// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/net/sunrpc/svcsock.c
 *
 * These are the RPC server socket internals.
 *
 * The server scheduling algorithm does not always distribute the load
 * evenly when servicing a single client. May need to modify the
 * svc_xprt_enqueue procedure...
 *
 * TCP support is largely untested and may be a little slow. The problem
 * is that we currently do two separate recvfrom's, one for the 4-byte
 * record length, and the second for the actual record. This could possibly
 * be improved by always reading a minimum size of around 100 bytes and
 * tucking any superfluous bytes away in a temporary store. Still, that
 * leaves write requests out in the rain. An alternative may be to peek at
 * the first skb in the queue, and if it matches the next TCP sequence
 * number, to extract the record marker. Yuck.
 *
 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/net.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/unistd.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/file.h>
#include <linux/freezer.h>
#include <net/sock.h>
#include <net/checksum.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <net/tcp_states.h>
#include <linux/uaccess.h>
#include <asm/ioctls.h>
#include <trace/events/skb.h>

#include <linux/sunrpc/types.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/xdr.h>
#include <linux/sunrpc/msg_prot.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/xprt.h>

#include "sunrpc.h"

#define RPCDBG_FACILITY RPCDBG_SVCXPRT


static struct svc_sock *svc_setup_socket(struct svc_serv *, struct socket *,
                                         int flags);
static int              svc_udp_recvfrom(struct svc_rqst *);
static int              svc_udp_sendto(struct svc_rqst *);
static void             svc_sock_detach(struct svc_xprt *);
static void             svc_tcp_sock_detach(struct svc_xprt *);
static void             svc_sock_free(struct svc_xprt *);

static struct svc_xprt *svc_create_socket(struct svc_serv *, int,
                                          struct net *, struct sockaddr *,
                                          int, int);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key svc_key[2];
static struct lock_class_key svc_slock_key[2];

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

        if (WARN_ON_ONCE(!sock_allow_reclassification(sk)))
                return;

        switch (sk->sk_family) {
        case AF_INET:
                sock_lock_init_class_and_name(sk, "slock-AF_INET-NFSD",
                                              &svc_slock_key[0],
                                              "sk_xprt.xpt_lock-AF_INET-NFSD",
                                              &svc_key[0]);
                break;

        case AF_INET6:
                sock_lock_init_class_and_name(sk, "slock-AF_INET6-NFSD",
                                              &svc_slock_key[1],
                                              "sk_xprt.xpt_lock-AF_INET6-NFSD",
                                              &svc_key[1]);
                break;

        default:
                BUG();
        }
}
#else
static void svc_reclassify_socket(struct socket *sock)
{
}
#endif

/*
 * Release an skbuff after use
 */
static void svc_release_skb(struct svc_rqst *rqstp)
{
        struct sk_buff *skb = rqstp->rq_xprt_ctxt;

        if (skb) {
                struct svc_sock *svsk =
                        container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
                rqstp->rq_xprt_ctxt = NULL;

                dprintk("svc: service %p, releasing skb %p\n", rqstp, skb);
                skb_free_datagram_locked(svsk->sk_sk, skb);
        }
}

static void svc_release_udp_skb(struct svc_rqst *rqstp)
{
        struct sk_buff *skb = rqstp->rq_xprt_ctxt;

        if (skb) {
                rqstp->rq_xprt_ctxt = NULL;

                dprintk("svc: service %p, releasing skb %p\n", rqstp, skb);
                consume_skb(skb);
        }
}

union svc_pktinfo_u {
        struct in_pktinfo pkti;
        struct in6_pktinfo pkti6;
};
#define SVC_PKTINFO_SPACE \
        CMSG_SPACE(sizeof(union svc_pktinfo_u))

static void svc_set_cmsg_data(struct svc_rqst *rqstp, struct cmsghdr *cmh)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        switch (svsk->sk_sk->sk_family) {
        case AF_INET: {
                        struct in_pktinfo *pki = CMSG_DATA(cmh);

                        cmh->cmsg_level = SOL_IP;
                        cmh->cmsg_type = IP_PKTINFO;
                        pki->ipi_ifindex = 0;
                        pki->ipi_spec_dst.s_addr =
                                 svc_daddr_in(rqstp)->sin_addr.s_addr;
                        cmh->cmsg_len = CMSG_LEN(sizeof(*pki));
                }
                break;

        case AF_INET6: {
                        struct in6_pktinfo *pki = CMSG_DATA(cmh);
                        struct sockaddr_in6 *daddr = svc_daddr_in6(rqstp);

                        cmh->cmsg_level = SOL_IPV6;
                        cmh->cmsg_type = IPV6_PKTINFO;
                        pki->ipi6_ifindex = daddr->sin6_scope_id;
                        pki->ipi6_addr = daddr->sin6_addr;
                        cmh->cmsg_len = CMSG_LEN(sizeof(*pki));
                }
                break;
        }
}

/*
 * send routine intended to be shared by the fore- and back-channel
 */
int svc_send_common(struct socket *sock, struct xdr_buf *xdr,
                    struct page *headpage, unsigned long headoffset,
                    struct page *tailpage, unsigned long tailoffset)
{
        int             result;
        int             size;
        struct page     **ppage = xdr->pages;
        size_t          base = xdr->page_base;
        unsigned int    pglen = xdr->page_len;
        unsigned int    flags = MSG_MORE | MSG_SENDPAGE_NOTLAST;
        int             slen;
        int             len = 0;

        slen = xdr->len;

        /* send head */
        if (slen == xdr->head[0].iov_len)
                flags = 0;
        len = kernel_sendpage(sock, headpage, headoffset,
                                  xdr->head[0].iov_len, flags);
        if (len != xdr->head[0].iov_len)
                goto out;
        slen -= xdr->head[0].iov_len;
        if (slen == 0)
                goto out;

        /* send page data */
        size = PAGE_SIZE - base < pglen ? PAGE_SIZE - base : pglen;
        while (pglen > 0) {
                if (slen == size)
                        flags = 0;
                result = kernel_sendpage(sock, *ppage, base, size, flags);
                if (result > 0)
                        len += result;
                if (result != size)
                        goto out;
                slen -= size;
                pglen -= size;
                size = PAGE_SIZE < pglen ? PAGE_SIZE : pglen;
                base = 0;
                ppage++;
        }

