Merge with /pub/scm/linux/kernel/git/torvalds/linux-2.6.git

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

/*
 * linux/net/sunrpc/xprtsock.c
 *
 * Client-side transport implementation for sockets.
 *
 * TCP callback races fixes (C) 1998 Red Hat Software <alan@redhat.com>
 * TCP send fixes (C) 1998 Red Hat Software <alan@redhat.com>
 * 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>
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/capability.h>
#include <linux/sched.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/udp.h>
#include <linux/tcp.h>
#include <linux/sunrpc/clnt.h>
#include <linux/file.h>

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

/*
 * How many times to try sending a request on a socket before waiting
 * for the socket buffer to clear.
 */
#define XS_SENDMSG_RETRY        (10U)

/*
 * Time out for an RPC UDP socket connect.  UDP socket connects are
 * synchronous, but we set a timeout anyway in case of resource
 * exhaustion on the local host.
 */
#define XS_UDP_CONN_TO          (5U * HZ)

/*
 * Wait duration for an RPC TCP connection to be established.  Solaris
 * NFS over TCP uses 60 seconds, for example, which is in line with how
 * long a server takes to reboot.
 */
#define XS_TCP_CONN_TO          (60U * HZ)

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

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

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

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

#ifdef RPC_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

#define XS_SENDMSG_FLAGS        (MSG_DONTWAIT | MSG_NOSIGNAL)

static inline int xs_send_head(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base, unsigned int len)
{
        struct kvec iov = {
                .iov_base       = xdr->head[0].iov_base + base,
                .iov_len        = len - base,
        };
        struct msghdr msg = {
                .msg_name       = addr,
                .msg_namelen    = addrlen,
                .msg_flags      = XS_SENDMSG_FLAGS,
        };

        if (xdr->len > len)
                msg.msg_flags |= MSG_MORE;

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

static int xs_send_tail(struct socket *sock, struct xdr_buf *xdr, unsigned int base, unsigned int len)
{
        struct kvec iov = {
                .iov_base       = xdr->tail[0].iov_base + base,
                .iov_len        = len - base,
        };
        struct msghdr msg = {
                .msg_flags      = XS_SENDMSG_FLAGS,
        };

        return kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len);
}

/**
 * xs_sendpages - write pages directly to a socket
 * @sock: socket to send on
 * @addr: UDP only -- address of destination
 * @addrlen: UDP only -- length of destination address
 * @xdr: buffer containing this request
 * @base: starting position in the buffer
 *
 */
static inline int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base)
{
        struct page **ppage = xdr->pages;
        unsigned int len, pglen = xdr->page_len;
        int err, ret = 0;
        ssize_t (*sendpage)(struct socket *, struct page *, int, size_t, int);

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

        clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags);

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

        if (unlikely(pglen == 0))
                goto copy_tail;
        if (unlikely(base >= pglen)) {
                base -= pglen;
                goto copy_tail;
        }
        if (base || xdr->page_base) {
                pglen -= base;
                base += xdr->page_base;
                ppage += base >> PAGE_CACHE_SHIFT;
                base &= ~PAGE_CACHE_MASK;
        }

        sendpage = sock->ops->sendpage ? : sock_no_sendpage;
        do {
                int flags = XS_SENDMSG_FLAGS;

                len = PAGE_CACHE_SIZE;
                if (base)
                        len -= base;
                if (pglen < len)
                        len = pglen;

                if (pglen != len || xdr->tail[0].iov_len != 0)
                        flags |= MSG_MORE;

                /* Hmm... We might be dealing with highmem pages */
                if (PageHighMem(*ppage))
                        sendpage = sock_no_sendpage;
                err = sendpage(sock, *ppage, base, len, flags);
                if (ret == 0)
                        ret = err;
                else if (err > 0)
                        ret += err;
                if (err != len)
                        goto out;
                base = 0;
                ppage++;
        } while ((pglen -= len) != 0);
copy_tail:
        len = xdr->tail[0].iov_len;
        if (base < len) {
                err = xs_send_tail(sock, xdr, base, len);
                if (ret == 0)
                        ret = err;
                else if (err > 0)
                        ret += err;
        }
out:
        return ret;
}

