Merge tag 'io_uring-5.13-2021-05-07' of git://git.kernel.dk/linux-block

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

// SPDX-License-Identifier: GPL-2.0
/*
 * 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 <linux/bvec.h>
#include <linux/highmem.h>
#include <linux/uio.h>
#include <linux/sched/mm.h>

#include <trace/events/sunrpc.h>

#include "socklib.h"
#include "sunrpc.h"

static void xs_close(struct rpc_xprt *xprt);
static void xs_tcp_set_socket_timeouts(struct rpc_xprt *xprt,
                struct socket *sock);

/*
 * 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;

#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
        },
        { },
};

/*
 * 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)

/*
 * 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]);
                }
}

static size_t
xs_alloc_sparse_pages(struct xdr_buf *buf, size_t want, gfp_t gfp)
{
        size_t i,n;

        if (!want || !(buf->flags & XDRBUF_SPARSE_PAGES))
                return want;
        n = (buf->page_base + want + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < n; i++) {
                if (buf->pages[i])
                        continue;
                buf->bvec[i].bv_page = buf->pages[i] = alloc_page(gfp);
                if (!buf->pages[i]) {
                        i *= PAGE_SIZE;
                        return i > buf->page_base ? i - buf->page_base : 0;
                }
        }
        return want;
}

static ssize_t
xs_sock_recvmsg(struct socket *sock, struct msghdr *msg, int flags, size_t seek)
{
        ssize_t ret;
        if (seek != 0)
                iov_iter_advance(&msg->msg_iter, seek);
        ret = sock_recvmsg(sock, msg, flags);
        return ret > 0 ? ret + seek : ret;
}

static ssize_t
xs_read_kvec(struct socket *sock, struct msghdr *msg, int flags,
                struct kvec *kvec, size_t count, size_t seek)
{
        iov_iter_kvec(&msg->msg_iter, READ, kvec, 1, count);
        return xs_sock_recvmsg(sock, msg, flags, seek);
}

static ssize_t
xs_read_bvec(struct socket *sock, struct msghdr *msg, int flags,
                struct bio_vec *bvec, unsigned long nr, size_t count,
                size_t seek)
{
        iov_iter_bvec(&msg->msg_iter, READ, bvec, nr, count);
        return xs_sock_recvmsg(sock, msg, flags, seek);
}

static ssize_t
xs_read_discard(struct socket *sock, struct msghdr *msg, int flags,
                size_t count)
{
        iov_iter_discard(&msg->msg_iter, READ, count);
        return sock_recvmsg(sock, msg, flags);
}

#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
static void
xs_flush_bvec(const struct bio_vec *bvec, size_t count, size_t seek)
{
        struct bvec_iter bi = {
                .bi_size = count,
        };
        struct bio_vec bv;

        bvec_iter_advance(bvec, &bi, seek & PAGE_MASK);
        for_each_bvec(bv, bvec, bi, bi)
                flush_dcache_page(bv.bv_page);
}
#else
static inline void
xs_flush_bvec(const struct bio_vec *bvec, size_t count, size_t seek)
{
}
#endif

static ssize_t
xs_read_xdr_buf(struct socket *sock, struct msghdr *msg, int flags,
                struct xdr_buf *buf, size_t count, size_t seek, size_t *read)
{
        size_t want, seek_init = seek, offset = 0;
        ssize_t ret;

        want = min_t(size_t, count, buf->head[0].iov_len);
        if (seek < want) {
                ret = xs_read_kvec(sock, msg, flags, &buf->head[0], want, seek);
                if (ret <= 0)
                        goto sock_err;
                offset += ret;
                if (offset == count || msg->msg_flags & (MSG_EOR|MSG_TRUNC))
                        goto out;
                if (ret != want)
                        goto out;
                seek = 0;
        } else {
                seek -= want;
                offset += want;
        }

        want = xs_alloc_sparse_pages(buf,
                        min_t(size_t, count - offset, buf->page_len),
                        GFP_KERNEL);
        if (seek < want) {
                ret = xs_read_bvec(sock, msg, flags, buf->bvec,
                                xdr_buf_pagecount(buf),
                                want + buf->page_base,
                                seek + buf->page_base);
                if (ret <= 0)
                        goto sock_err;
                xs_flush_bvec(buf->bvec, ret, seek + buf->page_base);
                ret -= buf->page_base;
                offset += ret;
                if (offset == count || msg->msg_flags & (MSG_EOR|MSG_TRUNC))
                        goto out;
                if (ret != want)
                        goto out;
                seek = 0;
        } else {
                seek -= want;
                offset += want;
        }

        want = min_t(size_t, count - offset, buf->tail[0].iov_len);
        if (seek < want) {
                ret = xs_read_kvec(sock, msg, flags, &buf->tail[0], want, seek);
                if (ret <= 0)
                        goto sock_err;
                offset += ret;
                if (offset == count || msg->msg_flags & (MSG_EOR|MSG_TRUNC))
                        goto out;
                if (ret != want)
                        goto out;
        } else if (offset < seek_init)
                offset = seek_init;
        ret = -EMSGSIZE;
out:
        *read = offset - seek_init;
        return ret;
sock_err:
        offset += seek;
        goto out;
}

static void
xs_read_header(struct sock_xprt *transport, struct xdr_buf *buf)
{
        if (!transport->recv.copied) {
                if (buf->head[0].iov_len >= transport->recv.offset)
                        memcpy(buf->head[0].iov_base,
                                        &transport->recv.xid,
                                        transport->recv.offset);
                transport->recv.copied = transport->recv.offset;
        }
}

