &tsock->peer_name);

        if (msg_importance(msg) > TIPC_CRITICAL_IMPORTANCE)
                return -EINVAL;
        msg_set_importance(&p_ptr->phdr, (u32)msg_importance(msg));
        sock->state = SS_CONNECTED;
        return 0;
}

/**
 * set_orig_addr - capture sender's address for received message
 * @m: descriptor for message info
 * @msg: received message header
 *
 * Note: Address is not captured if not requested by receiver.
 */
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;
                memset(&addr->addr, 0, sizeof(addr->addr));
                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);
        }
}

/**
 * anc_data_recv - optionally capture ancillary data for received message
 * @m: descriptor for message info
 * @msg: received message header
 * @tport: TIPC port associated with message
 *
 * Note: Ancillary data is not captured if not requested by receiver.
 *
 * Returns 0 if successful, otherwise errno
 */
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;
}

/**
 * recv_msg - receive packet-oriented message
 * @iocb: (unused)
 * @m: descriptor for message info
 * @buf_len: total size of user buffer area
 * @flags: receive flags
 *
 * Used for SOCK_DGRAM, SOCK_RDM, and SOCK_SEQPACKET messages.
 * If the complete message doesn't fit in user area, truncate it.
 *
 * Returns size of returned message data, errno otherwise
 */
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);

        /* 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;
}

/**
 * recv_stream - receive stream-oriented data
 * @iocb: (unused)
 * @m: descriptor for message info
 * @buf_len: total size of user buffer area
 * @flags: receive flags
 *
 * Used for SOCK_STREAM messages only.  If not enough data is available
 * will optionally wait for more; never truncates data.
 *
 * Returns size of returned message data, errno otherwise
 */
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))) {
                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;
}

/**
 * tipc_write_space - wake up thread if port congestion is released
 * @sk: socket
 */
static void tipc_write_space(struct sock *sk)
{
        struct socket_wq *wq;

        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (wq_has_sleeper(wq))
                wake_up_interruptible_sync_poll(&wq->wait, POLLOUT |
                                                POLLWRNORM | POLLWRBAND);
        rcu_read_unlock();
}

/**
 * tipc_data_ready - wake up threads to indicate messages have been received
 * @sk: socket
 * @len: the length of messages
 */
static void tipc_data_ready(struct sock *sk, int len)
{
        struct socket_wq *wq;

        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (wq_has_sleeper(wq))
                wake_up_interruptible_sync_poll(&wq->wait, POLLIN |
                                                POLLRDNORM | POLLRDBAND);
        rcu_read_unlock();
}

/**
 * filter_connect - Handle all incoming messages for a connection-based socket
 * @tsock: TIPC socket
 * @msg: message
 *
 * Returns TIPC error status code and socket error status code
 * once it encounters some errors
 */
static u32 filter_connect(struct tipc_sock *tsock, struct sk_buff **buf)
{
        struct socket *sock = tsock->sk.sk_socket;
        struct tipc_msg *msg = buf_msg(*buf);
        struct sock *sk = &tsock->sk;
        u32 retval = TIPC_ERR_NO_PORT;
        int res;

        if (msg_mcast(msg))
                return retval;

        switch ((int)sock->state) {
        case SS_CONNECTED:
                /* Accept only connection-based messages sent by peer */
                if (msg_connected(msg) && tipc_port_peer_msg(tsock->p, msg)) {
                        if (unlikely(msg_errcode(msg))) {
                                sock->state = SS_DISCONNECTING;
                                __tipc_disconnect(tsock->p);
                        }
                        retval = TIPC_OK;
                }
                break;
        case SS_CONNECTING:
                /* Accept only ACK or NACK message */
                if (unlikely(msg_errcode(msg))) {
                        sock->state = SS_DISCONNECTING;
                        sk->sk_err = ECONNREFUSED;
                        retval = TIPC_OK;
                        break;
                }

                if (unlikely(!msg_connected(msg)))
                        break;

                res = auto_connect(sock, msg);
                if (res) {
                        sock->state = SS_DISCONNECTING;
                        sk->sk_err = -res;
                        retval = TIPC_OK;
                        break;
                }

                /* If an incoming message is an 'ACK-', it should be
                 * discarded here because it doesn't contain useful
                 * data. In addition, we should try to wake up
                 * connect() routine if sleeping.
                 */
                if (msg_data_sz(msg) == 0) {
                        kfree_skb(*buf);
                        *buf = NULL;
                        if (waitqueue_active(sk_sleep(sk)))
                                wake_up_interruptible(sk_sleep(sk));
                }
                retval = TIPC_OK;
                break;
        case SS_LISTENING:
        case SS_UNCONNECTED:
                /* Accept only SYN message */
                if (!msg_connected(msg) && !(msg_errcode(msg)))
                        retval = TIPC_OK;
                break;
        case SS_DISCONNECTING:
                break;
        default:
                pr_err("Unknown socket state %u\n", sock->state);
        }
        return retval;
}