/**
 * xs_nospace - place task on wait queue if transmit was incomplete
 * @task: task to put to sleep
 *
 */
static void xs_nospace(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;

        dprintk("RPC: %4d xmit incomplete (%u left of %u)\n",
                        task->tk_pid, req->rq_slen - req->rq_bytes_sent,
                        req->rq_slen);

        if (test_bit(SOCK_ASYNC_NOSPACE, &xprt->sock->flags)) {
                /* Protect against races with write_space */
                spin_lock_bh(&xprt->transport_lock);

                /* Don't race with disconnect */
                if (!xprt_connected(xprt))
                        task->tk_status = -ENOTCONN;
                else if (test_bit(SOCK_NOSPACE, &xprt->sock->flags))
                        xprt_wait_for_buffer_space(task);

                spin_unlock_bh(&xprt->transport_lock);
        } else
                /* Keep holding the socket if it is blocked */
                rpc_delay(task, HZ>>4);
}

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

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

        req->rq_xtime = jiffies;
        status = xs_sendpages(xprt->sock, (struct sockaddr *) &xprt->addr,
                                sizeof(xprt->addr), xdr, req->rq_bytes_sent);

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

        if (likely(status >= (int) req->rq_slen))
                return 0;

        /* Still some bytes left; set up for a retry later. */
        if (status > 0)
                status = -EAGAIN;

        switch (status) {
        case -ENETUNREACH:
        case -EPIPE:
        case -ECONNREFUSED:
                /* When the server has died, an ICMP port unreachable message
                 * prompts ECONNREFUSED. */
                break;
        case -EAGAIN:
                xs_nospace(task);
                break;
        default:
                dprintk("RPC:      sendmsg returned unrecognized error %d\n",
                        -status);
                break;
        }

        return status;
}

static inline void xs_encode_tcp_record_marker(struct xdr_buf *buf)
{
        u32 reclen = buf->len - sizeof(rpc_fraghdr);
        rpc_fraghdr *base = buf->head[0].iov_base;
        *base = htonl(RPC_LAST_STREAM_FRAGMENT | reclen);
}

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

        xs_encode_tcp_record_marker(&req->rq_snd_buf);

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

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

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

                if (unlikely(status < 0))
                        break;

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

                status = -EAGAIN;
                if (retry++ > XS_SENDMSG_RETRY)
                        break;
        }

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

        return status;
}

/**
 * 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.
 */
static void xs_close(struct rpc_xprt *xprt)
{
        struct socket *sock = xprt->sock;
        struct sock *sk = xprt->inet;

        if (!sk)
                return;

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

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

        sk->sk_user_data = NULL;
        sk->sk_data_ready = xprt->old_data_ready;
        sk->sk_state_change = xprt->old_state_change;
        sk->sk_write_space = xprt->old_write_space;
        write_unlock_bh(&sk->sk_callback_lock);

        sk->sk_no_check = 0;

        sock_release(sock);
}

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

        cancel_delayed_work(&xprt->connect_worker);
        flush_scheduled_work();

        xprt_disconnect(xprt);
        xs_close(xprt);
        kfree(xprt->slot);
}

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

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

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

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

        if (xprt->shutdown)
                goto dropit;

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

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

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

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

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

        /* Something worked... */
        dst_confirm(skb->dst);

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

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

static inline size_t xs_tcp_copy_data(skb_reader_t *desc, void *p, size_t len)
{
        if (len > desc->count)
                len = desc->count;
        if (skb_copy_bits(desc->skb, desc->offset, p, len)) {
                dprintk("RPC:      failed to copy %zu bytes from skb. %zu bytes remain\n",
                                len, desc->count);
                return 0;
        }
        desc->offset += len;
        desc->count -= len;
        dprintk("RPC:      copied %zu bytes from skb. %zu bytes remain\n",
                        len, desc->count);
        return len;
}

static inline void xs_tcp_read_fraghdr(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        size_t len, used;
        char *p;

        p = ((char *) &xprt->tcp_recm) + xprt->tcp_offset;
        len = sizeof(xprt->tcp_recm) - xprt->tcp_offset;
        used = xs_tcp_copy_data(desc, p, len);
        xprt->tcp_offset += used;
        if (used != len)
                return;

        xprt->tcp_reclen = ntohl(xprt->tcp_recm);
        if (xprt->tcp_reclen & RPC_LAST_STREAM_FRAGMENT)
                xprt->tcp_flags |= XPRT_LAST_FRAG;
        else
                xprt->tcp_flags &= ~XPRT_LAST_FRAG;
        xprt->tcp_reclen &= RPC_FRAGMENT_SIZE_MASK;

        xprt->tcp_flags &= ~XPRT_COPY_RECM;
        xprt->tcp_offset = 0;

