SUNRPC: Refactor TCP receive

[mirror_ubuntu-bionic-kernel.git] / net / sunrpc / xprtsock.c

/*
 * linux/net/sunrpc/xprtsock.c
 *
 * Client-side transport implementation for sockets.
 *
 * TCP callback races fixes (C) 1998 Red Hat
 * TCP send fixes (C) 1998 Red Hat
 * TCP NFS related read + write fixes
 *  (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
 *
 * Rewrite of larges part of the code in order to stabilize TCP stuff.
 * Fix behaviour when socket buffer is full.
 *  (C) 1999 Trond Myklebust <trond.myklebust@fys.uio.no>
 *
 * IP socket transport implementation, (C) 2005 Chuck Lever <cel@netapp.com>
 *
 * IPv6 support contributed by Gilles Quillard, Bull Open Source, 2005.
 *   <gilles.quillard@bull.net>
 */

#include <linux/types.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/capability.h>
#include <linux/pagemap.h>
#include <linux/errno.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/net.h>
#include <linux/mm.h>
#include <linux/un.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/sched.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/sunrpc/xprtsock.h>
#include <linux/file.h>
#ifdef CONFIG_SUNRPC_BACKCHANNEL
#include <linux/sunrpc/bc_xprt.h>
#endif

#include <net/sock.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <net/tcp.h>

#include <trace/events/sunrpc.h>

#include "sunrpc.h"

static void xs_close(struct rpc_xprt *xprt);

/*
 * xprtsock tunables
 */
static unsigned int xprt_udp_slot_table_entries = RPC_DEF_SLOT_TABLE;
static unsigned int xprt_tcp_slot_table_entries = RPC_MIN_SLOT_TABLE;
static unsigned int xprt_max_tcp_slot_table_entries = RPC_MAX_SLOT_TABLE;

static unsigned int xprt_min_resvport = RPC_DEF_MIN_RESVPORT;
static unsigned int xprt_max_resvport = RPC_DEF_MAX_RESVPORT;

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)

#define XS_TCP_LINGER_TO        (15U * HZ)
static unsigned int xs_tcp_fin_timeout __read_mostly = XS_TCP_LINGER_TO;

/*
 * We can register our own files under /proc/sys/sunrpc by
 * calling register_sysctl_table() again.  The files in that
 * directory become the union of all files registered there.
 *
 * We simply need to make sure that we don't collide with
 * someone else's file names!
 */

static unsigned int min_slot_table_size = RPC_MIN_SLOT_TABLE;
static unsigned int max_slot_table_size = RPC_MAX_SLOT_TABLE;
static unsigned int max_tcp_slot_table_limit = RPC_MAX_SLOT_TABLE_LIMIT;
static unsigned int xprt_min_resvport_limit = RPC_MIN_RESVPORT;
static unsigned int xprt_max_resvport_limit = RPC_MAX_RESVPORT;

static struct ctl_table_header *sunrpc_table_header;

/*
 * FIXME: changing the UDP slot table size should also resize the UDP
 *        socket buffers for existing UDP transports
 */
static struct ctl_table xs_tunables_table[] = {
        {
                .procname       = "udp_slot_table_entries",
                .data           = &xprt_udp_slot_table_entries,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = &min_slot_table_size,
                .extra2         = &max_slot_table_size
        },
        {
                .procname       = "tcp_slot_table_entries",
                .data           = &xprt_tcp_slot_table_entries,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = &min_slot_table_size,
                .extra2         = &max_slot_table_size
        },
        {
                .procname       = "tcp_max_slot_table_entries",
                .data           = &xprt_max_tcp_slot_table_entries,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = &min_slot_table_size,
                .extra2         = &max_tcp_slot_table_limit
        },
        {
                .procname       = "min_resvport",
                .data           = &xprt_min_resvport,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = &xprt_min_resvport_limit,
                .extra2         = &xprt_max_resvport_limit
        },
        {
                .procname       = "max_resvport",
                .data           = &xprt_max_resvport,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = &xprt_min_resvport_limit,
                .extra2         = &xprt_max_resvport_limit
        },
        {
                .procname       = "tcp_fin_timeout",
                .data           = &xs_tcp_fin_timeout,
                .maxlen         = sizeof(xs_tcp_fin_timeout),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        { },
};

static struct ctl_table sunrpc_table[] = {
        {
                .procname       = "sunrpc",
                .mode           = 0555,
                .child          = xs_tunables_table
        },
        { },
};

#endif

/*
 * Wait duration for a reply from the RPC portmapper.
 */
#define XS_BIND_TO              (60U * HZ)

/*
 * Delay if a UDP socket connect error occurs.  This is most likely some
 * kind of resource problem on the local host.
 */
#define XS_UDP_REEST_TO         (2U * HZ)

/*
 * The reestablish timeout allows clients to delay for a bit before attempting
 * to reconnect to a server that just dropped our connection.
 *
 * We implement an exponential backoff when trying to reestablish a TCP
 * transport connection with the server.  Some servers like to drop a TCP
 * connection when they are overworked, so we start with a short timeout and
 * increase over time if the server is down or not responding.
 */
#define XS_TCP_INIT_REEST_TO    (3U * HZ)
#define XS_TCP_MAX_REEST_TO     (5U * 60 * HZ)

/*
 * TCP idle timeout; client drops the transport socket if it is idle
 * for this long.  Note that we also timeout UDP sockets to prevent
 * holding port numbers when there is no RPC traffic.
 */
#define XS_IDLE_DISC_TO         (5U * 60 * HZ)

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# undef  RPC_DEBUG_DATA
# define RPCDBG_FACILITY        RPCDBG_TRANS
#endif

#ifdef RPC_DEBUG_DATA
static void xs_pktdump(char *msg, u32 *packet, unsigned int count)
{
        u8 *buf = (u8 *) packet;
        int j;

        dprintk("RPC:       %s\n", msg);
        for (j = 0; j < count && j < 128; j += 4) {
                if (!(j & 31)) {
                        if (j)
                                dprintk("\n");
                        dprintk("0x%04x ", j);
                }
                dprintk("%02x%02x%02x%02x ",
                        buf[j], buf[j+1], buf[j+2], buf[j+3]);
        }
        dprintk("\n");
}
#else
static inline void xs_pktdump(char *msg, u32 *packet, unsigned int count)
{
        /* NOP */
}
#endif

static inline struct rpc_xprt *xprt_from_sock(struct sock *sk)
{
        return (struct rpc_xprt *) sk->sk_user_data;
}

static inline struct sockaddr *xs_addr(struct rpc_xprt *xprt)
{
        return (struct sockaddr *) &xprt->addr;
}

static inline struct sockaddr_un *xs_addr_un(struct rpc_xprt *xprt)
{
        return (struct sockaddr_un *) &xprt->addr;
}

static inline struct sockaddr_in *xs_addr_in(struct rpc_xprt *xprt)
{
        return (struct sockaddr_in *) &xprt->addr;
}

static inline struct sockaddr_in6 *xs_addr_in6(struct rpc_xprt *xprt)
{
        return (struct sockaddr_in6 *) &xprt->addr;
}

static void xs_format_common_peer_addresses(struct rpc_xprt *xprt)
{
        struct sockaddr *sap = xs_addr(xprt);
        struct sockaddr_in6 *sin6;
        struct sockaddr_in *sin;
        struct sockaddr_un *sun;
        char buf[128];

        switch (sap->sa_family) {
        case AF_LOCAL:
                sun = xs_addr_un(xprt);
                strlcpy(buf, sun->sun_path, sizeof(buf));
                xprt->address_strings[RPC_DISPLAY_ADDR] =
                                                kstrdup(buf, GFP_KERNEL);
                break;
        case AF_INET:
                (void)rpc_ntop(sap, buf, sizeof(buf));
                xprt->address_strings[RPC_DISPLAY_ADDR] =
                                                kstrdup(buf, GFP_KERNEL);
                sin = xs_addr_in(xprt);
                snprintf(buf, sizeof(buf), "%08x", ntohl(sin->sin_addr.s_addr));
                break;
        case AF_INET6:
                (void)rpc_ntop(sap, buf, sizeof(buf));
                xprt->address_strings[RPC_DISPLAY_ADDR] =
                                                kstrdup(buf, GFP_KERNEL);
                sin6 = xs_addr_in6(xprt);
                snprintf(buf, sizeof(buf), "%pi6", &sin6->sin6_addr);
                break;
        default:
                BUG();
        }

        xprt->address_strings[RPC_DISPLAY_HEX_ADDR] = kstrdup(buf, GFP_KERNEL);
}

static void xs_format_common_peer_ports(struct rpc_xprt *xprt)
{
        struct sockaddr *sap = xs_addr(xprt);
        char buf[128];

        snprintf(buf, sizeof(buf), "%u", rpc_get_port(sap));
        xprt->address_strings[RPC_DISPLAY_PORT] = kstrdup(buf, GFP_KERNEL);

        snprintf(buf, sizeof(buf), "%4hx", rpc_get_port(sap));
        xprt->address_strings[RPC_DISPLAY_HEX_PORT] = kstrdup(buf, GFP_KERNEL);
}

static void xs_format_peer_addresses(struct rpc_xprt *xprt,
                                     const char *protocol,
                                     const char *netid)
{
        xprt->address_strings[RPC_DISPLAY_PROTO] = protocol;
        xprt->address_strings[RPC_DISPLAY_NETID] = netid;
        xs_format_common_peer_addresses(xprt);
        xs_format_common_peer_ports(xprt);
}

static void xs_update_peer_port(struct rpc_xprt *xprt)
{
        kfree(xprt->address_strings[RPC_DISPLAY_HEX_PORT]);
        kfree(xprt->address_strings[RPC_DISPLAY_PORT]);

        xs_format_common_peer_ports(xprt);
}

static void xs_free_peer_addresses(struct rpc_xprt *xprt)
{
        unsigned int i;

        for (i = 0; i < RPC_DISPLAY_MAX; i++)
                switch (i) {
                case RPC_DISPLAY_PROTO:
                case RPC_DISPLAY_NETID:
                        continue;
                default:
                        kfree(xprt->address_strings[i]);
                }
}

#define XS_SENDMSG_FLAGS        (MSG_DONTWAIT | MSG_NOSIGNAL)

static int xs_send_kvec(struct socket *sock, struct sockaddr *addr, int addrlen, struct kvec *vec, unsigned int base, int more)
{
        struct msghdr msg = {
                .msg_name       = addr,
                .msg_namelen    = addrlen,
                .msg_flags      = XS_SENDMSG_FLAGS | (more ? MSG_MORE : 0),
        };
        struct kvec iov = {
                .iov_base       = vec->iov_base + base,
                .iov_len        = vec->iov_len - base,
        };

        if (iov.iov_len != 0)
                return kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len);
        return kernel_sendmsg(sock, &msg, NULL, 0, 0);
}

static int xs_send_pagedata(struct socket *sock, struct xdr_buf *xdr, unsigned int base, int more, bool zerocopy, int *sent_p)
{
        ssize_t (*do_sendpage)(struct socket *sock, struct page *page,
                        int offset, size_t size, int flags);
        struct page **ppage;
        unsigned int remainder;
        int err;

        remainder = xdr->page_len - base;
        base += xdr->page_base;
        ppage = xdr->pages + (base >> PAGE_SHIFT);
        base &= ~PAGE_MASK;
        do_sendpage = sock->ops->sendpage;
        if (!zerocopy)
                do_sendpage = sock_no_sendpage;
        for(;;) {
                unsigned int len = min_t(unsigned int, PAGE_SIZE - base, remainder);
                int flags = XS_SENDMSG_FLAGS;

                remainder -= len;
                if (remainder != 0 || more)
                        flags |= MSG_MORE;
                err = do_sendpage(sock, *ppage, base, len, flags);
                if (remainder == 0 || err != len)
                        break;
                *sent_p += err;
                ppage++;
                base = 0;
        }
        if (err > 0) {
                *sent_p += err;
                err = 0;
        }
        return err;
}

