/*
 * Modifications for Lustre
 *
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 *
 * Copyright (c) 2012, 2014, Intel Corporation.
 *
 * Author: Eric Mei <ericm@clusterfs.com>
 */

/*
 * Neil Brown <neilb@cse.unsw.edu.au>
 * J. Bruce Fields <bfields@umich.edu>
 * Andy Adamson <andros@umich.edu>
 * Dug Song <dugsong@monkey.org>
 *
 * RPCSEC_GSS server authentication.
 * This implements RPCSEC_GSS as defined in rfc2203 (rpcsec_gss) and rfc2078
 * (gssapi)
 *
 * The RPCSEC_GSS involves three stages:
 *  1/ context creation
 *  2/ data exchange
 *  3/ context destruction
 *
 * Context creation is handled largely by upcalls to user-space.
 *  In particular, GSS_Accept_sec_context is handled by an upcall
 * Data exchange is handled entirely within the kernel
 *  In particular, GSS_GetMIC, GSS_VerifyMIC, GSS_Seal, GSS_Unseal are in-kernel.
 * Context destruction is handled in-kernel
 *  GSS_Delete_sec_context is in-kernel
 *
 * Context creation is initiated by a RPCSEC_GSS_INIT request arriving.
 * The context handle and gss_token are used as a key into the rpcsec_init cache.
 * The content of this cache includes some of the outputs of GSS_Accept_sec_context,
 * being major_status, minor_status, context_handle, reply_token.
 * These are sent back to the client.
 * Sequence window management is handled by the kernel.  The window size if currently
 * a compile time constant.
 *
 * When user-space is happy that a context is established, it places an entry
 * in the rpcsec_context cache. The key for this cache is the context_handle.
 * The content includes:
 *   uid/gidlist - for determining access rights
 *   mechanism type
 *   mechanism specific information, such as a key
 *
 */

#define DEBUG_SUBSYSTEM S_SEC
#include <linux/types.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/sunrpc/cache.h>
#include <net/sock.h>

#include <obd.h>
#include <obd_class.h>
#include <obd_support.h>
#include <lustre_import.h>
#include <lustre_net.h>
#include <lustre_nodemap.h>
#include <lustre_sec.h>
#include <libcfs/linux/linux-hash.h>

#include "gss_err.h"
#include "gss_internal.h"
#include "gss_api.h"
#include "gss_crypto.h"

#define GSS_SVC_UPCALL_TIMEOUT  (20)

static DEFINE_SPINLOCK(__ctx_index_lock);
static __u64 __ctx_index;

unsigned int krb5_allow_old_client_csum;

__u64 gss_get_next_ctx_index(void)
{
	__u64 idx;

	spin_lock(&__ctx_index_lock);
	idx = __ctx_index++;
	spin_unlock(&__ctx_index_lock);

	return idx;
}

static inline unsigned long hash_mem(char *buf, int length, int bits)
{
	unsigned long hash = 0;
	unsigned long l = 0;
	int len = 0;
	unsigned char c;

	do {
		if (len == length) {
			c = (char) len;
			len = -1;
		} else
			c = *buf++;

		l = (l << 8) | c;
		len++;

		if ((len & (BITS_PER_LONG/8-1)) == 0)
			hash = cfs_hash_long(hash^l, BITS_PER_LONG);
	} while (len);

	return hash >> (BITS_PER_LONG - bits);
}

/****************************************
 * rpc sec init (rsi) cache *
 ****************************************/

#define RSI_HASHBITS    (6)
#define RSI_HASHMAX     (1 << RSI_HASHBITS)
#define RSI_HASHMASK    (RSI_HASHMAX - 1)

struct rsi {
	struct cache_head       h;
	__u32                   lustre_svc;
	lnet_nid_t		nid4; /* FIXME Support larger NID */
	char			nm_name[LUSTRE_NODEMAP_NAME_LENGTH + 1];
	wait_queue_head_t       waitq;
	rawobj_t                in_handle, in_token;
	rawobj_t                out_handle, out_token;
	int                     major_status, minor_status;
#ifdef HAVE_CACHE_HASH_SPINLOCK
	struct rcu_head		rcu_head;
#endif
};

#ifdef HAVE_CACHE_HEAD_HLIST
static struct hlist_head rsi_table[RSI_HASHMAX];
#else
static struct cache_head *rsi_table[RSI_HASHMAX];
#endif
static struct cache_detail rsi_cache;
static struct rsi *rsi_update(struct rsi *new, struct rsi *old);
static struct rsi *rsi_lookup(struct rsi *item);