        /* Sanity check of the record length */
        if (unlikely(xprt->tcp_reclen < 4)) {
                dprintk("RPC:      invalid TCP record fragment length\n");
                xprt_disconnect(xprt);
                return;
        }
        dprintk("RPC:      reading TCP record fragment of length %d\n",
                        xprt->tcp_reclen);
}

static void xs_tcp_check_recm(struct rpc_xprt *xprt)
{
        dprintk("RPC:      xprt = %p, tcp_copied = %lu, tcp_offset = %u, tcp_reclen = %u, tcp_flags = %lx\n",
                        xprt, xprt->tcp_copied, xprt->tcp_offset, xprt->tcp_reclen, xprt->tcp_flags);
        if (xprt->tcp_offset == xprt->tcp_reclen) {
                xprt->tcp_flags |= XPRT_COPY_RECM;
                xprt->tcp_offset = 0;
                if (xprt->tcp_flags & XPRT_LAST_FRAG) {
                        xprt->tcp_flags &= ~XPRT_COPY_DATA;
                        xprt->tcp_flags |= XPRT_COPY_XID;
                        xprt->tcp_copied = 0;
                }
        }
}

static inline void xs_tcp_read_xid(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        size_t len, used;
        char *p;

        len = sizeof(xprt->tcp_xid) - xprt->tcp_offset;
        dprintk("RPC:      reading XID (%Zu bytes)\n", len);
        p = ((char *) &xprt->tcp_xid) + xprt->tcp_offset;
        used = xs_tcp_copy_data(desc, p, len);
        xprt->tcp_offset += used;
        if (used != len)
                return;
        xprt->tcp_flags &= ~XPRT_COPY_XID;
        xprt->tcp_flags |= XPRT_COPY_DATA;
        xprt->tcp_copied = 4;
        dprintk("RPC:      reading reply for XID %08x\n",
                                                ntohl(xprt->tcp_xid));
        xs_tcp_check_recm(xprt);
}

static inline void xs_tcp_read_request(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        struct rpc_rqst *req;
        struct xdr_buf *rcvbuf;
        size_t len;
        ssize_t r;

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

        rcvbuf = &req->rq_private_buf;
        len = desc->count;
        if (len > xprt->tcp_reclen - xprt->tcp_offset) {
                skb_reader_t my_desc;

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

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

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

        if (xprt->tcp_copied == req->rq_private_buf.buflen)
                xprt->tcp_flags &= ~XPRT_COPY_DATA;
        else if (xprt->tcp_offset == xprt->tcp_reclen) {
                if (xprt->tcp_flags & XPRT_LAST_FRAG)
                        xprt->tcp_flags &= ~XPRT_COPY_DATA;
        }

out:
        if (!(xprt->tcp_flags & XPRT_COPY_DATA))
                xprt_complete_rqst(req->rq_task, xprt->tcp_copied);
        spin_unlock(&xprt->transport_lock);
        xs_tcp_check_recm(xprt);
}

static inline void xs_tcp_read_discard(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        size_t len;

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

static int xs_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb, unsigned int offset, size_t len)
{
        struct rpc_xprt *xprt = rd_desc->arg.data;
        skb_reader_t desc = {
                .skb    = skb,
                .offset = offset,
                .count  = len,
                .csum   = 0
        };

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

/**
 * xs_tcp_data_ready - "data ready" callback for TCP sockets
 * @sk: socket with data to read
 * @bytes: how much data to read
 *
 */
static void xs_tcp_data_ready(struct sock *sk, int bytes)
{
        struct rpc_xprt *xprt;
        read_descriptor_t rd_desc;

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

        /* We use rd_desc to pass struct xprt to xs_tcp_data_recv */
        rd_desc.arg.data = xprt;
        rd_desc.count = 65536;
        tcp_read_sock(sk, &rd_desc, xs_tcp_data_recv);
out:
        read_unlock(&sk->sk_callback_lock);
}

