// SPDX-License-Identifier: GPL-2.0
/*
 * 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/sched/signal.h>
#include <linux/sunrpc/svc.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/nfs_fs.h>
#include <linux/errno.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"
#include "netns.h"

#define NFSDBG_FACILITY NFSDBG_CALLBACK

struct nfs_callback_data {
        unsigned int users;
        struct svc_serv *serv;
};

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;

static int nfs4_callback_up_net(struct svc_serv *serv, struct net *net)
{
        const struct cred *cred = current_cred();
        int ret;
        struct nfs_net *nn = net_generic(net, nfs_net_id);

        ret = svc_create_xprt(serv, "tcp", net, PF_INET,
                                nfs_callback_set_tcpport, SVC_SOCK_ANONYMOUS,
                                cred);
        if (ret <= 0)
                goto out_err;
        nn->nfs_callback_tcpport = ret;
        dprintk("NFS: Callback listener port = %u (af %u, net %x)\n",
                nn->nfs_callback_tcpport, PF_INET, net->ns.inum);

        ret = svc_create_xprt(serv, "tcp", net, PF_INET6,
                                nfs_callback_set_tcpport, SVC_SOCK_ANONYMOUS,
                                cred);
        if (ret > 0) {
                nn->nfs_callback_tcpport6 = ret;
                dprintk("NFS: Callback listener port = %u (af %u, net %x)\n",
                        nn->nfs_callback_tcpport6, PF_INET6, net->ns.inum);
        } else if (ret != -EAFNOSUPPORT)
                goto out_err;
        return 0;

out_err:
        return (ret) ? ret : -ENOMEM;
}

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

        set_freezable();

        while (!kthread_freezable_should_stop(NULL)) {

                if (signal_pending(current))
                        flush_signals(current);
                /*
                 * Listen for a request on the socket
                 */
                err = svc_recv(rqstp, MAX_SCHEDULE_TIMEOUT);
                if (err == -EAGAIN || err == -EINTR)
                        continue;
                svc_process(rqstp);
        }
        svc_exit_thread(rqstp);
        module_put_and_exit(0);
        return 0;
}

#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_freezable_should_stop(NULL)) {

                if (signal_pending(current))
                        flush_signals(current);

                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);
                        finish_wait(&serv->sv_cb_waitq, &wq);
                        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);
                        if (!kthread_should_stop())
                                schedule();
                        finish_wait(&serv->sv_cb_waitq, &wq);
                }
        }
        svc_exit_thread(rqstp);
        module_put_and_exit(0);
        return 0;
}

static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
                struct svc_serv *serv)
{
        if (minorversion)
                /*
                 * Save the svc_serv in the transport so that it can
                 * be referenced when the session backchannel is initialized
                 */
                xprt->bc_serv = serv;
}
#else
static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
                struct svc_serv *serv)
{
}
#endif /* CONFIG_NFS_V4_1 */

static int nfs_callback_start_svc(int minorversion, struct rpc_xprt *xprt,
                                  struct svc_serv *serv)
{
        int nrservs = nfs_callback_nr_threads;
        int ret;

        nfs_callback_bc_serv(minorversion, xprt, serv);

        if (nrservs < NFS4_MIN_NR_CALLBACK_THREADS)
                nrservs = NFS4_MIN_NR_CALLBACK_THREADS;

        if (serv->sv_nrthreads-1 == nrservs)
                return 0;

        ret = serv->sv_ops->svo_setup(serv, NULL, nrservs);
        if (ret) {
                serv->sv_ops->svo_setup(serv, NULL, 0);
                return ret;
        }
        dprintk("nfs_callback_up: service started\n");
        return 0;
}

static void nfs_callback_down_net(u32 minorversion, struct svc_serv *serv, struct net *net)
{
        struct nfs_net *nn = net_generic(net, nfs_net_id);

        if (--nn->cb_users[minorversion])
                return;

        dprintk("NFS: destroy per-net callback data; net=%x\n", net->ns.inum);
        svc_shutdown_net(serv, net);
}

static int nfs_callback_up_net(int minorversion, struct svc_serv *serv,
                               struct net *net, struct rpc_xprt *xprt)
{
        struct nfs_net *nn = net_generic(net, nfs_net_id);
        int ret;

        if (nn->cb_users[minorversion]++)
                return 0;

        dprintk("NFS: create per-net callback data; net=%x\n", net->ns.inum);

        ret = svc_bind(serv, net);
        if (ret < 0) {
                printk(KERN_WARNING "NFS: bind callback service failed\n");
                goto err_bind;
        }

        ret = 0;
        if (!IS_ENABLED(CONFIG_NFS_V4_1) || minorversion == 0)
                ret = nfs4_callback_up_net(serv, net);
        else if (xprt->ops->bc_setup)
                set_bc_enabled(serv);
        else
                ret = -EPROTONOSUPPORT;

        if (ret < 0) {
                printk(KERN_ERR "NFS: callback service start failed\n");
                goto err_socks;
        }
        return 0;