        /* send tail */
        if (xdr->tail[0].iov_len) {
                result = kernel_sendpage(sock, tailpage, tailoffset,
                                   xdr->tail[0].iov_len, 0);
                if (result > 0)
                        len += result;
        }

out:
        return len;
}


/*
 * Generic sendto routine
 */
static int svc_sendto(struct svc_rqst *rqstp, struct xdr_buf *xdr)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        struct socket   *sock = svsk->sk_sock;
        union {
                struct cmsghdr  hdr;
                long            all[SVC_PKTINFO_SPACE / sizeof(long)];
        } buffer;
        struct cmsghdr *cmh = &buffer.hdr;
        int             len = 0;
        unsigned long tailoff;
        unsigned long headoff;
        RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);

        if (rqstp->rq_prot == IPPROTO_UDP) {
                struct msghdr msg = {
                        .msg_name       = &rqstp->rq_addr,
                        .msg_namelen    = rqstp->rq_addrlen,
                        .msg_control    = cmh,
                        .msg_controllen = sizeof(buffer),
                        .msg_flags      = MSG_MORE,
                };

                svc_set_cmsg_data(rqstp, cmh);

                if (sock_sendmsg(sock, &msg) < 0)
                        goto out;
        }

        tailoff = ((unsigned long)xdr->tail[0].iov_base) & (PAGE_SIZE-1);
        headoff = 0;
        len = svc_send_common(sock, xdr, rqstp->rq_respages[0], headoff,
                               rqstp->rq_respages[0], tailoff);

out:
        dprintk("svc: socket %p sendto([%p %zu... ], %d) = %d (addr %s)\n",
                svsk, xdr->head[0].iov_base, xdr->head[0].iov_len,
                xdr->len, len, svc_print_addr(rqstp, buf, sizeof(buf)));

        return len;
}

/*
 * Report socket names for nfsdfs
 */
static int svc_one_sock_name(struct svc_sock *svsk, char *buf, int remaining)
{
        const struct sock *sk = svsk->sk_sk;
        const char *proto_name = sk->sk_protocol == IPPROTO_UDP ?
                                                        "udp" : "tcp";
        int len;

        switch (sk->sk_family) {
        case PF_INET:
                len = snprintf(buf, remaining, "ipv4 %s %pI4 %d\n",
                                proto_name,
                                &inet_sk(sk)->inet_rcv_saddr,
                                inet_sk(sk)->inet_num);
                break;
#if IS_ENABLED(CONFIG_IPV6)
        case PF_INET6:
                len = snprintf(buf, remaining, "ipv6 %s %pI6 %d\n",
                                proto_name,
                                &sk->sk_v6_rcv_saddr,
                                inet_sk(sk)->inet_num);
                break;
#endif
        default:
                len = snprintf(buf, remaining, "*unknown-%d*\n",
                                sk->sk_family);
        }

        if (len >= remaining) {
                *buf = '\0';
                return -ENAMETOOLONG;
        }
        return len;
}

/*
 * Generic recvfrom routine.
 */
static ssize_t svc_recvfrom(struct svc_rqst *rqstp, struct kvec *iov,
                            unsigned int nr, size_t buflen, unsigned int base)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        struct msghdr msg = { NULL };
        ssize_t len;

        rqstp->rq_xprt_hlen = 0;

        clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
        iov_iter_kvec(&msg.msg_iter, READ, iov, nr, buflen);
        if (base != 0) {
                iov_iter_advance(&msg.msg_iter, base);
                buflen -= base;
        }
        len = sock_recvmsg(svsk->sk_sock, &msg, MSG_DONTWAIT);
        /* If we read a full record, then assume there may be more
         * data to read (stream based sockets only!)
         */
        if (len == buflen)
                set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);

        dprintk("svc: socket %p recvfrom(%p, %zu) = %zd\n",
                svsk, iov[0].iov_base, iov[0].iov_len, len);
        return len;
}

/*
 * Set socket snd and rcv buffer lengths
 */
static void svc_sock_setbufsize(struct svc_sock *svsk, unsigned int nreqs)
{
        unsigned int max_mesg = svsk->sk_xprt.xpt_server->sv_max_mesg;
        struct socket *sock = svsk->sk_sock;

        nreqs = min(nreqs, INT_MAX / 2 / max_mesg);

        lock_sock(sock->sk);
        sock->sk->sk_sndbuf = nreqs * max_mesg * 2;
        sock->sk->sk_rcvbuf = nreqs * max_mesg * 2;
        sock->sk->sk_write_space(sock->sk);
        release_sock(sock->sk);
}

static void svc_sock_secure_port(struct svc_rqst *rqstp)
{
        if (svc_port_is_privileged(svc_addr(rqstp)))
                set_bit(RQ_SECURE, &rqstp->rq_flags);
        else
                clear_bit(RQ_SECURE, &rqstp->rq_flags);
}

/*
 * INET callback when data has been received on the socket.
 */
static void svc_data_ready(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        if (svsk) {
                dprintk("svc: socket %p(inet %p), busy=%d\n",
                        svsk, sk,
                        test_bit(XPT_BUSY, &svsk->sk_xprt.xpt_flags));

                /* Refer to svc_setup_socket() for details. */
                rmb();
                svsk->sk_odata(sk);
                if (!test_and_set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags))
                        svc_xprt_enqueue(&svsk->sk_xprt);
        }
}

/*
 * INET callback when space is newly available on the socket.
 */
static void svc_write_space(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)(sk->sk_user_data);

        if (svsk) {
                dprintk("svc: socket %p(inet %p), write_space busy=%d\n",
                        svsk, sk, test_bit(XPT_BUSY, &svsk->sk_xprt.xpt_flags));

