/*
   Unix SMB/CIFS implementation.
   async socket syscalls
   Copyright (C) Volker Lendecke 2008

     ** NOTE! The following LGPL license applies to the async_sock
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/network.h"
#include "system/filesys.h"
#include <talloc.h>
#include <tevent.h>
#include "lib/async_req/async_sock.h"
#include "lib/util/iov_buf.h"
#include "lib/util/util_net.h"

/* Note: lib/util/ is currently GPL */
#include "lib/util/tevent_unix.h"
#include "lib/util/samba_util.h"

struct async_connect_state {
	int fd;
	struct tevent_fd *fde;
	int result;
	long old_sockflags;
	socklen_t address_len;
	struct sockaddr_storage address;

	void (*before_connect)(void *private_data);
	void (*after_connect)(void *private_data);
	void *private_data;
};

static void async_connect_cleanup(struct tevent_req *req,
				  enum tevent_req_state req_state);
static void async_connect_connected(struct tevent_context *ev,
				    struct tevent_fd *fde, uint16_t flags,
				    void *priv);

/**
 * @brief async version of connect(2)
 * @param[in] mem_ctx	The memory context to hang the result off
 * @param[in] ev	The event context to work from
 * @param[in] fd	The socket to recv from
 * @param[in] address	Where to connect?
 * @param[in] address_len Length of *address
 * @retval The async request
 *
 * This function sets the socket into non-blocking state to be able to call
 * connect in an async state. This will be reset when the request is finished.
 */

struct tevent_req *async_connect_send(
	TALLOC_CTX *mem_ctx, struct tevent_context *ev, int fd,
	const struct sockaddr *address, socklen_t address_len,
	void (*before_connect)(void *private_data),
	void (*after_connect)(void *private_data),
	void *private_data)
{
	struct tevent_req *req;
	struct async_connect_state *state;
	int ret;

	req = tevent_req_create(mem_ctx, &state, struct async_connect_state);
	if (req == NULL) {
		return NULL;
	}

	/**
	 * We have to set the socket to nonblocking for async connect(2). Keep
	 * the old sockflags around.
	 */

	state->fd = fd;
	state->before_connect = before_connect;
	state->after_connect = after_connect;
	state->private_data = private_data;

	state->old_sockflags = fcntl(fd, F_GETFL, 0);
	if (state->old_sockflags == -1) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	tevent_req_set_cleanup_fn(req, async_connect_cleanup);

	state->address_len = address_len;
	if (address_len > sizeof(state->address)) {
		tevent_req_error(req, EINVAL);
		return tevent_req_post(req, ev);
	}
	memcpy(&state->address, address, address_len);

	ret = set_blocking(fd, false);
	if (ret == -1) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	if (state->before_connect != NULL) {
		state->before_connect(state->private_data);
	}

	state->result = connect(fd, address, address_len);

	if (state->after_connect != NULL) {
		state->after_connect(state->private_data);
	}

	if (state->result == 0) {
		tevent_req_done(req);
		return tevent_req_post(req, ev);
	}

	/*
	 * The only errno indicating that an initial connect is still
	 * in flight is EINPROGRESS.
	 *
	 * This allows callers like open_socket_out_send() to reuse
	 * fds and call us with an fd for which the connect is still
	 * in flight. The proper thing to do for callers would be
	 * closing the fd and starting from scratch with a fresh
	 * socket.
	 */

	if (errno != EINPROGRESS) {
		tevent_req_error(req, errno);
		return tevent_req_post(req, ev);
	}

	/*
	 * Note for historic reasons TEVENT_FD_WRITE is not enough
	 * to get notified for POLLERR or EPOLLHUP even if they
	 * come together with POLLOUT. That means we need to
	 * use TEVENT_FD_READ in addition until we have
	 * TEVENT_FD_ERROR.
	 */
	state->fde = tevent_add_fd(ev, state, fd,
				   TEVENT_FD_ERROR|TEVENT_FD_WRITE,
				   async_connect_connected, req);
	if (state->fde == NULL) {
		tevent_req_error(req, ENOMEM);
		return tevent_req_post(req, ev);
	}
	return req;
}

static void async_connect_cleanup(struct tevent_req *req,
				  enum tevent_req_state req_state)
{
	struct async_connect_state *state =
		tevent_req_data(req, struct async_connect_state);