/**
 * xs_sendpages - write pages directly to a socket
 * @sock: socket to send on
 * @addr: UDP only -- address of destination
 * @addrlen: UDP only -- length of destination address
 * @xdr: buffer containing this request
 * @base: starting position in the buffer
 * @zerocopy: true if it is safe to use sendpage()
 * @sent_p: return the total number of bytes successfully queued for sending
 *
 */
static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base, bool zerocopy, int *sent_p)
{
        unsigned int remainder = xdr->len - base;
        int err = 0;
        int sent = 0;

        if (unlikely(!sock))
                return -ENOTSOCK;

        clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
        if (base != 0) {
                addr = NULL;
                addrlen = 0;
        }

        if (base < xdr->head[0].iov_len || addr != NULL) {
                unsigned int len = xdr->head[0].iov_len - base;
                remainder -= len;
                err = xs_send_kvec(sock, addr, addrlen, &xdr->head[0], base, remainder != 0);
                if (remainder == 0 || err != len)
                        goto out;
                *sent_p += err;
                base = 0;
        } else
                base -= xdr->head[0].iov_len;

        if (base < xdr->page_len) {
                unsigned int len = xdr->page_len - base;
                remainder -= len;
                err = xs_send_pagedata(sock, xdr, base, remainder != 0, zerocopy, &sent);
                *sent_p += sent;
                if (remainder == 0 || sent != len)
                        goto out;
                base = 0;
        } else
                base -= xdr->page_len;

        if (base >= xdr->tail[0].iov_len)
                return 0;
        err = xs_send_kvec(sock, NULL, 0, &xdr->tail[0], base, 0);
out:
        if (err > 0) {
                *sent_p += err;
                err = 0;
        }
        return err;
}

static void xs_nospace_callback(struct rpc_task *task)
{
        struct sock_xprt *transport = container_of(task->tk_rqstp->rq_xprt, struct sock_xprt, xprt);

        transport->inet->sk_write_pending--;
        clear_bit(SOCK_ASYNC_NOSPACE, &transport->sock->flags);
}

/**
 * xs_nospace - place task on wait queue if transmit was incomplete
 * @task: task to put to sleep
 *
 */
static int xs_nospace(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        struct sock *sk = transport->inet;
        int ret = -EAGAIN;

        dprintk("RPC: %5u xmit incomplete (%u left of %u)\n",
                        task->tk_pid, req->rq_slen - req->rq_bytes_sent,
                        req->rq_slen);

        /* Protect against races with write_space */
        spin_lock_bh(&xprt->transport_lock);

        /* Don't race with disconnect */
        if (xprt_connected(xprt)) {
                if (test_bit(SOCK_ASYNC_NOSPACE, &transport->sock->flags)) {
                        /*
                         * Notify TCP that we're limited by the application
                         * window size
                         */
                        set_bit(SOCK_NOSPACE, &transport->sock->flags);
                        sk->sk_write_pending++;
                        /* ...and wait for more buffer space */
                        xprt_wait_for_buffer_space(task, xs_nospace_callback);
                }
        } else {
                clear_bit(SOCK_ASYNC_NOSPACE, &transport->sock->flags);
                ret = -ENOTCONN;
        }

        spin_unlock_bh(&xprt->transport_lock);

        /* Race breaker in case memory is freed before above code is called */
        sk->sk_write_space(sk);
        return ret;
}

/*
 * Construct a stream transport record marker in @buf.
 */
static inline void xs_encode_stream_record_marker(struct xdr_buf *buf)
{
        u32 reclen = buf->len - sizeof(rpc_fraghdr);
        rpc_fraghdr *base = buf->head[0].iov_base;
        *base = cpu_to_be32(RPC_LAST_STREAM_FRAGMENT | reclen);
}

/**
 * xs_local_send_request - write an RPC request to an AF_LOCAL socket
 * @task: RPC task that manages the state of an RPC request
 *
 * Return values:
 *        0:    The request has been sent
 *   EAGAIN:    The socket was blocked, please call again later to
 *              complete the request
 * ENOTCONN:    Caller needs to invoke connect logic then call again
 *    other:    Some other error occured, the request was not sent
 */
static int xs_local_send_request(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;
        struct sock_xprt *transport =
                                container_of(xprt, struct sock_xprt, xprt);
        struct xdr_buf *xdr = &req->rq_snd_buf;
        int status;
        int sent = 0;

        xs_encode_stream_record_marker(&req->rq_snd_buf);

        xs_pktdump("packet data:",
                        req->rq_svec->iov_base, req->rq_svec->iov_len);

        status = xs_sendpages(transport->sock, NULL, 0, xdr, req->rq_bytes_sent,
                              true, &sent);
        dprintk("RPC:       %s(%u) = %d\n",
                        __func__, xdr->len - req->rq_bytes_sent, status);

        if (status == -EAGAIN && sock_writeable(transport->inet))
                status = -ENOBUFS;

        if (likely(sent > 0) || status == 0) {
                req->rq_bytes_sent += sent;
                req->rq_xmit_bytes_sent += sent;
                if (likely(req->rq_bytes_sent >= req->rq_slen)) {
                        req->rq_bytes_sent = 0;
                        return 0;
                }
                status = -EAGAIN;
        }

        switch (status) {
        case -ENOBUFS:
                break;
        case -EAGAIN:
                status = xs_nospace(task);
                break;
        default:
                dprintk("RPC:       sendmsg returned unrecognized error %d\n",
                        -status);
        case -EPIPE:
                xs_close(xprt);
                status = -ENOTCONN;
        }

        return status;
}

/**
 * xs_udp_send_request - write an RPC request to a UDP socket
 * @task: address of RPC task that manages the state of an RPC request
 *
 * Return values:
 *        0:    The request has been sent
 *   EAGAIN:    The socket was blocked, please call again later to
 *              complete the request
 * ENOTCONN:    Caller needs to invoke connect logic then call again
 *    other:    Some other error occurred, the request was not sent
 */
static int xs_udp_send_request(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        struct xdr_buf *xdr = &req->rq_snd_buf;
        int sent = 0;
        int status;

        xs_pktdump("packet data:",
                                req->rq_svec->iov_base,
                                req->rq_svec->iov_len);

        if (!xprt_bound(xprt))
                return -ENOTCONN;
        status = xs_sendpages(transport->sock, xs_addr(xprt), xprt->addrlen,
                              xdr, req->rq_bytes_sent, true, &sent);

        dprintk("RPC:       xs_udp_send_request(%u) = %d\n",
                        xdr->len - req->rq_bytes_sent, status);

        /* firewall is blocking us, don't return -EAGAIN or we end up looping */
        if (status == -EPERM)
                goto process_status;

        if (status == -EAGAIN && sock_writeable(transport->inet))
                status = -ENOBUFS;

        if (sent > 0 || status == 0) {
                req->rq_xmit_bytes_sent += sent;
                if (sent >= req->rq_slen)
                        return 0;
                /* Still some bytes left; set up for a retry later. */
                status = -EAGAIN;
        }

process_status:
        switch (status) {
        case -ENOTSOCK:
                status = -ENOTCONN;
                /* Should we call xs_close() here? */
                break;
        case -EAGAIN:
                status = xs_nospace(task);
                break;
        default:
                dprintk("RPC:       sendmsg returned unrecognized error %d\n",
                        -status);
        case -ENETUNREACH:
        case -ENOBUFS:
        case -EPIPE:
        case -ECONNREFUSED:
        case -EPERM:
                /* When the server has died, an ICMP port unreachable message
                 * prompts ECONNREFUSED. */
                clear_bit(SOCK_ASYNC_NOSPACE, &transport->sock->flags);
        }

        return status;
}

/**
 * xs_tcp_send_request - write an RPC request to a TCP socket
 * @task: address of RPC task that manages the state of an RPC request
 *
 * Return values:
 *        0:    The request has been sent
 *   EAGAIN:    The socket was blocked, please call again later to
 *              complete the request
 * ENOTCONN:    Caller needs to invoke connect logic then call again
 *    other:    Some other error occurred, the request was not sent
 *
 * XXX: In the case of soft timeouts, should we eventually give up
 *      if sendmsg is not able to make progress?
 */
static int xs_tcp_send_request(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        struct xdr_buf *xdr = &req->rq_snd_buf;
        bool zerocopy = true;
        int status;
        int sent;

        xs_encode_stream_record_marker(&req->rq_snd_buf);

        xs_pktdump("packet data:",
                                req->rq_svec->iov_base,
                                req->rq_svec->iov_len);
        /* Don't use zero copy if this is a resend. If the RPC call
         * completes while the socket holds a reference to the pages,
         * then we may end up resending corrupted data.
         */
        if (task->tk_flags & RPC_TASK_SENT)
                zerocopy = false;

        /* Continue transmitting the packet/record. We must be careful
         * to cope with writespace callbacks arriving _after_ we have
         * called sendmsg(). */
        while (1) {
                sent = 0;
                status = xs_sendpages(transport->sock, NULL, 0, xdr,
                                      req->rq_bytes_sent, zerocopy, &sent);

                dprintk("RPC:       xs_tcp_send_request(%u) = %d\n",
                                xdr->len - req->rq_bytes_sent, status);

                /* If we've sent the entire packet, immediately
                 * reset the count of bytes sent. */
                req->rq_bytes_sent += sent;
                req->rq_xmit_bytes_sent += sent;
                if (likely(req->rq_bytes_sent >= req->rq_slen)) {
                        req->rq_bytes_sent = 0;
                        return 0;
                }

                if (status < 0)
                        break;
                if (sent == 0) {
                        status = -EAGAIN;
                        break;
                }
        }
        if (status == -EAGAIN && sk_stream_is_writeable(transport->inet))
                status = -ENOBUFS;

        switch (status) {
        case -ENOTSOCK:
                status = -ENOTCONN;
                /* Should we call xs_close() here? */
                break;
        case -EAGAIN:
                status = xs_nospace(task);
                break;
        default:
                dprintk("RPC:       sendmsg returned unrecognized error %d\n",
                        -status);
        case -ECONNRESET:
        case -ECONNREFUSED:
        case -ENOTCONN:
        case -EADDRINUSE:
        case -ENOBUFS:
        case -EPIPE:
                clear_bit(SOCK_ASYNC_NOSPACE, &transport->sock->flags);
        }

        return status;
}

/**
 * xs_tcp_release_xprt - clean up after a tcp transmission
 * @xprt: transport
 * @task: rpc task
 *
 * This cleans up if an error causes us to abort the transmission of a request.
 * In this case, the socket may need to be reset in order to avoid confusing
 * the server.
 */
static void xs_tcp_release_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
{
        struct rpc_rqst *req;

        if (task != xprt->snd_task)
                return;
        if (task == NULL)
                goto out_release;
        req = task->tk_rqstp;
        if (req == NULL)
                goto out_release;
        if (req->rq_bytes_sent == 0)
                goto out_release;
        if (req->rq_bytes_sent == req->rq_snd_buf.len)
                goto out_release;
        set_bit(XPRT_CLOSE_WAIT, &xprt->state);
out_release:
        xprt_release_xprt(xprt, task);
}

static void xs_save_old_callbacks(struct sock_xprt *transport, struct sock *sk)
{
        transport->old_data_ready = sk->sk_data_ready;
        transport->old_state_change = sk->sk_state_change;
        transport->old_write_space = sk->sk_write_space;
        transport->old_error_report = sk->sk_error_report;
}

static void xs_restore_old_callbacks(struct sock_xprt *transport, struct sock *sk)
{
        sk->sk_data_ready = transport->old_data_ready;
        sk->sk_state_change = transport->old_state_change;
        sk->sk_write_space = transport->old_write_space;
        sk->sk_error_report = transport->old_error_report;
}

static void xs_sock_reset_connection_flags(struct rpc_xprt *xprt)
{
        smp_mb__before_atomic();
        clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
        clear_bit(XPRT_CLOSING, &xprt->state);
        smp_mb__after_atomic();
}

static void xs_sock_mark_closed(struct rpc_xprt *xprt)
{
        xs_sock_reset_connection_flags(xprt);
        /* Mark transport as closed and wake up all pending tasks */
        xprt_disconnect_done(xprt);
}

