/*
 * linux/fs/lockd/mon.c
 *
 * The kernel statd client.
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/types.h>
#include <linux/utsname.h>
#include <linux/kernel.h>
#include <linux/ktime.h>

#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/xprtsock.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>

#include <asm/unaligned.h>

#define NLMDBG_FACILITY         NLMDBG_MONITOR
#define NSM_PROGRAM             100024
#define NSM_VERSION             1

enum {
        NSMPROC_NULL,
        NSMPROC_STAT,
        NSMPROC_MON,
        NSMPROC_UNMON,
        NSMPROC_UNMON_ALL,
        NSMPROC_SIMU_CRASH,
        NSMPROC_NOTIFY,
};

struct nsm_args {
        struct nsm_private      *priv;
        u32                     prog;           /* RPC callback info */
        u32                     vers;
        u32                     proc;

        char                    *mon_name;
};

struct nsm_res {
        u32                     status;
        u32                     state;
};

static struct rpc_program       nsm_program;
static                          LIST_HEAD(nsm_handles);
static                          DEFINE_SPINLOCK(nsm_lock);

/*
 * Local NSM state
 */
u32     __read_mostly           nsm_local_state;
int     __read_mostly           nsm_use_hostnames;

static inline struct sockaddr *nsm_addr(const struct nsm_handle *nsm)
{
        return (struct sockaddr *)&nsm->sm_addr;
}

static struct rpc_clnt *nsm_create(void)
{
        struct sockaddr_in sin = {
                .sin_family             = AF_INET,
                .sin_addr.s_addr        = htonl(INADDR_LOOPBACK),
        };
        struct rpc_create_args args = {
                .protocol               = XPRT_TRANSPORT_UDP,
                .address                = (struct sockaddr *)&sin,
                .addrsize               = sizeof(sin),
                .servername             = "rpc.statd",
                .program                = &nsm_program,
                .version                = NSM_VERSION,
                .authflavor             = RPC_AUTH_NULL,
                .flags                  = RPC_CLNT_CREATE_NOPING,
        };

        return rpc_create(&args);
}

static int nsm_mon_unmon(struct nsm_handle *nsm, u32 proc, struct nsm_res *res)
{
        struct rpc_clnt *clnt;
        int             status;
        struct nsm_args args = {
                .priv           = &nsm->sm_priv,
                .prog           = NLM_PROGRAM,
                .vers           = 3,
                .proc           = NLMPROC_NSM_NOTIFY,
                .mon_name       = nsm->sm_mon_name,
        };
        struct rpc_message msg = {
                .rpc_argp       = &args,
                .rpc_resp       = res,
        };

        clnt = nsm_create();
        if (IS_ERR(clnt)) {
                status = PTR_ERR(clnt);
                dprintk("lockd: failed to create NSM upcall transport, "
                                "status=%d\n", status);
                goto out;
        }

        memset(res, 0, sizeof(*res));

        msg.rpc_proc = &clnt->cl_procinfo[proc];
        status = rpc_call_sync(clnt, &msg, 0);
        if (status < 0)
                dprintk("lockd: NSM upcall RPC failed, status=%d\n",
                                status);
        else
                status = 0;
        rpc_shutdown_client(clnt);
 out:
        return status;
}

/**
 * nsm_monitor - Notify a peer in case we reboot
 * @host: pointer to nlm_host of peer to notify
 *
 * If this peer is not already monitored, this function sends an
 * upcall to the local rpc.statd to record the name/address of
 * the peer to notify in case we reboot.
 *
 * Returns zero if the peer is monitored by the local rpc.statd;
 * otherwise a negative errno value is returned.
 */
int nsm_monitor(const struct nlm_host *host)
{
        struct nsm_handle *nsm = host->h_nsmhandle;
        struct nsm_res  res;
        int             status;

        dprintk("lockd: nsm_monitor(%s)\n", nsm->sm_name);

        if (nsm->sm_monitored)
                return 0;

        /*
         * Choose whether to record the caller_name or IP address of
         * this peer in the local rpc.statd's database.
         */
        nsm->sm_mon_name = nsm_use_hostnames ? nsm->sm_name : nsm->sm_addrbuf;

        status = nsm_mon_unmon(nsm, NSMPROC_MON, &res);
        if (unlikely(res.status != 0))
                status = -EIO;
        if (unlikely(status < 0)) {
                printk(KERN_NOTICE "lockd: cannot monitor %s\n", nsm->sm_name);
                return status;
        }

        nsm->sm_monitored = 1;
        if (unlikely(nsm_local_state != res.state)) {
                nsm_local_state = res.state;
                dprintk("lockd: NSM state changed to %d\n", nsm_local_state);
        }
        return 0;
}

