/*
 * In-kernel rpcbind client supporting versions 2, 3, and 4 of the rpcbind
 * protocol
 *
 * Based on RFC 1833: "Binding Protocols for ONC RPC Version 2" and
 * RFC 3530: "Network File System (NFS) version 4 Protocol"
 *
 * Original: Gilles Quillard, Bull Open Source, 2005 <gilles.quillard@bull.net>
 * Updated: Chuck Lever, Oracle Corporation, 2007 <chuck.lever@oracle.com>
 *
 * Descended from net/sunrpc/pmap_clnt.c,
 *  Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/module.h>

#include <linux/types.h>
#include <linux/socket.h>
#include <linux/un.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <net/ipv6.h>

#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/sched.h>
#include <linux/sunrpc/xprtsock.h>

#include "netns.h"

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY        RPCDBG_BIND
#endif

#define RPCBIND_SOCK_PATHNAME   "/var/run/rpcbind.sock"

#define RPCBIND_PROGRAM         (100000u)
#define RPCBIND_PORT            (111u)

#define RPCBVERS_2              (2u)
#define RPCBVERS_3              (3u)
#define RPCBVERS_4              (4u)

enum {
        RPCBPROC_NULL,
        RPCBPROC_SET,
        RPCBPROC_UNSET,
        RPCBPROC_GETPORT,
        RPCBPROC_GETADDR = 3,           /* alias for GETPORT */
        RPCBPROC_DUMP,
        RPCBPROC_CALLIT,
        RPCBPROC_BCAST = 5,             /* alias for CALLIT */
        RPCBPROC_GETTIME,
        RPCBPROC_UADDR2TADDR,
        RPCBPROC_TADDR2UADDR,
        RPCBPROC_GETVERSADDR,
        RPCBPROC_INDIRECT,
        RPCBPROC_GETADDRLIST,
        RPCBPROC_GETSTAT,
};

/*
 * r_owner
 *
 * The "owner" is allowed to unset a service in the rpcbind database.
 *
 * For AF_LOCAL SET/UNSET requests, rpcbind treats this string as a
 * UID which it maps to a local user name via a password lookup.
 * In all other cases it is ignored.
 *
 * For SET/UNSET requests, user space provides a value, even for
 * network requests, and GETADDR uses an empty string.  We follow
 * those precedents here.
 */
#define RPCB_OWNER_STRING       "0"
#define RPCB_MAXOWNERLEN        sizeof(RPCB_OWNER_STRING)

/*
 * XDR data type sizes
 */
#define RPCB_program_sz         (1)
#define RPCB_version_sz         (1)
#define RPCB_protocol_sz        (1)
#define RPCB_port_sz            (1)
#define RPCB_boolean_sz         (1)

#define RPCB_netid_sz           (1 + XDR_QUADLEN(RPCBIND_MAXNETIDLEN))
#define RPCB_addr_sz            (1 + XDR_QUADLEN(RPCBIND_MAXUADDRLEN))
#define RPCB_ownerstring_sz     (1 + XDR_QUADLEN(RPCB_MAXOWNERLEN))

/*
 * XDR argument and result sizes
 */
#define RPCB_mappingargs_sz     (RPCB_program_sz + RPCB_version_sz + \
                                RPCB_protocol_sz + RPCB_port_sz)
#define RPCB_getaddrargs_sz     (RPCB_program_sz + RPCB_version_sz + \
                                RPCB_netid_sz + RPCB_addr_sz + \
                                RPCB_ownerstring_sz)

#define RPCB_getportres_sz      RPCB_port_sz
#define RPCB_setres_sz          RPCB_boolean_sz

/*
 * Note that RFC 1833 does not put any size restrictions on the
 * address string returned by the remote rpcbind database.
 */
#define RPCB_getaddrres_sz      RPCB_addr_sz

static void                     rpcb_getport_done(struct rpc_task *, void *);
static void                     rpcb_map_release(void *data);
static const struct rpc_program rpcb_program;

struct rpcbind_args {
        struct rpc_xprt *       r_xprt;

        u32                     r_prog;
        u32                     r_vers;
        u32                     r_prot;
        unsigned short          r_port;
        const char *            r_netid;
        const char *            r_addr;
        const char *            r_owner;

        int                     r_status;
};

static struct rpc_procinfo rpcb_procedures2[];
static struct rpc_procinfo rpcb_procedures3[];
static struct rpc_procinfo rpcb_procedures4[];

struct rpcb_info {
        u32                     rpc_vers;
        struct rpc_procinfo *   rpc_proc;
};

static const struct rpcb_info rpcb_next_version[];
static const struct rpcb_info rpcb_next_version6[];

static const struct rpc_call_ops rpcb_getport_ops = {
        .rpc_call_done          = rpcb_getport_done,
        .rpc_release            = rpcb_map_release,
};

static void rpcb_wake_rpcbind_waiters(struct rpc_xprt *xprt, int status)
{
        xprt_clear_binding(xprt);
        rpc_wake_up_status(&xprt->binding, status);
}

static void rpcb_map_release(void *data)
{
        struct rpcbind_args *map = data;