/**
 * xs_error_report - callback to handle TCP socket state errors
 * @sk: socket
 *
 * Note: we don't call sock_error() since there may be a rpc_task
 * using the socket, and so we don't want to clear sk->sk_err.
 */
static void xs_error_report(struct sock *sk)
{
        struct rpc_xprt *xprt;
        int err;

        read_lock_bh(&sk->sk_callback_lock);
        if (!(xprt = xprt_from_sock(sk)))
                goto out;

        err = -sk->sk_err;
        if (err == 0)
                goto out;
        /* Is this a reset event? */
        if (sk->sk_state == TCP_CLOSE)
                xs_sock_mark_closed(xprt);
        dprintk("RPC:       xs_error_report client %p, error=%d...\n",
                        xprt, -err);
        trace_rpc_socket_error(xprt, sk->sk_socket, err);
        xprt_wake_pending_tasks(xprt, err);
 out:
        read_unlock_bh(&sk->sk_callback_lock);
}

static void xs_reset_transport(struct sock_xprt *transport)
{
        struct socket *sock = transport->sock;
        struct sock *sk = transport->inet;
        struct rpc_xprt *xprt = &transport->xprt;

        if (sk == NULL)
                return;

        if (atomic_read(&transport->xprt.swapper))
                sk_clear_memalloc(sk);

        kernel_sock_shutdown(sock, SHUT_RDWR);

        write_lock_bh(&sk->sk_callback_lock);
        transport->inet = NULL;
        transport->sock = NULL;

        sk->sk_user_data = NULL;

        xs_restore_old_callbacks(transport, sk);
        xprt_clear_connected(xprt);
        write_unlock_bh(&sk->sk_callback_lock);
        xs_sock_reset_connection_flags(xprt);

        trace_rpc_socket_close(xprt, sock);
        sock_release(sock);
}

/**
 * xs_close - close a socket
 * @xprt: transport
 *
 * This is used when all requests are complete; ie, no DRC state remains
 * on the server we want to save.
 *
 * The caller _must_ be holding XPRT_LOCKED in order to avoid issues with
 * xs_reset_transport() zeroing the socket from underneath a writer.
 */
static void xs_close(struct rpc_xprt *xprt)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);

        dprintk("RPC:       xs_close xprt %p\n", xprt);

        xs_reset_transport(transport);
        xprt->reestablish_timeout = 0;

        xprt_disconnect_done(xprt);
}

static void xs_inject_disconnect(struct rpc_xprt *xprt)
{
        dprintk("RPC:       injecting transport disconnect on xprt=%p\n",
                xprt);
        xprt_disconnect_done(xprt);
}

static void xs_xprt_free(struct rpc_xprt *xprt)
{
        xs_free_peer_addresses(xprt);
        xprt_free(xprt);
}

/**
 * xs_destroy - prepare to shutdown a transport
 * @xprt: doomed transport
 *
 */
static void xs_destroy(struct rpc_xprt *xprt)
{
        struct sock_xprt *transport = container_of(xprt,
                        struct sock_xprt, xprt);
        dprintk("RPC:       xs_destroy xprt %p\n", xprt);

        cancel_delayed_work_sync(&transport->connect_worker);
        xs_close(xprt);
        xs_xprt_free(xprt);
        module_put(THIS_MODULE);
}

static int xs_local_copy_to_xdr(struct xdr_buf *xdr, struct sk_buff *skb)
{
        struct xdr_skb_reader desc = {
                .skb            = skb,
                .offset         = sizeof(rpc_fraghdr),
                .count          = skb->len - sizeof(rpc_fraghdr),
        };

        if (xdr_partial_copy_from_skb(xdr, 0, &desc, xdr_skb_read_bits) < 0)
                return -1;
        if (desc.count)
                return -1;
        return 0;
}

/**
 * xs_local_data_ready - "data ready" callback for AF_LOCAL sockets
 * @sk: socket with data to read
 *
 * Currently this assumes we can read the whole reply in a single gulp.
 */
static void xs_local_data_ready(struct sock *sk)
{
        struct rpc_task *task;
        struct rpc_xprt *xprt;
        struct rpc_rqst *rovr;
        struct sk_buff *skb;
        int err, repsize, copied;
        u32 _xid;
        __be32 *xp;

        read_lock_bh(&sk->sk_callback_lock);
        dprintk("RPC:       %s...\n", __func__);
        xprt = xprt_from_sock(sk);
        if (xprt == NULL)
                goto out;

        skb = skb_recv_datagram(sk, 0, 1, &err);
        if (skb == NULL)
                goto out;

        repsize = skb->len - sizeof(rpc_fraghdr);
        if (repsize < 4) {
                dprintk("RPC:       impossible RPC reply size %d\n", repsize);
                goto dropit;
        }

        /* Copy the XID from the skb... */
        xp = skb_header_pointer(skb, sizeof(rpc_fraghdr), sizeof(_xid), &_xid);
        if (xp == NULL)
                goto dropit;

        /* Look up and lock the request corresponding to the given XID */
        spin_lock(&xprt->transport_lock);
        rovr = xprt_lookup_rqst(xprt, *xp);
        if (!rovr)
                goto out_unlock;
        task = rovr->rq_task;

        copied = rovr->rq_private_buf.buflen;
        if (copied > repsize)
                copied = repsize;

        if (xs_local_copy_to_xdr(&rovr->rq_private_buf, skb)) {
                dprintk("RPC:       sk_buff copy failed\n");
                goto out_unlock;
        }

        xprt_complete_rqst(task, copied);

 out_unlock:
        spin_unlock(&xprt->transport_lock);
 dropit:
        skb_free_datagram(sk, skb);
 out:
        read_unlock_bh(&sk->sk_callback_lock);
}

/**
 * xs_udp_data_ready - "data ready" callback for UDP sockets
 * @sk: socket with data to read
 *
 */
static void xs_udp_data_ready(struct sock *sk)
{
        struct rpc_task *task;
        struct rpc_xprt *xprt;
        struct rpc_rqst *rovr;
        struct sk_buff *skb;
        int err, repsize, copied;
        u32 _xid;
        __be32 *xp;

        read_lock_bh(&sk->sk_callback_lock);
        dprintk("RPC:       xs_udp_data_ready...\n");
        if (!(xprt = xprt_from_sock(sk)))
                goto out;

        if ((skb = skb_recv_datagram(sk, 0, 1, &err)) == NULL)
                goto out;

        repsize = skb->len - sizeof(struct udphdr);
        if (repsize < 4) {
                dprintk("RPC:       impossible RPC reply size %d!\n", repsize);
                goto dropit;
        }

        /* Copy the XID from the skb... */
        xp = skb_header_pointer(skb, sizeof(struct udphdr),
                                sizeof(_xid), &_xid);
        if (xp == NULL)
                goto dropit;

        /* Look up and lock the request corresponding to the given XID */
        spin_lock(&xprt->transport_lock);
        rovr = xprt_lookup_rqst(xprt, *xp);
        if (!rovr)
                goto out_unlock;
        task = rovr->rq_task;

        if ((copied = rovr->rq_private_buf.buflen) > repsize)
                copied = repsize;

        /* Suck it into the iovec, verify checksum if not done by hw. */
        if (csum_partial_copy_to_xdr(&rovr->rq_private_buf, skb)) {
                UDPX_INC_STATS_BH(sk, UDP_MIB_INERRORS);
                goto out_unlock;
        }

        UDPX_INC_STATS_BH(sk, UDP_MIB_INDATAGRAMS);

        xprt_adjust_cwnd(xprt, task, copied);
        xprt_complete_rqst(task, copied);

 out_unlock:
        spin_unlock(&xprt->transport_lock);
 dropit:
        skb_free_datagram(sk, skb);
 out:
        read_unlock_bh(&sk->sk_callback_lock);
}

/*
 * Helper function to force a TCP close if the server is sending
 * junk and/or it has put us in CLOSE_WAIT
 */
static void xs_tcp_force_close(struct rpc_xprt *xprt)
{
        xprt_force_disconnect(xprt);
}

static inline void xs_tcp_read_fraghdr(struct rpc_xprt *xprt, struct xdr_skb_reader *desc)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        size_t len, used;
        char *p;

        p = ((char *) &transport->tcp_fraghdr) + transport->tcp_offset;
        len = sizeof(transport->tcp_fraghdr) - transport->tcp_offset;
        used = xdr_skb_read_bits(desc, p, len);
        transport->tcp_offset += used;
        if (used != len)
                return;

        transport->tcp_reclen = ntohl(transport->tcp_fraghdr);
        if (transport->tcp_reclen & RPC_LAST_STREAM_FRAGMENT)
                transport->tcp_flags |= TCP_RCV_LAST_FRAG;
        else
                transport->tcp_flags &= ~TCP_RCV_LAST_FRAG;
        transport->tcp_reclen &= RPC_FRAGMENT_SIZE_MASK;

        transport->tcp_flags &= ~TCP_RCV_COPY_FRAGHDR;
        transport->tcp_offset = 0;

        /* Sanity check of the record length */
        if (unlikely(transport->tcp_reclen < 8)) {
                dprintk("RPC:       invalid TCP record fragment length\n");
                xs_tcp_force_close(xprt);
                return;
        }
        dprintk("RPC:       reading TCP record fragment of length %d\n",
                        transport->tcp_reclen);
}

static void xs_tcp_check_fraghdr(struct sock_xprt *transport)
{
        if (transport->tcp_offset == transport->tcp_reclen) {
                transport->tcp_flags |= TCP_RCV_COPY_FRAGHDR;
                transport->tcp_offset = 0;
                if (transport->tcp_flags & TCP_RCV_LAST_FRAG) {
                        transport->tcp_flags &= ~TCP_RCV_COPY_DATA;
                        transport->tcp_flags |= TCP_RCV_COPY_XID;
                        transport->tcp_copied = 0;
                }
        }
}

static inline void xs_tcp_read_xid(struct sock_xprt *transport, struct xdr_skb_reader *desc)
{
        size_t len, used;
        char *p;

        len = sizeof(transport->tcp_xid) - transport->tcp_offset;
        dprintk("RPC:       reading XID (%Zu bytes)\n", len);
        p = ((char *) &transport->tcp_xid) + transport->tcp_offset;
        used = xdr_skb_read_bits(desc, p, len);
        transport->tcp_offset += used;
        if (used != len)
                return;
        transport->tcp_flags &= ~TCP_RCV_COPY_XID;
        transport->tcp_flags |= TCP_RCV_READ_CALLDIR;
        transport->tcp_copied = 4;
        dprintk("RPC:       reading %s XID %08x\n",
                        (transport->tcp_flags & TCP_RPC_REPLY) ? "reply for"
                                                              : "request with",
                        ntohl(transport->tcp_xid));
        xs_tcp_check_fraghdr(transport);
}

static inline void xs_tcp_read_calldir(struct sock_xprt *transport,
                                       struct xdr_skb_reader *desc)
{
        size_t len, used;
        u32 offset;
        char *p;

        /*
         * We want transport->tcp_offset to be 8 at the end of this routine
         * (4 bytes for the xid and 4 bytes for the call/reply flag).
         * When this function is called for the first time,
         * transport->tcp_offset is 4 (after having already read the xid).
         */
        offset = transport->tcp_offset - sizeof(transport->tcp_xid);
        len = sizeof(transport->tcp_calldir) - offset;
        dprintk("RPC:       reading CALL/REPLY flag (%Zu bytes)\n", len);
        p = ((char *) &transport->tcp_calldir) + offset;
        used = xdr_skb_read_bits(desc, p, len);
        transport->tcp_offset += used;
        if (used != len)
                return;
        transport->tcp_flags &= ~TCP_RCV_READ_CALLDIR;
        /*
         * We don't yet have the XDR buffer, so we will write the calldir
         * out after we get the buffer from the 'struct rpc_rqst'
         */
        switch (ntohl(transport->tcp_calldir)) {
        case RPC_REPLY:
                transport->tcp_flags |= TCP_RCV_COPY_CALLDIR;
                transport->tcp_flags |= TCP_RCV_COPY_DATA;
                transport->tcp_flags |= TCP_RPC_REPLY;
                break;
        case RPC_CALL:
                transport->tcp_flags |= TCP_RCV_COPY_CALLDIR;
                transport->tcp_flags |= TCP_RCV_COPY_DATA;
                transport->tcp_flags &= ~TCP_RPC_REPLY;
                break;
        default:
                dprintk("RPC:       invalid request message type\n");
                xs_tcp_force_close(&transport->xprt);
        }
        xs_tcp_check_fraghdr(transport);
}

static inline void xs_tcp_read_common(struct rpc_xprt *xprt,
                                     struct xdr_skb_reader *desc,
                                     struct rpc_rqst *req)
{
        struct sock_xprt *transport =
                                container_of(xprt, struct sock_xprt, xprt);
        struct xdr_buf *rcvbuf;
        size_t len;
        ssize_t r;

        rcvbuf = &req->rq_private_buf;

        if (transport->tcp_flags & TCP_RCV_COPY_CALLDIR) {
                /*
                 * Save the RPC direction in the XDR buffer
                 */
                memcpy(rcvbuf->head[0].iov_base + transport->tcp_copied,
                        &transport->tcp_calldir,
                        sizeof(transport->tcp_calldir));
                transport->tcp_copied += sizeof(transport->tcp_calldir);
                transport->tcp_flags &= ~TCP_RCV_COPY_CALLDIR;
        }

        len = desc->count;
        if (len > transport->tcp_reclen - transport->tcp_offset) {
                struct xdr_skb_reader my_desc;

                len = transport->tcp_reclen - transport->tcp_offset;
                memcpy(&my_desc, desc, sizeof(my_desc));
                my_desc.count = len;
                r = xdr_partial_copy_from_skb(rcvbuf, transport->tcp_copied,
                                          &my_desc, xdr_skb_read_bits);
                desc->count -= r;
                desc->offset += r;
        } else
                r = xdr_partial_copy_from_skb(rcvbuf, transport->tcp_copied,
                                          desc, xdr_skb_read_bits);

        if (r > 0) {
                transport->tcp_copied += r;
                transport->tcp_offset += r;
        }
        if (r != len) {
                /* Error when copying to the receive buffer,
                 * usually because we weren't able to allocate
                 * additional buffer pages. All we can do now
                 * is turn off TCP_RCV_COPY_DATA, so the request
                 * will not receive any additional updates,
                 * and time out.
                 * Any remaining data from this record will
                 * be discarded.
                 */
                transport->tcp_flags &= ~TCP_RCV_COPY_DATA;
                dprintk("RPC:       XID %08x truncated request\n",
                                ntohl(transport->tcp_xid));
                dprintk("RPC:       xprt = %p, tcp_copied = %lu, "
                                "tcp_offset = %u, tcp_reclen = %u\n",
                                xprt, transport->tcp_copied,
                                transport->tcp_offset, transport->tcp_reclen);
                return;
        }

        dprintk("RPC:       XID %08x read %Zd bytes\n",
                        ntohl(transport->tcp_xid), r);
        dprintk("RPC:       xprt = %p, tcp_copied = %lu, tcp_offset = %u, "
                        "tcp_reclen = %u\n", xprt, transport->tcp_copied,
                        transport->tcp_offset, transport->tcp_reclen);

        if (transport->tcp_copied == req->rq_private_buf.buflen)
                transport->tcp_flags &= ~TCP_RCV_COPY_DATA;
        else if (transport->tcp_offset == transport->tcp_reclen) {
                if (transport->tcp_flags & TCP_RCV_LAST_FRAG)
                        transport->tcp_flags &= ~TCP_RCV_COPY_DATA;
        }
}