	TALLOC_FREE(state->fde);
	if (state->fd != -1) {
		int ret;

		ret = fcntl(state->fd, F_SETFL, state->old_sockflags);
		if (ret == -1) {
			abort();
		}

		state->fd = -1;
	}
}

/**
 * fde event handler for connect(2)
 * @param[in] ev	The event context that sent us here
 * @param[in] fde	The file descriptor event associated with the connect
 * @param[in] flags	Indicate read/writeability of the socket
 * @param[in] priv	private data, "struct async_req *" in this case
 */

static void async_connect_connected(struct tevent_context *ev,
				    struct tevent_fd *fde, uint16_t flags,
				    void *priv)
{
	struct tevent_req *req = talloc_get_type_abort(
		priv, struct tevent_req);
	struct async_connect_state *state =
		tevent_req_data(req, struct async_connect_state);
	int ret;
	int socket_error = 0;
	socklen_t slen = sizeof(socket_error);

	ret = getsockopt(state->fd, SOL_SOCKET, SO_ERROR,
			 &socket_error, &slen);

	if (ret != 0) {
		/*
		 * According to Stevens this is the Solaris behaviour
		 * in case the connection encountered an error:
		 * getsockopt() fails, error is in errno
		 */
		tevent_req_error(req, errno);
		return;
	}

	if (socket_error != 0) {
		/*
		 * Berkeley derived implementations (including) Linux
		 * return the pending error via socket_error.
		 */
		tevent_req_error(req, socket_error);
		return;
	}

	tevent_req_done(req);
	return;
}

int async_connect_recv(struct tevent_req *req, int *perrno)
{
	int err = tevent_req_simple_recv_unix(req);

	if (err != 0) {
		*perrno = err;
		return -1;
	}

	return 0;
}

struct writev_state {
	struct tevent_context *ev;
	struct tevent_queue_entry *queue_entry;
	int fd;
	struct tevent_fd *fde;
	struct iovec *iov;
	int count;
	size_t total_size;
	uint16_t flags;
	bool err_on_readability;
};

static void writev_cleanup(struct tevent_req *req,
			   enum tevent_req_state req_state);
static bool writev_cancel(struct tevent_req *req);
static void writev_trigger(struct tevent_req *req, void *private_data);
static void writev_handler(struct tevent_context *ev, struct tevent_fd *fde,
			   uint16_t flags, void *private_data);

struct tevent_req *writev_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
			       struct tevent_queue *queue, int fd,
			       bool err_on_readability,
			       struct iovec *iov, int count)
{
	struct tevent_req *req;
	struct writev_state *state;

	req = tevent_req_create(mem_ctx, &state, struct writev_state);
	if (req == NULL) {
		return NULL;
	}
	state->ev = ev;
	state->fd = fd;
	state->total_size = 0;
	state->count = count;
	state->iov = (struct iovec *)talloc_memdup(
		state, iov, sizeof(struct iovec) * count);
	if (tevent_req_nomem(state->iov, req)) {
		return tevent_req_post(req, ev);
	}
	state->flags = TEVENT_FD_WRITE | TEVENT_FD_ERROR;
	if (err_on_readability) {
		state->flags |= TEVENT_FD_READ;
	}

	tevent_req_set_cleanup_fn(req, writev_cleanup);
	tevent_req_set_cancel_fn(req, writev_cancel);

	if (queue == NULL) {
		state->fde = tevent_add_fd(state->ev, state, state->fd,
				    state->flags, writev_handler, req);
		if (tevent_req_nomem(state->fde, req)) {
			return tevent_req_post(req, ev);
		}
		return req;
	}