                /* Refer to svc_setup_socket() for details. */
                rmb();
                svsk->sk_owspace(sk);
                svc_xprt_enqueue(&svsk->sk_xprt);
        }
}

static int svc_tcp_has_wspace(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);

        if (test_bit(XPT_LISTENER, &xprt->xpt_flags))
                return 1;
        return !test_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
}

static void svc_tcp_kill_temp_xprt(struct svc_xprt *xprt)
{
        struct svc_sock *svsk;
        struct socket *sock;
        struct linger no_linger = {
                .l_onoff = 1,
                .l_linger = 0,
        };

        svsk = container_of(xprt, struct svc_sock, sk_xprt);
        sock = svsk->sk_sock;
        kernel_setsockopt(sock, SOL_SOCKET, SO_LINGER,
                          (char *)&no_linger, sizeof(no_linger));
}

/*
 * See net/ipv6/ip_sockglue.c : ip_cmsg_recv_pktinfo
 */
static int svc_udp_get_dest_address4(struct svc_rqst *rqstp,
                                     struct cmsghdr *cmh)
{
        struct in_pktinfo *pki = CMSG_DATA(cmh);
        struct sockaddr_in *daddr = svc_daddr_in(rqstp);

        if (cmh->cmsg_type != IP_PKTINFO)
                return 0;

        daddr->sin_family = AF_INET;
        daddr->sin_addr.s_addr = pki->ipi_spec_dst.s_addr;
        return 1;
}

/*
 * See net/ipv6/datagram.c : ip6_datagram_recv_ctl
 */
static int svc_udp_get_dest_address6(struct svc_rqst *rqstp,
                                     struct cmsghdr *cmh)
{
        struct in6_pktinfo *pki = CMSG_DATA(cmh);
        struct sockaddr_in6 *daddr = svc_daddr_in6(rqstp);

        if (cmh->cmsg_type != IPV6_PKTINFO)
                return 0;

        daddr->sin6_family = AF_INET6;
        daddr->sin6_addr = pki->ipi6_addr;
        daddr->sin6_scope_id = pki->ipi6_ifindex;
        return 1;
}

/*
 * Copy the UDP datagram's destination address to the rqstp structure.
 * The 'destination' address in this case is the address to which the
 * peer sent the datagram, i.e. our local address. For multihomed
 * hosts, this can change from msg to msg. Note that only the IP
 * address changes, the port number should remain the same.
 */
static int svc_udp_get_dest_address(struct svc_rqst *rqstp,
                                    struct cmsghdr *cmh)
{
        switch (cmh->cmsg_level) {
        case SOL_IP:
                return svc_udp_get_dest_address4(rqstp, cmh);
        case SOL_IPV6:
                return svc_udp_get_dest_address6(rqstp, cmh);
        }

        return 0;
}

/*
 * Receive a datagram from a UDP socket.
 */
static int svc_udp_recvfrom(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
        struct sk_buff  *skb;
        union {
                struct cmsghdr  hdr;
                long            all[SVC_PKTINFO_SPACE / sizeof(long)];
        } buffer;
        struct cmsghdr *cmh = &buffer.hdr;
        struct msghdr msg = {
                .msg_name = svc_addr(rqstp),
                .msg_control = cmh,
                .msg_controllen = sizeof(buffer),
                .msg_flags = MSG_DONTWAIT,
        };
        size_t len;
        int err;

        if (test_and_clear_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags))
            /* udp sockets need large rcvbuf as all pending
             * requests are still in that buffer.  sndbuf must
             * also be large enough that there is enough space
             * for one reply per thread.  We count all threads
             * rather than threads in a particular pool, which
             * provides an upper bound on the number of threads
             * which will access the socket.
             */
            svc_sock_setbufsize(svsk, serv->sv_nrthreads + 3);

        clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
        skb = NULL;
        err = kernel_recvmsg(svsk->sk_sock, &msg, NULL,
                             0, 0, MSG_PEEK | MSG_DONTWAIT);
        if (err >= 0)
                skb = skb_recv_udp(svsk->sk_sk, 0, 1, &err);

        if (skb == NULL) {
                if (err != -EAGAIN) {
                        /* possibly an icmp error */
                        dprintk("svc: recvfrom returned error %d\n", -err);
                        set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
                }
                return 0;
        }
        len = svc_addr_len(svc_addr(rqstp));
        rqstp->rq_addrlen = len;
        if (skb->tstamp == 0) {
                skb->tstamp = ktime_get_real();
                /* Don't enable netstamp, sunrpc doesn't
                   need that much accuracy */
        }
        sock_write_timestamp(svsk->sk_sk, skb->tstamp);
        set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags); /* there may be more data... */

        len  = skb->len;
        rqstp->rq_arg.len = len;

        rqstp->rq_prot = IPPROTO_UDP;

        if (!svc_udp_get_dest_address(rqstp, cmh)) {
                net_warn_ratelimited("svc: received unknown control message %d/%d; dropping RPC reply datagram\n",
                                     cmh->cmsg_level, cmh->cmsg_type);
                goto out_free;
        }
        rqstp->rq_daddrlen = svc_addr_len(svc_daddr(rqstp));

        if (skb_is_nonlinear(skb)) {
                /* we have to copy */
                local_bh_disable();
                if (csum_partial_copy_to_xdr(&rqstp->rq_arg, skb)) {
                        local_bh_enable();
                        /* checksum error */
                        goto out_free;
                }
                local_bh_enable();
                consume_skb(skb);
        } else {
                /* we can use it in-place */
                rqstp->rq_arg.head[0].iov_base = skb->data;
                rqstp->rq_arg.head[0].iov_len = len;
                if (skb_checksum_complete(skb))
                        goto out_free;
                rqstp->rq_xprt_ctxt = skb;
        }

        rqstp->rq_arg.page_base = 0;
        if (len <= rqstp->rq_arg.head[0].iov_len) {
                rqstp->rq_arg.head[0].iov_len = len;
                rqstp->rq_arg.page_len = 0;
                rqstp->rq_respages = rqstp->rq_pages+1;
        } else {
                rqstp->rq_arg.page_len = len - rqstp->rq_arg.head[0].iov_len;
                rqstp->rq_respages = rqstp->rq_pages + 1 +
                        DIV_ROUND_UP(rqstp->rq_arg.page_len, PAGE_SIZE);
        }
        rqstp->rq_next_page = rqstp->rq_respages+1;

        if (serv->sv_stats)
                serv->sv_stats->netudpcnt++;

        return len;
out_free:
        kfree_skb(skb);
        return 0;
}

static int
svc_udp_sendto(struct svc_rqst *rqstp)
{
        int             error;

        error = svc_sendto(rqstp, &rqstp->rq_res);
        if (error == -ECONNREFUSED)
                /* ICMP error on earlier request. */
                error = svc_sendto(rqstp, &rqstp->rq_res);

        return error;
}

static int svc_udp_has_wspace(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct svc_serv *serv = xprt->xpt_server;
        unsigned long required;