/*
 * Finds the request corresponding to the RPC xid and invokes the common
 * tcp read code to read the data.
 */
static inline int xs_tcp_read_reply(struct rpc_xprt *xprt,
                                    struct xdr_skb_reader *desc)
{
        struct sock_xprt *transport =
                                container_of(xprt, struct sock_xprt, xprt);
        struct rpc_rqst *req;

        dprintk("RPC:       read reply XID %08x\n", ntohl(transport->tcp_xid));

        /* Find and lock the request corresponding to this xid */
        spin_lock(&xprt->transport_lock);
        req = xprt_lookup_rqst(xprt, transport->tcp_xid);
        if (!req) {
                dprintk("RPC:       XID %08x request not found!\n",
                                ntohl(transport->tcp_xid));
                spin_unlock(&xprt->transport_lock);
                return -1;
        }

        xs_tcp_read_common(xprt, desc, req);

        if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))
                xprt_complete_rqst(req->rq_task, transport->tcp_copied);

        spin_unlock(&xprt->transport_lock);
        return 0;
}

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
/*
 * Obtains an rpc_rqst previously allocated and invokes the common
 * tcp read code to read the data.  The result is placed in the callback
 * queue.
 * If we're unable to obtain the rpc_rqst we schedule the closing of the
 * connection and return -1.
 */
static int xs_tcp_read_callback(struct rpc_xprt *xprt,
                                       struct xdr_skb_reader *desc)
{
        struct sock_xprt *transport =
                                container_of(xprt, struct sock_xprt, xprt);
        struct rpc_rqst *req;

        /* Look up and lock the request corresponding to the given XID */
        spin_lock(&xprt->transport_lock);
        req = xprt_lookup_bc_request(xprt, transport->tcp_xid);
        if (req == NULL) {
                spin_unlock(&xprt->transport_lock);
                printk(KERN_WARNING "Callback slot table overflowed\n");
                xprt_force_disconnect(xprt);
                return -1;
        }

        dprintk("RPC:       read callback  XID %08x\n", ntohl(req->rq_xid));
        xs_tcp_read_common(xprt, desc, req);

        if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))
                xprt_complete_bc_request(req, transport->tcp_copied);
        spin_unlock(&xprt->transport_lock);

        return 0;
}

static inline int _xs_tcp_read_data(struct rpc_xprt *xprt,
                                        struct xdr_skb_reader *desc)
{
        struct sock_xprt *transport =
                                container_of(xprt, struct sock_xprt, xprt);

        return (transport->tcp_flags & TCP_RPC_REPLY) ?
                xs_tcp_read_reply(xprt, desc) :
                xs_tcp_read_callback(xprt, desc);
}
#else
static inline int _xs_tcp_read_data(struct rpc_xprt *xprt,
                                        struct xdr_skb_reader *desc)
{
        return xs_tcp_read_reply(xprt, desc);
}
#endif /* CONFIG_SUNRPC_BACKCHANNEL */

/*
 * Read data off the transport.  This can be either an RPC_CALL or an
 * RPC_REPLY.  Relay the processing to helper functions.
 */
static void xs_tcp_read_data(struct rpc_xprt *xprt,
                                    struct xdr_skb_reader *desc)
{
        struct sock_xprt *transport =
                                container_of(xprt, struct sock_xprt, xprt);

        if (_xs_tcp_read_data(xprt, desc) == 0)
                xs_tcp_check_fraghdr(transport);
        else {
                /*
                 * The transport_lock protects the request handling.
                 * There's no need to hold it to update the tcp_flags.
                 */
                transport->tcp_flags &= ~TCP_RCV_COPY_DATA;
        }
}

static inline void xs_tcp_read_discard(struct sock_xprt *transport, struct xdr_skb_reader *desc)
{
        size_t len;

        len = transport->tcp_reclen - transport->tcp_offset;
        if (len > desc->count)
                len = desc->count;
        desc->count -= len;
        desc->offset += len;
        transport->tcp_offset += len;
        dprintk("RPC:       discarded %Zu bytes\n", len);
        xs_tcp_check_fraghdr(transport);
}

static int xs_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb, unsigned int offset, size_t len)
{
        struct rpc_xprt *xprt = rd_desc->arg.data;
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        struct xdr_skb_reader desc = {
                .skb    = skb,
                .offset = offset,
                .count  = len,
        };

        dprintk("RPC:       xs_tcp_data_recv started\n");
        do {
                trace_xs_tcp_data_recv(transport);
                /* Read in a new fragment marker if necessary */
                /* Can we ever really expect to get completely empty fragments? */
                if (transport->tcp_flags & TCP_RCV_COPY_FRAGHDR) {
                        xs_tcp_read_fraghdr(xprt, &desc);
                        continue;
                }
                /* Read in the xid if necessary */
                if (transport->tcp_flags & TCP_RCV_COPY_XID) {
                        xs_tcp_read_xid(transport, &desc);
                        continue;
                }
                /* Read in the call/reply flag */
                if (transport->tcp_flags & TCP_RCV_READ_CALLDIR) {
                        xs_tcp_read_calldir(transport, &desc);
                        continue;
                }
                /* Read in the request data */
                if (transport->tcp_flags & TCP_RCV_COPY_DATA) {
                        xs_tcp_read_data(xprt, &desc);
                        continue;
                }
                /* Skip over any trailing bytes on short reads */
                xs_tcp_read_discard(transport, &desc);
        } while (desc.count);
        trace_xs_tcp_data_recv(transport);
        dprintk("RPC:       xs_tcp_data_recv done\n");
        return len - desc.count;
}

static void xs_tcp_data_receive(struct sock_xprt *transport)
{
        struct rpc_xprt *xprt = &transport->xprt;
        struct sock *sk;
        read_descriptor_t rd_desc = {
                .count = 2*1024*1024,
                .arg.data = xprt,
        };
        unsigned long total = 0;
        int read = 0;

        sk = transport->inet;

        /* We use rd_desc to pass struct xprt to xs_tcp_data_recv */
        for (;;) {
                read = tcp_read_sock(sk, &rd_desc, xs_tcp_data_recv);
                if (read <= 0)
                        break;
                total += read;
                rd_desc.count = 65536;
        }
        trace_xs_tcp_data_ready(xprt, read, total);
}

/**
 * xs_tcp_data_ready - "data ready" callback for TCP sockets
 * @sk: socket with data to read
 *
 */
static void xs_tcp_data_ready(struct sock *sk)
{
        struct sock_xprt *transport;
        struct rpc_xprt *xprt;

        dprintk("RPC:       xs_tcp_data_ready...\n");

        read_lock_bh(&sk->sk_callback_lock);
        if (!(xprt = xprt_from_sock(sk)))
                goto out;
        transport = container_of(xprt, struct sock_xprt, xprt);

        /* Any data means we had a useful conversation, so
         * the we don't need to delay the next reconnect
         */
        if (xprt->reestablish_timeout)
                xprt->reestablish_timeout = 0;

        xs_tcp_data_receive(transport);
out:
        read_unlock_bh(&sk->sk_callback_lock);
}

/**
 * xs_tcp_state_change - callback to handle TCP socket state changes
 * @sk: socket whose state has changed
 *
 */
static void xs_tcp_state_change(struct sock *sk)
{
        struct rpc_xprt *xprt;
        struct sock_xprt *transport;

        read_lock_bh(&sk->sk_callback_lock);
        if (!(xprt = xprt_from_sock(sk)))
                goto out;
        dprintk("RPC:       xs_tcp_state_change client %p...\n", xprt);
        dprintk("RPC:       state %x conn %d dead %d zapped %d sk_shutdown %d\n",
                        sk->sk_state, xprt_connected(xprt),
                        sock_flag(sk, SOCK_DEAD),
                        sock_flag(sk, SOCK_ZAPPED),
                        sk->sk_shutdown);

        transport = container_of(xprt, struct sock_xprt, xprt);
        trace_rpc_socket_state_change(xprt, sk->sk_socket);
        switch (sk->sk_state) {
        case TCP_ESTABLISHED:
                spin_lock(&xprt->transport_lock);
                if (!xprt_test_and_set_connected(xprt)) {

                        /* Reset TCP record info */
                        transport->tcp_offset = 0;
                        transport->tcp_reclen = 0;
                        transport->tcp_copied = 0;
                        transport->tcp_flags =
                                TCP_RCV_COPY_FRAGHDR | TCP_RCV_COPY_XID;
                        xprt->connect_cookie++;
                        clear_bit(XPRT_SOCK_CONNECTING, &transport->sock_state);
                        xprt_clear_connecting(xprt);

                        xprt_wake_pending_tasks(xprt, -EAGAIN);
                }
                spin_unlock(&xprt->transport_lock);
                break;
        case TCP_FIN_WAIT1:
                /* The client initiated a shutdown of the socket */
                xprt->connect_cookie++;
                xprt->reestablish_timeout = 0;
                set_bit(XPRT_CLOSING, &xprt->state);
                smp_mb__before_atomic();
                clear_bit(XPRT_CONNECTED, &xprt->state);
                clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
                smp_mb__after_atomic();
                break;
        case TCP_CLOSE_WAIT:
                /* The server initiated a shutdown of the socket */
                xprt->connect_cookie++;
                clear_bit(XPRT_CONNECTED, &xprt->state);
                xs_tcp_force_close(xprt);
        case TCP_CLOSING:
                /*
                 * If the server closed down the connection, make sure that
                 * we back off before reconnecting
                 */
                if (xprt->reestablish_timeout < XS_TCP_INIT_REEST_TO)
                        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
                break;
        case TCP_LAST_ACK:
                set_bit(XPRT_CLOSING, &xprt->state);
                smp_mb__before_atomic();
                clear_bit(XPRT_CONNECTED, &xprt->state);
                smp_mb__after_atomic();
                break;
        case TCP_CLOSE:
                if (test_and_clear_bit(XPRT_SOCK_CONNECTING,
                                        &transport->sock_state))
                        xprt_clear_connecting(xprt);
                xs_sock_mark_closed(xprt);
        }
 out:
        read_unlock_bh(&sk->sk_callback_lock);
}

static void xs_write_space(struct sock *sk)
{
        struct socket *sock;
        struct rpc_xprt *xprt;

        if (unlikely(!(sock = sk->sk_socket)))
                return;
        clear_bit(SOCK_NOSPACE, &sock->flags);

        if (unlikely(!(xprt = xprt_from_sock(sk))))
                return;
        if (test_and_clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags) == 0)
                return;

        xprt_write_space(xprt);
}

/**
 * xs_udp_write_space - callback invoked when socket buffer space
 *                             becomes available
 * @sk: socket whose state has changed
 *
 * Called when more output buffer space is available for this socket.
 * We try not to wake our writers until they can make "significant"
 * progress, otherwise we'll waste resources thrashing kernel_sendmsg
 * with a bunch of small requests.
 */
static void xs_udp_write_space(struct sock *sk)
{
        read_lock_bh(&sk->sk_callback_lock);