static bool
xs_read_stream_request_done(struct sock_xprt *transport)
{
        return transport->recv.fraghdr & cpu_to_be32(RPC_LAST_STREAM_FRAGMENT);
}

static void
xs_read_stream_check_eor(struct sock_xprt *transport,
                struct msghdr *msg)
{
        if (xs_read_stream_request_done(transport))
                msg->msg_flags |= MSG_EOR;
}

static ssize_t
xs_read_stream_request(struct sock_xprt *transport, struct msghdr *msg,
                int flags, struct rpc_rqst *req)
{
        struct xdr_buf *buf = &req->rq_private_buf;
        size_t want, read;
        ssize_t ret;

        xs_read_header(transport, buf);

        want = transport->recv.len - transport->recv.offset;
        if (want != 0) {
                ret = xs_read_xdr_buf(transport->sock, msg, flags, buf,
                                transport->recv.copied + want,
                                transport->recv.copied,
                                &read);
                transport->recv.offset += read;
                transport->recv.copied += read;
        }

        if (transport->recv.offset == transport->recv.len)
                xs_read_stream_check_eor(transport, msg);

        if (want == 0)
                return 0;

        switch (ret) {
        default:
                break;
        case -EFAULT:
        case -EMSGSIZE:
                msg->msg_flags |= MSG_TRUNC;
                return read;
        case 0:
                return -ESHUTDOWN;
        }
        return ret < 0 ? ret : read;
}

static size_t
xs_read_stream_headersize(bool isfrag)
{
        if (isfrag)
                return sizeof(__be32);
        return 3 * sizeof(__be32);
}

static ssize_t
xs_read_stream_header(struct sock_xprt *transport, struct msghdr *msg,
                int flags, size_t want, size_t seek)
{
        struct kvec kvec = {
                .iov_base = &transport->recv.fraghdr,
                .iov_len = want,
        };
        return xs_read_kvec(transport->sock, msg, flags, &kvec, want, seek);
}

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
static ssize_t
xs_read_stream_call(struct sock_xprt *transport, struct msghdr *msg, int flags)
{
        struct rpc_xprt *xprt = &transport->xprt;
        struct rpc_rqst *req;
        ssize_t ret;

        /* Is this transport associated with the backchannel? */
        if (!xprt->bc_serv)
                return -ESHUTDOWN;

        /* Look up and lock the request corresponding to the given XID */
        req = xprt_lookup_bc_request(xprt, transport->recv.xid);
        if (!req) {
                printk(KERN_WARNING "Callback slot table overflowed\n");
                return -ESHUTDOWN;
        }
        if (transport->recv.copied && !req->rq_private_buf.len)
                return -ESHUTDOWN;

        ret = xs_read_stream_request(transport, msg, flags, req);
        if (msg->msg_flags & (MSG_EOR|MSG_TRUNC))
                xprt_complete_bc_request(req, transport->recv.copied);
        else
                req->rq_private_buf.len = transport->recv.copied;

        return ret;
}
#else /* CONFIG_SUNRPC_BACKCHANNEL */
static ssize_t
xs_read_stream_call(struct sock_xprt *transport, struct msghdr *msg, int flags)
{
        return -ESHUTDOWN;
}
#endif /* CONFIG_SUNRPC_BACKCHANNEL */

static ssize_t
xs_read_stream_reply(struct sock_xprt *transport, struct msghdr *msg, int flags)
{
        struct rpc_xprt *xprt = &transport->xprt;
        struct rpc_rqst *req;
        ssize_t ret = 0;

        /* Look up and lock the request corresponding to the given XID */
        spin_lock(&xprt->queue_lock);
        req = xprt_lookup_rqst(xprt, transport->recv.xid);
        if (!req || (transport->recv.copied && !req->rq_private_buf.len)) {
                msg->msg_flags |= MSG_TRUNC;
                goto out;
        }
        xprt_pin_rqst(req);
        spin_unlock(&xprt->queue_lock);

        ret = xs_read_stream_request(transport, msg, flags, req);

        spin_lock(&xprt->queue_lock);
        if (msg->msg_flags & (MSG_EOR|MSG_TRUNC))
                xprt_complete_rqst(req->rq_task, transport->recv.copied);
        else
                req->rq_private_buf.len = transport->recv.copied;
        xprt_unpin_rqst(req);
out:
        spin_unlock(&xprt->queue_lock);
        return ret;
}

static ssize_t
xs_read_stream(struct sock_xprt *transport, int flags)
{
        struct msghdr msg = { 0 };
        size_t want, read = 0;
        ssize_t ret = 0;

        if (transport->recv.len == 0) {
                want = xs_read_stream_headersize(transport->recv.copied != 0);
                ret = xs_read_stream_header(transport, &msg, flags, want,
                                transport->recv.offset);
                if (ret <= 0)
                        goto out_err;
                transport->recv.offset = ret;
                if (transport->recv.offset != want)
                        return transport->recv.offset;
                transport->recv.len = be32_to_cpu(transport->recv.fraghdr) &
                        RPC_FRAGMENT_SIZE_MASK;
                transport->recv.offset -= sizeof(transport->recv.fraghdr);
                read = ret;
        }