#ifdef HAVE_CACHE_DETAIL_WRITERS
static inline int channel_users(struct cache_detail *cd)
{
	return atomic_read(&cd->writers);
}
#else
static inline int channel_users(struct cache_detail *cd)
{
	return atomic_read(&cd->readers);
}
#endif

static inline int rsi_hash(struct rsi *item)
{
        return hash_mem((char *)item->in_handle.data, item->in_handle.len,
                        RSI_HASHBITS) ^
               hash_mem((char *)item->in_token.data, item->in_token.len,
                        RSI_HASHBITS);
}

static inline int __rsi_match(struct rsi *item, struct rsi *tmp)
{
        return (rawobj_equal(&item->in_handle, &tmp->in_handle) &&
                rawobj_equal(&item->in_token, &tmp->in_token));
}

static void rsi_free(struct rsi *rsi)
{
        rawobj_free(&rsi->in_handle);
        rawobj_free(&rsi->in_token);
        rawobj_free(&rsi->out_handle);
        rawobj_free(&rsi->out_token);
}

/* See handle_channel_req() userspace for where the upcall data is read */
static void rsi_request(struct cache_detail *cd,
                        struct cache_head *h,
                        char **bpp, int *blen)
{
	struct rsi *rsi = container_of(h, struct rsi, h);
	__u64 index = 0;

	/* if in_handle is null, provide kernel suggestion */
	if (rsi->in_handle.len == 0)
		index = gss_get_next_ctx_index();

	qword_addhex(bpp, blen, (char *) &rsi->lustre_svc,
			sizeof(rsi->lustre_svc));
	qword_addhex(bpp, blen, (char *) &rsi->nid4, sizeof(rsi->nid4));
	qword_addhex(bpp, blen, (char *) &index, sizeof(index));
	qword_addhex(bpp, blen, (char *) rsi->nm_name,
		     strlen(rsi->nm_name) + 1);
	qword_addhex(bpp, blen, rsi->in_handle.data, rsi->in_handle.len);
	qword_addhex(bpp, blen, rsi->in_token.data, rsi->in_token.len);
	(*bpp)[-1] = '\n';
}

static inline void __rsi_init(struct rsi *new, struct rsi *item)
{
	new->out_handle = RAWOBJ_EMPTY;
	new->out_token = RAWOBJ_EMPTY;

	new->in_handle = item->in_handle;
	item->in_handle = RAWOBJ_EMPTY;
	new->in_token = item->in_token;
	item->in_token = RAWOBJ_EMPTY;

	new->lustre_svc = item->lustre_svc;
	new->nid4 = item->nid4;
	memcpy(new->nm_name, item->nm_name, sizeof(item->nm_name));
	init_waitqueue_head(&new->waitq);
}

static inline void __rsi_update(struct rsi *new, struct rsi *item)
{
        LASSERT(new->out_handle.len == 0);
        LASSERT(new->out_token.len == 0);

        new->out_handle = item->out_handle;
        item->out_handle = RAWOBJ_EMPTY;
        new->out_token = item->out_token;
        item->out_token = RAWOBJ_EMPTY;

        new->major_status = item->major_status;
        new->minor_status = item->minor_status;
}

#ifdef HAVE_CACHE_HASH_SPINLOCK
static void rsi_free_rcu(struct rcu_head *head)
{
	struct rsi *rsi = container_of(head, struct rsi, rcu_head);

#ifdef HAVE_CACHE_HEAD_HLIST
	LASSERT(hlist_unhashed(&rsi->h.cache_list));
#else
	LASSERT(rsi->h.next == NULL);
#endif
	rsi_free(rsi);
	OBD_FREE_PTR(rsi);
}

static void rsi_put(struct kref *ref)
{
	struct rsi *rsi = container_of(ref, struct rsi, h.ref);

	call_rcu(&rsi->rcu_head, rsi_free_rcu);
}
#else /* !HAVE_CACHE_HASH_SPINLOCK */
static void rsi_put(struct kref *ref)
{
	struct rsi *rsi = container_of(ref, struct rsi, h.ref);

#ifdef HAVE_CACHE_HEAD_HLIST
	LASSERT(hlist_unhashed(&rsi->h.cache_list));
#else
	LASSERT(rsi->h.next == NULL);
#endif
	rsi_free(rsi);
	OBD_FREE_PTR(rsi);
}
#endif /* HAVE_CACHE_HASH_SPINLOCK */

static int rsi_match(struct cache_head *a, struct cache_head *b)
{
        struct rsi *item = container_of(a, struct rsi, h);
        struct rsi *tmp = container_of(b, struct rsi, h);

        return __rsi_match(item, tmp);
}

static void rsi_init(struct cache_head *cnew, struct cache_head *citem)
{
        struct rsi *new = container_of(cnew, struct rsi, h);
        struct rsi *item = container_of(citem, struct rsi, h);

        __rsi_init(new, item);
}

static void update_rsi(struct cache_head *cnew, struct cache_head *citem)
{
        struct rsi *new = container_of(cnew, struct rsi, h);
        struct rsi *item = container_of(citem, struct rsi, h);

        __rsi_update(new, item);
}

static struct cache_head *rsi_alloc(void)
{
        struct rsi *rsi;

