// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/fs/9p/trans_fd.c
 *
 * Fd transport layer.  Includes deprecated socket layer.
 *
 *  Copyright (C) 2006 by Russ Cox <rsc@swtch.com>
 *  Copyright (C) 2004-2005 by Latchesar Ionkov <lucho@ionkov.net>
 *  Copyright (C) 2004-2008 by Eric Van Hensbergen <ericvh@gmail.com>
 *  Copyright (C) 1997-2002 by Ron Minnich <rminnich@sarnoff.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/in.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/ipv6.h>
#include <linux/kthread.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/un.h>
#include <linux/uaccess.h>
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <linux/parser.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include <net/9p/transport.h>

#include <linux/syscalls.h> /* killme */

#define P9_PORT 564
#define MAX_SOCK_BUF (1024*1024)
#define MAXPOLLWADDR    2

static struct p9_trans_module p9_tcp_trans;
static struct p9_trans_module p9_fd_trans;

/**
 * struct p9_fd_opts - per-transport options
 * @rfd: file descriptor for reading (trans=fd)
 * @wfd: file descriptor for writing (trans=fd)
 * @port: port to connect to (trans=tcp)
 * @privport: port is privileged
 */

struct p9_fd_opts {
        int rfd;
        int wfd;
        u16 port;
        bool privport;
};

/*
  * Option Parsing (code inspired by NFS code)
  *  - a little lazy - parse all fd-transport options
  */

enum {
        /* Options that take integer arguments */
        Opt_port, Opt_rfdno, Opt_wfdno, Opt_err,
        /* Options that take no arguments */
        Opt_privport,
};

static const match_table_t tokens = {
        {Opt_port, "port=%u"},
        {Opt_rfdno, "rfdno=%u"},
        {Opt_wfdno, "wfdno=%u"},
        {Opt_privport, "privport"},
        {Opt_err, NULL},
};

enum {
        Rworksched = 1,         /* read work scheduled or running */
        Rpending = 2,           /* can read */
        Wworksched = 4,         /* write work scheduled or running */
        Wpending = 8,           /* can write */
};

struct p9_poll_wait {
        struct p9_conn *conn;
        wait_queue_entry_t wait;
        wait_queue_head_t *wait_addr;
};

/**
 * struct p9_conn - fd mux connection state information
 * @mux_list: list link for mux to manage multiple connections (?)
 * @client: reference to client instance for this connection
 * @err: error state
 * @req_list: accounting for requests which have been sent
 * @unsent_req_list: accounting for requests that haven't been sent
 * @rreq: read request
 * @wreq: write request
 * @req: current request being processed (if any)
 * @tmp_buf: temporary buffer to read in header
 * @rc: temporary fcall for reading current frame
 * @wpos: write position for current frame
 * @wsize: amount of data to write for current frame
 * @wbuf: current write buffer
 * @poll_pending_link: pending links to be polled per conn
 * @poll_wait: array of wait_q's for various worker threads
 * @pt: poll state
 * @rq: current read work
 * @wq: current write work
 * @wsched: ????
 *
 */

struct p9_conn {
        struct list_head mux_list;
        struct p9_client *client;
        int err;
        struct list_head req_list;
        struct list_head unsent_req_list;
        struct p9_req_t *rreq;
        struct p9_req_t *wreq;
        char tmp_buf[7];
        struct p9_fcall rc;
        int wpos;
        int wsize;
        char *wbuf;
        struct list_head poll_pending_link;
        struct p9_poll_wait poll_wait[MAXPOLLWADDR];
        poll_table pt;
        struct work_struct rq;
        struct work_struct wq;
        unsigned long wsched;
};

/**
 * struct p9_trans_fd - transport state
 * @rd: reference to file to read from
 * @wr: reference of file to write to
 * @conn: connection state reference
 *
 */

struct p9_trans_fd {
        struct file *rd;
        struct file *wr;
        struct p9_conn conn;
};

static void p9_poll_workfn(struct work_struct *work);

static DEFINE_SPINLOCK(p9_poll_lock);
static LIST_HEAD(p9_poll_pending_list);
static DECLARE_WORK(p9_poll_work, p9_poll_workfn);

static unsigned int p9_ipport_resv_min = P9_DEF_MIN_RESVPORT;
static unsigned int p9_ipport_resv_max = P9_DEF_MAX_RESVPORT;