        switch (be32_to_cpu(transport->recv.calldir)) {
        default:
                msg.msg_flags |= MSG_TRUNC;
                break;
        case RPC_CALL:
                ret = xs_read_stream_call(transport, &msg, flags);
                break;
        case RPC_REPLY:
                ret = xs_read_stream_reply(transport, &msg, flags);
        }
        if (msg.msg_flags & MSG_TRUNC) {
                transport->recv.calldir = cpu_to_be32(-1);
                transport->recv.copied = -1;
        }
        if (ret < 0)
                goto out_err;
        read += ret;
        if (transport->recv.offset < transport->recv.len) {
                if (!(msg.msg_flags & MSG_TRUNC))
                        return read;
                msg.msg_flags = 0;
                ret = xs_read_discard(transport->sock, &msg, flags,
                                transport->recv.len - transport->recv.offset);
                if (ret <= 0)
                        goto out_err;
                transport->recv.offset += ret;
                read += ret;
                if (transport->recv.offset != transport->recv.len)
                        return read;
        }
        if (xs_read_stream_request_done(transport)) {
                trace_xs_stream_read_request(transport);
                transport->recv.copied = 0;
        }
        transport->recv.offset = 0;
        transport->recv.len = 0;
        return read;
out_err:
        return ret != 0 ? ret : -ESHUTDOWN;
}

static __poll_t xs_poll_socket(struct sock_xprt *transport)
{
        return transport->sock->ops->poll(transport->file, transport->sock,
                        NULL);
}

static bool xs_poll_socket_readable(struct sock_xprt *transport)
{
        __poll_t events = xs_poll_socket(transport);

        return (events & (EPOLLIN | EPOLLRDNORM)) && !(events & EPOLLRDHUP);
}

static void xs_poll_check_readable(struct sock_xprt *transport)
{

        clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
        if (!xs_poll_socket_readable(transport))
                return;
        if (!test_and_set_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
                queue_work(xprtiod_workqueue, &transport->recv_worker);
}

static void xs_stream_data_receive(struct sock_xprt *transport)
{
        size_t read = 0;
        ssize_t ret = 0;

        mutex_lock(&transport->recv_mutex);
        if (transport->sock == NULL)
                goto out;
        for (;;) {
                ret = xs_read_stream(transport, MSG_DONTWAIT);
                if (ret < 0)
                        break;
                read += ret;
                cond_resched();
        }
        if (ret == -ESHUTDOWN)
                kernel_sock_shutdown(transport->sock, SHUT_RDWR);
        else
                xs_poll_check_readable(transport);
out:
        mutex_unlock(&transport->recv_mutex);
        trace_xs_stream_read_data(&transport->xprt, ret, read);
}

static void xs_stream_data_receive_workfn(struct work_struct *work)
{
        struct sock_xprt *transport =
                container_of(work, struct sock_xprt, recv_worker);
        unsigned int pflags = memalloc_nofs_save();

        xs_stream_data_receive(transport);
        memalloc_nofs_restore(pflags);
}

static void
xs_stream_reset_connect(struct sock_xprt *transport)
{
        transport->recv.offset = 0;
        transport->recv.len = 0;
        transport->recv.copied = 0;
        transport->xmit.offset = 0;
}

static void
xs_stream_start_connect(struct sock_xprt *transport)
{
        transport->xprt.stat.connect_count++;
        transport->xprt.stat.connect_start = jiffies;
}

#define XS_SENDMSG_FLAGS        (MSG_DONTWAIT | MSG_NOSIGNAL)

/**
 * xs_nospace - handle transmit was incomplete
 * @req: pointer to RPC request
 *
 */
static int xs_nospace(struct rpc_rqst *req)
{
        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;

        trace_rpc_socket_nospace(req, transport);

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

        /* Don't race with disconnect */
        if (xprt_connected(xprt)) {
                /* wait for more buffer space */
                sk->sk_write_pending++;
                xprt_wait_for_buffer_space(xprt);
        } else
                ret = -ENOTCONN;

        spin_unlock(&xprt->transport_lock);

        /* Race breaker in case memory is freed before above code is called */
        if (ret == -EAGAIN) {
                struct socket_wq *wq;

                rcu_read_lock();
                wq = rcu_dereference(sk->sk_wq);
                set_bit(SOCKWQ_ASYNC_NOSPACE, &wq->flags);
                rcu_read_unlock();

                sk->sk_write_space(sk);
        }
        return ret;
}

static void
xs_stream_prepare_request(struct rpc_rqst *req)
{
        xdr_free_bvec(&req->rq_rcv_buf);
        req->rq_task->tk_status = xdr_alloc_bvec(&req->rq_rcv_buf, GFP_KERNEL);
}

/*
 * Determine if the previous message in the stream was aborted before it
 * could complete transmission.
 */
static bool
xs_send_request_was_aborted(struct sock_xprt *transport, struct rpc_rqst *req)
{
        return transport->xmit.offset != 0 && req->rq_bytes_sent == 0;
}

/*
 * Return the stream record marker field for a record of length < 2^31-1
 */
static rpc_fraghdr
xs_stream_record_marker(struct xdr_buf *xdr)
{
        if (!xdr->len)
                return 0;
        return cpu_to_be32(RPC_LAST_STREAM_FRAGMENT | (u32)xdr->len);
}

/**
 * xs_local_send_request - write an RPC request to an AF_LOCAL socket
 * @req: pointer to 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_local_send_request(struct rpc_rqst *req)
{
        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;
        rpc_fraghdr rm = xs_stream_record_marker(xdr);
        unsigned int msglen = rm ? req->rq_slen + sizeof(rm) : req->rq_slen;
        struct msghdr msg = {
                .msg_flags      = XS_SENDMSG_FLAGS,
        };
        unsigned int sent;
        int status;