        OBD_ALLOC_PTR(rsi);
        if (rsi) 
                return &rsi->h;
        else
                return NULL;
}

static int rsi_parse(struct cache_detail *cd, char *mesg, int mlen)
{
	char *buf = mesg;
	int len;
	struct rsi rsii, *rsip = NULL;
	time64_t expiry;
	int status = -EINVAL;
	ENTRY;

	memset(&rsii, 0, sizeof(rsii));

	/* handle */
	len = qword_get(&mesg, buf, mlen);
	if (len < 0)
		goto out;
	if (rawobj_alloc(&rsii.in_handle, buf, len)) {
		status = -ENOMEM;
		goto out;
	}

	/* token */
	len = qword_get(&mesg, buf, mlen);
	if (len < 0)
		goto out;
	if (rawobj_alloc(&rsii.in_token, buf, len)) {
		status = -ENOMEM;
		goto out;
	}

	rsip = rsi_lookup(&rsii);
	if (!rsip)
		goto out;
	if (!test_bit(CACHE_PENDING, &rsip->h.flags)) {
		/* If this is not a pending request, it probably means
		 * someone wrote arbitrary data to the init channel.
		 * Directly return -EINVAL in this case.
		 */
		status = -EINVAL;
                goto out;
	}

	rsii.h.flags = 0;
	/* expiry */
	expiry = get_expiry(&mesg);
	if (expiry == 0)
		goto out;

	len = qword_get(&mesg, buf, mlen);
	if (len <= 0)
		goto out;

	/* major */
	status = kstrtoint(buf, 10, &rsii.major_status);
	if (status)
		goto out;

	/* minor */
	len = qword_get(&mesg, buf, mlen);
	if (len <= 0) {
		status = -EINVAL;
		goto out;
	}

	status = kstrtoint(buf, 10, &rsii.minor_status);
	if (status)
		goto out;

	/* out_handle */
	len = qword_get(&mesg, buf, mlen);
	if (len < 0)
		goto out;
	if (rawobj_alloc(&rsii.out_handle, buf, len)) {
		status = -ENOMEM;
		goto out;
	}

	/* out_token */
	len = qword_get(&mesg, buf, mlen);
	if (len < 0)
		goto out;
	if (rawobj_alloc(&rsii.out_token, buf, len)) {
		status = -ENOMEM;
		goto out;
	}

	rsii.h.expiry_time = expiry;
	rsip = rsi_update(&rsii, rsip);
	status = 0;
out:
	rsi_free(&rsii);
	if (rsip) {
		wake_up(&rsip->waitq);
		cache_put(&rsip->h, &rsi_cache);
	} else {
		status = -ENOMEM;
	}

	if (status)
		CERROR("rsi parse error %d\n", status);
	RETURN(status);
}

static struct cache_detail rsi_cache = {
	.hash_size	= RSI_HASHMAX,
	.hash_table	= rsi_table,
	.name		= "auth.sptlrpc.init",
	.cache_put	= rsi_put,
	.cache_request	= rsi_request,
	.cache_upcall	= sunrpc_cache_pipe_upcall,
	.cache_parse	= rsi_parse,
	.match		= rsi_match,
	.init		= rsi_init,
	.update		= update_rsi,
	.alloc		= rsi_alloc,
};

static struct rsi *rsi_lookup(struct rsi *item)
{
        struct cache_head *ch;
        int hash = rsi_hash(item);

        ch = sunrpc_cache_lookup(&rsi_cache, &item->h, hash);
        if (ch)
                return container_of(ch, struct rsi, h);
        else
                return NULL;
}

static struct rsi *rsi_update(struct rsi *new, struct rsi *old)
{
        struct cache_head *ch;
        int hash = rsi_hash(new);

        ch = sunrpc_cache_update(&rsi_cache, &new->h, &old->h, hash);
        if (ch)
                return container_of(ch, struct rsi, h);
        else
                return NULL;
}

/****************************************
 * rpc sec context (rsc) cache                            *
 ****************************************/

#define RSC_HASHBITS    (10)
#define RSC_HASHMAX     (1 << RSC_HASHBITS)
#define RSC_HASHMASK    (RSC_HASHMAX - 1)

struct rsc {
        struct cache_head       h;
        struct obd_device      *target;
        rawobj_t                handle;
        struct gss_svc_ctx      ctx;
#ifdef HAVE_CACHE_HASH_SPINLOCK
	struct rcu_head		rcu_head;
#endif
};