static void p9_mux_poll_stop(struct p9_conn *m)
{
        unsigned long flags;
        int i;

        for (i = 0; i < ARRAY_SIZE(m->poll_wait); i++) {
                struct p9_poll_wait *pwait = &m->poll_wait[i];

                if (pwait->wait_addr) {
                        remove_wait_queue(pwait->wait_addr, &pwait->wait);
                        pwait->wait_addr = NULL;
                }
        }

        spin_lock_irqsave(&p9_poll_lock, flags);
        list_del_init(&m->poll_pending_link);
        spin_unlock_irqrestore(&p9_poll_lock, flags);

        flush_work(&p9_poll_work);
}

/**
 * p9_conn_cancel - cancel all pending requests with error
 * @m: mux data
 * @err: error code
 *
 */

static void p9_conn_cancel(struct p9_conn *m, int err)
{
        struct p9_req_t *req, *rtmp;
        LIST_HEAD(cancel_list);

        p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err);

        spin_lock(&m->client->lock);

        if (m->err) {
                spin_unlock(&m->client->lock);
                return;
        }

        m->err = err;

        list_for_each_entry_safe(req, rtmp, &m->req_list, req_list) {
                list_move(&req->req_list, &cancel_list);
        }
        list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) {
                list_move(&req->req_list, &cancel_list);
        }

        list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
                p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req);
                list_del(&req->req_list);
                if (!req->t_err)
                        req->t_err = err;
                p9_client_cb(m->client, req, REQ_STATUS_ERROR);
        }
        spin_unlock(&m->client->lock);
}

static __poll_t
p9_fd_poll(struct p9_client *client, struct poll_table_struct *pt, int *err)
{
        __poll_t ret;
        struct p9_trans_fd *ts = NULL;

        if (client && client->status == Connected)
                ts = client->trans;

        if (!ts) {
                if (err)
                        *err = -EREMOTEIO;
                return EPOLLERR;
        }

        ret = vfs_poll(ts->rd, pt);
        if (ts->rd != ts->wr)
                ret = (ret & ~EPOLLOUT) | (vfs_poll(ts->wr, pt) & ~EPOLLIN);
        return ret;
}

/**
 * p9_fd_read- read from a fd
 * @client: client instance
 * @v: buffer to receive data into
 * @len: size of receive buffer
 *
 */

static int p9_fd_read(struct p9_client *client, void *v, int len)
{
        int ret;
        struct p9_trans_fd *ts = NULL;
        loff_t pos;

        if (client && client->status != Disconnected)
                ts = client->trans;

        if (!ts)
                return -EREMOTEIO;

        if (!(ts->rd->f_flags & O_NONBLOCK))
                p9_debug(P9_DEBUG_ERROR, "blocking read ...\n");

        pos = ts->rd->f_pos;
        ret = kernel_read(ts->rd, v, len, &pos);
        if (ret <= 0 && ret != -ERESTARTSYS && ret != -EAGAIN)
                client->status = Disconnected;
        return ret;
}

/**
 * p9_read_work - called when there is some data to be read from a transport
 * @work: container of work to be done
 *
 */

static void p9_read_work(struct work_struct *work)
{
        __poll_t n;
        int err;
        struct p9_conn *m;

        m = container_of(work, struct p9_conn, rq);

        if (m->err < 0)
                return;

        p9_debug(P9_DEBUG_TRANS, "start mux %p pos %zd\n", m, m->rc.offset);

        if (!m->rc.sdata) {
                m->rc.sdata = m->tmp_buf;
                m->rc.offset = 0;
                m->rc.capacity = 7; /* start by reading header */
        }

        clear_bit(Rpending, &m->wsched);
        p9_debug(P9_DEBUG_TRANS, "read mux %p pos %zd size: %zd = %zd\n",
                 m, m->rc.offset, m->rc.capacity,
                 m->rc.capacity - m->rc.offset);
        err = p9_fd_read(m->client, m->rc.sdata + m->rc.offset,
                         m->rc.capacity - m->rc.offset);
        p9_debug(P9_DEBUG_TRANS, "mux %p got %d bytes\n", m, err);
        if (err == -EAGAIN)
                goto end_clear;

        if (err <= 0)
                goto error;

        m->rc.offset += err;