        rpcb_wake_rpcbind_waiters(map->r_xprt, map->r_status);
        xprt_put(map->r_xprt);
        kfree(map->r_addr);
        kfree(map);
}

static int rpcb_get_local(struct net *net)
{
        int cnt;
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        spin_lock(&sn->rpcb_clnt_lock);
        if (sn->rpcb_users)
                sn->rpcb_users++;
        cnt = sn->rpcb_users;
        spin_unlock(&sn->rpcb_clnt_lock);

        return cnt;
}

void rpcb_put_local(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct rpc_clnt *clnt = sn->rpcb_local_clnt;
        struct rpc_clnt *clnt4 = sn->rpcb_local_clnt4;
        int shutdown = 0;

        spin_lock(&sn->rpcb_clnt_lock);
        if (sn->rpcb_users) {
                if (--sn->rpcb_users == 0) {
                        sn->rpcb_local_clnt = NULL;
                        sn->rpcb_local_clnt4 = NULL;
                }
                shutdown = !sn->rpcb_users;
        }
        spin_unlock(&sn->rpcb_clnt_lock);

        if (shutdown) {
                /*
                 * cleanup_rpcb_clnt - remove xprtsock's sysctls, unregister
                 */
                if (clnt4)
                        rpc_shutdown_client(clnt4);
                if (clnt)
                        rpc_shutdown_client(clnt);
        }
}

static void rpcb_set_local(struct net *net, struct rpc_clnt *clnt,
                        struct rpc_clnt *clnt4,
                        bool is_af_local)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        /* Protected by rpcb_create_local_mutex */
        sn->rpcb_local_clnt = clnt;
        sn->rpcb_local_clnt4 = clnt4;
        sn->rpcb_is_af_local = is_af_local ? 1 : 0;
        smp_wmb(); 
        sn->rpcb_users = 1;
        dprintk("RPC:       created new rpcb local clients (rpcb_local_clnt: "
                        "%p, rpcb_local_clnt4: %p) for net %p%s\n",
                        sn->rpcb_local_clnt, sn->rpcb_local_clnt4,
                        net, (net == &init_net) ? " (init_net)" : "");
}

/*
 * Returns zero on success, otherwise a negative errno value
 * is returned.
 */
static int rpcb_create_local_unix(struct net *net)
{
        static const struct sockaddr_un rpcb_localaddr_rpcbind = {
                .sun_family             = AF_LOCAL,
                .sun_path               = RPCBIND_SOCK_PATHNAME,
        };
        struct rpc_create_args args = {
                .net            = net,
                .protocol       = XPRT_TRANSPORT_LOCAL,
                .address        = (struct sockaddr *)&rpcb_localaddr_rpcbind,
                .addrsize       = sizeof(rpcb_localaddr_rpcbind),
                .servername     = "localhost",
                .program        = &rpcb_program,
                .version        = RPCBVERS_2,
                .authflavor     = RPC_AUTH_NULL,
                /*
                 * We turn off the idle timeout to prevent the kernel
                 * from automatically disconnecting the socket.
                 * Otherwise, we'd have to cache the mount namespace
                 * of the caller and somehow pass that to the socket
                 * reconnect code.
                 */
                .flags          = RPC_CLNT_CREATE_NO_IDLE_TIMEOUT,
        };
        struct rpc_clnt *clnt, *clnt4;
        int result = 0;

        /*
         * Because we requested an RPC PING at transport creation time,
         * this works only if the user space portmapper is rpcbind, and
         * it's listening on AF_LOCAL on the named socket.
         */
        clnt = rpc_create(&args);
        if (IS_ERR(clnt)) {
                dprintk("RPC:       failed to create AF_LOCAL rpcbind "
                                "client (errno %ld).\n", PTR_ERR(clnt));
                result = PTR_ERR(clnt);
                goto out;
        }

        clnt4 = rpc_bind_new_program(clnt, &rpcb_program, RPCBVERS_4);
        if (IS_ERR(clnt4)) {
                dprintk("RPC:       failed to bind second program to "
                                "rpcbind v4 client (errno %ld).\n",
                                PTR_ERR(clnt4));
                clnt4 = NULL;
        }

        rpcb_set_local(net, clnt, clnt4, true);

out:
        return result;
}

/*
 * Returns zero on success, otherwise a negative errno value
 * is returned.
 */
static int rpcb_create_local_net(struct net *net)
{
        static const struct sockaddr_in rpcb_inaddr_loopback = {
                .sin_family             = AF_INET,
                .sin_addr.s_addr        = htonl(INADDR_LOOPBACK),
                .sin_port               = htons(RPCBIND_PORT),
        };
        struct rpc_create_args args = {
                .net            = net,
                .protocol       = XPRT_TRANSPORT_TCP,
                .address        = (struct sockaddr *)&rpcb_inaddr_loopback,
                .addrsize       = sizeof(rpcb_inaddr_loopback),
                .servername     = "localhost",
                .program        = &rpcb_program,
                .version        = RPCBVERS_2,
                .authflavor     = RPC_AUTH_UNIX,
                .flags          = RPC_CLNT_CREATE_NOPING,
        };
        struct rpc_clnt *clnt, *clnt4;
        int result = 0;

        clnt = rpc_create(&args);
        if (IS_ERR(clnt)) {
                dprintk("RPC:       failed to create local rpcbind "
                                "client (errno %ld).\n", PTR_ERR(clnt));
                result = PTR_ERR(clnt);
                goto out;
        }