        /* from net/core/sock.c:sock_def_write_space */
        if (sock_writeable(sk))
                xs_write_space(sk);

        read_unlock_bh(&sk->sk_callback_lock);
}

/**
 * xs_tcp_write_space - callback invoked when socket buffer space
 *                             becomes available
 * @sk: socket whose state has changed
 *
 * Called when more output buffer space is available for this socket.
 * We try not to wake our writers until they can make "significant"
 * progress, otherwise we'll waste resources thrashing kernel_sendmsg
 * with a bunch of small requests.
 */
static void xs_tcp_write_space(struct sock *sk)
{
        read_lock_bh(&sk->sk_callback_lock);

        /* from net/core/stream.c:sk_stream_write_space */
        if (sk_stream_is_writeable(sk))
                xs_write_space(sk);

        read_unlock_bh(&sk->sk_callback_lock);
}

static void xs_udp_do_set_buffer_size(struct rpc_xprt *xprt)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        struct sock *sk = transport->inet;

        if (transport->rcvsize) {
                sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
                sk->sk_rcvbuf = transport->rcvsize * xprt->max_reqs * 2;
        }
        if (transport->sndsize) {
                sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
                sk->sk_sndbuf = transport->sndsize * xprt->max_reqs * 2;
                sk->sk_write_space(sk);
        }
}

/**
 * xs_udp_set_buffer_size - set send and receive limits
 * @xprt: generic transport
 * @sndsize: requested size of send buffer, in bytes
 * @rcvsize: requested size of receive buffer, in bytes
 *
 * Set socket send and receive buffer size limits.
 */
static void xs_udp_set_buffer_size(struct rpc_xprt *xprt, size_t sndsize, size_t rcvsize)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);

        transport->sndsize = 0;
        if (sndsize)
                transport->sndsize = sndsize + 1024;
        transport->rcvsize = 0;
        if (rcvsize)
                transport->rcvsize = rcvsize + 1024;

        xs_udp_do_set_buffer_size(xprt);
}

/**
 * xs_udp_timer - called when a retransmit timeout occurs on a UDP transport
 * @task: task that timed out
 *
 * Adjust the congestion window after a retransmit timeout has occurred.
 */
static void xs_udp_timer(struct rpc_xprt *xprt, struct rpc_task *task)
{
        xprt_adjust_cwnd(xprt, task, -ETIMEDOUT);
}

static unsigned short xs_get_random_port(void)
{
        unsigned short range = xprt_max_resvport - xprt_min_resvport;
        unsigned short rand = (unsigned short) prandom_u32() % range;
        return rand + xprt_min_resvport;
}

/**
 * xs_set_reuseaddr_port - set the socket's port and address reuse options
 * @sock: socket
 *
 * Note that this function has to be called on all sockets that share the
 * same port, and it must be called before binding.
 */
static void xs_sock_set_reuseport(struct socket *sock)
{
        int opt = 1;

        kernel_setsockopt(sock, SOL_SOCKET, SO_REUSEPORT,
                        (char *)&opt, sizeof(opt));
}

static unsigned short xs_sock_getport(struct socket *sock)
{
        struct sockaddr_storage buf;
        int buflen;
        unsigned short port = 0;

        if (kernel_getsockname(sock, (struct sockaddr *)&buf, &buflen) < 0)
                goto out;
        switch (buf.ss_family) {
        case AF_INET6:
                port = ntohs(((struct sockaddr_in6 *)&buf)->sin6_port);
                break;
        case AF_INET:
                port = ntohs(((struct sockaddr_in *)&buf)->sin_port);
        }
out:
        return port;
}

/**
 * xs_set_port - reset the port number in the remote endpoint address
 * @xprt: generic transport
 * @port: new port number
 *
 */
static void xs_set_port(struct rpc_xprt *xprt, unsigned short port)
{
        dprintk("RPC:       setting port for xprt %p to %u\n", xprt, port);

        rpc_set_port(xs_addr(xprt), port);
        xs_update_peer_port(xprt);
}

static void xs_set_srcport(struct sock_xprt *transport, struct socket *sock)
{
        if (transport->srcport == 0)
                transport->srcport = xs_sock_getport(sock);
}

static unsigned short xs_get_srcport(struct sock_xprt *transport)
{
        unsigned short port = transport->srcport;

        if (port == 0 && transport->xprt.resvport)
                port = xs_get_random_port();
        return port;
}

static unsigned short xs_next_srcport(struct sock_xprt *transport, unsigned short port)
{
        if (transport->srcport != 0)
                transport->srcport = 0;
        if (!transport->xprt.resvport)
                return 0;
        if (port <= xprt_min_resvport || port > xprt_max_resvport)
                return xprt_max_resvport;
        return --port;
}
static int xs_bind(struct sock_xprt *transport, struct socket *sock)
{
        struct sockaddr_storage myaddr;
        int err, nloop = 0;
        unsigned short port = xs_get_srcport(transport);
        unsigned short last;

        /*
         * If we are asking for any ephemeral port (i.e. port == 0 &&
         * transport->xprt.resvport == 0), don't bind.  Let the local
         * port selection happen implicitly when the socket is used
         * (for example at connect time).
         *
         * This ensures that we can continue to establish TCP
         * connections even when all local ephemeral ports are already
         * a part of some TCP connection.  This makes no difference
         * for UDP sockets, but also doens't harm them.
         *
         * If we're asking for any reserved port (i.e. port == 0 &&
         * transport->xprt.resvport == 1) xs_get_srcport above will
         * ensure that port is non-zero and we will bind as needed.
         */
        if (port == 0)
                return 0;

        memcpy(&myaddr, &transport->srcaddr, transport->xprt.addrlen);
        do {
                rpc_set_port((struct sockaddr *)&myaddr, port);
                err = kernel_bind(sock, (struct sockaddr *)&myaddr,
                                transport->xprt.addrlen);
                if (err == 0) {
                        transport->srcport = port;
                        break;
                }
                last = port;
                port = xs_next_srcport(transport, port);
                if (port > last)
                        nloop++;
        } while (err == -EADDRINUSE && nloop != 2);

        if (myaddr.ss_family == AF_INET)
                dprintk("RPC:       %s %pI4:%u: %s (%d)\n", __func__,
                                &((struct sockaddr_in *)&myaddr)->sin_addr,
                                port, err ? "failed" : "ok", err);
        else
                dprintk("RPC:       %s %pI6:%u: %s (%d)\n", __func__,
                                &((struct sockaddr_in6 *)&myaddr)->sin6_addr,
                                port, err ? "failed" : "ok", err);
        return err;
}

/*
 * We don't support autobind on AF_LOCAL sockets
 */
static void xs_local_rpcbind(struct rpc_task *task)
{
        rcu_read_lock();
        xprt_set_bound(rcu_dereference(task->tk_client->cl_xprt));
        rcu_read_unlock();
}

static void xs_local_set_port(struct rpc_xprt *xprt, unsigned short port)
{
}

#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key xs_key[2];
static struct lock_class_key xs_slock_key[2];

static inline void xs_reclassify_socketu(struct socket *sock)
{
        struct sock *sk = sock->sk;

        sock_lock_init_class_and_name(sk, "slock-AF_LOCAL-RPC",
                &xs_slock_key[1], "sk_lock-AF_LOCAL-RPC", &xs_key[1]);
}

static inline void xs_reclassify_socket4(struct socket *sock)
{
        struct sock *sk = sock->sk;

        sock_lock_init_class_and_name(sk, "slock-AF_INET-RPC",
                &xs_slock_key[0], "sk_lock-AF_INET-RPC", &xs_key[0]);
}

static inline void xs_reclassify_socket6(struct socket *sock)
{
        struct sock *sk = sock->sk;

        sock_lock_init_class_and_name(sk, "slock-AF_INET6-RPC",
                &xs_slock_key[1], "sk_lock-AF_INET6-RPC", &xs_key[1]);
}

static inline void xs_reclassify_socket(int family, struct socket *sock)
{
        WARN_ON_ONCE(sock_owned_by_user(sock->sk));
        if (sock_owned_by_user(sock->sk))
                return;

        switch (family) {
        case AF_LOCAL:
                xs_reclassify_socketu(sock);
                break;
        case AF_INET:
                xs_reclassify_socket4(sock);
                break;
        case AF_INET6:
                xs_reclassify_socket6(sock);
                break;
        }
}
#else
static inline void xs_reclassify_socketu(struct socket *sock)
{
}

static inline void xs_reclassify_socket4(struct socket *sock)
{
}

static inline void xs_reclassify_socket6(struct socket *sock)
{
}

static inline void xs_reclassify_socket(int family, struct socket *sock)
{
}
#endif

static void xs_dummy_setup_socket(struct work_struct *work)
{
}

static struct socket *xs_create_sock(struct rpc_xprt *xprt,
                struct sock_xprt *transport, int family, int type,
                int protocol, bool reuseport)
{
        struct socket *sock;
        int err;

        err = __sock_create(xprt->xprt_net, family, type, protocol, &sock, 1);
        if (err < 0) {
                dprintk("RPC:       can't create %d transport socket (%d).\n",
                                protocol, -err);
                goto out;
        }
        xs_reclassify_socket(family, sock);

        if (reuseport)
                xs_sock_set_reuseport(sock);

        err = xs_bind(transport, sock);
        if (err) {
                sock_release(sock);
                goto out;
        }

        return sock;
out:
        return ERR_PTR(err);
}

static int xs_local_finish_connecting(struct rpc_xprt *xprt,
                                      struct socket *sock)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
                                                                        xprt);

        if (!transport->inet) {
                struct sock *sk = sock->sk;

                write_lock_bh(&sk->sk_callback_lock);

                xs_save_old_callbacks(transport, sk);

                sk->sk_user_data = xprt;
                sk->sk_data_ready = xs_local_data_ready;
                sk->sk_write_space = xs_udp_write_space;
                sk->sk_error_report = xs_error_report;
                sk->sk_allocation = GFP_NOIO;

                xprt_clear_connected(xprt);

                /* Reset to new socket */
                transport->sock = sock;
                transport->inet = sk;

                write_unlock_bh(&sk->sk_callback_lock);
        }

        /* Tell the socket layer to start connecting... */
        xprt->stat.connect_count++;
        xprt->stat.connect_start = jiffies;
        return kernel_connect(sock, xs_addr(xprt), xprt->addrlen, 0);
}

/**
 * xs_local_setup_socket - create AF_LOCAL socket, connect to a local endpoint
 * @transport: socket transport to connect
 */
static int xs_local_setup_socket(struct sock_xprt *transport)
{
        struct rpc_xprt *xprt = &transport->xprt;
        struct socket *sock;
        int status = -EIO;

        status = __sock_create(xprt->xprt_net, AF_LOCAL,
                                        SOCK_STREAM, 0, &sock, 1);
        if (status < 0) {
                dprintk("RPC:       can't create AF_LOCAL "
                        "transport socket (%d).\n", -status);
                goto out;
        }
        xs_reclassify_socketu(sock);

        dprintk("RPC:       worker connecting xprt %p via AF_LOCAL to %s\n",
                        xprt, xprt->address_strings[RPC_DISPLAY_ADDR]);

        status = xs_local_finish_connecting(xprt, sock);
        trace_rpc_socket_connect(xprt, sock, status);
        switch (status) {
        case 0:
                dprintk("RPC:       xprt %p connected to %s\n",
                                xprt, xprt->address_strings[RPC_DISPLAY_ADDR]);
                xprt_set_connected(xprt);
        case -ENOBUFS:
                break;
        case -ENOENT:
                dprintk("RPC:       xprt %p: socket %s does not exist\n",
                                xprt, xprt->address_strings[RPC_DISPLAY_ADDR]);
                break;
        case -ECONNREFUSED:
                dprintk("RPC:       xprt %p: connection refused for %s\n",
                                xprt, xprt->address_strings[RPC_DISPLAY_ADDR]);
                break;
        default:
                printk(KERN_ERR "%s: unhandled error (%d) connecting to %s\n",
                                __func__, -status,
                                xprt->address_strings[RPC_DISPLAY_ADDR]);
        }

out:
        xprt_clear_connecting(xprt);
        xprt_wake_pending_tasks(xprt, status);
        return status;
}

static void xs_local_connect(struct rpc_xprt *xprt, struct rpc_task *task)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        int ret;

         if (RPC_IS_ASYNC(task)) {
                /*
                 * We want the AF_LOCAL connect to be resolved in the
                 * filesystem namespace of the process making the rpc
                 * call.  Thus we connect synchronously.
                 *
                 * If we want to support asynchronous AF_LOCAL calls,
                 * we'll need to figure out how to pass a namespace to
                 * connect.
                 */
                rpc_exit(task, -ENOTCONN);
                return;
        }
        ret = xs_local_setup_socket(transport);
        if (ret && !RPC_IS_SOFTCONN(task))
                msleep_interruptible(15000);
}

