/*
 * linux/fs/nfs/callback.c
 *
 * Copyright (C) 2004 Trond Myklebust
 *
 * NFSv4 callback handling
 */

#include <linux/completion.h>
#include <linux/ip.h>
#include <linux/module.h>
#include <linux/sunrpc/svc.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/nfs_fs.h>
#include <linux/mutex.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/sunrpc/svcauth_gss.h>
#include <linux/sunrpc/bc_xprt.h>

#include <net/inet_sock.h>

#include "nfs4_fs.h"
#include "callback.h"
#include "internal.h"

#define NFSDBG_FACILITY NFSDBG_CALLBACK

struct nfs_callback_data {
        unsigned int users;
        struct svc_serv *serv;
        struct svc_rqst *rqst;
        struct task_struct *task;
};

static struct nfs_callback_data nfs_callback_info[NFS4_MAX_MINOR_VERSION + 1];
static DEFINE_MUTEX(nfs_callback_mutex);
static struct svc_program nfs4_callback_program;

unsigned int nfs_callback_set_tcpport;
unsigned short nfs_callback_tcpport;
unsigned short nfs_callback_tcpport6;
#define NFS_CALLBACK_MAXPORTNR (65535U)

static int param_set_portnr(const char *val, const struct kernel_param *kp)
{
        unsigned long num;
        int ret;

        if (!val)
                return -EINVAL;
        ret = strict_strtoul(val, 0, &num);
        if (ret == -EINVAL || num > NFS_CALLBACK_MAXPORTNR)
                return -EINVAL;
        *((unsigned int *)kp->arg) = num;
        return 0;
}
static struct kernel_param_ops param_ops_portnr = {
        .set = param_set_portnr,
        .get = param_get_uint,
};
#define param_check_portnr(name, p) __param_check(name, p, unsigned int);

module_param_named(callback_tcpport, nfs_callback_set_tcpport, portnr, 0644);

/*
 * This is the NFSv4 callback kernel thread.
 */
static int
nfs4_callback_svc(void *vrqstp)
{
        int err, preverr = 0;
        struct svc_rqst *rqstp = vrqstp;

        set_freezable();

        while (!kthread_should_stop()) {
                /*
                 * Listen for a request on the socket
                 */
                err = svc_recv(rqstp, MAX_SCHEDULE_TIMEOUT);
                if (err == -EAGAIN || err == -EINTR) {
                        preverr = err;
                        continue;
                }
                if (err < 0) {
                        if (err != preverr) {
                                printk(KERN_WARNING "%s: unexpected error "
                                        "from svc_recv (%d)\n", __func__, err);
                                preverr = err;
                        }
                        schedule_timeout_uninterruptible(HZ);
                        continue;
                }
                preverr = err;
                svc_process(rqstp);
        }
        return 0;
}

/*
 * Prepare to bring up the NFSv4 callback service
 */
struct svc_rqst *
nfs4_callback_up(struct svc_serv *serv)
{
        int ret;

        ret = svc_create_xprt(serv, "tcp", &init_net, PF_INET,
                                nfs_callback_set_tcpport, SVC_SOCK_ANONYMOUS);
        if (ret <= 0)
                goto out_err;
        nfs_callback_tcpport = ret;
        dprintk("NFS: Callback listener port = %u (af %u)\n",
                        nfs_callback_tcpport, PF_INET);

        ret = svc_create_xprt(serv, "tcp", &init_net, PF_INET6,
                                nfs_callback_set_tcpport, SVC_SOCK_ANONYMOUS);
        if (ret > 0) {
                nfs_callback_tcpport6 = ret;
                dprintk("NFS: Callback listener port = %u (af %u)\n",
                                nfs_callback_tcpport6, PF_INET6);
        } else if (ret == -EAFNOSUPPORT)
                ret = 0;
        else
                goto out_err;

        return svc_prepare_thread(serv, &serv->sv_pools[0]);

out_err:
        if (ret == 0)
                ret = -ENOMEM;
        return ERR_PTR(ret);
}