        /*
         * This results in an RPC ping.  On systems running portmapper,
         * the v4 ping will fail.  Proceed anyway, but disallow rpcb
         * v4 upcalls.
         */
        clnt4 = rpc_bind_new_program(clnt, &rpcb_program, RPCBVERS_4);
        if (IS_ERR(clnt4)) {
                dprintk("RPC:       failed to bind second program to "
                                "rpcbind v4 client (errno %ld).\n",
                                PTR_ERR(clnt4));
                clnt4 = NULL;
        }

        rpcb_set_local(net, clnt, clnt4, false);

out:
        return result;
}

/*
 * Returns zero on success, otherwise a negative errno value
 * is returned.
 */
int rpcb_create_local(struct net *net)
{
        static DEFINE_MUTEX(rpcb_create_local_mutex);
        int result = 0;

        if (rpcb_get_local(net))
                return result;

        mutex_lock(&rpcb_create_local_mutex);
        if (rpcb_get_local(net))
                goto out;

        if (rpcb_create_local_unix(net) != 0)
                result = rpcb_create_local_net(net);

out:
        mutex_unlock(&rpcb_create_local_mutex);
        return result;
}

static struct rpc_clnt *rpcb_create(struct net *net, const char *hostname,
                                    struct sockaddr *srvaddr, size_t salen,
                                    int proto, u32 version)
{
        struct rpc_create_args args = {
                .net            = net,
                .protocol       = proto,
                .address        = srvaddr,
                .addrsize       = salen,
                .servername     = hostname,
                .program        = &rpcb_program,
                .version        = version,
                .authflavor     = RPC_AUTH_UNIX,
                .flags          = (RPC_CLNT_CREATE_NOPING |
                                        RPC_CLNT_CREATE_NONPRIVPORT),
        };

        switch (srvaddr->sa_family) {
        case AF_INET:
                ((struct sockaddr_in *)srvaddr)->sin_port = htons(RPCBIND_PORT);
                break;
        case AF_INET6:
                ((struct sockaddr_in6 *)srvaddr)->sin6_port = htons(RPCBIND_PORT);
                break;
        default:
                return ERR_PTR(-EAFNOSUPPORT);
        }

        return rpc_create(&args);
}

static int rpcb_register_call(struct sunrpc_net *sn, struct rpc_clnt *clnt, struct rpc_message *msg, bool is_set)
{
        int flags = RPC_TASK_NOCONNECT;
        int error, result = 0;

        if (is_set || !sn->rpcb_is_af_local)
                flags = RPC_TASK_SOFTCONN;
        msg->rpc_resp = &result;

        error = rpc_call_sync(clnt, msg, flags);
        if (error < 0) {
                dprintk("RPC:       failed to contact local rpcbind "
                                "server (errno %d).\n", -error);
                return error;
        }

        if (!result)
                return -EACCES;
        return 0;
}

/**
 * rpcb_register - set or unset a port registration with the local rpcbind svc
 * @net: target network namespace
 * @prog: RPC program number to bind
 * @vers: RPC version number to bind
 * @prot: transport protocol to register
 * @port: port value to register
 *
 * Returns zero if the registration request was dispatched successfully
 * and the rpcbind daemon returned success.  Otherwise, returns an errno
 * value that reflects the nature of the error (request could not be
 * dispatched, timed out, or rpcbind returned an error).
 *
 * RPC services invoke this function to advertise their contact
 * information via the system's rpcbind daemon.  RPC services
 * invoke this function once for each [program, version, transport]
 * tuple they wish to advertise.
 *
 * Callers may also unregister RPC services that are no longer
 * available by setting the passed-in port to zero.  This removes
 * all registered transports for [program, version] from the local
 * rpcbind database.
 *
 * This function uses rpcbind protocol version 2 to contact the
 * local rpcbind daemon.
 *
 * Registration works over both AF_INET and AF_INET6, and services
 * registered via this function are advertised as available for any
 * address.  If the local rpcbind daemon is listening on AF_INET6,
 * services registered via this function will be advertised on
 * IN6ADDR_ANY (ie available for all AF_INET and AF_INET6
 * addresses).
 */
int rpcb_register(struct net *net, u32 prog, u32 vers, int prot, unsigned short port)
{
        struct rpcbind_args map = {
                .r_prog         = prog,
                .r_vers         = vers,
                .r_prot         = prot,
                .r_port         = port,
        };
        struct rpc_message msg = {
                .rpc_argp       = &map,
        };
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        bool is_set = false;

        dprintk("RPC:       %sregistering (%u, %u, %d, %u) with local "
                        "rpcbind\n", (port ? "" : "un"),
                        prog, vers, prot, port);

