/*
 *  scsi_netlink.c  - SCSI Transport Netlink Interface
 *
 *  Copyright (C) 2006   James Smart, Emulex Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */
#include <linux/time.h>
#include <linux/jiffies.h>
#include <linux/security.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/netlink.h>

#include <scsi/scsi_netlink.h>
#include "scsi_priv.h"

struct sock *scsi_nl_sock = NULL;
EXPORT_SYMBOL_GPL(scsi_nl_sock);

static DEFINE_SPINLOCK(scsi_nl_lock);
static struct list_head scsi_nl_drivers;

static u32      scsi_nl_state;
#define STATE_EHANDLER_BSY              0x00000001

struct scsi_nl_transport {
        int (*msg_handler)(struct sk_buff *);
        void (*event_handler)(struct notifier_block *, unsigned long, void *);
        unsigned int refcnt;
        int flags;
};

/* flags values (bit flags) */
#define HANDLER_DELETING                0x1

static struct scsi_nl_transport transports[SCSI_NL_MAX_TRANSPORTS] =
        { {NULL, }, };


struct scsi_nl_drvr {
        struct list_head next;
        int (*dmsg_handler)(struct Scsi_Host *shost, void *payload,
                                 u32 len, u32 pid);
        void (*devt_handler)(struct notifier_block *nb,
                                 unsigned long event, void *notify_ptr);
        struct scsi_host_template *hostt;
        u64 vendor_id;
        unsigned int refcnt;
        int flags;
};



/**
 * scsi_nl_rcv_msg - Receive message handler.
 * @skb:                socket receive buffer
 *
 * Description: Extracts message from a receive buffer.
 *    Validates message header and calls appropriate transport message handler
 *
 *
 **/
static void
scsi_nl_rcv_msg(struct sk_buff *skb)
{
        struct nlmsghdr *nlh;
        struct scsi_nl_hdr *hdr;
        unsigned long flags;
        u32 rlen;
        int err, tport;

        while (skb->len >= NLMSG_SPACE(0)) {
                err = 0;

                nlh = nlmsg_hdr(skb);
                if ((nlh->nlmsg_len < (sizeof(*nlh) + sizeof(*hdr))) ||
                    (skb->len < nlh->nlmsg_len)) {
                        printk(KERN_WARNING "%s: discarding partial skb\n",
                                 __func__);
                        return;
                }

                rlen = NLMSG_ALIGN(nlh->nlmsg_len);
                if (rlen > skb->len)
                        rlen = skb->len;

                if (nlh->nlmsg_type != SCSI_TRANSPORT_MSG) {
                        err = -EBADMSG;
                        goto next_msg;
                }

                hdr = NLMSG_DATA(nlh);
                if ((hdr->version != SCSI_NL_VERSION) ||
                    (hdr->magic != SCSI_NL_MAGIC)) {
                        err = -EPROTOTYPE;
                        goto next_msg;
                }

                if (security_netlink_recv(skb, CAP_SYS_ADMIN)) {
                        err = -EPERM;
                        goto next_msg;
                }

                if (nlh->nlmsg_len < (sizeof(*nlh) + hdr->msglen)) {
                        printk(KERN_WARNING "%s: discarding partial message\n",
                                 __func__);
                        goto next_msg;
                }

                /*
                 * Deliver message to the appropriate transport
                 */
                spin_lock_irqsave(&scsi_nl_lock, flags);

                tport = hdr->transport;
                if ((tport < SCSI_NL_MAX_TRANSPORTS) &&
                    !(transports[tport].flags & HANDLER_DELETING) &&
                    (transports[tport].msg_handler)) {
                        transports[tport].refcnt++;
                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
                        err = transports[tport].msg_handler(skb);
                        spin_lock_irqsave(&scsi_nl_lock, flags);
                        transports[tport].refcnt--;
                } else
                        err = -ENOENT;

                spin_unlock_irqrestore(&scsi_nl_lock, flags);

next_msg:
                if ((err) || (nlh->nlmsg_flags & NLM_F_ACK))
                        netlink_ack(skb, nlh, err);