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

        read_lock(&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\n",
                                sk->sk_state, xprt_connected(xprt),
                                sock_flag(sk, SOCK_DEAD),
                                sock_flag(sk, SOCK_ZAPPED));

        switch (sk->sk_state) {
        case TCP_ESTABLISHED:
                spin_lock_bh(&xprt->transport_lock);
                if (!xprt_test_and_set_connected(xprt)) {
                        /* Reset TCP record info */
                        xprt->tcp_offset = 0;
                        xprt->tcp_reclen = 0;
                        xprt->tcp_copied = 0;
                        xprt->tcp_flags = XPRT_COPY_RECM | XPRT_COPY_XID;
                        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
                        xprt_wake_pending_tasks(xprt, 0);
                }
                spin_unlock_bh(&xprt->transport_lock);
                break;
        case TCP_SYN_SENT:
        case TCP_SYN_RECV:
                break;
        default:
                xprt_disconnect(xprt);
                break;
        }
 out:
        read_unlock(&sk->sk_callback_lock);
}

/**
 * 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(&sk->sk_callback_lock);

        /* from net/core/sock.c:sock_def_write_space */
        if (sock_writeable(sk)) {
                struct socket *sock;
                struct rpc_xprt *xprt;

                if (unlikely(!(sock = sk->sk_socket)))
                        goto out;
                if (unlikely(!(xprt = xprt_from_sock(sk))))
                        goto out;
                if (unlikely(!test_and_clear_bit(SOCK_NOSPACE, &sock->flags)))
                        goto out;

                xprt_write_space(xprt);
        }

 out:
        read_unlock(&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(&sk->sk_callback_lock);

        /* from net/core/stream.c:sk_stream_write_space */
        if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) {
                struct socket *sock;
                struct rpc_xprt *xprt;

                if (unlikely(!(sock = sk->sk_socket)))
                        goto out;
                if (unlikely(!(xprt = xprt_from_sock(sk))))
                        goto out;
                if (unlikely(!test_and_clear_bit(SOCK_NOSPACE, &sock->flags)))
                        goto out;

                xprt_write_space(xprt);
        }

 out:
        read_unlock(&sk->sk_callback_lock);
}

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

        if (xprt->rcvsize) {
                sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
                sk->sk_rcvbuf = xprt->rcvsize * xprt->max_reqs *  2;
        }
        if (xprt->sndsize) {
                sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
                sk->sk_sndbuf = xprt->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)
{
        xprt->sndsize = 0;
        if (sndsize)
                xprt->sndsize = sndsize + 1024;
        xprt->rcvsize = 0;
        if (rcvsize)
                xprt->rcvsize = rcvsize + 1024;

        xs_udp_do_set_buffer_size(xprt);
}

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

static int xs_bindresvport(struct rpc_xprt *xprt, struct socket *sock)
{
        struct sockaddr_in myaddr = {
                .sin_family = AF_INET,
        };
        int err;
        unsigned short port = xprt->port;

        do {
                myaddr.sin_port = htons(port);
                err = sock->ops->bind(sock, (struct sockaddr *) &myaddr,
                                                sizeof(myaddr));
                if (err == 0) {
                        xprt->port = port;
                        dprintk("RPC:      xs_bindresvport bound to port %u\n",
                                        port);
                        return 0;
                }
                if (port <= xprt_min_resvport)
                        port = xprt_max_resvport;
                else
                        port--;
        } while (err == -EADDRINUSE && port != xprt->port);

        dprintk("RPC:      can't bind to reserved port (%d).\n", -err);
        return err;
}

/**
 * xs_udp_connect_worker - set up a UDP socket
 * @args: RPC transport to connect
 *
 * Invoked by a work queue tasklet.
 */
static void xs_udp_connect_worker(void *args)
{
        struct rpc_xprt *xprt = (struct rpc_xprt *) args;
        struct socket *sock = xprt->sock;
        int err, status = -EIO;

        if (xprt->shutdown || xprt->addr.sin_port == 0)
                goto out;

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

        /* Start by resetting any existing state */
        xs_close(xprt);

        if ((err = sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock)) < 0) {
                dprintk("RPC:      can't create UDP transport socket (%d).\n", -err);
                goto out;
        }

        if (xprt->resvport && xs_bindresvport(xprt, sock) < 0) {
                sock_release(sock);
                goto out;
        }