        msg.rpc_proc = &rpcb_procedures2[RPCBPROC_UNSET];
        if (port != 0) {
                msg.rpc_proc = &rpcb_procedures2[RPCBPROC_SET];
                is_set = true;
        }

        return rpcb_register_call(sn, sn->rpcb_local_clnt, &msg, is_set);
}

/*
 * Fill in AF_INET family-specific arguments to register
 */
static int rpcb_register_inet4(struct sunrpc_net *sn,
                               const struct sockaddr *sap,
                               struct rpc_message *msg)
{
        const struct sockaddr_in *sin = (const struct sockaddr_in *)sap;
        struct rpcbind_args *map = msg->rpc_argp;
        unsigned short port = ntohs(sin->sin_port);
        bool is_set = false;
        int result;

        map->r_addr = rpc_sockaddr2uaddr(sap, GFP_KERNEL);

        dprintk("RPC:       %sregistering [%u, %u, %s, '%s'] with "
                "local rpcbind\n", (port ? "" : "un"),
                        map->r_prog, map->r_vers,
                        map->r_addr, map->r_netid);

        msg->rpc_proc = &rpcb_procedures4[RPCBPROC_UNSET];
        if (port != 0) {
                msg->rpc_proc = &rpcb_procedures4[RPCBPROC_SET];
                is_set = true;
        }

        result = rpcb_register_call(sn, sn->rpcb_local_clnt4, msg, is_set);
        kfree(map->r_addr);
        return result;
}

/*
 * Fill in AF_INET6 family-specific arguments to register
 */
static int rpcb_register_inet6(struct sunrpc_net *sn,
                               const struct sockaddr *sap,
                               struct rpc_message *msg)
{
        const struct sockaddr_in6 *sin6 = (const struct sockaddr_in6 *)sap;
        struct rpcbind_args *map = msg->rpc_argp;
        unsigned short port = ntohs(sin6->sin6_port);
        bool is_set = false;
        int result;

        map->r_addr = rpc_sockaddr2uaddr(sap, GFP_KERNEL);

        dprintk("RPC:       %sregistering [%u, %u, %s, '%s'] with "
                "local rpcbind\n", (port ? "" : "un"),
                        map->r_prog, map->r_vers,
                        map->r_addr, map->r_netid);

        msg->rpc_proc = &rpcb_procedures4[RPCBPROC_UNSET];
        if (port != 0) {
                msg->rpc_proc = &rpcb_procedures4[RPCBPROC_SET];
                is_set = true;
        }

        result = rpcb_register_call(sn, sn->rpcb_local_clnt4, msg, is_set);
        kfree(map->r_addr);
        return result;
}

static int rpcb_unregister_all_protofamilies(struct sunrpc_net *sn,
                                             struct rpc_message *msg)
{
        struct rpcbind_args *map = msg->rpc_argp;

        dprintk("RPC:       unregistering [%u, %u, '%s'] with "
                "local rpcbind\n",
                        map->r_prog, map->r_vers, map->r_netid);

        map->r_addr = "";
        msg->rpc_proc = &rpcb_procedures4[RPCBPROC_UNSET];

        return rpcb_register_call(sn, sn->rpcb_local_clnt4, msg, false);
}

/**
 * rpcb_v4_register - set or unset a port registration with the local rpcbind
 * @net: target network namespace
 * @program: RPC program number of service to (un)register
 * @version: RPC version number of service to (un)register
 * @address: address family, IP address, and port to (un)register
 * @netid: netid of transport protocol to (un)register
 *
 * Returns zero if the registration request was dispatched successfully
 * and the rpcbind daemon returned success.  Otherwise, returns an errno
 * value that reflects the nature of the error (request could not be
 * dispatched, timed out, or rpcbind returned an error).
 *
 * RPC services invoke this function to advertise their contact
 * information via the system's rpcbind daemon.  RPC services
 * invoke this function once for each [program, version, address,
 * netid] tuple they wish to advertise.
 *
 * Callers may also unregister RPC services that are registered at a
 * specific address by setting the port number in @address to zero.
 * They may unregister all registered protocol families at once for
 * a service by passing a NULL @address argument.  If @netid is ""
 * then all netids for [program, version, address] are unregistered.
 *
 * This function uses rpcbind protocol version 4 to contact the
 * local rpcbind daemon.  The local rpcbind daemon must support
 * version 4 of the rpcbind protocol in order for these functions
 * to register a service successfully.
 *
 * Supported netids include "udp" and "tcp" for UDP and TCP over
 * IPv4, and "udp6" and "tcp6" for UDP and TCP over IPv6,
 * respectively.
 *
 * The contents of @address determine the address family and the
 * port to be registered.  The usual practice is to pass INADDR_ANY
 * as the raw address, but specifying a non-zero address is also
 * supported by this API if the caller wishes to advertise an RPC
 * service on a specific network interface.
 *
 * Note that passing in INADDR_ANY does not create the same service
 * registration as IN6ADDR_ANY.  The former advertises an RPC
 * service on any IPv4 address, but not on IPv6.  The latter
 * advertises the service on all IPv4 and IPv6 addresses.
 */
int rpcb_v4_register(struct net *net, const u32 program, const u32 version,
                     const struct sockaddr *address, const char *netid)
{
        struct rpcbind_args map = {
                .r_prog         = program,
                .r_vers         = version,
                .r_netid        = netid,
                .r_owner        = RPCB_OWNER_STRING,
        };
        struct rpc_message msg = {
                .rpc_argp       = &map,
        };
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        if (sn->rpcb_local_clnt4 == NULL)
                return -EPROTONOSUPPORT;