                skb_pull(skb, rlen);
        }
}


/**
 * scsi_nl_rcv_event - Event handler for a netlink socket.
 * @this:               event notifier block
 * @event:              event type
 * @ptr:                event payload
 *
 **/
static int
scsi_nl_rcv_event(struct notifier_block *this, unsigned long event, void *ptr)
{
        struct netlink_notify *n = ptr;
        struct scsi_nl_drvr *driver;
        unsigned long flags;
        int tport;

        if (n->protocol != NETLINK_SCSITRANSPORT)
                return NOTIFY_DONE;

        spin_lock_irqsave(&scsi_nl_lock, flags);
        scsi_nl_state |= STATE_EHANDLER_BSY;

        /*
         * Pass event on to any transports that may be listening
         */
        for (tport = 0; tport < SCSI_NL_MAX_TRANSPORTS; tport++) {
                if (!(transports[tport].flags & HANDLER_DELETING) &&
                    (transports[tport].event_handler)) {
                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
                        transports[tport].event_handler(this, event, ptr);
                        spin_lock_irqsave(&scsi_nl_lock, flags);
                }
        }

        /*
         * Pass event on to any drivers that may be listening
         */
        list_for_each_entry(driver, &scsi_nl_drivers, next) {
                if (!(driver->flags & HANDLER_DELETING) &&
                    (driver->devt_handler)) {
                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
                        driver->devt_handler(this, event, ptr);
                        spin_lock_irqsave(&scsi_nl_lock, flags);
                }
        }

        scsi_nl_state &= ~STATE_EHANDLER_BSY;
        spin_unlock_irqrestore(&scsi_nl_lock, flags);

        return NOTIFY_DONE;
}

static struct notifier_block scsi_netlink_notifier = {
        .notifier_call  = scsi_nl_rcv_event,
};


/*
 * GENERIC SCSI transport receive and event handlers
 */

/**
 * scsi_generic_msg_handler - receive message handler for GENERIC transport messages
 * @skb:                socket receive buffer
 **/
static int
scsi_generic_msg_handler(struct sk_buff *skb)
{
        struct nlmsghdr *nlh = nlmsg_hdr(skb);
        struct scsi_nl_hdr *snlh = NLMSG_DATA(nlh);
        struct scsi_nl_drvr *driver;
        struct Scsi_Host *shost;
        unsigned long flags;
        int err = 0, match, pid;

        pid = NETLINK_CREDS(skb)->pid;

        switch (snlh->msgtype) {
        case SCSI_NL_SHOST_VENDOR:
                {
                struct scsi_nl_host_vendor_msg *msg = NLMSG_DATA(nlh);

                /* Locate the driver that corresponds to the message */
                spin_lock_irqsave(&scsi_nl_lock, flags);
                match = 0;
                list_for_each_entry(driver, &scsi_nl_drivers, next) {
                        if (driver->vendor_id == msg->vendor_id) {
                                match = 1;
                                break;
                        }
                }

                if ((!match) || (!driver->dmsg_handler)) {
                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
                        err = -ESRCH;
                        goto rcv_exit;
                }

                if (driver->flags & HANDLER_DELETING) {
                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
                        err = -ESHUTDOWN;
                        goto rcv_exit;
                }

                driver->refcnt++;
                spin_unlock_irqrestore(&scsi_nl_lock, flags);


                /* if successful, scsi_host_lookup takes a shost reference */
                shost = scsi_host_lookup(msg->host_no);
                if (!shost) {
                        err = -ENODEV;
                        goto driver_exit;
                }

                /* is this host owned by the vendor ? */
                if (shost->hostt != driver->hostt) {
                        err = -EINVAL;
                        goto vendormsg_put;
                }

                /* pass message on to the driver */
                err = driver->dmsg_handler(shost, (void *)&msg[1],
                                         msg->vmsg_datalen, pid);

vendormsg_put:
                /* release reference by scsi_host_lookup */
                scsi_host_put(shost);

driver_exit:
                /* release our own reference on the registration object */
                spin_lock_irqsave(&scsi_nl_lock, flags);
                driver->refcnt--;
                spin_unlock_irqrestore(&scsi_nl_lock, flags);
                break;
                }

        default:
                err = -EBADR;
                break;
        }

rcv_exit:
        if (err)
                printk(KERN_WARNING "%s: Msgtype %d failed - err %d\n",
                         __func__, snlh->msgtype, err);
        return err;
}