	/*
	 * writev_trigger tries a nonblocking write. If that succeeds,
	 * we can't directly notify the callback to call
	 * writev_recv. The callback would TALLOC_FREE(req) after
	 * calling writev_recv even before writev_trigger can inspect
	 * it for success.
	 */
	tevent_req_defer_callback(req, ev);

	state->queue_entry = tevent_queue_add_optimize_empty(
		queue, ev, req, writev_trigger, NULL);
	if (tevent_req_nomem(state->queue_entry, req)) {
		return tevent_req_post(req, ev);
	}
	if (!tevent_req_is_in_progress(req)) {
		return tevent_req_post(req, ev);
	}
	return req;
}

static void writev_cleanup(struct tevent_req *req,
			   enum tevent_req_state req_state)
{
	struct writev_state *state = tevent_req_data(req, struct writev_state);

	TALLOC_FREE(state->queue_entry);
	TALLOC_FREE(state->fde);
}

static bool writev_cancel(struct tevent_req *req)
{
	struct writev_state *state = tevent_req_data(req, struct writev_state);

	if (state->total_size > 0) {
		/*
		 * We've already started to write :-(
		 */
		return false;
	}

	TALLOC_FREE(state->queue_entry);
	TALLOC_FREE(state->fde);

	tevent_req_defer_callback(req, state->ev);
	tevent_req_error(req, ECANCELED);
	return true;
}

static void writev_do(struct tevent_req *req, struct writev_state *state)
{
	ssize_t written;
	bool ok;

	written = writev(state->fd, state->iov, state->count);
	if ((written == -1) &&
	    ((errno == EINTR) ||
	     (errno == EAGAIN) ||
	     (errno == EWOULDBLOCK))) {
		/* retry after going through the tevent loop */
		return;
	}
	if (written == -1) {
		tevent_req_error(req, errno);
		return;
	}
	if (written == 0) {
		tevent_req_error(req, EPIPE);
		return;
	}
	state->total_size += written;

	ok = iov_advance(&state->iov, &state->count, written);
	if (!ok) {
		tevent_req_error(req, EIO);
		return;
	}

	if (state->count == 0) {
		tevent_req_done(req);
		return;
	}
}

static void writev_trigger(struct tevent_req *req, void *private_data)
{
	struct writev_state *state = tevent_req_data(req, struct writev_state);

	state->queue_entry = NULL;

	writev_do(req, state);
	if (!tevent_req_is_in_progress(req)) {
		return;
	}

	state->fde = tevent_add_fd(state->ev, state, state->fd, state->flags,
			    writev_handler, req);
	if (tevent_req_nomem(state->fde, req)) {
		return;
	}
}

static void writev_handler(struct tevent_context *ev, struct tevent_fd *fde,
			   uint16_t flags, void *private_data)
{
	struct tevent_req *req = talloc_get_type_abort(
		private_data, struct tevent_req);
	struct writev_state *state =
		tevent_req_data(req, struct writev_state);

	if (flags & TEVENT_FD_ERROR) {
		/*
		 * There's an error, for legacy reasons
		 * we just use EPIPE instead of a more
		 * detailed error using
		 * samba_socket_poll_or_sock_error().
		 */
		tevent_req_error(req, EPIPE);
		return;
	}

	if (flags & TEVENT_FD_READ) {
		/* Readable and the caller wants an error on read. */
		tevent_req_error(req, EPIPE);
		return;
	}

	writev_do(req, state);
}

ssize_t writev_recv(struct tevent_req *req, int *perrno)
{
	struct writev_state *state =
		tevent_req_data(req, struct writev_state);
	ssize_t ret;

	if (tevent_req_is_unix_error(req, perrno)) {
		tevent_req_received(req);
		return -1;
	}
	ret = state->total_size;
	tevent_req_received(req);
	return ret;
}

struct read_packet_state {
	int fd;
	struct tevent_fd *fde;
	uint8_t *buf;
	size_t nread;
	ssize_t (*more)(uint8_t *buf, size_t buflen, void *private_data);
	void *private_data;
};

static void read_packet_cleanup(struct tevent_req *req,
				 enum tevent_req_state req_state);
static void read_packet_handler(struct tevent_context *ev,
				struct tevent_fd *fde,
				uint16_t flags, void *private_data);