        /* header read in */
        if ((!m->rreq) && (m->rc.offset == m->rc.capacity)) {
                p9_debug(P9_DEBUG_TRANS, "got new header\n");

                /* Header size */
                m->rc.size = 7;
                err = p9_parse_header(&m->rc, &m->rc.size, NULL, NULL, 0);
                if (err) {
                        p9_debug(P9_DEBUG_ERROR,
                                 "error parsing header: %d\n", err);
                        goto error;
                }

                if (m->rc.size >= m->client->msize) {
                        p9_debug(P9_DEBUG_ERROR,
                                 "requested packet size too big: %d\n",
                                 m->rc.size);
                        err = -EIO;
                        goto error;
                }

                p9_debug(P9_DEBUG_TRANS,
                         "mux %p pkt: size: %d bytes tag: %d\n",
                         m, m->rc.size, m->rc.tag);

                m->rreq = p9_tag_lookup(m->client, m->rc.tag);
                if (!m->rreq || (m->rreq->status != REQ_STATUS_SENT)) {
                        p9_debug(P9_DEBUG_ERROR, "Unexpected packet tag %d\n",
                                 m->rc.tag);
                        err = -EIO;
                        goto error;
                }

                if (!m->rreq->rc.sdata) {
                        p9_debug(P9_DEBUG_ERROR,
                                 "No recv fcall for tag %d (req %p), disconnecting!\n",
                                 m->rc.tag, m->rreq);
                        m->rreq = NULL;
                        err = -EIO;
                        goto error;
                }
                m->rc.sdata = m->rreq->rc.sdata;
                memcpy(m->rc.sdata, m->tmp_buf, m->rc.capacity);
                m->rc.capacity = m->rc.size;
        }

        /* packet is read in
         * not an else because some packets (like clunk) have no payload
         */
        if ((m->rreq) && (m->rc.offset == m->rc.capacity)) {
                p9_debug(P9_DEBUG_TRANS, "got new packet\n");
                m->rreq->rc.size = m->rc.offset;
                spin_lock(&m->client->lock);
                if (m->rreq->status == REQ_STATUS_SENT) {
                        list_del(&m->rreq->req_list);
                        p9_client_cb(m->client, m->rreq, REQ_STATUS_RCVD);
                } else if (m->rreq->status == REQ_STATUS_FLSHD) {
                        /* Ignore replies associated with a cancelled request. */
                        p9_debug(P9_DEBUG_TRANS,
                                 "Ignore replies associated with a cancelled request\n");
                } else {
                        spin_unlock(&m->client->lock);
                        p9_debug(P9_DEBUG_ERROR,
                                 "Request tag %d errored out while we were reading the reply\n",
                                 m->rc.tag);
                        err = -EIO;
                        goto error;
                }
                spin_unlock(&m->client->lock);
                m->rc.sdata = NULL;
                m->rc.offset = 0;
                m->rc.capacity = 0;
                p9_req_put(m->rreq);
                m->rreq = NULL;
        }

end_clear:
        clear_bit(Rworksched, &m->wsched);

        if (!list_empty(&m->req_list)) {
                if (test_and_clear_bit(Rpending, &m->wsched))
                        n = EPOLLIN;
                else
                        n = p9_fd_poll(m->client, NULL, NULL);

                if ((n & EPOLLIN) && !test_and_set_bit(Rworksched, &m->wsched)) {
                        p9_debug(P9_DEBUG_TRANS, "sched read work %p\n", m);
                        schedule_work(&m->rq);
                }
        }

        return;
error:
        p9_conn_cancel(m, err);
        clear_bit(Rworksched, &m->wsched);
}

/**
 * p9_fd_write - write to a socket
 * @client: client instance
 * @v: buffer to send data from
 * @len: size of send buffer
 *
 */

static int p9_fd_write(struct p9_client *client, void *v, int len)
{
        ssize_t ret;
        struct p9_trans_fd *ts = NULL;

        if (client && client->status != Disconnected)
                ts = client->trans;

        if (!ts)
                return -EREMOTEIO;

        if (!(ts->wr->f_flags & O_NONBLOCK))
                p9_debug(P9_DEBUG_ERROR, "blocking write ...\n");

        ret = kernel_write(ts->wr, v, len, &ts->wr->f_pos);
        if (ret <= 0 && ret != -ERESTARTSYS && ret != -EAGAIN)
                client->status = Disconnected;
        return ret;
}