/**
 * scsi_nl_add_transport -
 *    Registers message and event handlers for a transport. Enables
 *    receipt of netlink messages and events to a transport.
 *
 * @tport:              transport registering handlers
 * @msg_handler:        receive message handler callback
 * @event_handler:      receive event handler callback
 **/
int
scsi_nl_add_transport(u8 tport,
        int (*msg_handler)(struct sk_buff *),
        void (*event_handler)(struct notifier_block *, unsigned long, void *))
{
        unsigned long flags;
        int err = 0;

        if (tport >= SCSI_NL_MAX_TRANSPORTS)
                return -EINVAL;

        spin_lock_irqsave(&scsi_nl_lock, flags);

        if (scsi_nl_state & STATE_EHANDLER_BSY) {
                spin_unlock_irqrestore(&scsi_nl_lock, flags);
                msleep(1);
                spin_lock_irqsave(&scsi_nl_lock, flags);
        }

        if (transports[tport].msg_handler || transports[tport].event_handler) {
                err = -EALREADY;
                goto register_out;
        }

        transports[tport].msg_handler = msg_handler;
        transports[tport].event_handler = event_handler;
        transports[tport].flags = 0;
        transports[tport].refcnt = 0;

register_out:
        spin_unlock_irqrestore(&scsi_nl_lock, flags);

        return err;
}
EXPORT_SYMBOL_GPL(scsi_nl_add_transport);


/**
 * scsi_nl_remove_transport -
 *    Disable transport receiption of messages and events
 *
 * @tport:              transport deregistering handlers
 *
 **/
void
scsi_nl_remove_transport(u8 tport)
{
        unsigned long flags;

        spin_lock_irqsave(&scsi_nl_lock, flags);
        if (scsi_nl_state & STATE_EHANDLER_BSY) {
                spin_unlock_irqrestore(&scsi_nl_lock, flags);
                msleep(1);
                spin_lock_irqsave(&scsi_nl_lock, flags);
        }

        if (tport < SCSI_NL_MAX_TRANSPORTS) {
                transports[tport].flags |= HANDLER_DELETING;

                while (transports[tport].refcnt != 0) {
                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
                        schedule_timeout_uninterruptible(HZ/4);
                        spin_lock_irqsave(&scsi_nl_lock, flags);
                }
                transports[tport].msg_handler = NULL;
                transports[tport].event_handler = NULL;
                transports[tport].flags = 0;
        }

        spin_unlock_irqrestore(&scsi_nl_lock, flags);

        return;
}
EXPORT_SYMBOL_GPL(scsi_nl_remove_transport);


/**
 * scsi_nl_add_driver -
 *    A driver is registering its interfaces for SCSI netlink messages
 *
 * @vendor_id:          A unique identification value for the driver.
 * @hostt:              address of the driver's host template. Used
 *                      to verify an shost is bound to the driver
 * @nlmsg_handler:      receive message handler callback
 * @nlevt_handler:      receive event handler callback
 *
 * Returns:
 *   0 on Success
 *   error result otherwise
 **/
int
scsi_nl_add_driver(u64 vendor_id, struct scsi_host_template *hostt,
        int (*nlmsg_handler)(struct Scsi_Host *shost, void *payload,
                                 u32 len, u32 pid),
        void (*nlevt_handler)(struct notifier_block *nb,
                                 unsigned long event, void *notify_ptr))
{
        struct scsi_nl_drvr *driver;
        unsigned long flags;

        driver = kzalloc(sizeof(*driver), GFP_KERNEL);
        if (unlikely(!driver)) {
                printk(KERN_ERR "%s: allocation failure\n", __func__);
                return -ENOMEM;
        }

        driver->dmsg_handler = nlmsg_handler;
        driver->devt_handler = nlevt_handler;
        driver->hostt = hostt;
        driver->vendor_id = vendor_id;

        spin_lock_irqsave(&scsi_nl_lock, flags);
        if (scsi_nl_state & STATE_EHANDLER_BSY) {
                spin_unlock_irqrestore(&scsi_nl_lock, flags);
                msleep(1);
                spin_lock_irqsave(&scsi_nl_lock, flags);
        }
        list_add_tail(&driver->next, &scsi_nl_drivers);
        spin_unlock_irqrestore(&scsi_nl_lock, flags);

        return 0;
}
EXPORT_SYMBOL_GPL(scsi_nl_add_driver);