struct tevent_req *read_packet_send(TALLOC_CTX *mem_ctx,
				    struct tevent_context *ev,
				    int fd, size_t initial,
				    ssize_t (*more)(uint8_t *buf,
						    size_t buflen,
						    void *private_data),
				    void *private_data)
{
	struct tevent_req *req;
	struct read_packet_state *state;

	req = tevent_req_create(mem_ctx, &state, struct read_packet_state);
	if (req == NULL) {
		return NULL;
	}
	state->fd = fd;
	state->nread = 0;
	state->more = more;
	state->private_data = private_data;

	tevent_req_set_cleanup_fn(req, read_packet_cleanup);

	state->buf = talloc_array(state, uint8_t, initial);
	if (tevent_req_nomem(state->buf, req)) {
		return tevent_req_post(req, ev);
	}

	state->fde = tevent_add_fd(ev, state, fd,
				   TEVENT_FD_READ, read_packet_handler,
				   req);
	if (tevent_req_nomem(state->fde, req)) {
		return tevent_req_post(req, ev);
	}
	return req;
}

static void read_packet_cleanup(struct tevent_req *req,
			   enum tevent_req_state req_state)
{
	struct read_packet_state *state =
		tevent_req_data(req, struct read_packet_state);

	TALLOC_FREE(state->fde);
}

static void read_packet_handler(struct tevent_context *ev,
				struct tevent_fd *fde,
				uint16_t flags, void *private_data)
{
	struct tevent_req *req = talloc_get_type_abort(
		private_data, struct tevent_req);
	struct read_packet_state *state =
		tevent_req_data(req, struct read_packet_state);
	size_t total = talloc_get_size(state->buf);
	ssize_t nread, more;
	uint8_t *tmp;

	nread = recv(state->fd, state->buf+state->nread, total-state->nread,
		     0);
	if ((nread == -1) && (errno == ENOTSOCK)) {
		nread = read(state->fd, state->buf+state->nread,
			     total-state->nread);
	}
	if ((nread == -1) && (errno == EINTR)) {
		/* retry */
		return;
	}
	if (nread == -1) {
		tevent_req_error(req, errno);
		return;
	}
	if (nread == 0) {
		tevent_req_error(req, EPIPE);
		return;
	}

	state->nread += nread;
	if (state->nread < total) {
		/* Come back later */
		return;
	}

	/*
	 * We got what was initially requested. See if "more" asks for -- more.
	 */
	if (state->more == NULL) {
		/* Nobody to ask, this is a async read_data */
		tevent_req_done(req);
		return;
	}

	more = state->more(state->buf, total, state->private_data);
	if (more == -1) {
		/* We got an invalid packet, tell the caller */
		tevent_req_error(req, EIO);
		return;
	}
	if (more == 0) {
		/* We're done, full packet received */
		tevent_req_done(req);
		return;
	}

	if (total + more < total) {
		tevent_req_error(req, EMSGSIZE);
		return;
	}

	tmp = talloc_realloc(state, state->buf, uint8_t, total+more);
	if (tevent_req_nomem(tmp, req)) {
		return;
	}
	state->buf = tmp;
}

ssize_t read_packet_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
			 uint8_t **pbuf, int *perrno)
{
	struct read_packet_state *state =
		tevent_req_data(req, struct read_packet_state);

	if (tevent_req_is_unix_error(req, perrno)) {
		tevent_req_received(req);
		return -1;
	}
	*pbuf = talloc_move(mem_ctx, &state->buf);
	tevent_req_received(req);
	return talloc_get_size(*pbuf);
}

struct wait_for_read_state {
	struct tevent_fd *fde;
	int fd;
	bool check_errors;
};

static void wait_for_read_cleanup(struct tevent_req *req,
				  enum tevent_req_state req_state);
static void wait_for_read_done(struct tevent_context *ev,
			       struct tevent_fd *fde,
			       uint16_t flags,
			       void *private_data);

struct tevent_req *wait_for_read_send(TALLOC_CTX *mem_ctx,
				      struct tevent_context *ev, int fd,
				      bool check_errors)
{
	struct tevent_req *req;
	struct wait_for_read_state *state;

	req = tevent_req_create(mem_ctx, &state, struct wait_for_read_state);
	if (req == NULL) {
		return NULL;
	}

	tevent_req_set_cleanup_fn(req, wait_for_read_cleanup);

	state->fde = tevent_add_fd(ev, state, fd, TEVENT_FD_READ,
				   wait_for_read_done, req);
	if (tevent_req_nomem(state->fde, req)) {
		return tevent_req_post(req, ev);
	}

	state->fd = fd;
	state->check_errors = check_errors;
	return req;
}

static void wait_for_read_cleanup(struct tevent_req *req,
				  enum tevent_req_state req_state)
{
	struct wait_for_read_state *state =
		tevent_req_data(req, struct wait_for_read_state);