#if IS_ENABLED(CONFIG_SUNRPC_SWAP)
/*
 * Note that this should be called with XPRT_LOCKED held (or when we otherwise
 * know that we have exclusive access to the socket), to guard against
 * races with xs_reset_transport.
 */
static void xs_set_memalloc(struct rpc_xprt *xprt)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
                        xprt);

        /*
         * If there's no sock, then we have nothing to set. The
         * reconnecting process will get it for us.
         */
        if (!transport->inet)
                return;
        if (atomic_read(&xprt->swapper))
                sk_set_memalloc(transport->inet);
}

/**
 * xs_enable_swap - Tag this transport as being used for swap.
 * @xprt: transport to tag
 *
 * Take a reference to this transport on behalf of the rpc_clnt, and
 * optionally mark it for swapping if it wasn't already.
 */
static int
xs_enable_swap(struct rpc_xprt *xprt)
{
        struct sock_xprt *xs = container_of(xprt, struct sock_xprt, xprt);

        if (atomic_inc_return(&xprt->swapper) != 1)
                return 0;
        if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE))
                return -ERESTARTSYS;
        if (xs->inet)
                sk_set_memalloc(xs->inet);
        xprt_release_xprt(xprt, NULL);
        return 0;
}

/**
 * xs_disable_swap - Untag this transport as being used for swap.
 * @xprt: transport to tag
 *
 * Drop a "swapper" reference to this xprt on behalf of the rpc_clnt. If the
 * swapper refcount goes to 0, untag the socket as a memalloc socket.
 */
static void
xs_disable_swap(struct rpc_xprt *xprt)
{
        struct sock_xprt *xs = container_of(xprt, struct sock_xprt, xprt);

        if (!atomic_dec_and_test(&xprt->swapper))
                return;
        if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE))
                return;
        if (xs->inet)
                sk_clear_memalloc(xs->inet);
        xprt_release_xprt(xprt, NULL);
}
#else
static void xs_set_memalloc(struct rpc_xprt *xprt)
{
}

static int
xs_enable_swap(struct rpc_xprt *xprt)
{
        return -EINVAL;
}

static void
xs_disable_swap(struct rpc_xprt *xprt)
{
}
#endif

static void xs_udp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);

        if (!transport->inet) {
                struct sock *sk = sock->sk;

                write_lock_bh(&sk->sk_callback_lock);

                xs_save_old_callbacks(transport, sk);

                sk->sk_user_data = xprt;
                sk->sk_data_ready = xs_udp_data_ready;
                sk->sk_write_space = xs_udp_write_space;
                sk->sk_allocation = GFP_NOIO;

                xprt_set_connected(xprt);

                /* Reset to new socket */
                transport->sock = sock;
                transport->inet = sk;

                xs_set_memalloc(xprt);

                write_unlock_bh(&sk->sk_callback_lock);
        }
        xs_udp_do_set_buffer_size(xprt);
}

static void xs_udp_setup_socket(struct work_struct *work)
{
        struct sock_xprt *transport =
                container_of(work, struct sock_xprt, connect_worker.work);
        struct rpc_xprt *xprt = &transport->xprt;
        struct socket *sock = transport->sock;
        int status = -EIO;

        sock = xs_create_sock(xprt, transport,
                        xs_addr(xprt)->sa_family, SOCK_DGRAM,
                        IPPROTO_UDP, false);
        if (IS_ERR(sock))
                goto out;

        dprintk("RPC:       worker connecting xprt %p via %s to "
                                "%s (port %s)\n", xprt,
                        xprt->address_strings[RPC_DISPLAY_PROTO],
                        xprt->address_strings[RPC_DISPLAY_ADDR],
                        xprt->address_strings[RPC_DISPLAY_PORT]);

        xs_udp_finish_connecting(xprt, sock);
        trace_rpc_socket_connect(xprt, sock, 0);
        status = 0;
out:
        xprt_unlock_connect(xprt, transport);
        xprt_clear_connecting(xprt);
        xprt_wake_pending_tasks(xprt, status);
}

/**
 * xs_tcp_shutdown - gracefully shut down a TCP socket
 * @xprt: transport
 *
 * Initiates a graceful shutdown of the TCP socket by calling the
 * equivalent of shutdown(SHUT_RDWR);
 */
static void xs_tcp_shutdown(struct rpc_xprt *xprt)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        struct socket *sock = transport->sock;

        if (sock == NULL)
                return;
        if (xprt_connected(xprt)) {
                kernel_sock_shutdown(sock, SHUT_RDWR);
                trace_rpc_socket_shutdown(xprt, sock);
        } else
                xs_reset_transport(transport);
}

static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        int ret = -ENOTCONN;

        if (!transport->inet) {
                struct sock *sk = sock->sk;
                unsigned int keepidle = xprt->timeout->to_initval / HZ;
                unsigned int keepcnt = xprt->timeout->to_retries + 1;
                unsigned int opt_on = 1;
                unsigned int timeo;

                /* TCP Keepalive options */
                kernel_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
                                (char *)&opt_on, sizeof(opt_on));
                kernel_setsockopt(sock, SOL_TCP, TCP_KEEPIDLE,
                                (char *)&keepidle, sizeof(keepidle));
                kernel_setsockopt(sock, SOL_TCP, TCP_KEEPINTVL,
                                (char *)&keepidle, sizeof(keepidle));
                kernel_setsockopt(sock, SOL_TCP, TCP_KEEPCNT,
                                (char *)&keepcnt, sizeof(keepcnt));

                /* TCP user timeout (see RFC5482) */
                timeo = jiffies_to_msecs(xprt->timeout->to_initval) *
                        (xprt->timeout->to_retries + 1);
                kernel_setsockopt(sock, SOL_TCP, TCP_USER_TIMEOUT,
                                (char *)&timeo, sizeof(timeo));

                write_lock_bh(&sk->sk_callback_lock);

                xs_save_old_callbacks(transport, sk);

                sk->sk_user_data = xprt;
                sk->sk_data_ready = xs_tcp_data_ready;
                sk->sk_state_change = xs_tcp_state_change;
                sk->sk_write_space = xs_tcp_write_space;
                sk->sk_error_report = xs_error_report;
                sk->sk_allocation = GFP_NOIO;

                /* socket options */
                sock_reset_flag(sk, SOCK_LINGER);
                tcp_sk(sk)->nonagle |= TCP_NAGLE_OFF;

                xprt_clear_connected(xprt);

                /* Reset to new socket */
                transport->sock = sock;
                transport->inet = sk;

                write_unlock_bh(&sk->sk_callback_lock);
        }

        if (!xprt_bound(xprt))
                goto out;

        xs_set_memalloc(xprt);

        /* Tell the socket layer to start connecting... */
        xprt->stat.connect_count++;
        xprt->stat.connect_start = jiffies;
        set_bit(XPRT_SOCK_CONNECTING, &transport->sock_state);
        ret = kernel_connect(sock, xs_addr(xprt), xprt->addrlen, O_NONBLOCK);
        switch (ret) {
        case 0:
                xs_set_srcport(transport, sock);
        case -EINPROGRESS:
                /* SYN_SENT! */
                if (xprt->reestablish_timeout < XS_TCP_INIT_REEST_TO)
                        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
        }
out:
        return ret;
}

/**
 * xs_tcp_setup_socket - create a TCP socket and connect to a remote endpoint
 *
 * Invoked by a work queue tasklet.
 */
static void xs_tcp_setup_socket(struct work_struct *work)
{
        struct sock_xprt *transport =
                container_of(work, struct sock_xprt, connect_worker.work);
        struct socket *sock = transport->sock;
        struct rpc_xprt *xprt = &transport->xprt;
        int status = -EIO;

        if (!sock) {
                sock = xs_create_sock(xprt, transport,
                                xs_addr(xprt)->sa_family, SOCK_STREAM,
                                IPPROTO_TCP, true);
                if (IS_ERR(sock)) {
                        status = PTR_ERR(sock);
                        goto out;
                }
        }

        dprintk("RPC:       worker connecting xprt %p via %s to "
                                "%s (port %s)\n", xprt,
                        xprt->address_strings[RPC_DISPLAY_PROTO],
                        xprt->address_strings[RPC_DISPLAY_ADDR],
                        xprt->address_strings[RPC_DISPLAY_PORT]);

        status = xs_tcp_finish_connecting(xprt, sock);
        trace_rpc_socket_connect(xprt, sock, status);
        dprintk("RPC:       %p connect status %d connected %d sock state %d\n",
                        xprt, -status, xprt_connected(xprt),
                        sock->sk->sk_state);
        switch (status) {
        default:
                printk("%s: connect returned unhandled error %d\n",
                        __func__, status);
        case -EADDRNOTAVAIL:
                /* We're probably in TIME_WAIT. Get rid of existing socket,
                 * and retry
                 */
                xs_tcp_force_close(xprt);
                break;
        case 0:
        case -EINPROGRESS:
        case -EALREADY:
                xprt_unlock_connect(xprt, transport);
                return;
        case -EINVAL:
                /* Happens, for instance, if the user specified a link
                 * local IPv6 address without a scope-id.
                 */
        case -ECONNREFUSED:
        case -ECONNRESET:
        case -ENETUNREACH:
        case -EADDRINUSE:
        case -ENOBUFS:
                /* retry with existing socket, after a delay */
                xs_tcp_force_close(xprt);
                goto out;
        }
        status = -EAGAIN;
out:
        xprt_unlock_connect(xprt, transport);
        xprt_clear_connecting(xprt);
        xprt_wake_pending_tasks(xprt, status);
}

/**
 * xs_connect - connect a socket to a remote endpoint
 * @xprt: pointer to transport structure
 * @task: address of RPC task that manages state of connect request
 *
 * TCP: If the remote end dropped the connection, delay reconnecting.
 *
 * UDP socket connects are synchronous, but we use a work queue anyway
 * to guarantee that even unprivileged user processes can set up a
 * socket on a privileged port.
 *
 * If a UDP socket connect fails, the delay behavior here prevents
 * retry floods (hard mounts).
 */
static void xs_connect(struct rpc_xprt *xprt, struct rpc_task *task)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);

        WARN_ON_ONCE(!xprt_lock_connect(xprt, task, transport));

        if (transport->sock != NULL) {
                dprintk("RPC:       xs_connect delayed xprt %p for %lu "
                                "seconds\n",
                                xprt, xprt->reestablish_timeout / HZ);

                /* Start by resetting any existing state */
                xs_reset_transport(transport);

                queue_delayed_work(rpciod_workqueue,
                                   &transport->connect_worker,
                                   xprt->reestablish_timeout);
                xprt->reestablish_timeout <<= 1;
                if (xprt->reestablish_timeout < XS_TCP_INIT_REEST_TO)
                        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
                if (xprt->reestablish_timeout > XS_TCP_MAX_REEST_TO)
                        xprt->reestablish_timeout = XS_TCP_MAX_REEST_TO;
        } else {
                dprintk("RPC:       xs_connect scheduled xprt %p\n", xprt);
                queue_delayed_work(rpciod_workqueue,
                                   &transport->connect_worker, 0);
        }
}

/**
 * xs_local_print_stats - display AF_LOCAL socket-specifc stats
 * @xprt: rpc_xprt struct containing statistics
 * @seq: output file
 *
 */
static void xs_local_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
{
        long idle_time = 0;

        if (xprt_connected(xprt))
                idle_time = (long)(jiffies - xprt->last_used) / HZ;

        seq_printf(seq, "\txprt:\tlocal %lu %lu %lu %ld %lu %lu %lu "
                        "%llu %llu %lu %llu %llu\n",
                        xprt->stat.bind_count,
                        xprt->stat.connect_count,
                        xprt->stat.connect_time,
                        idle_time,
                        xprt->stat.sends,
                        xprt->stat.recvs,
                        xprt->stat.bad_xids,
                        xprt->stat.req_u,
                        xprt->stat.bklog_u,
                        xprt->stat.max_slots,
                        xprt->stat.sending_u,
                        xprt->stat.pending_u);
}