/**
 * p9_write_work - called when a transport can send some data
 * @work: container for work to be done
 *
 */

static void p9_write_work(struct work_struct *work)
{
        __poll_t n;
        int err;
        struct p9_conn *m;
        struct p9_req_t *req;

        m = container_of(work, struct p9_conn, wq);

        if (m->err < 0) {
                clear_bit(Wworksched, &m->wsched);
                return;
        }

        if (!m->wsize) {
                spin_lock(&m->client->lock);
                if (list_empty(&m->unsent_req_list)) {
                        clear_bit(Wworksched, &m->wsched);
                        spin_unlock(&m->client->lock);
                        return;
                }

                req = list_entry(m->unsent_req_list.next, struct p9_req_t,
                               req_list);
                req->status = REQ_STATUS_SENT;
                p9_debug(P9_DEBUG_TRANS, "move req %p\n", req);
                list_move_tail(&req->req_list, &m->req_list);

                m->wbuf = req->tc.sdata;
                m->wsize = req->tc.size;
                m->wpos = 0;
                p9_req_get(req);
                m->wreq = req;
                spin_unlock(&m->client->lock);
        }

        p9_debug(P9_DEBUG_TRANS, "mux %p pos %d size %d\n",
                 m, m->wpos, m->wsize);
        clear_bit(Wpending, &m->wsched);
        err = p9_fd_write(m->client, m->wbuf + m->wpos, m->wsize - m->wpos);
        p9_debug(P9_DEBUG_TRANS, "mux %p sent %d bytes\n", m, err);
        if (err == -EAGAIN)
                goto end_clear;


        if (err < 0)
                goto error;
        else if (err == 0) {
                err = -EREMOTEIO;
                goto error;
        }

        m->wpos += err;
        if (m->wpos == m->wsize) {
                m->wpos = m->wsize = 0;
                p9_req_put(m->wreq);
                m->wreq = NULL;
        }

end_clear:
        clear_bit(Wworksched, &m->wsched);

        if (m->wsize || !list_empty(&m->unsent_req_list)) {
                if (test_and_clear_bit(Wpending, &m->wsched))
                        n = EPOLLOUT;
                else
                        n = p9_fd_poll(m->client, NULL, NULL);

                if ((n & EPOLLOUT) &&
                   !test_and_set_bit(Wworksched, &m->wsched)) {
                        p9_debug(P9_DEBUG_TRANS, "sched write work %p\n", m);
                        schedule_work(&m->wq);
                }
        }

        return;

error:
        p9_conn_cancel(m, err);
        clear_bit(Wworksched, &m->wsched);
}

static int p9_pollwake(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key)
{
        struct p9_poll_wait *pwait =
                container_of(wait, struct p9_poll_wait, wait);
        struct p9_conn *m = pwait->conn;
        unsigned long flags;

        spin_lock_irqsave(&p9_poll_lock, flags);
        if (list_empty(&m->poll_pending_link))
                list_add_tail(&m->poll_pending_link, &p9_poll_pending_list);
        spin_unlock_irqrestore(&p9_poll_lock, flags);

        schedule_work(&p9_poll_work);
        return 1;
}

/**
 * p9_pollwait - add poll task to the wait queue
 * @filp: file pointer being polled
 * @wait_address: wait_q to block on
 * @p: poll state
 *
 * called by files poll operation to add v9fs-poll task to files wait queue
 */

static void
p9_pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *p)
{
        struct p9_conn *m = container_of(p, struct p9_conn, pt);
        struct p9_poll_wait *pwait = NULL;
        int i;

        for (i = 0; i < ARRAY_SIZE(m->poll_wait); i++) {
                if (m->poll_wait[i].wait_addr == NULL) {
                        pwait = &m->poll_wait[i];
                        break;
                }
        }

        if (!pwait) {
                p9_debug(P9_DEBUG_ERROR, "not enough wait_address slots\n");
                return;
        }

        pwait->conn = m;
        pwait->wait_addr = wait_address;
        init_waitqueue_func_entry(&pwait->wait, p9_pollwake);
        add_wait_queue(wait_address, &pwait->wait);
}

