/*
 * Copyright (c) 2010 Cisco Systems, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 */

/* XXX TBD some includes may be extraneous */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/utsname.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/configfs.h>
#include <linux/ctype.h>
#include <linux/hash.h>
#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/kref.h>
#include <asm/unaligned.h>
#include <scsi/libfc.h>

#include <target/target_core_base.h>
#include <target/target_core_fabric.h>

#include "tcm_fc.h"

static void ft_sess_delete_all(struct ft_tport *);

/*
 * Lookup or allocate target local port.
 * Caller holds ft_lport_lock.
 */
static struct ft_tport *ft_tport_get(struct fc_lport *lport)
{
        struct ft_tpg *tpg;
        struct ft_tport *tport;
        int i;

        tport = rcu_dereference_protected(lport->prov[FC_TYPE_FCP],
                                          lockdep_is_held(&ft_lport_lock));
        if (tport && tport->tpg)
                return tport;

        tpg = ft_lport_find_tpg(lport);
        if (!tpg)
                return NULL;

        if (tport) {
                tport->tpg = tpg;
                tpg->tport = tport;
                return tport;
        }

        tport = kzalloc(sizeof(*tport), GFP_KERNEL);
        if (!tport)
                return NULL;

        tport->lport = lport;
        tport->tpg = tpg;
        tpg->tport = tport;
        for (i = 0; i < FT_SESS_HASH_SIZE; i++)
                INIT_HLIST_HEAD(&tport->hash[i]);

        rcu_assign_pointer(lport->prov[FC_TYPE_FCP], tport);
        return tport;
}

/*
 * Delete a target local port.
 * Caller holds ft_lport_lock.
 */
static void ft_tport_delete(struct ft_tport *tport)
{
        struct fc_lport *lport;
        struct ft_tpg *tpg;

        ft_sess_delete_all(tport);
        lport = tport->lport;
        BUG_ON(tport != lport->prov[FC_TYPE_FCP]);
        RCU_INIT_POINTER(lport->prov[FC_TYPE_FCP], NULL);

        tpg = tport->tpg;
        if (tpg) {
                tpg->tport = NULL;
                tport->tpg = NULL;
        }
        kfree_rcu(tport, rcu);
}

/*
 * Add local port.
 * Called thru fc_lport_iterate().
 */
void ft_lport_add(struct fc_lport *lport, void *arg)
{
        mutex_lock(&ft_lport_lock);
        ft_tport_get(lport);
        mutex_unlock(&ft_lport_lock);
}

/*
 * Delete local port.
 * Called thru fc_lport_iterate().
 */
void ft_lport_del(struct fc_lport *lport, void *arg)
{
        struct ft_tport *tport;

        mutex_lock(&ft_lport_lock);
        tport = lport->prov[FC_TYPE_FCP];
        if (tport)
                ft_tport_delete(tport);
        mutex_unlock(&ft_lport_lock);
}

/*
 * Notification of local port change from libfc.
 * Create or delete local port and associated tport.
 */
int ft_lport_notify(struct notifier_block *nb, unsigned long event, void *arg)
{
        struct fc_lport *lport = arg;

        switch (event) {
        case FC_LPORT_EV_ADD:
                ft_lport_add(lport, NULL);
                break;
        case FC_LPORT_EV_DEL:
                ft_lport_del(lport, NULL);
                break;
        }
        return NOTIFY_DONE;
}

/*
 * Hash function for FC_IDs.
 */
static u32 ft_sess_hash(u32 port_id)
{
        return hash_32(port_id, FT_SESS_HASH_BITS);
}

/*
 * Find session in local port.
 * Sessions and hash lists are RCU-protected.
 * A reference is taken which must be eventually freed.
 */
static struct ft_sess *ft_sess_get(struct fc_lport *lport, u32 port_id)
{
        struct ft_tport *tport;
        struct hlist_head *head;
        struct ft_sess *sess;

        rcu_read_lock();
        tport = rcu_dereference(lport->prov[FC_TYPE_FCP]);
        if (!tport)
                goto out;

        head = &tport->hash[ft_sess_hash(port_id)];
        hlist_for_each_entry_rcu(sess, head, hash) {
                if (sess->port_id == port_id) {
                        kref_get(&sess->kref);
                        rcu_read_unlock();
                        pr_debug("port_id %x found %p\n", port_id, sess);
                        return sess;
                }
        }
out:
        rcu_read_unlock();
        pr_debug("port_id %x not found\n", port_id);
        return NULL;
}

static int ft_sess_alloc_cb(struct se_portal_group *se_tpg,
                            struct se_session *se_sess, void *p)
{
        struct ft_sess *sess = p;
        struct ft_tport *tport = sess->tport;
        struct hlist_head *head = &tport->hash[ft_sess_hash(sess->port_id)];

        pr_debug("port_id %x sess %p\n", sess->port_id, sess);
        hlist_add_head_rcu(&sess->hash, head);
        tport->sess_count++;