#if defined(CONFIG_NFS_V4_1)
/*
 * The callback service for NFSv4.1 callbacks
 */
static int
nfs41_callback_svc(void *vrqstp)
{
        struct svc_rqst *rqstp = vrqstp;
        struct svc_serv *serv = rqstp->rq_server;
        struct rpc_rqst *req;
        int error;
        DEFINE_WAIT(wq);

        set_freezable();

        while (!kthread_should_stop()) {
                prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE);
                spin_lock_bh(&serv->sv_cb_lock);
                if (!list_empty(&serv->sv_cb_list)) {
                        req = list_first_entry(&serv->sv_cb_list,
                                        struct rpc_rqst, rq_bc_list);
                        list_del(&req->rq_bc_list);
                        spin_unlock_bh(&serv->sv_cb_lock);
                        dprintk("Invoking bc_svc_process()\n");
                        error = bc_svc_process(serv, req, rqstp);
                        dprintk("bc_svc_process() returned w/ error code= %d\n",
                                error);
                } else {
                        spin_unlock_bh(&serv->sv_cb_lock);
                        schedule();
                }
                finish_wait(&serv->sv_cb_waitq, &wq);
        }
        return 0;
}

/*
 * Bring up the NFSv4.1 callback service
 */
struct svc_rqst *
nfs41_callback_up(struct svc_serv *serv, struct rpc_xprt *xprt)
{
        struct svc_rqst *rqstp;
        int ret;

        /*
         * Create an svc_sock for the back channel service that shares the
         * fore channel connection.
         * Returns the input port (0) and sets the svc_serv bc_xprt on success
         */
        ret = svc_create_xprt(serv, "tcp-bc", &init_net, PF_INET, 0,
                              SVC_SOCK_ANONYMOUS);
        if (ret < 0) {
                rqstp = ERR_PTR(ret);
                goto out;
        }

        /*
         * Save the svc_serv in the transport so that it can
         * be referenced when the session backchannel is initialized
         */
        xprt->bc_serv = serv;

        INIT_LIST_HEAD(&serv->sv_cb_list);
        spin_lock_init(&serv->sv_cb_lock);
        init_waitqueue_head(&serv->sv_cb_waitq);
        rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]);
        if (IS_ERR(rqstp)) {
                svc_xprt_put(serv->sv_bc_xprt);
                serv->sv_bc_xprt = NULL;
        }
out:
        dprintk("--> %s return %ld\n", __func__,
                IS_ERR(rqstp) ? PTR_ERR(rqstp) : 0);
        return rqstp;
}

static inline int nfs_minorversion_callback_svc_setup(u32 minorversion,
                struct svc_serv *serv, struct rpc_xprt *xprt,
                struct svc_rqst **rqstpp, int (**callback_svc)(void *vrqstp))
{
        if (minorversion) {
                *rqstpp = nfs41_callback_up(serv, xprt);
                *callback_svc = nfs41_callback_svc;
        }
        return minorversion;
}

static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
                struct nfs_callback_data *cb_info)
{
        if (minorversion)
                xprt->bc_serv = cb_info->serv;
}
#else
static inline int nfs_minorversion_callback_svc_setup(u32 minorversion,
                struct svc_serv *serv, struct rpc_xprt *xprt,
                struct svc_rqst **rqstpp, int (**callback_svc)(void *vrqstp))
{
        return 0;
}

static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
                struct nfs_callback_data *cb_info)
{
}
#endif /* CONFIG_NFS_V4_1 */

/*
 * Bring up the callback thread if it is not already up.
 */
int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt)
{
        struct svc_serv *serv = NULL;
        struct svc_rqst *rqstp;
        int (*callback_svc)(void *vrqstp);
        struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
        char svc_name[12];
        int ret = 0;
        int minorversion_setup;

        mutex_lock(&nfs_callback_mutex);
        if (cb_info->users++ || cb_info->task != NULL) {
                nfs_callback_bc_serv(minorversion, xprt, cb_info);
                goto out;
        }
        serv = svc_create(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, NULL);
        if (!serv) {
                ret = -ENOMEM;
                goto out_err;
        }

        minorversion_setup =  nfs_minorversion_callback_svc_setup(minorversion,
                                        serv, xprt, &rqstp, &callback_svc);
        if (!minorversion_setup) {
                /* v4.0 callback setup */
                rqstp = nfs4_callback_up(serv);
                callback_svc = nfs4_callback_svc;
        }