        if (address == NULL)
                return rpcb_unregister_all_protofamilies(sn, &msg);

        switch (address->sa_family) {
        case AF_INET:
                return rpcb_register_inet4(sn, address, &msg);
        case AF_INET6:
                return rpcb_register_inet6(sn, address, &msg);
        }

        return -EAFNOSUPPORT;
}

static struct rpc_task *rpcb_call_async(struct rpc_clnt *rpcb_clnt, struct rpcbind_args *map, struct rpc_procinfo *proc)
{
        struct rpc_message msg = {
                .rpc_proc = proc,
                .rpc_argp = map,
                .rpc_resp = map,
        };
        struct rpc_task_setup task_setup_data = {
                .rpc_client = rpcb_clnt,
                .rpc_message = &msg,
                .callback_ops = &rpcb_getport_ops,
                .callback_data = map,
                .flags = RPC_TASK_ASYNC | RPC_TASK_SOFTCONN,
        };

        return rpc_run_task(&task_setup_data);
}

/*
 * In the case where rpc clients have been cloned, we want to make
 * sure that we use the program number/version etc of the actual
 * owner of the xprt. To do so, we walk back up the tree of parents
 * to find whoever created the transport and/or whoever has the
 * autobind flag set.
 */
static struct rpc_clnt *rpcb_find_transport_owner(struct rpc_clnt *clnt)
{
        struct rpc_clnt *parent = clnt->cl_parent;
        struct rpc_xprt *xprt = rcu_dereference(clnt->cl_xprt);

        while (parent != clnt) {
                if (rcu_dereference(parent->cl_xprt) != xprt)
                        break;
                if (clnt->cl_autobind)
                        break;
                clnt = parent;
                parent = parent->cl_parent;
        }
        return clnt;
}

/**
 * rpcb_getport_async - obtain the port for a given RPC service on a given host
 * @task: task that is waiting for portmapper request
 *
 * This one can be called for an ongoing RPC request, and can be used in
 * an async (rpciod) context.
 */
void rpcb_getport_async(struct rpc_task *task)
{
        struct rpc_clnt *clnt;
        struct rpc_procinfo *proc;
        u32 bind_version;
        struct rpc_xprt *xprt;
        struct rpc_clnt *rpcb_clnt;
        struct rpcbind_args *map;
        struct rpc_task *child;
        struct sockaddr_storage addr;
        struct sockaddr *sap = (struct sockaddr *)&addr;
        size_t salen;
        int status;

        rcu_read_lock();
        do {
                clnt = rpcb_find_transport_owner(task->tk_client);
                xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
        } while (xprt == NULL);
        rcu_read_unlock();

        dprintk("RPC: %5u %s(%s, %u, %u, %d)\n",
                task->tk_pid, __func__,
                xprt->servername, clnt->cl_prog, clnt->cl_vers, xprt->prot);

        /* Put self on the wait queue to ensure we get notified if
         * some other task is already attempting to bind the port */
        rpc_sleep_on(&xprt->binding, task, NULL);

        if (xprt_test_and_set_binding(xprt)) {
                dprintk("RPC: %5u %s: waiting for another binder\n",
                        task->tk_pid, __func__);
                xprt_put(xprt);
                return;
        }

        /* Someone else may have bound if we slept */
        if (xprt_bound(xprt)) {
                status = 0;
                dprintk("RPC: %5u %s: already bound\n",
                        task->tk_pid, __func__);
                goto bailout_nofree;
        }

        /* Parent transport's destination address */
        salen = rpc_peeraddr(clnt, sap, sizeof(addr));

        /* Don't ever use rpcbind v2 for AF_INET6 requests */
        switch (sap->sa_family) {
        case AF_INET:
                proc = rpcb_next_version[xprt->bind_index].rpc_proc;
                bind_version = rpcb_next_version[xprt->bind_index].rpc_vers;
                break;
        case AF_INET6:
                proc = rpcb_next_version6[xprt->bind_index].rpc_proc;
                bind_version = rpcb_next_version6[xprt->bind_index].rpc_vers;
                break;
        default:
                status = -EAFNOSUPPORT;
                dprintk("RPC: %5u %s: bad address family\n",
                                task->tk_pid, __func__);
                goto bailout_nofree;
        }
        if (proc == NULL) {
                xprt->bind_index = 0;
                status = -EPFNOSUPPORT;
                dprintk("RPC: %5u %s: no more getport versions available\n",
                        task->tk_pid, __func__);
                goto bailout_nofree;
        }

        dprintk("RPC: %5u %s: trying rpcbind version %u\n",
                task->tk_pid, __func__, bind_version);

