/*
 * 2007+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
 * All rights reserved.
 *
 * 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.
 */

#include <linux/buffer_head.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/connector.h>
#include <linux/dst.h>
#include <linux/device.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/socket.h>
#include <linux/slab.h>

#include <net/sock.h>

/*
 * Polling machinery.
 */

struct dst_poll_helper
{
        poll_table              pt;
        struct dst_state        *st;
};

static int dst_queue_wake(wait_queue_t *wait, unsigned mode, int sync, void *key)
{
        struct dst_state *st = container_of(wait, struct dst_state, wait);

        wake_up(&st->thread_wait);
        return 1;
}

static void dst_queue_func(struct file *file, wait_queue_head_t *whead,
                                 poll_table *pt)
{
        struct dst_state *st = container_of(pt, struct dst_poll_helper, pt)->st;

        st->whead = whead;
        init_waitqueue_func_entry(&st->wait, dst_queue_wake);
        add_wait_queue(whead, &st->wait);
}

void dst_poll_exit(struct dst_state *st)
{
        if (st->whead) {
                remove_wait_queue(st->whead, &st->wait);
                st->whead = NULL;
        }
}

int dst_poll_init(struct dst_state *st)
{
        struct dst_poll_helper ph;

        ph.st = st;
        init_poll_funcptr(&ph.pt, &dst_queue_func);

        st->socket->ops->poll(NULL, st->socket, &ph.pt);
        return 0;
}

/*
 * Header receiving function - may block.
 */
static int dst_data_recv_header(struct socket *sock,
                void *data, unsigned int size, int block)
{
        struct msghdr msg;
        struct kvec iov;
        int err;

        iov.iov_base = data;
        iov.iov_len = size;

        msg.msg_iov = (struct iovec *)&iov;
        msg.msg_iovlen = 1;
        msg.msg_name = NULL;
        msg.msg_namelen = 0;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags = (block)?MSG_WAITALL:MSG_DONTWAIT;

        err = kernel_recvmsg(sock, &msg, &iov, 1, iov.iov_len,
                        msg.msg_flags);
        if (err != size)
                return -1;

        return 0;
}

/*
 * Header sending function - may block.
 */
int dst_data_send_header(struct socket *sock,
                void *data, unsigned int size, int more)
{
        struct msghdr msg;
        struct kvec iov;
        int err;

        iov.iov_base = data;
        iov.iov_len = size;

        msg.msg_iov = (struct iovec *)&iov;
        msg.msg_iovlen = 1;
        msg.msg_name = NULL;
        msg.msg_namelen = 0;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags = MSG_WAITALL | (more)?MSG_MORE:0;

        err = kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len);
        if (err != size) {
                dprintk("%s: size: %u, more: %d, err: %d.\n",
                                __func__, size, more, err);
                return -1;
        }

        return 0;
}

/*
 * Block autoconfiguration: request size of the storage and permissions.
 */
static int dst_request_remote_config(struct dst_state *st)
{
        struct dst_node *n = st->node;
        int err = -EINVAL;
        struct dst_cmd *cmd = st->data;

        memset(cmd, 0, sizeof(struct dst_cmd));
        cmd->cmd = DST_CFG;

        dst_convert_cmd(cmd);

        err = dst_data_send_header(st->socket, cmd, sizeof(struct dst_cmd), 0);
        if (err)
                goto out;

        err = dst_data_recv_header(st->socket, cmd, sizeof(struct dst_cmd), 1);
        if (err)
                goto out;

        dst_convert_cmd(cmd);

        if (cmd->cmd != DST_CFG) {
                err = -EINVAL;
                dprintk("%s: checking result: cmd: %d, size reported: %llu.\n",
                        __func__, cmd->cmd, cmd->sector);
                goto out;
        }

        if (n->size != 0)
                n->size = min_t(loff_t, n->size, cmd->sector);
        else
                n->size = cmd->sector;

        n->info->size = n->size;
        st->permissions = cmd->rw;

out:
        dprintk("%s: n: %p, err: %d, size: %llu, permission: %x.\n",
                        __func__, n, err, n->size, st->permissions);
        return err;
}