/**
 * p9_conn_create - initialize the per-session mux data
 * @client: client instance
 *
 * Note: Creates the polling task if this is the first session.
 */

static void p9_conn_create(struct p9_client *client)
{
        __poll_t n;
        struct p9_trans_fd *ts = client->trans;
        struct p9_conn *m = &ts->conn;

        p9_debug(P9_DEBUG_TRANS, "client %p msize %d\n", client, client->msize);

        INIT_LIST_HEAD(&m->mux_list);
        m->client = client;

        INIT_LIST_HEAD(&m->req_list);
        INIT_LIST_HEAD(&m->unsent_req_list);
        INIT_WORK(&m->rq, p9_read_work);
        INIT_WORK(&m->wq, p9_write_work);
        INIT_LIST_HEAD(&m->poll_pending_link);
        init_poll_funcptr(&m->pt, p9_pollwait);

        n = p9_fd_poll(client, &m->pt, NULL);
        if (n & EPOLLIN) {
                p9_debug(P9_DEBUG_TRANS, "mux %p can read\n", m);
                set_bit(Rpending, &m->wsched);
        }

        if (n & EPOLLOUT) {
                p9_debug(P9_DEBUG_TRANS, "mux %p can write\n", m);
                set_bit(Wpending, &m->wsched);
        }
}

/**
 * p9_poll_mux - polls a mux and schedules read or write works if necessary
 * @m: connection to poll
 *
 */

static void p9_poll_mux(struct p9_conn *m)
{
        __poll_t n;
        int err = -ECONNRESET;

        if (m->err < 0)
                return;

        n = p9_fd_poll(m->client, NULL, &err);
        if (n & (EPOLLERR | EPOLLHUP | EPOLLNVAL)) {
                p9_debug(P9_DEBUG_TRANS, "error mux %p err %d\n", m, n);
                p9_conn_cancel(m, err);
        }

        if (n & EPOLLIN) {
                set_bit(Rpending, &m->wsched);
                p9_debug(P9_DEBUG_TRANS, "mux %p can read\n", m);
                if (!test_and_set_bit(Rworksched, &m->wsched)) {
                        p9_debug(P9_DEBUG_TRANS, "sched read work %p\n", m);
                        schedule_work(&m->rq);
                }
        }

        if (n & EPOLLOUT) {
                set_bit(Wpending, &m->wsched);
                p9_debug(P9_DEBUG_TRANS, "mux %p can write\n", m);
                if ((m->wsize || !list_empty(&m->unsent_req_list)) &&
                    !test_and_set_bit(Wworksched, &m->wsched)) {
                        p9_debug(P9_DEBUG_TRANS, "sched write work %p\n", m);
                        schedule_work(&m->wq);
                }
        }
}

/**
 * p9_fd_request - send 9P request
 * The function can sleep until the request is scheduled for sending.
 * The function can be interrupted. Return from the function is not
 * a guarantee that the request is sent successfully.
 *
 * @client: client instance
 * @req: request to be sent
 *
 */

static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)
{
        __poll_t n;
        struct p9_trans_fd *ts = client->trans;
        struct p9_conn *m = &ts->conn;

        p9_debug(P9_DEBUG_TRANS, "mux %p task %p tcall %p id %d\n",
                 m, current, &req->tc, req->tc.id);
        if (m->err < 0)
                return m->err;

        spin_lock(&client->lock);
        req->status = REQ_STATUS_UNSENT;
        list_add_tail(&req->req_list, &m->unsent_req_list);
        spin_unlock(&client->lock);

        if (test_and_clear_bit(Wpending, &m->wsched))
                n = EPOLLOUT;
        else
                n = p9_fd_poll(m->client, NULL, NULL);

        if (n & EPOLLOUT && !test_and_set_bit(Wworksched, &m->wsched))
                schedule_work(&m->wq);

        return 0;
}

static int p9_fd_cancel(struct p9_client *client, struct p9_req_t *req)
{
        int ret = 1;

        p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);

        spin_lock(&client->lock);

        if (req->status == REQ_STATUS_UNSENT) {
                list_del(&req->req_list);
                req->status = REQ_STATUS_FLSHD;
                p9_req_put(req);
                ret = 0;
        }
        spin_unlock(&client->lock);

        return ret;
}

static int p9_fd_cancelled(struct p9_client *client, struct p9_req_t *req)
{
        p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);

        spin_lock(&client->lock);
        /* Ignore cancelled request if message has been received
         * before lock.
         */
        if (req->status == REQ_STATUS_RCVD) {
                spin_unlock(&client->lock);
                return 0;
        }