        /* Close the stream if the previous transmission was incomplete */
        if (xs_send_request_was_aborted(transport, req)) {
                xs_close(xprt);
                return -ENOTCONN;
        }

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

        req->rq_xtime = ktime_get();
        status = xprt_sock_sendmsg(transport->sock, &msg, xdr,
                                   transport->xmit.offset, rm, &sent);
        dprintk("RPC:       %s(%u) = %d\n",
                        __func__, xdr->len - transport->xmit.offset, status);

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

        if (likely(sent > 0) || status == 0) {
                transport->xmit.offset += sent;
                req->rq_bytes_sent = transport->xmit.offset;
                if (likely(req->rq_bytes_sent >= msglen)) {
                        req->rq_xmit_bytes_sent += transport->xmit.offset;
                        transport->xmit.offset = 0;
                        return 0;
                }
                status = -EAGAIN;
        }

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

        return status;
}

/**
 * xs_udp_send_request - write an RPC request to a UDP socket
 * @req: pointer to 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_rqst *req)
{
        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;
        struct msghdr msg = {
                .msg_name       = xs_addr(xprt),
                .msg_namelen    = xprt->addrlen,
                .msg_flags      = XS_SENDMSG_FLAGS,
        };
        unsigned int sent;
        int status;

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

        if (!xprt_bound(xprt))
                return -ENOTCONN;

        if (!xprt_request_get_cong(xprt, req))
                return -EBADSLT;

        req->rq_xtime = ktime_get();
        status = xprt_sock_sendmsg(transport->sock, &msg, xdr, 0, 0, &sent);

        dprintk("RPC:       xs_udp_send_request(%u) = %d\n",
                        xdr->len, 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(req);
                break;
        case -ENETUNREACH:
        case -ENOBUFS:
        case -EPIPE:
        case -ECONNREFUSED:
        case -EPERM:
                /* When the server has died, an ICMP port unreachable message
                 * prompts ECONNREFUSED. */
                break;
        default:
                dprintk("RPC:       sendmsg returned unrecognized error %d\n",
                        -status);
        }

        return status;
}

/**
 * xs_tcp_send_request - write an RPC request to a TCP socket
 * @req: pointer to 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_rqst *req)
{
        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;
        rpc_fraghdr rm = xs_stream_record_marker(xdr);
        unsigned int msglen = rm ? req->rq_slen + sizeof(rm) : req->rq_slen;
        struct msghdr msg = {
                .msg_flags      = XS_SENDMSG_FLAGS,
        };
        bool vm_wait = false;
        unsigned int sent;
        int status;

        /* Close the stream if the previous transmission was incomplete */
        if (xs_send_request_was_aborted(transport, req)) {
                if (transport->sock != NULL)
                        kernel_sock_shutdown(transport->sock, SHUT_RDWR);
                return -ENOTCONN;
        }

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

        if (test_bit(XPRT_SOCK_UPD_TIMEOUT, &transport->sock_state))
                xs_tcp_set_socket_timeouts(xprt, transport->sock);

        /* Continue transmitting the packet/record. We must be careful
         * to cope with writespace callbacks arriving _after_ we have
         * called sendmsg(). */
        req->rq_xtime = ktime_get();
        tcp_sock_set_cork(transport->inet, true);
        while (1) {
                status = xprt_sock_sendmsg(transport->sock, &msg, xdr,
                                           transport->xmit.offset, rm, &sent);

                dprintk("RPC:       xs_tcp_send_request(%u) = %d\n",
                                xdr->len - transport->xmit.offset, status);

                /* If we've sent the entire packet, immediately
                 * reset the count of bytes sent. */
                transport->xmit.offset += sent;
                req->rq_bytes_sent = transport->xmit.offset;
                if (likely(req->rq_bytes_sent >= msglen)) {
                        req->rq_xmit_bytes_sent += transport->xmit.offset;
                        transport->xmit.offset = 0;
                        if (atomic_long_read(&xprt->xmit_queuelen) == 1)
                                tcp_sock_set_cork(transport->inet, false);
                        return 0;
                }

                WARN_ON_ONCE(sent == 0 && status == 0);

                if (status == -EAGAIN ) {
                        /*
                         * Return EAGAIN if we're sure we're hitting the
                         * socket send buffer limits.
                         */
                        if (test_bit(SOCK_NOSPACE, &transport->sock->flags))
                                break;
                        /*
                         * Did we hit a memory allocation failure?
                         */
                        if (sent == 0) {
                                status = -ENOBUFS;
                                if (vm_wait)
                                        break;
                                /* Retry, knowing now that we're below the
                                 * socket send buffer limit
                                 */
                                vm_wait = true;
                        }
                        continue;
                }
                if (status < 0)
                        break;
                vm_wait = false;
        }

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

        return status;
}

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_state_flags(struct rpc_xprt *xprt)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);

        clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
        clear_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state);
        clear_bit(XPRT_SOCK_WAKE_WRITE, &transport->sock_state);
        clear_bit(XPRT_SOCK_WAKE_DISCONNECT, &transport->sock_state);
}

static void xs_run_error_worker(struct sock_xprt *transport, unsigned int nr)
{
        set_bit(nr, &transport->sock_state);
        queue_work(xprtiod_workqueue, &transport->error_worker);
}

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);
        xs_sock_reset_state_flags(xprt);
        smp_mb__after_atomic();
}

/**
 * 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 sock_xprt *transport;
        struct rpc_xprt *xprt;