#ifdef HAVE_CACHE_HEAD_HLIST
static struct hlist_head rsc_table[RSC_HASHMAX];
#else
static struct cache_head *rsc_table[RSC_HASHMAX];
#endif
static struct cache_detail rsc_cache;
static struct rsc *rsc_update(struct rsc *new, struct rsc *old);
static struct rsc *rsc_lookup(struct rsc *item);

static void rsc_free(struct rsc *rsci)
{
        rawobj_free(&rsci->handle);
        rawobj_free(&rsci->ctx.gsc_rvs_hdl);
        lgss_delete_sec_context(&rsci->ctx.gsc_mechctx);
}

static inline int rsc_hash(struct rsc *rsci)
{
        return hash_mem((char *)rsci->handle.data,
                        rsci->handle.len, RSC_HASHBITS);
}

static inline int __rsc_match(struct rsc *new, struct rsc *tmp)
{
        return rawobj_equal(&new->handle, &tmp->handle);
}

static inline void __rsc_init(struct rsc *new, struct rsc *tmp)
{
        new->handle = tmp->handle;
        tmp->handle = RAWOBJ_EMPTY;

        new->target = NULL;
        memset(&new->ctx, 0, sizeof(new->ctx));
        new->ctx.gsc_rvs_hdl = RAWOBJ_EMPTY;
}

static inline void __rsc_update(struct rsc *new, struct rsc *tmp)
{
	new->ctx = tmp->ctx;
	memset(&tmp->ctx, 0, sizeof(tmp->ctx));
	tmp->ctx.gsc_rvs_hdl = RAWOBJ_EMPTY;
	tmp->ctx.gsc_mechctx = NULL;
	tmp->target = NULL;

	memset(&new->ctx.gsc_seqdata, 0, sizeof(new->ctx.gsc_seqdata));
	spin_lock_init(&new->ctx.gsc_seqdata.ssd_lock);
}

#ifdef HAVE_CACHE_HASH_SPINLOCK
static void rsc_free_rcu(struct rcu_head *head)
{
	struct rsc *rsci = container_of(head, struct rsc, rcu_head);

#ifdef HAVE_CACHE_HEAD_HLIST
	LASSERT(hlist_unhashed(&rsci->h.cache_list));
#else
	LASSERT(rsci->h.next == NULL);
#endif
	rawobj_free(&rsci->handle);
	OBD_FREE_PTR(rsci);
}

static void rsc_put(struct kref *ref)
{
	struct rsc *rsci = container_of(ref, struct rsc, h.ref);

	rawobj_free(&rsci->ctx.gsc_rvs_hdl);
	lgss_delete_sec_context(&rsci->ctx.gsc_mechctx);
	call_rcu(&rsci->rcu_head, rsc_free_rcu);
}
#else /* !HAVE_CACHE_HASH_SPINLOCK */
static void rsc_put(struct kref *ref)
{
	struct rsc *rsci = container_of(ref, struct rsc, h.ref);

#ifdef HAVE_CACHE_HEAD_HLIST
	LASSERT(hlist_unhashed(&rsci->h.cache_list));
#else
	LASSERT(rsci->h.next == NULL);
#endif
	rsc_free(rsci);
	OBD_FREE_PTR(rsci);
}
#endif /* HAVE_CACHE_HASH_SPINLOCK */

static int rsc_match(struct cache_head *a, struct cache_head *b)
{
        struct rsc *new = container_of(a, struct rsc, h);
        struct rsc *tmp = container_of(b, struct rsc, h);

        return __rsc_match(new, tmp);
}

static void rsc_init(struct cache_head *cnew, struct cache_head *ctmp)
{
        struct rsc *new = container_of(cnew, struct rsc, h);
        struct rsc *tmp = container_of(ctmp, struct rsc, h);

        __rsc_init(new, tmp);
}

static void update_rsc(struct cache_head *cnew, struct cache_head *ctmp)
{
        struct rsc *new = container_of(cnew, struct rsc, h);
        struct rsc *tmp = container_of(ctmp, struct rsc, h);

        __rsc_update(new, tmp);
}

static struct cache_head * rsc_alloc(void)
{
        struct rsc *rsc;

        OBD_ALLOC_PTR(rsc);
        if (rsc)
                return &rsc->h;
        else
                return NULL;
}

static int rsc_parse(struct cache_detail *cd, char *mesg, int mlen)
{
        char                *buf = mesg;
        int                  len, rv, tmp_int;
        struct rsc           rsci, *rscp = NULL;
	time64_t expiry;
        int                  status = -EINVAL;
        struct gss_api_mech *gm = NULL;

        memset(&rsci, 0, sizeof(rsci));

        /* context handle */
        len = qword_get(&mesg, buf, mlen);
        if (len < 0) goto out;
        status = -ENOMEM;
        if (rawobj_alloc(&rsci.handle, buf, len))
                goto out;

        rsci.h.flags = 0;
        /* expiry */
        expiry = get_expiry(&mesg);
        status = -EINVAL;
        if (expiry == 0)
                goto out;

        /* remote flag */
        rv = get_int(&mesg, &tmp_int);
        if (rv) {
                CERROR("fail to get remote flag\n");
                goto out;
        }
        rsci.ctx.gsc_remote = (tmp_int != 0);

	/* root user flag */
	rv = get_int(&mesg, &tmp_int);
	if (rv) {
		CERROR("fail to get root user flag\n");
		goto out;
	}
	rsci.ctx.gsc_usr_root = (tmp_int != 0);

        /* mds user flag */
        rv = get_int(&mesg, &tmp_int);
        if (rv) {
                CERROR("fail to get mds user flag\n");
                goto out;
        }
        rsci.ctx.gsc_usr_mds = (tmp_int != 0);

