/* 
   Unix SMB/CIFS implementation.
   Samba internal messaging functions
   Copyright (C) 2007 by Volker Lendecke

   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "lib/messages_ctdbd.h"
#include "lib/util/server_id.h"
#include "messages.h"
#include "util_tdb.h"
#include "lib/util/iov_buf.h"
#include "lib/messages_util.h"
#include "ctdbd_conn.h"
#include "lib/cluster_support.h"

struct messaging_ctdbd_context;

struct messaging_ctdbd_fde_ev {
	struct messaging_ctdbd_fde_ev *prev, *next;

	/*
	 * Backreference to enable DLIST_REMOVE from our
	 * destructor. Also, set to NULL when the dgm_context dies
	 * before the messaging_dgm_fde_ev.
	 */
	struct messaging_ctdbd_context *ctx;

	struct tevent_context *ev;
	struct tevent_fd *fde;
};

struct messaging_ctdbd_context {
	struct ctdbd_connection *conn;

	struct messaging_ctdbd_fde_ev *fde_evs;

	void (*recv_cb)(struct tevent_context *ev,
			const uint8_t *msg, size_t msg_len,
			int *fds, size_t num_fds,
			void *private_data);
	void *private_data;
};

/*
 * This is a Samba3 hack/optimization. Routines like process_exists need to
 * talk to ctdbd, and they don't get handed a messaging context.
 */
static struct ctdbd_connection *global_ctdbd_connection;
static int global_ctdb_connection_pid;

struct ctdbd_connection *messaging_ctdbd_connection(void)
{
	if (!lp_clustering()) {
		return NULL;
	}

	if (global_ctdb_connection_pid == 0 &&
	    global_ctdbd_connection == NULL) {
		struct tevent_context *ev;
		struct messaging_context *msg;

		ev = samba_tevent_context_init(NULL);
		if (!ev) {
			DEBUG(0,("samba_tevent_context_init failed\n"));
			return NULL;
		}

		msg = messaging_init(NULL, ev);
		if (!msg) {
			DEBUG(0,("messaging_init failed\n"));
			return NULL;
		}
	}

	if (global_ctdb_connection_pid != getpid()) {
		DEBUG(0,("messaging_ctdbd_connection():"
			 "valid for pid[%jd] but it's [%jd]\n",
			 (intmax_t)global_ctdb_connection_pid,
			 (intmax_t)getpid()));
		smb_panic("messaging_ctdbd_connection() invalid process\n");
	}

	return global_ctdbd_connection;
}

static int messaging_ctdb_send(struct server_id src,
			       struct server_id pid, int msg_type,
			       const struct iovec *iov, int iovlen,
			       const int *fds, size_t num_fds,
			       struct messaging_backend *backend)
{
	struct messaging_ctdbd_context *ctx = talloc_get_type_abort(
		backend->private_data, struct messaging_ctdbd_context);
	uint8_t hdr[MESSAGE_HDR_LENGTH];
	struct iovec iov2[iovlen+1];

	if (num_fds > 0) {
		return ENOSYS;
	}

	message_hdr_put(hdr, msg_type, src, pid);
	iov2[0] = (struct iovec){ .iov_base = hdr, .iov_len = sizeof(hdr) };
	memcpy(&iov2[1], iov, iovlen * sizeof(*iov));

	return ctdbd_messaging_send_iov(ctx->conn, pid.vnn, pid.pid,
					iov2, iovlen+1);
}

static int messaging_ctdbd_destructor(struct messaging_ctdbd_context *ctx)
{
	/*
	 * The global connection just went away
	 */
	global_ctdb_connection_pid = 0;
	global_ctdbd_connection = NULL;
	return 0;
}

static int messaging_ctdb_recv(
	struct tevent_context *ev,
	uint32_t src_vnn, uint32_t dst_vnn, uint64_t dst_srvid,
	const uint8_t *msg, size_t msg_len, void *private_data)
{
	struct messaging_ctdbd_context *ctx = talloc_get_type_abort(
		private_data, struct messaging_ctdbd_context);

	ctx->recv_cb(ev, msg, msg_len, NULL, 0, ctx->private_data);

	return 0;
}

static void messaging_ctdbd_readable(struct tevent_context *ev,
				     struct tevent_fd *fde,
				     uint16_t flags,
				     void *private_data)
{
	struct ctdbd_connection *conn = talloc_get_type_abort(
		private_data, struct ctdbd_connection);

	if ((flags & TEVENT_FD_READ) == 0) {
		return;
	}
	ctdbd_socket_readable(ev, conn);
}

static int messaging_ctdbd_init_internal(
	struct messaging_context *msg_ctx, TALLOC_CTX *mem_ctx,
	struct messaging_ctdbd_context *ctx,
	void (*recv_cb)(struct tevent_context *ev,
			const uint8_t *msg, size_t msg_len,
			int *fds, size_t num_fds,
			void *private_data),
	void *private_data,
	bool reinit)
{
	int ret;

	if (reinit) {
		ret = ctdbd_reinit_connection(ctx,
					      lp_ctdbd_socket(),
					      lp_ctdb_timeout(),
					      ctx->conn);
		if (ret != 0) {
			DBG_ERR("ctdbd_reinit_connection failed: %s\n",
				strerror(ret));
			return ret;
		}
	} else {
		ret = ctdbd_init_connection(ctx,
					    lp_ctdbd_socket(),
					    lp_ctdb_timeout(),
					    &ctx->conn);
		if (ret != 0) {
			DBG_ERR("ctdbd_init_connection failed: %s\n",
				strerror(ret));
			return ret;
		}
	}

