/*
 * 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/blkdev.h>
#include <linux/bio.h>
#include <linux/dst.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/socket.h>

#include <net/sock.h>

/*
 * Export bioset is used for server block IO requests.
 */
static struct bio_set *dst_bio_set;

int __init dst_export_init(void)
{
	int err = -ENOMEM;

	dst_bio_set = bioset_create(32, sizeof(struct dst_export_priv));
	if (!dst_bio_set)
		goto err_out_exit;

	return 0;

err_out_exit:
	return err;
}

void dst_export_exit(void)
{
	bioset_free(dst_bio_set);
}

/*
 * When client connects and autonegotiates with the server node,
 * its permissions are checked in a security attributes and sent
 * back.
 */
static unsigned int dst_check_permissions(struct dst_state *main, struct dst_state *st)
{
	struct dst_node *n = main->node;
	struct dst_secure *sentry;
	struct dst_secure_user *s;
	struct saddr *sa = &st->ctl.addr;
	unsigned int perm = 0;

	mutex_lock(&n->security_lock);
	list_for_each_entry(sentry, &n->security_list, sec_entry) {
		s = &sentry->sec;

		if (s->addr.sa_family != sa->sa_family)
			continue;

		if (s->addr.sa_data_len != sa->sa_data_len)
			continue;

		/*
		 * This '2' below is a port field. This may be very wrong to do
		 * in atalk for example though. If there will be any need to extent
		 * protocol to something else, I can create per-family helpers and
		 * use them instead of this memcmp.
		 */
		if (memcmp(s->addr.sa_data + 2, sa->sa_data + 2,
					sa->sa_data_len - 2))
			continue;

		perm = s->permissions;
	}
	mutex_unlock(&n->security_lock);

	return perm;
}

/*
 * Accept new client: allocate appropriate network state and check permissions.
 */
static struct dst_state *dst_accept_client(struct dst_state *st)
{
	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;
	struct socket *sock = NULL;
	struct dst_state *new;

	while (!err && !sock) {
		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;

				/*
				 * Magic HZ? Polling check above is not safe in
				 * all cases (like socket reset in BH context),
				 * so it is simpler just to postpone it to the
				 * process context instead of implementing special
				 * locking there.
				 */
				schedule_timeout(HZ);
			}
			finish_wait(&st->thread_wait, &wait);
		}

		err = -ECONNRESET;
		dst_state_lock(st);

		dprintk("%s: st: %p, revents: %x [err: %d, in: %d].\n",
			__func__, st, revents, revents & err_mask,
			revents & POLLIN);

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

		if (!n->trans_scan_timeout || st->need_exit)
			err = -ENODEV;

		if (st->socket && (revents & POLLIN))
			err = kernel_accept(st->socket, &sock, 0);

		dst_state_unlock(st);
	}

	if (err)
		goto err_out_exit;

	new = dst_state_alloc(st->node);
	if (!new) {
		err = -ENOMEM;
		goto err_out_release;
	}
	new->socket = sock;

	new->ctl.addr.sa_data_len = sizeof(struct sockaddr);
	err = kernel_getpeername(sock, (struct sockaddr *)&new->ctl.addr,
			(int *)&new->ctl.addr.sa_data_len);
	if (err)
		goto err_out_put;

	new->permissions = dst_check_permissions(st, new);
	if (new->permissions == 0) {
		err = -EPERM;
		dst_dump_addr(sock, (struct sockaddr *)&new->ctl.addr,
				"Client is not allowed to connect");
		goto err_out_put;
	}

	err = dst_poll_init(new);
	if (err)
		goto err_out_put;

	dst_dump_addr(sock, (struct sockaddr *)&new->ctl.addr,
			"Connected client");

	return new;

err_out_put:
	dst_state_put(new);
err_out_release:
	sock_release(sock);
err_out_exit:
	return ERR_PTR(err);
}