/*
 * Socket machinery.
 */

#define DST_DEFAULT_TIMEO       20000

int dst_state_socket_create(struct dst_state *st)
{
        int err;
        struct socket *sock;
        struct dst_network_ctl *ctl = &st->ctl;

        err = sock_create(ctl->addr.sa_family, ctl->type, ctl->proto, &sock);
        if (err < 0)
                return err;

        sock->sk->sk_sndtimeo = sock->sk->sk_rcvtimeo =
                msecs_to_jiffies(DST_DEFAULT_TIMEO);
        sock->sk->sk_allocation = GFP_NOIO;

        st->socket = st->read_socket = sock;
        return 0;
}

void dst_state_socket_release(struct dst_state *st)
{
        dprintk("%s: st: %p, socket: %p, n: %p.\n",
                        __func__, st, st->socket, st->node);
        if (st->socket) {
                sock_release(st->socket);
                st->socket = NULL;
                st->read_socket = NULL;
        }
}

void dst_dump_addr(struct socket *sk, struct sockaddr *sa, char *str)
{
        if (sk->ops->family == AF_INET) {
                struct sockaddr_in *sin = (struct sockaddr_in *)sa;
                printk(KERN_INFO "%s %u.%u.%u.%u:%d.\n",
                        str, NIPQUAD(sin->sin_addr.s_addr), ntohs(sin->sin_port));
        } else if (sk->ops->family == AF_INET6) {
                struct sockaddr_in6 *sin = (struct sockaddr_in6 *)sa;
                printk(KERN_INFO "%s %pi6:%d",
                        str, &sin->sin6_addr, ntohs(sin->sin6_port));
        }
}

void dst_state_exit_connected(struct dst_state *st)
{
        if (st->socket) {
                dst_poll_exit(st);
                st->socket->ops->shutdown(st->socket, 2);

                dst_dump_addr(st->socket, (struct sockaddr *)&st->ctl.addr,
                                "Disconnected peer");
                dst_state_socket_release(st);
        }
}

static int dst_state_init_connected(struct dst_state *st)
{
        int err;
        struct dst_network_ctl *ctl = &st->ctl;

        err = dst_state_socket_create(st);
        if (err)
                goto err_out_exit;

        err = kernel_connect(st->socket, (struct sockaddr *)&st->ctl.addr,
                        st->ctl.addr.sa_data_len, 0);
        if (err)
                goto err_out_release;

        err = dst_poll_init(st);
        if (err)
                goto err_out_release;

        dst_dump_addr(st->socket, (struct sockaddr *)&ctl->addr,
                        "Connected to peer");

        return 0;

err_out_release:
        dst_state_socket_release(st);
err_out_exit:
        return err;
}

/*
 * State reset is used to reconnect to the remote peer.
 * May fail, but who cares, we will try again later.
 */
static void inline dst_state_reset_nolock(struct dst_state *st)
{
        dst_state_exit_connected(st);
        dst_state_init_connected(st);
}

static void inline dst_state_reset(struct dst_state *st)
{
        dst_state_lock(st);
        dst_state_reset_nolock(st);
        dst_state_unlock(st);
}

/*
 * Basic network sending/receiving functions.
 * Blocked mode is used.
 */
static int dst_data_recv_raw(struct dst_state *st, void *buf, u64 size)
{
        struct msghdr msg;
        struct kvec iov;
        int err;

        BUG_ON(!size);

        iov.iov_base = buf;
        iov.iov_len = size;

        msg.msg_iov = (struct iovec *)&iov;
        msg.msg_iovlen = 1;
        msg.msg_name = NULL;
        msg.msg_namelen = 0;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags = MSG_DONTWAIT;

        err = kernel_recvmsg(st->socket, &msg, &iov, 1, iov.iov_len,
                        msg.msg_flags);
        if (err <= 0) {
                dprintk("%s: failed to recv data: size: %llu, err: %d.\n",
                                __func__, size, err);
                if (err == 0)
                        err = -ECONNRESET;

                dst_state_exit_connected(st);
        }

        return err;
}

/*
 * Ping command to early detect failed nodes.
 */
static int dst_send_ping(struct dst_state *st)
{
        struct dst_cmd *cmd = st->data;
        int err = -ECONNRESET;

        dst_state_lock(st);
        if (st->socket) {
                memset(cmd, 0, sizeof(struct dst_cmd));

                cmd->cmd = __cpu_to_be32(DST_PING);

                err = dst_data_send_header(st->socket, cmd, sizeof(struct dst_cmd), 0);
        }
        dprintk("%s: st: %p, socket: %p, err: %d.\n", __func__, st, st->socket, err);
        dst_state_unlock(st);

        return err;
}

/*
 * Receiving function, which should either return error or read
 * whole block request. If there was no traffic for a one second,
 * send a ping, since remote node may die.
 */
int dst_data_recv(struct dst_state *st, void *data, unsigned int size)
{
        unsigned int revents = 0;
        unsigned int err_mask = POLLERR | POLLHUP | POLLRDHUP;
        unsigned int mask = err_mask | POLLIN;
        struct dst_node *n = st->node;
        int err = 0;

        while (size && !err) {
                revents = dst_state_poll(st);

                if (!(revents & mask)) {
                        DEFINE_WAIT(wait);