/**
 * nsm_unmonitor - Unregister peer notification
 * @host: pointer to nlm_host of peer to stop monitoring
 *
 * If this peer is monitored, this function sends an upcall to
 * tell the local rpc.statd not to send this peer a notification
 * when we reboot.
 */
void nsm_unmonitor(const struct nlm_host *host)
{
        struct nsm_handle *nsm = host->h_nsmhandle;
        struct nsm_res  res;
        int status;

        if (atomic_read(&nsm->sm_count) == 1
         && nsm->sm_monitored && !nsm->sm_sticky) {
                dprintk("lockd: nsm_unmonitor(%s)\n", nsm->sm_name);

                status = nsm_mon_unmon(nsm, NSMPROC_UNMON, &res);
                if (res.status != 0)
                        status = -EIO;
                if (status < 0)
                        printk(KERN_NOTICE "lockd: cannot unmonitor %s\n",
                                        nsm->sm_name);
                else
                        nsm->sm_monitored = 0;
        }
}

static struct nsm_handle *nsm_lookup_hostname(const char *hostname,
                                              const size_t len)
{
        struct nsm_handle *nsm;

        list_for_each_entry(nsm, &nsm_handles, sm_link)
                if (strlen(nsm->sm_name) == len &&
                    memcmp(nsm->sm_name, hostname, len) == 0)
                        return nsm;
        return NULL;
}

static struct nsm_handle *nsm_lookup_addr(const struct sockaddr *sap)
{
        struct nsm_handle *nsm;

        list_for_each_entry(nsm, &nsm_handles, sm_link)
                if (rpc_cmp_addr(nsm_addr(nsm), sap))
                        return nsm;
        return NULL;
}

static struct nsm_handle *nsm_lookup_priv(const struct nsm_private *priv)
{
        struct nsm_handle *nsm;

        list_for_each_entry(nsm, &nsm_handles, sm_link)
                if (memcmp(nsm->sm_priv.data, priv->data,
                                        sizeof(priv->data)) == 0)
                        return nsm;
        return NULL;
}

/*
 * Construct a unique cookie to match this nsm_handle to this monitored
 * host.  It is passed to the local rpc.statd via NSMPROC_MON, and
 * returned via NLMPROC_SM_NOTIFY, in the "priv" field of these
 * requests.
 *
 * The NSM protocol requires that these cookies be unique while the
 * system is running.  We prefer a stronger requirement of making them
 * unique across reboots.  If user space bugs cause a stale cookie to
 * be sent to the kernel, it could cause the wrong host to lose its
 * lock state if cookies were not unique across reboots.
 *
 * The cookies are exposed only to local user space via loopback.  They
 * do not appear on the physical network.  If we want greater security
 * for some reason, nsm_init_private() could perform a one-way hash to
 * obscure the contents of the cookie.
 */
static void nsm_init_private(struct nsm_handle *nsm)
{
        u64 *p = (u64 *)&nsm->sm_priv.data;
        struct timespec ts;
        s64 ns;

        ktime_get_ts(&ts);
        ns = timespec_to_ns(&ts);
        put_unaligned(ns, p);
        put_unaligned((unsigned long)nsm, p + 1);
}

static struct nsm_handle *nsm_create_handle(const struct sockaddr *sap,
                                            const size_t salen,
                                            const char *hostname,
                                            const size_t hostname_len)
{
        struct nsm_handle *new;

        new = kzalloc(sizeof(*new) + hostname_len + 1, GFP_KERNEL);
        if (unlikely(new == NULL))
                return NULL;

        atomic_set(&new->sm_count, 1);
        new->sm_name = (char *)(new + 1);
        memcpy(nsm_addr(new), sap, salen);
        new->sm_addrlen = salen;
        nsm_init_private(new);

        if (rpc_ntop(nsm_addr(new), new->sm_addrbuf,
                                        sizeof(new->sm_addrbuf)) == 0)
                (void)snprintf(new->sm_addrbuf, sizeof(new->sm_addrbuf),
                                "unsupported address family");
        memcpy(new->sm_name, hostname, hostname_len);
        new->sm_name[hostname_len] = '\0';

        return new;
}

/**
 * nsm_get_handle - Find or create a cached nsm_handle
 * @sap: pointer to socket address of handle to find
 * @salen: length of socket address
 * @hostname: pointer to C string containing hostname to find
 * @hostname_len: length of C string
 *
 * Behavior is modulated by the global nsm_use_hostnames variable.
 *
 * Returns a cached nsm_handle after bumping its ref count, or
 * returns a fresh nsm_handle if a handle that matches @sap and/or
 * @hostname cannot be found in the handle cache.  Returns NULL if
 * an error occurs.
 */
struct nsm_handle *nsm_get_handle(const struct sockaddr *sap,
                                  const size_t salen, const char *hostname,
                                  const size_t hostname_len)
{
        struct nsm_handle *cached, *new = NULL;