/**
 * rcvbuf_limit - get proper overload limit of socket receive queue
 * @sk: socket
 * @buf: message
 *
 * For all connection oriented messages, irrespective of importance,
 * the default overload value (i.e. 67MB) is set as limit.
 *
 * For all connectionless messages, by default new queue limits are
 * as belows:
 *
 * TIPC_LOW_IMPORTANCE       (4 MB)
 * TIPC_MEDIUM_IMPORTANCE    (8 MB)
 * TIPC_HIGH_IMPORTANCE      (16 MB)
 * TIPC_CRITICAL_IMPORTANCE  (32 MB)
 *
 * Returns overload limit according to corresponding message importance
 */
static unsigned int rcvbuf_limit(struct sock *sk, struct sk_buff *buf)
{
        struct tipc_msg *msg = buf_msg(buf);

        if (msg_connected(msg))
                return sysctl_tipc_rmem[2];

        return sk->sk_rcvbuf >> TIPC_CRITICAL_IMPORTANCE <<
                msg_importance(msg);
}

/**
 * filter_rcv - validate incoming message
 * @sk: socket
 * @buf: message
 *
 * Enqueues message on receive queue if acceptable; optionally handles
 * disconnect indication for a connected socket.
 *
 * Called with socket lock already taken; port lock may also be taken.
 *
 * Returns TIPC error status code (TIPC_OK if message is not to be rejected)
 */
static u32 filter_rcv(struct sock *sk, struct sk_buff *buf)
{
        struct socket *sock = sk->sk_socket;
        struct tipc_msg *msg = buf_msg(buf);
        unsigned int limit = rcvbuf_limit(sk, buf);
        u32 res = TIPC_OK;

        /* 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 {
                res = filter_connect(tipc_sk(sk), &buf);
                if (res != TIPC_OK || buf == NULL)
                        return res;
        }

        /* Reject message if there isn't room to queue it */
        if (sk_rmem_alloc_get(sk) + buf->truesize >= limit)
                return TIPC_ERR_OVERLOAD;

        /* Enqueue message */
        TIPC_SKB_CB(buf)->handle = NULL;
        __skb_queue_tail(&sk->sk_receive_queue, buf);
        skb_set_owner_r(buf, sk);

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

/**
 * backlog_rcv - handle incoming message from backlog queue
 * @sk: socket
 * @buf: message
 *
 * Caller must hold socket lock, but not port lock.
 *
 * Returns 0
 */
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;
}

/**
 * dispatch - handle incoming message
 * @tport: TIPC port that received message
 * @buf: message
 *
 * Called with port lock already taken.
 *
 * Returns TIPC error status code (TIPC_OK if message is not to be rejected)
 */
static u32 dispatch(struct tipc_port *tport, struct sk_buff *buf)
{
        struct sock *sk = tport->sk;
        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, rcvbuf_limit(sk, buf)))
                        res = TIPC_ERR_OVERLOAD;
                else
                        res = TIPC_OK;
        }
        bh_unlock_sock(sk);

        return res;
}

/**
 * wakeupdispatch - wake up port after congestion
 * @tport: port to wakeup
 *
 * Called with port lock already taken.
 */
static void wakeupdispatch(struct tipc_port *tport)
{
        struct sock *sk = tport->sk;

        sk->sk_write_space(sk);
}

static int tipc_wait_for_connect(struct socket *sock, long *timeo_p)
{
        struct sock *sk = sock->sk;
        DEFINE_WAIT(wait);
        int done;

        do {
                int err = sock_error(sk);
                if (err)
                        return err;
                if (!*timeo_p)
                        return -ETIMEDOUT;
                if (signal_pending(current))
                        return sock_intr_errno(*timeo_p);

                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
                done = sk_wait_event(sk, timeo_p, sock->state != SS_CONNECTING);
                finish_wait(sk_sleep(sk), &wait);
        } while (!done);
        return 0;
}

/**
 * connect - establish a connection to another TIPC port
 * @sock: socket structure
 * @dest: socket address for destination port
 * @destlen: size of socket address data structure
 * @flags: file-related flags associated with socket
 *
 * Returns 0 on success, errno otherwise
 */
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,};
        long timeout = (flags & O_NONBLOCK) ? 0 : tipc_sk(sk)->conn_timeout;
        socket_state previous;
        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;
        }

        /*
         * 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;
        }

        previous = sock->state;
        switch (sock->state) {
        case SS_UNCONNECTED:
                /* Send a 'SYN-' to destination */
                m.msg_name = dest;
                m.msg_namelen = destlen;

                /* If connect is in non-blocking case, set MSG_DONTWAIT to
                 * indicate send_msg() is never blocked.
                 */
                if (!timeout)
                        m.msg_flags = MSG_DONTWAIT;

                res = send_msg(NULL, sock, &m, 0);
                if ((res < 0) && (res != -EWOULDBLOCK))
                        goto exit;