        /*
         * Set the SOCK_NOSPACE flag before checking the available
         * sock space.
         */
        set_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
        required = atomic_read(&svsk->sk_xprt.xpt_reserved) + serv->sv_max_mesg;
        if (required*2 > sock_wspace(svsk->sk_sk))
                return 0;
        clear_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
        return 1;
}

static struct svc_xprt *svc_udp_accept(struct svc_xprt *xprt)
{
        BUG();
        return NULL;
}

static void svc_udp_kill_temp_xprt(struct svc_xprt *xprt)
{
}

static struct svc_xprt *svc_udp_create(struct svc_serv *serv,
                                       struct net *net,
                                       struct sockaddr *sa, int salen,
                                       int flags)
{
        return svc_create_socket(serv, IPPROTO_UDP, net, sa, salen, flags);
}

static const struct svc_xprt_ops svc_udp_ops = {
        .xpo_create = svc_udp_create,
        .xpo_recvfrom = svc_udp_recvfrom,
        .xpo_sendto = svc_udp_sendto,
        .xpo_release_rqst = svc_release_udp_skb,
        .xpo_detach = svc_sock_detach,
        .xpo_free = svc_sock_free,
        .xpo_has_wspace = svc_udp_has_wspace,
        .xpo_accept = svc_udp_accept,
        .xpo_secure_port = svc_sock_secure_port,
        .xpo_kill_temp_xprt = svc_udp_kill_temp_xprt,
};

static struct svc_xprt_class svc_udp_class = {
        .xcl_name = "udp",
        .xcl_owner = THIS_MODULE,
        .xcl_ops = &svc_udp_ops,
        .xcl_max_payload = RPCSVC_MAXPAYLOAD_UDP,
        .xcl_ident = XPRT_TRANSPORT_UDP,
};

static void svc_udp_init(struct svc_sock *svsk, struct svc_serv *serv)
{
        int err, level, optname, one = 1;

        svc_xprt_init(sock_net(svsk->sk_sock->sk), &svc_udp_class,
                      &svsk->sk_xprt, serv);
        clear_bit(XPT_CACHE_AUTH, &svsk->sk_xprt.xpt_flags);
        svsk->sk_sk->sk_data_ready = svc_data_ready;
        svsk->sk_sk->sk_write_space = svc_write_space;

        /* initialise setting must have enough space to
         * receive and respond to one request.
         * svc_udp_recvfrom will re-adjust if necessary
         */
        svc_sock_setbufsize(svsk, 3);

        /* data might have come in before data_ready set up */
        set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
        set_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags);

        /* make sure we get destination address info */
        switch (svsk->sk_sk->sk_family) {
        case AF_INET:
                level = SOL_IP;
                optname = IP_PKTINFO;
                break;
        case AF_INET6:
                level = SOL_IPV6;
                optname = IPV6_RECVPKTINFO;
                break;
        default:
                BUG();
        }
        err = kernel_setsockopt(svsk->sk_sock, level, optname,
                                        (char *)&one, sizeof(one));
        dprintk("svc: kernel_setsockopt returned %d\n", err);
}

/*
 * A data_ready event on a listening socket means there's a connection
 * pending. Do not use state_change as a substitute for it.
 */
static void svc_tcp_listen_data_ready(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        dprintk("svc: socket %p TCP (listen) state change %d\n",
                sk, sk->sk_state);

        if (svsk) {
                /* Refer to svc_setup_socket() for details. */
                rmb();
                svsk->sk_odata(sk);
        }

        /*
         * This callback may called twice when a new connection
         * is established as a child socket inherits everything
         * from a parent LISTEN socket.
         * 1) data_ready method of the parent socket will be called
         *    when one of child sockets become ESTABLISHED.
         * 2) data_ready method of the child socket may be called
         *    when it receives data before the socket is accepted.
         * In case of 2, we should ignore it silently.
         */
        if (sk->sk_state == TCP_LISTEN) {
                if (svsk) {
                        set_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);
                        svc_xprt_enqueue(&svsk->sk_xprt);
                } else
                        printk("svc: socket %p: no user data\n", sk);
        }
}

/*
 * A state change on a connected socket means it's dying or dead.
 */
static void svc_tcp_state_change(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        dprintk("svc: socket %p TCP (connected) state change %d (svsk %p)\n",
                sk, sk->sk_state, sk->sk_user_data);

        if (!svsk)
                printk("svc: socket %p: no user data\n", sk);
        else {
                /* Refer to svc_setup_socket() for details. */
                rmb();
                svsk->sk_ostate(sk);
                if (sk->sk_state != TCP_ESTABLISHED) {
                        set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
                        svc_xprt_enqueue(&svsk->sk_xprt);
                }
        }
}

/*
 * Accept a TCP connection
 */
static struct svc_xprt *svc_tcp_accept(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct sockaddr_storage addr;
        struct sockaddr *sin = (struct sockaddr *) &addr;
        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
        struct socket   *sock = svsk->sk_sock;
        struct socket   *newsock;
        struct svc_sock *newsvsk;
        int             err, slen;
        RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);

        dprintk("svc: tcp_accept %p sock %p\n", svsk, sock);
        if (!sock)
                return NULL;

        clear_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);
        err = kernel_accept(sock, &newsock, O_NONBLOCK);
        if (err < 0) {
                if (err == -ENOMEM)
                        printk(KERN_WARNING "%s: no more sockets!\n",
                               serv->sv_name);
                else if (err != -EAGAIN)
                        net_warn_ratelimited("%s: accept failed (err %d)!\n",
                                             serv->sv_name, -err);
                return NULL;
        }
        set_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);

        err = kernel_getpeername(newsock, sin);
        if (err < 0) {
                net_warn_ratelimited("%s: peername failed (err %d)!\n",
                                     serv->sv_name, -err);
                goto failed;            /* aborted connection or whatever */
        }
        slen = err;