        if (hostname && memchr(hostname, '/', hostname_len) != NULL) {
                if (printk_ratelimit()) {
                        printk(KERN_WARNING "Invalid hostname \"%.*s\" "
                                            "in NFS lock request\n",
                                (int)hostname_len, hostname);
                }
                return NULL;
        }

retry:
        spin_lock(&nsm_lock);

        if (nsm_use_hostnames && hostname != NULL)
                cached = nsm_lookup_hostname(hostname, hostname_len);
        else
                cached = nsm_lookup_addr(sap);

        if (cached != NULL) {
                atomic_inc(&cached->sm_count);
                spin_unlock(&nsm_lock);
                kfree(new);
                dprintk("lockd: found nsm_handle for %s (%s), "
                                "cnt %d\n", cached->sm_name,
                                cached->sm_addrbuf,
                                atomic_read(&cached->sm_count));
                return cached;
        }

        if (new != NULL) {
                list_add(&new->sm_link, &nsm_handles);
                spin_unlock(&nsm_lock);
                dprintk("lockd: created nsm_handle for %s (%s)\n",
                                new->sm_name, new->sm_addrbuf);
                return new;
        }

        spin_unlock(&nsm_lock);

        new = nsm_create_handle(sap, salen, hostname, hostname_len);
        if (unlikely(new == NULL))
                return NULL;
        goto retry;
}

/**
 * nsm_reboot_lookup - match NLMPROC_SM_NOTIFY arguments to an nsm_handle
 * @info: pointer to NLMPROC_SM_NOTIFY arguments
 *
 * Returns a matching nsm_handle if found in the nsm cache; the returned
 * nsm_handle's reference count is bumped and sm_monitored is cleared.
 * Otherwise returns NULL if some error occurred.
 */
struct nsm_handle *nsm_reboot_lookup(const struct nlm_reboot *info)
{
        struct nsm_handle *cached;

        spin_lock(&nsm_lock);

        cached = nsm_lookup_priv(&info->priv);
        if (unlikely(cached == NULL)) {
                spin_unlock(&nsm_lock);
                dprintk("lockd: never saw rebooted peer '%.*s' before\n",
                                info->len, info->mon);
                return cached;
        }

        atomic_inc(&cached->sm_count);
        spin_unlock(&nsm_lock);

        /*
         * During subsequent lock activity, force a fresh
         * notification to be set up for this host.
         */
        cached->sm_monitored = 0;

        dprintk("lockd: host %s (%s) rebooted, cnt %d\n",
                        cached->sm_name, cached->sm_addrbuf,
                        atomic_read(&cached->sm_count));
        return cached;
}

/**
 * nsm_release - Release an NSM handle
 * @nsm: pointer to handle to be released
 *
 */
void nsm_release(struct nsm_handle *nsm)
{
        if (atomic_dec_and_lock(&nsm->sm_count, &nsm_lock)) {
                list_del(&nsm->sm_link);
                spin_unlock(&nsm_lock);
                dprintk("lockd: destroyed nsm_handle for %s (%s)\n",
                                nsm->sm_name, nsm->sm_addrbuf);
                kfree(nsm);
        }
}

/*
 * XDR functions for NSM.
 *
 * See http://www.opengroup.org/ for details on the Network
 * Status Monitor wire protocol.
 */

static int encode_nsm_string(struct xdr_stream *xdr, const char *string)
{
        const u32 len = strlen(string);
        __be32 *p;

        if (unlikely(len > SM_MAXSTRLEN))
                return -EIO;
        p = xdr_reserve_space(xdr, sizeof(u32) + len);
        if (unlikely(p == NULL))
                return -EIO;
        xdr_encode_opaque(p, string, len);
        return 0;
}

/*
 * "mon_name" specifies the host to be monitored.
 */
static int encode_mon_name(struct xdr_stream *xdr, const struct nsm_args *argp)
{
        return encode_nsm_string(xdr, argp->mon_name);
}

/*
 * The "my_id" argument specifies the hostname and RPC procedure
 * to be called when the status manager receives notification
 * (via the NLMPROC_SM_NOTIFY call) that the state of host "mon_name"
 * has changed.
 */
static int encode_my_id(struct xdr_stream *xdr, const struct nsm_args *argp)
{
        int status;
        __be32 *p;

        status = encode_nsm_string(xdr, utsname()->nodename);
        if (unlikely(status != 0))
                return status;
        p = xdr_reserve_space(xdr, 3 * sizeof(u32));
        if (unlikely(p == NULL))
                return -EIO;
        *p++ = htonl(argp->prog);
        *p++ = htonl(argp->vers);
        *p++ = htonl(argp->proc);
        return 0;
}