        rpcb_clnt = rpcb_create(xprt->xprt_net, xprt->servername, sap, salen,
                                xprt->prot, bind_version);
        if (IS_ERR(rpcb_clnt)) {
                status = PTR_ERR(rpcb_clnt);
                dprintk("RPC: %5u %s: rpcb_create failed, error %ld\n",
                        task->tk_pid, __func__, PTR_ERR(rpcb_clnt));
                goto bailout_nofree;
        }

        map = kzalloc(sizeof(struct rpcbind_args), GFP_ATOMIC);
        if (!map) {
                status = -ENOMEM;
                dprintk("RPC: %5u %s: no memory available\n",
                        task->tk_pid, __func__);
                goto bailout_release_client;
        }
        map->r_prog = clnt->cl_prog;
        map->r_vers = clnt->cl_vers;
        map->r_prot = xprt->prot;
        map->r_port = 0;
        map->r_xprt = xprt;
        map->r_status = -EIO;

        switch (bind_version) {
        case RPCBVERS_4:
        case RPCBVERS_3:
                map->r_netid = xprt->address_strings[RPC_DISPLAY_NETID];
                map->r_addr = rpc_sockaddr2uaddr(sap, GFP_ATOMIC);
                map->r_owner = "";
                break;
        case RPCBVERS_2:
                map->r_addr = NULL;
                break;
        default:
                BUG();
        }

        child = rpcb_call_async(rpcb_clnt, map, proc);
        rpc_release_client(rpcb_clnt);
        if (IS_ERR(child)) {
                /* rpcb_map_release() has freed the arguments */
                dprintk("RPC: %5u %s: rpc_run_task failed\n",
                        task->tk_pid, __func__);
                return;
        }

        xprt->stat.bind_count++;
        rpc_put_task(child);
        return;

bailout_release_client:
        rpc_release_client(rpcb_clnt);
bailout_nofree:
        rpcb_wake_rpcbind_waiters(xprt, status);
        task->tk_status = status;
        xprt_put(xprt);
}
EXPORT_SYMBOL_GPL(rpcb_getport_async);

/*
 * Rpcbind child task calls this callback via tk_exit.
 */
static void rpcb_getport_done(struct rpc_task *child, void *data)
{
        struct rpcbind_args *map = data;
        struct rpc_xprt *xprt = map->r_xprt;
        int status = child->tk_status;

        /* Garbage reply: retry with a lesser rpcbind version */
        if (status == -EIO)
                status = -EPROTONOSUPPORT;

        /* rpcbind server doesn't support this rpcbind protocol version */
        if (status == -EPROTONOSUPPORT)
                xprt->bind_index++;

        if (status < 0) {
                /* rpcbind server not available on remote host? */
                xprt->ops->set_port(xprt, 0);
        } else if (map->r_port == 0) {
                /* Requested RPC service wasn't registered on remote host */
                xprt->ops->set_port(xprt, 0);
                status = -EACCES;
        } else {
                /* Succeeded */
                xprt->ops->set_port(xprt, map->r_port);
                xprt_set_bound(xprt);
                status = 0;
        }

        dprintk("RPC: %5u rpcb_getport_done(status %d, port %u)\n",
                        child->tk_pid, status, map->r_port);

        map->r_status = status;
}

/*
 * XDR functions for rpcbind
 */

static void rpcb_enc_mapping(struct rpc_rqst *req, struct xdr_stream *xdr,
                             const struct rpcbind_args *rpcb)
{
        __be32 *p;

        dprintk("RPC: %5u encoding PMAP_%s call (%u, %u, %d, %u)\n",
                        req->rq_task->tk_pid,
                        req->rq_task->tk_msg.rpc_proc->p_name,
                        rpcb->r_prog, rpcb->r_vers, rpcb->r_prot, rpcb->r_port);

        p = xdr_reserve_space(xdr, RPCB_mappingargs_sz << 2);
        *p++ = cpu_to_be32(rpcb->r_prog);
        *p++ = cpu_to_be32(rpcb->r_vers);
        *p++ = cpu_to_be32(rpcb->r_prot);
        *p   = cpu_to_be32(rpcb->r_port);
}

static int rpcb_dec_getport(struct rpc_rqst *req, struct xdr_stream *xdr,
                            struct rpcbind_args *rpcb)
{
        unsigned long port;
        __be32 *p;

        rpcb->r_port = 0;

        p = xdr_inline_decode(xdr, 4);
        if (unlikely(p == NULL))
                return -EIO;

        port = be32_to_cpup(p);
        dprintk("RPC: %5u PMAP_%s result: %lu\n", req->rq_task->tk_pid,
                        req->rq_task->tk_msg.rpc_proc->p_name, port);
        if (unlikely(port > USHRT_MAX))
                return -EIO;

        rpcb->r_port = port;
        return 0;
}

static int rpcb_dec_set(struct rpc_rqst *req, struct xdr_stream *xdr,
                        unsigned int *boolp)
{
        __be32 *p;

        p = xdr_inline_decode(xdr, 4);
        if (unlikely(p == NULL))
                return -EIO;