        return 0;
}

/*
 * Allocate session and enter it in the hash for the local port.
 * Caller holds ft_lport_lock.
 */
static struct ft_sess *ft_sess_create(struct ft_tport *tport, u32 port_id,
                                      struct fc_rport_priv *rdata)
{
        struct se_portal_group *se_tpg = &tport->tpg->se_tpg;
        struct ft_sess *sess;
        struct hlist_head *head;
        unsigned char initiatorname[TRANSPORT_IQN_LEN];

        ft_format_wwn(&initiatorname[0], TRANSPORT_IQN_LEN, rdata->ids.port_name);

        head = &tport->hash[ft_sess_hash(port_id)];
        hlist_for_each_entry_rcu(sess, head, hash)
                if (sess->port_id == port_id)
                        return sess;

        sess = kzalloc(sizeof(*sess), GFP_KERNEL);
        if (!sess)
                return NULL;

        kref_init(&sess->kref); /* ref for table entry */
        sess->tport = tport;
        sess->port_id = port_id;

        sess->se_sess = target_alloc_session(se_tpg, TCM_FC_DEFAULT_TAGS,
                                             sizeof(struct ft_cmd),
                                             TARGET_PROT_NORMAL, &initiatorname[0],
                                             sess, ft_sess_alloc_cb);
        if (IS_ERR(sess->se_sess)) {
                kfree(sess);
                return NULL;
        }
        return sess;
}

/*
 * Unhash the session.
 * Caller holds ft_lport_lock.
 */
static void ft_sess_unhash(struct ft_sess *sess)
{
        struct ft_tport *tport = sess->tport;

        hlist_del_rcu(&sess->hash);
        BUG_ON(!tport->sess_count);
        tport->sess_count--;
        sess->port_id = -1;
        sess->params = 0;
}

/*
 * Delete session from hash.
 * Caller holds ft_lport_lock.
 */
static struct ft_sess *ft_sess_delete(struct ft_tport *tport, u32 port_id)
{
        struct hlist_head *head;
        struct ft_sess *sess;

        head = &tport->hash[ft_sess_hash(port_id)];
        hlist_for_each_entry_rcu(sess, head, hash) {
                if (sess->port_id == port_id) {
                        ft_sess_unhash(sess);
                        return sess;
                }
        }
        return NULL;
}

static void ft_close_sess(struct ft_sess *sess)
{
        transport_deregister_session_configfs(sess->se_sess);
        target_sess_cmd_list_set_waiting(sess->se_sess);
        target_wait_for_sess_cmds(sess->se_sess);
        ft_sess_put(sess);
}

/*
 * Delete all sessions from tport.
 * Caller holds ft_lport_lock.
 */
static void ft_sess_delete_all(struct ft_tport *tport)
{
        struct hlist_head *head;
        struct ft_sess *sess;

        for (head = tport->hash;
             head < &tport->hash[FT_SESS_HASH_SIZE]; head++) {
                hlist_for_each_entry_rcu(sess, head, hash) {
                        ft_sess_unhash(sess);
                        ft_close_sess(sess);    /* release from table */
                }
        }
}

/*
 * TCM ops for sessions.
 */

/*
 * Determine whether session is allowed to be shutdown in the current context.
 * Returns non-zero if the session should be shutdown.
 */
int ft_sess_shutdown(struct se_session *se_sess)
{
        struct ft_sess *sess = se_sess->fabric_sess_ptr;

        pr_debug("port_id %x\n", sess->port_id);
        return 1;
}

/*
 * Remove session and send PRLO.
 * This is called when the ACL is being deleted or queue depth is changing.
 */
void ft_sess_close(struct se_session *se_sess)
{
        struct ft_sess *sess = se_sess->fabric_sess_ptr;
        u32 port_id;

        mutex_lock(&ft_lport_lock);
        port_id = sess->port_id;
        if (port_id == -1) {
                mutex_unlock(&ft_lport_lock);
                return;
        }
        pr_debug("port_id %x\n", port_id);
        ft_sess_unhash(sess);
        mutex_unlock(&ft_lport_lock);
        ft_close_sess(sess);
        /* XXX Send LOGO or PRLO */
        synchronize_rcu();              /* let transport deregister happen */
}

u32 ft_sess_get_index(struct se_session *se_sess)
{
        struct ft_sess *sess = se_sess->fabric_sess_ptr;

        return sess->port_id;   /* XXX TBD probably not what is needed */
}

u32 ft_sess_get_port_name(struct se_session *se_sess,
                          unsigned char *buf, u32 len)
{
        struct ft_sess *sess = se_sess->fabric_sess_ptr;

        return ft_format_wwn(buf, len, sess->port_name);
}

/*
 * libfc ops involving sessions.
 */

static int ft_prli_locked(struct fc_rport_priv *rdata, u32 spp_len,
                          const struct fc_els_spp *rspp, struct fc_els_spp *spp)
{
        struct ft_tport *tport;
        struct ft_sess *sess;
        u32 fcp_parm;

        tport = ft_tport_get(rdata->local_port);
        if (!tport)
                goto not_target;        /* not a target for this local port */

        if (!rspp)
                goto fill;

        if (rspp->spp_flags & (FC_SPP_OPA_VAL | FC_SPP_RPA_VAL))
                return FC_SPP_RESP_NO_PA;