        /* Ideally, we would want to reject connections from unauthorized
         * hosts here, but when we get encryption, the IP of the host won't
         * tell us anything.  For now just warn about unpriv connections.
         */
        if (!svc_port_is_privileged(sin)) {
                dprintk("%s: connect from unprivileged port: %s\n",
                        serv->sv_name,
                        __svc_print_addr(sin, buf, sizeof(buf)));
        }
        dprintk("%s: connect from %s\n", serv->sv_name,
                __svc_print_addr(sin, buf, sizeof(buf)));

        /* Reset the inherited callbacks before calling svc_setup_socket */
        newsock->sk->sk_state_change = svsk->sk_ostate;
        newsock->sk->sk_data_ready = svsk->sk_odata;
        newsock->sk->sk_write_space = svsk->sk_owspace;

        /* make sure that a write doesn't block forever when
         * low on memory
         */
        newsock->sk->sk_sndtimeo = HZ*30;

        newsvsk = svc_setup_socket(serv, newsock,
                                 (SVC_SOCK_ANONYMOUS | SVC_SOCK_TEMPORARY));
        if (IS_ERR(newsvsk))
                goto failed;
        svc_xprt_set_remote(&newsvsk->sk_xprt, sin, slen);
        err = kernel_getsockname(newsock, sin);
        slen = err;
        if (unlikely(err < 0)) {
                dprintk("svc_tcp_accept: kernel_getsockname error %d\n", -err);
                slen = offsetof(struct sockaddr, sa_data);
        }
        svc_xprt_set_local(&newsvsk->sk_xprt, sin, slen);

        if (sock_is_loopback(newsock->sk))
                set_bit(XPT_LOCAL, &newsvsk->sk_xprt.xpt_flags);
        else
                clear_bit(XPT_LOCAL, &newsvsk->sk_xprt.xpt_flags);
        if (serv->sv_stats)
                serv->sv_stats->nettcpconn++;

        return &newsvsk->sk_xprt;

failed:
        sock_release(newsock);
        return NULL;
}

static unsigned int svc_tcp_restore_pages(struct svc_sock *svsk, struct svc_rqst *rqstp)
{
        unsigned int i, len, npages;

        if (svsk->sk_datalen == 0)
                return 0;
        len = svsk->sk_datalen;
        npages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < npages; i++) {
                if (rqstp->rq_pages[i] != NULL)
                        put_page(rqstp->rq_pages[i]);
                BUG_ON(svsk->sk_pages[i] == NULL);
                rqstp->rq_pages[i] = svsk->sk_pages[i];
                svsk->sk_pages[i] = NULL;
        }
        rqstp->rq_arg.head[0].iov_base = page_address(rqstp->rq_pages[0]);
        return len;
}

static void svc_tcp_save_pages(struct svc_sock *svsk, struct svc_rqst *rqstp)
{
        unsigned int i, len, npages;

        if (svsk->sk_datalen == 0)
                return;
        len = svsk->sk_datalen;
        npages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < npages; i++) {
                svsk->sk_pages[i] = rqstp->rq_pages[i];
                rqstp->rq_pages[i] = NULL;
        }
}

static void svc_tcp_clear_pages(struct svc_sock *svsk)
{
        unsigned int i, len, npages;

        if (svsk->sk_datalen == 0)
                goto out;
        len = svsk->sk_datalen;
        npages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < npages; i++) {
                if (svsk->sk_pages[i] == NULL) {
                        WARN_ON_ONCE(1);
                        continue;
                }
                put_page(svsk->sk_pages[i]);
                svsk->sk_pages[i] = NULL;
        }
out:
        svsk->sk_tcplen = 0;
        svsk->sk_datalen = 0;
}

/*
 * Receive fragment record header.
 * If we haven't gotten the record length yet, get the next four bytes.
 */
static int svc_tcp_recv_record(struct svc_sock *svsk, struct svc_rqst *rqstp)
{
        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
        unsigned int want;
        int len;

        if (svsk->sk_tcplen < sizeof(rpc_fraghdr)) {
                struct kvec     iov;

                want = sizeof(rpc_fraghdr) - svsk->sk_tcplen;
                iov.iov_base = ((char *) &svsk->sk_reclen) + svsk->sk_tcplen;
                iov.iov_len  = want;
                len = svc_recvfrom(rqstp, &iov, 1, want, 0);
                if (len < 0)
                        goto error;
                svsk->sk_tcplen += len;

                if (len < want) {
                        dprintk("svc: short recvfrom while reading record "
                                "length (%d of %d)\n", len, want);
                        return -EAGAIN;
                }

                dprintk("svc: TCP record, %d bytes\n", svc_sock_reclen(svsk));
                if (svc_sock_reclen(svsk) + svsk->sk_datalen >
                                                        serv->sv_max_mesg) {
                        net_notice_ratelimited("RPC: fragment too large: %d\n",
                                        svc_sock_reclen(svsk));
                        goto err_delete;
                }
        }

        return svc_sock_reclen(svsk);
error:
        dprintk("RPC: TCP recv_record got %d\n", len);
        return len;
err_delete:
        set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
        return -EAGAIN;
}

static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
{
        struct rpc_xprt *bc_xprt = svsk->sk_xprt.xpt_bc_xprt;
        struct rpc_rqst *req = NULL;
        struct kvec *src, *dst;
        __be32 *p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
        __be32 xid;
        __be32 calldir;

        xid = *p++;
        calldir = *p;

        if (!bc_xprt)
                return -EAGAIN;
        spin_lock(&bc_xprt->queue_lock);
        req = xprt_lookup_rqst(bc_xprt, xid);
        if (!req)
                goto unlock_notfound;

        memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
        /*
         * XXX!: cheating for now!  Only copying HEAD.
         * But we know this is good enough for now (in fact, for any
         * callback reply in the forseeable future).
         */
        dst = &req->rq_private_buf.head[0];
        src = &rqstp->rq_arg.head[0];
        if (dst->iov_len < src->iov_len)
                goto unlock_eagain; /* whatever; just giving up. */
        memcpy(dst->iov_base, src->iov_base, src->iov_len);
        xprt_complete_rqst(req->rq_task, rqstp->rq_arg.len);
        rqstp->rq_arg.len = 0;
        spin_unlock(&bc_xprt->queue_lock);
        return 0;
unlock_notfound:
        printk(KERN_NOTICE
                "%s: Got unrecognized reply: "
                "calldir 0x%x xpt_bc_xprt %p xid %08x\n",
                __func__, ntohl(calldir),
                bc_xprt, ntohl(xid));
unlock_eagain:
        spin_unlock(&bc_xprt->queue_lock);
        return -EAGAIN;

}

static int copy_pages_to_kvecs(struct kvec *vec, struct page **pages, int len)
{
        int i = 0;
        int t = 0;

        while (t < len) {
                vec[i].iov_base = page_address(pages[i]);
                vec[i].iov_len = PAGE_SIZE;
                i++;
                t += PAGE_SIZE;
        }
        return i;
}

static void svc_tcp_fragment_received(struct svc_sock *svsk)
{
        /* If we have more data, signal svc_xprt_enqueue() to try again */
        dprintk("svc: TCP %s record (%d bytes)\n",
                svc_sock_final_rec(svsk) ? "final" : "nonfinal",
                svc_sock_reclen(svsk));
        svsk->sk_tcplen = 0;
        svsk->sk_reclen = 0;
}

/*
 * Receive data from a TCP socket.
 */
static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
        int             len;
        struct kvec *vec;
        unsigned int want, base;
        __be32 *p;
        __be32 calldir;
        int pnum;

        dprintk("svc: tcp_recv %p data %d conn %d close %d\n",
                svsk, test_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags),
                test_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags),
                test_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags));

        len = svc_tcp_recv_record(svsk, rqstp);
        if (len < 0)
                goto error;

        base = svc_tcp_restore_pages(svsk, rqstp);
        want = svc_sock_reclen(svsk) - (svsk->sk_tcplen - sizeof(rpc_fraghdr));

        vec = rqstp->rq_vec;

        pnum = copy_pages_to_kvecs(&vec[0], &rqstp->rq_pages[0], base + want);

        rqstp->rq_respages = &rqstp->rq_pages[pnum];
        rqstp->rq_next_page = rqstp->rq_respages + 1;

        /* Now receive data */
        len = svc_recvfrom(rqstp, vec, pnum, base + want, base);
        if (len >= 0) {
                svsk->sk_tcplen += len;
                svsk->sk_datalen += len;
        }
        if (len != want || !svc_sock_final_rec(svsk)) {
                svc_tcp_save_pages(svsk, rqstp);
                if (len < 0 && len != -EAGAIN)
                        goto err_delete;
                if (len == want)
                        svc_tcp_fragment_received(svsk);
                else
                        dprintk("svc: incomplete TCP record (%d of %d)\n",
                                (int)(svsk->sk_tcplen - sizeof(rpc_fraghdr)),
                                svc_sock_reclen(svsk));
                goto err_noclose;
        }

        if (svsk->sk_datalen < 8) {
                svsk->sk_datalen = 0;
                goto err_delete; /* client is nuts. */
        }

        rqstp->rq_arg.len = svsk->sk_datalen;
        rqstp->rq_arg.page_base = 0;
        if (rqstp->rq_arg.len <= rqstp->rq_arg.head[0].iov_len) {
                rqstp->rq_arg.head[0].iov_len = rqstp->rq_arg.len;
                rqstp->rq_arg.page_len = 0;
        } else
                rqstp->rq_arg.page_len = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len;

        rqstp->rq_xprt_ctxt   = NULL;
        rqstp->rq_prot        = IPPROTO_TCP;
        if (test_bit(XPT_LOCAL, &svsk->sk_xprt.xpt_flags))
                set_bit(RQ_LOCAL, &rqstp->rq_flags);
        else
                clear_bit(RQ_LOCAL, &rqstp->rq_flags);

        p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
        calldir = p[1];
        if (calldir)
                len = receive_cb_reply(svsk, rqstp);

        /* Reset TCP read info */
        svsk->sk_datalen = 0;
        svc_tcp_fragment_received(svsk);

        if (len < 0)
                goto error;

        svc_xprt_copy_addrs(rqstp, &svsk->sk_xprt);
        if (serv->sv_stats)
                serv->sv_stats->nettcpcnt++;

        return rqstp->rq_arg.len;

error:
        if (len != -EAGAIN)
                goto err_delete;
        dprintk("RPC: TCP recvfrom got EAGAIN\n");
        return 0;
err_delete:
        printk(KERN_NOTICE "%s: recvfrom returned errno %d\n",
               svsk->sk_xprt.xpt_server->sv_name, -len);
        set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
err_noclose:
        return 0;       /* record not complete */
}

/*
 * Send out data on TCP socket.
 */
static int svc_tcp_sendto(struct svc_rqst *rqstp)
{
        struct xdr_buf  *xbufp = &rqstp->rq_res;
        int sent;
        __be32 reclen;