/*
 * The "mon_id" argument specifies the non-private arguments
 * of an NSMPROC_MON or NSMPROC_UNMON call.
 */
static int encode_mon_id(struct xdr_stream *xdr, const struct nsm_args *argp)
{
        int status;

        status = encode_mon_name(xdr, argp);
        if (unlikely(status != 0))
                return status;
        return encode_my_id(xdr, argp);
}

/*
 * The "priv" argument may contain private information required
 * by the NSMPROC_MON call. This information will be supplied in the
 * NLMPROC_SM_NOTIFY call.
 */
static int encode_priv(struct xdr_stream *xdr, const struct nsm_args *argp)
{
        __be32 *p;

        p = xdr_reserve_space(xdr, SM_PRIV_SIZE);
        if (unlikely(p == NULL))
                return -EIO;
        xdr_encode_opaque_fixed(p, argp->priv->data, SM_PRIV_SIZE);
        return 0;
}

static int xdr_enc_mon(struct rpc_rqst *req, __be32 *p,
                       const struct nsm_args *argp)
{
        struct xdr_stream xdr;
        int status;

        xdr_init_encode(&xdr, &req->rq_snd_buf, p);
        status = encode_mon_id(&xdr, argp);
        if (unlikely(status))
                return status;
        return encode_priv(&xdr, argp);
}

static int xdr_enc_unmon(struct rpc_rqst *req, __be32 *p,
                         const struct nsm_args *argp)
{
        struct xdr_stream xdr;

        xdr_init_encode(&xdr, &req->rq_snd_buf, p);
        return encode_mon_id(&xdr, argp);
}

static int xdr_dec_stat_res(struct rpc_rqst *rqstp, __be32 *p,
                            struct nsm_res *resp)
{
        struct xdr_stream xdr;

        xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
        p = xdr_inline_decode(&xdr, 2 * sizeof(u32));
        if (unlikely(p == NULL))
                return -EIO;
        resp->status = ntohl(*p++);
        resp->state = ntohl(*p);

        dprintk("lockd: xdr_dec_stat_res status %d state %d\n",
                        resp->status, resp->state);
        return 0;
}

static int xdr_dec_stat(struct rpc_rqst *rqstp, __be32 *p,
                        struct nsm_res *resp)
{
        struct xdr_stream xdr;

        xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
        p = xdr_inline_decode(&xdr, sizeof(u32));
        if (unlikely(p == NULL))
                return -EIO;
        resp->state = ntohl(*p);

        dprintk("lockd: xdr_dec_stat state %d\n", resp->state);
        return 0;
}

#define SM_my_name_sz   (1+XDR_QUADLEN(SM_MAXSTRLEN))
#define SM_my_id_sz     (SM_my_name_sz+3)
#define SM_mon_name_sz  (1+XDR_QUADLEN(SM_MAXSTRLEN))
#define SM_mon_id_sz    (SM_mon_name_sz+SM_my_id_sz)
#define SM_priv_sz      (XDR_QUADLEN(SM_PRIV_SIZE))
#define SM_mon_sz       (SM_mon_id_sz+SM_priv_sz)
#define SM_monres_sz    2
#define SM_unmonres_sz  1

static struct rpc_procinfo      nsm_procedures[] = {
[NSMPROC_MON] = {
                .p_proc         = NSMPROC_MON,
                .p_encode       = (kxdrproc_t)xdr_enc_mon,
                .p_decode       = (kxdrproc_t)xdr_dec_stat_res,
                .p_arglen       = SM_mon_sz,
                .p_replen       = SM_monres_sz,
                .p_statidx      = NSMPROC_MON,
                .p_name         = "MONITOR",
        },
[NSMPROC_UNMON] = {
                .p_proc         = NSMPROC_UNMON,
                .p_encode       = (kxdrproc_t)xdr_enc_unmon,
                .p_decode       = (kxdrproc_t)xdr_dec_stat,
                .p_arglen       = SM_mon_id_sz,
                .p_replen       = SM_unmonres_sz,
                .p_statidx      = NSMPROC_UNMON,
                .p_name         = "UNMONITOR",
        },
};

static struct rpc_version       nsm_version1 = {
                .number         = 1,
                .nrprocs        = ARRAY_SIZE(nsm_procedures),
                .procs          = nsm_procedures
};

static struct rpc_version *     nsm_version[] = {
        [1] = &nsm_version1,
};

static struct rpc_stat          nsm_stats;

static struct rpc_program       nsm_program = {
                .name           = "statd",
                .number         = NSM_PROGRAM,
                .nrvers         = ARRAY_SIZE(nsm_version),
                .version        = nsm_version,
                .stats          = &nsm_stats
};