        if (IS_ERR(rqstp)) {
                ret = PTR_ERR(rqstp);
                goto out_err;
        }

        svc_sock_update_bufs(serv);

        sprintf(svc_name, "nfsv4.%u-svc", minorversion);
        cb_info->serv = serv;
        cb_info->rqst = rqstp;
        cb_info->task = kthread_run(callback_svc, cb_info->rqst, svc_name);
        if (IS_ERR(cb_info->task)) {
                ret = PTR_ERR(cb_info->task);
                svc_exit_thread(cb_info->rqst);
                cb_info->rqst = NULL;
                cb_info->task = NULL;
                goto out_err;
        }
out:
        /*
         * svc_create creates the svc_serv with sv_nrthreads == 1, and then
         * svc_prepare_thread increments that. So we need to call svc_destroy
         * on both success and failure so that the refcount is 1 when the
         * thread exits.
         */
        if (serv)
                svc_destroy(serv);
        mutex_unlock(&nfs_callback_mutex);
        return ret;
out_err:
        dprintk("NFS: Couldn't create callback socket or server thread; "
                "err = %d\n", ret);
        cb_info->users--;
        goto out;
}

/*
 * Kill the callback thread if it's no longer being used.
 */
void nfs_callback_down(int minorversion)
{
        struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];

        mutex_lock(&nfs_callback_mutex);
        cb_info->users--;
        if (cb_info->users == 0 && cb_info->task != NULL) {
                kthread_stop(cb_info->task);
                svc_exit_thread(cb_info->rqst);
                cb_info->serv = NULL;
                cb_info->rqst = NULL;
                cb_info->task = NULL;
        }
        mutex_unlock(&nfs_callback_mutex);
}

/* Boolean check of RPC_AUTH_GSS principal */
int
check_gss_callback_principal(struct nfs_client *clp, struct svc_rqst *rqstp)
{
        struct rpc_clnt *r = clp->cl_rpcclient;
        char *p = svc_gss_principal(rqstp);

        if (rqstp->rq_authop->flavour != RPC_AUTH_GSS)
                return 1;

        /* No RPC_AUTH_GSS on NFSv4.1 back channel yet */
        if (clp->cl_minorversion != 0)
                return 0;
        /*
         * It might just be a normal user principal, in which case
         * userspace won't bother to tell us the name at all.
         */
        if (p == NULL)
                return 0;

        /* Expect a GSS_C_NT_HOSTBASED_NAME like "nfs@serverhostname" */

        if (memcmp(p, "nfs@", 4) != 0)
                return 0;
        p += 4;
        if (strcmp(p, r->cl_server) != 0)
                return 0;
        return 1;
}

/*
 * pg_authenticate method for nfsv4 callback threads.
 *
 * The authflavor has been negotiated, so an incorrect flavor is a server
 * bug. Drop packets with incorrect authflavor.
 *
 * All other checking done after NFS decoding where the nfs_client can be
 * found in nfs4_callback_compound
 */
static int nfs_callback_authenticate(struct svc_rqst *rqstp)
{
        switch (rqstp->rq_authop->flavour) {
        case RPC_AUTH_NULL:
                if (rqstp->rq_proc != CB_NULL)
                        return SVC_DROP;
                break;
        case RPC_AUTH_GSS:
                /* No RPC_AUTH_GSS support yet in NFSv4.1 */
                 if (svc_is_backchannel(rqstp))
                        return SVC_DROP;
        }
        return SVC_OK;
}

/*
 * Define NFS4 callback program
 */
static struct svc_version *nfs4_callback_version[] = {
        [1] = &nfs4_callback_version1,
        [4] = &nfs4_callback_version4,
};

static struct svc_stat nfs4_callback_stats;

static struct svc_program nfs4_callback_program = {
        .pg_prog = NFS4_CALLBACK,                       /* RPC service number */
        .pg_nvers = ARRAY_SIZE(nfs4_callback_version),  /* Number of entries */
        .pg_vers = nfs4_callback_version,               /* version table */
        .pg_name = "NFSv4 callback",                    /* service name */
        .pg_class = "nfs",                              /* authentication class */
        .pg_stats = &nfs4_callback_stats,
        .pg_authenticate = nfs_callback_authenticate,
};