                        for (;;) {
                                prepare_to_wait(&st->thread_wait, &wait,
                                                TASK_INTERRUPTIBLE);
                                if (!n->trans_scan_timeout || st->need_exit)
                                        break;

                                revents = dst_state_poll(st);

                                if (revents & mask)
                                        break;

                                if (signal_pending(current))
                                        break;

                                if (!schedule_timeout(HZ)) {
                                        err = dst_send_ping(st);
                                        if (err)
                                                return err;
                                }

                                continue;
                        }
                        finish_wait(&st->thread_wait, &wait);
                }

                err = -ECONNRESET;
                dst_state_lock(st);

                if (            st->socket &&
                                (st->read_socket == st->socket) &&
                                (revents & POLLIN)) {
                        err = dst_data_recv_raw(st, data, size);
                        if (err > 0) {
                                data += err;
                                size -= err;
                                err = 0;
                        }
                }

                if (revents & err_mask || !st->socket) {
                        dprintk("%s: revents: %x, socket: %p, size: %u, err: %d.\n",
                                        __func__, revents, st->socket, size, err);
                        err = -ECONNRESET;
                }

                dst_state_unlock(st);

                if (!n->trans_scan_timeout)
                        err = -ENODEV;
        }

        return err;
}

/*
 * Send block autoconf reply.
 */
static int dst_process_cfg(struct dst_state *st)
{
        struct dst_node *n = st->node;
        struct dst_cmd *cmd = st->data;
        int err;

        cmd->sector = n->size;
        cmd->rw = st->permissions;

        dst_convert_cmd(cmd);

        dst_state_lock(st);
        err = dst_data_send_header(st->socket, cmd, sizeof(struct dst_cmd), 0);
        dst_state_unlock(st);

        return err;
}

/*
 * Receive block IO from the network.
 */
static int dst_recv_bio(struct dst_state *st, struct bio *bio, unsigned int total_size)
{
        struct bio_vec *bv;
        int i, err;
        void *data;
        unsigned int sz;

        bio_for_each_segment(bv, bio, i) {
                sz = min(total_size, bv->bv_len);

                dprintk("%s: bio: %llu/%u, total: %u, len: %u, sz: %u, off: %u.\n",
                        __func__, (u64)bio->bi_sector, bio->bi_size, total_size,
                        bv->bv_len, sz, bv->bv_offset);

                data = kmap(bv->bv_page) + bv->bv_offset;
                err = dst_data_recv(st, data, sz);
                kunmap(bv->bv_page);

                bv->bv_len = sz;

                if (err)
                        return err;

                total_size -= sz;
                if (total_size == 0)
                        break;
        }

        return 0;
}

/*
 * Our block IO has just completed and arrived: get it.
 */
static int dst_process_io_response(struct dst_state *st)
{
        struct dst_node *n = st->node;
        struct dst_cmd *cmd = st->data;
        struct dst_trans *t;
        int err = 0;
        struct bio *bio;

        mutex_lock(&n->trans_lock);
        t = dst_trans_search(n, cmd->id);
        mutex_unlock(&n->trans_lock);

        if (!t)
                goto err_out_exit;

        bio = t->bio;

        dprintk("%s: bio: %llu/%u, cmd_size: %u, csize: %u, dir: %lu.\n",
                __func__, (u64)bio->bi_sector, bio->bi_size, cmd->size,
                cmd->csize, bio_data_dir(bio));

        if (bio_data_dir(bio) == READ) {
                if (bio->bi_size != cmd->size - cmd->csize)
                        goto err_out_exit;

                if (dst_need_crypto(n)) {
                        err = dst_recv_cdata(st, t->cmd.hash);
                        if (err)
                                goto err_out_exit;
                }

                err = dst_recv_bio(st, t->bio, bio->bi_size);
                if (err)
                        goto err_out_exit;