        /* we haven't received a response for oldreq,
         * remove it from the list.
         */
        list_del(&req->req_list);
        req->status = REQ_STATUS_FLSHD;
        spin_unlock(&client->lock);
        p9_req_put(req);

        return 0;
}

static int p9_fd_show_options(struct seq_file *m, struct p9_client *clnt)
{
        if (clnt->trans_mod == &p9_tcp_trans) {
                if (clnt->trans_opts.tcp.port != P9_PORT)
                        seq_printf(m, ",port=%u", clnt->trans_opts.tcp.port);
        } else if (clnt->trans_mod == &p9_fd_trans) {
                if (clnt->trans_opts.fd.rfd != ~0)
                        seq_printf(m, ",rfd=%u", clnt->trans_opts.fd.rfd);
                if (clnt->trans_opts.fd.wfd != ~0)
                        seq_printf(m, ",wfd=%u", clnt->trans_opts.fd.wfd);
        }
        return 0;
}

/**
 * parse_opts - parse mount options into p9_fd_opts structure
 * @params: options string passed from mount
 * @opts: fd transport-specific structure to parse options into
 *
 * Returns 0 upon success, -ERRNO upon failure
 */

static int parse_opts(char *params, struct p9_fd_opts *opts)
{
        char *p;
        substring_t args[MAX_OPT_ARGS];
        int option;
        char *options, *tmp_options;

        opts->port = P9_PORT;
        opts->rfd = ~0;
        opts->wfd = ~0;
        opts->privport = false;

        if (!params)
                return 0;

        tmp_options = kstrdup(params, GFP_KERNEL);
        if (!tmp_options) {
                p9_debug(P9_DEBUG_ERROR,
                         "failed to allocate copy of option string\n");
                return -ENOMEM;
        }
        options = tmp_options;

        while ((p = strsep(&options, ",")) != NULL) {
                int token;
                int r;
                if (!*p)
                        continue;
                token = match_token(p, tokens, args);
                if ((token != Opt_err) && (token != Opt_privport)) {
                        r = match_int(&args[0], &option);
                        if (r < 0) {
                                p9_debug(P9_DEBUG_ERROR,
                                         "integer field, but no integer?\n");
                                continue;
                        }
                }
                switch (token) {
                case Opt_port:
                        opts->port = option;
                        break;
                case Opt_rfdno:
                        opts->rfd = option;
                        break;
                case Opt_wfdno:
                        opts->wfd = option;
                        break;
                case Opt_privport:
                        opts->privport = true;
                        break;
                default:
                        continue;
                }
        }

        kfree(tmp_options);
        return 0;
}

static int p9_fd_open(struct p9_client *client, int rfd, int wfd)
{
        struct p9_trans_fd *ts = kzalloc(sizeof(struct p9_trans_fd),
                                           GFP_KERNEL);
        if (!ts)
                return -ENOMEM;

        ts->rd = fget(rfd);
        if (!ts->rd)
                goto out_free_ts;
        if (!(ts->rd->f_mode & FMODE_READ))
                goto out_put_rd;
        ts->wr = fget(wfd);
        if (!ts->wr)
                goto out_put_rd;
        if (!(ts->wr->f_mode & FMODE_WRITE))
                goto out_put_wr;

        client->trans = ts;
        client->status = Connected;

        return 0;

out_put_wr:
        fput(ts->wr);
out_put_rd:
        fput(ts->rd);
out_free_ts:
        kfree(ts);
        return -EIO;
}

static int p9_socket_open(struct p9_client *client, struct socket *csocket)
{
        struct p9_trans_fd *p;
        struct file *file;

        p = kzalloc(sizeof(struct p9_trans_fd), GFP_KERNEL);
        if (!p)
                return -ENOMEM;

        csocket->sk->sk_allocation = GFP_NOIO;
        file = sock_alloc_file(csocket, 0, NULL);
        if (IS_ERR(file)) {
                pr_err("%s (%d): failed to map fd\n",
                       __func__, task_pid_nr(current));
                kfree(p);
                return PTR_ERR(file);
        }

        get_file(file);
        p->wr = p->rd = file;
        client->trans = p;
        client->status = Connected;

        p->rd->f_flags |= O_NONBLOCK;