	ret = register_with_ctdbd(ctx->conn, MSG_SRVID_SAMBA, NULL, NULL);
	if (ret != 0) {
		DBG_DEBUG("Could not register MSG_SRVID_SAMBA: %s\n",
			  strerror(ret));
		return ret;
	}

	ctx->recv_cb = recv_cb;
	ctx->private_data = private_data;

	ret = register_with_ctdbd(ctx->conn, getpid(),
				  messaging_ctdb_recv, ctx);
	if (ret != 0) {
		DEBUG(10, ("register_with_ctdbd failed: %s\n",
			   strerror(ret)));
		return ret;
	}

	global_ctdb_connection_pid = getpid();
	global_ctdbd_connection = ctx->conn;
	talloc_set_destructor(ctx, messaging_ctdbd_destructor);

	set_my_vnn(ctdbd_vnn(ctx->conn));

	return 0;
}

int messaging_ctdbd_init(struct messaging_context *msg_ctx,
			 TALLOC_CTX *mem_ctx,
			 void (*recv_cb)(struct tevent_context *ev,
					 const uint8_t *msg, size_t msg_len,
					 int *fds, size_t num_fds,
					 void *private_data),
			 void *private_data,
			 struct messaging_backend **presult)
{
	struct messaging_backend *result;
	struct messaging_ctdbd_context *ctx;
	int ret;

	if (!(result = talloc(mem_ctx, struct messaging_backend))) {
		DEBUG(0, ("talloc failed\n"));
		return ENOMEM;
	}

	if (!(ctx = talloc_zero(result, struct messaging_ctdbd_context))) {
		DEBUG(0, ("talloc failed\n"));
		TALLOC_FREE(result);
		return ENOMEM;
	}

	ret = messaging_ctdbd_init_internal(msg_ctx, mem_ctx, ctx,
					    recv_cb, private_data, false);
	if (ret != 0) {
		TALLOC_FREE(result);
		return ret;
	}

	result->send_fn = messaging_ctdb_send;
	result->private_data = (void *)ctx;

	*presult = result;
	return 0;
}

int messaging_ctdbd_reinit(struct messaging_context *msg_ctx,
			   TALLOC_CTX *mem_ctx,
			   void (*recv_cb)(struct tevent_context *ev,
					   const uint8_t *msg, size_t msg_len,
					   int *fds, size_t num_fds,
					   void *private_data),
			   void *private_data,
			   struct messaging_backend *backend)
{
	struct messaging_ctdbd_context *ctx = talloc_get_type_abort(
		backend->private_data, struct messaging_ctdbd_context);
	int ret;

	ret = messaging_ctdbd_init_internal(msg_ctx, mem_ctx, ctx,
					    recv_cb, private_data, true);
	if (ret != 0) {
		return ret;
	}

	return 0;
}

struct messaging_ctdbd_fde {
	struct tevent_fd *fde;
};

static int messaging_ctdbd_fde_ev_destructor(
	struct messaging_ctdbd_fde_ev *fde_ev)
{
	if (fde_ev->ctx != NULL) {
		DLIST_REMOVE(fde_ev->ctx->fde_evs, fde_ev);
		fde_ev->ctx = NULL;
	}
	return 0;
}

struct messaging_ctdbd_fde *messaging_ctdbd_register_tevent_context(
	TALLOC_CTX *mem_ctx, struct tevent_context *ev,
	struct messaging_backend *backend)
{
	struct messaging_ctdbd_context *ctx = talloc_get_type_abort(
		backend->private_data, struct messaging_ctdbd_context);
	struct messaging_ctdbd_fde_ev *fde_ev;
	struct messaging_ctdbd_fde *fde;

	if (ctx == NULL) {
		return NULL;
	}

	fde = talloc(mem_ctx, struct messaging_ctdbd_fde);
	if (fde == NULL) {
		return NULL;
	}

	for (fde_ev = ctx->fde_evs; fde_ev != NULL; fde_ev = fde_ev->next) {
		if ((fde_ev->ev == ev) &&
		    (tevent_fd_get_flags(fde_ev->fde) != 0)) {
			break;
		}
	}

	if (fde_ev == NULL) {
		int fd = ctdbd_conn_get_fd(ctx->conn);

		fde_ev = talloc(fde, struct messaging_ctdbd_fde_ev);
		if (fde_ev == NULL) {
			return NULL;
		}
		fde_ev->fde = tevent_add_fd(
			ev, fde_ev, fd, TEVENT_FD_READ,
			messaging_ctdbd_readable, ctx->conn);
		if (fde_ev->fde == NULL) {
			TALLOC_FREE(fde);
			return NULL;
		}
		fde_ev->ev = ev;
		fde_ev->ctx = ctx;
		DLIST_ADD(ctx->fde_evs, fde_ev);
		talloc_set_destructor(
			fde_ev, messaging_ctdbd_fde_ev_destructor);
	} else {
		/*
		 * Same trick as with tdb_wrap: The caller will never
		 * see the talloc_referenced object, the
		 * messaging_ctdbd_fde_ev, so problems with
		 * talloc_unlink will not happen.
		 */
		if (talloc_reference(fde, fde_ev) == NULL) {
			TALLOC_FREE(fde);
			return NULL;
		}
	}

	fde->fde = fde_ev->fde;
	return fde;
}