/*
 * Each server's block request sometime finishes.
 * Usually it happens in hard irq context of the appropriate controller,
 * so to play good with all cases we just queue BIO into the queue
 * and wake up processing thread, which gets completed request and
 * send (encrypting if needed) it back to the client (if it was a read
 * request), or sends back reply that writing succesfully completed.
 */
static int dst_export_process_request_queue(struct dst_state *st)
{
	unsigned long flags;
	struct dst_export_priv *p = NULL;
	struct bio *bio;
	int err = 0;

	while (!list_empty(&st->request_list)) {
		spin_lock_irqsave(&st->request_lock, flags);
		if (!list_empty(&st->request_list)) {
			p = list_first_entry(&st->request_list,
				struct dst_export_priv, request_entry);
			list_del(&p->request_entry);
		}
		spin_unlock_irqrestore(&st->request_lock, flags);

		if (!p)
			break;

		bio = p->bio;

		if (dst_need_crypto(st->node) && (bio_data_dir(bio) == READ))
			err = dst_export_crypto(st->node, bio);
		else
			err = dst_export_send_bio(bio);

		if (err)
			break;
	}

	return err;
}

/*
 * Cleanup export state.
 * It has to wait until all requests are finished,
 * and then free them all.
 */
static void dst_state_cleanup_export(struct dst_state *st)
{
	struct dst_export_priv *p;
	unsigned long flags;

	/*
	 * This loop waits for all pending bios to be completed and freed.
	 */
	while (atomic_read(&st->refcnt) > 1) {
		dprintk("%s: st: %p, refcnt: %d, list_empty: %d.\n",
				__func__, st, atomic_read(&st->refcnt),
				list_empty(&st->request_list));
		wait_event_timeout(st->thread_wait,
				(atomic_read(&st->refcnt) == 1) ||
				!list_empty(&st->request_list),
				HZ/2);

		while (!list_empty(&st->request_list)) {
			p = NULL;
			spin_lock_irqsave(&st->request_lock, flags);
			if (!list_empty(&st->request_list)) {
				p = list_first_entry(&st->request_list,
					struct dst_export_priv, request_entry);
				list_del(&p->request_entry);
			}
			spin_unlock_irqrestore(&st->request_lock, flags);

			if (p)
				bio_put(p->bio);

			dprintk("%s: st: %p, refcnt: %d, list_empty: %d, p: %p.\n",
				__func__, st, atomic_read(&st->refcnt),
				list_empty(&st->request_list), p);
		}
	}

	dst_state_put(st);
}

/*
 * Client accepting thread.
 * Not only accepts new connection, but also schedules receiving thread
 * and performs request completion described above.
 */
static int dst_accept(void *init_data, void *schedule_data)
{
	struct dst_state *main_st = schedule_data;
	struct dst_node *n = init_data;
	struct dst_state *st;
	int err;

	while (n->trans_scan_timeout && !main_st->need_exit) {
		dprintk("%s: main_st: %p, n: %p.\n", __func__, main_st, n);
		st = dst_accept_client(main_st);
		if (IS_ERR(st))
			continue;

		err = dst_state_schedule_receiver(st);
		if (!err) {
			while (n->trans_scan_timeout) {
				err = wait_event_interruptible_timeout(st->thread_wait,
						!list_empty(&st->request_list) ||
						!n->trans_scan_timeout ||
						st->need_exit,
					HZ);

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

				if (list_empty(&st->request_list))
					continue;

				err = dst_export_process_request_queue(st);
				if (err)
					break;
			}

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

		dst_state_cleanup_export(st);
	}

	dprintk("%s: freeing listening socket st: %p.\n", __func__, main_st);

	dst_state_lock(main_st);
	dst_poll_exit(main_st);
	dst_state_socket_release(main_st);
	dst_state_unlock(main_st);
	dst_state_put(main_st);
	dprintk("%s: freed listening socket st: %p.\n", __func__, main_st);

	return 0;
}

int dst_start_export(struct dst_node *n)
{
	if (list_empty(&n->security_list)) {
		printk(KERN_ERR "You are trying to export node '%s' without security attributes.\n"
				"No clients will be allowed to connect. Exiting.\n", n->name);
		return -EINVAL;
	}
	return dst_node_trans_init(n, sizeof(struct dst_export_priv));
}