/**
 * scsi_nl_remove_driver -
 *    An driver is unregistering with the SCSI netlink messages
 *
 * @vendor_id:          The unique identification value for the driver.
 **/
void
scsi_nl_remove_driver(u64 vendor_id)
{
        struct scsi_nl_drvr *driver;
        unsigned long flags;

        spin_lock_irqsave(&scsi_nl_lock, flags);
        if (scsi_nl_state & STATE_EHANDLER_BSY) {
                spin_unlock_irqrestore(&scsi_nl_lock, flags);
                msleep(1);
                spin_lock_irqsave(&scsi_nl_lock, flags);
        }

        list_for_each_entry(driver, &scsi_nl_drivers, next) {
                if (driver->vendor_id == vendor_id) {
                        driver->flags |= HANDLER_DELETING;
                        while (driver->refcnt != 0) {
                                spin_unlock_irqrestore(&scsi_nl_lock, flags);
                                schedule_timeout_uninterruptible(HZ/4);
                                spin_lock_irqsave(&scsi_nl_lock, flags);
                        }
                        list_del(&driver->next);
                        kfree(driver);
                        spin_unlock_irqrestore(&scsi_nl_lock, flags);
                        return;
                }
        }

        spin_unlock_irqrestore(&scsi_nl_lock, flags);

        printk(KERN_ERR "%s: removal of driver failed - vendor_id 0x%llx\n",
               __func__, (unsigned long long)vendor_id);
        return;
}
EXPORT_SYMBOL_GPL(scsi_nl_remove_driver);


/**
 * scsi_netlink_init - Called by SCSI subsystem to initialize
 *      the SCSI transport netlink interface
 *
 **/
void
scsi_netlink_init(void)
{
        int error;

        INIT_LIST_HEAD(&scsi_nl_drivers);

        error = netlink_register_notifier(&scsi_netlink_notifier);
        if (error) {
                printk(KERN_ERR "%s: register of event handler failed - %d\n",
                                __func__, error);
                return;
        }

        scsi_nl_sock = netlink_kernel_create(&init_net, NETLINK_SCSITRANSPORT,
                                SCSI_NL_GRP_CNT, scsi_nl_rcv_msg, NULL,
                                THIS_MODULE);
        if (!scsi_nl_sock) {
                printk(KERN_ERR "%s: register of recieve handler failed\n",
                                __func__);
                netlink_unregister_notifier(&scsi_netlink_notifier);
                return;
        }

        /* Register the entry points for the generic SCSI transport */
        error = scsi_nl_add_transport(SCSI_NL_TRANSPORT,
                                scsi_generic_msg_handler, NULL);
        if (error)
                printk(KERN_ERR "%s: register of GENERIC transport handler"
                                "  failed - %d\n", __func__, error);
        return;
}


/**
 * scsi_netlink_exit - Called by SCSI subsystem to disable the SCSI transport netlink interface
 *
 **/
void
scsi_netlink_exit(void)
{
        scsi_nl_remove_transport(SCSI_NL_TRANSPORT);

        if (scsi_nl_sock) {
                netlink_kernel_release(scsi_nl_sock);
                netlink_unregister_notifier(&scsi_netlink_notifier);
        }

        return;
}


/*
 * Exported Interfaces
 */

/**
 * scsi_nl_send_transport_msg -
 *    Generic function to send a single message from a SCSI transport to
 *    a single process
 *
 * @pid:                receiving pid
 * @hdr:                message payload
 *
 **/
void
scsi_nl_send_transport_msg(u32 pid, struct scsi_nl_hdr *hdr)
{
        struct sk_buff *skb;
        struct nlmsghdr *nlh;
        const char *fn;
        char *datab;
        u32 len, skblen;
        int err;