        p9_conn_create(client);
        return 0;
}

/**
 * p9_conn_destroy - cancels all pending requests of mux
 * @m: mux to destroy
 *
 */

static void p9_conn_destroy(struct p9_conn *m)
{
        p9_debug(P9_DEBUG_TRANS, "mux %p prev %p next %p\n",
                 m, m->mux_list.prev, m->mux_list.next);

        p9_mux_poll_stop(m);
        cancel_work_sync(&m->rq);
        if (m->rreq) {
                p9_req_put(m->rreq);
                m->rreq = NULL;
        }
        cancel_work_sync(&m->wq);
        if (m->wreq) {
                p9_req_put(m->wreq);
                m->wreq = NULL;
        }

        p9_conn_cancel(m, -ECONNRESET);

        m->client = NULL;
}

/**
 * p9_fd_close - shutdown file descriptor transport
 * @client: client instance
 *
 */

static void p9_fd_close(struct p9_client *client)
{
        struct p9_trans_fd *ts;

        if (!client)
                return;

        ts = client->trans;
        if (!ts)
                return;

        client->status = Disconnected;

        p9_conn_destroy(&ts->conn);

        if (ts->rd)
                fput(ts->rd);
        if (ts->wr)
                fput(ts->wr);

        kfree(ts);
}

/*
 * stolen from NFS - maybe should be made a generic function?
 */
static inline int valid_ipaddr4(const char *buf)
{
        int rc, count, in[4];

        rc = sscanf(buf, "%d.%d.%d.%d", &in[0], &in[1], &in[2], &in[3]);
        if (rc != 4)
                return -EINVAL;
        for (count = 0; count < 4; count++) {
                if (in[count] > 255)
                        return -EINVAL;
        }
        return 0;
}

static int p9_bind_privport(struct socket *sock)
{
        struct sockaddr_in cl;
        int port, err = -EINVAL;

        memset(&cl, 0, sizeof(cl));
        cl.sin_family = AF_INET;
        cl.sin_addr.s_addr = htonl(INADDR_ANY);
        for (port = p9_ipport_resv_max; port >= p9_ipport_resv_min; port--) {
                cl.sin_port = htons((ushort)port);
                err = kernel_bind(sock, (struct sockaddr *)&cl, sizeof(cl));
                if (err != -EADDRINUSE)
                        break;
        }
        return err;
}


static int
p9_fd_create_tcp(struct p9_client *client, const char *addr, char *args)
{
        int err;
        struct socket *csocket;
        struct sockaddr_in sin_server;
        struct p9_fd_opts opts;

        err = parse_opts(args, &opts);
        if (err < 0)
                return err;

        if (addr == NULL || valid_ipaddr4(addr) < 0)
                return -EINVAL;

        csocket = NULL;

        client->trans_opts.tcp.port = opts.port;
        client->trans_opts.tcp.privport = opts.privport;
        sin_server.sin_family = AF_INET;
        sin_server.sin_addr.s_addr = in_aton(addr);
        sin_server.sin_port = htons(opts.port);
        err = __sock_create(current->nsproxy->net_ns, PF_INET,
                            SOCK_STREAM, IPPROTO_TCP, &csocket, 1);
        if (err) {
                pr_err("%s (%d): problem creating socket\n",
                       __func__, task_pid_nr(current));
                return err;
        }

        if (opts.privport) {
                err = p9_bind_privport(csocket);
                if (err < 0) {
                        pr_err("%s (%d): problem binding to privport\n",
                               __func__, task_pid_nr(current));

                        sock_release(csocket);
                        return err;
                }
        }

        err = csocket->ops->connect(csocket,
                                    (struct sockaddr *)&sin_server,
                                    sizeof(struct sockaddr_in), 0);
        if (err < 0) {
                pr_err("%s (%d): problem connecting socket to %s\n",
                       __func__, task_pid_nr(current), addr);
                sock_release(csocket);
                return err;
        }

        return p9_socket_open(client, csocket);
}

static int
p9_fd_create_unix(struct p9_client *client, const char *addr, char *args)
{
        int err;
        struct socket *csocket;
        struct sockaddr_un sun_server;

        csocket = NULL;

        if (!addr || !strlen(addr))
                return -EINVAL;