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

        transport = container_of(xprt, struct sock_xprt, xprt);
        transport->xprt_err = -sk->sk_err;
        if (transport->xprt_err == 0)
                goto out;
        dprintk("RPC:       xs_error_report client %p, error=%d...\n",
                        xprt, -transport->xprt_err);
        trace_rpc_socket_error(xprt, sk->sk_socket, transport->xprt_err);

        /* barrier ensures xprt_err is set before XPRT_SOCK_WAKE_ERROR */
        smp_mb__before_atomic();
        xs_run_error_worker(transport, XPRT_SOCK_WAKE_ERROR);
 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;
        struct file *filp = transport->file;

        if (sk == NULL)
                return;

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

        kernel_sock_shutdown(sock, SHUT_RDWR);

        mutex_lock(&transport->recv_mutex);
        write_lock_bh(&sk->sk_callback_lock);
        transport->inet = NULL;
        transport->sock = NULL;
        transport->file = 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);
        /* Reset stream record info */
        xs_stream_reset_connect(transport);
        mutex_unlock(&transport->recv_mutex);

        trace_rpc_socket_close(xprt, sock);
        fput(filp);

        xprt_disconnect_done(xprt);
}

/**
 * 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;
}

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);
        cancel_work_sync(&transport->recv_worker);
        cancel_work_sync(&transport->error_worker);
        xs_xprt_free(xprt);
        module_put(THIS_MODULE);
}

/**
 * xs_udp_data_read_skb - receive callback for UDP sockets
 * @xprt: transport
 * @sk: socket
 * @skb: skbuff
 *
 */
static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
                struct sock *sk,
                struct sk_buff *skb)
{
        struct rpc_task *task;
        struct rpc_rqst *rovr;
        int repsize, copied;
        u32 _xid;
        __be32 *xp;

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

        /* Copy the XID from the skb... */
        xp = skb_header_pointer(skb, 0, sizeof(_xid), &_xid);
        if (xp == NULL)
                return;

        /* Look up and lock the request corresponding to the given XID */
        spin_lock(&xprt->queue_lock);
        rovr = xprt_lookup_rqst(xprt, *xp);
        if (!rovr)
                goto out_unlock;
        xprt_pin_rqst(rovr);
        xprt_update_rtt(rovr->rq_task);
        spin_unlock(&xprt->queue_lock);
        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)) {
                spin_lock(&xprt->queue_lock);
                __UDPX_INC_STATS(sk, UDP_MIB_INERRORS);
                goto out_unpin;
        }


        spin_lock(&xprt->transport_lock);
        xprt_adjust_cwnd(xprt, task, copied);
        spin_unlock(&xprt->transport_lock);
        spin_lock(&xprt->queue_lock);
        xprt_complete_rqst(task, copied);
        __UDPX_INC_STATS(sk, UDP_MIB_INDATAGRAMS);
out_unpin:
        xprt_unpin_rqst(rovr);
 out_unlock:
        spin_unlock(&xprt->queue_lock);
}

static void xs_udp_data_receive(struct sock_xprt *transport)
{
        struct sk_buff *skb;
        struct sock *sk;
        int err;

        mutex_lock(&transport->recv_mutex);
        sk = transport->inet;
        if (sk == NULL)
                goto out;
        for (;;) {
                skb = skb_recv_udp(sk, 0, 1, &err);
                if (skb == NULL)
                        break;
                xs_udp_data_read_skb(&transport->xprt, sk, skb);
                consume_skb(skb);
                cond_resched();
        }
        xs_poll_check_readable(transport);
out:
        mutex_unlock(&transport->recv_mutex);
}

static void xs_udp_data_receive_workfn(struct work_struct *work)
{
        struct sock_xprt *transport =
                container_of(work, struct sock_xprt, recv_worker);
        unsigned int pflags = memalloc_nofs_save();

        xs_udp_data_receive(transport);
        memalloc_nofs_restore(pflags);
}

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

        read_lock_bh(&sk->sk_callback_lock);
        dprintk("RPC:       xs_data_ready...\n");
        xprt = xprt_from_sock(sk);
        if (xprt != NULL) {
                struct sock_xprt *transport = container_of(xprt,
                                struct sock_xprt, xprt);
                transport->old_data_ready(sk);
                /* Any data means we had a useful conversation, so
                 * then we don't need to delay the next reconnect
                 */
                if (xprt->reestablish_timeout)
                        xprt->reestablish_timeout = 0;
                if (!test_and_set_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
                        queue_work(xprtiod_workqueue, &transport->recv_worker);
        }
        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);
}

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
static size_t xs_tcp_bc_maxpayload(struct rpc_xprt *xprt)
{
        return PAGE_SIZE;
}
#endif /* CONFIG_SUNRPC_BACKCHANNEL */

/**
 * 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:
                if (!xprt_test_and_set_connected(xprt)) {
                        xprt->connect_cookie++;
                        clear_bit(XPRT_SOCK_CONNECTING, &transport->sock_state);
                        xprt_clear_connecting(xprt);

                        xprt->stat.connect_count++;
                        xprt->stat.connect_time += (long)jiffies -
                                                   xprt->stat.connect_start;
                        xs_run_error_worker(transport, XPRT_SOCK_WAKE_PENDING);
                }
                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_run_error_worker(transport, XPRT_SOCK_WAKE_DISCONNECT);
                fallthrough;
        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);
                clear_bit(XPRT_CLOSING, &xprt->state);
                /* Trigger the socket release */
                xs_run_error_worker(transport, XPRT_SOCK_WAKE_DISCONNECT);
        }
 out:
        read_unlock_bh(&sk->sk_callback_lock);
}

static void xs_write_space(struct sock *sk)
{
        struct socket_wq *wq;
        struct sock_xprt *transport;
        struct rpc_xprt *xprt;