err_socks:
        svc_rpcb_cleanup(serv, net);
err_bind:
        nn->cb_users[minorversion]--;
        dprintk("NFS: Couldn't create callback socket: err = %d; "
                        "net = %x\n", ret, net->ns.inum);
        return ret;
}

static const struct svc_serv_ops nfs40_cb_sv_ops = {
        .svo_function           = nfs4_callback_svc,
        .svo_enqueue_xprt       = svc_xprt_do_enqueue,
        .svo_setup              = svc_set_num_threads_sync,
        .svo_module             = THIS_MODULE,
};
#if defined(CONFIG_NFS_V4_1)
static const struct svc_serv_ops nfs41_cb_sv_ops = {
        .svo_function           = nfs41_callback_svc,
        .svo_enqueue_xprt       = svc_xprt_do_enqueue,
        .svo_setup              = svc_set_num_threads_sync,
        .svo_module             = THIS_MODULE,
};

static const struct svc_serv_ops *nfs4_cb_sv_ops[] = {
        [0] = &nfs40_cb_sv_ops,
        [1] = &nfs41_cb_sv_ops,
};
#else
static const struct svc_serv_ops *nfs4_cb_sv_ops[] = {
        [0] = &nfs40_cb_sv_ops,
        [1] = NULL,
};
#endif

static struct svc_serv *nfs_callback_create_svc(int minorversion)
{
        struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
        const struct svc_serv_ops *sv_ops;
        struct svc_serv *serv;

        /*
         * Check whether we're already up and running.
         */
        if (cb_info->serv) {
                /*
                 * Note: increase service usage, because later in case of error
                 * svc_destroy() will be called.
                 */
                svc_get(cb_info->serv);
                return cb_info->serv;
        }

        switch (minorversion) {
        case 0:
                sv_ops = nfs4_cb_sv_ops[0];
                break;
        default:
                sv_ops = nfs4_cb_sv_ops[1];
        }

        if (sv_ops == NULL)
                return ERR_PTR(-ENOTSUPP);

        /*
         * Sanity check: if there's no task,
         * we should be the first user ...
         */
        if (cb_info->users)
                printk(KERN_WARNING "nfs_callback_create_svc: no kthread, %d users??\n",
                        cb_info->users);

        serv = svc_create_pooled(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, sv_ops);
        if (!serv) {
                printk(KERN_ERR "nfs_callback_create_svc: create service failed\n");
                return ERR_PTR(-ENOMEM);
        }
        cb_info->serv = serv;
        /* As there is only one thread we need to over-ride the
         * default maximum of 80 connections
         */
        serv->sv_maxconn = 1024;
        dprintk("nfs_callback_create_svc: service created\n");
        return serv;
}

/*
 * 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;
        struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
        int ret;
        struct net *net = xprt->xprt_net;

        mutex_lock(&nfs_callback_mutex);

        serv = nfs_callback_create_svc(minorversion);
        if (IS_ERR(serv)) {
                ret = PTR_ERR(serv);
                goto err_create;
        }

        ret = nfs_callback_up_net(minorversion, serv, net, xprt);
        if (ret < 0)
                goto err_net;

        ret = nfs_callback_start_svc(minorversion, xprt, serv);
        if (ret < 0)
                goto err_start;

        cb_info->users++;
        /*
         * 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.
         */
err_net:
        if (!cb_info->users)
                cb_info->serv = NULL;
        svc_destroy(serv);
err_create:
        mutex_unlock(&nfs_callback_mutex);
        return ret;

err_start:
        nfs_callback_down_net(minorversion, serv, net);
        dprintk("NFS: Couldn't create server thread; err = %d\n", ret);
        goto err_net;
}

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

        mutex_lock(&nfs_callback_mutex);
        serv = cb_info->serv;
        nfs_callback_down_net(minorversion, serv, net);
        cb_info->users--;
        if (cb_info->users == 0) {
                svc_get(serv);
                serv->sv_ops->svo_setup(serv, NULL, 0);
                svc_destroy(serv);
                dprintk("nfs_callback_down: service destroyed\n");
                cb_info->serv = 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)
{
        char *p = rqstp->rq_cred.cr_principal;

        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;

        /*
         * Did we get the acceptor from userland during the SETCLIENID
         * negotiation?
         */
        if (clp->cl_acceptor)
                return !strcmp(p, clp->cl_acceptor);

        /*
         * Otherwise try to verify it using the cl_hostname. Note that this
         * doesn't work if a non-canonical hostname was used in the devname.
         */

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

        if (memcmp(p, "nfs@", 4) != 0)
                return 0;
        p += 4;
        if (strcmp(p, clp->cl_hostname) != 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. Deny 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_DENIED;
                break;
        case RPC_AUTH_GSS:
                /* No RPC_AUTH_GSS support yet in NFSv4.1 */
                 if (svc_is_backchannel(rqstp))
                        return SVC_DENIED;
        }
        return SVC_OK;
}

/*
 * Define NFS4 callback program
 */
static const 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,
        .pg_init_request = svc_generic_init_request,
        .pg_rpcbind_set = svc_generic_rpcbind_set,
};