        /* Set up the first element of the reply kvec.
         * Any other kvecs that may be in use have been taken
         * care of by the server implementation itself.
         */
        reclen = htonl(0x80000000|((xbufp->len ) - 4));
        memcpy(xbufp->head[0].iov_base, &reclen, 4);

        sent = svc_sendto(rqstp, &rqstp->rq_res);
        if (sent != xbufp->len) {
                printk(KERN_NOTICE
                       "rpc-srv/tcp: %s: %s %d when sending %d bytes "
                       "- shutting down socket\n",
                       rqstp->rq_xprt->xpt_server->sv_name,
                       (sent<0)?"got error":"sent only",
                       sent, xbufp->len);
                set_bit(XPT_CLOSE, &rqstp->rq_xprt->xpt_flags);
                svc_xprt_enqueue(rqstp->rq_xprt);
                sent = -EAGAIN;
        }
        return sent;
}

static struct svc_xprt *svc_tcp_create(struct svc_serv *serv,
                                       struct net *net,
                                       struct sockaddr *sa, int salen,
                                       int flags)
{
        return svc_create_socket(serv, IPPROTO_TCP, net, sa, salen, flags);
}

static const struct svc_xprt_ops svc_tcp_ops = {
        .xpo_create = svc_tcp_create,
        .xpo_recvfrom = svc_tcp_recvfrom,
        .xpo_sendto = svc_tcp_sendto,
        .xpo_release_rqst = svc_release_skb,
        .xpo_detach = svc_tcp_sock_detach,
        .xpo_free = svc_sock_free,
        .xpo_has_wspace = svc_tcp_has_wspace,
        .xpo_accept = svc_tcp_accept,
        .xpo_secure_port = svc_sock_secure_port,
        .xpo_kill_temp_xprt = svc_tcp_kill_temp_xprt,
};

static struct svc_xprt_class svc_tcp_class = {
        .xcl_name = "tcp",
        .xcl_owner = THIS_MODULE,
        .xcl_ops = &svc_tcp_ops,
        .xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
        .xcl_ident = XPRT_TRANSPORT_TCP,
};

void svc_init_xprt_sock(void)
{
        svc_reg_xprt_class(&svc_tcp_class);
        svc_reg_xprt_class(&svc_udp_class);
}

void svc_cleanup_xprt_sock(void)
{
        svc_unreg_xprt_class(&svc_tcp_class);
        svc_unreg_xprt_class(&svc_udp_class);
}

static void svc_tcp_init(struct svc_sock *svsk, struct svc_serv *serv)
{
        struct sock     *sk = svsk->sk_sk;

        svc_xprt_init(sock_net(svsk->sk_sock->sk), &svc_tcp_class,
                      &svsk->sk_xprt, serv);
        set_bit(XPT_CACHE_AUTH, &svsk->sk_xprt.xpt_flags);
        set_bit(XPT_CONG_CTRL, &svsk->sk_xprt.xpt_flags);
        if (sk->sk_state == TCP_LISTEN) {
                dprintk("setting up TCP socket for listening\n");
                strcpy(svsk->sk_xprt.xpt_remotebuf, "listener");
                set_bit(XPT_LISTENER, &svsk->sk_xprt.xpt_flags);
                sk->sk_data_ready = svc_tcp_listen_data_ready;
                set_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);
        } else {
                dprintk("setting up TCP socket for reading\n");
                sk->sk_state_change = svc_tcp_state_change;
                sk->sk_data_ready = svc_data_ready;
                sk->sk_write_space = svc_write_space;

                svsk->sk_reclen = 0;
                svsk->sk_tcplen = 0;
                svsk->sk_datalen = 0;
                memset(&svsk->sk_pages[0], 0, sizeof(svsk->sk_pages));

                tcp_sk(sk)->nonagle |= TCP_NAGLE_OFF;

                set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
                switch (sk->sk_state) {
                case TCP_SYN_RECV:
                case TCP_ESTABLISHED:
                        break;
                default:
                        set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
                }
        }
}

void svc_sock_update_bufs(struct svc_serv *serv)
{
        /*
         * The number of server threads has changed. Update
         * rcvbuf and sndbuf accordingly on all sockets
         */
        struct svc_sock *svsk;

        spin_lock_bh(&serv->sv_lock);
        list_for_each_entry(svsk, &serv->sv_permsocks, sk_xprt.xpt_list)
                set_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags);
        spin_unlock_bh(&serv->sv_lock);
}
EXPORT_SYMBOL_GPL(svc_sock_update_bufs);

/*
 * Initialize socket for RPC use and create svc_sock struct
 */
static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
                                                struct socket *sock,
                                                int flags)
{
        struct svc_sock *svsk;
        struct sock     *inet;
        int             pmap_register = !(flags & SVC_SOCK_ANONYMOUS);
        int             err = 0;

        dprintk("svc: svc_setup_socket %p\n", sock);
        svsk = kzalloc(sizeof(*svsk), GFP_KERNEL);
        if (!svsk)
                return ERR_PTR(-ENOMEM);

        inet = sock->sk;

        /* Register socket with portmapper */
        if (pmap_register)
                err = svc_register(serv, sock_net(sock->sk), inet->sk_family,
                                     inet->sk_protocol,
                                     ntohs(inet_sk(inet)->inet_sport));

        if (err < 0) {
                kfree(svsk);
                return ERR_PTR(err);
        }

        svsk->sk_sock = sock;
        svsk->sk_sk = inet;
        svsk->sk_ostate = inet->sk_state_change;
        svsk->sk_odata = inet->sk_data_ready;
        svsk->sk_owspace = inet->sk_write_space;
        /*
         * This barrier is necessary in order to prevent race condition
         * with svc_data_ready(), svc_listen_data_ready() and others
         * when calling callbacks above.
         */
        wmb();
        inet->sk_user_data = svsk;

        /* Initialize the socket */
        if (sock->type == SOCK_DGRAM)
                svc_udp_init(svsk, serv);
        else
                svc_tcp_init(svsk, serv);

        dprintk("svc: svc_setup_socket created %p (inet %p), "
                        "listen %d close %d\n",
                        svsk, svsk->sk_sk,
                        test_bit(XPT_LISTENER, &svsk->sk_xprt.xpt_flags),
                        test_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags));

        return svsk;
}

bool svc_alien_sock(struct net *net, int fd)
{
        int err;
        struct socket *sock = sockfd_lookup(fd, &err);
        bool ret = false;

        if (!sock)
                goto out;
        if (sock_net(sock->sk) != net)
                ret = true;
        sockfd_put(sock);
out:
        return ret;
}
EXPORT_SYMBOL_GPL(svc_alien_sock);