        *boolp = 0;
        if (*p != xdr_zero)
                *boolp = 1;

        dprintk("RPC: %5u RPCB_%s call %s\n",
                        req->rq_task->tk_pid,
                        req->rq_task->tk_msg.rpc_proc->p_name,
                        (*boolp ? "succeeded" : "failed"));
        return 0;
}

static void encode_rpcb_string(struct xdr_stream *xdr, const char *string,
                               const u32 maxstrlen)
{
        __be32 *p;
        u32 len;

        len = strlen(string);
        WARN_ON_ONCE(len > maxstrlen);
        if (len > maxstrlen)
                /* truncate and hope for the best */
                len = maxstrlen;
        p = xdr_reserve_space(xdr, 4 + len);
        xdr_encode_opaque(p, string, len);
}

static void rpcb_enc_getaddr(struct rpc_rqst *req, struct xdr_stream *xdr,
                             const struct rpcbind_args *rpcb)
{
        __be32 *p;

        dprintk("RPC: %5u encoding RPCB_%s call (%u, %u, '%s', '%s')\n",
                        req->rq_task->tk_pid,
                        req->rq_task->tk_msg.rpc_proc->p_name,
                        rpcb->r_prog, rpcb->r_vers,
                        rpcb->r_netid, rpcb->r_addr);

        p = xdr_reserve_space(xdr, (RPCB_program_sz + RPCB_version_sz) << 2);
        *p++ = cpu_to_be32(rpcb->r_prog);
        *p = cpu_to_be32(rpcb->r_vers);

        encode_rpcb_string(xdr, rpcb->r_netid, RPCBIND_MAXNETIDLEN);
        encode_rpcb_string(xdr, rpcb->r_addr, RPCBIND_MAXUADDRLEN);
        encode_rpcb_string(xdr, rpcb->r_owner, RPCB_MAXOWNERLEN);
}

static int rpcb_dec_getaddr(struct rpc_rqst *req, struct xdr_stream *xdr,
                            struct rpcbind_args *rpcb)
{
        struct sockaddr_storage address;
        struct sockaddr *sap = (struct sockaddr *)&address;
        __be32 *p;
        u32 len;

        rpcb->r_port = 0;

        p = xdr_inline_decode(xdr, 4);
        if (unlikely(p == NULL))
                goto out_fail;
        len = be32_to_cpup(p);

        /*
         * If the returned universal address is a null string,
         * the requested RPC service was not registered.
         */
        if (len == 0) {
                dprintk("RPC: %5u RPCB reply: program not registered\n",
                                req->rq_task->tk_pid);
                return 0;
        }

        if (unlikely(len > RPCBIND_MAXUADDRLEN))
                goto out_fail;

        p = xdr_inline_decode(xdr, len);
        if (unlikely(p == NULL))
                goto out_fail;
        dprintk("RPC: %5u RPCB_%s reply: %s\n", req->rq_task->tk_pid,
                        req->rq_task->tk_msg.rpc_proc->p_name, (char *)p);

        if (rpc_uaddr2sockaddr(req->rq_xprt->xprt_net, (char *)p, len,
                                sap, sizeof(address)) == 0)
                goto out_fail;
        rpcb->r_port = rpc_get_port(sap);

        return 0;

out_fail:
        dprintk("RPC: %5u malformed RPCB_%s reply\n",
                        req->rq_task->tk_pid,
                        req->rq_task->tk_msg.rpc_proc->p_name);
        return -EIO;
}

/*
 * Not all rpcbind procedures described in RFC 1833 are implemented
 * since the Linux kernel RPC code requires only these.
 */

static struct rpc_procinfo rpcb_procedures2[] = {
        [RPCBPROC_SET] = {
                .p_proc         = RPCBPROC_SET,
                .p_encode       = (kxdreproc_t)rpcb_enc_mapping,
                .p_decode       = (kxdrdproc_t)rpcb_dec_set,
                .p_arglen       = RPCB_mappingargs_sz,
                .p_replen       = RPCB_setres_sz,
                .p_statidx      = RPCBPROC_SET,
                .p_timer        = 0,
                .p_name         = "SET",
        },

        [RPCBPROC_UNSET] = {
                .p_proc         = RPCBPROC_UNSET,
                .p_encode       = (kxdreproc_t)rpcb_enc_mapping,
                .p_decode       = (kxdrdproc_t)rpcb_dec_set,
                .p_arglen       = RPCB_mappingargs_sz,
                .p_replen       = RPCB_setres_sz,
                .p_statidx      = RPCBPROC_UNSET,
                .p_timer        = 0,
                .p_name         = "UNSET",
        },
        [RPCBPROC_GETPORT] = {
                .p_proc         = RPCBPROC_GETPORT,
                .p_encode       = (kxdreproc_t)rpcb_enc_mapping,
                .p_decode       = (kxdrdproc_t)rpcb_dec_getport,
                .p_arglen       = RPCB_mappingargs_sz,
                .p_replen       = RPCB_getportres_sz,
                .p_statidx      = RPCBPROC_GETPORT,
                .p_timer        = 0,
                .p_name         = "GETPORT",
        },
};