                if (dst_need_crypto(n))
                        return dst_trans_crypto(t);
        } else {
                err = -EBADMSG;
                if (cmd->size || cmd->csize)
                        goto err_out_exit;
        }

        dst_trans_remove(t);
        dst_trans_put(t);

        return 0;

err_out_exit:
        return err;
}

/*
 * Receive crypto data.
 */
int dst_recv_cdata(struct dst_state *st, void *cdata)
{
        struct dst_cmd *cmd = st->data;
        struct dst_node *n = st->node;
        struct dst_crypto_ctl *c = &n->crypto;
        int err;

        if (cmd->csize != c->crypto_attached_size) {
                dprintk("%s: cmd: cmd: %u, sector: %llu, size: %u, "
                                "csize: %u != digest size %u.\n",
                                __func__, cmd->cmd, cmd->sector, cmd->size,
                                cmd->csize, c->crypto_attached_size);
                err = -EINVAL;
                goto err_out_exit;
        }

        err = dst_data_recv(st, cdata, cmd->csize);
        if (err)
                goto err_out_exit;

        cmd->size -= cmd->csize;
        return 0;

err_out_exit:
        return err;
}

/*
 * Receive the command and start its processing.
 */
static int dst_recv_processing(struct dst_state *st)
{
        int err = -EINTR;
        struct dst_cmd *cmd = st->data;

        /*
         * If socket will be reset after this statement, then
         * dst_data_recv() will just fail and loop will
         * start again, so it can be done without any locks.
         *
         * st->read_socket is needed to prevents state machine
         * breaking between this data reading and subsequent one
         * in protocol specific functions during connection reset.
         * In case of reset we have to read next command and do
         * not expect data for old command to magically appear in
         * new connection.
         */
        st->read_socket = st->socket;
        err = dst_data_recv(st, cmd, sizeof(struct dst_cmd));
        if (err)
                goto out_exit;

        dst_convert_cmd(cmd);

        dprintk("%s: cmd: %u, size: %u, csize: %u, id: %llu, "
                        "sector: %llu, flags: %llx, rw: %llx.\n",
                        __func__, cmd->cmd, cmd->size,
                        cmd->csize, cmd->id, cmd->sector,
                        cmd->flags, cmd->rw);

        /*
         * This should catch protocol breakage and random garbage instead of commands.
         */
        if (unlikely(cmd->csize > st->size - sizeof(struct dst_cmd))) {
                err = -EBADMSG;
                goto out_exit;
        }

        err = -EPROTO;
        switch (cmd->cmd) {
                case DST_IO_RESPONSE:
                        err = dst_process_io_response(st);
                        break;
                case DST_IO:
                        err = dst_process_io(st);
                        break;
                case DST_CFG:
                        err = dst_process_cfg(st);
                        break;
                case DST_PING:
                        err = 0;
                        break;
                default:
                        break;
        }

out_exit:
        return err;
}

/*
 * Receiving thread. For the client node we should try to reconnect,
 * for accepted client we just drop the state and expect it to reconnect.
 */
static int dst_recv(void *init_data, void *schedule_data)
{
        struct dst_state *st = schedule_data;
        struct dst_node *n = init_data;
        int err = 0;

        dprintk("%s: start st: %p, n: %p, scan: %lu, need_exit: %d.\n",
                        __func__, st, n, n->trans_scan_timeout, st->need_exit);

        while (n->trans_scan_timeout && !st->need_exit) {
                err = dst_recv_processing(st);
                if (err < 0) {
                        if (!st->ctl.type)
                                break;

                        if (!n->trans_scan_timeout || st->need_exit)
                                break;

                        dst_state_reset(st);
                        msleep(1000);
                }
        }

        st->need_exit = 1;
        wake_up(&st->thread_wait);

        dprintk("%s: freeing receiving socket st: %p.\n", __func__, st);
        dst_state_lock(st);
        dst_state_exit_connected(st);
        dst_state_unlock(st);
        dst_state_put(st);

        dprintk("%s: freed receiving socket st: %p.\n", __func__, st);

        return err;
}

/*
 * Network state dies here and borns couple of lines below.
 * This object is the main network state processing engine:
 * sending, receiving, reconnections, all network related
 * tasks are handled on behalf of the state.
 */
static void dst_state_free(struct dst_state *st)
{
        dprintk("%s: st: %p.\n", __func__, st);
        if (st->cleanup)
                st->cleanup(st);
        kfree(st->data);
        kfree(st);
}