/*
 * Initialize listening state and schedule accepting thread.
 */
int dst_node_init_listened(struct dst_node *n, struct dst_export_ctl *le)
{
	struct dst_state *st;
	int err = -ENOMEM;
	struct dst_network_ctl *ctl = &le->ctl;

	memcpy(&n->info->net, ctl, sizeof(struct dst_network_ctl));

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

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

	st->socket->sk->sk_reuse = 1;

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

	err = kernel_listen(st->socket, 1024);
	if (err)
		goto err_out_socket_release;
	n->state = st;

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

	dst_state_get(st);

	err = thread_pool_schedule(n->pool, dst_thread_setup,
			dst_accept, st, MAX_SCHEDULE_TIMEOUT);
	if (err)
		goto err_out_poll_exit;

	return 0;

err_out_poll_exit:
	dst_poll_exit(st);
err_out_socket_release:
	dst_state_socket_release(st);
err_out_put:
	dst_state_put(st);
err_out_exit:
	n->state = NULL;
	return err;
}

/*
 * Free bio and related private data.
 * Also drop a reference counter for appropriate state,
 * which waits when there are no more block IOs in-flight.
 */
static void dst_bio_destructor(struct bio *bio)
{
	struct bio_vec *bv;
	struct dst_export_priv *priv = bio->bi_private;
	int i;

	bio_for_each_segment(bv, bio, i) {
		if (!bv->bv_page)
			break;

		__free_page(bv->bv_page);
	}

	if (priv)
		dst_state_put(priv->state);
	bio_free(bio, dst_bio_set);
}

/*
 * Block IO completion. Queue request to be sent back to
 * the client (or just confirmation).
 */
static void dst_bio_end_io(struct bio *bio, int err)
{
	struct dst_export_priv *p = bio->bi_private;
	struct dst_state *st = p->state;
	unsigned long flags;

	spin_lock_irqsave(&st->request_lock, flags);
	list_add_tail(&p->request_entry, &st->request_list);
	spin_unlock_irqrestore(&st->request_lock, flags);

	wake_up(&st->thread_wait);
}

/*
 * Allocate read request for the server.
 */
static int dst_export_read_request(struct bio *bio, unsigned int total_size)
{
	unsigned int size;
	struct page *page;
	int err;

	while (total_size) {
		err = -ENOMEM;
		page = alloc_page(GFP_KERNEL);
		if (!page)
			goto err_out_exit;

		size = min_t(unsigned int, PAGE_SIZE, total_size);

		err = bio_add_page(bio, page, size, 0);
		dprintk("%s: bio: %llu/%u, size: %u, err: %d.\n",
				__func__, (u64)bio->bi_sector, bio->bi_size,
				size, err);
		if (err <= 0)
			goto err_out_free_page;

		total_size -= size;
	}

	return 0;

err_out_free_page:
	__free_page(page);
err_out_exit:
	return err;
}

/*
 * Allocate write request for the server.
 * Should not only get pages, but also read data from the network.
 */
static int dst_export_write_request(struct dst_state *st,
		struct bio *bio, unsigned int total_size)
{
	unsigned int size;
	struct page *page;
	void *data;
	int err;

	while (total_size) {
		err = -ENOMEM;
		page = alloc_page(GFP_KERNEL);
		if (!page)
			goto err_out_exit;

		data = kmap(page);
		if (!data)
			goto err_out_free_page;

		size = min_t(unsigned int, PAGE_SIZE, total_size);

		err = dst_data_recv(st, data, size);
		if (err)
			goto err_out_unmap_page;

		err = bio_add_page(bio, page, size, 0);
		if (err <= 0)
			goto err_out_unmap_page;

		kunmap(page);

		total_size -= size;
	}

	return 0;

err_out_unmap_page:
	kunmap(page);
err_out_free_page:
	__free_page(page);
err_out_exit:
	return err;
}