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

                write_lock_bh(&sk->sk_callback_lock);

                sk->sk_user_data = xprt;
                xprt->old_data_ready = sk->sk_data_ready;
                xprt->old_state_change = sk->sk_state_change;
                xprt->old_write_space = sk->sk_write_space;
                sk->sk_data_ready = xs_udp_data_ready;
                sk->sk_write_space = xs_udp_write_space;
                sk->sk_no_check = UDP_CSUM_NORCV;

                xprt_set_connected(xprt);

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

                write_unlock_bh(&sk->sk_callback_lock);
        }
        xs_udp_do_set_buffer_size(xprt);
        status = 0;
out:
        xprt_wake_pending_tasks(xprt, status);
        xprt_clear_connecting(xprt);
}

/*
 * We need to preserve the port number so the reply cache on the server can
 * find our cached RPC replies when we get around to reconnecting.
 */
static void xs_tcp_reuse_connection(struct rpc_xprt *xprt)
{
        int result;
        struct socket *sock = xprt->sock;
        struct sockaddr any;

        dprintk("RPC:      disconnecting xprt %p to reuse port\n", xprt);

        /*
         * Disconnect the transport socket by doing a connect operation
         * with AF_UNSPEC.  This should return immediately...
         */
        memset(&any, 0, sizeof(any));
        any.sa_family = AF_UNSPEC;
        result = sock->ops->connect(sock, &any, sizeof(any), 0);
        if (result)
                dprintk("RPC:      AF_UNSPEC connect return code %d\n",
                                result);
}

/**
 * xs_tcp_connect_worker - connect a TCP socket to a remote endpoint
 * @args: RPC transport to connect
 *
 * Invoked by a work queue tasklet.
 */
static void xs_tcp_connect_worker(void *args)
{
        struct rpc_xprt *xprt = (struct rpc_xprt *)args;
        struct socket *sock = xprt->sock;
        int err, status = -EIO;

        if (xprt->shutdown || xprt->addr.sin_port == 0)
                goto out;

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

        if (!xprt->sock) {
                /* start from scratch */
                if ((err = sock_create_kern(PF_INET, SOCK_STREAM, IPPROTO_TCP, &sock)) < 0) {
                        dprintk("RPC:      can't create TCP transport socket (%d).\n", -err);
                        goto out;
                }

                if (xprt->resvport && xs_bindresvport(xprt, sock) < 0) {
                        sock_release(sock);
                        goto out;
                }
        } else
                /* "close" the socket, preserving the local port */
                xs_tcp_reuse_connection(xprt);

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

                write_lock_bh(&sk->sk_callback_lock);

                sk->sk_user_data = xprt;
                xprt->old_data_ready = sk->sk_data_ready;
                xprt->old_state_change = sk->sk_state_change;
                xprt->old_write_space = sk->sk_write_space;
                sk->sk_data_ready = xs_tcp_data_ready;
                sk->sk_state_change = xs_tcp_state_change;
                sk->sk_write_space = xs_tcp_write_space;

                /* socket options */
                sk->sk_userlocks |= SOCK_BINDPORT_LOCK;
                sock_reset_flag(sk, SOCK_LINGER);
                tcp_sk(sk)->linger2 = 0;
                tcp_sk(sk)->nonagle |= TCP_NAGLE_OFF;

                xprt_clear_connected(xprt);

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

                write_unlock_bh(&sk->sk_callback_lock);
        }

        /* Tell the socket layer to start connecting... */
        status = sock->ops->connect(sock, (struct sockaddr *) &xprt->addr,
                        sizeof(xprt->addr), O_NONBLOCK);
        dprintk("RPC: %p  connect status %d connected %d sock state %d\n",
                        xprt, -status, xprt_connected(xprt), sock->sk->sk_state);
        if (status < 0) {
                switch (status) {
                        case -EINPROGRESS:
                        case -EALREADY:
                                goto out_clear;
                        case -ECONNREFUSED:
                        case -ECONNRESET:
                                /* retry with existing socket, after a delay */
                                break;
                        default:
                                /* get rid of existing socket, and retry */
                                xs_close(xprt);
                                break;
                }
        }
out:
        xprt_wake_pending_tasks(xprt, status);
out_clear:
        xprt_clear_connecting(xprt);
}