/**
 * xs_udp_print_stats - display UDP socket-specifc stats
 * @xprt: rpc_xprt struct containing statistics
 * @seq: output file
 *
 */
static void xs_udp_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);

        seq_printf(seq, "\txprt:\tudp %u %lu %lu %lu %lu %llu %llu "
                        "%lu %llu %llu\n",
                        transport->srcport,
                        xprt->stat.bind_count,
                        xprt->stat.sends,
                        xprt->stat.recvs,
                        xprt->stat.bad_xids,
                        xprt->stat.req_u,
                        xprt->stat.bklog_u,
                        xprt->stat.max_slots,
                        xprt->stat.sending_u,
                        xprt->stat.pending_u);
}

/**
 * xs_tcp_print_stats - display TCP socket-specifc stats
 * @xprt: rpc_xprt struct containing statistics
 * @seq: output file
 *
 */
static void xs_tcp_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        long idle_time = 0;

        if (xprt_connected(xprt))
                idle_time = (long)(jiffies - xprt->last_used) / HZ;

        seq_printf(seq, "\txprt:\ttcp %u %lu %lu %lu %ld %lu %lu %lu "
                        "%llu %llu %lu %llu %llu\n",
                        transport->srcport,
                        xprt->stat.bind_count,
                        xprt->stat.connect_count,
                        xprt->stat.connect_time,
                        idle_time,
                        xprt->stat.sends,
                        xprt->stat.recvs,
                        xprt->stat.bad_xids,
                        xprt->stat.req_u,
                        xprt->stat.bklog_u,
                        xprt->stat.max_slots,
                        xprt->stat.sending_u,
                        xprt->stat.pending_u);
}

/*
 * Allocate a bunch of pages for a scratch buffer for the rpc code. The reason
 * we allocate pages instead doing a kmalloc like rpc_malloc is because we want
 * to use the server side send routines.
 */
static void *bc_malloc(struct rpc_task *task, size_t size)
{
        struct page *page;
        struct rpc_buffer *buf;

        WARN_ON_ONCE(size > PAGE_SIZE - sizeof(struct rpc_buffer));
        if (size > PAGE_SIZE - sizeof(struct rpc_buffer))
                return NULL;

        page = alloc_page(GFP_KERNEL);
        if (!page)
                return NULL;

        buf = page_address(page);
        buf->len = PAGE_SIZE;

        return buf->data;
}

/*
 * Free the space allocated in the bc_alloc routine
 */
static void bc_free(void *buffer)
{
        struct rpc_buffer *buf;

        if (!buffer)
                return;

        buf = container_of(buffer, struct rpc_buffer, data);
        free_page((unsigned long)buf);
}

/*
 * Use the svc_sock to send the callback. Must be called with svsk->sk_mutex
 * held. Borrows heavily from svc_tcp_sendto and xs_tcp_send_request.
 */
static int bc_sendto(struct rpc_rqst *req)
{
        int len;
        struct xdr_buf *xbufp = &req->rq_snd_buf;
        struct rpc_xprt *xprt = req->rq_xprt;
        struct sock_xprt *transport =
                                container_of(xprt, struct sock_xprt, xprt);
        struct socket *sock = transport->sock;
        unsigned long headoff;
        unsigned long tailoff;

        xs_encode_stream_record_marker(xbufp);

        tailoff = (unsigned long)xbufp->tail[0].iov_base & ~PAGE_MASK;
        headoff = (unsigned long)xbufp->head[0].iov_base & ~PAGE_MASK;
        len = svc_send_common(sock, xbufp,
                              virt_to_page(xbufp->head[0].iov_base), headoff,
                              xbufp->tail[0].iov_base, tailoff);

        if (len != xbufp->len) {
                printk(KERN_NOTICE "Error sending entire callback!\n");
                len = -EAGAIN;
        }

        return len;
}

/*
 * The send routine. Borrows from svc_send
 */
static int bc_send_request(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct svc_xprt *xprt;
        u32                     len;

        dprintk("sending request with xid: %08x\n", ntohl(req->rq_xid));
        /*
         * Get the server socket associated with this callback xprt
         */
        xprt = req->rq_xprt->bc_xprt;

        /*
         * Grab the mutex to serialize data as the connection is shared
         * with the fore channel
         */
        if (!mutex_trylock(&xprt->xpt_mutex)) {
                rpc_sleep_on(&xprt->xpt_bc_pending, task, NULL);
                if (!mutex_trylock(&xprt->xpt_mutex))
                        return -EAGAIN;
                rpc_wake_up_queued_task(&xprt->xpt_bc_pending, task);
        }
        if (test_bit(XPT_DEAD, &xprt->xpt_flags))
                len = -ENOTCONN;
        else
                len = bc_sendto(req);
        mutex_unlock(&xprt->xpt_mutex);

        if (len > 0)
                len = 0;

        return len;
}

/*
 * The close routine. Since this is client initiated, we do nothing
 */

static void bc_close(struct rpc_xprt *xprt)
{
}

/*
 * The xprt destroy routine. Again, because this connection is client
 * initiated, we do nothing
 */

static void bc_destroy(struct rpc_xprt *xprt)
{
        dprintk("RPC:       bc_destroy xprt %p\n", xprt);

        xs_xprt_free(xprt);
        module_put(THIS_MODULE);
}

static struct rpc_xprt_ops xs_local_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xs_tcp_release_xprt,
        .alloc_slot             = xprt_alloc_slot,
        .rpcbind                = xs_local_rpcbind,
        .set_port               = xs_local_set_port,
        .connect                = xs_local_connect,
        .buf_alloc              = rpc_malloc,
        .buf_free               = rpc_free,
        .send_request           = xs_local_send_request,
        .set_retrans_timeout    = xprt_set_retrans_timeout_def,
        .close                  = xs_close,
        .destroy                = xs_destroy,
        .print_stats            = xs_local_print_stats,
        .enable_swap            = xs_enable_swap,
        .disable_swap           = xs_disable_swap,
};

static struct rpc_xprt_ops xs_udp_ops = {
        .set_buffer_size        = xs_udp_set_buffer_size,
        .reserve_xprt           = xprt_reserve_xprt_cong,
        .release_xprt           = xprt_release_xprt_cong,
        .alloc_slot             = xprt_alloc_slot,
        .rpcbind                = rpcb_getport_async,
        .set_port               = xs_set_port,
        .connect                = xs_connect,
        .buf_alloc              = rpc_malloc,
        .buf_free               = rpc_free,
        .send_request           = xs_udp_send_request,
        .set_retrans_timeout    = xprt_set_retrans_timeout_rtt,
        .timer                  = xs_udp_timer,
        .release_request        = xprt_release_rqst_cong,
        .close                  = xs_close,
        .destroy                = xs_destroy,
        .print_stats            = xs_udp_print_stats,
        .enable_swap            = xs_enable_swap,
        .disable_swap           = xs_disable_swap,
        .inject_disconnect      = xs_inject_disconnect,
};

static struct rpc_xprt_ops xs_tcp_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xs_tcp_release_xprt,
        .alloc_slot             = xprt_lock_and_alloc_slot,
        .rpcbind                = rpcb_getport_async,
        .set_port               = xs_set_port,
        .connect                = xs_connect,
        .buf_alloc              = rpc_malloc,
        .buf_free               = rpc_free,
        .send_request           = xs_tcp_send_request,
        .set_retrans_timeout    = xprt_set_retrans_timeout_def,
        .close                  = xs_tcp_shutdown,
        .destroy                = xs_destroy,
        .print_stats            = xs_tcp_print_stats,
        .enable_swap            = xs_enable_swap,
        .disable_swap           = xs_disable_swap,
        .inject_disconnect      = xs_inject_disconnect,
};

/*
 * The rpc_xprt_ops for the server backchannel
 */

static struct rpc_xprt_ops bc_tcp_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xprt_release_xprt,
        .alloc_slot             = xprt_alloc_slot,
        .buf_alloc              = bc_malloc,
        .buf_free               = bc_free,
        .send_request           = bc_send_request,
        .set_retrans_timeout    = xprt_set_retrans_timeout_def,
        .close                  = bc_close,
        .destroy                = bc_destroy,
        .print_stats            = xs_tcp_print_stats,
        .enable_swap            = xs_enable_swap,
        .disable_swap           = xs_disable_swap,
        .inject_disconnect      = xs_inject_disconnect,
};

static int xs_init_anyaddr(const int family, struct sockaddr *sap)
{
        static const struct sockaddr_in sin = {
                .sin_family             = AF_INET,
                .sin_addr.s_addr        = htonl(INADDR_ANY),
        };
        static const struct sockaddr_in6 sin6 = {
                .sin6_family            = AF_INET6,
                .sin6_addr              = IN6ADDR_ANY_INIT,
        };

        switch (family) {
        case AF_LOCAL:
                break;
        case AF_INET:
                memcpy(sap, &sin, sizeof(sin));
                break;
        case AF_INET6:
                memcpy(sap, &sin6, sizeof(sin6));
                break;
        default:
                dprintk("RPC:       %s: Bad address family\n", __func__);
                return -EAFNOSUPPORT;
        }
        return 0;
}

static struct rpc_xprt *xs_setup_xprt(struct xprt_create *args,
                                      unsigned int slot_table_size,
                                      unsigned int max_slot_table_size)
{
        struct rpc_xprt *xprt;
        struct sock_xprt *new;

        if (args->addrlen > sizeof(xprt->addr)) {
                dprintk("RPC:       xs_setup_xprt: address too large\n");
                return ERR_PTR(-EBADF);
        }

        xprt = xprt_alloc(args->net, sizeof(*new), slot_table_size,
                        max_slot_table_size);
        if (xprt == NULL) {
                dprintk("RPC:       xs_setup_xprt: couldn't allocate "
                                "rpc_xprt\n");
                return ERR_PTR(-ENOMEM);
        }

        new = container_of(xprt, struct sock_xprt, xprt);
        memcpy(&xprt->addr, args->dstaddr, args->addrlen);
        xprt->addrlen = args->addrlen;
        if (args->srcaddr)
                memcpy(&new->srcaddr, args->srcaddr, args->addrlen);
        else {
                int err;
                err = xs_init_anyaddr(args->dstaddr->sa_family,
                                        (struct sockaddr *)&new->srcaddr);
                if (err != 0) {
                        xprt_free(xprt);
                        return ERR_PTR(err);
                }
        }

        return xprt;
}

static const struct rpc_timeout xs_local_default_timeout = {
        .to_initval = 10 * HZ,
        .to_maxval = 10 * HZ,
        .to_retries = 2,
};

/**
 * xs_setup_local - Set up transport to use an AF_LOCAL socket
 * @args: rpc transport creation arguments
 *
 * AF_LOCAL is a "tpi_cots_ord" transport, just like TCP
 */
static struct rpc_xprt *xs_setup_local(struct xprt_create *args)
{
        struct sockaddr_un *sun = (struct sockaddr_un *)args->dstaddr;
        struct sock_xprt *transport;
        struct rpc_xprt *xprt;
        struct rpc_xprt *ret;

        xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries,
                        xprt_max_tcp_slot_table_entries);
        if (IS_ERR(xprt))
                return xprt;
        transport = container_of(xprt, struct sock_xprt, xprt);

        xprt->prot = 0;
        xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
        xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;

        xprt->bind_timeout = XS_BIND_TO;
        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
        xprt->idle_timeout = XS_IDLE_DISC_TO;

        xprt->ops = &xs_local_ops;
        xprt->timeout = &xs_local_default_timeout;

        INIT_DELAYED_WORK(&transport->connect_worker,
                        xs_dummy_setup_socket);

        switch (sun->sun_family) {
        case AF_LOCAL:
                if (sun->sun_path[0] != '/') {
                        dprintk("RPC:       bad AF_LOCAL address: %s\n",
                                        sun->sun_path);
                        ret = ERR_PTR(-EINVAL);
                        goto out_err;
                }
                xprt_set_bound(xprt);
                xs_format_peer_addresses(xprt, "local", RPCBIND_NETID_LOCAL);
                ret = ERR_PTR(xs_local_setup_socket(transport));
                if (ret)
                        goto out_err;
                break;
        default:
                ret = ERR_PTR(-EAFNOSUPPORT);
                goto out_err;
        }

        dprintk("RPC:       set up xprt to %s via AF_LOCAL\n",
                        xprt->address_strings[RPC_DISPLAY_ADDR]);

        if (try_module_get(THIS_MODULE))
                return xprt;
        ret = ERR_PTR(-EINVAL);
out_err:
        xs_xprt_free(xprt);
        return ret;
}

static const struct rpc_timeout xs_udp_default_timeout = {
        .to_initval = 5 * HZ,
        .to_maxval = 30 * HZ,
        .to_increment = 5 * HZ,
        .to_retries = 5,
};