/**
 * svc_addsock - add a listener socket to an RPC service
 * @serv: pointer to RPC service to which to add a new listener
 * @fd: file descriptor of the new listener
 * @name_return: pointer to buffer to fill in with name of listener
 * @len: size of the buffer
 * @cred: credential
 *
 * Fills in socket name and returns positive length of name if successful.
 * Name is terminated with '\n'.  On error, returns a negative errno
 * value.
 */
int svc_addsock(struct svc_serv *serv, const int fd, char *name_return,
                const size_t len, const struct cred *cred)
{
        int err = 0;
        struct socket *so = sockfd_lookup(fd, &err);
        struct svc_sock *svsk = NULL;
        struct sockaddr_storage addr;
        struct sockaddr *sin = (struct sockaddr *)&addr;
        int salen;

        if (!so)
                return err;
        err = -EAFNOSUPPORT;
        if ((so->sk->sk_family != PF_INET) && (so->sk->sk_family != PF_INET6))
                goto out;
        err =  -EPROTONOSUPPORT;
        if (so->sk->sk_protocol != IPPROTO_TCP &&
            so->sk->sk_protocol != IPPROTO_UDP)
                goto out;
        err = -EISCONN;
        if (so->state > SS_UNCONNECTED)
                goto out;
        err = -ENOENT;
        if (!try_module_get(THIS_MODULE))
                goto out;
        svsk = svc_setup_socket(serv, so, SVC_SOCK_DEFAULTS);
        if (IS_ERR(svsk)) {
                module_put(THIS_MODULE);
                err = PTR_ERR(svsk);
                goto out;
        }
        salen = kernel_getsockname(svsk->sk_sock, sin);
        if (salen >= 0)
                svc_xprt_set_local(&svsk->sk_xprt, sin, salen);
        svsk->sk_xprt.xpt_cred = get_cred(cred);
        svc_add_new_perm_xprt(serv, &svsk->sk_xprt);
        return svc_one_sock_name(svsk, name_return, len);
out:
        sockfd_put(so);
        return err;
}
EXPORT_SYMBOL_GPL(svc_addsock);

/*
 * Create socket for RPC service.
 */
static struct svc_xprt *svc_create_socket(struct svc_serv *serv,
                                          int protocol,
                                          struct net *net,
                                          struct sockaddr *sin, int len,
                                          int flags)
{
        struct svc_sock *svsk;
        struct socket   *sock;
        int             error;
        int             type;
        struct sockaddr_storage addr;
        struct sockaddr *newsin = (struct sockaddr *)&addr;
        int             newlen;
        int             family;
        int             val;
        RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);

        dprintk("svc: svc_create_socket(%s, %d, %s)\n",
                        serv->sv_program->pg_name, protocol,
                        __svc_print_addr(sin, buf, sizeof(buf)));

        if (protocol != IPPROTO_UDP && protocol != IPPROTO_TCP) {
                printk(KERN_WARNING "svc: only UDP and TCP "
                                "sockets supported\n");
                return ERR_PTR(-EINVAL);
        }

        type = (protocol == IPPROTO_UDP)? SOCK_DGRAM : SOCK_STREAM;
        switch (sin->sa_family) {
        case AF_INET6:
                family = PF_INET6;
                break;
        case AF_INET:
                family = PF_INET;
                break;
        default:
                return ERR_PTR(-EINVAL);
        }

        error = __sock_create(net, family, type, protocol, &sock, 1);
        if (error < 0)
                return ERR_PTR(error);

        svc_reclassify_socket(sock);

        /*
         * If this is an PF_INET6 listener, we want to avoid
         * getting requests from IPv4 remotes.  Those should
         * be shunted to a PF_INET listener via rpcbind.
         */
        val = 1;
        if (family == PF_INET6)
                kernel_setsockopt(sock, SOL_IPV6, IPV6_V6ONLY,
                                        (char *)&val, sizeof(val));

        if (type == SOCK_STREAM)
                sock->sk->sk_reuse = SK_CAN_REUSE; /* allow address reuse */
        error = kernel_bind(sock, sin, len);
        if (error < 0)
                goto bummer;

        error = kernel_getsockname(sock, newsin);
        if (error < 0)
                goto bummer;
        newlen = error;

        if (protocol == IPPROTO_TCP) {
                if ((error = kernel_listen(sock, 64)) < 0)
                        goto bummer;
        }

        svsk = svc_setup_socket(serv, sock, flags);
        if (IS_ERR(svsk)) {
                error = PTR_ERR(svsk);
                goto bummer;
        }
        svc_xprt_set_local(&svsk->sk_xprt, newsin, newlen);
        return (struct svc_xprt *)svsk;
bummer:
        dprintk("svc: svc_create_socket error = %d\n", -error);
        sock_release(sock);
        return ERR_PTR(error);
}

/*
 * Detach the svc_sock from the socket so that no
 * more callbacks occur.
 */
static void svc_sock_detach(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct sock *sk = svsk->sk_sk;

        dprintk("svc: svc_sock_detach(%p)\n", svsk);

        /* put back the old socket callbacks */
        lock_sock(sk);
        sk->sk_state_change = svsk->sk_ostate;
        sk->sk_data_ready = svsk->sk_odata;
        sk->sk_write_space = svsk->sk_owspace;
        sk->sk_user_data = NULL;
        release_sock(sk);
}

/*
 * Disconnect the socket, and reset the callbacks
 */
static void svc_tcp_sock_detach(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);

        dprintk("svc: svc_tcp_sock_detach(%p)\n", svsk);

        svc_sock_detach(xprt);

        if (!test_bit(XPT_LISTENER, &xprt->xpt_flags)) {
                svc_tcp_clear_pages(svsk);
                kernel_sock_shutdown(svsk->sk_sock, SHUT_RDWR);
        }
}

/*
 * Free the svc_sock's socket resources and the svc_sock itself.
 */
static void svc_sock_free(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        dprintk("svc: svc_sock_free(%p)\n", svsk);

        if (svsk->sk_sock->file)
                sockfd_put(svsk->sk_sock);
        else
                sock_release(svsk->sk_sock);
        kfree(svsk);
}