        /* oss user flag */
        rv = get_int(&mesg, &tmp_int);
        if (rv) {
                CERROR("fail to get oss user flag\n");
                goto out;
        }
        rsci.ctx.gsc_usr_oss = (tmp_int != 0);

        /* mapped uid */
        rv = get_int(&mesg, (int *) &rsci.ctx.gsc_mapped_uid);
        if (rv) {
                CERROR("fail to get mapped uid\n");
                goto out;
        }

        rscp = rsc_lookup(&rsci);
        if (!rscp)
                goto out;

        /* uid, or NEGATIVE */
        rv = get_int(&mesg, (int *) &rsci.ctx.gsc_uid);
        if (rv == -EINVAL)
                goto out;
        if (rv == -ENOENT) {
                CERROR("NOENT? set rsc entry negative\n");
		set_bit(CACHE_NEGATIVE, &rsci.h.flags);
        } else {
		rawobj_t tmp_buf;
		time64_t ctx_expiry;

		/* gid */
		if (get_int(&mesg, (int *) &rsci.ctx.gsc_gid))
			goto out;

		/* mech name */
		len = qword_get(&mesg, buf, mlen);
		if (len < 0)
			goto out;
		gm = lgss_name_to_mech(buf);
		status = -EOPNOTSUPP;
		if (!gm)
			goto out;

		status = -EINVAL;
		/* mech-specific data: */
		len = qword_get(&mesg, buf, mlen);
		if (len < 0)
			goto out;

		tmp_buf.len = len;
		tmp_buf.data = (unsigned char *)buf;
		if (lgss_import_sec_context(&tmp_buf, gm,
					    &rsci.ctx.gsc_mechctx))
			goto out;

		/* set to seconds since machine booted */
		expiry = ktime_get_seconds();

		/* currently the expiry time passed down from user-space
		 * is invalid, here we retrive it from mech.
		 */
		if (lgss_inquire_context(rsci.ctx.gsc_mechctx, &ctx_expiry)) {
			CERROR("unable to get expire time, drop it\n");
			goto out;
		}

		/* ctx_expiry is the number of seconds since Jan 1 1970.
		 * We want just the  number of seconds into the future.
		 */
		expiry += ctx_expiry - ktime_get_real_seconds();
        }

        rsci.h.expiry_time = expiry;
        rscp = rsc_update(&rsci, rscp);
        status = 0;
out:
        if (gm)
                lgss_mech_put(gm);
        rsc_free(&rsci);
        if (rscp)
                cache_put(&rscp->h, &rsc_cache);
        else
                status = -ENOMEM;

        if (status)
                CERROR("parse rsc error %d\n", status);
        return status;
}

static struct cache_detail rsc_cache = {
        .hash_size      = RSC_HASHMAX,
        .hash_table     = rsc_table,
        .name           = "auth.sptlrpc.context",
        .cache_put      = rsc_put,
        .cache_parse    = rsc_parse,
        .match          = rsc_match,
        .init           = rsc_init,
        .update         = update_rsc,
        .alloc          = rsc_alloc,
};

static struct rsc *rsc_lookup(struct rsc *item)
{
        struct cache_head *ch;
        int                hash = rsc_hash(item);

        ch = sunrpc_cache_lookup(&rsc_cache, &item->h, hash);
        if (ch)
                return container_of(ch, struct rsc, h);
        else
                return NULL;
}

static struct rsc *rsc_update(struct rsc *new, struct rsc *old)
{
        struct cache_head *ch;
        int                hash = rsc_hash(new);

        ch = sunrpc_cache_update(&rsc_cache, &new->h, &old->h, hash);
        if (ch)
                return container_of(ch, struct rsc, h);
        else
                return NULL;
}

#define COMPAT_RSC_PUT(item, cd)        cache_put((item), (cd))

/****************************************
 * rsc cache flush                      *
 ****************************************/

static struct rsc *gss_svc_searchbyctx(rawobj_t *handle)
{
        struct rsc  rsci;
        struct rsc *found;

        memset(&rsci, 0, sizeof(rsci));
        if (rawobj_dup(&rsci.handle, handle))
                return NULL;

        found = rsc_lookup(&rsci);
        rsc_free(&rsci);
        if (!found)
                return NULL;
        if (cache_check(&rsc_cache, &found->h, NULL))
                return NULL;
        return found;
}

int gss_svc_upcall_install_rvs_ctx(struct obd_import *imp,
                                   struct gss_sec *gsec,
                                   struct gss_cli_ctx *gctx)
{
        struct rsc      rsci, *rscp = NULL;
	time64_t ctx_expiry;
        __u32           major;
        int             rc;
        ENTRY;

        memset(&rsci, 0, sizeof(rsci));

        if (rawobj_alloc(&rsci.handle, (char *) &gsec->gs_rvs_hdl,
                         sizeof(gsec->gs_rvs_hdl)))
                GOTO(out, rc = -ENOMEM);