/**
 * xs_setup_udp - Set up transport to use a UDP socket
 * @args: rpc transport creation arguments
 *
 */
static struct rpc_xprt *xs_setup_udp(struct xprt_create *args)
{
        struct sockaddr *addr = args->dstaddr;
        struct rpc_xprt *xprt;
        struct sock_xprt *transport;
        struct rpc_xprt *ret;

        xprt = xs_setup_xprt(args, xprt_udp_slot_table_entries,
                        xprt_udp_slot_table_entries);
        if (IS_ERR(xprt))
                return xprt;
        transport = container_of(xprt, struct sock_xprt, xprt);

        xprt->prot = IPPROTO_UDP;
        xprt->tsh_size = 0;
        /* XXX: header size can vary due to auth type, IPv6, etc. */
        xprt->max_payload = (1U << 16) - (MAX_HEADER << 3);

        xprt->bind_timeout = XS_BIND_TO;
        xprt->reestablish_timeout = XS_UDP_REEST_TO;
        xprt->idle_timeout = XS_IDLE_DISC_TO;

        xprt->ops = &xs_udp_ops;

        xprt->timeout = &xs_udp_default_timeout;

        switch (addr->sa_family) {
        case AF_INET:
                if (((struct sockaddr_in *)addr)->sin_port != htons(0))
                        xprt_set_bound(xprt);

                INIT_DELAYED_WORK(&transport->connect_worker,
                                        xs_udp_setup_socket);
                xs_format_peer_addresses(xprt, "udp", RPCBIND_NETID_UDP);
                break;
        case AF_INET6:
                if (((struct sockaddr_in6 *)addr)->sin6_port != htons(0))
                        xprt_set_bound(xprt);

                INIT_DELAYED_WORK(&transport->connect_worker,
                                        xs_udp_setup_socket);
                xs_format_peer_addresses(xprt, "udp", RPCBIND_NETID_UDP6);
                break;
        default:
                ret = ERR_PTR(-EAFNOSUPPORT);
                goto out_err;
        }

        if (xprt_bound(xprt))
                dprintk("RPC:       set up xprt to %s (port %s) via %s\n",
                                xprt->address_strings[RPC_DISPLAY_ADDR],
                                xprt->address_strings[RPC_DISPLAY_PORT],
                                xprt->address_strings[RPC_DISPLAY_PROTO]);
        else
                dprintk("RPC:       set up xprt to %s (autobind) via %s\n",
                                xprt->address_strings[RPC_DISPLAY_ADDR],
                                xprt->address_strings[RPC_DISPLAY_PROTO]);

        if (try_module_get(THIS_MODULE))
                return xprt;
        ret = ERR_PTR(-EINVAL);
out_err:
        xs_xprt_free(xprt);
        return ret;
}

static const struct rpc_timeout xs_tcp_default_timeout = {
        .to_initval = 60 * HZ,
        .to_maxval = 60 * HZ,
        .to_retries = 2,
};

/**
 * xs_setup_tcp - Set up transport to use a TCP socket
 * @args: rpc transport creation arguments
 *
 */
static struct rpc_xprt *xs_setup_tcp(struct xprt_create *args)
{
        struct sockaddr *addr = args->dstaddr;
        struct rpc_xprt *xprt;
        struct sock_xprt *transport;
        struct rpc_xprt *ret;
        unsigned int max_slot_table_size = xprt_max_tcp_slot_table_entries;

        if (args->flags & XPRT_CREATE_INFINITE_SLOTS)
                max_slot_table_size = RPC_MAX_SLOT_TABLE_LIMIT;

        xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries,
                        max_slot_table_size);
        if (IS_ERR(xprt))
                return xprt;
        transport = container_of(xprt, struct sock_xprt, xprt);

        xprt->prot = IPPROTO_TCP;
        xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
        xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;

        xprt->bind_timeout = XS_BIND_TO;
        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
        xprt->idle_timeout = XS_IDLE_DISC_TO;

        xprt->ops = &xs_tcp_ops;
        xprt->timeout = &xs_tcp_default_timeout;

        switch (addr->sa_family) {
        case AF_INET:
                if (((struct sockaddr_in *)addr)->sin_port != htons(0))
                        xprt_set_bound(xprt);

                INIT_DELAYED_WORK(&transport->connect_worker,
                                        xs_tcp_setup_socket);
                xs_format_peer_addresses(xprt, "tcp", RPCBIND_NETID_TCP);
                break;
        case AF_INET6:
                if (((struct sockaddr_in6 *)addr)->sin6_port != htons(0))
                        xprt_set_bound(xprt);

                INIT_DELAYED_WORK(&transport->connect_worker,
                                        xs_tcp_setup_socket);
                xs_format_peer_addresses(xprt, "tcp", RPCBIND_NETID_TCP6);
                break;
        default:
                ret = ERR_PTR(-EAFNOSUPPORT);
                goto out_err;
        }

        if (xprt_bound(xprt))
                dprintk("RPC:       set up xprt to %s (port %s) via %s\n",
                                xprt->address_strings[RPC_DISPLAY_ADDR],
                                xprt->address_strings[RPC_DISPLAY_PORT],
                                xprt->address_strings[RPC_DISPLAY_PROTO]);
        else
                dprintk("RPC:       set up xprt to %s (autobind) via %s\n",
                                xprt->address_strings[RPC_DISPLAY_ADDR],
                                xprt->address_strings[RPC_DISPLAY_PROTO]);

        if (try_module_get(THIS_MODULE))
                return xprt;
        ret = ERR_PTR(-EINVAL);
out_err:
        xs_xprt_free(xprt);
        return ret;
}

/**
 * xs_setup_bc_tcp - Set up transport to use a TCP backchannel socket
 * @args: rpc transport creation arguments
 *
 */
static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
{
        struct sockaddr *addr = args->dstaddr;
        struct rpc_xprt *xprt;
        struct sock_xprt *transport;
        struct svc_sock *bc_sock;
        struct rpc_xprt *ret;

        xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries,
                        xprt_tcp_slot_table_entries);
        if (IS_ERR(xprt))
                return xprt;
        transport = container_of(xprt, struct sock_xprt, xprt);

        xprt->prot = IPPROTO_TCP;
        xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
        xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
        xprt->timeout = &xs_tcp_default_timeout;

        /* backchannel */
        xprt_set_bound(xprt);
        xprt->bind_timeout = 0;
        xprt->reestablish_timeout = 0;
        xprt->idle_timeout = 0;

        xprt->ops = &bc_tcp_ops;

        switch (addr->sa_family) {
        case AF_INET:
                xs_format_peer_addresses(xprt, "tcp",
                                         RPCBIND_NETID_TCP);
                break;
        case AF_INET6:
                xs_format_peer_addresses(xprt, "tcp",
                                   RPCBIND_NETID_TCP6);
                break;
        default:
                ret = ERR_PTR(-EAFNOSUPPORT);
                goto out_err;
        }

        dprintk("RPC:       set up xprt to %s (port %s) via %s\n",
                        xprt->address_strings[RPC_DISPLAY_ADDR],
                        xprt->address_strings[RPC_DISPLAY_PORT],
                        xprt->address_strings[RPC_DISPLAY_PROTO]);

        /*
         * Once we've associated a backchannel xprt with a connection,
         * we want to keep it around as long as the connection lasts,
         * in case we need to start using it for a backchannel again;
         * this reference won't be dropped until bc_xprt is destroyed.
         */
        xprt_get(xprt);
        args->bc_xprt->xpt_bc_xprt = xprt;
        xprt->bc_xprt = args->bc_xprt;
        bc_sock = container_of(args->bc_xprt, struct svc_sock, sk_xprt);
        transport->sock = bc_sock->sk_sock;
        transport->inet = bc_sock->sk_sk;

        /*
         * Since we don't want connections for the backchannel, we set
         * the xprt status to connected
         */
        xprt_set_connected(xprt);

        if (try_module_get(THIS_MODULE))
                return xprt;

        args->bc_xprt->xpt_bc_xprt = NULL;
        xprt_put(xprt);
        ret = ERR_PTR(-EINVAL);
out_err:
        xs_xprt_free(xprt);
        return ret;
}

static struct xprt_class        xs_local_transport = {
        .list           = LIST_HEAD_INIT(xs_local_transport.list),
        .name           = "named UNIX socket",
        .owner          = THIS_MODULE,
        .ident          = XPRT_TRANSPORT_LOCAL,
        .setup          = xs_setup_local,
};

static struct xprt_class        xs_udp_transport = {
        .list           = LIST_HEAD_INIT(xs_udp_transport.list),
        .name           = "udp",
        .owner          = THIS_MODULE,
        .ident          = XPRT_TRANSPORT_UDP,
        .setup          = xs_setup_udp,
};

static struct xprt_class        xs_tcp_transport = {
        .list           = LIST_HEAD_INIT(xs_tcp_transport.list),
        .name           = "tcp",
        .owner          = THIS_MODULE,
        .ident          = XPRT_TRANSPORT_TCP,
        .setup          = xs_setup_tcp,
};

static struct xprt_class        xs_bc_tcp_transport = {
        .list           = LIST_HEAD_INIT(xs_bc_tcp_transport.list),
        .name           = "tcp NFSv4.1 backchannel",
        .owner          = THIS_MODULE,
        .ident          = XPRT_TRANSPORT_BC_TCP,
        .setup          = xs_setup_bc_tcp,
};

/**
 * init_socket_xprt - set up xprtsock's sysctls, register with RPC client
 *
 */
int init_socket_xprt(void)
{
#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
        if (!sunrpc_table_header)
                sunrpc_table_header = register_sysctl_table(sunrpc_table);
#endif

        xprt_register_transport(&xs_local_transport);
        xprt_register_transport(&xs_udp_transport);
        xprt_register_transport(&xs_tcp_transport);
        xprt_register_transport(&xs_bc_tcp_transport);

        return 0;
}

/**
 * cleanup_socket_xprt - remove xprtsock's sysctls, unregister
 *
 */
void cleanup_socket_xprt(void)
{
#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
        if (sunrpc_table_header) {
                unregister_sysctl_table(sunrpc_table_header);
                sunrpc_table_header = NULL;
        }
#endif

        xprt_unregister_transport(&xs_local_transport);
        xprt_unregister_transport(&xs_udp_transport);
        xprt_unregister_transport(&xs_tcp_transport);
        xprt_unregister_transport(&xs_bc_tcp_transport);
}

static int param_set_uint_minmax(const char *val,
                const struct kernel_param *kp,
                unsigned int min, unsigned int max)
{
        unsigned int num;
        int ret;

        if (!val)
                return -EINVAL;
        ret = kstrtouint(val, 0, &num);
        if (ret == -EINVAL || num < min || num > max)
                return -EINVAL;
        *((unsigned int *)kp->arg) = num;
        return 0;
}

static int param_set_portnr(const char *val, const struct kernel_param *kp)
{
        return param_set_uint_minmax(val, kp,
                        RPC_MIN_RESVPORT,
                        RPC_MAX_RESVPORT);
}

static const struct kernel_param_ops param_ops_portnr = {
        .set = param_set_portnr,
        .get = param_get_uint,
};

#define param_check_portnr(name, p) \
        __param_check(name, p, unsigned int);

module_param_named(min_resvport, xprt_min_resvport, portnr, 0644);
module_param_named(max_resvport, xprt_max_resvport, portnr, 0644);

static int param_set_slot_table_size(const char *val,
                                     const struct kernel_param *kp)
{
        return param_set_uint_minmax(val, kp,
                        RPC_MIN_SLOT_TABLE,
                        RPC_MAX_SLOT_TABLE);
}

static const struct kernel_param_ops param_ops_slot_table_size = {
        .set = param_set_slot_table_size,
        .get = param_get_uint,
};

#define param_check_slot_table_size(name, p) \
        __param_check(name, p, unsigned int);

static int param_set_max_slot_table_size(const char *val,
                                     const struct kernel_param *kp)
{
        return param_set_uint_minmax(val, kp,
                        RPC_MIN_SLOT_TABLE,
                        RPC_MAX_SLOT_TABLE_LIMIT);
}

static const struct kernel_param_ops param_ops_max_slot_table_size = {
        .set = param_set_max_slot_table_size,
        .get = param_get_uint,
};

#define param_check_max_slot_table_size(name, p) \
        __param_check(name, p, unsigned int);

module_param_named(tcp_slot_table_entries, xprt_tcp_slot_table_entries,
                   slot_table_size, 0644);
module_param_named(tcp_max_slot_table_entries, xprt_max_tcp_slot_table_entries,
                   max_slot_table_size, 0644);
module_param_named(udp_slot_table_entries, xprt_udp_slot_table_entries,
                   slot_table_size, 0644);