        /*
         * If both target and initiator bits are off, the SPP is invalid.
         */
        fcp_parm = ntohl(rspp->spp_params);
        if (!(fcp_parm & (FCP_SPPF_INIT_FCN | FCP_SPPF_TARG_FCN)))
                return FC_SPP_RESP_INVL;

        /*
         * Create session (image pair) only if requested by
         * EST_IMG_PAIR flag and if the requestor is an initiator.
         */
        if (rspp->spp_flags & FC_SPP_EST_IMG_PAIR) {
                spp->spp_flags |= FC_SPP_EST_IMG_PAIR;
                if (!(fcp_parm & FCP_SPPF_INIT_FCN))
                        return FC_SPP_RESP_CONF;
                sess = ft_sess_create(tport, rdata->ids.port_id, rdata);
                if (!sess)
                        return FC_SPP_RESP_RES;
                if (!sess->params)
                        rdata->prli_count++;
                sess->params = fcp_parm;
                sess->port_name = rdata->ids.port_name;
                sess->max_frame = rdata->maxframe_size;

                /* XXX TBD - clearing actions.  unit attn, see 4.10 */
        }

        /*
         * OR in our service parameters with other provider (initiator), if any.
         */
fill:
        fcp_parm = ntohl(spp->spp_params);
        fcp_parm &= ~FCP_SPPF_RETRY;
        spp->spp_params = htonl(fcp_parm | FCP_SPPF_TARG_FCN);
        return FC_SPP_RESP_ACK;

not_target:
        fcp_parm = ntohl(spp->spp_params);
        fcp_parm &= ~FCP_SPPF_TARG_FCN;
        spp->spp_params = htonl(fcp_parm);
        return 0;
}

/**
 * tcm_fcp_prli() - Handle incoming or outgoing PRLI for the FCP target
 * @rdata: remote port private
 * @spp_len: service parameter page length
 * @rspp: received service parameter page (NULL for outgoing PRLI)
 * @spp: response service parameter page
 *
 * Returns spp response code.
 */
static int ft_prli(struct fc_rport_priv *rdata, u32 spp_len,
                   const struct fc_els_spp *rspp, struct fc_els_spp *spp)
{
        int ret;

        mutex_lock(&ft_lport_lock);
        ret = ft_prli_locked(rdata, spp_len, rspp, spp);
        mutex_unlock(&ft_lport_lock);
        pr_debug("port_id %x flags %x ret %x\n",
               rdata->ids.port_id, rspp ? rspp->spp_flags : 0, ret);
        return ret;
}

static void ft_sess_free(struct kref *kref)
{
        struct ft_sess *sess = container_of(kref, struct ft_sess, kref);

        transport_deregister_session(sess->se_sess);
        kfree_rcu(sess, rcu);
}

void ft_sess_put(struct ft_sess *sess)
{
        int sess_held = atomic_read(&sess->kref.refcount);

        BUG_ON(!sess_held);
        kref_put(&sess->kref, ft_sess_free);
}

static void ft_prlo(struct fc_rport_priv *rdata)
{
        struct ft_sess *sess;
        struct ft_tport *tport;

        mutex_lock(&ft_lport_lock);
        tport = rcu_dereference_protected(rdata->local_port->prov[FC_TYPE_FCP],
                                          lockdep_is_held(&ft_lport_lock));

        if (!tport) {
                mutex_unlock(&ft_lport_lock);
                return;
        }
        sess = ft_sess_delete(tport, rdata->ids.port_id);
        if (!sess) {
                mutex_unlock(&ft_lport_lock);
                return;
        }
        mutex_unlock(&ft_lport_lock);
        ft_close_sess(sess);            /* release from table */
        rdata->prli_count--;
        /* XXX TBD - clearing actions.  unit attn, see 4.10 */
}

/*
 * Handle incoming FCP request.
 * Caller has verified that the frame is type FCP.
 */
static void ft_recv(struct fc_lport *lport, struct fc_frame *fp)
{
        struct ft_sess *sess;
        u32 sid = fc_frame_sid(fp);

        pr_debug("sid %x\n", sid);

        sess = ft_sess_get(lport, sid);
        if (!sess) {
                pr_debug("sid %x sess lookup failed\n", sid);
                /* TBD XXX - if FCP_CMND, send PRLO */
                fc_frame_free(fp);
                return;
        }
        ft_recv_req(sess, fp);  /* must do ft_sess_put() */
}

/*
 * Provider ops for libfc.
 */
struct fc4_prov ft_prov = {
        .prli = ft_prli,
        .prlo = ft_prlo,
        .recv = ft_recv,
        .module = THIS_MODULE,
};