        rscp = rsc_lookup(&rsci);
        if (rscp == NULL)
                GOTO(out, rc = -ENOMEM);

        major = lgss_copy_reverse_context(gctx->gc_mechctx,
                                          &rsci.ctx.gsc_mechctx);
        if (major != GSS_S_COMPLETE)
                GOTO(out, rc = -ENOMEM);

        if (lgss_inquire_context(rsci.ctx.gsc_mechctx, &ctx_expiry)) {
                CERROR("unable to get expire time, drop it\n");
                GOTO(out, rc = -EINVAL);
        }
	rsci.h.expiry_time = ctx_expiry;

	switch (imp->imp_obd->u.cli.cl_sp_to) {
	case LUSTRE_SP_MDT:
		rsci.ctx.gsc_usr_mds = 1;
		break;
	case LUSTRE_SP_OST:
		rsci.ctx.gsc_usr_oss = 1;
		break;
	case LUSTRE_SP_CLI:
		rsci.ctx.gsc_usr_root = 1;
		break;
	case LUSTRE_SP_MGS:
		/* by convention, all 3 set to 1 means MGS */
		rsci.ctx.gsc_usr_mds = 1;
		rsci.ctx.gsc_usr_oss = 1;
		rsci.ctx.gsc_usr_root = 1;
		break;
	default:
		break;
	}

        rscp = rsc_update(&rsci, rscp);
        if (rscp == NULL)
                GOTO(out, rc = -ENOMEM);

        rscp->target = imp->imp_obd;
        rawobj_dup(&gctx->gc_svc_handle, &rscp->handle);

	CDEBUG(D_SEC, "create reverse svc ctx %p to %s: idx %#llx\n",
	       &rscp->ctx, obd2cli_tgt(imp->imp_obd), gsec->gs_rvs_hdl);
	rc = 0;
out:
        if (rscp)
                cache_put(&rscp->h, &rsc_cache);
        rsc_free(&rsci);

        if (rc)
		CERROR("create reverse svc ctx: idx %#llx, rc %d\n",
                       gsec->gs_rvs_hdl, rc);
        RETURN(rc);
}

int gss_svc_upcall_expire_rvs_ctx(rawobj_t *handle)
{
	const time64_t expire = 20;
	struct rsc *rscp;

        rscp = gss_svc_searchbyctx(handle);
        if (rscp) {
                CDEBUG(D_SEC, "reverse svcctx %p (rsc %p) expire soon\n",
                       &rscp->ctx, rscp);

		rscp->h.expiry_time = ktime_get_real_seconds() + expire;
                COMPAT_RSC_PUT(&rscp->h, &rsc_cache);
        }
        return 0;
}

int gss_svc_upcall_dup_handle(rawobj_t *handle, struct gss_svc_ctx *ctx)
{
        struct rsc *rscp = container_of(ctx, struct rsc, ctx);

        return rawobj_dup(handle, &rscp->handle);
}

int gss_svc_upcall_update_sequence(rawobj_t *handle, __u32 seq)
{
        struct rsc             *rscp;

        rscp = gss_svc_searchbyctx(handle);
        if (rscp) {
                CDEBUG(D_SEC, "reverse svcctx %p (rsc %p) update seq to %u\n",
                       &rscp->ctx, rscp, seq + 1);

                rscp->ctx.gsc_rvs_seq = seq + 1;
                COMPAT_RSC_PUT(&rscp->h, &rsc_cache);
        }
        return 0;
}

static struct cache_deferred_req* cache_upcall_defer(struct cache_req *req)
{
        return NULL;
}
static struct cache_req cache_upcall_chandle = { cache_upcall_defer };

int gss_svc_upcall_handle_init(struct ptlrpc_request *req,
			       struct gss_svc_reqctx *grctx,
			       struct gss_wire_ctx *gw,
			       struct obd_device *target,
			       __u32 lustre_svc,
			       rawobj_t *rvs_hdl,
			       rawobj_t *in_token)
{
	struct ptlrpc_reply_state *rs;
	struct rsc                *rsci = NULL;
	struct rsi                *rsip = NULL, rsikey;
	wait_queue_entry_t wait;
	int                        replen = sizeof(struct ptlrpc_body);
	struct gss_rep_header     *rephdr;
	int                        first_check = 1;
	int                        rc = SECSVC_DROP;

	ENTRY;
	memset(&rsikey, 0, sizeof(rsikey));
	rsikey.lustre_svc = lustre_svc;
	/* In case of MR, rq_peer is not the NID from which request is received,
	 * but primary NID of peer.
	 * So we need LNetPrimaryNID(rq_source) to match what the clients uses.
	 */
	LNetPrimaryNID(&req->rq_source.nid);
	rsikey.nid4 = lnet_nid_to_nid4(&req->rq_source.nid);
	nodemap_test_nid(lnet_nid_to_nid4(&req->rq_peer.nid), rsikey.nm_name,
			 sizeof(rsikey.nm_name));