/**
 * xs_connect - connect a socket to a remote endpoint
 * @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_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        if (xprt_test_and_set_connecting(xprt))
                return;

        if (xprt->sock != NULL) {
                dprintk("RPC:      xs_connect delayed xprt %p for %lu seconds\n",
                                xprt, xprt->reestablish_timeout / HZ);
                schedule_delayed_work(&xprt->connect_worker,
                                        xprt->reestablish_timeout);
                xprt->reestablish_timeout <<= 1;
                if (xprt->reestablish_timeout > XS_TCP_MAX_REEST_TO)
                        xprt->reestablish_timeout = XS_TCP_MAX_REEST_TO;
        } else {
                dprintk("RPC:      xs_connect scheduled xprt %p\n", xprt);
                schedule_work(&xprt->connect_worker);

                /* flush_scheduled_work can sleep... */
                if (!RPC_IS_ASYNC(task))
                        flush_scheduled_work();
        }
}

static struct rpc_xprt_ops xs_udp_ops = {
        .set_buffer_size        = xs_udp_set_buffer_size,
        .reserve_xprt           = xprt_reserve_xprt_cong,
        .release_xprt           = xprt_release_xprt_cong,
        .connect                = xs_connect,
        .send_request           = xs_udp_send_request,
        .set_retrans_timeout    = xprt_set_retrans_timeout_rtt,
        .timer                  = xs_udp_timer,
        .release_request        = xprt_release_rqst_cong,
        .close                  = xs_close,
        .destroy                = xs_destroy,
};

static struct rpc_xprt_ops xs_tcp_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xprt_release_xprt,
        .connect                = xs_connect,
        .send_request           = xs_tcp_send_request,
        .set_retrans_timeout    = xprt_set_retrans_timeout_def,
        .close                  = xs_close,
        .destroy                = xs_destroy,
};

/**
 * xs_setup_udp - Set up transport to use a UDP socket
 * @xprt: transport to set up
 * @to:   timeout parameters
 *
 */
int xs_setup_udp(struct rpc_xprt *xprt, struct rpc_timeout *to)
{
        size_t slot_table_size;

        dprintk("RPC:      setting up udp-ipv4 transport...\n");

        xprt->max_reqs = xprt_udp_slot_table_entries;
        slot_table_size = xprt->max_reqs * sizeof(xprt->slot[0]);
        xprt->slot = kmalloc(slot_table_size, GFP_KERNEL);
        if (xprt->slot == NULL)
                return -ENOMEM;
        memset(xprt->slot, 0, slot_table_size);

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

        INIT_WORK(&xprt->connect_worker, xs_udp_connect_worker, xprt);
        xprt->bind_timeout = XS_BIND_TO;
        xprt->connect_timeout = XS_UDP_CONN_TO;
        xprt->reestablish_timeout = XS_UDP_REEST_TO;
        xprt->idle_timeout = XS_IDLE_DISC_TO;

        xprt->ops = &xs_udp_ops;

        if (to)
                xprt->timeout = *to;
        else
                xprt_set_timeout(&xprt->timeout, 5, 5 * HZ);

        return 0;
}

/**
 * xs_setup_tcp - Set up transport to use a TCP socket
 * @xprt: transport to set up
 * @to: timeout parameters
 *
 */
int xs_setup_tcp(struct rpc_xprt *xprt, struct rpc_timeout *to)
{
        size_t slot_table_size;

        dprintk("RPC:      setting up tcp-ipv4 transport...\n");

        xprt->max_reqs = xprt_tcp_slot_table_entries;
        slot_table_size = xprt->max_reqs * sizeof(xprt->slot[0]);
        xprt->slot = kmalloc(slot_table_size, GFP_KERNEL);
        if (xprt->slot == NULL)
                return -ENOMEM;
        memset(xprt->slot, 0, slot_table_size);

        xprt->prot = IPPROTO_TCP;
        xprt->port = xprt_max_resvport;
        xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
        xprt->resvport = capable(CAP_NET_BIND_SERVICE) ? 1 : 0;
        xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;

        INIT_WORK(&xprt->connect_worker, xs_tcp_connect_worker, xprt);
        xprt->bind_timeout = XS_BIND_TO;
        xprt->connect_timeout = XS_TCP_CONN_TO;
        xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
        xprt->idle_timeout = XS_IDLE_DISC_TO;

        xprt->ops = &xs_tcp_ops;

        if (to)
                xprt->timeout = *to;
        else
                xprt_set_timeout(&xprt->timeout, 2, 60 * HZ);

        return 0;
}