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

        if (unlikely(!(xprt = xprt_from_sock(sk))))
                return;
        transport = container_of(xprt, struct sock_xprt, xprt);
        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (!wq || test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &wq->flags) == 0)
                goto out;

        xs_run_error_worker(transport, XPRT_SOCK_WAKE_WRITE);
        sk->sk_write_pending--;
out:
        rcu_read_unlock();
}

/**
 * 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
 * @xprt: controlling 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)
{
        spin_lock(&xprt->transport_lock);
        xprt_adjust_cwnd(xprt, task, -ETIMEDOUT);
        spin_unlock(&xprt->transport_lock);
}

static int xs_get_random_port(void)
{
        unsigned short min = xprt_min_resvport, max = xprt_max_resvport;
        unsigned short range;
        unsigned short rand;

        if (max < min)
                return -EADDRINUSE;
        range = max - min + 1;
        rand = (unsigned short) prandom_u32() % range;
        return rand + min;
}

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

        if (kernel_getsockname(sock, (struct sockaddr *)&buf) < 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->xprt.reuseport)
                transport->srcport = xs_sock_getport(sock);
}

static int xs_get_srcport(struct sock_xprt *transport)
{
        int 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;
        int 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 doesn'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 port;

        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)
{
        xprt_set_bound(task->tk_xprt);
}

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)
{
        if (WARN_ON_ONCE(!sock_allow_reclassification(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_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 file *filp;
        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)
                sock_set_reuseport(sock->sk);

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

        filp = sock_alloc_file(sock, O_NONBLOCK, NULL);
        if (IS_ERR(filp))
                return ERR_CAST(filp);
        transport->file = filp;

        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_data_ready;
                sk->sk_write_space = xs_udp_write_space;
                sock_set_flag(sk, SOCK_FASYNC);
                sk->sk_error_report = xs_error_report;

                xprt_clear_connected(xprt);

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

                write_unlock_bh(&sk->sk_callback_lock);
        }

        xs_stream_start_connect(transport);

        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 file *filp;
        struct socket *sock;
        int status;

        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_socket(AF_LOCAL, sock);

        filp = sock_alloc_file(sock, O_NONBLOCK, NULL);
        if (IS_ERR(filp)) {
                status = PTR_ERR(filp);
                goto out;
        }
        transport->file = filp;

        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->stat.connect_count++;
                xprt->stat.connect_time += (long)jiffies -
                                           xprt->stat.connect_start;
                xprt_set_connected(xprt);
                break;
        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.
                 */
                task->tk_rpc_status = -ENOTCONN;
                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_data_ready;
                sk->sk_write_space = xs_udp_write_space;
                sock_set_flag(sk, SOCK_FASYNC);

                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);

        xprt->stat.connect_start = jiffies;
}

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;
        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_clear_connecting(xprt);
        xprt_unlock_connect(xprt, transport);
        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;
        int skst = transport->inet ? transport->inet->sk_state : TCP_CLOSE;

        if (sock == NULL)
                return;
        switch (skst) {
        default:
                kernel_sock_shutdown(sock, SHUT_RDWR);
                trace_rpc_socket_shutdown(xprt, sock);
                break;
        case TCP_CLOSE:
        case TCP_TIME_WAIT:
                xs_reset_transport(transport);
        }
}

static void xs_tcp_set_socket_timeouts(struct rpc_xprt *xprt,
                struct socket *sock)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        unsigned int keepidle;
        unsigned int keepcnt;
        unsigned int timeo;

        spin_lock(&xprt->transport_lock);
        keepidle = DIV_ROUND_UP(xprt->timeout->to_initval, HZ);
        keepcnt = xprt->timeout->to_retries + 1;
        timeo = jiffies_to_msecs(xprt->timeout->to_initval) *
                (xprt->timeout->to_retries + 1);
        clear_bit(XPRT_SOCK_UPD_TIMEOUT, &transport->sock_state);
        spin_unlock(&xprt->transport_lock);

        /* TCP Keepalive options */
        sock_set_keepalive(sock->sk);
        tcp_sock_set_keepidle(sock->sk, keepidle);
        tcp_sock_set_keepintvl(sock->sk, keepidle);
        tcp_sock_set_keepcnt(sock->sk, keepcnt);

        /* TCP user timeout (see RFC5482) */
        tcp_sock_set_user_timeout(sock->sk, timeo);
}

static void xs_tcp_set_connect_timeout(struct rpc_xprt *xprt,
                unsigned long connect_timeout,
                unsigned long reconnect_timeout)
{
        struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
        struct rpc_timeout to;
        unsigned long initval;

        spin_lock(&xprt->transport_lock);
        if (reconnect_timeout < xprt->max_reconnect_timeout)
                xprt->max_reconnect_timeout = reconnect_timeout;
        if (connect_timeout < xprt->connect_timeout) {
                memcpy(&to, xprt->timeout, sizeof(to));
                initval = DIV_ROUND_UP(connect_timeout, to.to_retries + 1);
                /* Arbitrary lower limit */
                if (initval <  XS_TCP_INIT_REEST_TO << 1)
                        initval = XS_TCP_INIT_REEST_TO << 1;
                to.to_initval = initval;
                to.to_maxval = initval;
                memcpy(&transport->tcp_timeout, &to,
                                sizeof(transport->tcp_timeout));
                xprt->timeout = &transport->tcp_timeout;
                xprt->connect_timeout = connect_timeout;
        }
        set_bit(XPRT_SOCK_UPD_TIMEOUT, &transport->sock_state);
        spin_unlock(&xprt->transport_lock);
}