        /* duplicate context handle. for INIT it always 0 */
        if (rawobj_dup(&rsikey.in_handle, &gw->gw_handle)) {
                CERROR("fail to dup context handle\n");
                GOTO(out, rc);
        }

        if (rawobj_dup(&rsikey.in_token, in_token)) {
                CERROR("can't duplicate token\n");
                rawobj_free(&rsikey.in_handle);
                GOTO(out, rc);
        }

        rsip = rsi_lookup(&rsikey);
        rsi_free(&rsikey);
        if (!rsip) {
                CERROR("error in rsi_lookup.\n");

                if (!gss_pack_err_notify(req, GSS_S_FAILURE, 0))
                        rc = SECSVC_COMPLETE;

                GOTO(out, rc);
        }

	cache_get(&rsip->h); /* take an extra ref */
	init_wait(&wait);
	add_wait_queue(&rsip->waitq, &wait);

cache_check:
	/* Note each time cache_check() will drop a reference if return
	 * non-zero. We hold an extra reference on initial rsip, but must
	 * take care of following calls. */
	rc = cache_check(&rsi_cache, &rsip->h, &cache_upcall_chandle);
	switch (rc) {
	case -ETIMEDOUT:
	case -EAGAIN: {
		int valid;

		if (first_check) {
			first_check = 0;

			cache_read_lock(&rsi_cache);
			valid = test_bit(CACHE_VALID, &rsip->h.flags);
			if (valid == 0)
				set_current_state(TASK_INTERRUPTIBLE);
			cache_read_unlock(&rsi_cache);

			if (valid == 0) {
				unsigned long timeout;

				timeout = cfs_time_seconds(GSS_SVC_UPCALL_TIMEOUT);
				schedule_timeout(timeout);
			}
			cache_get(&rsip->h);
			goto cache_check;
		}
		CWARN("waited %ds timeout, drop\n", GSS_SVC_UPCALL_TIMEOUT);
		break;
	}
	case -ENOENT:
		CDEBUG(D_SEC, "cache_check return ENOENT, drop\n");
		break;
	case 0:
		/* if not the first check, we have to release the extra
		 * reference we just added on it. */
		if (!first_check)
			cache_put(&rsip->h, &rsi_cache);
		CDEBUG(D_SEC, "cache_check is good\n");
		break;
	}

	remove_wait_queue(&rsip->waitq, &wait);
	cache_put(&rsip->h, &rsi_cache);

	if (rc)
		GOTO(out, rc = SECSVC_DROP);

        rc = SECSVC_DROP;
        rsci = gss_svc_searchbyctx(&rsip->out_handle);
        if (!rsci) {
                CERROR("authentication failed\n");

		/* gss mechanism returned major and minor code so we return
		 * those in error message */
		if (!gss_pack_err_notify(req, rsip->major_status,
					 rsip->minor_status))
			rc = SECSVC_COMPLETE;

                GOTO(out, rc);
        } else {
                cache_get(&rsci->h);
                grctx->src_ctx = &rsci->ctx;
        }

	if (gw->gw_flags & LUSTRE_GSS_PACK_KCSUM) {
		grctx->src_ctx->gsc_mechctx->hash_func = gss_digest_hash;
	} else if (!strcmp(grctx->src_ctx->gsc_mechctx->mech_type->gm_name,
			   "krb5") &&
		   !krb5_allow_old_client_csum) {
		CWARN("%s: deny connection from '%s' due to missing 'krb_csum' feature, set 'sptlrpc.gss.krb5_allow_old_client_csum=1' to allow, but recommend client upgrade: rc = %d\n",
		      target->obd_name, libcfs_nidstr(&req->rq_peer.nid),
		      -EPROTO);
		GOTO(out, rc = SECSVC_DROP);
	} else {
		grctx->src_ctx->gsc_mechctx->hash_func =
			gss_digest_hash_compat;
	}

        if (rawobj_dup(&rsci->ctx.gsc_rvs_hdl, rvs_hdl)) {
                CERROR("failed duplicate reverse handle\n");
                GOTO(out, rc);
        }

        rsci->target = target;

	CDEBUG(D_SEC, "server create rsc %p(%u->%s)\n",
	       rsci, rsci->ctx.gsc_uid, libcfs_nidstr(&req->rq_peer.nid));

        if (rsip->out_handle.len > PTLRPC_GSS_MAX_HANDLE_SIZE) {
                CERROR("handle size %u too large\n", rsip->out_handle.len);
                GOTO(out, rc = SECSVC_DROP);
        }

        grctx->src_init = 1;
	grctx->src_reserve_len = round_up(rsip->out_token.len, 4);

        rc = lustre_pack_reply_v2(req, 1, &replen, NULL, 0);
        if (rc) {
                CERROR("failed to pack reply: %d\n", rc);
                GOTO(out, rc = SECSVC_DROP);
        }

        rs = req->rq_reply_state;
        LASSERT(rs->rs_repbuf->lm_bufcount == 3);
        LASSERT(rs->rs_repbuf->lm_buflens[0] >=
                sizeof(*rephdr) + rsip->out_handle.len);
        LASSERT(rs->rs_repbuf->lm_buflens[2] >= rsip->out_token.len);