/*
 * Groovy, we've gotten an IO request from the client.
 * Allocate BIO from the bioset, private data from the mempool
 * and lots of pages for IO.
 */
int dst_process_io(struct dst_state *st)
{
	struct dst_node *n = st->node;
	struct dst_cmd *cmd = st->data;
	struct bio *bio;
	struct dst_export_priv *priv;
	int err = -ENOMEM;

	if (unlikely(!n->bdev)) {
		err = -EINVAL;
		goto err_out_exit;
	}

	bio = bio_alloc_bioset(GFP_KERNEL,
			PAGE_ALIGN(cmd->size) >> PAGE_SHIFT,
			dst_bio_set);
	if (!bio)
		goto err_out_exit;

	priv = (struct dst_export_priv *)(((void *)bio) - sizeof (struct dst_export_priv));

	priv->state = dst_state_get(st);
	priv->bio = bio;

	bio->bi_private = priv;
	bio->bi_end_io = dst_bio_end_io;
	bio->bi_destructor = dst_bio_destructor;
	bio->bi_bdev = n->bdev;

	/*
	 * Server side is only interested in two low bits:
	 * uptodate (set by itself actually) and rw block
	 */
	bio->bi_flags |= cmd->flags & 3;

	bio->bi_rw = cmd->rw;
	bio->bi_size = 0;
	bio->bi_sector = cmd->sector;

	dst_bio_to_cmd(bio, &priv->cmd, DST_IO_RESPONSE, cmd->id);

	priv->cmd.flags = 0;
	priv->cmd.size = cmd->size;

	if (bio_data_dir(bio) == WRITE) {
		err = dst_recv_cdata(st, priv->cmd.hash);
		if (err)
			goto err_out_free;

		err = dst_export_write_request(st, bio, cmd->size);
		if (err)
			goto err_out_free;

		if (dst_need_crypto(n))
			return dst_export_crypto(n, bio);
	} else {
		err = dst_export_read_request(bio, cmd->size);
		if (err)
			goto err_out_free;
	}

	dprintk("%s: bio: %llu/%u, rw: %lu, dir: %lu, flags: %lx, phys: %d.\n",
			__func__, (u64)bio->bi_sector, bio->bi_size,
			bio->bi_rw, bio_data_dir(bio),
			bio->bi_flags, bio->bi_phys_segments);

	generic_make_request(bio);

	return 0;

err_out_free:
	bio_put(bio);
err_out_exit:
	return err;
}

/*
 * Ok, block IO is ready, let's send it back to the client...
 */
int dst_export_send_bio(struct bio *bio)
{
	struct dst_export_priv *p = bio->bi_private;
	struct dst_state *st = p->state;
	struct dst_cmd *cmd = &p->cmd;
	int err;

	dprintk("%s: id: %llu, bio: %llu/%u, csize: %u, flags: %lu, rw: %lu.\n",
			__func__, cmd->id, (u64)bio->bi_sector, bio->bi_size,
			cmd->csize, bio->bi_flags, bio->bi_rw);

	dst_convert_cmd(cmd);

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

	if (bio_data_dir(bio) == WRITE) {
		/* ... or just confirmation that writing has completed. */
		cmd->size = cmd->csize = 0;
		err = dst_data_send_header(st->socket, cmd,
				sizeof(struct dst_cmd), 0);
		if (err)
			goto err_out_unlock;
	} else {
		err = dst_send_bio(st, cmd, bio);
		if (err)
			goto err_out_unlock;
	}

	dst_state_unlock(st);

	bio_put(bio);
	return 0;

err_out_unlock:
	dst_state_unlock(st);

	bio_put(bio);
	return err;
}