        if (strlen(addr) >= UNIX_PATH_MAX) {
                pr_err("%s (%d): address too long: %s\n",
                       __func__, task_pid_nr(current), addr);
                return -ENAMETOOLONG;
        }

        sun_server.sun_family = PF_UNIX;
        strcpy(sun_server.sun_path, addr);
        err = __sock_create(current->nsproxy->net_ns, PF_UNIX,
                            SOCK_STREAM, 0, &csocket, 1);
        if (err < 0) {
                pr_err("%s (%d): problem creating socket\n",
                       __func__, task_pid_nr(current));

                return err;
        }
        err = csocket->ops->connect(csocket, (struct sockaddr *)&sun_server,
                        sizeof(struct sockaddr_un) - 1, 0);
        if (err < 0) {
                pr_err("%s (%d): problem connecting socket: %s: %d\n",
                       __func__, task_pid_nr(current), addr, err);
                sock_release(csocket);
                return err;
        }

        return p9_socket_open(client, csocket);
}

static int
p9_fd_create(struct p9_client *client, const char *addr, char *args)
{
        int err;
        struct p9_fd_opts opts;

        parse_opts(args, &opts);
        client->trans_opts.fd.rfd = opts.rfd;
        client->trans_opts.fd.wfd = opts.wfd;

        if (opts.rfd == ~0 || opts.wfd == ~0) {
                pr_err("Insufficient options for proto=fd\n");
                return -ENOPROTOOPT;
        }

        err = p9_fd_open(client, opts.rfd, opts.wfd);
        if (err < 0)
                return err;

        p9_conn_create(client);

        return 0;
}

static struct p9_trans_module p9_tcp_trans = {
        .name = "tcp",
        .maxsize = MAX_SOCK_BUF,
        .def = 0,
        .create = p9_fd_create_tcp,
        .close = p9_fd_close,
        .request = p9_fd_request,
        .cancel = p9_fd_cancel,
        .cancelled = p9_fd_cancelled,
        .show_options = p9_fd_show_options,
        .owner = THIS_MODULE,
};

static struct p9_trans_module p9_unix_trans = {
        .name = "unix",
        .maxsize = MAX_SOCK_BUF,
        .def = 0,
        .create = p9_fd_create_unix,
        .close = p9_fd_close,
        .request = p9_fd_request,
        .cancel = p9_fd_cancel,
        .cancelled = p9_fd_cancelled,
        .show_options = p9_fd_show_options,
        .owner = THIS_MODULE,
};

static struct p9_trans_module p9_fd_trans = {
        .name = "fd",
        .maxsize = MAX_SOCK_BUF,
        .def = 0,
        .create = p9_fd_create,
        .close = p9_fd_close,
        .request = p9_fd_request,
        .cancel = p9_fd_cancel,
        .cancelled = p9_fd_cancelled,
        .show_options = p9_fd_show_options,
        .owner = THIS_MODULE,
};

/**
 * p9_poll_workfn - poll worker thread
 * @work: work queue
 *
 * polls all v9fs transports for new events and queues the appropriate
 * work to the work queue
 *
 */

static void p9_poll_workfn(struct work_struct *work)
{
        unsigned long flags;

        p9_debug(P9_DEBUG_TRANS, "start %p\n", current);

        spin_lock_irqsave(&p9_poll_lock, flags);
        while (!list_empty(&p9_poll_pending_list)) {
                struct p9_conn *conn = list_first_entry(&p9_poll_pending_list,
                                                        struct p9_conn,
                                                        poll_pending_link);
                list_del_init(&conn->poll_pending_link);
                spin_unlock_irqrestore(&p9_poll_lock, flags);

                p9_poll_mux(conn);

                spin_lock_irqsave(&p9_poll_lock, flags);
        }
        spin_unlock_irqrestore(&p9_poll_lock, flags);

        p9_debug(P9_DEBUG_TRANS, "finish\n");
}

int p9_trans_fd_init(void)
{
        v9fs_register_trans(&p9_tcp_trans);
        v9fs_register_trans(&p9_unix_trans);
        v9fs_register_trans(&p9_fd_trans);

        return 0;
}

void p9_trans_fd_exit(void)
{
        flush_work(&p9_poll_work);
        v9fs_unregister_trans(&p9_tcp_trans);
        v9fs_unregister_trans(&p9_unix_trans);
        v9fs_unregister_trans(&p9_fd_trans);
}