                /* Just entered SS_CONNECTING state; the only
                 * difference is that return value in non-blocking
                 * case is EINPROGRESS, rather than EALREADY.
                 */
                res = -EINPROGRESS;
        case SS_CONNECTING:
                if (previous == SS_CONNECTING)
                        res = -EALREADY;
                if (!timeout)
                        goto exit;
                timeout = msecs_to_jiffies(timeout);
                /* Wait until an 'ACK' or 'RST' arrives, or a timeout occurs */
                res = tipc_wait_for_connect(sock, &timeout);
                break;
        case SS_CONNECTED:
                res = -EISCONN;
                break;
        default:
                res = -EINVAL;
                break;
        }
exit:
        release_sock(sk);
        return res;
}

/**
 * listen - allow socket to listen for incoming connections
 * @sock: socket structure
 * @len: (unused)
 *
 * Returns 0 on success, errno otherwise
 */
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 tipc_wait_for_accept(struct socket *sock, long timeo)
{
        struct sock *sk = sock->sk;
        DEFINE_WAIT(wait);
        int err;

        /* True wake-one mechanism for incoming connections: only
         * one process gets woken up, not the 'whole herd'.
         * Since we do not 'race & poll' for established sockets
         * anymore, the common case will execute the loop only once.
        */
        for (;;) {
                prepare_to_wait_exclusive(sk_sleep(sk), &wait,
                                          TASK_INTERRUPTIBLE);
                if (skb_queue_empty(&sk->sk_receive_queue)) {
                        release_sock(sk);
                        timeo = schedule_timeout(timeo);
                        lock_sock(sk);
                }
                err = 0;
                if (!skb_queue_empty(&sk->sk_receive_queue))
                        break;
                err = -EINVAL;
                if (sock->state != SS_LISTENING)
                        break;
                err = sock_intr_errno(timeo);
                if (signal_pending(current))
                        break;
                err = -EAGAIN;
                if (!timeo)
                        break;
        }
        finish_wait(sk_sleep(sk), &wait);
        return err;
}

/**
 * accept - wait for connection request
 * @sock: listening socket
 * @newsock: new socket that is to be connected
 * @flags: file-related flags associated with socket
 *
 * Returns 0 on success, errno otherwise
 */
static int accept(struct socket *sock, struct socket *new_sock, int flags)
{
        struct sock *new_sk, *sk = sock->sk;
        struct sk_buff *buf;
        struct tipc_sock *new_tsock;
        struct tipc_port *new_tport;
        struct tipc_msg *msg;
        u32 new_ref;
        long timeo;
        int res;

        lock_sock(sk);

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

        timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);
        res = tipc_wait_for_accept(sock, timeo);
        if (res)
                goto exit;

        buf = skb_peek(&sk->sk_receive_queue);

        res = tipc_sk_create(sock_net(sock->sk), new_sock, 0, 1);
        if (res)
                goto exit;

        new_sk = new_sock->sk;
        new_tsock = tipc_sk(new_sk);
        new_tport = new_tsock->p;
        new_ref = new_tport->ref;
        msg = buf_msg(buf);

        /* we lock on new_sk; but lockdep sees the lock on sk */
        lock_sock_nested(new_sk, SINGLE_DEPTH_NESTING);

        /*
         * 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_connect(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);
                skb_set_owner_r(buf, new_sk);
        }
        release_sock(new_sk);

exit:
        release_sock(sk);
        return res;
}

/**
 * shutdown - shutdown socket connection
 * @sock: socket structure
 * @how: direction to close (must be SHUT_RDWR)
 *
 * Terminates connection (if necessary), then purges socket's receive queue.
 *
 * Returns 0 on success, errno otherwise
 */
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) {
                        if (TIPC_SKB_CB(buf)->handle != NULL) {
                                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 */
                __skb_queue_purge(&sk->sk_receive_queue);

                /* Wake up anyone sleeping in poll */
                sk->sk_state_change(sk);
                res = 0;
                break;

        default:
                res = -ENOTCONN;
        }

        release_sock(sk);
        return res;
}

/**
 * setsockopt - set socket option
 * @sock: socket structure
 * @lvl: option level
 * @opt: option identifier
 * @ov: pointer to new option value
 * @ol: length of option value
 *
 * For stream sockets only, accepts and ignores all IPPROTO_TCP options
 * (to ease compatibility).
 *
 * Returns 0 on success, errno otherwise
 */
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;
}

/**
 * getsockopt - get socket option
 * @sock: socket structure
 * @lvl: option level
 * @opt: option identifier
 * @ov: receptacle for option value
 * @ol: receptacle for length of option value
 *
 * For stream sockets only, returns 0 length result for all IPPROTO_TCP options
 * (to ease compatibility).
 *
 * Returns 0 on success, errno otherwise
 */
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 = 0; /* was tipc_queue_size, now obsolete */
                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_sk_create
};

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

static struct proto tipc_proto_kern = {
        .name           = "TIPC",
        .obj_size       = sizeof(struct tipc_sock),
        .sysctl_rmem    = sysctl_tipc_rmem
};

/**
 * tipc_socket_init - initialize TIPC socket interface
 *
 * Returns 0 on success, errno otherwise
 */
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;
}

/**
 * tipc_socket_stop - stop TIPC socket interface
 */
void tipc_socket_stop(void)
{
        if (!sockets_enabled)
                return;

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