        rephdr = lustre_msg_buf(rs->rs_repbuf, 0, 0);
        rephdr->gh_version = PTLRPC_GSS_VERSION;
        rephdr->gh_flags = 0;
        rephdr->gh_proc = PTLRPC_GSS_PROC_ERR;
        rephdr->gh_major = rsip->major_status;
        rephdr->gh_minor = rsip->minor_status;
        rephdr->gh_seqwin = GSS_SEQ_WIN;
        rephdr->gh_handle.len = rsip->out_handle.len;
        memcpy(rephdr->gh_handle.data, rsip->out_handle.data,
               rsip->out_handle.len);

        memcpy(lustre_msg_buf(rs->rs_repbuf, 2, 0), rsip->out_token.data,
               rsip->out_token.len);

        rs->rs_repdata_len = lustre_shrink_msg(rs->rs_repbuf, 2,
                                               rsip->out_token.len, 0);

        rc = SECSVC_OK;

out:
	/* it looks like here we should put rsip also, but this mess up
	 * with NFS cache mgmt code... FIXME
	 * something like:
	 * if (rsip)
	 *     rsi_put(&rsip->h, &rsi_cache); */

	if (rsci) {
		/* if anything went wrong, we don't keep the context too */
		if (rc != SECSVC_OK)
			set_bit(CACHE_NEGATIVE, &rsci->h.flags);
		else
			CDEBUG(D_SEC, "create rsc with idx %#llx\n",
			       gss_handle_to_u64(&rsci->handle));

		COMPAT_RSC_PUT(&rsci->h, &rsc_cache);
	}
	RETURN(rc);
}

struct gss_svc_ctx *gss_svc_upcall_get_ctx(struct ptlrpc_request *req,
					   struct gss_wire_ctx *gw)
{
	struct rsc *rsc;

	rsc = gss_svc_searchbyctx(&gw->gw_handle);
	if (!rsc) {
		CWARN("Invalid gss ctx idx %#llx from %s\n",
		      gss_handle_to_u64(&gw->gw_handle),
		      libcfs_nidstr(&req->rq_peer.nid));
		return NULL;
	}

	return &rsc->ctx;
}

void gss_svc_upcall_put_ctx(struct gss_svc_ctx *ctx)
{
        struct rsc *rsc = container_of(ctx, struct rsc, ctx);

        COMPAT_RSC_PUT(&rsc->h, &rsc_cache);
}

void gss_svc_upcall_destroy_ctx(struct gss_svc_ctx *ctx)
{
        struct rsc *rsc = container_of(ctx, struct rsc, ctx);

        /* can't be found */
	set_bit(CACHE_NEGATIVE, &rsc->h.flags);
        /* to be removed at next scan */
        rsc->h.expiry_time = 1;
}

int __init gss_init_svc_upcall(void)
{
	int	i, rc;

	/*
	 * this helps reducing context index confliction. after server reboot,
	 * conflicting request from clients might be filtered out by initial
	 * sequence number checking, thus no chance to sent error notification
	 * back to clients.
	 */
	get_random_bytes(&__ctx_index, sizeof(__ctx_index));

#ifdef HAVE_CACHE_HEAD_HLIST
	for (i = 0; i < rsi_cache.hash_size; i++)
		INIT_HLIST_HEAD(&rsi_cache.hash_table[i]);
#endif
	rc = cache_register_net(&rsi_cache, &init_net);
	if (rc != 0)
		return rc;

#ifdef HAVE_CACHE_HEAD_HLIST
	for (i = 0; i < rsc_cache.hash_size; i++)
		INIT_HLIST_HEAD(&rsc_cache.hash_table[i]);
#endif
	rc = cache_register_net(&rsc_cache, &init_net);
	if (rc != 0) {
		cache_unregister_net(&rsi_cache, &init_net);
		return rc;
	}

	/* FIXME this looks stupid. we intend to give lsvcgssd a chance to open
	 * the init upcall channel, otherwise there's big chance that the first
	 * upcall issued before the channel be opened thus nfsv4 cache code will
	 * drop the request directly, thus lead to unnecessary recovery time.
	 * Here we wait at minimum 1.5 seconds.
	 */
	for (i = 0; i < 6; i++) {
		if (channel_users(&rsi_cache) > 0)
			break;
		schedule_timeout_uninterruptible(cfs_time_seconds(1) / 4);
	}

	if (channel_users(&rsi_cache) == 0)
		CDEBUG(D_SEC,
		       "Init channel is not opened by lsvcgssd, following request might be dropped until lsvcgssd is active\n");

	return 0;
}

void gss_exit_svc_upcall(void)
{
	cache_purge(&rsi_cache);
	cache_unregister_net(&rsi_cache, &init_net);

	cache_purge(&rsc_cache);
	cache_unregister_net(&rsc_cache, &init_net);
}