struct dst_state *dst_state_alloc(struct dst_node *n)
{
        struct dst_state *st;
        int err = -ENOMEM;

        st = kzalloc(sizeof(struct dst_state), GFP_KERNEL);
        if (!st)
                goto err_out_exit;

        st->node = n;
        st->need_exit = 0;

        st->size = PAGE_SIZE;
        st->data = kmalloc(st->size, GFP_KERNEL);
        if (!st->data)
                goto err_out_free;

        spin_lock_init(&st->request_lock);
        INIT_LIST_HEAD(&st->request_list);

        mutex_init(&st->state_lock);
        init_waitqueue_head(&st->thread_wait);

        /*
         * One for processing thread, another one for node itself.
         */
        atomic_set(&st->refcnt, 2);

        dprintk("%s: st: %p, n: %p.\n", __func__, st, st->node);

        return st;

err_out_free:
        kfree(st);
err_out_exit:
        return ERR_PTR(err);
}

int dst_state_schedule_receiver(struct dst_state *st)
{
        return thread_pool_schedule_private(st->node->pool, dst_thread_setup,
                        dst_recv, st, MAX_SCHEDULE_TIMEOUT, st->node);
}

/*
 * Initialize client's connection to the remote peer: allocate state,
 * connect and perform block IO autoconfiguration.
 */
int dst_node_init_connected(struct dst_node *n, struct dst_network_ctl *r)
{
        struct dst_state *st;
        int err = -ENOMEM;

        st = dst_state_alloc(n);
        if (IS_ERR(st)) {
                err = PTR_ERR(st);
                goto err_out_exit;
        }
        memcpy(&st->ctl, r, sizeof(struct dst_network_ctl));

        err = dst_state_init_connected(st);
        if (err)
                goto err_out_free_data;

        err = dst_request_remote_config(st);
        if (err)
                goto err_out_exit_connected;
        n->state = st;

        err = dst_state_schedule_receiver(st);
        if (err)
                goto err_out_exit_connected;

        return 0;

err_out_exit_connected:
        dst_state_exit_connected(st);
err_out_free_data:
        dst_state_free(st);
err_out_exit:
        n->state = NULL;
        return err;
}

void dst_state_put(struct dst_state *st)
{
        dprintk("%s: st: %p, refcnt: %d.\n",
                        __func__, st, atomic_read(&st->refcnt));
        if (atomic_dec_and_test(&st->refcnt))
                dst_state_free(st);
}

/*
 * Send block IO to the network one by one using zero-copy ->sendpage().
 */
int dst_send_bio(struct dst_state *st, struct dst_cmd *cmd, struct bio *bio)
{
        struct bio_vec *bv;
        struct dst_crypto_ctl *c = &st->node->crypto;
        int err, i = 0;
        int flags = MSG_WAITALL;

        err = dst_data_send_header(st->socket, cmd,
                sizeof(struct dst_cmd) + c->crypto_attached_size, bio->bi_vcnt);
        if (err)
                goto err_out_exit;

        bio_for_each_segment(bv, bio, i) {
                if (i < bio->bi_vcnt - 1)
                        flags |= MSG_MORE;

                err = kernel_sendpage(st->socket, bv->bv_page, bv->bv_offset,
                                bv->bv_len, flags);
                if (err <= 0)
                        goto err_out_exit;
        }

        return 0;

err_out_exit:
        dprintk("%s: %d/%d, flags: %x, err: %d.\n",
                        __func__, i, bio->bi_vcnt, flags, err);
        return err;
}

/*
 * Send transaction to the remote peer.
 */
int dst_trans_send(struct dst_trans *t)
{
        int err;
        struct dst_state *st = t->n->state;
        struct bio *bio = t->bio;

        dst_convert_cmd(&t->cmd);

        dst_state_lock(st);
        if (!st->socket) {
                err = dst_state_init_connected(st);
                if (err)
                        goto err_out_unlock;
        }

        if (bio_data_dir(bio) == WRITE) {
                err = dst_send_bio(st, &t->cmd, t->bio);
        } else {
                err = dst_data_send_header(st->socket, &t->cmd,
                                sizeof(struct dst_cmd), 0);
        }
        if (err)
                goto err_out_reset;

        dst_state_unlock(st);
        return 0;

err_out_reset:
        dst_state_reset_nolock(st);
err_out_unlock:
        dst_state_unlock(st);

        return err;
}