        if (!scsi_nl_sock) {
                err = -ENOENT;
                fn = "netlink socket";
                goto msg_fail;
        }

        len = NLMSG_SPACE(hdr->msglen);
        skblen = NLMSG_SPACE(len);

        skb = alloc_skb(skblen, GFP_KERNEL);
        if (!skb) {
                err = -ENOBUFS;
                fn = "alloc_skb";
                goto msg_fail;
        }

        nlh = nlmsg_put(skb, pid, 0, SCSI_TRANSPORT_MSG, len - sizeof(*nlh), 0);
        if (!nlh) {
                err = -ENOBUFS;
                fn = "nlmsg_put";
                goto msg_fail_skb;
        }
        datab = NLMSG_DATA(nlh);
        memcpy(datab, hdr, hdr->msglen);

        err = nlmsg_unicast(scsi_nl_sock, skb, pid);
        if (err < 0) {
                fn = "nlmsg_unicast";
                /* nlmsg_unicast already kfree_skb'd */
                goto msg_fail;
        }

        return;

msg_fail_skb:
        kfree_skb(skb);
msg_fail:
        printk(KERN_WARNING
                "%s: Dropped Message : pid %d Transport %d, msgtype x%x, "
                "msglen %d: %s : err %d\n",
                __func__, pid, hdr->transport, hdr->msgtype, hdr->msglen,
                fn, err);
        return;
}
EXPORT_SYMBOL_GPL(scsi_nl_send_transport_msg);


/**
 * scsi_nl_send_vendor_msg - called to send a shost vendor unique message
 *                      to a specific process id.
 *
 * @pid:                process id of the receiver
 * @host_no:            host # sending the message
 * @vendor_id:          unique identifier for the driver's vendor
 * @data_len:           amount, in bytes, of vendor unique payload data
 * @data_buf:           pointer to vendor unique data buffer
 *
 * Returns:
 *   0 on successful return
 *   otherwise, failing error code
 *
 * Notes:
 *      This routine assumes no locks are held on entry.
 */
int
scsi_nl_send_vendor_msg(u32 pid, unsigned short host_no, u64 vendor_id,
                         char *data_buf, u32 data_len)
{
        struct sk_buff *skb;
        struct nlmsghdr *nlh;
        struct scsi_nl_host_vendor_msg *msg;
        u32 len, skblen;
        int err;

        if (!scsi_nl_sock) {
                err = -ENOENT;
                goto send_vendor_fail;
        }

        len = SCSI_NL_MSGALIGN(sizeof(*msg) + data_len);
        skblen = NLMSG_SPACE(len);

        skb = alloc_skb(skblen, GFP_KERNEL);
        if (!skb) {
                err = -ENOBUFS;
                goto send_vendor_fail;
        }

        nlh = nlmsg_put(skb, 0, 0, SCSI_TRANSPORT_MSG,
                                skblen - sizeof(*nlh), 0);
        if (!nlh) {
                err = -ENOBUFS;
                goto send_vendor_fail_skb;
        }
        msg = NLMSG_DATA(nlh);

        INIT_SCSI_NL_HDR(&msg->snlh, SCSI_NL_TRANSPORT,
                                SCSI_NL_SHOST_VENDOR, len);
        msg->vendor_id = vendor_id;
        msg->host_no = host_no;
        msg->vmsg_datalen = data_len;   /* bytes */
        memcpy(&msg[1], data_buf, data_len);

        err = nlmsg_unicast(scsi_nl_sock, skb, pid);
        if (err)
                /* nlmsg_multicast already kfree_skb'd */
                goto send_vendor_fail;

        return 0;

send_vendor_fail_skb:
        kfree_skb(skb);
send_vendor_fail:
        printk(KERN_WARNING
                "%s: Dropped SCSI Msg : host %d vendor_unique - err %d\n",
                __func__, host_no, err);
        return err;
}
EXPORT_SYMBOL(scsi_nl_send_vendor_msg);