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;

                /* Avoid temporary address, they are bad for long-lived
                 * connections such as NFS mounts.
                 * RFC4941, section 3.6 suggests that:
                 *    Individual applications, which have specific
                 *    knowledge about the normal duration of connections,
                 *    MAY override this as appropriate.
                 */
                if (xs_addr(xprt)->sa_family == PF_INET6) {
                        ip6_sock_set_addr_preferences(sk,
                                IPV6_PREFER_SRC_PUBLIC);
                }

                xs_tcp_set_socket_timeouts(xprt, sock);
                tcp_sock_set_nodelay(sk);

                write_lock_bh(&sk->sk_callback_lock);

                xs_save_old_callbacks(transport, sk);

                sk->sk_user_data = xprt;
                sk->sk_data_ready = xs_data_ready;
                sk->sk_state_change = xs_tcp_state_change;
                sk->sk_write_space = xs_tcp_write_space;
                sock_set_flag(sk, SOCK_FASYNC);
                sk->sk_error_report = xs_error_report;

                /* socket options */
                sock_reset_flag(sk, SOCK_LINGER);

                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);

        xs_stream_start_connect(transport);

        /* Tell the socket layer to start connecting... */
        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);
                fallthrough;
        case -EINPROGRESS:
                /* SYN_SENT! */
                if (xprt->reestablish_timeout < XS_TCP_INIT_REEST_TO)
                        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
                break;
        case -EADDRNOTAVAIL:
                /* Source port number is unavailable. Try a new one! */
                transport->srcport = 0;
        }
out:
        return ret;
}

/**
 * xs_tcp_setup_socket - create a TCP socket and connect to a remote endpoint
 * @work: queued work item
 *
 * 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);
                fallthrough;
        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 -ENETDOWN:
        case -ENETUNREACH:
        case -EHOSTUNREACH:
        case -EADDRINUSE:
        case -ENOBUFS:
                /* xs_tcp_force_close() wakes tasks with a fixed error code.
                 * We need to wake them first to ensure the correct error code.
                 */
                xprt_wake_pending_tasks(xprt, status);
                xs_tcp_force_close(xprt);
                goto out;
        }
        status = -EAGAIN;
out:
        xprt_clear_connecting(xprt);
        xprt_unlock_connect(xprt, transport);
        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);
        unsigned long delay = 0;

        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);

                delay = xprt_reconnect_delay(xprt);
                xprt_reconnect_backoff(xprt, XS_TCP_INIT_REEST_TO);

        } else
                dprintk("RPC:       xs_connect scheduled xprt %p\n", xprt);

        queue_delayed_work(xprtiod_workqueue,
                        &transport->connect_worker,
                        delay);
}

static void xs_wake_disconnect(struct sock_xprt *transport)
{
        if (test_and_clear_bit(XPRT_SOCK_WAKE_DISCONNECT, &transport->sock_state))
                xs_tcp_force_close(&transport->xprt);
}

static void xs_wake_write(struct sock_xprt *transport)
{
        if (test_and_clear_bit(XPRT_SOCK_WAKE_WRITE, &transport->sock_state))
                xprt_write_space(&transport->xprt);
}

static void xs_wake_error(struct sock_xprt *transport)
{
        int sockerr;

        if (!test_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state))
                return;
        mutex_lock(&transport->recv_mutex);
        if (transport->sock == NULL)
                goto out;
        if (!test_and_clear_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state))
                goto out;
        sockerr = xchg(&transport->xprt_err, 0);
        if (sockerr < 0)
                xprt_wake_pending_tasks(&transport->xprt, sockerr);
out:
        mutex_unlock(&transport->recv_mutex);
}

static void xs_wake_pending(struct sock_xprt *transport)
{
        if (test_and_clear_bit(XPRT_SOCK_WAKE_PENDING, &transport->sock_state))
                xprt_wake_pending_tasks(&transport->xprt, -EAGAIN);
}

static void xs_error_handle(struct work_struct *work)
{
        struct sock_xprt *transport = container_of(work,
                        struct sock_xprt, error_worker);

        xs_wake_disconnect(transport);
        xs_wake_write(transport);
        xs_wake_error(transport);
        xs_wake_pending(transport);
}

/**
 * xs_local_print_stats - display AF_LOCAL socket-specific 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 / HZ,
                        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-specific 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-specific 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 / HZ,
                        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 int bc_malloc(struct rpc_task *task)
{
        struct rpc_rqst *rqst = task->tk_rqstp;
        size_t size = rqst->rq_callsize;
        struct page *page;
        struct rpc_buffer *buf;

        if (size > PAGE_SIZE - sizeof(struct rpc_buffer)) {
                WARN_ONCE(1, "xprtsock: large bc buffer request (size %zu)\n",
                          size);
                return -EINVAL;
        }

        page = alloc_page(GFP_KERNEL);
        if (!page)
                return -ENOMEM;

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

        rqst->rq_buffer = buf->data;
        rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize;
        return 0;
}

/*
 * Free the space allocated in the bc_alloc routine
 */
static void bc_free(struct rpc_task *task)
{
        void *buffer = task->tk_rqstp->rq_buffer;
        struct rpc_buffer *buf;