static struct rpc_procinfo rpcb_procedures3[] = {
        [RPCBPROC_SET] = {
                .p_proc         = RPCBPROC_SET,
                .p_encode       = (kxdreproc_t)rpcb_enc_getaddr,
                .p_decode       = (kxdrdproc_t)rpcb_dec_set,
                .p_arglen       = RPCB_getaddrargs_sz,
                .p_replen       = RPCB_setres_sz,
                .p_statidx      = RPCBPROC_SET,
                .p_timer        = 0,
                .p_name         = "SET",
        },
        [RPCBPROC_UNSET] = {
                .p_proc         = RPCBPROC_UNSET,
                .p_encode       = (kxdreproc_t)rpcb_enc_getaddr,
                .p_decode       = (kxdrdproc_t)rpcb_dec_set,
                .p_arglen       = RPCB_getaddrargs_sz,
                .p_replen       = RPCB_setres_sz,
                .p_statidx      = RPCBPROC_UNSET,
                .p_timer        = 0,
                .p_name         = "UNSET",
        },
        [RPCBPROC_GETADDR] = {
                .p_proc         = RPCBPROC_GETADDR,
                .p_encode       = (kxdreproc_t)rpcb_enc_getaddr,
                .p_decode       = (kxdrdproc_t)rpcb_dec_getaddr,
                .p_arglen       = RPCB_getaddrargs_sz,
                .p_replen       = RPCB_getaddrres_sz,
                .p_statidx      = RPCBPROC_GETADDR,
                .p_timer        = 0,
                .p_name         = "GETADDR",
        },
};

static struct rpc_procinfo rpcb_procedures4[] = {
        [RPCBPROC_SET] = {
                .p_proc         = RPCBPROC_SET,
                .p_encode       = (kxdreproc_t)rpcb_enc_getaddr,
                .p_decode       = (kxdrdproc_t)rpcb_dec_set,
                .p_arglen       = RPCB_getaddrargs_sz,
                .p_replen       = RPCB_setres_sz,
                .p_statidx      = RPCBPROC_SET,
                .p_timer        = 0,
                .p_name         = "SET",
        },
        [RPCBPROC_UNSET] = {
                .p_proc         = RPCBPROC_UNSET,
                .p_encode       = (kxdreproc_t)rpcb_enc_getaddr,
                .p_decode       = (kxdrdproc_t)rpcb_dec_set,
                .p_arglen       = RPCB_getaddrargs_sz,
                .p_replen       = RPCB_setres_sz,
                .p_statidx      = RPCBPROC_UNSET,
                .p_timer        = 0,
                .p_name         = "UNSET",
        },
        [RPCBPROC_GETADDR] = {
                .p_proc         = RPCBPROC_GETADDR,
                .p_encode       = (kxdreproc_t)rpcb_enc_getaddr,
                .p_decode       = (kxdrdproc_t)rpcb_dec_getaddr,
                .p_arglen       = RPCB_getaddrargs_sz,
                .p_replen       = RPCB_getaddrres_sz,
                .p_statidx      = RPCBPROC_GETADDR,
                .p_timer        = 0,
                .p_name         = "GETADDR",
        },
};

static const struct rpcb_info rpcb_next_version[] = {
        {
                .rpc_vers       = RPCBVERS_2,
                .rpc_proc       = &rpcb_procedures2[RPCBPROC_GETPORT],
        },
        {
                .rpc_proc       = NULL,
        },
};

static const struct rpcb_info rpcb_next_version6[] = {
        {
                .rpc_vers       = RPCBVERS_4,
                .rpc_proc       = &rpcb_procedures4[RPCBPROC_GETADDR],
        },
        {
                .rpc_vers       = RPCBVERS_3,
                .rpc_proc       = &rpcb_procedures3[RPCBPROC_GETADDR],
        },
        {
                .rpc_proc       = NULL,
        },
};

static const struct rpc_version rpcb_version2 = {
        .number         = RPCBVERS_2,
        .nrprocs        = ARRAY_SIZE(rpcb_procedures2),
        .procs          = rpcb_procedures2
};

static const struct rpc_version rpcb_version3 = {
        .number         = RPCBVERS_3,
        .nrprocs        = ARRAY_SIZE(rpcb_procedures3),
        .procs          = rpcb_procedures3
};

static const struct rpc_version rpcb_version4 = {
        .number         = RPCBVERS_4,
        .nrprocs        = ARRAY_SIZE(rpcb_procedures4),
        .procs          = rpcb_procedures4
};

static const struct rpc_version *rpcb_version[] = {
        NULL,
        NULL,
        &rpcb_version2,
        &rpcb_version3,
        &rpcb_version4
};

static struct rpc_stat rpcb_stats;

static const struct rpc_program rpcb_program = {
        .name           = "rpcbind",
        .number         = RPCBIND_PROGRAM,
        .nrvers         = ARRAY_SIZE(rpcb_version),
        .version        = rpcb_version,
        .stats          = &rpcb_stats,
};