	TALLOC_FREE(state->fde);
}

static void wait_for_read_done(struct tevent_context *ev,
			       struct tevent_fd *fde,
			       uint16_t flags,
			       void *private_data)
{
	struct tevent_req *req = talloc_get_type_abort(
		private_data, struct tevent_req);
	struct wait_for_read_state *state =
	    tevent_req_data(req, struct wait_for_read_state);
	int ret, available;

	if ((flags & TEVENT_FD_READ) == 0) {
		return;
	}

	if (!state->check_errors) {
		tevent_req_done(req);
		return;
	}

	ret = ioctl(state->fd, FIONREAD, &available);

	if ((ret == -1) && (errno == EINTR)) {
		/* come back later */
		return;
	}

	if (ret == -1) {
		tevent_req_error(req, errno);
		return;
	}

	if (available == 0) {
		tevent_req_error(req, EPIPE);
		return;
	}

	tevent_req_done(req);
}

bool wait_for_read_recv(struct tevent_req *req, int *perr)
{
	int err = tevent_req_simple_recv_unix(req);

	if (err != 0) {
		*perr = err;
		return false;
	}

	return true;
}

struct accept_state {
	struct tevent_fd *fde;
	int listen_sock;
	struct samba_sockaddr addr;
	int sock;
};

static void accept_handler(struct tevent_context *ev, struct tevent_fd *fde,
			   uint16_t flags, void *private_data);

struct tevent_req *accept_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
			       int listen_sock)
{
	struct tevent_req *req;
	struct accept_state *state;

	req = tevent_req_create(mem_ctx, &state, struct accept_state);
	if (req == NULL) {
		return NULL;
	}

	state->listen_sock = listen_sock;

	state->fde = tevent_add_fd(ev, state, listen_sock, TEVENT_FD_READ,
				   accept_handler, req);
	if (tevent_req_nomem(state->fde, req)) {
		return tevent_req_post(req, ev);
	}
	return req;
}

static void accept_handler(struct tevent_context *ev, struct tevent_fd *fde,
			   uint16_t flags, void *private_data)
{
	struct tevent_req *req = talloc_get_type_abort(
		private_data, struct tevent_req);
	struct accept_state *state = tevent_req_data(req, struct accept_state);
	int ret;

	TALLOC_FREE(state->fde);

	if ((flags & TEVENT_FD_READ) == 0) {
		tevent_req_error(req, EIO);
		return;
	}

	state->addr.sa_socklen = sizeof(state->addr.u);

	ret = accept(state->listen_sock,
		     &state->addr.u.sa,
		     &state->addr.sa_socklen);
	if ((ret == -1) && (errno == EINTR)) {
		/* retry */
		return;
	}
	if (ret == -1) {
		tevent_req_error(req, errno);
		return;
	}
	smb_set_close_on_exec(ret);
	state->sock = ret;
	tevent_req_done(req);
}

int accept_recv(struct tevent_req *req,
		int *listen_sock,
		struct samba_sockaddr *paddr,
		int *perr)
{
	struct accept_state *state = tevent_req_data(req, struct accept_state);
	int sock = state->sock;
	int err;

	if (tevent_req_is_unix_error(req, &err)) {
		if (perr != NULL) {
			*perr = err;
		}
		tevent_req_received(req);
		return -1;
	}
	if (listen_sock != NULL) {
		*listen_sock = state->listen_sock;
	}
	if (paddr != NULL) {
		*paddr = state->addr;
	}
	tevent_req_received(req);
	return sock;
}