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

static int bc_sendto(struct rpc_rqst *req)
{
        struct xdr_buf *xdr = &req->rq_snd_buf;
        struct sock_xprt *transport =
                        container_of(req->rq_xprt, struct sock_xprt, xprt);
        struct msghdr msg = {
                .msg_flags      = 0,
        };
        rpc_fraghdr marker = cpu_to_be32(RPC_LAST_STREAM_FRAGMENT |
                                         (u32)xdr->len);
        unsigned int sent = 0;
        int err;

        req->rq_xtime = ktime_get();
        err = xprt_sock_sendmsg(transport->sock, &msg, xdr, 0, marker, &sent);
        xdr_free_bvec(xdr);
        if (err < 0 || sent != (xdr->len + sizeof(marker)))
                return -EAGAIN;
        return sent;
}

/**
 * bc_send_request - Send a backchannel Call on a TCP socket
 * @req: rpc_rqst containing Call message to be sent
 *
 * xpt_mutex ensures @rqstp's whole message is written to the socket
 * without interruption.
 *
 * Return values:
 *   %0 if the message was sent successfully
 *   %ENOTCONN if the message was not sent
 */
static int bc_send_request(struct rpc_rqst *req)
{
        struct svc_xprt *xprt;
        int len;

        /*
         * 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
         */
        mutex_lock(&xprt->xpt_mutex);
        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)
{
        xprt_disconnect_done(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 const struct rpc_xprt_ops xs_local_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xprt_release_xprt,
        .alloc_slot             = xprt_alloc_slot,
        .free_slot              = xprt_free_slot,
        .rpcbind                = xs_local_rpcbind,
        .set_port               = xs_local_set_port,
        .connect                = xs_local_connect,
        .buf_alloc              = rpc_malloc,
        .buf_free               = rpc_free,
        .prepare_request        = xs_stream_prepare_request,
        .send_request           = xs_local_send_request,
        .wait_for_reply_request = xprt_wait_for_reply_request_def,
        .close                  = xs_close,
        .destroy                = xs_destroy,
        .print_stats            = xs_local_print_stats,
        .enable_swap            = xs_enable_swap,
        .disable_swap           = xs_disable_swap,
};

static const 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,
        .free_slot              = xprt_free_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,
        .wait_for_reply_request = xprt_wait_for_reply_request_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 const struct rpc_xprt_ops xs_tcp_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xprt_release_xprt,
        .alloc_slot             = xprt_alloc_slot,
        .free_slot              = xprt_free_slot,
        .rpcbind                = rpcb_getport_async,
        .set_port               = xs_set_port,
        .connect                = xs_connect,
        .buf_alloc              = rpc_malloc,
        .buf_free               = rpc_free,
        .prepare_request        = xs_stream_prepare_request,
        .send_request           = xs_tcp_send_request,
        .wait_for_reply_request = xprt_wait_for_reply_request_def,
        .close                  = xs_tcp_shutdown,
        .destroy                = xs_destroy,
        .set_connect_timeout    = xs_tcp_set_connect_timeout,
        .print_stats            = xs_tcp_print_stats,
        .enable_swap            = xs_enable_swap,
        .disable_swap           = xs_disable_swap,
        .inject_disconnect      = xs_inject_disconnect,
#ifdef CONFIG_SUNRPC_BACKCHANNEL
        .bc_setup               = xprt_setup_bc,
        .bc_maxpayload          = xs_tcp_bc_maxpayload,
        .bc_num_slots           = xprt_bc_max_slots,
        .bc_free_rqst           = xprt_free_bc_rqst,
        .bc_destroy             = xprt_destroy_bc,
#endif
};

/*
 * The rpc_xprt_ops for the server backchannel
 */

static const struct rpc_xprt_ops bc_tcp_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xprt_release_xprt,
        .alloc_slot             = xprt_alloc_slot,
        .free_slot              = xprt_free_slot,
        .buf_alloc              = bc_malloc,
        .buf_free               = bc_free,
        .send_request           = bc_send_request,
        .wait_for_reply_request = xprt_wait_for_reply_request_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);
        mutex_init(&new->recv_mutex);
        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->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_WORK(&transport->recv_worker, xs_stream_data_receive_workfn);
        INIT_WORK(&transport->error_worker, xs_error_handle);
        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;
        /* 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;

        INIT_WORK(&transport->recv_worker, xs_udp_data_receive_workfn);
        INIT_WORK(&transport->error_worker, xs_error_handle);
        INIT_DELAYED_WORK(&transport->connect_worker, xs_udp_setup_socket);

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

                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);

                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->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;

        xprt->max_reconnect_timeout = xprt->timeout->to_maxval;
        xprt->connect_timeout = xprt->timeout->to_initval *
                (xprt->timeout->to_retries + 1);

        INIT_WORK(&transport->recv_worker, xs_stream_data_receive_workfn);
        INIT_WORK(&transport->error_worker, xs_error_handle);
        INIT_DELAYED_WORK(&transport->connect_worker, xs_tcp_setup_socket);

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

                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);

                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->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;
        args->bc_xprt->xpt_bc_xps = 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,
        .netid          = { "" },
};

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,
        .netid          = { "udp", "udp6", "" },
};

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,
        .netid          = { "tcp", "tcp6", "" },
};

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,
        .netid          = { "" },
};

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

        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 (sunrpc_table_header) {
                unregister_sysctl_table(sunrpc_table_header);
                sunrpc_table_header = NULL;
        }

        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)
                return ret;
        if (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);